@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{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} } @inproceedings{BischoffMueckeEsenetal.2023, author = {Bischoff, Kay and M{\"u}cke, Dominik and Esen, Cemal and Hellmann, Ralf}, title = {UV-Femtosecond-Laser Structuring of Silicon Carbide}, 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 ultraviolet ultrashort pulsed laser processing of silicon carbide. Laser ablated cavities are evaluated with respect to their ablation rates, surface roughness and overall quality by varying the laser pulse fluence. Using this type of laser, high edge quality and surface roughness down to 107 nm can be achieved with an ablation efficiency of up to 0.228 mm 3 W -1 min -1. Functional surfaces are produced by generating laser induced periodic surface structures. The comparison with infrared wavelength underlines the advantages of the ultraviolet wavelength for laser micro machining this material. Significant differences with respect to the measured ablation depths and roughness as well as generated micro-and nanostructures appear. While infrared ablation is dominated by a chipping mechanism above a critical fluence of 9.93 Jcm -2 , higher ablation rates are observed with strong quality losses at the same time. In comparison to the infrared emission wavelength, in general , a significantly higher processing quality is achieved with the ultraviolet emission wavelength. In addition, the influence of spot size and repetition rate in UV processing is investigated. By increasing these parameters, a process acceleration without quality losses is enabled. The generation of a sophisticated microstructure exemplifies the advantages of processing silicon carbide with the UV laser reported here.}, subject = {Femtosekundenlaser}, language = {en} } @inproceedings{SommerHornungEsenetal.2024, author = {Sommer, David and Hornung, Simon and Esen, Cemal and Hellmann, Ralf}, title = {Optimization of mechanical properties of additive manufactured IN 718 parts combining LPBF and in-situ high-speed milling}, series = {Laser 3D Manufacturing XI}, booktitle = {Laser 3D Manufacturing XI}, editor = {Gu, Bo and Chen, Hongqiang}, publisher = {SPIE}, doi = {http://dx.doi.org/10.1117/12.3000952}, year = {2024}, subject = {Hochgeschwindigkeitsfr{\"a}sen}, language = {en} }