GRISM, MANUFACTURING METHOD OF THE SAME, AND OPTICAL DEVICE COMPRISING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a grism with high transmittance in a vacuum ultraviolet range.

SOLUTION: A grism is provided which comprises a prism and a diffraction grating having a plurality of binary-type diffraction gratings. In the grism, the prism is formed with a first optical material which is at least one selected from the group consisting of lithium fluoride and magnesium fluoride, the binary-type diffraction gratings are formed with a second optical material which is at least one selected from the group consisting of lithium fluoride and magnesium fluoride, and the root-mean-square value (rms value) of the surface roughness of the binary-type diffraction gratings is equal to or less than 5 nm. The grism can be used preferably in a vacuum ultraviolet range from 200 nm to the absorption edge wavelength on a short wavelength side in which the refractive indices of the lithium fluoride and the magnesium fluoride vary significantly.

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