Patent ID: 6842546

Claim:
An integrated optical circuit, comprising: an optical waveguide located on a Silicon-on-Insulator (SOI) wafer, wherein the optical waveguide is formed from an upper semiconductor layer of the SOI wafer, a gate oxide layer deposited on the upper semiconductor layer, and a polysilicon layer formed at least in part from polysilicon and deposited on the gate oxide layer, wherein the semiconductor layer is formed at least in part from silicon; and an evanescent coupling region formed at least in part from a gap portion that optically couples light to the upper semiconductor layer of the optical waveguide using the evanescent coupling region, wherein light can be coupled from outside of the passive optical waveguide device via the evanescent coupling region into the optical waveguide, and wherein light can be coupled from the optical waveguide through the evanescent coupling region out of the passive optical waveguide device; 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, 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 travelling through the region of static effective mode index within the optical waveguide over the lifetime of the passive optical waveguide device.