Patent ID: 7522784

Claim:
An asymmetric directional coupler formed in an electro-optic material for directing light transmitted into the directional coupler to be coupled from a first optical waveguide to a second optical waveguide at any selected optical power from full coupling to full attenuation comprising: a first optical waveguide having a first propagation constant; a second optical waveguide having a second propagation constant different from the first propagation constant sufficient to cause an accumulated optical phase difference between them; the first and second optical waveguides being disposed in close proximity to each other over a selected length to permit evanescent coupling between them; a first signal electrode associated with the first optical waveguide for receiving a control voltage to determine a percentage of optical coupling between the first and second optical waveguides; a second signal electrode associated with the second optical waveguide for receiving a control voltage approximately complementary to the first electrode control voltage for determining a percentage of optical coupling between the first and second waveguides; wherein the length and first and second propagation constants are selected so that light is coupled from the first optical waveguide to the second optical waveguide in a percentage between full coupling and full attenuation when the voltage applied to both the first and second electrodes is zero, such that less than 81% of a total switching voltage is required to switch to full coupling or to full attenuation.