Realization of tunable optical channel drop filter based on photonic crystal octagonal shaped structure

Photonic crystals (PhCs) are artificial dielectric nanostructure materials. In these structures, a periodic modulation of the material dielectric constant results in a photonic band gap (PBG). By employing defects in the photonic crystals, light can steer in specific direction. Consequently, defects are used in most of the PhC structures. In this work, a novel channel drop filter (CDF) based on two dimensional (2-D) photonic crystal with octagonal shaped structure is designed and numerically analyzed by using the finite difference time domain (FDTD) and plane wave expansion (PWE) techniques. The proposed filter is an octagonal shaped structure of Si rods between two waveguides; consisting of 19*18 silicon rods with the refractive index of 3.5 and rod radius of 0.16a; where a is a lattice constant and equals 0.6 mu m. By analyzing the structure, wide ranges of TE photonic band gap (PBG) would be achieved. It will be stated that the proposed CDF has appropriate characteristics and could be used in the future wavelength division multiplexing (WDM) communication systems.