@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{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{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{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{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{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{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{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{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{SommerPetersEsenetal.2025, author = {Sommer, David and Peters, Maximilian and Esen, Cemal and Hellmann, Ralf}, title = {Influence of in-situ high-speed milling within a hybrid additive manufacturing approach on the fatigue behaviour of Inconel 718 lattice structures}, series = {Lasers in Manufacturing, M{\"u}nchen, Juni 2025}, booktitle = {Lasers in Manufacturing, M{\"u}nchen, Juni 2025}, year = {2025}, abstract = {As lattice structures in various designs are used in additive manufacturing for lightweight components, the mechanical characterisation and fracture behaviour is of upmost importance for their industrial application. In this study, the fatigue behaviour of Inconel 718 lattice structures is evaluated, comparing sole PBF-LB/M to a hybrid additive manufacturing process combining PBF-LB/M with in-situ high-speed milling. At first, the static and dynamic mechanical load behaviour of different packing densities is analysed, determining the compressive strength and the endurance limit. Secondly, hybrid additive manufactured components are compared to PBF-LB/M built parts with respect to these mechanical properties, revealing improved compressive properties and modified regimes of fatigue. In addition, differences in fracture behaviour are qualified by fractographic and surface analysis. Overall, it can be summarized that the mechanical load characteristics, especially the fatigue behaviour, are improved for hybrid additively manufactured components with a superior surface quality of Ra < 1 µm.}, subject = {Hochgeschwindigkeitsfr{\"a}sen}, language = {de} }