摘要 |
In a multi-wavelength spectroscopic apparatus using diffraction gratings, a first diffraction grating is a diffraction grating with diffraction efficiencies of p-polarized light and s-polarized light being equal on a short wavelength side of an operating wavelength range, and a second diffraction grating is a diffraction grating with diffraction efficiencies of p-polarized light and s-polarized light being equal on a long wavelength side of an operating wavelength range. By performing dispersion with two such diffraction gratings, it is possible to enlarge the amount of angular dispersion, and to produce a spectroscopic apparatus, which cancels wavelength dependencies of the diffraction efficiencies and has a small wavelength dependency of the diffraction efficiency.
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