@article{KeferPapeBischoffetal.2024, author = {Kefer, Stefan and Pape, Natalie and Bischoff, Kay and Schmauss, Bernhard and Hellmann, Ralf}, title = {Lattice-Like Waveguides With Integrated Bragg Gratings in Planar Cyclic Olefin Copolymers}, series = {Journal of Lightwave Technology}, volume = {42}, journal = {Journal of Lightwave Technology}, number = {18}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, issn = {0733-8724}, doi = {10.1109/JLT.2023.3328323}, pages = {6302 -- 6311}, year = {2024}, abstract = {This contribution demonstrates femtosecond laser direct writing of lattice-like waveguides in planar cyclic olefin copolymer substrates. Based on numerical simulation and experimental near-field analysis, stable single-mode waveguiding around wavelengths of 1550 nm is demonstrated. The waveguiding mechanism is based on a hexagonal array of laser-induced, positive refractive index modification lines. Thus, the lateral extension of the guided mode can be adapted by varying the fabrication parameters and, in consequence, the resulting cross-sectional arrangement of the refractive index perturbations. With an optical attenuationof 2.2 dB·cm-1 around 1550 nm, the fabricated waveguides are well-suited for on-chip integrated photonic devices. Moreover, the waveguides can also be equipped with Bragg gratings to enable the application of the photonic platform as a sensing device. Dependingon their length, the Bragg grating structures exhibit reflectivities ofup to 99\% and spectral widths down to 0.3 nm. The flexibility of the fabrication process and the sensing capabilities of the lattice-like waveguides with integrated Bragg gratings are underlined by an exemplary application study demonstrating a relative pressure sensor. For that, a photonic platform is micromilled to generate a 300 µm thick diaphragm and a reference pressure chamber. The strain introduced to the diaphragm by external pressure changes can then be quantified by the integrated photonic structures.This way, absolute pressure sensitivities of up to 38 pm·kPa-1 can be achieved in a relative pressure range from -60 to 100 kPa. The newly-developed lattice-like waveguides with integrated Bragggratings are therefore well-suited for the realization of novel and adaptable photonic devices and sensors.}, subject = {Wellenleiter}, language = {en} } @article{BischoffKeferWienkeetal.2023, author = {Bischoff, Kay and Kefer, Stefan and Wienke, Alexander and Overmeyer, Ludger and Kaierle, Stefan and Esen, Cemal and Hellmann, Ralf}, title = {Integration of Bragg gratings in aerosol-jetted polymer optical waveguides for strain monitoring capabilities}, series = {Optics Letters}, volume = {48}, journal = {Optics Letters}, number = {7}, doi = {https://doi.org/10.1364/OL.481801}, pages = {1778 -- 1781}, year = {2023}, abstract = {We demonstrate and discuss the integration of Bragg gratings in aerosol-jetted polymer optical waveguides, produced in the optical assembly and connection technology for component-integrated bus systems (OPTAVER) process. By using a femtosecond laser and adaptive beam shaping, an elliptical focal voxel generates different types of single pulse modification by nonlinear absorption in the waveguide material, which are arranged periodically to form Bragg gratings. Integration of a single grating structure or, alternatively, an array of Bragg grating structures in the multimode waveguide yields a pronounced reflection signal with typical multimodal properties, i.e., a number of reflection peaks with non-Gaussian shapes. However, the main wavelength of reflection, located around 1555 nm, is evaluable by means of an appropriate smoothing algorithm. When loaded by mechanical bending, a pronounced Bragg wavelength shift of this reflected peak up to 160 pm is detected. This demonstrates that the additively manufactured waveguides can be used not only for signal transmission but also as a sensor.}, subject = {Bragg-Reflektor}, language = {de} }