Fig. 2. Hybrid graphene metasurface allows for electrically tunable resonant absorption.

a Schematic of the hybrid graphene metasurface. Inset: high-frequency equivalent circuit model. b SEM image showing the fabricated gold nanoantenna array. Inset: zoom-in view. P_x = P_y = 1 μm, L = 400 nm, w = 100 nm, and g = 40 nm. c Measured reflection spectra when applying different gate voltages V_g. d Change of reflection ΔR(λ) = R_+7 V(λ) − R_−3 V(λ) (red curve) and modulation depth M(λ) = |ΔR(λ)|/max[R_+7 V(λ);R_−3 V(λ)] (cyan curve) for two gate voltages of V_g = +7 V and −3 V as functions of wavelength λ