Patent ID: 8094373

Claim:
A polarization element, comprising: a base; a plurality of metal thin wires provided on the base along a predetermined alignment axis; and a plurality of protection films, one of the plurality of protection films covering one of the plurality of metal thin wires, wherein the plurality of metal thin wires includes a first metal thin wire and a second metal thin wire, the first metal thin wire and the second metal thin wire being adjacent to each other, wherein the plurality of protection films includes a first protection film provided on the first metal thin wire and a second protection film provided on the second metal thin wire, wherein a first mask is provided between the upper end of the first metal thin wire and the first protection film provided on the first metal thin wire, the first mask being a mask through which the first metal thin wire is formed, wherein a second mask is provided between the upper end of the second metal thin wire and the second protection film provided on the second metal thin wire, the second mask being a mask through which the second metal thin wire is formed, wherein the first protection film provided on the first metal thin wire covers the first mask and both sidewalls of the first metal thin wire, and the second protection film provided on the second metal thin wire covers the second mask and both sidewalls of the second metal thin wire, wherein a width of a first part in a direction of the alignment axis, the first part being above the first mask, of the first protection film provided on the first metal thin wire is larger than a sum of a width of the first metal thin wire in the direction of the alignment axis and widths of second parts in a direction of the alignment axis, the second parts being on the both sidewalls of the first metal thin wire, of the first protection film provided on the first metal thin wire, wherein a third part, the third part being on a first sidewall of the sidewalls of the second metal thin wire, of the second protection film provided on the second metal thin wire forms an air gap with one of the second parts of the first protection film provided on the first metal thin wire, wherein the first sidewall is opposed to one of the sidewalls of the first metal thin wire where the one of the second parts is provided, and wherein the second and third parts have substantially the same thickness along lengths thereof in an orthogonal direction to the base.