▎ 摘　　要

In this paper, enhanced absorption has been demonstrated using multilayer graphene strip grating coupled with dielectric grating (DG). The proposed plasmonic structure consists of graphene grating and DG backed with a dielectric metal substrate. Perfect absorption can be achieved due to effective impedance matching, the results of coupled-mode theory and finite-difference time domain agree well. We find that the absorption resonance dip can be tuned using the gate voltage to alter the chemical potential of the graphene. In addition, when the proposed complex grating structure is used in refractive index sensing, it shows an excellent sensing performance in the mid-infrared range (sensitivity up to 4860nm/RIU)