Second harmonic generation in plasmonic metasurfaces enhanced by symmetry-protected dual bound states in the continuum
Di Liu, Yingying Ren, Yanyan Huo, Yangjian Cai, Tingyin Ning
Abstract
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/cm 2 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.