Modeling of Mach-Zehnder Interferometric Sensors Employing Ring-Resonator Circuits for Slow-Light Enhancement

The performance of symmetric Mach-Zehnder interferometric (MZI) sensor employing ring-resonator circuits for slow-light enhancement of the sensor performance was theoretically investigated. The slow-light structures considered in this study are coupled-resonator optical waveguide (CROW), four-port single ring-resonator (FPRR), and two-port single ring-resonator (TPRR) circuits. The performance of the sensors was quantitatively formulated for resolution of refractive index of measurand and figure of merit (FoM) with respect to similar MZI without employing slow-light structure. The effect of attenuation constant of mode traveling in the ring-resonator to the theoretical ultimate sensor resolution limited by available insertion loss budget was also discussed. Taking realistic ring attenuation constant of 1 dB/cm, ring radius of 300 mu m, and 20 dB insertion loss budget, the theoretical ultimate sensing performance using a single-resonator TPRR can reach resolution of 3.63E-10 RIU which is 5 times better than single-resonator FPRR and 3-resonator CROW while giving FoM of 5 and 15 times better compared to circuit employing FPRR and 3-resonator CROW, respectively.