Patent ID: 7894693

Claim:
An optical semiconductor device comprising: a waveguide that has one or more first segments, one or more second segments and a plurality of third segments, the first segment having a region that includes a diffractive grating and another region that is a space region combined to the region, the second segment having a region that includes a diffractive grating and another region that is a space region combined to the region, a length of the second segment being different from that of the first segment, the third segment having a region that includes a diffractive grating and another region that is a space region combined to the region, a length of the third segment being shown as L 3 =L 1 +(L 2 −L 1 )×K 1 in which 0.3≦K 1 ≦0.7, L 1 is a length of the first segment, L 2 is a length of the second segment and L 3 is a length of the third segment; and a refractive index control portion that controls refractive index of the first segment through the third segments.