A study on photonic crystal slab waveguide with absolute photonic band gap

Abstract

Most of the conventional photonic crystal (PhC) slab waveguides have a photonic band gap (PBG) only for one polarization state of two orthogonal polarization states. In this paper, we study on an absolute PBG that can realize PBG for both polarizations in the same frequency range and demonstrate that an absolute PBG can be realized in PhC structures proposed here. In the numerical analysis and design of PhC structures, we employ the two-dimensional finite element method (FEM) based on the effective index method (EIM). First, we propose two-types of PhC structures with an absolute PBG and show that a steering type PhC is superior to an air-ring type PhC to obtain a wideband absolute PBG. It is also shown that the optimized steering type PhC has the absolute PBG whose bandwidth of 164 nm at the center wavelength of 1.55 µm. Furthermore, we design PhC waveguides based on the obtained PhC structure having an absolute PBG in order to obtain guided modes for both polarization states within the same wavelength range. The transmission properties of the designed PhC waveguides are also investigated and 60 degree bends which are required in compact photonic circuits are designed. From these results, the possibility to realize compact polarization multiplexing photonic devices is shown.