| 摘要 |
PROBLEM TO BE SOLVED: To ensure oscillation in a desired mode, and to improve the yield of a semiconductor laser such as a stable polarization switching device having excellent reproducibility, by installing diffraction gratings having each different coupling coefficient in both regions. SOLUTION: An N-type InP substrate 31 is coated with a photo-resist first and a diffraction grating pattern is formed by two luminous-flux exposure by an He-Cd laser, and irregular gratings 32a, 32b are formed to the substrate 1 by reactive ion beam etching(RIBE). A mask is formed only to the irregular grating 32a of a first region 38a by the photo-resist, and only the irregular grating 32b of a second region 38b is etched further by RIBE and the depth of irregularities is made shallower than the section of the irregular grating 32a. Accordingly, the coupling coefficient of the irregular grating 32b is made smaller than that of the irregular grating 32a. |
