Absorption and Losses in One-Dimensional Photonic-Crystal-Based Absorbers Incorporating Graphene

We investigate the linear response of single and multiple graphene sheets embedded in quarter-wave one-dimensional photonic crystals (PhCs) in terms of absorption and losses. In particular, we show that it is possible to achieve near-perfect narrowband absorption when a single monolayer graphene is sandwiched between two PhC mirrors with optimized pair numbers. The simulations reveal that the resonant wavelength and the total absorption frequency may be tuned by tilting the angle of incidence of the impinging source. We also show that the losses, related to the dielectric materials constituting the one-dimensional PhC, can degrade the optical performance of the device. Conversely, by arranging the same dielectric slabs in a different order (supercell), it is possible to achieve a broadband absorption that is almost constant over a wide range of angle of incidence. In this configuration, the absorption and the bandwidth can be tuned by varying the supercell geometry. These features make these devices attractive for different applications ranging from tunable and saturable absorbers for short-pulse lasers to graphene-based photodetectors.