TY - JOUR A1 - Roth, Gian-Luca A1 - Adelmann, Benedikt A1 - Hellmann, Ralf T1 - Cutting and Drilling of SiC Semiconductor by Fiber Laser JF - Journal of Laser Micro/Nanoengineering N2 - We present an experimental study on fiber laser micromachining of 4H-SiC semiconductor. In particular, we optimize the process time for percussion drilling of 440 µm and 330 µm thick wafers with a minimum drilling time of, eg, 7.5 ms being achieved for 330 µm thick wafers. The drilled holes are characterized by a low taper, a high circularity and entry diameters of about 60 µm. For laser cutting, effective cutting speeds of 2 mm/s and 0.63 mm/s are obtained for 330 µm and 440 µm wafer thickness, respectively, with the cut kerf width being 65 µm. Both processes are associated with a good quality that is characterized by no chipping and cracks. The capability of the fiber laser based micromachining process is highlighted by cutting complex micrometer scale inner and outer contours into partially metallized SiC wafers with high quality. KW - Laserschneiden KW - Faserlaser Y1 - 2015 VL - 10 IS - 3 SP - 279 EP - 283 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Circular microchannels inside bulk polymethylmethacrylate generated by femtosecond laser using slit beam shaping JF - Journal of Laser Applications N2 - The authors report on the laser generation of three-dimensional microchannel architectures with fundamentally unlimited channel length by focused 514 nm femtosecond laser pulses inside polymethylmethacrylate bulk material. The three-dimensional channel layout is implemented by moving the specimen using three-dimensional motorized stages, allowing freely chosen complex shaped channel architectures. Based on nonlinear absorption of high intensities around the focal volume, a material modification, including a refractive-index shift is triggered. After laser exposure, the channel is created by a gaseous degradation of exposed areas during an annealing process. Cross section and aspect ratio of thus generated microchannels are strongly influenced by the numerical aperture of the applied objective. To obtain a circular cross-sectional shape, high focusing objectives are necessary. In this report, the authors improve the existing setup by using an elliptical input beam, transforming the intensity distribution of the focal area in the propagation direction to a circular shape even for low and medium numerical aperture focusing objectives and therefore avoiding a small working distance as a limiting factor for processing depth. The elliptical input beam is obtained by insertion of a slit mask in front of the focusing objective. The ellipticity of the incident beam defines the aspect ratio of the generated microchannels. Furthermore, the size of internal microchannels is adjustable by varying laser and annealing process parameters. KW - Femtosekundenlaser Y1 - 2019 VL - 31 IS - 2 SP - 022603-1 EP - 022603-5 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Vertical Microchannels for Microfluidic Multilayer Interconnections in PMMA JF - Journal of Laser Micro/Nanoengineering N2 - We report on laser generation of microchannels by focused femtosecond laser pulses inside PMMA bulk material. This process enables direct fabrication of three dimensional microfluidic channel architectures with generally unlimited channel length. Based on nonlinear ultrashort pulse laser absorption of high intensities around the focal volume, a material modification including a refractive index shift is triggered. After laser exposure the channel is created by a gaseous degradation of exposed areas during an annealing process. The 3D channel layout can easily be realized by moving the specimen using 3D motorized stages, allowing freely chosen complex shaped channel architectures. In this report, the creation of inner lying vertical microchannels is examined. In addition to previously shown horizontal channel architectures vertical channels are necessary to fulfill the definition of an internal three-dimensional microfluidic structure and to create interconnections in multilevel lab on chip devices. The cross section and geometry of vertical channels are strongly influenced by laser parameters such as pulse duration, laser power and writing speed. The influence of these process parameters on the channels diameter is determined and parameters are optimized regarding a controllable, stable and reproducible process. The functionality of vertical microchannels as an interconnection between multilayer microfluidic devices is demonstrated using a Rhodamine B solution. KW - Polymethylmethacrylate KW - Femtosekundenlaser Y1 - 2018 VL - 13 IS - 3 SP - 155 EP - 159 ER - TY - CHAP A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Internal micro structuring of transparent optical polymers by fs laser T2 - Laser-based Micro-and Nanoprocessing