@inproceedings{HasenstabAdelmannHellmann2013, author = {Hasenstab, Stefan and Adelmann, Benedikt and Hellmann, Ralf}, title = {Laser Cutting of Alumina and Aluminum Nitride with a 500 W Single Mode Fiber Laser}, series = {XXVII. microCAD International Scientific Conference}, booktitle = {XXVII. microCAD International Scientific Conference}, year = {2013}, subject = {Laserschneiden}, language = {en} } @inproceedings{KalmarHellmannRegertetal.2011, author = {Kalm{\´a}r, L{\´a}szl{\´o} and Hellmann, Ralf and R{\´e}gert, Tam{\´a}s and Varga, Zoltan}, title = {Numerical simulation of heat transfer procedure in high power LED modules}, series = {Proceedings of the 12th technical and scientific meeting}, booktitle = {Proceedings of the 12th technical and scientific meeting}, pages = {18 -- 20}, year = {2011}, subject = {Lumineszenzdiode}, language = {en} } @inproceedings{GlaabHellmann2010, author = {Glaab, Johannes and Hellmann, Ralf}, title = {Small-scale low-through UV-C LED disinfection device, in waste processing and recycling}, series = {Proceedings of the XXIV international Scientific conference Miskolc, Ungarn}, booktitle = {Proceedings of the XXIV international Scientific conference Miskolc, Ungarn}, year = {2010}, subject = {Lumineszenzdiode}, language = {en} } @inproceedings{HeilmannHellmann2011, author = {Heilmann, Eva-Maria and Hellmann, Ralf}, title = {Water jet guided laser cutting using a green disc laser}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, year = {2011}, subject = {Wasserstrahlschneiden}, language = {en} } @inproceedings{RungBischoffJaegeretal.2014, author = {Rung, Stefan and Bischoff, Christian and J{\"a}ger, Erwin and Umhofer, Udo and Hellmann, Ralf}, title = {Laser thin film ablation with multiple beams and tailored beam profiles}, series = {Proceedings of SPIE 8967, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XIX}, volume = {8967}, booktitle = {Proceedings of SPIE 8967, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XIX}, year = {2014}, subject = {Laserablation}, language = {en} } @inproceedings{RungRexhepiHellmann2013, author = {Rung, Stefan and Rexhepi, Mal and Hellmann, Ralf}, title = {Beam shaping for enhanced through-put of laser ablation of transparent conductive films}, series = {Proceedings of the XXVII MicroCAD International Scientific Conference}, volume = {2013}, booktitle = {Proceedings of the XXVII MicroCAD International Scientific Conference}, year = {2013}, subject = {Laserablation}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Markus and Belle, Stefan and Hellmann, Ralf}, title = {Detection of unlabeled DNA hybridization with a planar Bragg Grating Sensor}, series = {XXV International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, booktitle = {XXV International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, number = {Section R}, pages = {67 -- 72}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{HeilmannHellmann2011, author = {Heilmann, Eva-Maria and Hellmann, Ralf}, title = {High Speed Fibre Laser Material processing of Stainless Steel Tapes Under Tension}, series = {XXV International MicroCAD Conference - Material Processing Technologies, Miskolc (Hungary), 21-25}, booktitle = {XXV International MicroCAD Conference - Material Processing Technologies, Miskolc (Hungary), 21-25}, year = {2011}, subject = {Lasertechnologie}, language = {en} } @inproceedings{AdelmannHellmann2011, author = {Adelmann, Benedikt and Hellmann, Ralf}, title = {Different modulation schemes in fibre laser cutting}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, pages = {1 -- 6}, year = {2011}, subject = {Laserschneiden}, language = {en} } @inproceedings{AdelmannHellmann2011, author = {Adelmann, Benedikt and Hellmann, Ralf}, title = {DOE based optimization of fibre laser cutting of metals}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, pages = {7 -- 12}, year = {2011}, subject = {Laserschneiden}, language = {en} } @inproceedings{RischHellmann2011, author = {Risch, Anna and Hellmann, Ralf}, title = {Laser induced modification of GZO thin film}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, pages = {69 -- 74}, year = {2011}, subject = {Laser}, language = {en} } @inproceedings{RischHellmann2011, author = {Risch, Anna and Hellmann, Ralf}, title = {ITO thin film laser patterning by picosecond laser}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section K: Material science/Material processing technologies}, pages = {63 -- 68}, year = {2011}, subject = {Laserbearbeitung}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Optical interrogation of chemical and temperature bragg grating sensors using tunable fiber coupled bandpass filter}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section H}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section H}, pages = {25 -- 30}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{BelleRosenbergerHellmann2011, author = {Belle, Stefan and Rosenberger, Manuel and Hellmann, Ralf}, title = {Optical fibre sensing in the production process and storage of biofuels}, series = {Proceeding XXV microCAD, International scientific conference, 2011, Section A}, booktitle = {Proceeding XXV microCAD, International scientific conference, 2011, Section A}, pages = {21 -- 26}, year = {2011}, subject = {Biokraftstoff}, language = {en} } @inproceedings{RosenbergerBelleHellmann2011, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Detection of biochemical reaction and DNA hybridization using a planar bragg grating sensor}, series = {Proceeding SPIE, Vol. 8073, article id: 80730C}, booktitle = {Proceeding SPIE, Vol. 8073, article id: 80730C}, number = {8073}, doi = {10.1117/12.886785}, year = {2011}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RischHuehnleinKnoelletal.2009, author = {Risch, Anna and H{\"u}hnlein, Kristof and Kn{\"o}ll, J{\"u}rgen and Hellmann, Ralf}, title = {Laserscribing of transparent conductive oxides - a comparative study using nanosecond and picosecond pulsed solid state lasers}, series = {Proceedings of the 20st International Scientific Conference, Mittweida, 2009}, booktitle = {Proceedings of the 20st International Scientific Conference, Mittweida, 2009}, year = {2009}, subject = {Festk{\"o}rperlaser}, language = {en} } @inproceedings{KaloumenosAmrheinGlaabetal.2010, author = {Kaloumenos, Mareiki and Amrhein, Frank and Glaab, Johannes and Sauer, Michael and Hellmann, Ralf and Kaloudis, Michael}, title = {Development of a UV-Light Source with Highest Power Density Based on Light Emitting Diode Technology for Applications in Production Engineering, in Production Engineering and manufacturing Systems}, series = {Proceedings of the XXIV International Scientific Conference Miskolc, Ungarn}, booktitle = {Proceedings of the XXIV International Scientific Conference Miskolc, Ungarn}, year = {2010}, subject = {Lumineszenzdiode}, language = {en} } @inproceedings{KalmarHellmannRegertetal.2012, author = {Kalm{\´a}r, L{\´a}szl{\´o} and Hellmann, Ralf and R{\´e}gert, Tam{\´a}s and Varga, Zoltan}, title = {Numerical investigation of unsteady heat transport procedure in high power LED module}, series = {GEP}, volume = {2012}, booktitle = {GEP}, number = {1}, pages = {43 -- 46}, year = {2012}, subject = {Lumineszenzdiode}, language = {en} } @inproceedings{HuehnleinTschirpkeHellmann2010, author = {H{\"u}hnlein, Kristof and Tschirpke, Katrin and Hellmann, Ralf}, title = {Optimisation of laser cutting using design of experiment - A comparative study of cutting thin ceramic layers using a fibre laser and a CO2 laser}, series = {Physics procedia}, volume = {5}, booktitle = {Physics procedia}, number = {Part B}, issn = {1875-3892}, pages = {243 -- 252}, year = {2010}, subject = {Laserschneiden}, language = {en} } @inproceedings{GlaabHellmann2010, author = {Glaab, Johannes and Hellmann, Ralf}, title = {Germicidal potential of ultraviolet-LED emitting different wavelength for the inactivation