Thermally-grown silicon-dioxide waveguides for use in UV light

Silicon dioxide is transparent in wavelength down to vacuum UV, and high qu ality film is obtained by thermal oxidation of Si substrate. Both of higher -refractive-index guiding core and lower-index optical buffer layers consis t of SiO2 films thermally-grown at different temperatures on Si substrate. Silicon-on-insulator wafer, of which buried oxide layer of 3 mu m thickness had been treated at >1100 degrees C to be optical buffer layer, was held i n steam flow at 800 degrees C for oxidizing top Si layer to form SiO2 guidi ng core layer of 1.2 mu m thickness. Guiding characteristics were measured and showed good agreement with theoretical prediction.