Electric-Controlled Switching ON/OFF of Bands in a Graphene-Based Multi-band Metamaterial Absorber

Optical switches utilizing micro/nanostructures are currently in high demand. To enhance frequency-selective light absorption and achieve absorption-mediated switching, a novel design of graphene-assisted multi-band metamaterial absorber is numerically investigated at optical to near-infrared frequencies. It features a thin silicon layer with circular perforations on a monolayer graphene supported by a metallic substrate. The finite integration technique-based Computer Simulation Technology (CST) Microwave studio is used for numerical simulations. The coupled mode theory (CMT) is applied to validate the numerical results and to elucidate the origin of absorption. Simulation results show that the multi-band absorption is significantly enhanced due to critical coupling facilitated by guided-mode resonances within the system. The absorber exhibits four narrow absorption bands at wavelengths of 551 nm, 671 nm, 817 nm, and 1071 nm, with absorptances of approximately 1, 0.54, 1, and 0.92, respectively. The full width at half maximum (FWHM) for these bands are 6 nm, 5 nm, 11 nm, and 8 nm, respectively. The main advantage of this absorber is its ability to electrically control the number of absorption bands. By applying an external gate voltage across the graphene layer, it can be switched from a multi-band absorber to a triple/double/single-band absorber or even a perfect reflector. The absorption spectra are investigated by considering various factors, including different geometrical parameters, light polarization, chemical potential, and angle of incidence. Due to its multiple resonance wavelengths, high absorptance, insensitivity to polarization, and ability to switch bands, the proposed absorber holds promise for various applications across the visible to near-infrared frequency range.