REFLECTION TYPE DIFFRACTION GRATING

摘要

PURPOSE: To solve such problems of a conventional reflection type diffractive optical element that because the diffraction efficiency depends on polarized light, optical elements to compensate the polarized light are required to be inserted into the optical system and its insertion loss decreases the spectral sensitivity. CONSTITUTION: First, a sol solution containing a liquid hydrolysate of methyltriethoxysilane as a main component was applied onto a glass substrate(10) by spin coating. This sol-solution-applied substrate(10) was press-molded while a brazed replica diffraction grating (900/mm) which was subjected to mold release treatment and which was available on the market was used as a stamping mold. Then, mold release treatment and baking were performed to thereby obtain a fine roughness structure(12) serving as a diffraction grating. The depth of each of the roughness grooves was about 1 mu m. Al was vacuum-deposited on a surface of the fine roughness structure to thereby form a metal film(14) with a thickness of 100 nm. The reflectance of the Al film was not lower than 90 % with respect to non-polarized light. Silicon dioxide (SiO2) and titanium dioxide (TiO2) were vacuum-deposited successively on the Al film to thereby form a dielectric film(16) constituted by two layers 280 nm and 170 nm thick.