@misc{BeyerHarendtKoschligetal.1998, author = {Beyer, Harald and Harendt, Andreas and Koschlig, Tobias and Rolle, Siegfried and Roß, Werner and Volkmann, Hans}, title = {Das Institut f{\"u}r Plasma- und Lasertechnik der Technischen Fachhochschule Wildau}, series = {Wissenschaftliche Beitr{\"a}ge 2/1998}, volume = {4}, journal = {Wissenschaftliche Beitr{\"a}ge 2/1998}, number = {2}, issn = {0949-8214}, doi = {10.15771/0949-8214_1998_2_3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-7488}, pages = {16 -- 23}, year = {1998}, abstract = {Am 31.12.1996 endete das Wissenschaftler-Integrations-Programm (WIP) in den neuen L{\"a}ndern. Es war angelegt worden, um Teilen der in der Akademie der Wissenschaften der DDR arbeitenden (und mehrfach positiv evaluierten) Wissenschaftlern eine {\"U}bergangsphase zu finanzieren, in der sie einerseits ihre Arbeit kontinuierlich fortsetzen konnten und andererseits die Integration in einer Hochschule erfolgen sollte, da die Forschungslandschaft der DDR an die bundesdeutschen Strukturen anzupassen waren. Das vorab auf zwei Jahre angelegte, 1992 gestartete Programm konnte bis 1996 verl{\"a}ngert werden, wenn es gelang, eine Hochschule zu finden, die bekundete, an einer Integration dieser Wissenschaftler in ihrer Einrichtung interessiert zu sein. Zielhochschule der Wissenschaftler in der von Prof. Dr. sc. H. G{\"u}ndel gegr{\"u}ndeten Gruppe, die sich in Fortf{\"u}hrung ihrer langj{\"a}hrigen Forschungst{\"a}tigkeit auf dem Gebiet der nichtthermischen Plasmen (auch Niedertemperaturplasmen), insbesondere zur Erzeugung von Laserlicht besch{\"a}ftigte und auch noch besch{\"a}ftigt, war die TFH Wildau. Dies war f{\"u}r eine Berliner Einrichtung einerseits ungew{\"o}hnlich, andererseits auch nahe: In der Gr{\"u}ndungsphase der TFH Wildau lag ein besonderes Schwergewicht auf den modernen Technologien, was sich auch dadurch ausdr{\"u}ckte, daß es einen Fachbereich Physikalische Technik gab, der heute im Fachbereich Ingenieur- und Wirtschaftsingenieurwesen als Studienrichtung weiter besteht. Da sich f{\"u}r die Zukunft eine immer breitere, auch ingenieurm{\"a}ßige Anwendung der Plasma- und Lasertechnik abzeichnet und an den Deutschen Fachhochschulen dieses Gebiet (insbesondere die Plasmatechnik) kaum in der Lehre vertreten wird, wurde von beiden Seiten - der TFH Wildau auf der einen und der sich damals noch als WIP AG Niedertemperaturplasmen bezeichnenden Gruppe aus Berlin auf der anderen - eine Integration in einem Institut f{\"u}r Plasma- und Lasertechnik (IPLT) der TFH Wildau im Fachbereich Physikalische Technik angestrebt.}, language = {de} } @misc{RichterBrzezinka1995, author = {Richter, Asta and Brzezinka, Klaus-Werner}, title = {Thin Film Deposition and Modification of Fullerenes by Laser Radiation}, series = {Wissenschaftliche Beitr{\"a}ge 1/1995}, volume = {1}, journal = {Wissenschaftliche Beitr{\"a}ge 1/1995}, number = {1}, issn = {0949-8214}, doi = {10.15771/0949-8214_1995_17}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-8118}, pages = {100 -- 103}, year = {1995}, abstract = {Laser ablation from solid fullerene pellet and textured graphite targets has been probed for deposition of thin fullerite and diamond-like carbon (DLC) films by means of a pulsed C02 laser. Ablation of fullerene material does not yield fullerite films, but results in amorphous pregraphitic carbon structures. At very low laser flux structural transformations are observed with increasing exposure time. These thermal effects cannot completely decompose the fullerenes without increase of the laser power density. Thermal evaporation is a suitable method to deposite fullerite fllms of high quality, thus epitaxial fullerite films are grown on mica. Sandwich C60/DLC structures are produced by laser deposition which show a sharp interface as can be deduced from the superposition of the characteristic Raman spectra of the fullerite and the DLC.}, language = {en} } @misc{FranckeRohrbeckRudolphetal.1998, author = {Francke, Klaus-Peter and Rohrbeck, Wolfgang and Rudolph, Rolf and Volkmann, Hans}, title = {1 kW Pulse Corona Reactor for Voc Destruction}, series = {Wissenschaftliche Beitr{\"a}ge 2/1998}, volume = {4}, journal = {Wissenschaftliche Beitr{\"a}ge 2/1998}, number = {2}, issn = {0949-8214}, doi = {10.15771/0949-8214_1998_2_9}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-7546}, pages = {48 -- 50}, year = {1998}, abstract = {A I kW pulse corona reactor has been developed capable of treating gas flows up to 100 m3/h. The discharge efficiency reaches 80 \% in air and nearly 100 \% in nitrogen flows. The efficiency of radical production has been proofed by ozone synthesis as weil as by NO to N2 conversion.}, language = {en} } @misc{BeyerHarendtRolleetal.2000, author = {Beyer, Harald and Harendt, Andreas and Rolle, Siegfried and Ross, Werner and Volkmann, Hans}, title = {TE-CO2-Laser mit variabler Impulsdauer}, series = {Wissenschaftliche Beitr{\"a}ge 2/2000}, volume = {5}, journal = {Wissenschaftliche Beitr{\"a}ge 2/2000}, number = {2}, issn = {0949-8214}, doi = {10.15771/0949-8214_2000_2_2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-7006}, pages = {13 -- 16}, year = {2000}, abstract = {Laserbearbeitungsverfahren wie Pr{\"a}zisionschneiden und Bohren erfordern den Einsatz von Laserimpulsen mit angepasster Impulsleistung (10 kW) und Impulsdauer (10 μs bis zu einigen 100 μs). Transversal elektrisch (TE) angeregte Impuls-CO2 -Laser werden bei Gasdr{\"u}cken bis zu einigen 100 kPa betrieben. In diesem Bereich begrenzen jedoch einsetzende Plasmainstabilit{\"a}ten die m{\"o}gliche elektrische Anregungsdauer f{\"u}r ein homogenes nichtthermisches Entladungsplasma auf einige 100 ns [1]. Eine Verl{\"a}ngerung der Laserimpulsdauer ist durch Ver{\"a}nderung der Energietransportzeit im Lasermedium m{\"o}glich. In [2,3] wurde dies durch eine Herabsetzung des CO2 -Anteils im Gasgemisch sowie durch Herabsetzung des Gasdrucks erreicht. Mit der zus{\"a}tzlichen Verminderung des Heliumanteils [4] kann die Laserimpulsdauer bis zu 1000 μs ausgedehnt werden.}, language = {de} } @misc{BeyerPurschSchumacher2000, author = {Beyer, Harald and Pursch, Heinz and Schumacher, Andreas}, title = {Untersuchung des spektralen Einkoppelverhaltens von Lichtwellenleitersensoren}, series = {Wissenschaftliche Beitr{\"a}ge 2/2000}, volume = {5}, journal = {Wissenschaftliche Beitr{\"a}ge 2/2000}, number = {2}, issn = {0949-8214}, doi = {10.15771/0949-8214_2000_2_3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-7018}, pages = {17 -- 20}, year = {2000}, abstract = {In Schaltanlagen des Niederspannungsnetzes k{\"o}nnen St{\"o}rlichtb{\"o}gen zu erheblichen Sch{\"a}den f{\"u}hren. Die Ursache der Lichtb{\"o}gen ist vielf{\"a}ltig und reicht von {\"U}berschl{\"a}gen an Isolationsstrecken {\"u}ber Blitzeinschl{\"a}ge in das Netz bis zu Kurzschl{\"u}ssen, die bei Wartungs- oder Montagearbeiten verursacht werden k{\"o}nnen. Die Wirkungen von St{\"o}rlichtb{\"o}gen sind erheblich und k{\"o}nnen die Zerst{\"o}rung der Schaltanlage zur Folge haben. Die Kl{\"o}ckner-Moeller GmbH hat ein St{\"o}rlichtbogenschutzsystem (ARCON) entwickelt, das in die Schaltanlagen integriert wird. Da das Auftreten der St{\"o}rlichtb{\"o}gen nicht vorhersehbar ist, wird die gesamte Schaltanlage von Sensoren auf der Basis von Lichtwellenleitern {\"u}berwacht. F{\"u}r diesen Einsatzzweck sind die Sensoren so konzipiert, dass das Licht des Bogens nicht {\"u}ber die Stirnfl{\"a}che des Lichtleiters, sondern seitlich {\"u}ber den Mantel in den Kern eingekoppelt wird. Die Leuchterscheinungen jedes sich bildenden Lichtbogens k{\"o}nnen von dem Sensor erfasst und an einen Detektor weitergeleitet werden, dessen Signal die Schutzmaßnahmen einleitet. Dadurch kann der Strom noch w{\"a}hrend der ersten Halbwelle abgeschaltet und der Schaden begrenzt werden.}, language = {de} } @misc{SchmadlWittl2002, author = {Schmadl, Josef and Wittl, Romel}, title = {Experimentelle Untersuchung des W{\"a}rme{\"u}bergangs beim Sieden bin{\"a}rer Stoffgemische aus Aceton und Ethanol}, series = {Wissenschaftliche Beitr{\"a}ge 2002}, volume = {7}, journal = {Wissenschaftliche Beitr{\"a}ge 2002}, issn = {0949-8214}, doi = {10.15771/0949-8214_2002_10}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6915}, pages = {59 -- 65}, year = {2002}, abstract = {Das Sieden und besonders das in dieser Arbeit ausschließlich behandelte vollausgebildete Blasensieden ist immer dann die bevorzugte Form der W{\"a}rme{\"u}bertragung an Fl{\"u}ssigkeiten, wenn hohe W{\"a}rmestr{\"o}me pro Heizfl{\"a}cheneinheit und pro K Heizwand{\"u}berhitzung {\"u}bertragen werden sollen. In vielen F{\"a}llen werden dabei nicht reine Stoffe, sondern Stoffgemische eingesetzt, z. B. bei der K{\"u}hlung von Chemiereaktoren oder bei der thermischen Trennung von Stoffgemischen (Destillation, Rektifikation und Eindampfung zwecks Kristallisation). Dabei ist zu ber{\"u}cksichtigen, dass der W{\"a}rme{\"u}bergangskoeffizient beim Blasensieden von Gemischen wegen des kombinierten W{\"a}rme- und Stoff{\"u}bergangs in der Regel kleiner als bei reinen Stoffen ist. Besonders bei hohen W{\"a}rmestromdichten, hohen Dr{\"u}cken und hohen relativen Fl{\"u}chtigkeiten der beteiligten Stoffkomponenten kann dieser „Gemischeffekt" den W{\"a}rme{\"u}bergangskoeffizienten um Faktor 10 und mehr herabsetzen, was in der Apparateauslegung ber{\"u}cksichtigt werden muss.}, language = {de} } @misc{SchmadlWittl2002, author = {Schmadl, Josef and Wittl, Romel}, title = {Korrelation der Konzentrations- und Druckabh{\"a}ngigkeit des W{\"a}rme{\"u}bergangskoeffizienten beim Sieden von bin{\"a}ren Stoffgemischen aus Aceton und Ethanol}, series = {Wissenschaftliche Beitr{\"a}ge 2002}, volume = {7}, journal = {Wissenschaftliche Beitr{\"a}ge 2002}, issn = {0949-8214}, doi = {10.15771/0949-8214_2002_11}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6927}, pages = {66 -- 70}, year = {2002}, abstract = {Bislang gibt es keine einheitliche Theorie, um den W{\"a}rme{\"u}bergang beim Blasensieden in freier Konvektion f{\"u}r bin{\"a}re Gemische ohne experimentelle Daten und mit ausreichender Genauigkeit vorauszuberechnen. In der Literatur gibt es jedoch zahlreiche Korrelationsgleichungen bzw. Modelle f{\"u}r die praktische Berechnung des W{\"a}rme{\"u}bergangskoeffizienten (W{\"U}K). Diese Modelle oder Gleichungen sind empirische oder halbempirische Ans{\"a}tze, die nur auf spezielle Stoffpaare anwendbar oder auf niedrige Siededr{\"u}cke beschr{\"a}nkt sind oder nicht alle Einflussparameter enthalten.}, language = {de} } @article{VandenhoutenWendlandt2015, author = {Vandenhouten, Ralf and Wendlandt, Ole}, title = {High-precision Optical Position Measurement in Indoor Environments}, series = {Optik \& Photonik}, volume = {10}, journal = {Optik \& Photonik}, number = {3}, issn = {1863-1460}, doi = {10.1002/opph.201500022}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9305}, pages = {24 -- 27}, year = {2015}, abstract = {Indoor localization is still a challenge today. Conventional methods based on satellite navigation, like GPS, can only be used outdoors. On the other hand, radio signal architectures, like WiFi or NFC, require high cost infrastructure to be installed inside the building. In collaboration with Ixellence GmbH, the research group for telematics of the University of Applied Science Wildau is developing a new inexpensive solution based on the camera of a mobile device. This approach only requires the availability of multiple identifiable landmarks that can be installed cost-efficiently in an indoor environment. Our investigations show that this method is very accurate and can produce repeatable, robust results.}, language = {en} } @inproceedings{BauerHeinrichFursenkoetal.2017, author = {Bauer, Joachim and Heinrich, Friedhelm and Fursenko, Oksana and Marschmeyer, Steffen and Bluemich, Adrian and Pulwer, Silvio and Steglich, Patrick and Villringer, Claus and Mai, Andreas and Schrader, Sigurd}, title = {Very high aspect ratio through silicon via reflectometry}, series = {Proceedings of SPIE}, booktitle = {Proceedings of SPIE}, issn = {1996-756X}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13758}, year = {2017}, abstract = {Through Silicon Via (TSV) technology is a key feature of new 3D integration of circuits by creation of interconnections using vias, which go through the silicon wafer. Typically, the highly-selective Bosch Si etch process, characterized by a high etch rate and high aspect ratio and forming of scallops on the sidewalls is used. As presented in this paper, we have developed an experimental setup and a respective evaluation algorithm for the control and monitoring of very high aspect ratio TSV profiles by spectroscopic reflectometry. For this purpose square via arrays with lateral dimension from 3 to 10 μm were fabricated by a Bosch etch process and analyzed by our setup. By exploiting interference and diffraction effects of waves reflected from the top and bottom surfaces as well as from the side walls of the TSV patterns, the measurements provided etch depths, CD values and scallop periods. The results were compared with data obtained by a commercial wafer metrology tool. Aspect ratios of up to 35:1 were safely evaluable by our setup.}, language = {en} } @inproceedings{VillringerGilaniZhangetal.2019, author = {Villringer, Claus and Gilani, Taravat Saeb and Zhang, Edward and Pulwer, Silvio and Steglich, Patrick and Schrader, Sigurd and Laufer, Jan}, title = {Development of tuneable Fabry-P{\´e}rot sensors for parallelised photoacoustic signal acquisition}, series = {Proc. SPIE 10878, Photons Plus Ultrasound: Imaging and Sensing 2019, 108780M (8 March 2019)}, booktitle = {Proc. SPIE 10878, Photons Plus Ultrasound: Imaging and Sensing 2019, 108780M (8 March 2019)}, issn = {1996-756X}, doi = {10.1117/12.2509437}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13769}, year = {2019}, abstract = {Fabry-P{\´e}rot (FP) sensors have enabled high resolution 3D photoacoustic (PA) imaging in backward mode. However, raster-scanning of the interrogation laser beam across the sensor can result in slow 3D image acquisition. To overcome this limitation, parallelized PA signal acquisition can be used for which FP sensors with uniform optical thickness are required. In this work, the optical thickness is tuned a) irreversibly through the use of a photopolymer host matrix and b) actively using embedded electro-optic (EO) chromophores. Polymer spacers (5 μm) were deposited using spin coating and sandwiched between two dielectric mirrors and transparent ITO electrodes. The employed polymer guest-host system consists of an EO chromophore (2-methyl-4-nitroaniline) and poly(vinyl cinnamate). EO tuneability was induced using contact poling and a tuneability of 68 pm was demonstrated. The optical thickness was homogenised by raster scanning a UV beam whilst varying the exposure time across a 4 mm2 detection aperture.}, language = {en} } @inproceedings{ChepurnaGrebinykPetrushkoetal.2019, author = {Chepurna, Oksana and Grebinyk, Anna and Petrushko, Yulia and Prylutska, Svitlana and Grebinyk, Sergii and Yashchuk, Valeriy and Matyshevska, Olga and Ritter, Uwe and Dandekar, Thomas and Frohme, Marcus and Qu, Junle and Ohulchanskyy, Tymish Y.}, title = {LED-based portable light source for photodynamic therapy}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14778}, year = {2019}, abstract = {Photodynamic therapy (PDT) employs light activation of tissue-localized photosensitizer in an oxygen-dependent process which initiates oxidative stress, inflammation, and cell death. Laser systems, which are mostly used in PDT as light sources can be costly and oversized. light-emitting diodes (LEDs) equipment has a high potential to simplify technical part of phototriggered therapies and to reduce its costs. We develop the LED-based system that includes the control and irradiation units. The system provides the same power density at any irradiation point. Among the advantages of the device is a possibility to change the irradiation area and tune the irradiation dose. PDT experiments with cancer cells in vitro treated with two different photosensitizers demonstrated a possibility to use the developed LED-based system as a low-cost light source in PDT.}, language = {en} } @inproceedings{PulwerFiebelkornZeschetal.2019, author = {Pulwer, Silvio and Fiebelkorn, Richard and Zesch, Christoph and Steglich, Patrick and Villringer, Claus and Villasmunta, Francesco and Gedat, Egbert and Handrich, Jan and Schrader, Sigurd and Vandenhouten, Ralf}, title = {Endoscopic orientation by multimodal data fusion}, series = {Proc. SPIE 10931, MOEMS and Miniaturized Systems XVIII}, booktitle = {Proc. SPIE 10931, MOEMS and Miniaturized Systems XVIII}, issn = {1996-756X}, doi = {10.1117/12.2508470}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-11420}, year = {2019}, abstract = {To improve the feasibility of endoscopic inspection processes we developed a system that provides online information about position, orientation and viewing direction of endoscopes, to support the analysis of endoscopic images and to ease the operational handling of the equipment. The setup is based on an industrial endoscope consisting of a camera, various MEMS and multimodal data fusion. The software contains algorithms for feature and geometric structure recognition as well as Kalman filters. To track the distal end of the endoscope and to generate 3D point cloud data in real time the optical and photometrical characteristics of the system are registered and the movement of the endoscope is reconstructed by using image processing techniques.}, language = {en} } @article{BondarenkoHuelsemannMaietal.2021, author = {Bondarenko, Siegfried and H{\"u}lsemann, Marcel and Mai, Andreas and Steglich, Patrick}, title = {Fiber-to-chip light coupling using a graded-index lensed fiber collimator}, series = {Optical Engineering}, volume = {60}, journal = {Optical Engineering}, number = {1}, publisher = {SPIE}, issn = {1560-2303}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13749}, year = {2021}, abstract = {Fiber-to-chip light coupling using a graded-index (GRIN) fiber collimator is investigated. Our experiments with grating couplers and strip waveguides fabricated in a photonic integrated circuit technology reveal that the peak coupling efficiency of a GRIN fiber collimator is 7.8 dB lower than that of a single-mode fiber. However, the 3-dB alignment tolerance is improved by a factor of about 5.7 giving rise to pluggable sensor solutions. This work opens a path toward a cost-effective and portable sensor platform based on pluggable photonic biosensors using GRIN fiber collimators.}, language = {en} } @article{KagelJacobsBieretal.2019, author = {Kagel, Heike and Jacobs, Hannes and Bier, Frank Fabian and Gl{\"o}kler, J{\"o}rn and Frohme, Marcus}, title = {A Novel Microtiter Plate Format High Power Open Source LED Array}, series = {Photonics}, volume = {6}, journal = {Photonics}, number = {1}, issn = {2304-6732}, doi = {10.3390/photonics6010017}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-11307}, year = {2019}, abstract = {Many photochemical or photobiological applications require the use of high power ultraviolet light sources, such as high-pressure mercury arc lamps. In addition, many photo-induced chemical, biochemical and biological applications require either a combinatorial setting or a parallel assay of multiple samples under the same environmental conditions to ensure reproducibility. To achieve this, alternative, controllable light sources, such as ultraviolet light emitting diodes (UV LEDs) with high power and spatial control are required. Preferably, LEDs are arranged in a suitable standardized 96-well microtiter plate format. We designed such an array and established the methods required for heat management and enabling stable, controllable illumination over time.