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

摘要

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 lambda(0) = 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 similar to 140 mu m(2), which makes this device a promising one for on-chip optical applications.