Patent ID: 7668223

Claim:
A photonic semiconductor device comprising: a substrate having a lower surface and an upper surface; one or more layers including: at least one buffer layer having a lower surface that is in contact with the upper surface of the substrate; one or more multi quantum well (MQW) and confinement heterostructure (SCH) layers, one layer of said one or more MQW and SCH layers having a lower surface that is in contact with an upper surface of said at least one buffer layer; at least one grating layer having a lower surface that is in contact with an upper surface of said one or more MQW and SCH layers, at least a portion of the grating layer having a periodically varying refractive index region therein; one or more cladding and contact layers, one of said one or more cladding and contact layers having a lower surface that is in contact with an upper surface of said at least one grating layer; a waveguide ridge formed in at least said one or more cladding and contact layers; a first trench formed at least in said one or more cladding and contact layers and in said at least one grating layer, said first trench being located on a side of the waveguide ridge and extending in a direction substantially parallel to said waveguide ridge alongside said waveguide ridge, the first trench having at least a first width along a first portion thereof and a second width along a second portion thereof, the second width being greater than the first width; and a second trench formed at least in said one or more cladding and contact layers and in said at least one grating layer, said second trench being located on a side of the waveguide ridge opposite the side of the waveguide ridge on which the first trench is located, the second trench extending in a direction substantially parallel to said waveguide ridge alongside said waveguide ridge, the second trench having at least a first width along a first portion thereof and a second width along a second portion thereof, the second width along the second portion of the second trench being greater than the first width along the first portion of the second trench, wherein the first width of the first portions of the first and second trenches is substantially constant throughout portions of the photonic semiconductor device and wherein the second width of the second portions of the first and second trenches varies in other portions of the photonic semiconductor device over a plurality of widths, each of said plurality of widths being larger than the first width.