TWO-DIMENSIONAL PHOTONIC CRYSTAL SLAB HAVING LOCAL THREE-DIMENSIONAL STRUCTURE
A two-dimensional photonic crystal for controlling the front/back emission ratio of light emitted from an optical resonator. A refractive index member (13) of a material having a refractive index different from that of the air is provided on a two- dimensional photonic crystal having air-holes (12) periodically made in the body (11) of the crystal. The body (11) where the refractive index member (13) is provided constitutes an optical resonator together with the refractive index member (13). The light (191) emitted from the high refractive index side, namely from the side where the refractive index member (13) is provided is made stronger than the light (192) emitted from the other side. The front/back emission ratio between the lights (191, 192) can be controlled by varying the refractive index, shape, and size of the refractive index member.