XIV 2020 N2 - 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. KW - Femtosekundenlaser Y1 - 2020 U6 - https://doi.org/10.1117/12.2543487 VL - 11268 SP - 112681L PB - International Society for Optics and Photonics ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Microchannels inside bulk PMMA generated by femtosecond laser using adaptive beam shaping JF - Optics Express N2 - 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. KW - Femtosekundenlaser KW - Polymethylmethacrylate Y1 - 2020 VL - 28 IS - 4 SP - 5801 EP - 5811 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - A New Approach to Seal Polymer Microfluidic Devices Using Ultrashort Laser Pulses JF - Journal of Laser Micro/Nanoengineering N2 - We report on the joining of two different transparent thermoplastic polymers using infrared femtosecond laser pulses. Solely being based on nonlinear absorption, the developed micro-welding process for cyclo-olefin copolymers and polycarbonate does not require any intermediate absorbing layers or any surface pre-processing of the welding partners. In addition, it circumvents any heat damages at the outer surfaces of the welding partners. Femtosecond laser welding of cyclo-olefin copolymers is improved by increasing the numerical aperture of the focusing setup resulting in a wider and more homogenous welding cross-section. Welding results are classified by shear strength and fracture modes are analyzed using scanning electron microscopy. Furthermore, we demonstrate, to the best of our knowledge, first results of ultrashort pulse laser welding of transparent polycarbonate, one of the most used transparent polymers. In view of an optimized and stable micro-welding process, we study the influence of laser power and focal position on welding results. The application of ultrashort pulse laser welding for Lab-on-chip fabrication technologies is demonstrated by sealing an ultrashort pulse laser ablated microfluidic device based on a transparent polymer substrate. KW - Femtosekundenlaser KW - Laserschweißen Y1 - 2019 VL - 14 IS - 1 SP - 49 EP - 53 ER - TY - CHAP A1 - Roth, Gian-Luca A1 - Wolf, Bastian A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Generation of internal 3D microfluidic architectures in polymers by fs laser processing T2 - Lasers in Manufacturing 2019 N2 - 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. KW - Femtosekundenlaser Y1 - 2019 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Laser beam microwelding of transparent plastics JF - Joining Plastics N2 - The laser beam welding of transparent plastic components is still a challenge according to the state of the art. A new approach for the joining of two transparent polymeric components using ultrashort laser beam pulses is presented in this report. In this respect, the high peak pulse intensity associated with these lasers permits non-linear absorption processes and thus the production of a locally well-defined heat source in the interior even of a transparent material or at the boundary layer between two transparent substrates. Welding results for transparent plastics of the cycloolefin copolymer and polycarbonate types are shown in this study. In addition to the investigation into the influences of fundamental process parameters on the weld geometry, the leak tightness is demonstrated in this study using a microfluidic system. KW - Laserschweißen Y1 - 2018 VL - 12 IS - 3/4 SP - 2 EP - 8 ER - TY - JOUR A1 - Adelmann, Benedikt A1 - Roth, Gian-Luca A1 - Hellmann, Ralf T1 - Back side ablation of SiC diodes using a q-switched NIR laser JF - Journal of Laser Micro/Nanoengineering KW - Halbleiterdiode KW - NIR Y1 - 2015 VL - 10 SP - 190 EP - 194 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Femtosecond laser direct generation of 3D-microfluidic channels inside bulk PMMA JF - Optics Express N2 - We report on laser direct generation of 3D-microchannels for microfluidic applications inside PMMA bulk material by focused femtosecond pulses. Inner lying channels with cross sectional areas from 100 µm2 to 4400 µm2 are directly created in the volume of a PMMA substrate. Using the presented process, the channel length is fundamentally unlimited. Here we demonstrate a channel length of 6 meters inside a substrate with dimensions of 20 × 20 × 1.1 mm. The formation of the micro channels is based on nonlinear absorption around the focal volume that triggers a material modification. The modified volume can be selectively opened to form the channel by a subsequent annealing process. The cross section of the channel is strongly influenced by the energy distribution and illumination around the focal volume determined by the optical setup and process design. The 3D channel layout can easily be realized by moving the specimen using 3D motorized stage, allowing freely chosen complex shaped channel architectures. Within