Patent ID: 7477819

Claim:
A two-dimensional photonic crystal, wherein on a plane in which four adjoining unit lattices are arranged so as to have one angle in common with the unit lattice being a rectangle whose shorter side X 1 has a length of x 1 and whose longer side Y 1 has a length of y 1 , first dielectric regions each being columnar and having a rectangular cross section whose shorter side X 2 has a length of x 2 and whose longer side Y 2 has a length of y 2 are disposed on said shorter sides X 1 and said longer sides Y 1 of each rectangular unit lattice, characterized in that said first dielectric region is arranged so that the midpoint of said shorter side X 1 and the midpoint of said longer side Y 1 and the center of said rectangular cross section substantially coincide, said longer sides Y 2 of each said first dielectric region are substantially parallel to each other, the ratio of x 1 :y 1 equals 1:substantially √{square root over (3)}, and the ratio of x 1 :x 2 :y 2 equals 1:0.133:0.48 to 1:0.158:0.58; and wherein: said two dimensional-photonic crystal has a full band gap width of 22.5% or greater.