Patent ID: 7206487

Claim:
A waveguide photodetector comprising: a first clad layer disposed on a substrate; a core layer of a small thickness disposed on the first clad layer capable of absorbing a light beam size of up to 4 μm and; a second clad layer disposed on the core layer; and at least one subsidiary layer having a predetermined thickness is inserted in each of the first clad layer and the second clad layer, wherein the at least one subsidiary layer in each of the first and second clad layers is placed at a predetermined position inside the respective one of the first or second clad layers such that the at least one subsidiary layer allows absorption of a light beam size up to 10 μm, and wherein the at least one subsidiary layer in each of the first and second clad layers is formed of material different from the material of the respective first or second clad layer and has a higher refractive index than the refractive index of the respective first or second clad layer.