TY - JOUR A1 - Mikayelyan, Eduard A1 - Grodd, Linda A1 - Ksianzou, Viachaslau A1 - Wesner, Daniel A1 - Rodygin, Alexander I. A1 - Schönherr, Holger A1 - Luponosov, Yuriy N. A1 - Ponomarenko, Sergei A. A1 - Ivanov, Dimitri A. A1 - Pietsch, Ullrich A1 - Grigorian, Souren T1 - 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 JF - Nanoscale Research Letters N2 - 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. KW - thin film KW - interfacial monolayer KW - oligomer KW - quarterthiophene KW - in situ GIXD KW - phase transition KW - mesophase Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-12314 SN - 1556-276X VL - 14 ER - TY - JOUR A1 - Grytsenko, Kostyantyn A1 - Ksianzou, Viachaslau A1 - Kolomzarov, Yurii A1 - Lytvyn, Peter A1 - Dietzel, Birgit A1 - Schrader, Sigurd T1 - Fluoropolymer Film Formation by Electron Activated Vacuum Deposition JF - Surfaces N2 - Polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE) were heated to their decomposition temperature in a high vacuum. The emitted fragments passed an electron cloud, condensed on a substrate and formed fluoropolymer film. Growth rate of PTFE and PHFP films increased up to a factor five in the presence of the electron cloud. Mass spectrometry revealed changes in the mass spectra of fragments generated by thermal decomposition only and formed under electron activation. The observed changes were different for each fluoropolymer. Infrared spectroscopy (IRS) showed that the structure of the films was close to the structure of the bulk polymers. Atomic force microscopy (AFM) has revealed different morphologies of PTFE, PHFP and PCTFE films, suggesting a Volmer–Weber growth mechanism for PTFE and PHFP but a Frank-van der Merwe one for PCTFE. All films were smooth at nanoscale and transparent from ultraviolet to near-infrared region. Additional radio frequency (RF) plasma ignited in the emitted fragments at a low pressure increased mechanical characteristics of the films without losing their optical transparency and smoothness. KW - fluoropolymer thin film KW - vacuum deposition KW - polymerization KW - plasma KW - surface Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13786 SN - 2571-9637 VL - 4 IS - 1 SP - 66 EP - 80 PB - MDPI ER - TY - CHAP A1 - Padilla-Michel, Yazmin A1 - Pulwer, Silvio A1 - Saffari, Pouneh A1 - Ksianzou, Viachaslau A1 - Schrader, Sigurd T1 - On the origin and removal of interference patterns in coated multimode fibres N2 - In this study, we present the experimental investigations on interference patterns, such as those already reported in VIMOS-IFU, and up to now no appropriate explanation has been presented. These interference patterns are produced in multimode fibres coated with acrylate or polyimide, which is the preferred coating material for the fibres used in IFUs. Our experiments show that, under specific conditions, cladding modes interact with the coating and produce interference. Our results show that the conditions at which the fibre is held during data acquisition has an impact in the output spectrum. Altering the positioning conditions of the fibre leads to the changes into the interference pattern, therefore, fibres should be carefully manipulated in order to minimise this potential problem and improve the performance of these instruments. Finally we present a simple way of predicting and modelling this interference produced from the visible to the near infrared spectra. This model can be included in the data reduction pipeline in order to remove the interference patterns. These results should be of interest for the optimisation of the data reduction pipelines of instruments using optical fibres. Considering these results will benefit innovations and developments of high performance fibre systems. KW - instrumentation KW - multimode fibre KW - bending loss KW - fringing KW - interference KW - coating material KW - data reduction Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15295 SP - 1517 EP - 1527 PB - Society of Photo-Optical Instrumentation Engineers (SPIE) ER - TY - JOUR A1 - Ksianzou, Viachaslau A1 - Velagapudi, R. K. A1 - Grimm, Bernd A1 - Schrader, Sigurd T1 - Polarization-dependent optical characterization of poly(phenylquinoxaline) thin films JF - Journal of Applied Physics N2 - 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. