A Silicon Microring Resonator for Refractive Index Carbon Dioxide Gas Sensing
Jiaqi Wang, Hui Zhang, Si Chen, Zunyue Zhang, Guoxian Wu, Li Xu, Penghao Ding, Chuxian Tan, Yu Du, Youfu Geng, Xuejin Li, Hon Ki Tsang, Zhenzhou Cheng
Abstract
Silicon microring resonators (MRRs) are promising for on-chip optical gas sensing due to their strong light-matter interaction, compact footprint, and mass-scalable fabrication potential. However, for refractive index sensors, it is essential to consider the cross-sensitivity to temperature induced by the thermal-optic effect in MRRs. To address this challenge, we demonstrate a silicon MRR coated with gas-sensitive polyhexamethylene biguanide hydrochloride as the upper cladding for carbon dioxide sensing. The engineered MRR exhibits distinct temperature and gas sensitivities for TE 0 and TE 1 modes. With the linear independent responses, a gas sensitivity of −0.90 pm/ppm within a range of 700 ppm is demonstrated in conjunction with the temperature compensation. The response and recovery times of gas sensing are measured as ∼3.5 and 1.5 min. Our study paves the way for on-chip optical gas sensing with temperature compensation.