Enhanced coherent amplification and nonlinear effects using tunable THz hyperbolic metamaterials based on active and passive graphene

Graphene is a two-dimensional (2D) material that is very appealing for terahertz (THz) applications given that its plasma frequency is located exactly in this frequency band, as well as its extremely large third-order nonlinear parameters [1] - [3] . In addition, its linear and nonlinear properties are both highly tunable via electrical bias or chemical doping. As a result, graphene based devices can have a reconfigurable THz performance. Furthermore, optically pumped graphene can lead to coherent amplification and radiation of THz signals, becoming an active material that can be characterized by gain performance [4] . However, graphene suffers from weak light-matter interactions with the incident electromagnetic waves mainly due to its single atom thickness. Interestingly, hyperbolic metamaterials (HMM) with anisotropic and uniaxial properties are widely used to control and enhance the light-matter interactions. In our talk, we will demonstrate that amplification and nonlinear effects can be dramatically enhanced by ultrathin reconfigurable HMM based on graphene [4] .