@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} } @article{SchwarzRungEsenetal.2020, author = {Schwarz, Simon and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Rapid fabrication of precise glass axicon arrays by an all laser-based manufacturing technology}, series = {Journal of Laser Applications}, volume = {32}, journal = {Journal of Laser Applications}, number = {1}, pages = {012001 -- 012001}, year = {2020}, subject = {Femtosekundenlaser}, 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} } @article{RothRungEsenetal.2020, author = {Roth, Gian-Luca and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Microchannels inside bulk PMMA generated by femtosecond laser using adaptive beam shaping}, series = {Optics Express}, volume = {28}, journal = {Optics Express}, number = {4}, pages = {5801 -- 5811}, year = {2020}, abstract = {In this contribution, we report on the generation of internal microchannels with basically unlimited channel length inside of PMMA bulk material by femtosecond laser. A precisely controllable and stable circular channel cross section is obtained by using a spatial light modulator to compensate the writing depth depending spherical aberration. Furthermore, the generation of a rotatable elliptical input beam by adaptive optics ensures a fitting of the beam shaping to the writing direction. In this study, we report on both, the effect of the ellipticity of the input beam and the effect of a correction of the spherical aberration on the circularity of the resulting internal microchannels. Moreover, we demonstrate the application of this writing technique by creating microfluidic testing structures inside of a transparent standard polymer.}, subject = {Femtosekundenlaser}, language = {en} } @article{RungBokanSchwarzetal.2020, author = {Rung, Stefan and Bokan, Kevin and Schwarz, Simon and Esen, Cemal and Hellmann, Ralf}, title = {Influence of laser wavelength on the modification of friction between 100Cr6 steel and polytetrafluoroethylene by femtosecond laser-induced periodic surface structures}, series = {Journal of Laser Applications}, volume = {32}, journal = {Journal of Laser Applications}, number = {3}, doi = {10.2351/7.0000036}, pages = {032017-1 -- 032017-6}, year = {2020}, subject = {Femtosekundenlaser}, language = {en} } @article{RothHesslerKeferetal.2020, author = {Roth, Gian-Luca and Hessler, Steffen and Kefer, Stefan and Girschikofsky, Maiko and Esen, Cemal and Hellmann, Ralf}, title = {Femtosecond laser inscription of waveguides and Bragg gratings in transparent cyclic olefin copolymers}, series = {Optics Express}, volume = {28}, journal = {Optics Express}, number = {12}, doi = {10.1364/OE.388364}, pages = {18077 -- 18084}, year = {2020}, abstract = {We report on a femtosecond laser based fabrication technique that enables simultaneous single-step generation of optical waveguides and Bragg gratings inside bulk cyclic olefin copolymers. Due to the nonlinear absorption of focused and spatially modulated laser radiation with a wavelength of 514 nm and a pulse duration of 450 fs, a modification concluding a refractive index shift increase inside the substrate can be achieved. A sophisticated characterization of the generated waveguides by means of an elaborate cut-back method reveals a maximum attenuation of 3.2 dB/cm. Additionally, a Mach-Zehnder interferometer is used to examine the waveguide's refractive index profile. The integrated Bragg grating structures exhibit reflectivities up to 95 \% and a spectral full width at half maximum of 288 pm, at a Bragg wavelength of 1582 nm, whereas the grating period can be deliberately chosen by adapting the fabrication parameters. Thus, due to its increased flexibility and the resulting dispensability of cost-intensive phase masks, this method constitutes an especially promising fabrication process for polymer Bragg gratings inside of bulk materials.}, subject = {Femtosekundenlaser}, language = {en} } @article{RothHaubnerKeferetal.2020, author = {Roth, Gian-Luca and Haubner, Julian and Kefer, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Fs-laser based hybrid micromachining for polymer micro-opto electrical systems}, series = {Optics and Lasers in Engineering}, volume = {137}, journal = {Optics and Lasers in Engineering}, number = {10362}, doi = {10.1016/j.optlaseng.2020.106362}, pages = {1 -- 8}, year = {2020}, abstract = {We report on femtosecond laser direct writing of electrically conductive copper structures on transparent cyclic olefin copolymer based planar optical chips. The process is based on a laser-induced reduction of CuO nanoparticles dissolved in a water-soluble resin. Thus generated conductive copper structures are characterized with respect to their chemical composition and electrical resistivity. In addition, the application of ultrashort laser pulses enables a hybrid micromachining approach comprising ablation of polymer substrates and the fabrication of copper patterns in a single laser processing setup. A possible electro-optical application of this approach is demonstrated by employing the copper structures as an electro-thermal microheater in combination with a polymer planar optical Bragg grating sensor. This, in turn, highlights the potential of generating copious micro-opto-electro-mechanical polymer structures for numerous sensing applications ranging from Lab-on-Chip to environmental applications using the presented hybrid micromachining approach.}, subject = {Femtosekundenlaser}, language = {en} } @article{SchwarzRothRungetal.2020, author = {Schwarz, Simon and Roth, Gian-Luca and Rung, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Fabrication and evaluation of negative axicons for ultrashort pulsed laser applications}, series = {Optics Express}, volume = {Optics Express}, journal = {Optics Express}, number = {28}, pages = {26207 -- 26217}, year = {2020}, subject = {Ultrakurzzeitlaser}, 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} } @article{ZettlKlarEsenetal.2020, author = {Zettl, Julian and Klar, Maximilian and Esen, Cemal and Hellmann, Ralf}, title = {Generation of Rotationally Symmetric Micro Tools using Ultrashort Laser Pulses}, series = {Journal of Laser Micro/Nanoengeneering}, volume = {15}, journal = {Journal of Laser Micro/Nanoengeneering}, number = {2}, doi = {10.2961/jlmn.2020.02.2007}, pages = {118 -- 122}, year = {2020}, abstract = {We report on the fabrication of rotationally symmetrical geometries with ultrashort laser pulses impinging the constant rotating workpiece tangentially. This particular micro machin-ing of geometry is referred to as laser turning, upon which the laser beam is, in general, orient-ed perpendicularly to the rotational axis and tangentially to the work piece. The target geome-try is realized by moving the constantly rotating specimen according to the specified geometry along the focused laser spot. In contrast to mechanical turning, laser turning induces a mini-mized amount of lateral forces through friction that might deteriorate the geometry. In this study, laser turning is examined for stellite as a function of pulse energy and pulse length in the range between 240 fs and 10 ps. Shorter pulse lengths and higher pulse energies increase the achievable ablation rate, while in the pulse length regime of below 1 ps lower roughness is achieved. With a maximum ablation rate of 1.27 mm³/min and a minimum roughness of 0.17 µm, laser turning combines both, fast processing and high surface quality.}, subject = {Ultrakurzzeitlaser}, 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} }