Graphene-based electromechanically tunable subwavelength mid-IR perfect absorber

In this article, we propose and numerically investigate a graphene-based electromechanically tunable perfect absorber design. The fundamental motivation is to demonstrate the electromechanically tunable feature in graphene metasurface at the mid-infrared regime, which otherwise exploited only the chemical potential feature in the literature. The structure consists of a gold grating on a gold substrate separated by an oxide spacer with an overlay of monolayer graphene with free-standing segments. By applying external DC voltages, the free-standing region of the graphene layer deflects, owing to the electrostatic force it experiences. This shifts the resonance absorption wavelength. In the mid-infrared region of 5-10 mu m, a very low actuation voltage of 1.6 V displaces the graphene membrane by 1 nm, resulting in a wide shift of 60 nm in resonance wavelength. A continuous tunability with near-perfect absorption over a wavelength range of 200 nm for an applied voltage of only 7 V is demonstrated. At a voltage greater than 7 V, a mode hopping phenomenon is observed, hampering the perfect absorber operations with a shift in wavelengths. It is shown that the perfect absorption is again retained at some higher voltage. Such implementations hold promising applications in nanophotonics sensors, detectors, real-time beam steering, etc.

Automated summary

In this article, a graphene-based electromechanically tunable perfect absorber design is proposed and numerically investigated. By applying external voltages, the resonance absorption wavelength of the graphene layer can be shifted due to the deflection of the free-standing region. It is demonstrated that a wide shift in resonance wavelength can be achieved with a low actuation voltage in the mid-infrared region.