Optical filter using diffraction grating

TL;DR: In this article, the authors proposed to obtain the optical filter which has high diffraction efficiency over a wide wavelength range irrelevantly to the polarization state of incident light by arranging 1st and 2nd reflecting mirrors so that each reflected light beam is incident at right angles to a 2nd polarizer.

Abstract: PURPOSE:To obtain the optical filter which has high diffraction efficiency over a wide wavelength range irrelevantly to the polarization state of incident light by arranging 1st and 2nd reflecting mirrors so that each reflected light beam is incident at right angles to a 2nd polarizer. CONSTITUTION:Incident light is split by a 1st polarizer 11a into a P and an S linear polarized light beam, which are incident on 1st and 2nd diffraction grating 12a and 12b as S waves; and the diffracted light beams from the 1st and 2nd diffraction gratings 12a and 12b are reflected by 1st and 2nd reflecting mirrors 13a and 13b, made incident on the 2nd polarizer 11b orthogonally and then polarized and multiplexed, and projected as one light beam. In this case, the angles of diffraction of the diffraction gratings depend upon the wavelength, so only light with specific wavelength passes through the optical filter. The light beams incident on the diffraction gratings are all S waves, so the optical fiber which has the high diffraction grating and wide wavelength range without reference to the polarization states is obtained.