Patent ID: 8358895

Claim:
A two-dimensional photonic crystal including a slab-shaped body provided with a periodic arrangement of modified refractive index areas whose refractive index differs from that of the body, wherein: on a first surface, which is one of surfaces of the body, the modified refractive index areas are arranged in a triangular lattice pattern and have at least a three-fold rotational symmetry with respect to each lattice point; on a second surface, which is the other surface of the body, the modified refractive index areas are arranged in a triangular lattice pattern whose position is complementary to the triangular lattice on the first surface, and have at least a three-fold rotational symmetry with respect to each lattice point; and the modified refractive index area has columns each extending from one lattice point on the first surface to each of three lattice points on the second surface that are nearest to the aforementioned lattice point on the first surface and each of the columns has an oblique cylindrical shape with a continuous smooth wall.