of indigenous coliform bacteria}, series = {Water research conference, Lissabon, Portugal}, booktitle = {Water research conference, Lissabon, Portugal}, year = {2010}, subject = {Lumineszenzdiode}, language = {en} } @inproceedings{RosenbergerBelleHellmann2009, author = {Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Optical interrogation of bragg grating sensors using tunable fibre based bandpass filter}, series = {Proceedings of the 20st international science conference, Mittweida}, booktitle = {Proceedings of the 20st international science conference, Mittweida}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{BelleScheurichHellmann2009, author = {Belle, Stefan and Scheurich, Steffen and Hellmann, Ralf}, title = {Interrogation water content in organic solvents by planar bragg grating sensors}, series = {Proceedings SENSOR}, booktitle = {Proceedings SENSOR}, number = {Vol. II, P3.2}, isbn = {978-3-9810993-6-2}, pages = {324 -- 329}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{ScheurichBelleHellmannetal.2009, author = {Scheurich, Steffen and Belle, Stefan and Hellmann, Ralf and So, Sik and Sparrow, Ian and Emmerson, Greg}, title = {Application of a silica-on-silicon planar optical waveguide. Bragg grating sensor for organic liquid compound detection}, series = {SPIE Optics an optoelectronics conference, Proceedings of SPIE, Vol. 7356, Prag, CR}, booktitle = {SPIE Optics an optoelectronics conference, Proceedings of SPIE, Vol. 7356, Prag, CR}, number = {7356}, isbn = {978-0819476302}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{ScheurichBelleHellmannetal.2009, author = {Scheurich, Steffen and Belle, Stefan and Hellmann, Ralf and So, Sik and Sparrow, Ian and Emmerson, Greg}, title = {Planar optical waveguide bragg grating chemical sensor for online process control}, series = {3rd integrated optics - sensors, sensing structures and methodes Korbielow, PL}, booktitle = {3rd integrated optics - sensors, sensing structures and methodes Korbielow, PL}, year = {2009}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{KalmarHellmannRegertetal.2012, author = {Kalm{\´a}r, L{\´a}szl{\´o} and Hellmann, Ralf and R{\´e}gert, Tam{\´a}s and Varga, Zoltan}, title = {Numerical investigation of heat transport procedure in high power LED modules}, series = {Proceedings of the XXVI International MicroCAD Conference, Miskolc (Hungary)}, booktitle = {Proceedings of the XXVI International MicroCAD Conference, Miskolc (Hungary)}, pages = {43 -- 46}, year = {2012}, subject = {Lumineszenzdiode}, language = {en} } @inproceedings{BischoffJaegerRungetal.2012, author = {Bischoff, Christian and J{\"a}ger, Erwin and Rung, Stefan and Hellmann, Ralf}, title = {Diffractive beam shaping optics for efficient micromachining}, series = {Proceedings of the LASYS (Internationale Fachmesse f{\"u}r Laser-Materialbearbeitung) - SLT (Stuttgarter Lasertage) 2012}, booktitle = {Proceedings of the LASYS (Internationale Fachmesse f{\"u}r Laser-Materialbearbeitung) - SLT (Stuttgarter Lasertage) 2012}, year = {2012}, subject = {Laserbearbeitung}, language = {en} } @inproceedings{KollerHesslerRosenbergeretal.2012, author = {Koller, Georg and Hessler, Steffen and Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Micro-structured optical waveguide fabrication in PMMA using low frequency reactive ion etching}, series = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, booktitle = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, year = {2012}, subject = {Wellenleiter}, language = {en} } @inproceedings{GirschikofskyRosenbergerBelleetal.2012, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Brutschy, Malte and Waldvogel, Siegfried and Hellmann, Ralf}, title = {α-Cyclodextrin functionalized planar Bragg grating sensor for the detection of small arene traces in solvamt vapour}, series = {14th international meeting on chemical sensors (IMCS 2012)}, booktitle = {14th international meeting on chemical sensors (IMCS 