Optical waveguide, method for manufacturing optical waveguide, and optical semiconductor device

A method for manufacturing an optical waveguide comprising a semiconductor quantum well structure, wherein the optical waveguide comprises a first region in which the semiconductor quantum well structure is not disordered, a second region in which the semiconductor quantum well structure is disordered, and a third region provided between the first region and the second region, the method comprising:

• forming a selective growth mask defining an opening portion in the third region in a surface of a crystal including the semiconductor quantum well structure, wherein a ratio between a width of the selective growth mask and a width of the opening portion varies continuously in a direction from the first region toward the second region over all of the third region;
• selectively growing a semiconductor crystal in the opening portion;
• removing the selective growth mask;
• forming an annealing mask in the second region, the third region, and a part of the first region including an interface between the first region and the second region;
• annealing the crystal including the semiconductor quantum well structure with the annealing mask formed thereon;
• and
• removing the annealing mask.