Dual‐Band Chiral Nonlinear Metasurface Supported by Quasibound States in the Continuum

Abstract

This paper presents an all-dielectric chiral metasurface composed of an array of two-layer distorted square structures with nanoholes. This metasurface can simultaneously generate dual-band opposite chiral responses, which can be attributed to the bound states in the continuum (BICs) and the distorted chiral structure. By combining the BICs with chirality, a dual-band chiral nonlinear metasurface and a chiral-sensing method are proposed. The simulated results show that the third harmonic generation (THG) conversion efficiency can reach the order of 10 −4 for two peaks with a peak-pump intensity of approximately 5.3 GW cm −2 in the near-infrared region. Moreover, the third-harmonic circular dichroism for each peak can reach up to 0.99 and -0.94, respectively. Furthermore, it is theoretically demonstrated that this metasurface can be used for chiral sensing with high sensitivities. These results provide new insights for linear and nonlinear spin-dependent applications.

Nonlinear chiral metaphotonics: a perspective

“…The authors demonstrated numerically that such structures can achieve near-unity TH CD in the vicinity of the quasi-BIC mode together with the enhancement of the overall TH signal. This concept was later applied to double-layer photonic crystal slabs with asymmetric dimer-shaped holes in Si film 89 …”

“…This concept was later applied to double-layer photonic crystal slabs with asymmetric dimer-shaped holes in Si film. 89 The pioneering experimental observations of chiral nonlinear BICs for strong nonlinear CD have been reported only recently. 46,90 Shi et al 46 studied an Si metasurface composed of a square lattice of asymmetric meta-atoms, with the schematic and SEM images shown in the top and bottom left panels of Fig.…”

Dual-wavelength chiral metasurfaces based on quasi-bound states in the continuum

“…Meanwhile, the twisted metasurface system composed of a series of stacked identical metasurfaces arranged with a rotation angle can exhibit evident optical chirality [39]. Consequently, empowered by quasi-BICs, a stacked metasurface system with a pair of twisted metasurfaces have been proposed to achieve spectrum selective chirality at a single wavelength [40,41], two wavelengths [42] or multi wavelengths [43]. However, the chirality of these metasurfaces at these resonant wavelengths cannot be independently controlled by adjusting the structural parameters.…”