Patent ID: 8243768

Claim:
A semiconductor diffraction grating device comprising: a semiconductor substrate having a principal surface; a semiconductor core layer and a semiconductor cladding layer provided on the principal surface of the semiconductor substrate; and a chirped grating structure provided between the semiconductor core layer and the semiconductor cladding layer, the chirped grating structure having a first end and a second end opposite to the first end and having a changing coupling coefficient, κ, wherein the chirped grating structure includes a first region, a second region, and a third region arranged in that order in a predetermined axis direction, the first region, the second region, and the third region each including a plurality of projections constituting a chirped grating; the plurality of projections are provided at placement positions arranged with a predetermined pitch in the predetermined axis direction, the pitch of the projections changing monotonically from the first end to the second end of the chirped grating structure; and the first region has a coupling coefficient κ increasing monotonically from the first end of the chirped grating structure to the second region in the predetermined axis direction, the second region has a constant coupling coefficient κ of a predetermined value, and the third region has a coupling coefficient κ decreasing monotonically from the second region to the second end of the chirped grating structure in the predetermined axis direction.