}, language = {en} } @article{JurkovičovaBenLtaiefRoosetal.2024, author = {Jurkovičov{\´a}, Lucie and Ben Ltaief, Ltaief and Roos, Andreas Hult and Hort, Ondřej and Finke, Ondřej and Albrecht, Martin and Hoque, Ziaul and Klimešov{\´a}, Eva and Sundaralingam, Akgash and Antipenkov, Roman and Grenfell, Annika and Špaček, Alexandr and Szuba, Wojciech and Krikunova, Maria and Mudrich, Marcel and Nejdl, Jaroslav and Andreasson, Jakob}, title = {Bright continuously tunable vacuum ultraviolet source for ultrafast spectroscopy}, series = {Communications Physics}, volume = {7}, journal = {Communications Physics}, publisher = {Nature Publishing Group}, issn = {2399-3650}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18462}, year = {2024}, abstract = {Ultrafast electron dynamics drive phenomena such as photochemical reactions, catalysis, and light harvesting. To capture such dynamics in real-time, femtosecond to attosecond light sources are extensively used. However, an exact match between the excitation photon energy and a characteristic resonance is crucial. High-harmonic generation sources are advantageous in terms of pulse duration but limited in spectral tunability in the vacuum ultraviolet range. Here, we present a monochromatic femtosecond source continuously tunable around 21eV photon energy utilizing the second harmonic of an optical parametric chirped pulse amplification laser system to drive high-harmonic generation. The unique tunability of the source is verified in an experiment probing the interatomic Coulombic decay in doped He nanodroplets across the He absorption bands. Moreover, we achieved intensities sufficient for driving collective processes in multiply excited helium nanodroplets, which have been previously observed only at free electron lasers.}, language = {en} } @article{MedinaLagdsmandBenLtaiefetal.2023, author = {Medina, Cristian and L{\ae}gdsmand, Asbj{\o}rn {\O}rnemark and Ben Ltaief, Ltaief and Hoque, Ziaul and Roos, Andreas Hult and Jurkovičov{\´a}, Lucie and Hort, Ondřej and Finke, Ondřej and Albrecht, Martin and Nejdl, Jaroslav and Stienkemeier, Frank and Andreasson, Jakob and Klimešov{\´a}, Eva and Krikunova, Maria and Heidenreich, Andreas and Mudrich, Marcel}, title = {Long-lasting XUV activation of helium nanodroplets for avalanche ionization}, series = {New Journal of Physics}, volume = {25}, journal = {New Journal of Physics}, publisher = {Institute of Physics (IOP)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17701}, year = {2023}, abstract = {We study the dynamics of avalanche ionization of pure helium nanodroplets activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense near-infrared (NIR) pulse. In addition to a transient enhancement of ignition of a nanoplasma at short delay times \${\sim}200\$ fs, long-term activation of the nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics simulations suggest that the short-term activation is caused by the injection of seed electrons into the droplets by XUV photoemission. Long-term activation appears due to electrons remaining loosely bound to photoions which form stable 'snowball' structures in the droplets. Thus, we show that XUV irradiation can induce long-lasting changes of the strong-field optical properties of nanoparticles, potentially opening new routes to controlling avalanche-ionization phenomena in nanostructures and condensed-phase systems.}, language = {en} } @article{SmekhovaSzyjkaLaTorreetal.2024, author = {Smekhova, Alevtina and Szyjka, Thomas and La Torre, Enrico and Ollefs, Katharina and Eggert, Benedikt and Coester, Birte and Wilhelm, Fabrice and Bali, Rantej and Lindner, J{\"u}rgen and Rogalev, A. and T{\"o}bbens, Daniel Maria and Weschke, Eugen and Luo, Chen and Chen, Kai and Radu, Florin and Schmitz-Antoniak, Carolin and Wende, Heiko}, title = {Irradiation-induced enhancement of Fe and Al magnetic polarizations in Fe60Al40 films}, series = {New Journal of Physics}, volume = {26}, journal = {New Journal of Physics}, publisher = {Institute of Physics Publishing (IOP)}, issn = {1367-2630}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18381}, year = {2024}, abstract = {The rise of Fe magnetic moment, changes in Al electronic structure and a variation of Al magnetic polarization in thin films of transition metal aluminide Fe60Al40 have been probed through the order-disorder phase transition by soft X-ray absorption spectroscopy and X-ray resonant magnetic reflectivity in the extreme ultraviolet regime. In a course of the transition induced by 20 keV Ne+ irradiation with low fluences (1014 ions·cm-2), X-ray magnetic circular dichroism spectra taken at the Fe L2,3 absorption edges at room and low temperatures revealed a pronounced increase of Fe 3d states spin-polarization. X-ray resonant magnetic reflectivity applied to the Al L2,3 and Fe M2,3 edges allowed to detect the magnetic polarization of Al atoms in the films. The changes in Al electronic structure have been seen by alteration of Al K edge X-ray absorption near edge structure. A difference in anisotropy fields for films before and after irradiation has been observed by element-specific hysteresis loops recorded at low temperatures in absorption and reflection geometries at the Fe L2,3 and M2,3 edges, respectively. An attempt to reduce the top oxide layer by an inductively coupled hydrogen plasma has shown a possibility to recover the chemically ordered phase.}, language = {en} } @inproceedings{KupperMuehligJakobeschky2024, author = {Kupper, Stefan and M{\"u}hlig, Verena and Jakobeschky, Laura}, title = {AD3D - Eine automatisierte Toolchain f{\"u}r das 3D-Drucken}, series = {Tagungsband AALE 2024 : Fit f{\"u}r die Zukunft: Praktische L{\"o}sungen f{\"u}r die industrielle Automation}, booktitle = {Tagungsband AALE 2024 : Fit f{\"u}r die Zukunft: Praktische L{\"o}sungen f{\"u}r die industrielle Automation}, editor = {Reiff-Stephan, J{\"o}rg and J{\"a}kel, Jens and St{\"o}cker, Christian}, publisher = {Hochschule f{\"u}r Technik, Wirtschaft und Kultur}, address = {Leipzig}, isbn = {978-3-910103-02-3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18553}, pages = {259 -- 263}, year = {2024}, abstract = {Der technische Fortschritt hat dazu gef{\"u}hrt, dass die Kosten f{\"u}r das automatisierte Drucken von Emblemen, Anh{\"a}ngern sowie allgemein gedruckten Prototypen stark gefallen sind. Dies geschah insbesondere auch vor dem Hintergrund eines Wandels der Industrie hin zu einer modernen Industrie 4.0. In dieser Arbeit wird ein neuer Ansatz f{\"u}r das automatische 3D-Drucken eines Logos pr{\"a}sentiert, welches als Pixelgrafik vorliegt. Die vorgeschlagene Prozesskette erzeugt hierbei final den G-code zum Drucken. Dabei sind seitens des Users wenige Eingaben erforderlich.}, language = {de} } @article{LuxSiemrothSgarlataetal.2015, author = {Lux, Helge and Siemroth, Peter and Sgarlata, Anna and Prosposito, Paolo and Schubert, Markus Andreas and Casalboni, Mauro and Schrader, Sigurd}, title = {Synthesis of graphene-like transparent conductive films on dielectric substrates using a modified filtered vacuum arc system}, series = {Journal of Applied Physics}, volume = {117}, journal = {Journal of Applied Physics}, number = {19}, issn = {1089-7550}, doi = {10.1063/1.4921448}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9738}, year = {2015}, abstract = {Here, we present a reliable process to deposit transparent conductive films on silicon oxide, quartz, and sapphire using a solid carbon source. This layer consists of partially ordered graphene flakes with a lateral dimension of about 5 nm. The process does not require any catalytic metal and exploits a high current arc evaporation (Φ-HCA) to homogeneously deposit a layer of carbon on heated substrates. A gas atmosphere consisting of Argon or Argon/Hydrogen blend acting as a buffer influences the morphology of the growing film. scanning tunneling microscopy, transmission electron microscopy, and Raman spectra were used for a thorough characterization of the samples in order to optimize the growth parameters. The best carbon layers have a surface resistance of 5.7 × 103 Ω◻ whereas the optical transparency of the coatings is 88\% with an excellent homogeneity over areas of several cm2. Such results are compatible with most semiconductor fabrication processes and make this method very promising for various industrial applications.}, language = {en} } @article{SteglichMaiVillringeretal.2018, author = {Steglich, Patrick and Mai, Christian and Villringer, Claus and Pulwer, Silvio and Casalboni, Mauro and Schrader, Sigurd and Mai, Andreas}, title = {Quadratic electro-optic effect in silicon-organic hybrid slot-waveguides}, series = {Optics Letters}, volume = {43}, journal = {Optics Letters}, number = {15}, issn = {1539-4794}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12148}, year = {2018}, abstract = {This Letter reports on the quadratic electro-optic effect of polymers, observed in a silicon slot-waveguide at low voltages. We demonstrate that in narrow slots, the electro-optic response with respect to refractive index change is strong enough for on-chip wavelength tuning and intensity modulation using voltages as low as 1 V. A silicon slot-waveguide embedded by a nonlinear optical polymer, consisting of the dye Disperse Red 1 in poly(methyl methacrylate), serves as the phase shifter in a racetrack ring resonator. As deduced from the experimental data, the third-order susceptibility of the utilized electro-optic polymer is about 2·10-19 m2/V2. The demonstrated low-voltage operation and inherently thermal stability show the potential for silicon-organic hybrid devices using the quadratic electro-optic effect.}, language = {en} } @inproceedings{SteglichMaiStolareketal.2016, author = {Steglich, Patrick and Mai, Christian and Stolarek, David and Lischke, Stefan and Kupijai, Sebastian and Villringer, Claus and Pulwer, Silvio and Heinrich, Friedhelm and Bauer, Joachim and Meister, Stefan and Knoll, Dieter and Casalboni, Mauro and Schrader, Sigurd}, title = {Partially slotted silicon ring resonator covered with electro-optical polymer}, series = {Proceedings of SPIE}, booktitle = {Proceedings of SPIE}, issn = {1996-756X}, doi = {10.1117/12.2217725}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13771}, year = {2016}, abstract = {In this work, we present for the first time a partially slotted silicon ring resonator (PSRR) covered with an electro-optical polymer (Poly[(methyl methacrylate)-co-(Disperse Red 1 acrylate)]). The PSRR takes advantage of both a highly efficient vertical slot waveguide based phase shifter and a low loss strip waveguide in a single ring. The device is realized on 200 mm silicon-on-insulator wafers using 248 nm DUV lithography and covered with the electro-optic polymer in a post process. This silicon-organic hybrid ring resonator has a small footprint, high optical quality factor, and high DC device tunability. A quality factor of up to 105 and a DC device tunability of about 700 pm/V is experimentally demonstrated in the wavelength range of 1540 nm to 1590 nm. Further, we compare our results with state-of-the-art silicon-organic hybrid devices by determining the poling efficiency. It is demonstrated that the active PSRR is a promising candidate for efficient optical switches and tunable filters.}, language = {en} } @article{GerhardLetienCressentetal.2020, author = {Gerhard, Christoph and Letien, Emilie and Cressent, Thomas and Hofmann, Mandy}, title = {Inline monitoring of hydrogenous plasma-induced defect formation within fused silica via plasma emission spectroscopy}, series = {Applied Physics A: Materials Science and Processing}, volume = {126}, journal = {Applied Physics A: Materials Science and Processing}, issn = {1432-0630}, doi = {10.1007/s00339-020-3347-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13118}, year = {2020}, abstract = {In this paper, the indirect monitoring of plasma-induced defect formation within fused silica via plasma emission spectroscopy is presented. It is shown that low-pressure plasma treatment with hydrogen as process gas leads to a decrease in UV transmission of fused silica. This decrease can be directly attributed to oxygen vacancy-related defects and the presence of hydrogen within the silicon dioxide glass network. By the analysis of the plasma composition, it was observed that the amount of oxygen within the plasma increases with increasing treatment duration. Hence, oxygen was continuously released from glass network in the course of the plasma treatment. It was further observed that this release is strongly dependent on the applied plasma power where the lowest process efficiency occurs at the highest plasma power. It is shown that an increase in plasma power leads to a remarkable increase in light emission from the working gas, hydrogen. This observation indicates that the higher the degree of excitation and ionisation of the plasma, the lower the efficiency of plasma-induced formation of oxygen deficiency-related defects. This finding is of mentionable relevance for a better understanding of plasma-induced surface modification and coating processes.}, language = {en} } @inproceedings{N’TsoukpoeKoFalcozetal.2020, author = {N'Tsoukpoe, Kokouvi Edem and Ko, Ga{\"e}lle Kafira and Falcoz, Quentin and Coulibaly, Y{\´e}zouma}, title = {Design, construction and experimental investigation of a linear Fresnel concentrator for sustainable energy services in Sub-Saharan Africa}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13194}, pages = {7 -- 16}, year = {2020}, abstract = {Concentrating solar power (CSP) is considered as one of the promising ways for future sustainable electricity generation, especially in the Sahel region, which is characterized by high direct solar irradiation, but also severe and acute energy poverty. In this paper, we focus on the linear Fresnel system, which it is probably the simplest CSP technology and presents the lowest investment costs. However, it is the less investigated CSP technology and several authors expect significant cost reduction of this technology. Therefore, deeper knowledge on the technology is required. We aim at investigating the coupling of a linear Fresnel system with various energy processes in order to bring out its interests for the Sahel region and, hence, provide sustainable energy services such as electricity generation for rural areas, cooling and refrigeration via sorption cold production, hot water or steam supply for semi-industrial or industrial processes. We have built a linear Fresnel collector of 7.5 m2. The receiver has been designed as a trapezoidal receiver with multi-tubular absorber; it has been experimentally investigated in order to determine its thermal performance, especially the heat loss coefficients. Jatropha curcas oil, a locally produced non-edible vegetable oil is used as heat transfer fluid. The concentrator has been characterised in order to find its optical, thermal and global efficiencies. Paths for the prototype performance improvement have been identified and examined.}, language = {en} } @inproceedings{ReiffStephan2020, author = {Reiff-Stephan, J{\"o}rg}, title = {Implementation approaches for distributed energy management systems in production}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIV-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13220}, pages = {116 -- 124}, year = {2020}, abstract = {The energy management of manufacturing facilities must be taken increasing account for an efficient operation within a production process. Future efforts and solutions will focus on improvement of the process stability and on cost reduction to meet the needs of successfully compete in local and global markets especially for SME. The paper describes an approach for manufacturing facilities using an example for thermoprocessing equipment. For this purpose, the TPS-principle Jidōka is used, the mechanism of self-adapting limit setting as well as an implementation is presented prototypically.}, language = {en} } @inproceedings{ReiffStephan2020, author = {Reiff-Stephan, J{\"o}rg}, title = {Solar power in product development}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13206}, pages = {55 -- 65}, year = {2020}, abstract = {The availability of electrical energy is one of the essential basic elements for economic growth and humanitarian living conditions. In one of the poorest regions of Western Africa - in the savannah region of northern Togo - the central expansion of electricity grids has not taken place. Decentralized solutions based on renewable energy systems can help here and promote the region's development. In the presented paper, the various renewable energy carrier systems were examined with regard to their use in the savannah region of Western Africa. The solar energy carrier system could be used as a power supplier in the secondary conversion process to mechanical power. Subsequently, a prototype for a clay brick production machine was designed and a digital mock-up was developed. Together with the partners in Togo, the prototype is built and tested in the field. Experiences are being gathered in cooperation with Bonita-Haus and will be incorporated into the educational content in Togo as well as at the Technical University of Wildau. This will make a significant contribution to the utilization of the technology at the site and to improving the living conditions in Western Africa.}, language = {en} } @inproceedings{GieseFuerkus2020, author = {Giese, Lutz B. and F{\"u}rkus, Stefan}, title = {A Short Approximation Method to Pre-estimate the Electric Yield of Wind Farms}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-2b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13256}, pages = {34 -- 40}, year = {2020}, abstract = {Amongst the Renewable Energy Sources (RES) contributing to the worldwide electricity production, wind energy became very important. Germany and several other countries own significant wind potentials. 2\% of a country's area can be used for wind farms, thus Germany could produce easily up to 200 TWhel yearly just onshore. However, often legal and especially financial aspects decide about the speed of development. Careful project preparation guaranteed by professional management is obligatory. Beside factors such as (i) rights to the property and (ii) electric grid connection, (iii) the sufficiency of the wind and peripheral conditions need to be known. A proper wind forecast and yield prognoses are important items. To solve these tasks, professional programs are sold on the markets. To offer a convenient alternative, authors will present software based on Excel named as WindCalc 1.5, which is still under development.}, language = {en} } @inproceedings{Giese2020, author = {Giese, Lutz B.}, title = {Turnaround in Energy Policy - Measures to Reduce the Carbon Dioxide Emission from the Private Sector}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13248}, pages = {81 -- 86}, year = {2020}, abstract = {The greenhouse gases (GHG) carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) are considered mainly to be responsible for the additional anthropogenic greenhouse effect, the so-called "global warming". In the private sector, the "Rational Use of Energy" can be a very effective tool (i) to reduce the greenhouse gas emissions, (ii) to decrease the annual energy costs and furthermore (iii) it prepares the integration of Renewable Energy Sources by saving conventional, mostly fossil energy. Aim of this paper is (i) to show that by applying energy saving measures, the primary energy demand and thus the individual (direct) carbon dioxide emission can be reduced in a relevant scale. (ii) It is to give laterally information about (ii.i) the energy market structure and (ii.ii) the legal backgrounds in the EU.}, language = {en} } @inproceedings{AfenyivehAdanleteAdjanohDouti2020, author = {Afenyiveh, Serge Dzo Mawuefa and Adanlete Adjanoh, Assiongbon and Douti, Dam-Be Lardja}, title = {Optical simulation of a parabolic solar concentrator}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-2a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13238}, pages = {66 -- 72}, year = {2020}, abstract = {This work presents a 3D ray tracing approach for the optical simulation of a parabolic solar concentrator for a thermo-magnetic (Curie motor) experiment. An approach based on Snell's law of reflection (geometrical optics) in vector form is used in this study. We consider the solid angle of the sun through a rotation of the concentrator around an axis. This paper aims to set up a digital technical tool as flexible as possible for applications in the field of renewable energy.Mathematical modelling as well as numerical simulation in Python environment are presented. The aim of the proposed algorithm is to be used for the concentration of light rays on any optical system, symmetrical or not. Better yet, offers a solar tracking model.}, language = {en} } @inproceedings{SteglichPaulMaietal.2021, author = {Steglich, Patrick and Paul, Martin and Mai, Christian and B{\"o}hme, Andrea and Bondarenko, Siegfried and Weller, Michael G. and Mai, Andreas}, title = {A monolithically integrated micro fluidic channel in a silicon-based photonic-integrated-circuit technology for biochemical sensing}, series = {Proc. SPIE 11772, Optical Sensors 2021}, booktitle = {Proc. SPIE 11772, Optical Sensors 2021}, doi = {10.1117/12.2588791}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13925}, year = {2021}, abstract = {In this work, a cost-effective optofluidic system is propossed and preliminary experimental results are presented. A microfluidic channel monolithically integrated into a photonic integrated circuit technology is used in conjunc- tion with a cyclo-olefin copolymer (COC) substrate to provide fluidic in- and output ports. We report on initial experimental results as well as on the simple and cost-effective fabrication of this optofluidic system by means of micro-milling.