Designing of a four-channel add-drop filter based on photonic crystal asymmetric ring resonator on InP substrate

This article describes a 4-channel add-drop filter based on photonic crystal asymmetric (elliptical) ring resonator on InP substrate at 1.55μm window. The photonic crystal is consisted of pillars in air background in hexagonal lattice. The radius of the pillars are determined to be 125.6 nm having lattice constant of 590 nm using the gap map and band diagram. Band diagram also shows that only TM mode can propagate through the waveguides. The proposed asymmetric ring resonator has a free spectral range of about 76.5 nm and channel spacing of about 1.6 nm (200 GHz), with more than 91% efficiency, -22.3 dB crosstalk and a quality factor of more than 4440. In this filter the quality factor is significantly improved with respect to other published reports.