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We propose and investigate a wideband nonlinear graphene-based terahertz (THz) metasurface that enables mode selective dual-band four-wave mixing (FWM) within a single resonant platform. The metasurface consists of three concentric graphene resonance rings placed above a metallic ground plane and separated by a thin dielectric spacer. Strong lateral plasmonic coupling among the rings leads to plasmonic mode hybridization, giving rise to a broad linear resonance band with a bandwidth of nearly 1 THz spanning from 1.5 to 2.5 THz and strong electromagnetic field enhancement across the entire band. Despite its wideband absorption response, the nonlinear emission remains spectrally selective, resulting in two dominant FWM output peaks corresponding to radiative hybrid plasmonic modes of the metasurface. Owing to graphene’s strong third-order nonlinearity combined with resonance enhanced local fields, efficient dual-band FWM generation is achieved at relatively low input intensities on the order of 100kWcm −2 . Furthermore, the nonlinear response exhibits robustness against variations in the incident angle and can be actively tuned via the graphene Fermi energy, enabling dynamic control of both the resonance characteristics and nonlinear frequency conversion. These results are new and demonstrate that wideband nonlinear graphene metasurfaces provide a compact and versatile platform for mode selective dual-band THz frequency mixing, with potential applications in tunable THz frequency conversion, nonlinear wave mixing, and compact FWM-based THz devices.
Sahu et al. (Wed,) studied this question.