Sensitivity-enhanced microring resonator with partial intermediate refractive index cladding

In this report, a microring structure with partial intermediate refractive index cladding is proposed and simulated using finite-difference time-domain. The introduced intermediate refractive index cladding is a transitional layer between the ring waveguide and the environment to achieve a greater detection range of evanescent wave, which is of great benefit to the light–matter interaction. The sensitivity of the modified microring resonator is obtained up to 480 nm / RIU, which is eight times the microring resonator without partial intermediate refractive index cladding. This scheme can offer a way to improve the sensitivity of optical microcavity biosensors.