Plasmonic absorption enhancement in periodic cross-shaped graphene arrays

We investigate the periodically patterned cross-shaped graphene arrays from far-infrared to THz region as wavelength tunable absorbers. By increasing the cross-arm width, the absorption of the single-layer array can essentially exceeds the continuous graphene sheet due to the surface plasmon resonance, even for small graphene filling ratio. The absorption can be further enhanced with higher chemical potential and relaxation time. The complementary structure brings about more absorption of incident light compared to the original graphene array. Moreover, the wavelength of absorption maximum shows angle independence for both TE and TM polarizations. The absorption efficiency can be significantly improved with double layers of the cross-shaped graphene arrays, which are helpful to design dual-band and broadband absorbers.