2012)}, isbn = {978-3-9813484-2-2}, doi = {10.5162/IMCS2012/7.5.1}, pages = {646 -- 648}, year = {2012}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RungHellmann2012, author = {Rung, Stefan and Hellmann, Ralf}, title = {Laser scribing of metallized transparent conductive oxide - A comparative study using top hat and Gaussian beam profiles}, series = {Proceedings of the XXVI International MicroCAD Conference - Material Processing Technologies}, booktitle = {Proceedings of the XXVI International MicroCAD Conference - Material Processing Technologies}, year = {2012}, subject = {Laserbearbeitung}, language = {en} } @inproceedings{GirschikofskyRosenbergerBelleetal.2012, author = {Girschikofsky, Maiko and Rosenberger, Manuel and Belle, Stefan and Hellmann, Ralf}, title = {Surface modifications of planar bragg grating refractive index sensors for gas detection}, series = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, booktitle = {Proceedings of the XXVI International MicroCAD Conference - Sensing Technologies, Miskolc (Hungary)}, year = {2012}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{JaegerRaedelBischoffetal.2014, author = {J{\"a}ger, Erwin and R{\"a}del, Ulrich and Bischoff, Christian and Umhofer, Udo and Rung, Stefan and Hellmann, Ralf}, title = {Laser micromachining - parallel processing with multiple top hat beams}, series = {8th International Conference on Photonic Technologies LANE 2014}, booktitle = {8th International Conference on Photonic Technologies LANE 2014}, year = {2014}, subject = {Laserbearbeitung}, language = {de} } @inproceedings{FranzRothRungetal.2021, author = {Franz, Daniel and Roth, Gian-Luca and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Superimposed beam deflection using acousto-optical deflectors in combination with a galvanometer scanner}, series = {Lasers in Manufacturing - LiM 2021}, booktitle = {Lasers in Manufacturing - LiM 2021}, year = {2021}, subject = {Galvanometer}, language = {en} } @inproceedings{SchwarzRungEsenetal.2020, author = {Schwarz, Simon and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Current results on laser-based production of complex optics in glass}, series = {10. Wetzlarer Herbsttagung "Moderne Optikfertigung", 29. - 30. September 2020, Wetzlar}, booktitle = {10. Wetzlarer Herbsttagung "Moderne Optikfertigung", 29. - 30. September 2020, Wetzlar}, year = {2020}, subject = {Laserbearbeitung}, language = {en} } @inproceedings{SchwarzRungEsenetal.2020, author = {Schwarz, Simon and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {UKP-Prozess mit anschließendem CO2-Laserpolieren zur Fertigung komplexer Optiken}, series = {10. Workshop Laserbearbeitung von Glaswerkstoffen}, booktitle = {10. Workshop Laserbearbeitung von Glaswerkstoffen}, year = {2020}, subject = {Linse}, language = {en} } @inproceedings{SauerKeferRuppertetal.2019, author = {Sauer, Theresia and Kefer, Stefan and Ruppert, Wolfgang and Hellmann, Ralf and Kaloudis, Michael}, title = {Integration of Bragg grating sensors in components made of carbon fiber reinforced polymers}, series = {Tagungsband der 20. GMA/ITG-Fachtagung Sensoren und Messsysteme 2019, 25.06.2019 - 26.06.2019, N{\"u}rnberg, Deutschland}, booktitle = {Tagungsband der 20. GMA/ITG-Fachtagung Sensoren und Messsysteme 2019, 25.06.2019 - 26.06.2019, N{\"u}rnberg, Deutschland}, isbn = {978-3-9819376-0-2}, doi = {10.5162/sensoren2019/P3.12}, pages = {806 -- 810}, year = {2019}, abstract = {This contribution discusses the integration of polymer planar Bragg grating sensors (PPBG) into carbon fiber reinforced polymer (CFRP) components. For the first time, it is shown that PPBGs based on cyclic olefin copolymers can be integrated into commercial-grade composites, thereby withstanding the demanding production processes. Pre-impregnated fibers are stacked and partially modified to form a sensor pocket. Afterwards, the CFRP specimen containing the optical sensor is cured in a heated mechanical press for 2 hours at a pressure of 7 bar and a temperature of 120 °C. A subsequent evalutaion of the sensor signal shows a Bragg wavelength shift of 1236 pm and a decline in signal amplitude of -2 dB. Three-point flexural tests of the cured sample reveal a linear behavior of the sensor signal towards external loads. The determined sensitivity in dependence of the CFRP specimen's maximum central deflection is -112 pm/mm, while correlation to the applied force results in a sensitivity of -5 pm/N.