Design and optimization of optical add-drop filter and sensor using 2D photonic crystal

Abstract

In this paper, we have investigated the performance of a 2D photonic crystal add-drop filter (ADF) and sensor based on a quasi-square ring resonator cavity. High quality factor (Q) is a crucial requirement for both filter and sensor. We have focused on improving the Q of the structure by applying different optimization techniques. The designed 20 μm × 19 μm photonic crystal has a square lattice of GaAs rods in air with refractive index of 3.40 at operating wavelength of 1.55 μm. The effect of scattering rods at four corners and inner rods of the ring resonator cavity are analyzed at first. After observing slight improvement in Q, it is found that comparatively high Q is achieved by the application of a hetero ring resonator cavity to the structure. Besides, the optimized ADF is tuned to two different wavelengths simultaneously available from two output ports, 1537.40 nm 1548.5 nm. Finally, the performance of the optimized structure is investigated as a sensor and it is found that the sensitivity is 11.6 nm/RIU (Refractive Index Unit). Simulation results are obtained using finite difference time domain (FDTD) method.