Patent ID: 7589895

Claim:
A polarizing element, wherein the polarizing element has a two-layer structure in which a grating pattern having a constant period Λ is formed in a substrate, a cross section of the grating pattern having a triangular shape, and a film having a refractive index higher than that of the substrate is deposited on the grating pattern, in the case where a first wavelength λ 1 and a second wavelength λ 2 satisfy a relationship of λ 1 <λ 2 , Λ cos θ 0 <λ 1 where θ 0 is an angle of incidence to a grating surface, and the grating period, a grating height, and a film thickness are determined such that reflection efficiency of zero-order diffracted light of TE polarization is not lower than a predetermined value that is sufficient for the polarizing element functions as a reflecting element for the first wavelength λ 1 while transmission efficiency of zero-order diffracted light of TM polarization is not lower than the predetermined value that is sufficient for the polarizing element functions as a transmitting element for the first wavelength λ 1 , and such that transmission efficiency of the zero-order diffracted light of the TE polarization is not lower than the predetermined value that is sufficient for the polarizing element functions as a transmitting element for the second wavelength λ 2 while reflection efficiency of the zero-order diffracted light of TM polarization is not lower than the predetermined value that is sufficient for the polarizing element functions as a reflecting element for the second wavelength λ 2 .