Effects of germanium content on sol-gel GeO₂/γ-glycidoxypropyltrimethoxysilane hybrid planar waveguides prepared at low temperature

The effects of germanium content on the structural and optical properties of GeO₂/γ-glycidoxypropyltri-methoxysilane hybrid materials processed by the sol-gel technique are studied for optical waveguide applications. Glass planar waveguide thin films with thickness of more than 2.0 μm are prepared by a single-coating process and low-temperature heat treatment from this high germanium content hybrid material. Multimode light guiding is demonstrated in the hybrid planar waveguide films. The properties of the planar waveguide films such as refractive index, thickness, and transparency as well as structural characterization using the prism coupling technique, atomic force microscopy, thermal gravimetric analysis, UV-visible spectroscopy, and Fourier transform infrared spectroscopy, are systematically studied. These results indicate that the refractive index increases and film thickness decreases with an increase in GeO₂ content, and thus dense, low absorption, and high transparency in the visible range waveguide films can be obtained at a low temperature. Waveguide propagation characteristics, at 632.8 and 1550 nm, are studied. The propagation loss of the hybrid waveguide film with a GeO₂ content of 0.3 M is measured to be 1.2 dB/cm at the wavelength of 1550 nm. © 2004 American Vacuum Society.