Patent ID: 8619830

Claim:
A photonic crystal surface emission laser, comprising: an active layer; and a photonic crystal layer made of a plate-shaped slab provided with modified refractive index areas having a refractive index different from that of the slab, the modified refractive index areas being arranged on each of lattice points of a first rhombic-like lattice and a second rhombic-like lattice in which two diagonals are respectively parallel and only one of the two diagonals has different lengths, wherein: a x1 , a x2 , a y , and n satisfy a following inequality: ï˜ƒ 1 a x â¢ â¢ 1 - 1 a x â¢ â¢ 2 ï˜„ ( 1 a x â¢ â¢ 1 + 1 a x â¢ â¢ 2 ) 2 + ( 2 a y ) 2 â‰¤ 1 n , where a x1 and a y respectively represent a length of aforementioned one of the two diagonals having different lengths and that of an other one of the two diagonals of the first rhombic-like lattice, a x2 (a x2 â‰ a x1 ) and a y respectively represent a length of the aforementioned one of the two diagonals having different lengths and that of an other one of the two diagonals of the second rhombic-like lattice, and n represents an equivalent refractive index of the photonic crystal layer in a direction perpendicular to the photonic crystal layer.