Enhancing the Performance of Integrated Optical Sensor by Slow-light: Theoretical Study on Ring-Resonator Based Structures

In this work, the performance of three kinds of integrated optical ring-resonator based slow-light structures for sensing applications is theoretically studied using the transfer matrix method and the complex transmission coefficient approach. Enhancement of sensing performance due to the slowlight phenomenon is quantitatively formulated. The modeling results show that using realistic structure parameters, a refractive index detection limit of one order better than the state of the art Mach-Zehnder interferometer sensing structure is possible by the inclusion of such a slow-light structure. The role of ring(s) attenuation constant in limiting the usable light slowness and the achievable sensor resolution is also discussed. For a sufficiently small ring attenuation constant, the optimal sensing performance of a singleresonator circuit can be better than that of multiple resonator circuits, while offering less fabrication complexities, cleaner spectra, shorter device length, and higher figure of merit. Keywords– ring resonator, coupled-resonator optical waveguide, slow-light, refractometric sensor, MachZehnder interferometer