}, subject = {Bragg-Reflektor}, language = {en} } @inproceedings{RothEsenHellmann2020, author = {Roth, Gian-Luca and Esen, Cemal and Hellmann, Ralf}, title = {Internal micro structuring of transparent optical polymers by fs laser}, series = {Laser-based Micro-and Nanoprocessing XIV 2020}, volume = {11268}, booktitle = {Laser-based Micro-and Nanoprocessing XIV 2020}, publisher = {International Society for Optics and Photonics}, doi = {10.1117/12.2543487}, pages = {112681L}, year = {2020}, abstract = {Lab-on-chip systems are based on components to transport, mix, separate and analyse small volumes of different fluids. The consecutive integration of more complex functions into a single and compact chip demands on multilayer systems. As the classical production using a stacking and joining of single processed layers is elaborate and limited in terms of multilayer structures, an uprising trend to fabricate those devices is the internal, three dimensional processing of transparent substrates by using ultrashort laser pulses. In this study, we report on the generation of internal hollow architectures created by focused 514nm femtosecond laser pulses inside optical polymer bulk materials of different polymers. The three-dimensional channel layout is implemented by moving the sample using three-dimensional motorized stages, allowing arbitrary complex shaped internal channel architectures. Size and cross sectional shape of a single internal generated microchannel are determined by the intensity distribution of the focal voxel. In particular, we show a comprehensive parameter study to improve this laser process with respect to a higher processing speed and stability.}, subject = {Femtosekundenlaser}, language = {en} } @inproceedings{RothWolfEsenetal.2019, author = {Roth, Gian-Luca and Wolf, Bastian and Esen, Cemal and Hellmann, Ralf}, title = {Generation of internal 3D microfluidic architectures in polymers by fs laser processing}, series = {Lasers in Manufacturing 2019}, booktitle = {Lasers in Manufacturing 2019}, year = {2019}, abstract = {Microfluidic lab on chip systems require components to transport, mix, separate and analyse small volumes of different fluids. In this study, we report on the laser generation of internal hollow architectures created by focused 514 nm femtosecond laser pulses inside PMMA bulk material. Size and cross-sectional shape of a single internal generated microchannel are determined by the intensity distribution inside the focal voxel and can be controlled either by the numerical aperture of the focusing objective or by laser beam shaping. As both approaches are practically limited with respect to the realizable cross-sectional shapes, we present a process based on an internal hatching to expand the achievable channel cross-sections and thereby enable the possibility to create complex 3D shaped internal structures. This process is applied to create fully internal functional microfluidic elements such as mixers which are part of most polymer lab-on-chip systems.