Patent ID: 8891159

Claim:
An optical semiconductor element comprising: a grating base layer including a projection-recess structure disposed over a substrate; and a grating cover layer including a group III-V semiconductor having three or more elements, wherein the grating cover layer includes a first region which is disposed over recessed portions of the grating base layer and which has a first compositional ratio of aluminum in a group III-V semiconductor having a first refractive index, and a second region which is disposed over projecting portions of the grating base layer and which has a second compositional ratio of aluminum in a group III-V semiconductor having a second refractive index that is smaller than the first refractive index, wherein the grating base layer includes a third compositional ratio of aluminum in a group III-V semiconductor having a third refractive index that is smaller than the first refractive index, wherein the third compositional ratio is larger than the first compositional ratio.