Wavelength-division demultiplexer based on hetero-structure octagonal-shape photonic crystal ring resonators

Abstract

In this effort, a wavelength-division demultiplexer (WDM) is presented. The proposed device is formed by means of horizontal cascading of hetero-structure photonic crystal (PhC) ring resonators (RRs). In order to design this structure, four octagonal-shaped PhCRRs are horizontally connected. Each PhCRR creates a unique channel and has with a variable resonant wavelength. To achieve the required WDM channel spacing, every PhCRR is tuned to a unique resonant wavelength which is premeditated using various design parameters such as ring’s dielectric constant, surrounding medium’s dielectric constant, lattice dielectric constant, lattice constant in x or/and z direction and etc. Considering the ambient medium as air, rods dielectric constant as n = 3.6, and the PhC lattice with a = 558 nm in square type; the quality factor (Q) and drop efficiency of the base unit are found as 3100 and 100%, respectively, for operating at λ0 = 1550 nm. The simulation results are achieved by means of finite difference time domain (FDTD) method. These results show that the proposed WDM structure has a good performance in terms of average transmitted power higher than 95 ± 4%, reasonable channel spacing, low channel crosstalk (about -24db in worst case), and finally narrow full width half maximum (FWHM) bandwidth. The overall footprint of the proposed structure is calculated to be about ∼140 μm2, which makes this device a promising one for on-chip optical applications.