Nonlinear and Amplification Response with Asymmetric Graphene-based Coherent Perfect Absorbers

This work reports a novel asymmetric bifacial graphene metasurface design exhibiting broadband coherent perfect absorption (CPA) at low terahertz (THz) frequencies. Nonlinear CPA performance without resorting to optical nonlinearities, as well as amplification are demonstrated based on wave interference phenomena taking place in this subwavelength structure. The proposed design is composed of two graphene square patch arrays with different dimensions stacked over an ultrathin dielectric substrate. Asymmetric reflection in a broad frequency range is obtained that leads to the presented broadband and nonlinear CPA response and amplifying performance. The proposed ultrathin broadband CPA device is expected to be an important component to several new on-chip THz communication devices, such as sensors, coherent detectors, all-optical modulators, and small-signal amplifiers.