High Refractive Index Inorganic-Organic Hybrid Materials for Photonic Applications
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1007-S01-02
High Refractive Index Inorganic-organic Hybrid Materials for Photonic Applications Pélagie Declerck1, Ruth Houbertz1, Georg Jakopic2, Sven Passinger3, and Boris Chichkov3 1 Hybridpolymere (ORMOCER®) für Mikrosysteme, Fraunhofer Institut Silicatforschung, Neunerplatz 2, Würzburg, 97082, Germany 2 JOANNEUM RESEARCH Forschungsgesellschaft mbH., weiz, 8160, Austria 3 Laser Zentrum Hannover e.V., Hannover, 30419, Germany
ABSTRACT High refractive index materials are attractive for many photonic elements. For example, 3D photonic bandgap (PBG) materials have been proposed as the basis of many devices. In order to create complete 3D PBGs, materials enabling high refractive index contrast are needed. We here report on novel high refractive index hybrid polymers. They were synthesized by hydrolysis/polycondensation reactions of organo-alkoxysilanes and Ti alkoxide precursors, resulting in organically modified inorganic-oxidic pre-polymer resins. These can be organically cross-linked by one- or two-photon polymerization (2PP). The latter method enables the writing of arbitrary 3D structures. The introduction of Ti into the inorganic-oxidic network accounts for an increase in the material’s refractive index, which could be varied between 1.62 and 1.8. Optical properties such as refractive index and absorption losses were determined on an exemplary material system in the lower refractive index range. The influence of the processing parameters on the degree of organic polymerization, and the refractive index of these novel high index materials was investigated in particular. 3D photonic crystal structures were written for the first time in a high-refractive index hybrid polymer. INTRODUCTION Three dimensional (3D) photonic bandgap materials [1] are expected to be the basis of many devices. In order to create complete 2- or 3D photonic PBGs [2,3], materials with high refractive index contrast are needed. Low-cost fabrication of photonic elements have been made possible by polymers. However, their refractive indices are usually relatively low. Introduction of bromine into polymers is known to increase their refractive index [4], but these are hazardous materials and thus have to be avoided. In addition, purely organic polymers applied for optics are optical packages such as, for example, polymethymethacrylate (PMMA), often chemically, mechanically, and thermally not very stable. Inorganic-organic hybrid polymers have generated a growing interest due to their wide range of applications in optics, electronics, mechanics, energy, and biology, to mention only a few [5-9]. ORMOCERs®1 which belong to class II hybrid materials [10-11], are synthesized by controlled hydrolysis and polycondensation reactions of inorganic condensable units (-Si-OR) from organo-alkoxysilane precursors resulting in an inorganic-organic network. The ≡[Si-O-Si]n≡ units are functionalized by organic groups which can act as network modifier 1
registered by the Fraunhofer-Gesellschaft für Angewandte Forschung e.V.
and/or network former. The latter
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