Synthesis of polysilisiquioxane used as core layer material of optical waveguide

Abstract

Colorless and transparent polysilisiquioxane was synthesized using non-hydrolytic sol–gel process. A high degree of poly-condensation and a lower remnant ratio of Si–OCH₃ were calculated by ²⁹Si NMR and ¹H NMR, respectively. After spin-coating, subsequently UV and thermal curing, free-cracked thin films were obtained. The properties of the free-cracked thin films were measured by a prism coupler and thermal analysis system. The refractive index increased to 1.5495 (1,310 nm TE) and 1.5468 (1,550 nm TE), respectively, with the increasing of phenyltrimethoxysilane content to 20 mol%. Birefringence was below 0.0005. The thermo-optic coefficient was about −2.8 × 10⁻⁴ °C⁻¹. The optical loss was 0.20 dB cm⁻¹ at 1,310 nm and 0.75 dB cm⁻¹ at 1,550 nm, which was very important for core layer material of optical waveguide. The results of Thermo-Gravimetric Analysis indicated an excellent thermal stability. All of these properties imply that it will be a promising core layer material of optical waveguide.