}, subject = {Femtosekundenlaser}, language = {en} } @inproceedings{AdelmannHellmann2015, author = {Adelmann, Benedikt and Hellmann, Ralf}, title = {Comparative study of experimentally determined and simulated mechanical strength of fiber laser cut alumina substrates}, series = {Proceedings of the 7th International Congress on Laser Advanced Materials Processing}, volume = {2015}, booktitle = {Proceedings of the 7th International Congress on Laser Advanced Materials Processing}, number = {15}, pages = {1 -- 9}, year = {2015}, subject = {Laserschneiden}, language = {en} } @inproceedings{AdelmannNeumeierSchleieretal.2015, author = {Adelmann, Benedikt and Neumeier, Benedikt and Schleier, Max and Wilmann, Eugen and Hellmann, Ralf}, title = {Optical cutting tear detection system for industrial fiber laser based cutting machines}, series = {Lasers in Manufacturing Conference 2015}, booktitle = {Lasers in Manufacturing Conference 2015}, year = {2015}, subject = {Laserschneiden}, language = {en} } @inproceedings{SchwarzRungEsenetal.2020, author = {Schwarz, Simon and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Manufacturing of optical elements by non-contact laser processing}, series = {Seventh European Seminar on Precision Optics Manufacturing, Proceedings}, booktitle = {Seventh European Seminar on Precision Optics Manufacturing, Proceedings}, number = {11478}, year = {2020}, subject = {Laserbearbeitung}, language = {en} } @inproceedings{SchwarzRungEsenetal.2020, author = {Schwarz, Simon and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {All laser-based fabrication of optical elements}, series = {Proceedings of SPIE 11270, Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XX}, booktitle = {Proceedings of SPIE 11270, Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XX}, year = {2020}, subject = {Ultrakurzzeitlaser}, language = {de} } @inproceedings{SchwarzEsenHellmann2018, author = {Schwarz, Simon and Esen, Cemal and Hellmann, Ralf}, title = {CO2 laser polishing of femtosecond shaped micro-optical components}, series = {3rd Conference on Laser Polishing LaP 2018}, booktitle = {3rd Conference on Laser Polishing LaP 2018}, year = {2018}, subject = {Kohlendioxidlaser}, language = {en} } @inproceedings{SchwarzRungEsenetal.2018, author = {Schwarz, Simon and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Axicon fabrication with ultrashort and CO2 laser}, series = {LPM2018 The 19th International Symposium on Laser Precision Microfabrication}, booktitle = {LPM2018 The 19th International Symposium on Laser Precision Microfabrication}, year = {2018}, subject = {Ultrakurzzeitlaser}, language = {de} } @inproceedings{SchwarzEsenHellmann2018, author = {Schwarz, Simon and Esen, Cemal and Hellmann, Ralf}, title = {Homogeneous low spatial frequency LIPSS on dielectrics generated by beam-shaped femtosecond pulsed laser irradiation}, series = {LPM2018 The 19th International Symposium on Laser Precision Microfabrication}, booktitle = {LPM2018 The 19th International Symposium on Laser Precision Microfabrication}, year = {2018}, subject = {Femtosekundenlaser}, language = {en} } @inproceedings{SchwarzRungHellmann2017, author = {Schwarz, Simon and Rung, Stefan and Hellmann, Ralf}, title = {High quality one-dimensional low spatial frequency LIPSS on sapphire generated by Top-Hat beam shaped ultrashort-pulsed laser}, series = {MultiScience - XXXI. microCAD International Multidisciplinary Scientific Conference}, booktitle = {MultiScience - XXXI. microCAD International Multidisciplinary Scientific Conference}, year = {2017}, subject = {Ultrakurzzeitlaser}, language = {en} } @inproceedings{SchwarzRungHellmann2016, author = {Schwarz, Simon and Rung, Stefan and Hellmann, Ralf}, title = {Simulation of process parameters towards the generation of low spatial frequency LIPSS on dielectric materials}, series = {MultiScience - XXX. microCAD International Multidisciplinary Scientific Conference}, booktitle = {MultiScience - XXX. microCAD International Multidisciplinary Scientific Conference}, year = {2016}, subject = {Laserbestrahlung}, language = {en} } @inproceedings{DudutisPipirasSchwarzetal.2019, author = {Dudutis, Juozas and Pipiras, Jokūbas and Schwarz, Simon and Rung, Stefan and Hellmann, Ralf and Gečys, Paulius}, title = {Bessel beam formation with all laser fabricated axicon - case of glass dicing applications}, series = {COLA 2019, 15th International Conference