| 摘要 |
PURPOSE:To manufacture a diffraction grating which has grooves at half intervals in a simple process by forming photoresist in a grooves of a diffraction grating which has grooves on one main surface at specific intervals, and etching the diffraction grating by using said resist as a mask. CONSTITUTION:Photoresist 2 is applied over grooves 5a of a GaAs substrate 5 where a diffraction grating of A=0.25mum is formed by a known method, baked, and exposed uniformly to laser beam. Then, the photoresist 2 is developed under temperature control to position the top surface of the photoresist at height nearly a half as large as the depth of the grooves 5a, and the photoresist 2 is baked. Then, this photoresist 2 is used as a mask to etch the substrate 5 in an etchant having large anisotropy, and then the photoresist 2 is removed. Consequently, grooves are formed to width a half as large as the starting pitch A of the grooves 5a.
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