Patent ID: 7120338

Claim:
An optical waveguide coupler having a tunable coupling coefficient, said coupler comprising: a first waveguide and a second waveguide comprising first and second cores respectively, said first and second cores separated by cladding in an evanescent coupling region, said first and second waveguides supporting respective first and second spatial modes, wherein said first and second waveguides are comprised of semiconductor having a distribution of free carriers, and said cladding comprises a dielectric material that electrically isolates the first and second waveguides from each other, said first waveguide comprising an optical path in a resonant cavity; a first electrode electrically connected to said first waveguide; a second electrode electrically connected to said second waveguide; and a variable voltage source connected between first and second electrodes; wherein the distributions of free carriers are responsive to application of said voltage such that index of refraction variations can be introduced in said first waveguide to increase or decrease confinement of said first spatial mode and alter overlap of said first and second spatial modes in said cladding of said coupling region thereby changing the coupling coefficient between said waveguides from a first value to a second value.