Nonlinear metamaterial absorbers enabled by photonic doping of epsilon-near-zero metastructures

We theoretically demonstrate an approach for designing absorbers with strongly intensity-dependent absorption. The proposed absorbers consist of a spacer layer between a top resistive sheet and an underlying metallic substrate, akin to the traditional Salisbury screen, except for the use of an epsilon-near-zero slab with a nonlinear dielectric inclusion as the spacer layer. Such absorbers may be designed to exhibit highly tailorable absorption characteristics, including either saturable or reverse saturable absorption. In addition, the proposed nonlinear absorbers include interesting features such as high angular selectivity, insensitivity with respect to the absorber thickness, bandwidth tunability, and the possibility of operating with or without hysteresis. The proposed nonlinear absorbers may be appealing for several applications and nonlinear devices, such as optical limiters.