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9761 SN - 1089-7550 VL - 100 IS - 6 ER - TY - CHAP A1 - Grytsenko, Kostyantyn A1 - Doroshenko, T. A1 - Kolomzarov, Yurii A1 - Prokopets, Vadym M. A1 - Fedoriak, O. A1 - Zelinski, R. A1 - Lytvyn, Oksana A1 - Prescher, Dietrich A1 - Grimm, Bernd A1 - Ksianzou, Viachaslau A1 - Schrader, Sigurd A1 - Tolmachev, O. I. A1 - Slominskii, Yu L. A1 - Kurdiukov, V. A1 - Smirnova, G. T1 - Research on the growth of dye film in vacuum in situ N2 - Organic film deposition in vacuum is fast developing scientific and industrial domain. We developed installation for deposition of organic films equipped with optical spectrometer for measurements in situ. We are developing new dyes aimed for application in waveguide sensor, nonlinear optics and studying film organisation during deposition. Fluorinated azo-dyes and azomethine dyes were synthesized at University of Applied Sciences Wildau and at the Institute of Organic Chemistry, Kyiv. Compounds were evaporated at a pressure of 10-3 Pa using resistive heated crucible. Glass and glass covered with polytetrafluoroethylene (PTFE) film are used as substrates. The films were studied with Polytec and StellarNet spectrometers and an atomic force microscope. Optical spectra of the dye films revealed, that some compounds were decomposed during evaporation. Several kinds of dyes were evaporated and deposited without decomposition. Some deposited films formed H-aggregates and other types of aggregates. AFM images of dye films showed that their morphology depends on the chemical structure of the compounds and on the nature of the substrate on which the film was grown. KW - dye KW - solid KW - film KW - in situ KW - optical spectra KW - vacuum deposition Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15206 SP - 318 EP - 323 PB - Society of Photo-Optical Instrumentation Engineers (SPIE) ER - TY - JOUR A1 - Ksianzou, Viachaslau A1 - Villringer, Claus A1 - Grytsenko, Kostyantyn A1 - Pekur, Demyd A1 - Lytvyn, Peter A1 - Sopinskyy, Mykola A1 - Lebedyeva, Iryna A1 - Niemczyk, Agata A1 - Baranowska, Jolanta T1 - Structural and Optical Anomalies in Thin Films Grown in a Magnetic Field by Electron-Assisted Vacuum Deposition of PTFE JF - Macromolecular Materials and Engineering N2 - Polytetrafluoroethylene (PTFE) films are deposited in parallel and perpendicular magnetic fields (MF) by electron-enhanced vacuum deposition (EVD) and EVD + low-temperature plasma (LTP) methods. The structure, morphology, and nanomechanical properties of the films are studied by infrared spectroscopy (IRS), atomic force microscopy (AFM), and spectroscopic ellipsometry. The structure of the thicker films is closer to that of bulk PTFE than that of thin films. The films' crystallinity and surface roughness are higher than those deposited without MF. The birefringence of the refractive index (n) of the films deposited in the MF is inverse to the anisotropy of the n of the films deposited without MF. The hardness of the films is close to that of bulk PTFE. KW - birefringence KW - deposition in vacuum KW - morphology KW - plasma KW - thin polytetrafluoroethylene film Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-19712 VL - 310 IS - 3 PB - Wiley ER - TY - CHAP A1 - Meister, Stefan A1 - Al-Saadi, Aws A1 - Franke, Bülent A. A1 - Mahdi, Shaimaa A1 - Kuhlow, Berndt A1 - Voigt, Karsten A1 - Tillack, Bernd A1 - Richter, Harald H. A1 - Zimmermann, Lars A1 - Ksianzou, Viachaslau A1 - Schrader, Sigurd A1 - Eichler, Hans J. T1 - Photonic crystal microcavities in SOI waveguides produced in a CMOS environment N2 - We have investigated microcavities in Silicon-on-Insolator (SOI) waveguides. The rectangular waveguides with 500 nm width are fabricated in the 220 nm silicon device layer. The microcavities are formed by one-dimensional photonic crystals in Fabry-Perot structure directly written in the waveguides. The SOI photonic structures are produced in a CMOS environment using 248 nm DUV lithography, where the waveguides as well as the photonic crystals are created in the same step using a single mask. In order to achieve a desired spectral shape of the filter function capable for several applications, a number of different cavities were investigated, e.g. single cavities of first and higher order as well as multi-cavity filters. The experimental results are compared with simulations of photonic crystal microcavities in strip waveguides. The spectral transmission function of such filters dependent on the design parameters are calculated by an analysis based on Finite-Difference-Time-Domain (FDTD) method. KW - silicon photonics KW - SOI waveguide KW - photonic crystal KW - band-pass filter KW - microcavity KW - FDTD simulation Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15223 SP - 330 EP - 339 PB - Society of Photo-Optical Instrumentation Engineers (SPIE) ER - TY - CHAP A1 - Wang, Sha A1 - Meister, Stefan A1 - Mahdi, Shaimaa A1 - Franke, Bülent A. A1 - Al-Saadi, Aws A1 - Zimmermann, Lars A1 - Richter, Harald H. A1 - Stolarek, David A1 - Lisinetskii, Viktor A1 - Ksianzou, Viachaslau A1 - Schrader, Sigurd A1 - Eichler, Hans J. T1 - Spontaneous and stimulated Raman scattering in planar silicon waveguides N2 - Raman scattering in planar silicon on insulator (SOI) waveguides with 2 μm width, 220 nm height and 2 cm length is investigated. A cw Nd:YAP laser at 1340.6 nm with 7 GHz FWHM spectral width is used as the pump source. A lensed fiber of 2.5 μm focus diameter is used to couple the pump laser into the waveguide. The coupling efficiency is estimated to be around 10%. Spontaneous Raman scattering is observed with as low as 2.5 mW pump power inside the waveguide. The spontaneous Raman spectrum is measured by an optical spectrum analyzer. The first order Raman peak is measured at around 1441.4 nm corresponding to a Raman shift of 15.6 THz, while the FWHM of Raman spectrum is measured as around 100 GHz. Maximum Raman output of around 90 pW is obtained by around 22 mW pump. The stimulated Raman gain coefficient is estimated as around 56 cm/GW from the relationship between spontaneous Raman output power and pump power. A temperature dependence of Raman frequency shift of about 0.6 GHz/K is measured. The spontaneous anti-Stokes Raman scattering output peak at 1253 nm is also observed with around 35 mW pump. Stimulated Raman amplification measurement is carried out with a SLED white light source as probe signal. With 35 mW pump power, around 0.6 dB gain has been determined with both pump and probe being TE polarized. KW - silicon waveguide KW - Raman Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15248 SP - 281 EP - 289 PB - Society of Photo-Optical Instrumentation Engineers (SPIE) ER - TY - JOUR A1 - Steglich, Patrick A1 - Mai, Christian A1 - Villringer, Claus A1 - Dietzel, Birgit A1 - Bondarenko, Siegfried A1 - Ksianzou, Viachaslau A1 - Villasmunta, Francesco A1 - Zesch, Christoph A1 - Pulwer, Silvio A1 - Burger, Martin A1 - Bauer, Joachim A1 - Heinrich, Friedhelm A1 - Schrader, Sigurd A1 - Vitale, Francesco A1 - De Matteis, Fabio A1 - Prosposito, Paolo A1 - Casalboni, Mauro A1 - Mai, Andreas T1 - Silicon-organic hybrid photonics: an overview of recent advances, electro-optical effects and CMOS integration concepts JF - Journal of Physics: Photonics N2 - In recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon–organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon–organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13882 SN - 2515-7647 VL - 3 IS - 2 ER - TY - GEN A1 - Steglich, Patrick A1 - Villringer, Claus A1 - Pulwer, Silvio A1 - Dietzel, Birgit A1 - Ksianzou, Viachaslau