Second harmonic generation in plasmonic metasurfaces enhanced by symmetry-protected dual bound states in the continuum

We numerically investigate linear and nonlinear optical responses in metasurfaces consisting of Au double-gap split ring resonators (DSRRs). Symmetry-protected dual bound states in the continuum (BICs) in such plasmonic metasurfaces are observed at the near-infrared optical regime. Efficient second harmonic generation (SHG) is obtained at the quasi-BIC models due to the symmetry broken. The optimized SHG responses are obtained at the critical couplings between radiation and nonradiation processes at the linearly x- and y-polarized light, respectively. High conversion efficiency of SHG of a value 10-6 is arrived at the fundamental intensity of 10 GW/cm2 at the quasi-BIC wavelength under the y-polarized illumination. Large extrinsic and tunable chirality of linear and nonlinear optical responses empowered by quasi-BICs is acquired in asymmetry metasurfaces at oblique circularly polarized incidence. The results indicate that the plasmonic metasurfaces of symmetry-protected BICs at the near-infrared optical regime have great potential applications in the on-chip efficient frequency conversion, and the linear and nonlinear chiral manipulation. & COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

We numerically studied the linear and nonlinear optical responses in metasurfaces made of Au double-gap split ring resonators (DSRRs). We observed symmetry-protected dual bound states in the continuum (BICs) in these plasmonic metasurfaces at near-infrared optical frequencies. Efficient second harmonic generation (SHG) was achieved at the quasi-BIC modes due to symmetry breaking. Our results suggest that these plasmonic metasurfaces have great potential applications in on-chip efficient frequency conversion and linear and nonlinear chiral manipulation.