Method for manufacturing an optical member and method for manufacturing a semiconductor laser device

A method for manufacturing an optical member comprising:

• providing a silicon substrate having a first main surface of a {110} plane and a second main surface of a {110} plane that are parallel to each other;
• forming mask patterns on the first main surface and the second main surface, each of the mask patterns having an opening extending along a <100> direction, so that the opening on a first main surface side and the opening on a second main surface side are disposed alternately, or so that the opening on the second main surface side are disposed directly under the opening on the first main surface side;
• forming recesses having sloped surfaces of {100} planes in the first main surface side and the second main surface side by wet etching the silicon substrate with an etchant using the mask patterns as masks;
• forming a reflective film on the first main surface or the second main surface;
• and
• dividing the silicon substrate in the recesses so that a single optical member includes the sloped surface of one of the recesses and the sloped surface of an adjacent one of the recesses after the dividing of the silicon substrate.