| 摘要 |
PROBLEM TO BE SOLVED: To form a coating film which reduces reflection of light on the surface without deviating the cross-sectional form of the grooves of a diffraction grating or hologram from the ideal form. SOLUTION: After a coating film 20 is formed on a transparent substrate 7, grooves 203 are formed by etching or a 2P method. Since unnecessary coating film 20 is not formed on the side faces 202 or corners 201 of the grooves 203, decrease in the use efficiency of light due to scattered light or decrease in the signal-to noise ratio in a semiconductor laser device can be avoided. |
