Patent ID: 8014636

Claim:
A phase modulation waveguide structure comprising: one of a semiconductor and a semiconductor-on-insulator substrate; a doped semiconductor layer formed over the one of a semiconductor and a semiconductor-on-insulator substrate, said doped semiconductor layer comprising a waveguide rib protruding from a surface thereof not in contact with the one of a semiconductor and a semiconductor-on-insulator substrate; and an electrical contact on top of the waveguide rib, said electrical contact being formed of a material with an optical refractive index close to that of a surrounding oxide layer that surrounds the waveguide rib and the electrical contact and lower than the optical refractive index of the doped semiconductor layer, wherein during propagation of an optical mode within the waveguide structure, the electrical contact isolates the optical mode between the doped semiconductor layer and a metal electrode contact on top of said electrical contact.