@article{GoldenbergKoehlerKahleetal.2020, author = {Goldenberg, Leonid and K{\"o}hler, Mathias and Kahle, Olaf and Dreyer, Christian}, title = {Impact of inorganic nanoparticles on optical properties of low refractive index waveguiding polymers}, series = {Optical Materials Express}, volume = {10}, journal = {Optical Materials Express}, number = {11}, issn = {2159-3930}, doi = {10.1364/OME.405700}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13521}, pages = {2987 -- 2997}, year = {2020}, abstract = {The objective of this work is to improve the optical properties of low refractive index polymers used for waveguide by introduction of inorganic nanoparticles. Copolymers of fluorinated monomers and glycidyl methacrylate are used. Introduction of SiO2 nanoparticles into polymer matrix is performed by direct mixing; copolymerization with SiO2 nanoparticles modified by monomer, and in situ sol-gel formation of SiO2 during photochemical cross-linking and annealing catalyzed by photoacid generator. It is demonstrated that nanoparticles are able to decrease thermo-optic coefficient. It is also possible to fabricate waveguiding layers by direct introduction of nanoparticles without compromising of optical propagation losses.}, language = {en} } @article{GoldenbergKoehlerDreyer2021, author = {Goldenberg, Leonid and K{\"o}hler, Mathias and Dreyer, Christian}, title = {SiO2 Nanoparticles-Acrylate Formulations for Core and Cladding in Planar Optical Waveguides}, series = {Nanomaterials}, volume = {11}, journal = {Nanomaterials}, number = {5}, publisher = {MDPI}, issn = {2079-4991}, doi = {10.3390/nano11051210}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14057}, year = {2021}, abstract = {A combination of acrylate formulations and SiO2 nanoparticles is investigated with the aim to improve the optical properties of low-refractive index polymers that are used for the fabrication of planar optical waveguides. A decrease in refractive index and also in the thermo-optic coefficient of nanocomposite materials is clearly demonstrated, while some formulations exhibit an increase in the glass transition temperature. The possibility of using these nanocomposite materials to fabricate waveguiding layers with low optical propagation losses at telecommunication wavelengths around 1550 nm is also shown. The nanomaterials can be applied in optical microchips on polymer platforms.}, language = {en} } @article{DreyerMotocKoehleretal.2023, author = {Dreyer, Christian and Motoc, Dana Luca and Koehler, Mathias and Goldenberg, Leonid}, title = {UV LED Curable Perfluoropolyether (PFPE)-Urethane Methacrylate Transparent Coatings for Photonic Applications: Synthesis and Characterization}, series = {Polymers}, volume = {15}, journal = {Polymers}, number = {14}, publisher = {MDPI}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19139}, pages = {1}, year = {2023}, abstract = {The contribution aims to bring forth a novel synthesis route in developing transparent UV LED-curable coatings accounting for various exposure options. A selection of perfluoropolyether (PFPE)-urethane methacrylate and acrylate resins, free-radical photo-initiator Omnirad 2100, and two distinct silane-based crosslinking agents were blended under a weight ratio of 75:20:5 (without crosslinker) and 70:15:5:10, respectively. The coatings were cured under a UV LED 4 × 3 matrix light emitting source, in a chamber under a controlled atmosphere, by means of an in-house developed conveyor belt type platform, at different conveyor belt speeds (5, 50, 150, 250, and 500 mm/s). The morphologies of fabricated coatings were characterized by FTIR revealing high conversion rates (e.g., from 98 to 100\%) for increased exposure time as a result of the 5 or 50 mm/s values, on all combinations. Dynamic-mechanical and optical properties of UV LED-cured transparent coatings were also investigated. A negative shift of the glass transition temperature values with a decrease in exposure time, in all combinations, from about 60 °C to 30 °C, along with storage moduli lowering in the glassy plateau further favors higher exposure times for curing. The refractive indices of poly-mers were from 1.38 to 1.40, whereas the thermo-optic coefficients are showing minor changes around the value of 2.55∙10-4 K-1.}, language = {en} }