THERMOOPTICAL INTERFEROMETRIC SWITCHES FABRICATED BY ELECTRON-BEAM IRRADIATION OF SILICA-ON-SILICON

The thermal stability of channel optical waveguide devices fabricated by electron beam irradiation of plasma-enhanced chemical vapor deposit ion (PECVD) silica-on-silicon is investigated. The degree of stability is dependent on the starting material and on the use of thermal annea ling prior to irradiation. High-temperature postprocessing is shown to reduce modal confinement, increasing losses in waveguide bends and th e coupling coefficient in directional couplers. A low-temperature clad ding process based on a thick MgF2 layer is described, and low-loss th ermooptic Mach-Zehnder interferometric switches are demonstrated.