Patent ID: 6891985

Claim:
A passive optical waveguide device deposited on a Silicon-on-Insulator (SOI) wafer, the SOI wafer including an insulator layer and an upper semiconductor layer formed at least in part from silicon, the passive optical waveguide device comprising: an optical waveguide formed within the upper semiconductor layer, a gate oxide layer deposited above the upper semiconductor layer, and a polysilicon layer formed at least in part from polysilicon and deposited above the gate oxide layer; wherein the polysilicon layer projects a region of static effective mode index within the optical waveguide, the region of static effective mode index has a different effective mode index than the optical waveguide outside of the region of static effective mode index, the region of static effective mode index has a depth extending within the optical waveguide, and wherein a value and a position of the effective mode index within the region of static effective mode index remains substantially unchanged over time and applies a substantially unchanging optical function to light traveling through the region of static effective mode index over the lifetime of the passive optical waveguide device.