}, language = {en} } @inproceedings{OPUS4-1342, title = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, editor = {Amouzou, Kou 'santa and Adanlete Adjanoh, Assiongbon and Reiff-Stephan, J{\"o}rg}, isbn = {978-3-9819225-5-4}, doi = {10.15771/978-3-9819225-5-4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13424}, year = {2020}, abstract = {Conference Proceedings of the 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes. 1st July 2020 - Kara, Togo.}, language = {en} } @inproceedings{N’GobiDonnouAgbazoetal.2020, author = {N'Gobi, Gabin Koto and Donnou, Hagninou E. V. and Agbazo, M{\´e}dard and Akpo, Aristide. B. and Kounouhewa, Basile B.}, title = {Estimation of the Global Solar Radiation Received on the Soil in Nalohou and Natitingou (Northern Benin)}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13376}, pages = {41 -- 54}, year = {2020}, abstract = {The design of solar energy systems requires knowledge of the global solar radiation received by solar panels on the ground. However, for many developing countries such as the Benin Republic, there is a serious lack of radiometric stations everywhere in the country. The unavailability of these data, therefore, limits knowledge regarding the optimal functioning of solar installations. To cope with these difficulties, a method for estimating the global irradiation is developed at Nalohou AMMA CATCH station and Natintingou synoptic station, two sites in North-West Benin. This model depends on meteorological and astronomical parameters. Meteorological data such as sunshine duration, relative humidity, and air temperature have been collected on the synoptic station of Natitingou, and observed data of irradiation are collected from Nalohou. They are used to validate the model. The results show that the estimation of the mean square deviation value is around 10 -2 . Overall solar radiation is significant in this region and its annual average value varies between 9.80 kWh/m2 and 10.50 kWh/m2. This model can, therefore, be used by solar system operators to optimize energy production in the region.}, language = {en} } @inproceedings{vandeSandCorasanitiReiffStephan2020, author = {van de Sand, Ron and Corasaniti, Sandra and Reiff-Stephan, J{\"o}rg}, title = {Review of Condition Based Maintenance approaches for vapor compression refrigeration systems}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-2a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13369}, pages = {24 -- 33}, year = {2020}, abstract = {Vapor compression refrigeration systems are subject to performance degradation over time due to the presence of faults. However, latest work in the field of condition-based maintenance shows promising results in the automatic early detection of anomalous behaviour as well as in accurate machine diagnostics and can, therefore, increase the overall system reliability by simultaneously preventing machine downtimes. In this paper, the latest research works carried out within the last decade are reviewed and the approaches are classified regarding their working principles. Furthermore, the work at hand depicts the current research trend in this field and outlines current obstacles.}, language = {en} } @inproceedings{SmajicDuspara2020, author = {Smajic, H. and Duspara, T.}, title = {Design and manufacturing of an unmanned aerial vehicle with air quality control system}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13396}, pages = {87 -- 93}, year = {2020}, abstract = {Within the scope of this project, a fully functional model of an unmanned aerial vehicle with an air control system was developed and implemented as a prototype. By using the mobile measuring stations, it is feasible to measure the air quality in any part of the city, independent of the measuring altitude.}, language = {en} } @inproceedings{Dable2020, author = {Dable, Etienne}, title = {Construction of PV Systems for Elementary Schools in the Savannah of Togo}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIV-1a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13415}, pages = {111 -- 115}, year = {2020}, abstract = {The savannah region in northern Togo borders on Ghana, Burkina Faso and Benin (Figure 1). It covers 8,596 km2, which is 15\% of the total area of Togo. The regional capital Dapaong has about 100,000 inhabitants. The savannah region consists of 5 prefectures, 70 cantons, 1,073 villages and 451 hamlets. The number of inhabitants is growing rapidly. The population figures were 828,224 in 2010 and 890,403 in 2013, a growth rate of 8.2\% in only 3 years. With 105 inhabitants per km2 the savannah region is more densely populated than German Mecklenburg-Vorpommern (69 inhabitants per km2). The savannah region is the poorest region in the country. In the villages, subsistence farming prevails. Surpluses are sold at village markets or nearby city markets with little profit, since raw products are rarely processed and certainly not processed and the purchasing power in the region is low. The sensitive savannah floors are overused. During the long dry season (October to May) there is a lack of artificial irrigation. The climate change affects the savannah region through shorter and irregular rainy seasons. Deforestation leads to further drying out of the soil. The population is increasing, becoming poorer and poorer and uses almost exclusively wood for cooking in the villages. This leads to further deterioration of the arable land. Harvest yields are falling because improved seeds and fertilisers are also lacking. The infrastructure in the region is at an extremely low level. There are no industrial enterprises in the savannah region. There is an almost complete lack of companies that process and refine agricultural products. There is a lack of storage facilities and cold chains for agricultural products. Only for wood and charcoal there are transport routes from the international highway to regions with better purchasing power. A major obstacle to the establishment of small businesses is the lack of electricity.}, language = {en} } @inproceedings{KrouBabaSegbeayaetal.2020, author = {Krou, Nitale M'Balikine and Baba, Gnon and Segbeaya, Kwamivi N. and Akpaki, Ogouvid{\´e}}, title = {Energy recovery from sewage sludge and fermentable fractions of solid waste from the city of Sokode by co-digestion}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-2a}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13262}, pages = {94 -- 101}, year = {2020}, abstract = {One of the consequences of the improvement of the living conditions of the populations is the strong demand in thermal energy for the households whereas in the developing countries, the cost of living is a brake with all the social layers to reach supply of butane gas for their energy needs. This study takes place in the context of energy, environmental and sanitation challenges in the city of Sokod{\´e}. Indeed, we are witnessing more and more growing needs for butane gas, firewood or charcoal for cooking or lighting in the city of Sokod{\´e} as everywhere in other cities of the same size. Thus by the production of energy in situ, the condition of the populations will be able to improve significantly thanks to the recovery of sludge and fermentable fractions of solid waste into biogas. The objective of this work is to produce and recover methane from fermentable waste produced in the city of Sokod{\´e}. The methane or biogas recovered will be used as fuel to fuel kitchens in households. The resulting digestate will serve as an organic amendment to agricultural soils in the commune of Sokod{\´e}. Laboratory scale tests have been carried out to validate the value of co-digestion of sewage sludge with fermentable solid waste. The results obtained have shown that the methanogenic potential of sewage sludge is low compared to that of fermentable solid waste. The co-digestion of the two products allows a greater production of methane representing an energy gain compared to the methanisation of the sewage sludge alone. This study shows that waste (sludge from public septic tanks, waste from markets, hotels and fermentable households) can be considered an appreciable energy resource. Their Co-treatment would, while reducing the nuisance associated with this waste, produce valuable energy.}, language = {en} } @inproceedings{LiskerNowitzkiHellwigetal.2020, author = {Lisker, Roberto and Nowitzki, Mario and Hellwig, Udo and Wildenauer, Franz-Xaver}, title = {Comparable numerical study on different working fluids for micro scale power cycle integrated into a pellet fired boiler}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SII-2b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13383}, pages = {73 -- 80}, year = {2020}, abstract = {A cost-effective power cycle shall be developed to supply heat and electricity (co-generation). The aim of this study is to find an appropriate power cycle and working fluid for a friction turbine application. Due to its low production costs, better scalability and low-maintenance requirements, a friction turbine, also known as Tesla turbine, shall be used. In order to find a proper working fluid and estimate the efficiency and power output,a numerical study was performed on five promising working fluids namely Xenon, Argon, Helium, Air and superheated Steam. The simulation model consists of three disks with a diameter of 0,25 m and an outlet diameter of 0,12 mm rotating at constant 10.000 rpm.It is tried to keep the Gap Reynolds number at a constant 73, to ensure a laminar flow regime between the disks. The outcome of the numerical study showed that all working fluids are suitable. The highest efficiency (shaft power / technical power) has been achieved with steam (96\%) and a power output of 126 W/gap. The least efficiency with 89\% has been realized with air and a Power output of 118 W/gap. The noble gases are in between these fluids. By comparing the simulation data and taken into account numerical and estimation errors,all five working fluids are at par. Thus, the choice of the working fluid and the power cycle is an economical. While a hot gas air turbine is not as efficient as the steam turbine, the invest and maintenance costs are lower due to less heat exchangers and necessaries like water reconditioningand a phase separator.}, language = {en} } @inproceedings{OPUS4-1409, title = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) : 6th April 2021 - Kara, Togo : Conference Proceedings}, editor = {Reiff-Stephan, J{\"o}rg and Amouzou, Kou 'santa and Adanlete Adjanoh, Assiongbon}, publisher = {TIB Open Publishing}, address = {Hannover}, issn = {2748-8829}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14093}, year = {2021}, abstract = {Renewable energy sources are more important today than ever before, as they represent a key factor in reducing greenhouse emissions and fossil fuel consumption. Avoiding excessive burdens on future generations has now become the declared challenge of this century and justifies the efforts we must undertake to reduce global warming. This can only be achieved by conceiving new technical approaches, exploiting alternative resources and by raising people's awareness of the sustainable use of their own livelihoods. However, this change in awareness is a process that needs to be driven forward, especially in the field of research and education, and is therefore the declared aim of the Joint German-West African Conference on Sustainable, Renewable Energy Systems - SusRES. This annual conference provides a platform for exchange between scientists, students and many other interested parties, with technological progress at the forefront of the event. The SusRES conference is known as an accelerator for an ever-growing international network, not limited to the circumstances of a single country or even continent, which strives to take on and meet the global challenges of the present and future. This year's guiding theme of the event -Decentralized systems as a key factor in clean energy production for locations with limited infrastructure- of the event is primarily based on the consideration of how the energy supply of the future is to be designed. For some years now, a paradigm shift towards decentralised energy supply has been observed, which opens up new possibilities especially in areas with weak infrastructural supply. This is not just about providing energy from renewable resources, but also about exploiting this energy we have today efficiently and sustainably, whereby intelligent and interconnected systems play an ever-increasing role. The reader is provided with exciting insights into these topics within this conference proceedings elaborated by stakeholders from twelve time zones and four continents. In their contributions, the authors address important findings, especially from research but also from teaching, which represent an important milestone in their activities and thus make a significant contribution to our declared goals.}, language = {en} } @article{LukoseLiskerAkhtaretal.2021, author = {Lukose, R. and Lisker, Marco and Akhtar, Fatima and Fraschke, Mirko and Grabolla, T. and Mai, Andreas and Lukosius, Mindaugas}, title = {Influence of plasma treatment on SiO2/Si and Si3N4/Si substrates for large-scale transfer of graphene}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, issn = {2045-2322}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14179}, year = {2021}, abstract = {One of the limiting factors of graphene integration into electronic, photonic, or sensing devices is the unavailability of large-scale graphene directly grown on the isolators. Therefore, it is necessary to transfer graphene from the donor growth wafers onto the isolating target wafers. In the present research, graphene was transferred from the chemical vapor deposited 200 mm Germanium/Silicon (Ge/Si) wafers onto isolating (SiO2/Si and Si3N4/Si) wafers by electrochemical delamination procedure, employing poly(methylmethacrylate) as an intermediate support layer. In order to influence the adhesion properties of graphene, the wettability properties of the target substrates were investigated in this study. To increase the adhesion of the graphene on the isolating surfaces, they were pre-treated with oxygen plasma prior the transfer process of graphene. The wetting contact angle measurements revealed the increase of the hydrophilicity after surface interaction with oxygen plasma, leading to improved adhesion of the graphene on 200 mm target wafers and possible proof-of-concept development of graphene-based devices in standard Si technologies.}, language = {en} } @article{SteglichBondarenkoMaietal.2020, author = {Steglich, Patrick and Bondarenko, Siegfried and Mai, Christian and Paul, Martin and Weller, Michael G. and Mai, Andreas}, title = {CMOS-Compatible Silicon Photonic Sensor for Refractive Index Sensing Using Local Back-Side Release}, series = {IEEE Photonics Technology Letters}, volume = {32}, journal = {IEEE Photonics Technology Letters}, number = {19}, issn = {1941-0174}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13649}, pages = {1241 -- 1244}, year = {2020}, abstract = {Silicon photonic sensors are promising candidates for lab-on-a-chip solutions with versatile applications and scalable production prospects using complementary metal-oxide semiconductor (CMOS) fabrication methods. However, the widespread use has been hindered because the sensing area adjoins optical and electrical components making packaging and sensor handling challenging. In this work, a local back-side release of the photonic sensor is employed, enabling a separation of the sensing area from the rest of the chip. This approach allows preserving the compatibility of photonic integrated circuits in the front-end of line and metal interconnects in the back-end of line. The sensor is based on a micro-ring resonator and is fabricated on wafer-level using a CMOS technology. We revealed a ring resonator sensitivity for homogeneous sensing of 106 nm/RIU.}, language = {en} } @book{OPUS4-1806, title = {Electromagnetic Propagation and Waveguides in Photonics and Microwave Engineering}, editor = {Steglich, Patrick}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-83968-190-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18063}, publisher = {Technische Hochschule Wildau}, pages = {192}, year = {2020}, abstract = {Optical and microwave waveguides have attracted much research interest in both science and industry. The number of potential applications for their use is growing rapidly. This book examines recent advances in the broad field of waveguide technology. It covers current progress and latest breakthroughs in emergent applications in photonics and microwave engineering. The book includes ten contributions on recent developments in waveguide technologies including theory, simulation, and fabrication of novel waveguide concepts as well as reviews on recent advances.}, subject = {Wellenleiter}, language = {en} } @article{SopinskyyGrytsenkoVillringeretal.2023, author = {Sopinskyy, Mykola and Grytsenko, Kostyantyn and Villringer, Claus and Kolomzarov, Yurii and Schrader, Sigurd}, title = {Determination of scattering and Urbach absorption contributions to the light extinction in PTFE films by using graphical representation technique and numerical solution of the inverse problem}, series = {Semiconductor Physics, Quantum Electronics \& Optoelectronics}, volume = {26}, journal = {Semiconductor Physics, Quantum Electronics \& Optoelectronics}, number = {3}, publisher = {National Academy of Sciences of Ukraine. Institute for Semiconductor Physics}, address = {Kyiv}, issn = {1605-6582}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18035}, pages = {303 -- 314}, year = {2023}, abstract = {Ellipsometrically obtained spectral dependences of ordinary αxy and extra-ordinary αz extinction/attenuation coefficients within the spectral range λ = 300…980 nm of uniaxially anisotropic polytetrafluoroethylene (PTFE) films were analyzed. We considered the capabilities and specific features of the graphical representation technique for determining the contribution of Rayleigh scattering and Urbach absorption to light attenuation in the spectral range beyond fundamental absorption. It has been shown that the graphical approach enables to estimate these contributions qualitatively, semi-quantitatively or quantitatively, depending on the situation. The conclusions made using the analysis of graphical representation are confirmed by numerical solution of the inverse problem via simulation of the αxy (λ), αz (λ) experimental dependences within the framework of a best-fit procedure. Being based on both of these approaches, we have ascertained that, in the as-prepared PTFE films, the so-called anomalous light scattering (ALS) with the spectral dependence of scattering coefficient αs ≈ as λ-p (p > 4) takes place. Transformation of scattering from ALS to the Rayleigh one with p ≈ 4 due to annealing is accompanied by an increase of Urbach (subband) absorption. Both of these factors cause narrowing the dynamic range of extinction coefficient values. Both scattering and absorption coefficients are higher for the component of light polarized along the normal to the substrate as compared to the component polarized in parallel to it. The relationship between observed behavior of the scattering and absorption coefficients and the film structure has been discussed.