Thermooptic 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 deposition (PECVD) silica-on-silicon is investigated. The degree of stability is dependent on the starting material and on the use of thermal annealing prior to irradiation. High-temperature postprocessing is shown to reduce modal confinement, increasing losses in waveguide bends and the coupling coefficient in directional couplers. A low-temperature cladding process based on a thick MgF/sub 2/ layer is described, and low-loss thermooptic Mach-Zehnder interferometric switches are demonstrated.