Patent ID: 8605769

Claim:
A semiconductor laser device, comprising: a substrate having a principal plane; a two-dimensional diffraction grating that is formed on said substrate in a direction in which said principal plane extends and has an epitaxial layer of gallium nitride and a low refractive index material having a refractive index lower than that of said epitaxial layer, wherein said low refractive index material is made of at least one material selected from the group consisting of MgF2, CaF2, BaF2 and LiF, and wherein the diffraction grating has diffraction grating points comprised of a pattern of columns of the low refractive index material or the gallium nitride epitaxial layer, wherein each column includes substantially vertical sidewalls such that a distance between opposite sidewalls of the column is substantially constant along the height of the column; a first conductive-type clad layer formed on said substrate; a second conductive-type clad layer formed on said substrate; an active layer that is interposed between said first conductive-type clad layer and said second conductive-type clad layer and emits light when a carrier is injected thereinto; and a layer containing gallium nitride that covers a region directly on said two-dimensional diffraction grating, wherein said layer containing gallium nitride is grown in a horizontal direction along the principal plane of the substrate directly on the low refractive index material, wherein the epitaxial layer of gallium nitride in the two-dimensional diffraction grating and the layer containing gallium nitride that covers a region directly on the two-dimensional grating form one continuous epitaxial gallium nitride layer.