Highly Sensitive Refractive Index Sensor based on Photonic Crystal Ring Resonators Nested in a Mach-Zehnder Interferometer

Abstract Today, with the rapid development of photonics, optical sensors are being considered as efficient tools for detecting environmental variations and have been regarded as one of the most important fields in photonic research. In this study, we have proposed a two-dimensional photonic crystal (2D-PC) refractive index sensor using a combination of Mach-Zehnder interferometers and two ring resonators. Our goal is to increase the sensitivity and figure of merit (FOM) of the sensor, so that the output transmission spectrum can be considerably shifted by changing the refractive index of the simulated analytes. The proposed photonic crystal sensor consists of a hexagonal array of silicon rods on a SiO2 substrate. The finite difference time domain (FDTD) method is used for the numerical simulation of the structure. In this regard, to validate the simulation results, two different commercial software have been used. The quality-factor (Q-factor) and the sensitivity of the proposed structure are more than 1600 and 1700 nm / RIU, respectively, where RIU stands for the refractive index unit. In general, the structure has advantages such as low fabrication cost, high sensitivity to changes in refractive index and a high Q-factor.