TY - CHAP A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Hellmann, Ralf T1 - High quality one-dimensional low spatial frequency LIPSS on sapphire generated by Top-Hat beam shaped ultrashort-pulsed laser T2 - MultiScience - XXXI. microCAD International Multidisciplinary Scientific Conference KW - Ultrakurzzeitlaser Y1 - 2017 ER - TY - CHAP A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - All laser-based fabrication of optical elements T2 - Proceedings of SPIE 11270, Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XX KW - Ultrakurzzeitlaser KW - Kohlendioxidlaser KW - Femtosekundenlaser Y1 - 2020 ER - TY - CHAP A1 - Marx, Jan A1 - Esen, Cemal A1 - Lutz, Christian A1 - Hellmann, Ralf A1 - Ostendorf, Andreas T1 - Holographic tuning of physical axicons N2 - Axicon generated Bessel beams are a popular tool for high aspect ratio precision laser drilling. Spot diameter and working distance are given by the geometric parameters of the axicon and the wavelength used. Thus, it is difficult to manipulate the beam shape of a Bessel beam for a given setup. Spatial light modulators (SLMs) overcome limitations in flexibility. However, due to the limited phase shift of SLMs, only Bessel beams with flat cone angles and large focal length can be generated. In this contribution, an approach for generating Bessel beams with a shorter, but tunable focal length is presented. A physical axicon was combined with an SLM. A holographic image of a negative axicon is put on the SLM to generate a ring beam, which is focused by a subsequent physical axicon to get a small focal diameter. Thus, different sized high aspect ratio micro holes can be drilled without using any moving components. KW - Bessel beam KW - Micro drilling KW - Axicon KW - Spatial light modulator KW - Beam shaping KW - Bessel-Bündel KW - Axicon KW - Strahlformung, Laser Y1 - 2023 VL - 2023 IS - 154 SP - 1 EP - 9 PB - LiM 2023 Proceedings ER - TY - CHAP A1 - Kalmár, László A1 - Hellmann, Ralf A1 - Régert, Tamás A1 - Varga, Zoltan T1 - Numerical investigation of unsteady heat transport procedure in high power LED module T2 - GEP KW - LED module KW - Lumineszenzdiode Y1 - 2012 VL - 2012 IS - 1 SP - 43 EP - 46 ER - TY - CHAP A1 - Girschikofsky, Maiko A1 - Rosenberger, Manuel A1 - Belle, Stefan A1 - Brutschy, Malte A1 - Waldvogel, Siegfried A1 - Hellmann, Ralf T1 - α-Cyclodextrin functionalized planar Bragg grating sensor for the detection of small arene traces in solvamt vapour T2 - 14th international meeting on chemical sensors (IMCS 2012) KW - sensor detection KW - Bragg-Reflektor Y1 - 2012 SN - 978-3-9813484-2-2 U6 - https://doi.org/10.5162/IMCS2012/7.5.1 SP - 646 EP - 648 ER - TY - CHAP A1 - Koller, Georg A1 - Hessler, Steffen A1 - Rosenberger, Manuel A1 - Belle, Stefan A1 - Hellmann, Ralf T1 - Micro-structured optical waveguide fabrication in PMMA using low frequency reactive ion etching T2 - Proceedings of the XXVI International MicroCAD Conference – Sensing Technologies, Miskolc (Hungary) KW - waveguide fabrication KW - Wellenleiter Y1 - 2012 ER - TY - CHAP A1 - Girschikofsky, Maiko A1 - Rosenberger, Manuel A1 - Belle, Stefan A1 - Hellmann, Ralf T1 - Surface modifications of planar bragg grating refractive index sensors for gas detection T2 - Proceedings of the XXVI International MicroCAD Conference – Sensing Technologies, Miskolc (Hungary) KW - surface modification KW - Bragg-Reflektor Y1 - 2012 ER - TY - CHAP A1 - Bischoff, Christian A1 - Jäger, Erwin A1 - Rung, Stefan A1 - Hellmann, Ralf T1 - Diffractive beam shaping optics for efficient micromachining T2 - Proceedings of the LASYS (Internationale Fachmesse für Laser-Materialbearbeitung) – SLT (Stuttgarter Lasertage) 2012 KW - micromachining KW - Laserbearbeitung Y1 - 2012 ER - TY - CHAP A1 - Kalmár, László A1 - Hellmann, Ralf A1 - Régert, Tamás A1 - Varga, Zoltan T1 - Numerical investigation of heat transport procedure in high power LED modules T2 - Proceedings of the XXVI International MicroCAD Conference, Miskolc (Hungary) KW - heat transport procedure KW - Lumineszenzdiode KW - Wärmeübertragung Y1 - 2012 SP - 43 EP - 46 ER - TY - CHAP A1 - Rung, Stefan A1 - Hellmann, Ralf T1 - Laser scribing of metallized transparent conductive oxide – A comparative study using top hat and Gaussian beam profiles T2 - Proceedings of the XXVI International MicroCAD Conference – Material Processing Technologies KW - laser scribing KW - Laserbearbeitung KW - Laserritzen Y1 - 2012 ER -