Patent ID: 7155073

Claim:
An optical element, comprising: a first periodic structure having a period shorter than a wavelength of used light; a second periodic structure that has a period shorter than the wavelength of the used light and in which a direction of the period is orthogonal to or substantially orthogonal to that of the first periodic structure, the second periodic structure being adjacent to the first periodic structure; and a pair of optical elements disposed so as to sandwich the first periodic structure and the second periodic structure, wherein the first periodic structure and the second periodic structure transmit light having first polarization direction and reflect light having second polarization direction orthogonal to the first direction, wherein the second polarization direction is substantially parallel to one of the periodic direction of the first periodic structure and the periodic direction of the second periodic structure, and wherein the following conditions are satisfied, n1p<n1s, n2p>n2s, | n 1 s−n 2 s|>|n 1 p−n 2 p|, where n1p and n1s represent effective refractive indices of the first periodic structure with respect to P-polarized light and S-polarized light, respectively, and n2p and n2s represent effective refractive indices of the second periodic structure with respect to the P-polarized light and the S-polarized light, respectively.