Tunable absorption in a dielectric-graphene-metal groove-grating absorber

We propose in this paper a dielectric-graphene-metal groove-grating absorber with a layer of graphene deposited between the metal and dielectric under the groove. The graphene layer is shown to influence the interference between the propagating modes in the grating grooves. Unlike traditional groove-grating, whose absorption spectrum could only be determined by structural parameters, the absorption spectrum of dielectric-graphene-metal groove-grating absorber could also be tuned by adjusting the applied voltage on graphene. With optimized geometric parameters and applied voltage, a high efficiency (>95%) absorptive spectrum with peak wavelength ranging from 1.2 μm to 1.5 μm could be realized. We also demonstrate a broad-band absorber which could achieve broad absorption (>85%) from 1.39 μm to 1.54 μm by biasing the graphene layers with various voltages.