on Laser Ablation}, booktitle = {COLA 2019, 15th International Conference on Laser Ablation}, year = {2019}, subject = {Laserbestrahlung}, language = {en} } @inproceedings{DudutisPipirasSchwarzetal.2019, author = {Dudutis, Juozas and Pipiras, Jokūbas and Schwarz, Simon and Rung, Stefan and Hellmann, Ralf and Račiukaitis, Gediminas and Gečys, Paulius}, title = {Glass cutting by oblate-tip axicon-generated Bessel-Gaussian beams}, series = {Open Readings, 63rd International Conference for Students of Physics and Natural Sciences}, booktitle = {Open Readings, 63rd International Conference for Students of Physics and Natural Sciences}, year = {2019}, subject = {Laserschneiden}, language = {en} } @inproceedings{FranzMueckeKunzetal.2023, author = {Franz, Daniel and M{\"u}cke, Dominik and Kunz, Tim and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {UV picosecond laser drilling of ABF film material for printed circuit boards using laser burst mode and beam shaping}, series = {International Congress on Applications of Lasers \& Electro-Optics (ICALEO) 2023}, booktitle = {International Congress on Applications of Lasers \& Electro-Optics (ICALEO) 2023}, year = {2023}, abstract = {We report on an experimental study of laser microvia percussion drilling of Ajinomoto build-up film (ABF) material using an ultrashort pulsed laser in the ultraviolet region. In order to optimize the drilling quality in terms of the fabricated taper and microvia diameter, the MHz burst mode is used in combination with both a Gaussian and a top-hat laser intensity distribution. To evaluate the influence of the top-hat beam shape on defocusing, microvias were drilled at different z-positions in the range of 200 μm evenly distributed around the focal plane. The drilling quality was evaluated by laser scanning microscopy and metallography. When using a top-hat beam shape, a reduced taper of down to 26.8 \% on average is achieved compared to a Gaussian beam. For the application of 3 intra-burst pulses, we find an improvement of the taper by 11.6\% compared to the single pulse mode due to the increasing heat accumulation. Using a top-hat beam shape in combination with the MHz burst mode, an 18.2 \% reduction in laser drilling time for a microvia with a similar taper is remarkable, demonstrating the high potential for scaling throughput in electronics manufacturing.}, subject = {Pikosekundenbereich}, language = {en} } @inproceedings{BischoffEsenHellmann2023, author = {Bischoff, Kay and Esen, Cemal and Hellmann, Ralf}, title = {Acceleration of Femtosecond Reductive Laser Sintering of Copper(II) Oxide for Conductive Copper Patterns on Cyclic Olefin Copolymers}, series = {International Congress on Applications of Lasers \& Electro-Optics (ICALEO) 2023}, booktitle = {International Congress on Applications of Lasers \& Electro-Optics (ICALEO) 2023}, year = {2023}, abstract = {We report on the acceleration of femtosecond reductive laser sintering of copper (II) oxide on the surface of transparent cyclic olefin copolymers (COC) by varying the focus size to generate metallic copper (Cu) layers. By using different focusing conditions, different process speeds are achieved, and the structural accuracies are controlled. The formation of Cu lines is observed for different focus sizes at various scan speeds, which is attributed to laser exposure duration and chemical reaction time. The formed lines are categorized and measured by optical microscopy and provide the basis for two-dimensional Cu surfaces. By hatching, high quality conductive films are produced with an increased focus diameter of up to 400 µm at a scan speed of 400 mm/s and a hatch distance of 250 µm resulting in a multiple increased process speed by a factor of thirteen compared to previous research. Using 4-tip measurement , a low sheet resistance of 0.165 Ω/sq was validated on these Cu films, which have an atomic Cu content of 89.5\%.}, subject = {Femtosekundenlaser}, language = {en} }