Improved design of photonic crystal-based multiplexer/demultiplexer devices

In this paper, an improved design of photonic crystal (PhC)-based multiplexer/demultiplexer (MUX-DEMUX) devices is presented. This is achieved using careful geometrical design of microcavities with respect to the coupling length of the propagating wave. The nature of the design means that a microcavity embedded between two waveguides selects a particular wavelength to couple from one waveguide into the adjacent waveguide showing high selectivity. The numerical technique used for the designs throughout this article is the complex envelope alternating direction implicit finite difference time domain (CE-ADI-FDTD). Also, improvements have been made on the performance of the perfectly matched layers (PML) by presenting an accurate physical model of discretisation error.