a comprehensive parameter study, varying laser power, number of multi-passes, writing speed and writing depths, we identify an optimized process in terms of attainable channel height, width and aspect ratio, as well as process stability and reproducibility. The proof of concept for an application in three dimensional microfluidic systems is provided by florescence microscopy using a dye rhodamine B solution in isopropanol. KW - Femtosekundenlaser Y1 - 2017 VL - 25 IS - 15 SP - 18442 EP - 18450 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Rung, Stefan A1 - Hellmann, Ralf T1 - Welding of transparent polymers using femtosecond laser JF - Applied Physics A N2 - Based on nonlinear absorption, we report on laser welding of cycloolefin copolymers without any additional absorption layer employing infrared femtosecond laser. To the best of our knowledge, this is the first report of ultrashort laser welding of this material class, revealing a remarkable high processing speed of 20 mm/s in a single pass mode. Using a 1028 nm laser having a pulse duration of 220 fs at a repetition rate of 571 kHz leads to a welding seam width between 38 and 137 μm, depending on the applied laser average power. The welded joint is characterized by a maximum shear strength of 40 MPa. The experimental results are compared to those reported for femtosecond laser welding of PMMA and to those published for using a Thulium fiber laser. KW - Femtosekundenlaser KW - Laserschweißen Y1 - 2016 VL - 122 IS - 2 SP - 86 EP - 90 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Rung, Stefan A1 - Hellmann, Ralf T1 - Ultrashort pulse laser micro-welding of cyclo-olefin copolymers JF - Optics and Lasers in Engineering N2 - We report on the joining of transparent thermoplastic polymers using infrared femtosecond laser pulses. Due to nonlinear absorption, the developed micro-welding process for cyclo-olefin copolymers does not require any intermediate absorbing layers or any surface pre-processing of the welding partners. In view of an optimized and stable micro-welding process, the influence of the welding speed and focal position on both, the quality and shear force strength are investigated. We highlight that welding seam widths of down to 65 µm are feasible for welding speeds of up to 75 mm/s. However, a variation of the welding speed affects the required focal position for a successful joining process. The shear force strength of the welding seam is determined to 37 MPa, which corresponds to 64% of the shear strength of the bulk material and is not affected by the welding speed. KW - Laserschweißen KW - Femtosekundenlaser Y1 - 2017 VL - 93 SP - 178 EP - 181 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Hessler, Steffen A1 - Kefer, Stefan A1 - Girschikofsky, Maiko A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Femtosecond laser inscription of waveguides and Bragg gratings in transparent cyclic olefin copolymers JF - Optics Express N2 - 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. KW - Femtosekundenlaser KW - Wellenleiter KW - Bragg-Reflektor Y1 - 2020 U6 - https://doi.org/10.1364/OE.388364 VL - 28 IS - 12 SP - 18077 EP - 18084 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Haubner, Julian A1 - Kefer, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Fs-laser based hybrid micromachining for polymer micro-opto electrical systems JF - Optics and Lasers in Engineering N2 - 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. KW - Femtosekundenlaser KW - Bragg-Reflektor Y1 - 2020 U6 - https://doi.org/10.1016/j.optlaseng.2020.106362 VL - 137 IS - 10362 SP - 1 EP - 8 ER - TY - JOUR A1 - Schwarz, Simon A1 - Roth, Gian-Luca A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Fabrication and evaluation of negative axicons for ultrashort pulsed laser applications JF - Optics Express KW - Ultrakurzzeitlaser Y1 - 2020 VL - Optics Express IS - 28 SP - 26207 EP - 26217 ER - TY - JOUR A1 - Lutz, Christian A1 - Roth, Gian-Luca A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Efficient Ultrashort Pulsed Laser Processing by Dynamic Spatial Light Modulator Beam Shaping for Industrial Use JF - Journal of Laser Micro/Nanoengineering N2 - We report on the effect of different transversal beam shapes on the efficiency of ablation processes and the resulting surface characteristics. A possibility to efficiently apply ultrashort pulsed lasers with high average power is beam shaping. By using a cooled reflective based liquid crystal spatial light modulator to generate different spot distributions, it is possible to spatially allocate the available power to avoid excessive high fluences. In our experiments, we determine the optimal fluence to ablate the maximum volume per watt to be in the range of 0.2-0.4 J/cm². Based on this fluence, we increase the number of spots from one to a maximum of twenty to ablate steel