Optical Device

摘要

A conductive thin film has first and second surfaces and at least one opening extending through from the first surface to the second surface. At least on one of the first and second surfaces, first and second periodic surface patterns having different period lengths are provided. The period length of the second periodic surface pattern is substantially equal to an odd integral multiple of a half of the period length of the first periodic surface pattern. With this, surface plasmon polaritons excited by the first periodic surface pattern undergo odd-order Bragg reflection by the second periodic surface pattern. As a result, the intensity of the light falling on the first surface and transmitted to the second surface through the opening is increased with high efficiency.