Optically transparent graphene-based Salisbury screen microwave absorber

We propose an analytical model to study the absorption of a graphene sheet in the microwave range when its sheet resistance is varied. We demonstrate that the maximum achievable for a suspended structure is 50% and it is independent of the frequency in the range of interest. Finally, we propose a microwave absorber based on a Salisbury screen configuration consisting of two opportunely doped graphene sheets separated by a quarter-wavelength dielectric lossless spacer. In particular, we show how it is possible to achieve near-perfect absorption over a wide frequency bandwidth and how this graphene-based absorber is less sensitive to the variation of the graphene sheet resistance. The realization of the microwave absorber with few-layer graphene leads to a fully transparent device in the visible-near infrared range.