| 摘要 |
PROBLEM TO BE SOLVED: To provide a diffraction grating element which has a high efficiency of diffraction and, moreover, is capable of increasing an angle difference between an incident beam and a diffraction beam even in the diffraction grating element which uses light having different wavelengths as an object of diffraction. SOLUTION: To a diffraction grating 52, three beams LT, LR1, LR2 having different wavelengths are made incident from the inside of an element and optical paths of beams LR1, LR2 before incidence coincide with each other. The diffraction grating 52 has periods of ruggedness in the two directions which are vertical to each other, wherein the periods are different. Incident faces of the beams LT, LR1, LR2 have an inclination with respect to the short period direction of the diffraction grating 52. The diffraction grating 52 propagates the beam LT inversely as the zero-order diffractive transmission light along optical paths of the beams LR1, LR2 before incidence and makes the beams LR1, LR2 the minus first-order diffractive transmission light. COPYRIGHT: (C)2006,JPO&NCIPI
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