Defect modes in a two-dimensional square lattice of square rods

Abstract

We investigated defect modes created by drilling a hole in a rod and rotating it in a two-dimensional square lattice of square dielectric rods as well as that of square metallic rods in air by the supercell method. In E polarization (the electric field parallel to the rod axis), a hole in a dielectric rod created a nondegenerate acceptor mode inside the photonic band gap (PBG), while the one in a metallic rod resulted in a nondegenerate donor mode below the cutoff frequency. The frequency of the acceptor mode extends almost ail over the PEG. The rotation of a square rod did not create defect modes in either case, regardless of the angle of rotation. In H polarization (the magnetic field parallel to the rod axis), a hole in the dielectric rod created acceptor modes and rotating the rod resulted in paired donor and acceptor modes. As the angle of rotation increased, the donor mode moved away from the top of the PEG and the acceptor mode moved away from the bottom of the PEG. One of the defect modes of H polarization was strongly localized around the rods surrounding the defect rod rather than around the defect rod itself. [S1063-651X(98)13811-4].