▎ 摘　　要

Mid-infrared (Mid-IR) silicon photonics has attracted great attention for its promising potential in developing chip-integrated molecular sensors. With the merits of high-quality factors, excellent fabrication reproducibility, and compact device footprints, microring resonators (MRRs) are useful silicon photonic devices for sensing. However, expensive and bulky mid-IR facilities, namely, tunable lasers or spectrometers, may limit applications of MRR-based sensing devices. Here, we theoretically study an MRR-based nitrogen dioxide gas sensor probing with a monochromatic mid-IR laser to conquer this limitation. Moreover, graphene is used as a sensitizing medium by changing the phase of the propagating light in the silicon waveguide after gas molecules adsorption. Specifically, we theoretically realized a sensitivity of 1.259 x 10-5 RIU/ppm, a limit of detection of 5.1 ppm, and a detection range of 5135 ppm based on the proposed sensor. Our study is expected to open a door to the development of chip-integrated, low-cost, high-sensitivity optical gas sensors.