Optical waveguide, method of making the same and integrated optical device

摘要

An optical waveguide 3 comprises a substrate like a Si substrate having a projection with a flat surface and inclined side surfaces thereon, a buffer layer having a refractive index of n0 formed on lower surfaces of the substrate, a secondary buffer layer having a refractive index of n0 formed on the buffer layer, a core waveguide having a refractive index of n1 formed on the secondary buffer layer and a cladding layer having a refractive index of n0 covering the core waveguide. The flat surface of the projection 31 is exposed through an opening. The secondary buffer layer controls a transmission loss increase caused by partial thickness differences of the ground buffer layer or scattering by scratches or strains created by the grind.