SILICON-ON-INSULATOR OPTICAL RIB WAVE-GUIDES - LOSS, MODE CHARACTERISTICS, BENDS AND Y-JUNCTIONS

Optical rib waveguides with widths from 2.73 to 7.73 microns have been formed in SIMOX-based silicon-on-insulator (SOI) structures consistin g of a 4.32 micron thick surface-silicon layer and a 0.398 micron buri ed-oxide layer. The effect of waveguide width, bend radius, y-junction splitting and interface roughness on loss and mode characteristics ha ve been studied at wavelengths of 1.15 and 1.523 microns. The experime ntal results support the hypothesis that certain rib dimensions can le ad to single-mode waveguides even though planar SOI waveguides of simi lar multimicron dimension are multimode. The propagation losses of wav eguides 3.72 microns wide were found toi be nominally 0.0 dB/cm and 0. 4 dB/cm for the TE and TM modes, respectively, when measured at 1.523 microns, where the measurement error was +/- 0.5 dB/cm. This means tha t the loss is experimentally indistinguishable from pure bulk silicon. These results are thought to be the lowest loss measurements for sili con integrated optical waveguides reported to date.