in a multilayer scanning-based process. In this context, we examine the influence of different separation distances between the spots on the ablation efficiency and roughness. Subsequently to these investigations, we develop an efficient roughing process with higher ablation rates and a nearly constant roughness. KW - Ultrakurzzeitlaser KW - Lichtmodulator Y1 - 2021 U6 - https://doi.org/10.2961/jlmn.2021.01.2011 VL - 16 IS - 1 SP - 1 EP - 6 ER - TY - JOUR A1 - Roth, Gian-Luca A1 - Kefer, Stefan A1 - Hessler, Steffen A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Integration of Microfluidic and Photonic Components within Transparent Cyclic Olefin Copolymers by Using fs Laser JF - Journal of Laser Micro/Nanoengineering N2 - In this study, we report on the integration of microfluidic channels and optical components by focusing femtosecond laser radiation inside transparent cyclic olefin copolymer (COC) bulk material. An internal localized material modification is triggered based on nonlinear absorption of the laser radiation's high intensities inside the focal volume. The size and shape of the three-dimensional internal modification are controlled by using an adaptive beam shaping setup. The irradiated areas show a positive refractive index shift and can be used as Type I internal optical waveguides. Furthermore, precise control of the spatial pulse-to-pulse distance in combination with a suitable beam profile enables the integration of functional photonic elements, e.g., Bragg gratings, into the waveguide. Thus, it also enables the generation of integrated photonic sensors. In addition, internal fs laser-induced modifications are characterized by a lower thermal stability as compared to the pristine polymer material. By performing a post-annealing process step, internal hollow microstructures are created by gaseous degradation of the exposed areas. Circular microchannels can be generated in a deliberately chosen layout by employing motorized 3D stages. In comparison to etching-based fabrication methods the proposed technology facilitates unlimited channel lengths, as it omits restrictions arising from an etching selectivity and duration. Altogether, this contribution paves the way towards the fabrication of internal three-dimensional optofluidic devices, equipped with a photonic sensor. In contrast, microfluidic and photonic structures are both created by femtosecond laser direct writing inside of transparent polymers. KW - Femtosekundenlaser Y1 - 2021 U6 - https://doi.org/10.2961/jlmn.2021.01.2009 VL - 16 IS - 1 SP - 1 EP - 6 ER - TY - JOUR A1 - Bischoff, Kay A1 - Mücke, Dominik A1 - Roth, Gian-Luca A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - UV-Femtosecond-Laser Structuring of Cyclic Olefin Copolymer JF - Polymers N2 - We report on the laser ablation of cyclic olefin copolymer using an amplified ultrashort pulsed laser in the ultraviolet spectral range. In addition to a high ablation depth per laser-structured layer up to 74 μm at a fluence of 22 J cm−2, an excellent mean roughness 𝑅𝑎 of laser-patterned surfaces down to 0.5 μm is demonstrated. Furthermore, with increasing fluence, increasing ablation efficiencies up to 2.5 mm3 W−1 min−1 are determined. Regarding the quality of the ablation, we observed steep ablation flanks and low debris formation, though for fluences above 10.5 J cm−2 the formation of troughs was observed, being attributed to multiple reflections on the ablation flanks. For comparison, laser ablation was performed under identical conditions with an infrared laser wavelength. The results highlight that UV ablation exhibits significant advantages in terms of ablation efficiency, surface roughness and quality. Moreover, our results show that a larger UV focus spot accelerates the ablation process with comparable quality, paving the way for high-power UV ultrashort pulsed lasers towards an efficient and qualitative tool for the laser machining of cyclic olefin copolymer. The production of complex microfluidics further underlines the suitability of this type of laser. KW - Femtosekundenlaser Y1 - 2022 U6 - https://doi.org/https://doi.org/10.3390/polym14142962 VL - 14 IS - 14 SP - 2962 EP - 2962 ER - TY - CHAP A1 - Kefer, Stefan A1 - Rosenberger, Manuel A1 - Hessler, Steffen A1 - Girschikofsky, Maiko A1 - Belle, Stefan A1 - Roth, Gian-Luca A1 - Schmauss, Bernhard A1 - Hellmann, Ralf T1 - Fabrication and Applications of Polymer Planar Bragg Grating Sensors based on Cyclic Olefin Copolymers T2 - 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) N2 - This contribution reviews recent advancements, current research and possible applications of polymer planar Bragg grating (PPBG) sensors with a focus on the utilization of cyclic olefin copolymer (COC) substrates. COC-PPBGs can be handled and fabricated efficiently by employing a single writing step procedure which