Free spectral range and quality factor enhancement of multi-path optical ring resonator for sensor application

Abstract

The purpose of this study was to find the most optimal configuration of multipath optical ring resonator (MpORR) based on silicon on insulator (SOI). Two important indicators of MpORR are free spectral range (FSR) and Q factor. The greater the FSR and Q factor, the greater the ability of the MpORR to distinguish each resonance signal so that the sensor is more selective and can detect substances with small concentrations. Finite-difference time-domain (FDTD) simulations was used to optimize and analyze the design of MpORR. Several parameters that can affect the FSR and Q factors of the MpORR were investigated, including the ring resonator radius, the gap separation distance between the waveguide and the ring resonator, and the gap separator distance between resonator rings of MpORR. Based on the simulation, the most optimal configuration for MpORR are 3 µm, 200 nm, and 160 nm, that correspond to the ring resonator radius, the gap separation distance between the waveguide and the ring resonator, and the gap separator distance between resonator rings, respectively. From the simulation, 28 nm wide FSR and 1495 of Q Factor were obtained. With a wide FSR and a high Q factor, the design can be used to detect various analytes with high sensitivity.