}, language = {en} } @article{RoosHoqueKlimešovaetal.2023, author = {Roos, Andreas Hult and Hoque, Ziaul and Klimešov{\´a}, Eva and Ben Ltaief, Ltaief and Medina, Cristian and Jurkovič, Matej and Albrecht, Martin and Finke, Ondřej and Hort, Ondřej and Nejdl, Jaroslav and Mudrich, Marcel and Andreasson, Jakob and Krikunova, Maria}, title = {Electron correlation dynamics in atomic Kr excited by XUV pulses and controlled by NIR laser pulses of variable intensity}, series = {New Journal of Physics}, volume = {25}, journal = {New Journal of Physics}, publisher = {Institute of Physics Publishing (IOP)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16987}, year = {2023}, abstract = {We have investigated the possibility to track and control correlation dynamics of valence electrons in krypton (Kr) initiated by the absorption of one extreme ultraviolet (XUV) photon. In this investigation, pump-probe experiments have been performed where monochromatized single high-harmonics at photon energies 29.6, 32.8, and 35.9 eV have been used as pump to populate different intermediate excited states. A temporally delayed near-infrared (NIR) pulse probes the population of various decay channels via the detection of Kr²⁺ ion yields and its transient profiles. We observe that by varying the NIR pulse intensity within a range from 0.3 x 10¹³ to 2.6 x 10¹³ W cm⁻², the shape of the Kr²+ transient profile changes significantly. We show that by varying the intensity of the NIR pulse, it is possible—(i) to control the ratio between sequential and non-sequential double ionization of Kr; (ii) to selectively probe quantum beating oscillations between Kr+* satellite states that are coherently excited within the bandwidth of the XUV pulse; and (iii) to specifically probe the relaxation dynamics of doubly excited (Kr**) decay channels. Our studies show that the contribution of different ionization and decay channels (i)-(iii) can be altered by the NIR pulse intensity, thus demonstrating an efficient way to control the ionization dynamics in rare gas atoms.}, language = {en} } @inproceedings{SteglichMai2021, author = {Steglich, Patrick and Mai, Andreas}, title = {Analysis of BTO-on-Si-waveguides for energy-efficient electro-optical modulators}, series = {Proc. SPIE 11775, Integrated Optics: Design, Devices, Systems and Applications VI}, booktitle = {Proc. SPIE 11775, Integrated Optics: Design, Devices, Systems and Applications VI}, doi = {10.1117/12.2592501}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13934}, year = {2021}, abstract = {In this work, we analyze a horizontal slot waveguide configuration, which evaluates the potential for an integration of barium titanate (BTO) based modulators into a photonic integrated circuit (PIC) technology based on siliconon- insulator (SOI) wafer. The waveguide configuration consists of a doped crystal silicon layer, a Ba0:7Sr0:3TiO3 (BST) template layer, a barium titanate (BTO) layer and a doped poly-silicon layer on top. In contrast to current approaches, we analyze the performance of this waveguide-structure by using a vertical electrode configuration that is formed by the doped silicon layer. In this way, the electric field strength is dramatically increased compared to current horizontal electrode configuration.}, language = {en} } @article{YeshchenkoDmitrukGrytsenkoetal.2009, author = {Yeshchenko, Oleg A. and Dmitruk, Igor M. and Grytsenko, Kostyantyn and Prokopets, Vadym M. and Kotko, Andriy V. and Schrader, Sigurd}, title = {Influence of interparticle interaction on melting of gold nanoparticles in Au/polytetrafluoroethylene nanocomposites}, series = {Journal of Applied Physics}, volume = {105}, journal = {Journal of Applied Physics}, number = {9}, issn = {1089-7550}, doi = {10.1063/1.3125274}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9759}, year = {2009}, abstract = {The temperature dependence of the surface plasmon resonance energy and width in 5 nm spherical gold nanoparticles embedded in a polymer polytetrafluoroethylene matrix has been studied using absorption spectroscopy. The jumplike features have been observed in these dependences indicating the melting of gold nanoparticles at temperatures considerably lower than the bulk melting point. The interaction between gold nanoparticles sufficiently affects the melting of nanoparticles. The increase in the filling factor of the particles leads to a decrease in the melting temperature of gold nanoparticles.}, language = {en} } @book{OPUS4-1809, title = {Fiber Optics - From Fundamentals to Industrial Applications}, editor = {Steglich, Patrick and De Matteis, Fabio}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-83881-157-0}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18093}, publisher = {Technische Hochschule Wildau}, pages = {102}, year = {2019}, abstract = {Optical fibers in metrology, telecommunications, sensors, manufacturing, and health science have gained massive research interest. The number of applications is increasing at a fast pace. This book aims to present a collection of recent advances in fiber optics, addressing both fundamental and industrial applications. It covers the current progress and latest breakthroughs in emergent applications of fiber optics. The book includes five chapters on recent developments in optical fiber communications and fiber sensors, as well as the design, simulation, and fabrication of novel fiber concepts.}, language = {en} } @book{OPUS4-1808, title = {Plasmonic Nanostructures - Basic Concepts, Optimization and Applications}, editor = {Steglich, Patrick}, publisher = {IntechOpen}, address = {London}, isbn = {978-1-80356-004-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18084}, publisher = {Technische Hochschule Wildau}, pages = {126}, year = {2023}, abstract = {Plasmonics includes the fundamentals of surface plasmon polaritons in metals, and its rapidly increasing applications in biochemistry, nanotechnology, optical communication, sensing, and medicine. Surface plasmon polaritons have become popular because of their ultrasensitive optical measurement capabilities, and in recent years they have also been employed for ultra-high-speed data transfer. This book presents recent advances in the broad field of plasmonics, covering not only current progress and the latest breakthroughs in emergent applications but also geometry optimizations and the fundamentals of physical interactions.}, subject = {Plasmonik}, language = {en} } @article{BauerGutkeHeinrichetal.2020, author = {Bauer, Joachim and Gutke, Marko and Heinrich, Friedhelm and Edling, Matthias and Stoycheva, Vesela and Kaltenbach, Alexander and Burkhardt, Martin and Gruenefeld, Martin and Gamp, Matthias and Gerhard, Christoph and Steglich, Patrick and Steffen, Sebastian and Herzog, Michael and Dreyer, Christian and Schrader, Sigurd}, title = {Novel UV-transparent 2-component polyurethane resin for chip-on-board LED micro lenses}, series = {Optical Materials Express}, volume = {10}, journal = {Optical Materials Express}, number = {9}, issn = {2159-3930}, doi = {10.1364/OME.393844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13472}, pages = {2085 -- 2099}, year = {2020}, abstract = {In this work we present a novel optical polymer system based on polyurethane elastomer components, which combines excellent UV transparency with high thermal stability, good hardness, high surface tension and long pot life. The material looks very promising for encapsulation and microlensing applications for chip-on-board (CoB) light-emitting diodes (LED). The extinction coefficient k, refractive index n, and bandgap parameters were derived from transmission and reflection measurements in a wavelength range of 200-890 nm. Thermogravimetry and differential scanning calorimetry were used to provide glass transition and degradation temperatures. The surface tension was determined by means of contact angle measurements. As proof of concept, a commercial InGaN-CoB-LED is used to demonstrate the suitability of the new material for the production of microlenses.}, language = {en} } @article{GoldenbergKoehlerKahleetal.2020, author = {Goldenberg, Leonid and K{\"o}hler, Mathias and Kahle, Olaf and Dreyer, Christian}, title = {Impact of inorganic nanoparticles on optical properties of low refractive index waveguiding polymers}, series = {Optical Materials Express}, volume = {10}, journal = {Optical Materials Express}, number = {11}, issn = {2159-3930}, doi = {10.1364/OME.405700}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13521}, pages = {2987 -- 2997}, year = {2020}, abstract = {The objective of this work is to improve the optical properties of low refractive index polymers used for waveguide by introduction of inorganic nanoparticles. Copolymers of fluorinated monomers and glycidyl methacrylate are used. Introduction of SiO2 nanoparticles into polymer matrix is performed by direct mixing; copolymerization with SiO2 nanoparticles modified by monomer, and in situ sol-gel formation of SiO2 during photochemical cross-linking and annealing catalyzed by photoacid generator. It is demonstrated that nanoparticles are able to decrease thermo-optic coefficient. It is also possible to fabricate waveguiding layers by direct introduction of nanoparticles without compromising of optical propagation losses.}, language = {en} } @article{FelkeGrothHempeletal.2024, author = {Felke, Florens and Groth, Anne and Hempel, Martin and Czerny, Bernhard and Khatibi, Golta and D{\"o}hler, Torsten and Geißler, Ute}, title = {Effect of the loop forming process on the lifetime of aluminum heavy wire bonds under accelerated mechanical testing}, series = {Microelectronics Reliability}, volume = {154}, journal = {Microelectronics Reliability}, publisher = {Elsevier}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18631}, year = {2024}, abstract = {Heavy wire bonding is one of the most common interconnection technologies in manufacturing of high-power electronics. For industrial applications, the long-term reliability of these connections is crucial. Besides the selection of the wire material and the loop geometry itself, the loop forming process parameters also have an influence on the reliability of the wire bond. In this work, the influence of the backward bond head movement during wire bonding process on the quality of wire bond connections was systematically investigated and qualified by cyclic mechanical lifetime tests, surface roughness measurements of the heel area by laser confocal microscopy and static pull tests. The wire bond loops were fabricated with 300 μm aluminum H11 and H14CR wires with different hardness values. The lifetime at low frequency cycle and high frequency cycle regime was determined by means of two different mechanical cyclic test methods operating at 5 Hz and at 60 kHz respectively. The results have shown, that the surface topology of the heel region caused by the initial plastic deformation during the loop forming process has a significant effect on the wire bond failure due to heel cracking. The number of loading cycles to failure shows an inverse correlation with the degree of surface roughness in a so called wrinkling analysis in the low and high frequency cycle regime. The soft wire exhibits different lifetimes compared to the hard ones depending on the testing conditions, while a significant decrease of the lifetime is observed with >30 \% reverse movement during bonding in all cases.}, language = {en} } @inproceedings{SieversVillringerLebeketal.2023, author = {Sievers, Jan and Villringer, Claus and Lebek, Werner and Gilani, Taravat Saeb and Laufer, Jan}, title = {Photoacoustic tomography using a Fabry-Perot sensor with homogeneous optical thickness and wide-field camera-based detection}, series = {Opto-Acoustic Methods and Applications in Biophotonics VI}, booktitle = {Opto-Acoustic Methods and Applications in Biophotonics VI}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17850}, year = {2023}, abstract = {Fabry-Perot (FP) sensors are typically read out using a raster scan to acquire tomographic Photoacoustic (PA) images. To speed up the recording time, wide-field illumination of the sensor in combination with a camera as detector can be used. In this study, an sCMOS camera and wavelengths around 517 nm are used to interrogate a FP sensor with a homogeneous optical thickness over a 4 cm2 aperture. The recorded time series show PA signals are acquired over the entire area of the interrogation beam. The performance of the system, such as the noise equivalent pressure, is evaluated.}, language = {en} } @article{DubrovinskaiaDubrovinskyCrichtonetal.2005, author = {Dubrovinskaia, Natalia and Dubrovinsky, Leonid and Crichton, Wilson and Langenhorst, Falko and Richter, Asta}, title = {Aggregated diamond nanorods, the densest and least compressible form of carbon}, series = {Applied Physics Letters}, volume = {87}, journal = {Applied Physics Letters}, number = {8}, issn = {0003-6951}, doi = {10.1063/1.2034101}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5646}, year = {2005}, abstract = {We report the synthesis of aggregated diamondnanorods (ADNRs) from fullerene C60C60 at 20(1) GPa and 2200  °C using a multianvil apparatus. Individual diamond nanoroads are of 5-20 nm in diameter and longer than 1μm1μm. The x-ray and measured density of ADNRs is ∼0.2\%-0.4\%∼0.2\%-0.4\% higher than that of usual diamond. The extremely high isothermal bulk modulusKT=491(3)GPaKT=491(3)GPa [compare to KT=442(4)GPaKT=442(4)GPa of diamond] was obtained by in situx-ray diffraction study. Thus, ADNRs is the densest among all carbonmaterials and it has the lowest so far experimentally determined compressibility.}, language = {en} } @misc{BraeskeKlohsMirre2016, author = {Br{\"a}ske, J{\"o}rn and Klohs, Steffen and Mirre, Thomas}, title = {Untersuchung zum Ausfall der Strangf{\"u}hrungsrollen in der horizontalen Zone einer Brammenstranggussanlage}, series = {Wissenschaftliche Beitr{\"a}ge 2016}, volume = {20}, journal = {Wissenschaftliche Beitr{\"a}ge 2016}, issn = {0949-8214}, doi = {10.15771/0949-8214_2016_1_7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5346}, pages = {49 -- 58}, year = {2016}, abstract = {Es besteht ein Problem durch den h{\"a}ufigen Ausfall der Strangf{\"u}hrungsrollen und die resultierenden erheblichen Verluste durch den Produktionsausfall, welcher beim Ersetzen der Rolleneinheiten entsteht. Um die Ursachen zu ergr{\"u}nden wurden, zun{\"a}chst die Randbedingungen und das Schadensbild analysiert. Daraus entstand die Hypothese, dass allgemein eine zu hohe Temperaturbelastung f{\"u}r die Sch{\"a}digung der Lagerkomponenten verantwortlich ist und dies die grundlegende Ursache f{\"u}r die weitere Zerst{\"o}rung darstellt. Folglich musste eine Messeinrichtung installiert werden, um genauere Erkenntnisse {\"u}ber den {\"U}berhitzungsvorgang zu erlangen. Zu diesem Zweck wurden mehrere Verfahren zur Temperaturmessung miteinander verglichen, woraufhin eine Auswahl anhand einer Nutzwertanalyse erfolgte. Die Auswertung der gewonnenen Messdaten zeigte, dass die Charakteristik der aufgezeichneten {\"U}berhitzungen sehr variabel ist. Weiterhin konnte keine Abh{\"a}ngigkeit von einem Prozessparameter ermittelt werden. Die genauer betrachteten Vorg{\"a}nge konnten nicht oder nur eingeschr{\"a}nkt als Ursache f{\"u}r die {\"U}berhitzung nachgewiesen werden. Wenngleich somit weitere Untersuchungen erforderlich sind, wurden m{\"o}gliche Maßnahmen zur L{\"o}sung des Problems vorgeschlagen.}, language = {de} } @article{OuAnwandKoegleretal.2014, author = {Ou, Xin and Anwand, Wolfgang and K{\"o}gler, Reinhard and Zhou, Hong-Bo and Richter, Asta}, title = {The role of helium implantation induced vacancy defect on hardening of tungsten}, series = {Journal of Applied Physics}, volume = {115}, journal = {Journal of Applied Physics}, number = {12}, issn = {1089-7550}, doi = {10.1063/1.4870234}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5623}, year = {2014}, abstract = {Vacancy-type defects created by helium implantation in tungsten and their impact on the nano-hardness characteristics were investigated by correlating the results from the positron annihilation spectroscopy and the nano-indentation technique. Helium implantation was performed at room temperature (RT) and at an elevated temperate of 600 °C. Also, the effect of post-annealing of the RT implanted sample was studied. The S parameter characterizing the open volume in the material was found to increase after helium irradiation and is significantly enhanced for the samples thermally treated at 600 °C either by irradiation at high temperature or by post-annealing. Two types of helium-vacancy defects were detected after helium irradiation; small defects with high helium-to-vacancy ratio (low S parameter) for RT irradiation and large defects with low helium-to-vacancy ratio (high S parameter) for thermally treated tungsten. The hardness of the heat treated tungsten coincides with the S parameter, and hence is controlled by the large helium-vacancy defects. The hardness of tungsten irradiated at RT without thermal treatment is dominated by manufacturing related defects such as dislocation loops and impurity clusters and additionally by trapped He atoms from irradiation effects, which enhance hardness. He-stabilized dislocation loops mainly cause the very high hardness values in RT irradiated samples without post-annealing.}, language = {en} } @article{RoggeZinnProspositoetal.2017, author = {Rogge, Christian and Zinn, Steffen and Prosposito, Paolo and Francini, Roberto and Foitzik, Andreas}, title = {Transmitted light pH optode for small sample volumes}, series = {Journal of Sensors and Sensor Systems}, volume = {6}, journal = {Journal of Sensors and Sensor Systems}, number = {2}, issn = {2194-878X}, doi = {10.5194/jsss-6-351-2017}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10093}, pages = {351 -- 359}, year = {2017}, abstract = {An innovative concept of a low-cost pH optode with working volumes of less than 150 µL is presented. The pH monitoring is based on the color changing effect of pH indicators. The optode includes an RGB color sensor patch TCS34725 from Adafruit, a controllable LED and reactor slides and is addressed by a self-written LabVIEW© software. Utilizing the hue value of the HSV color model, it is possible to analyze the color change of the indicator and estimate the pH value of the analyzed samples by exploiting sigmoidal fit models. Measurements carried out with phenol red and DMEM (Dulbecco's Modified Eagle's Medium) reported a standard error of calibration in the physiologic pH range (6.5-7.5) of ±0.04 pH units.}, language = {en} } @article{MaierClausiusRichteretal.2021, author = {Maier, Petra and Clausius, Benjamin and Richter, Asta and Bittner, Benjamin and Hort, Norbert and Menze, Roman}, title = {Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness}, series = {Materials}, volume = {14}, journal = {Materials}, number = {13}, publisher = {MDPI}, issn = {1996-1944}, doi = {10.3390/ma14133686}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14194}, year = {2021}, abstract = {The investigation of the crack propagation in as-extruded and heat-treated Mg-Dy-Nd-Zn-Zr alloy with a focus on the interaction of long-period stacking-ordered (LPSO) structures is the aim of this study. Solution heat treatment on a hot extruded Mg-Dy-Nd-Zn-Zr (RESOLOY®) was done to change the initial fine-grained microstructure, consisting of grain boundary blocky LPSO and lamellar LPSO structures within the matrix, into coarser grains of less lamellar and blocky LPSO phases. C-ring compression tests in Ringer solution were used to cause a fracture. Crack initiation and propagation is influenced by twin boundaries and LPSO lamellae. The blocky LPSO phases also clearly hinder crack growth, by increasing the energy to pass either through the phase or along its interface. The microstructural features were characterized by micro- and nanohardness as well as the amount and location of LPSO phases in dependence on the heat treatment condition. By applying nanoindentation, blocky LPSO phases show a higher hardness than the grains with or without lamellar LPSO phases and their hardness decreases with heat treatment time. On the other hand, the matrix increases in hardness by solid solution strengthening. The microstructure consisting of a good balance of grain size, matrix and blocky LPSO phases and twins shows the highest fracture energy.