Potential of high Q dual band Mid-Infrared metasurfaces with Quasi-BIC for refractive index sensing

•The designed refractive index sensor has high quality factor and the figure of merit values and achieves good sensing performance.•The structure excites two QBICs with low radiation loss and realizes the two-band resonant response.•The resonant response band of the structure is in the mid-infrared band.•Electromagnetic field enhancement is mainly concentrated outside the structure and is conducive to the interaction between light and matter.•The designed structure is easy to process by introducing a coupler in the symmetry center to stimulate QBICs.