Optical device and optical module

Abstract

An optical device includes an active layer disposed over a semiconductor substrate, a diffraction grating disposed over the active layer, a clad layer partly disposed over the diffraction grating, at least one first burying material layer disposed beside side surfaces of end portions of the clad layer over the diffraction grating, and at least one second burying material layer disposed beside side surfaces of a center portion of the clad layer over the diffraction grating. A refractive index of the at least one first burying material layer is different from a refractive index of the at least are second burying material layer.

What is claimed is: 
     
         1 . An optical device comprising:
 a diffraction grating disposed over a semiconductor substrate;   an active layer disposed in a first region over the diffraction grating;   a guide layer disposed in a second region over the diffraction grating;   a clad layer disposed over the active layer and the guide layer;   a first burying material layer disposed in the first region over the clad layer; and   a second burying material layer disposed in the second region over the clad layer.   
     
     
         2 . The optical device according to  claim 1 , wherein
 an equivalent refractive index of the active layer is larger than an equivalent refractive index of the guide layer.