}, language = {en} } @article{SmithChristopherKennyetal.2003, author = {Smith, Roger and Christopher, D. and Kenny, S. D. and Richter, Asta and Wolf, Bodo}, title = {Defect generation and pileup of atoms during nanoindentation of Fe single crystals}, series = {Physical Review B}, volume = {67}, journal = {Physical Review B}, number = {24}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14855}, year = {2003}, abstract = {Complementary large scale molecular-dynamics simulations and experiments have been carried out to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe {110}, {100}, and {111}. The defect formation and motion causes the complex mechanisms of plastic and elastic deformation which is reflected in the pileup patterns. The experimental results show distinct patterns of pileup material which are dependent on the individual crystal faces and the superposition of the stress field of the indenter. The highest pileup around the indenter hole occurs on the {100} surface and the shallowest on {111}. The least symmetric surface is {110} which produces an experimental pileup pattern displaying only twofold symmetry with the axially symmetric indenter. The pyramidal indenter produces an asymmetric pattern which changes as the crystal is rotated with respect to the tip but repeats with threefold rotational symmetry. Material displacement occurs primarily in planes of the {110} family. Pileup is formed by cross slip between planes of the same family which intersect in ⟨111⟩ directions. For the {110} surface, dislocation loops propagate in the four in-plane ⟨111⟩ directions and the two inclined ⟨111⟩ directions. The loops that propagate in the in-plane directions are terminated by edge dislocations at the surface. These transport material away from the tip but cannot produce pileup. The loops that propagate in the inclined direction cross slip and cause the observed pileup. The {100} surface has fourfold rotational symmetry and all the ⟨111⟩ directions are inclined. The dislocation loops propagate in these directions and cross slip readily occurs, leading to a large pileup. The {111} face shows the least pileup which is more spread out over the surface. In this case the dislocation loops propagate in shallow slip planes and do not readily cross slip. Experimentally determined force-depth curves show distinct "pop-ins" which correspond to the formation of dislocations. The contact pressure (nanohardness) is not a constant and increases with decreasing indentation depth. It also changes with crystal face. Calculated force-depth curves match the experimental trend but give estimates of the nanohardness and Young's modulus higher than those values experimentally determined.}, language = {en} } @article{GerhardDobis2021, author = {Gerhard, Christoph and Dobis, Alexander}, title = {Manufacturing-induced surface contaminations}, series = {Vakuum in Forschung und Praxis}, volume = {33}, journal = {Vakuum in Forschung und Praxis}, number = {1}, publisher = {Wiley}, doi = {https://doi.org/10.1002/vipr.202100752}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15656}, pages = {33 -- 37}, year = {2021}, abstract = {Summary In the course of classical optics manufacturing glass components are in permanent direct contact with aqueous operating materials. Such contact leads to a certain absorption of water and hydrogenous compounds that may induce severe glass defects. In this contribution, absorption of hydrogen and other contaminants during grinding of glass was observed and qualitatively detected via laser-induced breakdown spectroscopy. It is shown that hydrogen, calcium, magnesium, and carbon are implanted into the glass surface where the contaminant concentration increases over grinding time or contact time of the glass surface with water and the grinding tool, respectively. The contaminants hydrogen, calcium, and magnesium can be attributed to the water used as lubricant. In contrast, carbon most likely originates from wear debris of the used silicon carbide grinding pads. Several possible mechanisms that lead to such surface contamination of glasses during grinding - diffusion, accumulation in micro cracks as well as the formation of hydrated silica - are finally introduced.}, language = {en} } @article{TarabrinBushunovTeslenkoetal.2021, author = {Tarabrin, Mikhail K. and Bushunov, Andrey A. and Teslenko, Andrei A. and Sakharova, Tatiana and Hinkel, Jonas and Usenov, Iskander and D{\"o}hler, Torsten and Geißler, Ute and Artyushenko, Viacheslav and Lazarev, Vladimir A.}, title = {Fabrication of an antireflection microstructure on AgClBr polycrystalline fiber by single pulse femtosecond laser ablation}, series = {Optical Materials Express}, volume = {11}, journal = {Optical Materials Express}, number = {2}, publisher = {Optical Society of America}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15384}, pages = {487 -- 496}, year = {2021}, abstract = {Polycrystalline infrared (PIR) fibers are used for numerous applications, one of those being power delivery for CO2 lasers. However, the fiber tip surface's transmittance cannot be increased with conventional antireflection coatings due to the surface unevenness. Antireflection microstructures (ARMs) offer an alternative way of increasing transmittance. In this work, ARMs were fabricated on the fiber tip surface of an AgClBr fiber by single-pulse femtosecond laser ablation. A single-surface transmittance of 92.8\% at 10.6 μm, a CO2 laser operation wavelength, was achieved. The proposed method can help significantly improve the systems' efficiency, where power delivery for CO2 lasers or sources operating in the wide wavelength range is required.}, language = {en} } @inproceedings{DietrichvandeSandReiffStephan2021, author = {Dietrich, Alexander and van de Sand, Ron and Reiff-Stephan, J{\"o}rg}, title = {Implementation of a Machine Tool Retrofit System}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15004}, pages = {239 -- 247}, year = {2021}, abstract = {Small and medium-sized companies increasingly turning their attention towards the fourth industrial revolution. In order to increase their own long-term competitiveness, there is a growing desire to make production smarter, more efficient, safer and more sustainable through new technologies. Often, however, existing plants cannot be easily replaced by modern equipment. The reasons for this can be high investment costs, excessive downtimes or the unavailability of an equivalent machine. An alternative solution to the purchase of new equipment is the modernisation or expansion of existing systems, also called retrofitting. Thus, this paper deals with the retrofit process of a machine tool, whereby the software architecture of the control unit is the primary concern of this work.}, language = {en} } @inproceedings{GieseReiffStephan2021, author = {Giese, Lutz B. and Reiff-Stephan, J{\"o}rg}, title = {Hydrogen and Usability of Hydrogen Storage Technologies}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14937}, pages = {97 -- 106}, year = {2021}, abstract = {Science, technology and politics agree: hydrogen will be the energy carrier of the future. It will replace fossil fuels based on a sufficient supply from sustainable energy. Since the possibilities of storing and transporting hydrogen play a decisive role here, the so-called LOHC (Liquid Organic Hydrogen Carriers) can be used as carrier materials. LOHC carrier materials can reversibly absorb hydrogen, store it without loss and release it again when needed. Since little or no pressure is required, normal containers or tanks can be used. The volume or mass-related energy densities can reach around a quarter of liquid fossil fuels. This paper is to give an introduction to the field of hydrogen storage and usage of those LOHC, in particular. The developments of the last ten years have been related to the storage and transport of hydrogen with LOHC. These are crucial to meet the future demand for energy carriers e.g. for mobile applications. For this purpose, all transport systems are under consideration as well as the decentralized supply of rural areas with low technological penetration, e.g. regions of Western Africa which are often characterized by a lack of energy supply. Hydrogen bound in LOHC can provide a hazard-free alternative for distribution. The paper provides an overview of the conversion forms as well as the chemical carrier materials. Dibenzyltoluene as well as N-ethylcarbazole - as examples for LOHC - are discussed as well as chemical hydrogen storage materials like ammonia boranes as alternatives to LOHC.}, language = {en} } @inproceedings{vandeSandCorasanitiReiffStephan2021, author = {van de Sand, Ron and Corasaniti, Sandra and Reiff-Stephan, J{\"o}rg}, title = {Positive-Unlabelled Learning based Novelty Detection for Industrial Chillers}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, volume = {1}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14965}, pages = {155 -- 164}, year = {2021}, abstract = {Chiller systems are used in many different applications in both the industrial and the commercial sector. They are considered major energy consumers and thus contribute a non-negligible factor to environmental pollution as well as to the overall operating cost. In addition, chillers, especially in industrial applications, are often associated with high reliability requirements, as unplanned system downtimes are usually costly. As many studies over the past decades have shown, the presence of faults can lead to significant performance degradation and thus higher energy consumption of these systems. Thus, data-driven fault detection plays an ever-increasing role in terms of energy efficient control strategies. However, labelled data to train associated algorithms are often only available to a limited extent, which consequently inhibits the broad application of such technologies. Therefore, this paper presents an approach that exploits only a small amount of labelled and large amounts of unlabelled data in the training phase in order to detect fault related anomalies. For this, the model utilizes the residual space of the data transformed through principal component analyses in conjunction with a biased support vector machine, which can be ascribed to the concept of semi-supervised learning, or more specifically, positive-unlabelled learning.}, language = {en} } @inproceedings{FalkvandeSandCorasanitietal.2021, author = {Falk, Constantin and van de Sand, Ron and Corasaniti, Sandra and Reiff-Stephan, J{\"o}rg}, title = {A Comparison Study of Data-Driven Anomaly Detection Approaches for Industrial Chillers}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14970}, pages = {165 -- 174}, year = {2021}, abstract = {Faults in industrial chiller systems can lead to higher energy consumption, increasing wear of system components and shorten equipment life. While they gradually cause anomalous system operating conditions, modern automatic fault detection models aim to detect them at low severity by using real-time sensor data. Many scientific contributions addressed this topic in the past and presented data-driven approaches to detect faulty system states. Although many promising results were presented to date, there is lack of suitable comparison studies that show the effectiveness of the proposed models by use of data stemming from different chiller systems. Therefore this study aims at detecting a suitable data-driven approach to detect faults reliable in different domains of industrial chillers. Thus, a unified procedure is developed, to train all algorithms in an identical way with same data-basis. Since most of the reviewed papers used only one dataset for training and testing, the selected approaches are trained and validated on two different datasets from real refrigeration systems. The data-driven approaches are evaluated based on their accuracy and true negative rate, from which the most suitable approach is derived as a conclusion.}, language = {en} } @unpublished{SteglichRabusSadaetal.2021, author = {Steglich, Patrick and Rabus, Dominik G. and Sada, Cinzia and Paul, Martin and Weller, Michael G. and Mai, Christian and Mai, Andreas}, title = {Silicon Photonic Micro-Ring Resonators for Chemical and Biological Sensing: A Tutorial}, series = {TechRxiv}, journal = {TechRxiv}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16840}, year = {2021}, abstract = {Silicon photonic micro-ring resonators (MRR) developed on the silicon-on-insulator (SOI) platform, owing to their high sensitivity and small footprint, show great potential for many chemical and biological sensing applications such as label-free detection in environmental monitoring, biomedical engineering, and food analysis. In this tutorial, we provide the theoretical background and give design guidelines for SOI-based MRR as well as examples of surface functionalization procedures for label-free detection of molecules. After introducing the advantages and perspectives of MRR, fundamentals of MRR are described in detail, followed by an introduction to the fabrication methods, which are based on a complementary metal-oxide semiconductor (CMOS) technology. Optimization of MRR for chemical and biological sensing is provided, with special emphasis on the optimization of waveguide geometry. At this point, the difference between chemical bulk sensing and label-free surface sensing is explained, and definitions like waveguide sensitivity, ring sensitivity, overall sensitivity as well as the limit of detection (LoD) of MRR are introduced. Further, we show and explain chemical bulk sensing of sodium chloride (NaCl) in water and provide a recipe for label-free surface sensing.}, language = {en} } @article{AlberAssfalgNayerietal.2022, author = {Alber, J and Assfalg, L and Nayeri, C N and Paschereit, C O and Lahr, Markus and Semmler, L and Twele, J and Fortmann, J and Fischer, J and Latoufis, K and Dorn, I}, title = {3D printed rotor blades for a research wind turbine: Aerodynamic and structural design and testing}, series = {Journal of Physics: Conference Series}, volume = {2265}, journal = {Journal of Physics: Conference Series}, publisher = {Institute of Physics Publishing (IOP)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16314}, year = {2022}, abstract = {This study combines the design, the 3D printing and the testing of a small 3-bladed wind turbine rotor for research and teaching purposes. The objective is the additive manufacturing of a rotor with a radius of one meter, as an alternative to subtractive methods, such as computerized milling. The blade design is developed using freely available software packages. The aerodynamic considerations include the airfoil selection, the calculation of the blade geometry and the simulation of the ultimate load cases. The structural considerations are focussed on the printable materials, the infill structures and the retrofit of a load-carrying spar. The rotor blades are 3D printed with the BigRep One at the maker space of the TH Wildau. The structural integrity of the prototype blade is tested in terms of the ultimate root bending moments and the centrifugal forces at the HTW Berlin. The aerodynamic run-up tests are performed at the large wind tunnel of the TU Berlin measuring the power curves. The successful prototype paves the way for follow-up projects, such as open field tests and the 3D printing of larger rotor blades.}, language = {en} } @article{HermannGrojoAxenteetal.2017, author = {Hermann, J{\"o}rg and Grojo, David and Axente, Emanuel and Gerhard, Christoph and Burger, Miloš and Craciun, Valentin}, title = {Ideal radiation source for plasma spectroscopy generated by laser ablation}, series = {Physical Review E}, volume = {96}, journal = {Physical Review E}, number = {5}, publisher = {American Physical Society (APS)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16132}, year = {2017}, abstract = {Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.}, language = {en} } @misc{GerhardLetienCressentetal.2019, author = {Gerhard, Christoph and Letien, Emilie and Cressent, Thomas and Hofmann, Mandy}, title = {Impact of the plasma power on plasma-induced increase in absorption of fused silica}, series = {Wissenschaftliche Beitr{\"a}ge 2019}, volume = {23}, journal = {Wissenschaftliche Beitr{\"a}ge 2019}, issn = {0949-8214}, doi = {10.15771/0949-8214_2019_5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10802}, pages = {33 -- 37}, year = {2019}, abstract = {In the last decades, laser machining of fused silica has gained in importance where the main challenge is to overcome the high transmission of this medium in order to achieve surface absorption. One approach is plasma treatment using hydrogenous process gases. In doing so, a near-surface glass layer is chemically modified by a removal of oxygen and an implantation of hydrogen, resulting in the formation of optically active defects and an increase in absorption. Against this background, the impact of the plasma power on plasma-induced increase in absorption of fused silica was investigated in the present work. Here, the highest efficiency of the plasma treatment process was found at the lowest applied plasma power whereas for higher plasma powers, a notably lower increase in absorption was observed. This effect is attributed to the decomposition of plasma species required for initiating the formation of optically active defects within the glass. Such decomposition increases with rising power due to the corresponding increase in electric field strength within the plasma. This finding is of substantial interest for an extensive understanding of plasma-glass interactions.}, language = {en} } @inproceedings{PrelipceanuCojocariuGrauretal.2015, author = {Prelipceanu, Marius and Cojocariu, Lucian and Graur, Adrian and Schrader, Sigurd}, title = {Analysis of thermally stimulated processes in new phenanthroline derivatives suitable for optoelectronic devices}, series = {Journal of Physics: Conference Series (JPCONF)}, volume = {585}, booktitle = {Journal of Physics: Conference Series (JPCONF)}, issn = {1742-6596}, doi = {10.1088/1742-6596/585/1/012011}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12050}, year = {2015}, abstract = {Thermally stimulated processes have been studied in thin films of phenanthroline derives to describe the states that had been localized. Ultraviolet Photoelectron Spectroscopy had checked out before thin films of new pyrrolo[l,2-a][l,10] phenanthroline derivatives [1], in order to further applications in optoelectronic devices. The investigated compounds have an electronic band structure which is due to the substituent (R=NO2, Cl) induced transformations of molecular orbitals. Thermally stimulated discharge currents (TSDC) attested dipolar and charge transport mechanisms. Each TSDC peak has been assigned to elementary processes that are different utilizing in addition dielectric spectroscopy (DES), and the mean trap depths have been approximated from thermally stimulated luminescence (TSL) curves.}, language = {en} } @article{KsianzouVelagapudiGrimmetal.2006, author = {Ksianzou, Viachaslau and Velagapudi, R. K. and Grimm, Bernd and Schrader, Sigurd}, title = {Polarization-dependent optical characterization of poly(phenylquinoxaline) thin films}, series = {Journal of Applied Physics}, volume = {100}, journal = {Journal of Applied Physics}, number = {6}, issn = {1089-7550}, doi = {10.1063/1.2349471}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9761}, year = {2006}, abstract = {Linear optical properties of two types of poly(phenylquinoxaline) (PPQ) are studied by multiwavelength prism coupling technique and optical absorption spectroscopy. Surface roughness measurements are done using atomic force microscopy. PPQs form smooth films of high optical quality having refractive indices above 1.7 in the visible and near infrared spectral ranges. Enhanced birefringence of Δn∼0.04Δn∼0.04 has been observed in both PPQ films prepared by spin coating. Sellmeier coefficients are derived for the wavelength range starting from 0.532to1.064μm0.532to1.064μm for both TE and TM polarizations. Quantum chemical calculations both on the semiempirical and on the ab initio level are carried out in order to calculate the first-order molecular polarizability tensors of the polymer repeat units. From the obtained tensor elements, theoretical values for both the average refractive indices and the maximum expectable birefringence are calculated. Based on these values a more detailed interpretation of the experimental findings is carried out. The dispersion of refractive index is quantified by the value of Abbe's constant (νd)(νd). In our case the value νd≈11νd≈11 indicates high dispersion in the visible spectral range. The imaginary part kk of the complex refractive index n∗=n-ikn*=n-ik reaches values of k⩽10-3k⩽10-3 in the wavelength range from 0.5to1μm0.5to1μm.}, language = {en} } @article{MinaevJanssonAgrenetal.2006, author = {Minaev, Boris and Jansson, Emil and {\AA}gren, Hans and Schrader, Sigurd}, title = {Theoretical study of phosphorescence in dye doped light emitting diodes}, series = {The Journal of Chemical Physics}, volume = {125}, journal = {The Journal of Chemical Physics}, number = {23}, issn = {1089-7690}, doi = {10.1063/1.2388263}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9775}, year = {2006}, abstract = {Phosphorescence of platinum(II) octaethyl porphyrin (PtOEP), which has been used in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons, is studied by time-dependent (TD) density functional theory (DFT).