features simultaneous generation of waveguide and Bragg grating structure within an injection molded substrate. The resulting photonic structures exhibit an attenuation as low as 1.2 dB cm-1 and a reflectivity up to 99 %. The potential of COC-PPBGs for high-temperature applications is proven by demonstrating temperature measurements up to 160 °C. Moreover, it is possible to employ single PPBGs for multidimensional stress and strain sensing or even three-dimensional shape reconstruction. Due to their excellent properties, it is feasible to integrate COC-PPBGs into commercial-grade carbon fiber reinforced polymer workpieces for structural health monitoring. Furthermore, utilization of appropriate coatings enables functionalization of PPBGs for refractive index sensing and thus biochemical applications. Beside the fabrication and characterization of COC-based PPBGs, this contribution exemplifies and reviews such applications. KW - Bragg gratings , Gratings , Optical waveguides , Temperature sensors , Substrates KW - Optischer Sensor KW - Bragg-Reflektor Y1 - 2020 UR - https://ieeexplore.ieee.org/document/9021801 SN - 978-1-7281-5304-9 U6 - https://doi.org/10.1109/PIERS-Fall48861.2019.9021801 SP - 647 EP - 655 PB - Institute of Electrical and Electronics Engineers ER - TY - JOUR A1 - Kefer, Stefan A1 - Bischoff, Kay A1 - Roth, Gian-Luca A1 - Haubner, Julian A1 - Schmauss, Bernhard A1 - Hellmann, Ralf T1 - Tunable Bulk Polymer Planar Bragg Gratings Electrified via Femtosecond Laser Reductive Sintering of CuO Nanoparticles JF - Advanced Optical Materials N2 - This contribution demonstrates and discusses electrically tunable polymer planar Bragg gratings based on bulk cyclic olefin copolymers. A lithographic single-writing-step method and femtosecond laser reductive sintering of copper(II) oxide nanoparticles are subsequently employed in order to generate buried photonic structures and copper conducting paths on top of the polymer substrate. This way, the necessary number of process steps for fabricating a planar polymer-based electro-optical device is greatly reduced. The response of a fully electrified grating structure follows temperature changes, induced by the copper conducting path, with sensitivities up to −31 pm K−1. Dilatometric measurements show that the specimen's behavior is correlated to the situationally reduced thermal expansion of the bulk polymer substrate. In consequence, the tuning response of the photonic platform follows a second order polynomial, whereas a direct current of 30 mA, which correlates to a power consumption of 18.3 mW, leads to a local temperature increase and a residual Bragg wavelength shift of 19.6 K and −547 pm, respectively. Moreover, the outstanding flexibility of the proposed fabrication concept is underlined by demonstrating alternative conducting path geometries, whereas one of the additional designs is adapted to control the spectral width of the Bragg grating's reflection peak. KW - Bragg gratings KW - CuO nanoparticles KW - cyclic olefin copolymers KW - electro-optic tuning KW - integrated photonics KW - Femtosekundenlaser KW - Bragg-Reflektor Y1 - 2021 UR - https://onlinelibrary.wiley.com/doi/10.1002/adom.202002203 U6 - https://doi.org/https://doi.org/10.1002/adom.202002203 VL - 9 IS - 13 SP - 2002203 EP - 2002203 ER - TY - JOUR A1 - Kefer, Stefan A1 - Pape, Dominik A1 - Roth, Gian-Luca A1 - Hessler, Steffen A1 - Schmauss, Bernhard A1 - Hellmann, Ralf T1 - Micromilling-assisted fabrication of monolithic polymer ridge-type waveguides with integrated photonic sensing structures JF - Optical Materials Express N2 - This study demonstrates and discusses a novel approach for the fabrication and rapid prototyping of monolithic photonic platforms comprising a ridge-type waveguide with integrated sensing structures. First, the bulk injection-molded cyclic olefin copolymer substrates are micromilled in order to define the physical extension of the ridge structure. Cross-sections down to 30 × 30 µm2, exhibiting a mean surface roughness of 300 nm, are achieved with this process. Subsequently, UV radiation is used to modify the ridge structure’s refractive index, which leads to the formation of an optical waveguide. By employing a phase mask, it is possible to equip the photonic platform with a Bragg grating suitable for temperature measurements with a sensitivity of −5.1 pm K-1. Furthermore, an integrated Fabry-Pérot cavity, generated during the micromilling step as well, enables refractive index measurements with sensitivities up to 1154 nm RIU-1. KW - Cyclic Olefin Copolymers KW - Micromilling KW - Bragg Grating KW - Fabry-Pérot Etalon KW - Bragg-Reflektor KW - Optischer Sensor Y1 - 2021 UR - https://www.osapublishing.org/ome/fulltext.cfm?uri=ome-11-8-2389&id=453071 U6 - https://doi.org/https://doi.org/10.1364/OME.425778 VL - 11 IS - 8 SP - 2389 EP - 2400 ER -