Optical add-drop filter based on square ring resonator consisting of octagon shape core

In this paper, an optical add-drop filter (ADF) based on a 2D square lattice photonic crystal (PC) is designed. Band diagram of considered ADF is analyzed with Plane Wave Expansion (PWE) technique and simulations on light propagation through it have been carried out using 2D Finite Difference Time Domain (FDTD) technique. The 2D square lattice PC consists of 35*29 infinitely long circular silicon rods of refractive index 3.45 in air background. The ADF design consists of two defect waveguides Bus and Drop which are coupled to each other through a square ring consisting of an octagon shape core. The proposed ADF is a compact structure of 286.19µm
²
. with resonance at wavelength 1549.2nm, a bandwidth of 2 nm, a high quality factor of 774.59, and a dropping efficiency of 90%. The effect of refractive index variation (of different parts of the design) on the performance of ADF is also investigated.