Optical waveguide circuit including multiple passive optical waveguide devices, and method of making same

A method for forming an integrated optical device on a Silicon-On-Insulator (SOI) wafer using a first lithography mask and a second lithography mask, the integrated optical device comprising a first passive optical waveguide device and a second passive optical waveguide device, the SOI wafer including an insulator layer and an upper semiconductor layer formed at least in part from silicon, the method comprising:

• depositing a gate oxide layer on a first portion of the upper semiconductor layer;
• depositing a polysilicon layer formed at least in part from polysilicon on the gate oxide layer;
• projecting light through the first lithography mask onto the polysilicon layer;
• etching the polysilicon layer using a result of the projecting of the first lithography mask to form at least in part the first passive optical waveguide device, wherein a region of static effective mode index is created within the first passive optical waveguide device proximate the etched polysilicon layer;
• projecting light through the second lithography mask onto a second portion of the upper semiconductor layer;
• etching the second portion of the upper semiconductor layer using a result of the projecting of the second lithography mask to form at least in part the second passive optical waveguide device, wherein a value and a position of an effective mode index within the second passive optical waveguide device remains substantially unchanged over time and applies a substantially unchanging optical function to light travelling through the second passive optical waveguide device over the lifetime of the second passive optical waveguide device;
• and
• wherein the optical waveguide forms at least a part of both the first passive optical waveguide device and the second passive optical waveguide device, the optical waveguide couples the first passive optical waveguide device and the second passive optical waveguide device, and the optical waveguide is formed at least in part using the upper semiconductor layer.