Patent ID: 7020371

Claim:
An integrated waveguide structure comprising: a first waveguide for weakly confining a first optical signal propagating therein, said first waveguide having an optical propagation axis and a characteristic length as measured along said optical propagation axis, said first waveguide disposed on a substrate; a first trench formed within said substrate on a first side of said first waveguide, said trench having a characteristic length as measured parallel to said optical propagation axis of the first waveguide, said characteristic length of the trench being substantially shorter than said characteristic length of the first waveguide; a second trench formed on a second side of the first waveguide, said second trench disposed opposite said first trench, said second trench having a characteristic length approximately equal to that of the first trench; a third trench formed within said substrate on a first side of said first waveguide, said third trench having a characteristic length as measured parallel to said optical propagation axis of the first waveguide, said characteristic length of the third trench being substantially shorter than said characteristic length of the first waveguide; and, a fourth trench formed on a second side of the first waveguide, said fourth trench disposed opposite said third trench, said fourth trench having a characteristic length approximately equal to that of the third trench, said trenches having a low index of refraction material therein, said characteristic length of the first trench, said characteristic length of the third trench, and a distance between the first trench and the second trench being chosen to provide a predetermined polarization characteristic to the waveguide structure.