Patent ID: 6904186

Claim:
An optical modulator for modulating light propagating in a three-dimensional optical waveguide by applying a voltage on said waveguide, said modulator comprising; a three-dimensional optical waveguide having at least a pair of branched portions and a recombining portion of said branched portions and radiating light of off mode; a slab optical waveguide guiding said light of off-mode, wherein said slab optical waveguide has a thickness of 20 μm or smaller; a modulating electrode for applying a signal voltage and a direct current bias on said three-dimensional optical waveguide to modulate light propagating in said three-dimensional optical waveguide; a photo detector for receiving light radiated from said slab optical waveguide and providing an output; and a controlling unit for varying said direct current bias based on said output from said photo detector so as to control the operational point of said modulator.