Nonlinear properties of meta-dimer comprised of coupled ring resonators

We experimentally and theoretically investigate the nonlinear electromagnetic properties of an on-chip metamaterial system comprised of two coupled ring resonators (CRRs) as meta-dimer and a varactor loaded in between them as nonlinear medium inclusion. The resonant frequency of the anti-symmetric coupling mode of CRRs is sensitive to the input power and can be tuned to an extremely low frequency as the induced voltage gradient loaded on the varactor is maximized when the mode is excited. Nonlinear responses, including the shift of resonant frequency as well as hysteresis effects, are demonstrated experimentally in distinct ranges of input powers. The findings have potential applications in implementing subwavelength nonlinear components for integrated plasmonic nanocircuits or metactronics.