Dual-band perfect graphene absorber with an all-dielectric zero-contrast grating-based resonant cavity

We proposed an all-dielectric resonant cavity based on a zero-contrast grating (ZCG), enabling the perfect absorption of monolayer graphene at the wavelength of 1550 nm band. The mechanism of dual-band perfect absorption, which is verified by the coupled-mode theory (CMT), can be attributed to the critical coupling of Fabry–Perot cavity resonance and guided-mode resonance (GMR) in the ZCG-based cavity. The absorption peaks can be tuned by tailoring the structural parameters, such as the thickness of the waveguide layer in the ZCG, and the cavity length. Interestingly, we find that the critical coupling of the system can be robustly controlled by changing the grating thickness and grating period of ZCG. The proposed structure has potential application prospects for high-performance graphene-based optoelectronic devices.