}, language = {en} } @article{GerhardGimpelTascheetal.2018, author = {Gerhard, Christoph and Gimpel, Thomas and Tasche, Daniel and Koch, Jennifer and Br{\"u}ckner, Stephan and Flachenecker, G{\"u}nter and Wieneke, Stephan and Schade, Wolfgang and Vi{\"o}l, Wolfgang}, title = {Atmospheric pressure plasma-assisted femtosecond laser engraving of aluminium}, series = {Journal of Physics D: Applied Physics}, volume = {51}, journal = {Journal of Physics D: Applied Physics}, issn = {1361-6463}, doi = {10.1088/1361-6463/aab6e6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10521}, pages = {1 -- 7}, year = {2018}, abstract = {In this contribution, we report on the impact of direct dielectric barrier discharge argon plasma at atmospheric pressure on femtosecond laser engraving of aluminium. It is shown that the assisting plasma strongly affects the surface geometry and formation of spikes of both laser-engraved single lines and patterns of adjacent lines with an appropriate overlap. Further, it was observed that the overall ablation depth is significantly increased in case of large-scale patterning whereas no notable differences in ablation depth are found for single lines. Several possible mechanisms and underlying effects of this behaviour are suggested. The increase in ablation depth is supposed to be due to a plasma-induced removal of debris particles from the cutting point via charging and oxidation as supported by EDX analysis of the re-solidified debris. Furthermore, the impact of a higher degree of surface wrinkling as well as direct interactions of plasma species with the aluminium surface on the ablation process are discussed.}, language = {en} } @article{GerhardStappenbeck2018, author = {Gerhard, Christoph and Stappenbeck, Marco}, title = {Impact of the Polishing Suspension Concentration on Laser Damage of Classically Manufactured and Plasma Post-Processed Zinc Crown Glass Surfaces}, series = {Applied Sciences}, volume = {8}, journal = {Applied Sciences}, number = {9}, publisher = {MDPI}, issn = {2076-3417}, doi = {10.3390/app8091556}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10556}, pages = {1 -- 15}, year = {2018}, abstract = {The laser-induced damage threshold of optics is an issue of essential importance in high-power laser applications. However, the complex and partially interacting mechanisms as well as the underlying reasons for laser damage of glass surfaces are not yet fully understood. The aim of the present work is to contribute to a better understanding of such damage mechanisms by providing original results on the impact of classical glass surface machining on the laser-induced damage threshold. For this purpose, glass samples were prepared with well-defined process conditions in terms of the used lapping and polishing agents and suspensions. Further, the samples were post-processed by atmospheric pressure plasma for precision cleaning. The laser-induced damage threshold and surface contamination by residues from the manufacturing process were determined before and after plasma post-processing. It is shown that the polishing suspension concentration has a certain impact on the laser-induced damage threshold and surface contamination by residues from used working materials. The highest damage threshold of 15.2 J/cm² is found for the lowest surface contamination by carbon which occurs in the case of the highest polishing suspension concentration. After plasma treatment for merely 60 s, this value was increased to 20.3 J/cm² due to the removal of surface-adherent carbon. The results thus imply that the laser-induced damage threshold can notably be increased by first choosing appropriate process parameters during classical manufacturing and second plasma post-processing for surface finishing.}, language = {en} } @article{SchulzeWehrholdHille2018, author = {Schulze, Sven and Wehrhold, Michel and Hille, Carsten}, title = {Femtosecond-Pulsed Laser Written and Etched Fiber Bragg Gratings for Fiber-Optical Biosensing}, series = {Sensors}, volume = {18}, journal = {Sensors}, number = {9}, issn = {1424-8220}, doi = {10.3390/s18092844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10570}, pages = {1 -- 20}, year = {2018}, abstract = {We present the development of a label-free, highly sensitive fiber-optical biosensor for online detection and quantification of biomolecules. Here, the advantages of etched fiber Bragg gratings (eFBG) were used, since they induce a narrowband Bragg wavelength peak in the reflection operation mode. The gratings were fabricated point-by-point via a nonlinear absorption process of a highly focused femtosecond-pulsed laser, without the need of prior coating removal or specific fiber doping. The sensitivity of the Bragg wavelength peak to the surrounding refractive index (SRI), as needed for biochemical sensing, was realized by fiber cladding removal using hydrofluoric acid etching. For evaluation of biosensing capabilities, eFBG fibers were biofunctionalized with a single-stranded DNA aptamer specific for binding the C-reactive protein (CRP). Thus, the CRP-sensitive eFBG fiber-optical biosensor showed a very low limit of detection of 0.82 pg/L, with a dynamic range of CRP detection from approximately 0.8 pg/L to 1.2 µg/L. The biosensor showed a high specificity to CRP even in the presence of interfering substances. These results suggest that the proposed biosensor is capable for quantification of CRP from trace amounts of clinical samples. In addition, the adaption of this eFBG fiber-optical biosensor for detection of other relevant analytes can be easily realized.}, language = {en} } @misc{SteglichVillringerPulweretal.2017, author = {Steglich, Patrick and Villringer, Claus and Pulwer, Silvio and Dietzel, Birgit and Ksianzou, Viachaslau and Schrader, Sigurd}, title = {Chip-integrierte photonische Bauelemente}, series = {Wissenschaftliche Beitr{\"a}ge 2017}, volume = {21}, journal = {Wissenschaftliche Beitr{\"a}ge 2017}, issn = {0949-8214}, doi = {10.15771/0949-8214_2017_7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9426}, pages = {55 -- 59}, year = {2017}, abstract = {In unserer hochtechnologisierten Gesellschaft spielt die optische Daten{\"u}bertragung aufgrund der stetig wachsenden Informationsvielfalt eine immer bedeutendere Rolle. In den Anf{\"a}ngen der Nachrichtentechnik waren Datenraten von wenigen bit/s realisierbar. Heute werden mittels optischer Technologien {\"U}bertragungsraten von mehreren Gbit/s umgesetzt. M{\"o}glich wird dies durch neue Entwicklungen in der Chip-integrierten Photonik. Beispiele daf{\"u}r sind Chip-integrierte elektrooptische Modulatoren und Schalter. In diesem Artikel werden neue Entwicklungen in der Chip-integrierten Photonik diskutiert und die experimentelle Charakterisierung der Bauelemente in Form eines Ringresonators beschrieben. F{\"u}r die Experimente wird exemplarisch ein photonisches Bauelement genutzt, das aus einem hybriden Silizium-Polymer-Materialsystem besteht. Die Ergebnisse zeigen, dass diese Materialkombination vielversprechend f{\"u}r zuk{\"u}nftige Chip-integrierte photonische Bauelemente mit extrem geringem Energiebedarf ist.}, language = {de} } @misc{SteglichKsianzouVillringeretal.2018, author = {Steglich, Patrick and Ksianzou, Viachaslau and Villringer, Claus and Pulwer, Silvio and Schrader, Sigurd}, title = {Theorie der Modenlinienspektroskopie zur optischen Charakterisierung von Polymerschichten}, series = {Wissenschaftliche Beitr{\"a}ge 2018}, volume = {22}, journal = {Wissenschaftliche Beitr{\"a}ge 2018}, issn = {0949-8214}, doi = {10.15771/0949-8214_2018_4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10248}, pages = {31 -- 38}, year = {2018}, abstract = {Die Modenlinienspektroskopie kann zur hochpr{\"a}zisen Charakterisierung von Polymerschichten bez{\"u}glich des Brechungsindex verwendet werden. Das vorliegende Manuskript behandelt die Theorie der Modenlinienspektroskopie und beginnt dabei mit den theoretischen Grundlagen eines planaren Wellenleiters, die zum Verst{\"a}ndnis der Modenlinienspektroskopie notwendig sind. Die hier pr{\"a}sentierten expliziten Herleitungen k{\"o}nnen genutzt werden, um die Modenlinienspektroskopie so zu modifizieren, dass auch die Messung des Pockelseffektes m{\"o}glich ist. Eine Anwendungsm{\"o}glichkeit soll in der zuk{\"u}nftigen Bestimmung des Pockelskoeffizienten bestehen, der f{\"u}r die Weiterentwicklung von polymerbasierten elektrooptischen Modulatoren ben{\"o}tigt wird. Zudem werden der Aufbau und die experimentelle Herangehensweisen beschrieben und die Brechungsindexbestimmung wird exemplarisch am Beispiel einer Wirt-Gast-Polymerschicht demonstriert.}, language = {de} } @misc{RaguschJergovićGieseetal.2018, author = {Ragusch, Denny and Jergović, Michael and Giese, Lutz B. and Rolle, Siegfried}, title = {Einsatz der Brennstoffzelle als Netzersatzanlage sicherheitsrelevanter Digitalfunkstationen im Feldtest}, series = {Wissenschaftliche Beitr{\"a}ge 2018}, volume = {22}, journal = {Wissenschaftliche Beitr{\"a}ge 2018}, issn = {0949-8214}, doi = {10.15771/0949-8214_2018_5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10251}, pages = {39 -- 45}, year = {2018}, abstract = {Es wird anhand des F{\"o}rderprojekts „Wasserstoff-Netzersatzanlagen der Beh{\"o}rden und Organisationen mit Sicherheitsaufgaben (BOS) des Landes Brandenburg" des Zentraldienstes der Polizei des Landes Brandenburg die Praxistauglichkeit von Brennstoffzellen-Netzersatzanlagen untersucht. Marktreife und kommerziell verf{\"u}gbare Brennstoffzellen wurden in 115 sicherheitsrelevanten Digitalfunkstationen im Fl{\"a}chenland Brandenburg als Ersatz von wartungsintensiven und umweltproblematischen Dieselgeneratoren f{\"u}r die (Not-)Stromversorgung installiert. Diese Netzersatzanlagen sind f{\"u}r eine {\"U}berbr{\"u}ckungszeit von 72 h unter realen Bedingungen ausgelegt und wurden im Feldtest, parallel zum realen Betrieb, {\"u}ber einen l{\"a}ngeren Einsatzzeitraum (ca. 2 Jahre) auf ihre Zuverl{\"a}ssigkeit und Verf{\"u}gbarkeit hin untersucht. Die Anforderungen an und die Realisierung der Brennstoffzellen-Netzersatzanlagen sowie die Feldtest-Versuchsplanung und deren Ergebnisse werden beschrieben und diskutiert. Die Praxistauglichkeit wird mit einer hohen Verf{\"u}gbarkeit {\"u}ber 97 \% und einer Funktionszuverl{\"a}ssigkeit von mehr als 95 \% erfolgreich best{\"a}tigt. Die Entwicklung weiterer Komponenten wird empfohlen.}, language = {de} } @misc{Krechlok1996, author = {Krechlok, Kurt}, title = {Struktur und Zwanglauf bei mechanischen Getrieben}, series = {Wissenschaftliche Beitr{\"a}ge 1/1996}, volume = {2}, journal = {Wissenschaftliche Beitr{\"a}ge 1/1996}, number = {1}, issn = {0949-8214}, doi = {10.15771/0949-8214_1996_11}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-8213}, pages = {54 -- 56}, year = {1996}, abstract = {In vielen Maschinen und Ger{\"a}ten bilden komplexe Bewegungsabl{\"a}ufe einzelner Arbeitsorgane und deren Zusammenspiel das Kernst{\"u}ck f{\"u}r die Erf{\"u}llung der geforderten technischen Funktion. Die technisch-wirtschaftlich optimale Realisierung von Bewegungsabl{\"a}ufen und die Beherrschung ihrer Dynamik sind damit oft entscheidende Voraussetzungen f{\"u}r den Erfolg des Gesamtproduktes. Typische Beispiele daf{\"u}r sind Maschinen zur Herstellung und Verarbeitung von Textilien, Druck- und Papiermaschinen, Verpackungsmaschinen aller Art sowie Handhabungseinrichtungen, F{\"o}rdereinrichtungen und Industrieroboter. Zur mechanischen L{\"o}sung solcher Bewegungsaufgaben dienen die ungleichm{\"a}ßig {\"u}bersetzenden Kurven- und Gelenkgetriebe, die in vielf{\"a}ltigen Bauformen und Kombinationen mit oft geringem Aufwand sicher und zuverl{\"a}ssig pr{\"a}zise Bewegungsabl{\"a}ufe erzeugen, und das auch bei hohen Geschwindigkeiten und Kr{\"a}ften. In nachfolgenden Ausf{\"u}hrungen sollen einige Zusammenh{\"a}nge zwischen der Getriebestruktur und dem zwangsl{\"a}ufigen Bewegungsablauf mechanischer Getriebe beschrieben werden.}, language = {de} } @misc{GuendelVolkmann1996, author = {G{\"u}ndel, Harald and Volkmann, Hans}, title = {Eximerlaser mit gauß-f{\"o}rmigem Strahlprofil}, series = {Wissenschaftliche Beitr{\"a}ge 1/1996}, volume = {2}, journal = {Wissenschaftliche Beitr{\"a}ge 1/1996}, number = {1}, issn = {0949-8214}, doi = {10.15771/0949-8214_1996_14}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-8245}, pages = {68 -- 71}, year = {1996}, abstract = {Wegen ihrer Wellenl{\"a}nge im ultravioletten Spektralgebiet geh{\"o}ren Eximerlaser (z. B. KrF, ArF, XeCI) zu den am vielseitigsten eingesetzten Lasern in der Forschung und zunehmend auch in der industriellen Anwendung. Alle am Markt erh{\"a}ltlichen Excimer-Laser weisen jedoch einen wesentlichen Nachteil auf, der ihre Einsatzm{\"o}glichkeiten begrenzt. Bedingt durch konstruktive Besonderheiten ist ihre Strahlqualit{\"a}t unbefriedigend. Sie weisen einen rechteckf{\"o}rmigen Strahlquerschnitt auf mit einem komplizierten Gemisch verschiedener transversaler Moden (Multimodenstruktur). Diese Eigenschaft wirkt sich negativ auf die Fokussierbarkeit der Strahlung aus, wodurch der positive Einfluß der kurzen Wellenl{\"a}ngen z.T. wieder zunichte gemacht wird. Besonders st{\"o}rend ist dieser Effekt z. B. beim Bohren feinster L{\"o}cher oder beim Einkoppeln der Strahlung in Lichtleiter. Das Ziel der Arbeiten besteht daher darin, einen Eximerlaser zu entwickeln, der die Vorteile der kurzen Wellenl{\"a}nge mit einer guten Strahlqualit{\"a}t verbindet. Anzustreben ist ein kreisrunder Strahlquerschnitt mit nur einer Strahlungsmode und Gauß-Profil. Dabei sollen die Erfahrungen genutzt werden, die im Institut f{\"u}r Plasma- und Lasertechnik der TFH Wildau bei der Entwicklung von Stickstofflasern mit gauß-{\"a}hnlichem Strahlprofil gewonnen wurden. Ein solches Ger{\"a}t w{\"u}rde die Einsatzgebiete von Eximer-Lasern erweitern und h{\"a}tte voraussichtlich gute Marktchancen.}, language = {de} } @article{RymarczykCzerwoszRichter2011, author = {Rymarczyk, Joanna and Czerwosz, Elzbieta and Richter, Asta}, title = {Topography and nanomechanical properties of Pd-C films}, series = {Central European Journal of Physics}, volume = {9}, journal = {Central European Journal of Physics}, number = {2}, issn = {2391-5471}, doi = {10.2478/s11534-010-0134-5}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9649}, pages = {300 -- 306}, year = {2011}, abstract = {Atomic force microscopy (AFM) topographical studies and results of nanoindentation experiment for several palladium-carbon films (Pd-C film) deposited on various substrates and with varying palladium content are presented. Pd-C films were prepared by a physical vapor decomposition (PVD) process and next were modified by a chemical vapor decomposition (CVD) method to obtain carbonaceous porous structure with dispersed palladium nanograins and a variation in roughness. The dependence of film topography on the kind of substrate such as Al2O3, Mo polycrystalline foil and fused silica was studied by AFM. Nanomechanical properties such as hardness and the reduced indentation modulus were determined by nanoindentation. A comparison of these values for films with different Pd content deposited on various substrates is presented.}, language = {en} } @misc{BeyerHarendtHugetetal.2001, author = {Beyer, Harald and Harendt, Andreas and Huget, Karin and Koschlig, Tobias and Rolle, Siegfried and Ross, Werner and Volkmann, Hans}, title = {Das Institut f{\"u}r Plasma- und Lasertechnik an der TFH Wildau - Entwicklung und Kooperation mit anderen Einrichtungen}, series = {Wissenschaftliche Beitr{\"a}ge 2001}, volume = {6}, journal = {Wissenschaftliche Beitr{\"a}ge 2001}, issn = {0949-8214}, doi = {10.15771/0949-8214_2001_6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-8518}, pages = {38 -- 41}, year = {2001}, abstract = {Die Plasmatechnik geh{\"o}rt mittlerweile zu den Schl{\"u}sseltechnologien des nachhaltigen Wachstums und der Bew{\"a}ltigung des Strukturwandels der deutschen Wirtschaft. Plasmaverfahren sind zur Voraussetzung f{\"u}r die Herstellung von Chips f{\"u}r Hochleistungscomputer geworden. Mit Plasmatechnologien werden Werkstoffoberfl{\"a}chen veredelt und Materialien mit neuen Eigenschaften erzeugt. Es gibt Plasmalampen, die ohne Verwendung von Quecksilber hohe Lichtausbeuten und gute Farbwiedergabe erreichen. Auch bei der Entsorgung toxischer Stoffe und von Abf{\"a}llen kommen Plasmatechnologien zum Einsatz. Das Bundesministerium f{\"u}r Bildung und Forschung (BMBF) hat in einer Brosch{\"u}re die Anwendung und Forschung auf dem Gebiet der Plasmatechnik in Deutschland zusammengestellt. In Deutschland wird j{\"a}hrlich eine Industrieproduktion von 45 Mio. € durch die Plasmatechnologie erst erm{\"o}glicht. Vor diesem Hintergrund soll die Entwicklung der Forschung und Ausbildung auf dem Gebiet der Plasmatechnik an der TFH Wildau beschrieben werden.}, language = {de} } @inproceedings{KirchnerVillringerGutkeetal.2023, author = {Kirchner, Thomas and Villringer, Claus and Gutke, Marko and Laufer, Jan}, title = {Plano-concave optical sensor for transcranial photoacoustic measurements}, series = {Opto-Acoustic Methods and Applications in Biophotonics VI}, booktitle = {Opto-Acoustic Methods and Applications in Biophotonics VI}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17840}, year = {2023}, abstract = {Biomedical photoacoustics is usually used to image absorption-based contrast in soft tissues up to depths of several centimeters and with sub-millimeter resolution. By contrast, measuring Photoacoustic (PA) signals through hard bone tissue shows severe signal degradation due to aberration and high attenuation of high frequency acoustic signal components. This is particularly noticeable when measuring through thicker, human, skull bone. Which is the main reason why transcranial PA imaging in humans has so far proved challenging to implement. To tackle this challenge, we developed an optical resonator sensor based on a previous planar-concave design. This sensor was found to be highly suitable for measuring the low-pressure amplitude and low acoustic frequency signals that are transmitted through human cranial bone. A plano-concave optical resonator sensor was fabricated to provide high sensitivity in the acoustic frequency range of DC to around 2 MHz, a low noise equivalent pressure and a small active element size enabling it to significantly outperform conventional piezoelectric transducers when measuring PA waves transmitted through ex vivo human cranial bones.}, language = {en} } @phdthesis{Lux2015, author = {Lux, Helge}, title = {Carbon-based functional Materials for Application in Photonics, Optoelectronics and Sensorics}, doi = {10.15771/DISS_2015_1}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13916}, school = {Technische Hochschule Wildau}, pages = {105}, year = {2015}, abstract = {In this work, two different processes to deposit Graphene-based transparent conductive films on arbitrary insulting substrates have been developed and examined. The first process is a PE-CVD, based on a gas mixture containing hydrocarbons (e.g. methane) inside a vacuum chamber where the insulating substrates are placed on a temperature controlled heating plate. The second process uses a pulsed filtered vacuum arc system (Phi-HCA) to homogeneously deposit a small, well defined amount of carbon on heated substrates. The substrates are tilted with respect to the particle beam and placed on a heating plate. A gas atmosphere consisting of Argon or Argon/Hydrogen decreases the particle energy and influences the morphology of the growing film. For both processes, Scanning Tunneling Microscopy (STM), Transmission Electron Microscopy (TEM) and Raman spectra have been used for a thorough characterization of the samples in order to optimize the growth parameters. Subsequently, the results (sheet resistance, Hall mobility, transmittance) have been compared with respect to the state of the art, reported in literature. The best carbon layers have a surface resistance of 5E3 Ohm_sqr while the optical transparency of the coatings is 88\% with an excellent homogeneity over areas of several cm^2. Both for the PE-CVD and the Phi-HCA, the area of deposition is only limited by the respective area of the heated surface. The obtained results and the fact, that the process can be compatible with most semiconductor fabrication processes, makes them promising for various industrial applications.