Effects of structurally deformed sub-lattice points on the dispersion properties of 2D hybrid triangular–graphite photonic crystal

Abstract

We investigate a hybrid two dimensional (2D) photonic crystal which is constructed by merging triangular and graphite lattices in air background. Different geometries of scatterers such as circular rods, circular rods with elliptical holes, circular hollow rods and elliptical rods with circular holes in the triangular sub-lattice are considered and effects of shape on their dispersion properties are discussed. Photonic band gaps (PBGs) for TM- and TE-polarized modes are found to exist for these symmetry-reduced graphite structures. The TE PBGs are found to contribute to produce complete photonic band gaps (CBGs) up to high values of filling fraction and rod diameter ratios. We show that TM and TE PBGs display opposite behaviors as the structure is transformed from graphite to symmetry-reduced graphite (hybrid triangular–graphite lattice) and from symmetry-reduced graphite to hollow centered symmetry-reduced graphite. Concerning the PBGs, inner structural deformation is found to be more beneficial in comparison to outer structural deformation. Small group velocities are observed at the same frequency for both polarizations near the edges of PBGs for the configurations of circular rods, circular rods with elliptical holes and circular hollow rods. These observations seem valuable for optical gain enhancement and low-threshold lasing.