Low-Birefringence Thermally and Environmentally Stable Slab Waveguide Planarized by Hot Embossing

Abstract

Slab optical waveguides made of “hot-embossing-able” phenyl and methyl silsesquioxane were fabricated. A wide range of refractive index control, from 1.46 to 1.56 at 0.63 µm was attained with high-precision controllability of precursor composition, ±0.5×10-3. A low birefringence, less than 7×10-4, was obtained. Despite the low birefringence, the refractive index of the waveguide was constant after heating at 200°C in an oxidizing atmosphere for 500 h. No difference in refractive index against the prolonged exposure of damp heating at 90°C and 90% relative humidity for 780 h was obtained. Radiative striation due to spin coating was successfully eliminated with planarization of the waveguide with hot embossment using a planar mold. The propagation loss of the planarized slab waveguide was measured to be less than 0.10 dB/cm at 0.63 µm of the transverse-electric mode. This material is considered to be suited for use in a cost-effective waveguide device.