A1 - Schrader, Sigurd T1 - Chip-integrierte photonische Bauelemente T2 - Wissenschaftliche Beiträge 2017 N2 - In unserer hochtechnologisierten Gesellschaft spielt die optische Datenübertragung aufgrund der stetig wachsenden Informationsvielfalt eine immer bedeutendere Rolle. In den Anfängen der Nachrichtentechnik waren Datenraten von wenigen bit/s realisierbar. Heute werden mittels optischer Technologien Übertragungsraten von mehreren Gbit/s umgesetzt. Möglich wird dies durch neue Entwicklungen in der Chip-integrierten Photonik. Beispiele dafür 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. Für die Experimente wird exemplarisch ein photonisches Bauelement genutzt, das aus einem hybriden Silizium-Polymer-Materialsystem besteht. Die Ergebnisse zeigen, dass diese Materialkombination vielversprechend für zukünftige Chip-integrierte photonische Bauelemente mit extrem geringem Energiebedarf ist. N2 - The focus on high-tech in our society makes optical data transmission increasingly important due to the continually growing diversity of information. At the very beginning of integrated photonics, the data rates achieved were only a few bit/s. Today, transfer rates of several Gbit/s are possible due to novel chip-integrated devices such as electro-optical modulators and switches. This trend was made possible due to new developments in the field of Chip-integrated photonics. In this article, we discuss latest developments in the field of chip-integrated photonic devices and describe their experimental characterization. The experimental setup is developed and described in detail. The example used in our experiments is a hybrid silicon-polymer material system. Our results show that the hybrid material approach is a promising candidate for future on-chip integrated photonic devices with low power consumption. Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9426 SN - 0949-8214 VL - 21 SP - 55 EP - 59 ER - TY - GEN A1 - Steglich, Patrick A1 - Ksianzou, Viachaslau A1 - Villringer, Claus A1 - Pulwer, Silvio A1 - Schrader, Sigurd T1 - Theorie der Modenlinienspektroskopie zur optischen Charakterisierung von Polymerschichten T2 - Wissenschaftliche Beiträge 2018 N2 - Die Modenlinienspektroskopie kann zur hochpräzisen Charakterisierung von Polymerschichten bezüglich des Brechungsindex verwendet werden. Das vorliegende Manuskript behandelt die Theorie der Modenlinienspektroskopie und beginnt dabei mit den theoretischen Grundlagen eines planaren Wellenleiters, die zum Verständnis der Modenlinienspektroskopie notwendig sind. Die hier präsentierten expliziten Herleitungen können genutzt werden, um die Modenlinienspektroskopie so zu modifizieren, dass auch die Messung des Pockelseffektes möglich ist. Eine Anwendungsmöglichkeit soll in der zukünftigen Bestimmung des Pockelskoeffizienten bestehen, der für die Weiterentwicklung von polymerbasierten elektrooptischen Modulatoren benötigt wird. Zudem werden der Aufbau und die experimentelle Herangehensweisen beschrieben und die Brechungsindexbestimmung wird exemplarisch am Beispiel einer Wirt-Gast-Polymerschicht demonstriert. N2 - M-Line spectroscopy can be used for high precision measurements of polymer layers. The present manuscript deals with the theory of m-line spectroscopy and thus begins with the theoretical background of a planar waveguide structure, which is necessary for a deeper understanding of m-line spectroscopy. The explicit derivations presented here can be used to modify the m-line spectroscopy in such a way that the measurement of the Pockels effect is also possible. One application is to be obtained in the future configuration of the Pockels coefficients, which is needed to optimize electro-optical modulators. In addition, the set-up and the experimental approach are described. Finally, a host-guest polymer layer is experimentally characterized in terms of the refractive index. Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-10248 SN - 0949-8214 VL - 22 SP - 31 EP - 38 ER -