}, language = {en} } @article{BaumannPohleZhangetal.2021, author = {Baumann, Elisabeth and Pohle, Ulrike and Zhang, Edward and Allen, Thomas and Villringer, Claus and Pulwer, Silvio and Gerhardt, Holger and Laufer, Jan}, title = {A backward-mode optical-resolution photoacoustic microscope for 3D imaging using a planar Fabry-P{\´e}rot sensor}, series = {Photoacoustics}, volume = {24}, journal = {Photoacoustics}, publisher = {Elsevier}, issn = {2213-5979}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14701}, pages = {100293}, year = {2021}, abstract = {Optical-resolution photoacoustic microscopy (OR-PAM) combines high spatial resolution and strong absorption-based contrast in tissue, which has enabled structural and spectroscopic imaging of endogenous chromophores, primarily hemoglobin. Conventional piezoelectric ultrasound transducers are typically placed far away from the photoacoustic source due to their opacity, which reduces acoustic sensitivity. Optical ultrasound sensors are an alternative as their transparency allows them to be positioned close to the sample with minimal source-detector distances. In this work, a backward-mode OR-PAM system based on a planar Fabry-P{\´e}rot ultrasound sensor and coaxially aligned excitation and interrogation beams was developed. Two 3D imaging modes, using raster-scanning for enhanced image quality and continuous-scanning for fast imaging, were implemented and tested on a leaf skeleton phantom. In fast imaging mode, a scan-rate of 100,000 A-lines/s was achieved. 3D images of a zebrafish embryo were acquired in vivo in raster-scanning mode. The transparency of the FP sensor in the visible and near-infrared wavelength region makes it suitable for combined functional and molecular imaging applications using OR-PAM and multi-photon fluorescence microscopy.}, language = {en} } @inproceedings{PaetowSzymanskiDetjeetal.2021, author = {Paetow, Clara and Szymanski, Mateusz and Detje, Johannes Siljas and Stolpmann, Alexander}, title = {A Model-Based Approach to Decarbonize an Island's Energy System}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14952}, pages = {145 -- 153}, year = {2021}, abstract = {To achieve climate goals and contain further global warming, it is inevitable to reduce CO2 emissions especially in energy consumption. A way to do so is by integrating renewable energy sources (RES) into an energy system's power generation. However, there is no standard procedure to decarbonise a locally restricted system. Therefore, the various local conditions have to be analysed and taken into consideration. The authors propose a model-based approach to decarbonise the energy system of the island F{\"o}hr, Germany. This includes various collected data sets on local conditions such as climate data and heat and power demand. The data is used to represent the island's energy system and design a model-based solution in a simulation software. The authors identify potentials by comparing costs and revenues by addressing the deployment of different RES technologies. One finding is that heat generation causes 91 \% of CO2 emissions making it the major producer. However, with the designed solution, emissions could be reduced to a third.}, language = {en} } @inproceedings{KataSamahTevi2020, author = {Kata, N'detigma and Samah, Hodo-Abalo and Tevi, Gabriel Jean-Philippe}, title = {The contribution of solar energy to environmental protection and poverty reduction}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SI-1b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13288}, pages = {17 -- 23}, year = {2020}, abstract = {The neighborhood population pressure one Djamd{\`e} reserve is investigated in this paper. After noting and observing changes in the microclimate of Djamd{\`e}, a survey was conducted. At the end of this survey, market gardening was proposed not only to remove the increased pressure on the reserve, but also to provide an income generating activity for this very vulnerable population. The collection of data on existing wells in the vicinity of the site shows that the availability of water for market gardening can be ensured by drilling. A comparative study between a pumping system with a petrol-powered pump and a photovoltaic system in the town of Kara has been carried out. The solar pumping system is by far the most interesting for Djamd{\`e} site. Considering the very high initial investment cost of the components of the solar pumping system, its size can be reduced by organizing and planning the watering of the crops.}, language = {en} } @inproceedings{SamahBannaZeghmati2020, author = {Samah, Hodo-Abalo and Banna, Magolm{\`e}{\`e}na and Zeghmati, Belkacem}, title = {Vegetation insulation screen as a passive cooling system in hot humid climate: heat and mass exchanges}, series = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, booktitle = {Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo}, doi = {10.15771/978-3-9819225-5-4_SIII-2b}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13408}, pages = {102 -- 110}, year = {2020}, abstract = {Planted roofs are passive cooling techniques that reduce the thermal load of buildings. In this paper, a dynamic mathematical model based on time average Navier-Stokes equations for a planted roof in hot humid climates has been developed for evaluating the cooling potential.Transfer equations are solved using a finite difference scheme and Thomas algorithm. The model was applied for the simulation of the planted roof in togolese climate conditions. Results showed that, evapotranspiration and Solar Heat gain Factor are functions of the Leaf Area Index which is the most important parameter when considering the foliage material. It is clearly proved that the foliage density and hence the vegetable canopy type selection greatly influence the thermal efficiency of the bioclimatic insulation screen. It was found that a larger Leaf Area Index reduces the solar flux penetration and increases evapotranspiration which is an important parameter when considering surrounding microclimate formation.}, language = {en} } @article{SteglichVillringerDietzeletal.2019, author = {Steglich, Patrick and Villringer, Claus and Dietzel, Birgit and Mai, Christian and Schrader, Sigurd and Casalboni, Mauro and Mai, Andreas}, title = {On-Chip Dispersion Measurement of the Quadratic Electro-Optic Effect in Nonlinear Optical Polymers Using a Photonic Integrated Circuit Technology}, series = {IEEE Photonics Journal}, volume = {11}, journal = {IEEE Photonics Journal}, number = {3}, issn = {1943-0655}, doi = {10.1109/JPHOT.2019.2917665}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12307}, year = {2019}, abstract = {A novel method to determine the dispersion of the quadratic electro-optic effect in nonlinear optical materials by using a silicon-on-insulator microring resonator is presented. The microring consists of a silicon slot waveguide enabling large dc electric field strength at low applied voltages. The dispersion of third-order hyperpolarizability of a linear conjugated dye is approximated by using a two-level model for the off-resonant spectral region. As an example, the dispersion of the resonance wavelength of the resonator filled with a dye doped polymer was measured in dependence of the applied dc voltage. The polymer was poly (methylmethacrylate) doped with 5 wt\% disperse red 1 (DR1), and the measurements have been carried out at the telecommunication wavelength band around 1550 nm (optical C-band). The described measurements represent a new technique to determine the dispersion of the third-order susceptibility and molecular hyperpolarizability of the material filled into the slot of the ring-resonator.}, language = {en} } @incollection{KalishettyhalliMahadevaiahLiskerFraschkeetal.2024, author = {Kalishettyhalli Mahadevaiah, Mamathamba and Lisker, Marco and Fraschke, Mirko and Marschmeyer, Steffen and Perez, Eduardo and Perez-Bosch Quesada, Emilio and Wenger, Christian and Mai, Andreas}, title = {Integration of Memristive Devices into a 130 nm CMOS Baseline Technology}, series = {Bio-Inspired Information Pathways: From Neuroscience to Neurotronics}, booktitle = {Bio-Inspired Information Pathways: From Neuroscience to Neurotronics}, editor = {Ziegler, Martin and Mussenbrock, Thomas and Kohlstedt, Hermann}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-031-36705-2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18029}, publisher = {Technische Hochschule Wildau}, pages = {177 -- 190}, year = {2024}, abstract = {The two main features of the memristive devices which makes them the promising candidates for neuromorphic applications are low power consumption and CMOS compatibility. The monolithic integration of memristive devices with CMOS circuitry paves the way for in-memory computing. This chapter focuses on the factors governing the CMOS integration process. Firstly, the influence of CMOS baseline technology selection on the memristor module is briefly discussed. Secondly, the selection of metal level interconnects and their effect on the memristive device performance is explained. Further, the widely used deposition technique for the CMOS compatible memristive switching layers is presented. Finally, the implementation of the optimized process for the fabrication of the memristive module and its influence on the device performance is presented in terms of electrical characterization results.}, language = {en} } @article{AnandSteglichKreissletal.2024, author = {Anand, Ketan and Steglich, Patrick and Kreissl, Jochen and Chavarin, Carlos Alvarado and Spirito, Davide and Franck, Max and Lecci, Giulia and Costina, Ioan and Herfurth, Norbert and Katzer, Jens and Mai, Christian and Becker, Annette and Reithmaier, Johann Peter and Zimmermann, Lars and Mai, Andreas}, title = {Adhesive-free bonding for hetero-integration of InP based coupons micro-transfer printed on SiO2 into Complementary Metal-Oxide-Semiconductor backend for Si photonics application on 8" wafer platform}, series = {Thin Solid Films}, journal = {Thin Solid Films}, number = {140399}, publisher = {Elsevier}, issn = {0040-6090}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19240}, year = {2024}, abstract = {Micro-Transfer printing (µTP) is a promising technique for hetero-integration of III-V materials into Si-based photonic platforms. To enhance the print yield by increasing the adhesion between the III-V material and Si or SiO2 surface, an adhesion promoter like Benzocyclobutene is typically used as interlayer. In this work, we demonstrate µTP of InP based coupons on SiO2 interlayer without any adhesive interlayer and investigate the mechanism of adhesive free bonding. Source coupons are InP-based coupon stacks on a sacrificial layer that is removed by a chemical wet etch with FeCl3. For the target we fabricated amorphous-Si waveguides on 8" wafer encapsulated by a High Density Plasma SiO2 which was planarized by a chemical mechanical polishing procedure. We used O2 plasma to activate both source and target to increase adhesion between coupon and substrate. To get a better understanding of the bonding mechanism we applied several surface characterization methods. Root mean square roughness of InP and SiO2 was measured by atomic force microscopy before and after plasma activation. The step height of the micro-transfer printed source coupon on the target wafer is estimated by optical step profiler. We used Raman peak position mappings of InP to analyze possible strain and contact angle measurements on SiO2, before and after plasma activation to observe a change in the hydrophilicity of the surface. X-ray Photoelectron Spectroscopy analysis was used to characterize the surface energy states of P2p, In3d, O1s for InP source and Si2p, O1s for SiO2 target. Our results demonstrate direct bonding of InP coupons by means of µTP without the need of a strain-compensation layer. In this way, a promising route towards Complementary Metal-Oxide-Semiconductor compatible use of µTP for the hetero-integration of InP is provided.}, language = {en} } @article{KlimesovaRoosHoqueetal.2024, author = {Klimesov{\´a}, Eva and Roos, Andreas Hult and Hoque, Ziaul and Smijesh, N. and Squibb, R.J. and Coudert-Alteirac, H. and Feifel, R. and Andreasson, Jakob and Krikunova, Maria}, title = {Update on MAC End-Station at ELI Beamlines Facility}, series = {Acta Physica Polonica A}, volume = {145}, journal = {Acta Physica Polonica A}, number = {2}, publisher = {Institute of Physics (IOP) and Polish Physical Society}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-18840}, pages = {118 -- 122}, year = {2024}, abstract = {The MAC end-station at the ELI Beamlines facility is a multipurpose user's station for atomic, molecular, and optical sciences and coherent diffractive imaging. The technical design of the station, the available instruments, and an overview of the whole beamline have been published in Eur. Phys. J. Spec. Top. 230, 4183 (2021). Here, we address ongoing upgrades of the MAC end-station that will provide users with advanced capabilities for beam manipulation and electron/ion detection. The upgrades include (i) the installation of a beam preparation chamber in front of the MAC chamber, (ii) a magnetic bottle electron spectrometer with high collection and detection efficiency and high energy resolution, and (iii) an event-driven TPX3CAM detector for velocity map imaging spectrometer, which provides both spatial and temporal information for each pixel. We present results from the first commissioning measurements with these instruments, confirming their performance for state-of-the-art experiments in atomic, molecular, and optical sciences.}, language = {en} } @unpublished{RichterAnwandChenetal.2017, author = {Richter, Asta and Anwand, Wolfgang and Chen, Chun-Liang and B{\"o}ttger, Roman}, title = {Evaluation of defect formation in helium irradiated Y2O3 doped W-Ti alloys by positron annihilation and nanoindentation}, series = {Journal of Nuclear Materials}, journal = {Journal of Nuclear Materials}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10048}, year = {2017}, abstract = {Helium implanted tungsten-titanium ODS alloys are investigated using positron annihilation spectroscopy and nanoindentation. Titanium reduces the brittleness of the tungsten alloy, which is manufactured by mechanical alloying. The addition of Y2O3 nanoparticles increases the mechanical properties at elevated temperature and enhances irradiation resistance. Helium ion implantation was applied to simulate irradiation effects on these materials. The irradiation was performed using a 500 kV He ion implanter at fluences around 5 × 1015 cm-2 for a series of samples both at room temperature and at 600 °C. The microstructure and mechanical properties of the pristine and irradiated W-Ti-ODS alloy are compared with respect to the titanium and Y2O3 content. Radiation damage is studied by positron annihilation spectroscopy analyzing the lifetime and the Doppler broadening. Three types of helium-vacancy defects were detected after helium irradiation in the W-Ti-ODS alloy: small defects with high helium-to-vacancy ratio (low S parameter) for room temperature irradiation, larger open volume defects with low helium-to-vacancy ratio (high S parameter) at the surface and He-vacancy complexes pinned at nanoparticles deeper in the material for implantation at 600 °C. Defect induced hardness was studied by nanoindentation. A drastic hardness increase is observed after He ion irradiation both for room temperature and elevated irradiation temperature of 600 °C. The Ti alloyed tungsten-ODS is more affected by the hardness increase after irradiation compared to the pure W-ODS alloy.}, language = {en} } @inproceedings{SzymanskivandeSandTauscheretal.2021, author = {Szymanski, Mateusz and van de Sand, Ron and Tauscher, Esther and Rieckmann, Olaf and Stolpmann, Alexander}, title = {Concept Towards Segmenting Arm Areas for Robot-Based Dermatological In Vivo Measurements}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14986}, pages = {217 -- 228}, year = {2021}, abstract = {Dermatological in vivo measurements are used for various purposes, e.g. health care, development and testing of skin care products or claim support in marketing. Especially for the last two purposes, in vivo measurements are extensive due to the quantity and repeatability of the measurement series. Furthermore, they are performed manually and therefore represent a nonnegligible time and cost factor. A solution to this is the implementation of collaborative robotics for the measurement execution. Due to various body shapes and surface conditions, common static control procedures are not applicable. To solve this problem, spatial information obtained from a stereoscopic camera can be integrated into the robot control process. However, the designated measurement area has to be detected and the spatial information processed. Therefore the authors propose a concept towards segmenting arm areas through a CNN-based object detector and their further processing to perform robot-based in vivo measurements. The paper gives an overview of the utilization of RGB-D images in 2D object detectors and describes the selection of a suitable model for the application. Furthermore the creation, annotation and augmentation of a custom dataset is presented.}, language = {en} } @article{JaenchenStach2012, author = {J{\"a}nchen, Jochen and Stach, Helmut}, title = {Adsorption properties of porous materials for solar thermal energy storage and heat pump applications}, series = {Energy Procedia}, volume = {30}, journal = {Energy Procedia}, number = {2012}, issn = {1876-6102}, doi = {10.1016/j.egypro.2012.11.034}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6160}, pages = {289 -- 293}, year = {2012}, abstract = {The water adsorption properties of modified porous sorbents for solar thermal energy storage and heat transformation have been investigated by thermogravimetry (TG) differential thermogravimetry (DTG), microcalorimetry, measurements of water adsorption isotherms, and storage tests. A chabazite type SAPO, a dealuminated faujasite type zeolite, and a mesostructured aluminosilicate, have been synthesized and compared with common zeolites X, Y and silica gel. It has been found that optimized lattice composition and pore architecture contribute to well adapt hydrophilic properties and a beneficial steep isotherm.}, language = {en} } @article{KlingspornKirnerVillringeretal.2016, author = {Klingsporn, M. and Kirner, S. and Villringer, Claus and Abou-Ras, D. and Costina, Ioan and Lehmann, M. and Stannowski, B.}, title = {Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiOx layers for application in solar cells}, series = {Journal of Applied Physics}, volume = {119}, journal = {Journal of Applied Physics}, number = {22}, issn = {1089-7550}, doi = {10.1063/1.4953566}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9727}, year = {2016}, abstract = {Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.}, language = {en} } @inproceedings{RichterRies1999, author = {Richter, Asta and Ries, Ronald}, title = {Mechanical properties of fullerite and diamondlike carbon films using surface acoustic waves and nanoindentation}, series = {Proc. SPIE 3725, International Conference on Solid State Crystals '98: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, (8 April 1999)}, booktitle = {Proc. SPIE 3725, International Conference on Solid State Crystals '98: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, (8 April 1999)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14840}, pages = {94 -- 101}, year = {1999}, abstract = {C60 and amorphous diamond-like carbon (DLC) films have been grown by thermal evaporation and laser ablation techniques at different substrate temperatures and on various substrates. The elastic modulus and the hardness of the films have been investigated by surface acoustic waves and nanoindentation. Both methods are completely new and designed for investigations of very thin films. For homogeneous C60 films the Young's modulus was found to be 14 GPa and the Poisson's ratio of 0.2. The measured nanohardness of 167 MPa corresponds with the microhardness value of 130 MPa. There is a correlation between deposition techniques and hardness as well as Young's modulus for DLC films.}, language = {en} } @article{GrytsenkoKolomzarovLytvynetal.2023, author = {Grytsenko, Kostyantyn and Kolomzarov, Yurii and Lytvyn, Peter and Kondratenko, Olga and Sopinskyy, Mykola and Lebedyeva, Iryna and Niemczyk, Agata and Baranovska, Jolanta and Moszyński, Dariusz and Villringer, Claus and Schrader, Sigurd}, title = {Optical and Mechanical Properties of Thin PTFE Films, Deposited from a Gas Phase}, series = {Macromolecular Materials and Engineering}, volume = {308}, journal = {Macromolecular Materials and Engineering}, number = {6}, publisher = {Wiley}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17587}, year = {2023}, abstract = {Thin polytetrafluoroethylene (PTFE) films are produced by deposition from a gas phase by two methods: electron-enhanced vacuum deposition (EVD) and EVD + low-temperature plasma (LTP). Structure, morphology, and composition of the films are studied by IR spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. They are close to the structure of bulk PTFE. The roughness of the films' surface is changed with gas pressure and LTP power variations. Films are transparent from UV to near-infrared regions. Refractive and extinction indices and their anisotropy are measured by spectral ellipsometry. They are tuned by variations of deposition conditions. Hardness and Young modulus of the films are increased if EVD + low power LTP is used for film deposition. Use of EVD + LTP also increases thermal stability of the films. Contact angle of the films corresponds to the bulk PTFE. The PTFE molecules oriented are preferentially in perpendicular direction to the substrate surface.