Patent ID: 7539385

Claim:
An optical semiconductor device, comprising: a semiconductor substrate having a (100) principal surface; a mesa stripe waveguide formed on a first region of said semiconductor substrate, said mesa stripe waveguide guiding a light therethrough in a forward direction to an end face of said mesa stripe waveguide, said mesa stripe waveguide amplifying a light guided therethrough by stimulated emission; a plurality of dummy mesa patterns, that do not actively amplify light, formed on said semiconductor substrate in a second region having an exit facet, said second region being located at a forward side of said first region, said exit facet determining an edge surface of said optical semiconductor device, each of said plurality of dummy mesa patterns extending to said exit facet, a gap being formed between said plurality of dummy mesa patterns in said second region; and a semi-insulating buried semiconductor layer formed on said semiconductor substrate so as to cover said first and second regions continuously, said semi-insulating buried semiconductor layer filling a right side and a left side of said waveguide mesa stripe in said first region; said semi-insulating buried semiconductor layer having a height equal to a height of said dummy mesa patterns.