Multiple-band enhanced light absorption of monolayer graphene with critical coupling to guided mode resonance

We investigate subwavelength grating-coupled distributed Bragg reflector (DBR) in order to achieve total absorption at preselected wavelengths in a graphene monolayer. Multispectral and near-unity absorption (approximately 99.44% of the incident light at normal incidence) can be achieved in the proposed photonic structure at near-infrared (NIR) regimes. When the system meets the condition of critical coupling, the excited guided mode resonance (GMR) occurs at the resonance wavelength, and the corresponding electric field intensity around the graphene sheet can be greatly enhanced due to the reinforced light-graphene interaction. Multiple absorption peaks can be tuned within the wavelength region of 1.3 μm to 1.6 μm by varying the structural parameters. Our findings also indicate that the near-total-absorption peaks are highly dependent on the number and thickness of unit cells in DBR. These features make the proposed structure have great potential in applications of scalable perfect absorbers (PAs).