Patent ID: 8200052

Claim:
An optical device comprising: a passive core layer in which is formed an optical circuit having a refractive index n 2 that is higher than the refractive index of other portions of the passive core layer; an active core layer covering at least a portion of the optical circuit, exhibiting an electro-optical effect, and having a refractive index of n 1 that is higher than the refractive index n 2 of the optical circuit; a lower clad layer having a planar top surface which is adjacent to a bottom surface of the passive core layer, the lower clad layer not extending past the bottom surface of the passive core layer and having a refractive index n 3 that is lower than the refractive index n 2 of the optical circuit; an upper clad layer covering the active and passive core layers and having a refractive index n 5 that is lower than the refractive index n 1 of the active core layer; a lower electrode disposed below the lower clad layer; and an upper electrode disposed on the upper clad layer, entrance and exit portions of the active core layer being tapered, respectively.