}, language = {en} } @inproceedings{RymarczykCzerwoszRichter2009, author = {Rymarczyk, Joanna and Czerwosz, Elzbieta and Richter, Asta}, title = {FEM modelling of nanoindentation experiment for nanostructural Me-carbon film (Me = Pd, Ni)}, series = {Proc. SPIE 7502, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2009}, booktitle = {Proc. SPIE 7502, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2009}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14837}, year = {2009}, abstract = {This work presents a comparison of numerical simulation and experimental data for nanoindentation studies of nanostructural Me-carbonaceous films (where Me = Pd or Ni). Films containing palladium or nickel nanograins embedded in a carbonaceous matrix were synthesized by a PVD process. The topography of films was characterized by AFM and the mechanical properties were analyzed by nanoindentation. Nanoindentation experiments were performed with a tip made of diamond with a shape of a 90° cube corner three-sided pyramid in a Hysitron Triboscope. The finite element method (FEM) was used to simulate the indentation experiment in such heterogeneous material on nanoscale.}, language = {en} } @article{SteglichLecciMai2022, author = {Steglich, Patrick and Lecci, Giulia and Mai, Andreas}, title = {Surface Plasmon Resonance (SPR) Spectroscopy and Photonic Integrated Circuit (PIC) Biosensors: A Comparative Review}, series = {Sensors}, volume = {22}, journal = {Sensors}, number = {8}, publisher = {MDPI}, issn = {1424-8220}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16018}, year = {2022}, abstract = {Label-free direct-optical biosensors such as surface-plasmon resonance (SPR) spectroscopy has become a gold standard in biochemical analytics in centralized laboratories. Biosensors based on photonic integrated circuits (PIC) are based on the same physical sensing mechanism: evanescent field sensing. PIC-based biosensors can play an important role in healthcare, especially for point-of-care diagnostics, if challenges for a transfer from research laboratory to industrial applications can be overcome. Research is at this threshold, which presents a great opportunity for innovative on-site analyses in the health and environmental sectors. A deeper understanding of the innovative PIC technology is possible by comparing it with the well-established SPR spectroscopy. In this work, we shortly introduce both technologies and reveal similarities and differences. Further, we review some latest advances and compare both technologies in terms of surface functionalization and sensor performance.}, language = {en} } @inproceedings{VandenhoutenHermerschmidtFiebelkorn2017, author = {Vandenhouten, Ralf and Hermerschmidt, Andreas and Fiebelkorn, Richard}, title = {Design and quality metrics of point patterns for coded structured light illumination with diffractive optical elements in optical 3D sensors}, series = {Proceedings of SPIE}, volume = {10335}, booktitle = {Proceedings of SPIE}, issn = {1996-756X}, doi = {10.1117/12.2270248}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9798}, year = {2017}, abstract = {Structured light has become a widespread technique for the development of camera-based 3D sensors. The structured illumination provides texture to homogeneous objects and thus allows for the reliable determination of the disparity of each object point in a stereo-camera setting. Even a monocular 3D sensor is possible if the light projector has a fixed relative position to the camera and if the structured light is coded, i.e. the position within the whole light pattern can be reconstructed uniquely from a small local window of the pattern, the uniqueness window. Coded patterns with such a uniqueness property are called Perfect SubMaps (PSM). In our paper we focus on the design and evaluation of the subset of symmetric isolated binary toroidal PSMs (SIBTPSM) for structured light patterns, because of their beneficial properties with respect to the signal-to-noise ratio and the use with laser light sources and DOEs. We define several figures of merit that are relevant for the practical use of PSMs in a 3D sensor: the PSM size, the size of the uniqueness window, the Hamming distance, the density, and the homogeneity. We have created SIBTPSMs using our own dedicated algorithms and have designed and fabricated DOEs that produce these patterns with large fan angles of 61° × 47° when used with near-infrared diode lasers (λ = 830nm). We analyze the influence of these characteristics on the 3D measurement process by theory, simulations, and experiments. The patterns of publicly available DOEs based on SIBTPSMs are used for comparison and reference. Our results show that the PSM width, the uniqueness window size, the minimum and average Hamming distances, and the uniformity have strong impact on either speed or quality of the 3D reconstruction, whereas the point density and the PSM height are of minor importance.}, language = {en} } @article{SteglichSchasfoort2022, author = {Steglich, Patrick and Schasfoort, Richard B. M.}, title = {Surface Plasmon Resonance Imaging (SPRi) and Photonic Integrated Circuits (PIC) for COVID-19 Severity Monitoring}, series = {COVID}, volume = {2}, journal = {COVID}, number = {3}, publisher = {MDPI}, issn = {2673-8112}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16004}, pages = {389 -- 397}, year = {2022}, abstract = {Direct optical detection methods such as surface plasmon resonance imaging (SPRi) and photonic-integrated-circuits (PIC)-based biosensors provide a fast label-free detection of COVID-19 antibodies in real-time. Each technology, i.e., SPRi and PIC, has advantages and disadvantages in terms of throughput, miniaturization, multiplexing, system integration, and cost-effective mass production. However, both technologies share similarities in terms of sensing mechanism and both can be used as high-content diagnostics at or near to point of care, where the analyte is not just quantified but comprehensively characterized. This is significant because recent results suggest that not only the antibody concentration of the three isotypes IgM, IgG, and IgA but also the strength of binding (affinity) gives an indication of potential COVID-19 severity. COVID-19 patients with high titers of low affinity antibodies are associated with disease severity. In this perspective, we provide some insights into how SPR and PIC technologies can be effectively combined and complementarily used for a comprehensive COVID-19 severity monitoring. This opens a route toward an immediate therapy decision to provide patients a treatment in an early stage of the infection, which could drastically lowers the risk of a severe disease course.}, language = {en} } @article{RistićFurboMoseretal.2016, author = {Ristić, Alenka and Furbo, Simon and Moser, Christoph and Schranzhofer, Hermann and Lazaro, Ana and Delgado, Monica and Pe{\~n}alosa, Conchita and Zalewski, Laurent and Diarce, Gonzalo and Alkan, Cemil and Gunasekara, Saman N. and Haussmann, Thomas and Gschwander, Stefan and Rathgeber, Christoph and Schmit, Henri and Barreneche, Camila and Cabeza, Luiza and Ferrer, Gerard and Konuklu, Yeliz and Paksoy, Halime and Rammelberg, Holger and Munz, Gunther and Herzog, Thomas H. and J{\"a}nchen, Jochen and del Barrio, Elena Palomo}, title = {IEA SHC Task 42 / ECES Annex 29 WG A1: Engineering and Processing of PCMs, TCMs and Sorption Materials}, series = {Energy Procedia}, volume = {91}, journal = {Energy Procedia}, issn = {1876-6102}, doi = {10.1016/j.egypro.2016.06.205}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6629}, pages = {207 -- 217}, year = {2016}, abstract = {An overview on the recent results on the engineering and characterization of sorption materials, PCMs and TCMs investigated in the working group WG A1 "Engineering and processing of TES materials" of IEA SHC Task 42 / ECES Annex 29 (Task 4229) entitled "Compact Thermal Energy Storage" is presented.}, language = {en} } @inproceedings{PrellGuentherReiffStephan2021, author = {Prell, Bastian and G{\"u}nther, Norman and Reiff-Stephan, J{\"o}rg}, title = {Cyber-Physical Production Systems in Settings with Limited Infrastructure}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14993}, pages = {229 -- 238}, year = {2021}, abstract = {During the last decade production innovation was mainly focused on connectivity aspects. The vision of smart factories running on software, that uses collected machine data, has become true but foremost for leading industrial companies in highly developed countries. Apart from these, production can also be found in non-industrialized craft professions as well as in less developed countries. As digitalization does not necessarily require an industrial or developed setting the latter could possibly benefit from it as well. Socio-cyber-physical production systems have been used to describe the interdependencies of linked production systems but usually focus on highly developed regions as well as for industrial applications. This paper lines out similarities and differences for each case, introduces the concept of cyber-physical production systems (CPPS) and its extension to socio-CPPS (SCPPS), which emphasizes the role of human workers in the production environment. The relation between industrial, non-industrial production and innovations is examined. Furthermore, the widening of SCCPS concepts for non-industrial production is discussed.}, language = {en} } @inproceedings{LebekHeyrothSyrowatkaetal.2023, author = {Lebek, Werner and Heyroth, Frank and Syrowatka, Frank and Villringer, Claus and Goerlitz, Sylvia and Laufer, Jan}, title = {Evaluation of fabrication methods for Fabry-Perot polymer film ultrasound sensors}, series = {Opto-Acoustic Methods and Applications in Biophotonics VI}, booktitle = {Opto-Acoustic Methods and Applications in Biophotonics VI}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17864}, year = {2023}, abstract = {Fabry-P{\`e}rot (FP) interferometer sensors enable highly sensitive backward mode acoustic detection in Photoacoustic (PA) imaging. They are transparent to the excitation wavelength, can be placed directly next to the PA source, and offer a broadband frequency response and high acoustic sensitivity. PA tomography using parallelized detection requires high spatial uniformity of the optical and acoustic properties, which can be hampered by contaminations during fabrication that lead to the formation of inhomogeneities and artefacts. The quality and homogeneity of the dielectric and polymer layers have a direct effect on the maximum optical phase sensitivity, and hence acoustic sensitivity. In this study, cross-sectional images of FP sensors were obtained using focused ion beam milling and ultramicrotomy followed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to evaluate different fabrication methods.}, language = {en} } @article{MikayelyanGroddKsianzouetal.2019, author = {Mikayelyan, Eduard and Grodd, Linda and Ksianzou, Viachaslau and Wesner, Daniel and Rodygin, Alexander I. and Sch{\"o}nherr, Holger and Luponosov, Yuriy N. and Ponomarenko, Sergei A. and Ivanov, Dimitri A. and Pietsch, Ullrich and Grigorian, Souren}, title = {Phase Transitions and Formation of a Monolayer-Type Structure in Thin Oligothiophene Films: Exploration with a Combined In Situ X-ray Diffraction and Electrical Measurements}, series = {Nanoscale Research Letters}, volume = {14}, journal = {Nanoscale Research Letters}, issn = {1556-276X}, doi = {10.1186/s11671-019-3009-8}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12314}, year = {2019}, abstract = {A combination of in situ electrical and grazing-incidence X-ray diffraction (GIXD) is a powerful tool for studies of correlations between the microstructure and charge transport in thin organic films. The information provided by such experimental approach can help optimizing the performance of the films as active layers of organic electronic devices. In this work, such combination of techniques was used to investigate the phase transitions in vacuum-deposited thin films of a common organic semiconductor dihexyl-quarterthiophene (DH4T). A transition from the initial highly crystalline phase to a mesophase was detected upon heating, while only a partial backward transition was observed upon cooling to room temperature. In situ electrical conductivity measurements revealed the impact of both transitions on charge transport. This is partly accounted for by the fact that the initial crystalline phase is characterized by inclination of molecules in the plane perpendicular to the π-π stacking direction, whereas the mesophase is built of molecules tilted in the direction of π-π stacking. Importantly, in addition to the two phases of DH4T characteristic of the bulk, a third interfacial substrate-stabilized monolayer-type phase was observed. The existence of such interfacial structure can have important implications for the charge mobility, being especially favorable for lateral two-dimensional charge transport in the organic field-effect transistors geometry.}, language = {en} } @inproceedings{SchmidtGiese2021, author = {Schmidt, Marcus and Giese, Lutz B.}, title = {Bi-facial Open-Space Photovoltaic Systems versus Conventional Systems using Mono-facial Modules}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021)}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14922}, pages = {37 -- 42}, year = {2021}, abstract = {As part of a scientific work within the solar company Sunfarming GmbH, the aim was to find out whether bi-facial modules on open spaces deliver better results economically than conventional mono-facial solar modules. In this context, an already installed 750 kWp PV system with mono-facial solar modules was compared directly with a structurally identical PV system with bi-facial modules, which, however, does not exist in practice but was only simulated with PV software. The second part of the investigation includes the comparison of four different assembly systems or elevation variants in order to determine the system with the best relationship between system yield and costs. The final result of the first investigation showed that the use of bi-facial modules reduced the specific costs per kWh by approximately 5 \%. In order to improve this effect, the use of compact assembly systems is recommended, e.g. five rows of modules per table with horizontal alignment.}, language = {en} } @article{MaiMaiSteglich2022, author = {Mai, Andreas and Mai, Christian and Steglich, Patrick}, title = {From Lab-on-chip to Lab-in-App: Challenges towards silicon photonic biosensors product developments}, series = {Results in Optics}, volume = {9}, journal = {Results in Optics}, publisher = {Elsevier}, issn = {2666-9501}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16687}, year = {2022}, abstract = {This work presents and evaluates different approaches of integrated optical sensors based on photonic integrated circuit (PIC) technologies for refractive index sensing. Bottlenecks in the fabrication flow towards an applicable system are discussed that hinder a cost-effective mass-production for disposable sensor chips. As sensor device, a waveguide coupled micro-ring based approach is chosen which is manufactured in an 8" wafer level process. We will show that the co-integration with a reproducible, scalable and low-cost microfluidic interface is the main challenge which needs to be overcome for future application of silicon technology based PIC sensor chips.}, language = {en} } @inproceedings{GribovaGiese2021, author = {Gribova, Maria and Giese, Lutz B.}, title = {Sustainably Produced Hydrogen}, series = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021}, booktitle = {2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021}, publisher = {TIB Open Publishing}, address = {Hannover}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14940}, pages = {107 -- 116}, year = {2021}, abstract = {The fossil fuels used to provide energy, such as coal, crude oil and natural gas, are largely responsible for carbon dioxide emissions and other so-called greenhouse gases. Hydrogen gas (H2) can make a key contribution to decarbonization. It can be produced using various processes. Several processes are available to produce hydrogen, such as (i) steam reforming, (ii) cracking process or (iii) electrolysis. Depending on the source of origin, there is a distinction made between different "colours". Gray, blue, turquoise, yellow and green hydrogen is avail­able, the latter made using Renewable Energies. However, items such as (i) possible variants of hydrogen, (ii) leading export countries or (iii) provision paths to be preferred in the future will be discussed in this paper.}, language = {en} } @article{VillringerSteglichPulweretal.2021, author = {Villringer, Claus and Steglich, Patrick and Pulwer, Silvio and Schrader, Sigurd and Laufer, Jan}, title = {Electro-optical properties of doped polymers with high transparency in the visible wavelength range}, series = {Optical Materials Express}, volume = {11}, journal = {Optical Materials Express}, number = {11}, publisher = {Optica Publishing Group}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15480}, pages = {3801 -- 3811}, year = {2021}, abstract = {The electro-optical (EO) properties of poly(methyl methacrylate) and the photopolymer poly(vinyl cinnamate) doped with varying concentrations of the EO chromophore 2-Methyl-4-nitroaniline were measured. The EO polymers were embedded in Fabry-P{\´e}rot etalons for the simultaneous determination of the Pockels and Kerr coefficients from measurements of the fringe shift induced by an external electric field. It was found that the host polymer has a significant impact on the EO performance and that the undoped host polymers exhibit a significant Pockels effect. Moreover, the Kerr effect provides a substantial contribution of 27\% to the total change of the refractive index at relatively high electric field strengths of E = 91.2 MV m-1.}, language = {en} } @article{HerzogJaenchenKontogeorgopoulosetal.2014, author = {Herzog, Thomas H. and J{\"a}nchen, Jochen and Kontogeorgopoulos, Eythymius M. and Lutz, Wolfgang}, title = {Steamed Zeolites for Heat Pump Applications and Solar Driven Thermal Adsorption Storage}, series = {Energy Procedia}, volume = {48}, journal = {Energy Procedia}, issn = {1876-6102}, doi = {10.1016/j.egypro.2014.02.044}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5951}, pages = {380 -- 383}, year = {2014}, abstract = {The influence of the dealumination degree of NaY with respect to the water adsorption properties was investigated by infrared spectroscopy, thermogravimetry and isotherm measurements. The modification of the samples is a result of a steaming process at different temperatures in dependence of time. It was found that dealumination controls the hydrophilic behavior of NaY and contributes to defined low desorption temperatures. Similar to microporous SAPO's steamed Y-zeolites can be used for low temperature applications of heat transformation and thermal adsorption storage.}, language = {en} } @article{HerzogJaenchen2016, author = {Herzog, Thomas H. and J{\"a}nchen, Jochen}, title = {Adsorption Properties of Modified Zeolites for Operating Range Enhancement of Adsorption Heat Pumps through the Use of Organic Adsorptive Agents}, series = {Energy Procedia}, volume = {91}, journal = {Energy Procedia}, issn = {1876-6102}, doi = {10.1016/j.egypro.2016.06.192}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6614}, pages = {155 -- 160}, year = {2016}, abstract = {Faujasite zeolites with the highest possible Al-content and different cations as well as a dealuminated zeolite Y have been chosen to study the impact on the adsorption behavior in view of differed adsorptive agents for heat pumps or thermochemical storages. Our results show advantages and disadvantages for water, methanol or ethanol adsorption due to the structure of the anion skeleton, kind of cations and size of the adsorbat molecule.}, language = {en} }