Patent ID: 6891147

Claim:
A wavelength-selective diffraction element adapted to receive two kinds of light having a wavelength λ 1 and a wavelength λ 2 (λ 1 <λ 2 ), characterized in that the wavelength-selective diffraction element comprises a transparent substrate, a grating comprising a concavo-convex member having a periodically recessed and projected shape formed on a front surface of the transparent substrate and a filling member filled in at least a recessed portion of the grating, wherein either of the concavo-convex member or the filling member contains an organic pigment having the absorption edge of light in a region having a shorter wavelength than the wavelength λ 1 ; the concavo-convex member and the filling member have the same refractive index with respect to either one of light having a wavelength λ 1 and light having a wavelength λ 2 , and they have different refractive indices with respect to the other light having a wavelength.