Graphene-based photonic nanostructures for linear and nonlinear devices

Graphene, a 2D carbon sheet with a honeycomb lattice, is a two-dimensional material with outstanding thermal, mechanical, electronic and optical properties. In particular, graphene is a gapless material with high mobility that exhibits remarkably high absorption values (~2.3%) for the visible and near-infrared wavelengths. In this paper, we will illustrate some applications of graphene photonics and plasmonics, reported in literature, in different research fields and we will investigate theoretically and experimentally the linear and nonlinear properties of graphene-based nanostructures such as one-dimensional (1D) photonic crystals (PhCs) and 1D gratings. In particular, we will show how to exploit the large nonlinear response and the saturation effects of graphene monolayers, sandwiched in the defect layer of an asymmetric 1D photonic crystal, to dynamically change the structure from a perfect absorber (100%) to a mirror. We will also show how it is possible to tune the working wavelength by tilting the angle of incidence of the impinging electromagnetic field for both TE and TM polarizations. Finally, we will report on a 1D dielectric grating, incorporating a graphene monolayer, that resembles the 1D PhC optical response exploiting guided mode resonances. Therefore, the proposed nanostructures could efficiently exploit the linear and nonlinear properties of the graphene monolayer for the realization of tunable absorbers or saturable mirrors improving and boosting the performance of optical devices such as photo-detectors and short-pulse lasers.