High-quality-factor dual-band Fano resonances induced by dual bound states in the continuum using a planar nanohole slab

Qing Mi,Yueke Wang,Shi Li,Yao Pei,Bin Ma,Chaoyu Yang,Tian Sang

doi:10.1186/s11671-021-03607-x

Abstract

In photonics, it is essential to achieve high-quality (Q)-factor resonances to improve optical devices’ performances. Herein, we demonstrate that high-Q-factor dual-band Fano resonances can be achieved by using a planar nanohole slab (PNS) based on the excitation of dual bound states in the continuum (BICs). By shrinking or expanding the tetramerized holes of the superlattice of the PNS, two symmetry-protected BICs can be induced to dual-band Fano resonances and their locations as well as their Q-factors can be flexibly tuned. Physical mechanisms for the dual-band Fano resonances can be interpreted as the resonant couplings between the electric toroidal dipoles or the magnetic toroidal dipoles based on the far-field multiple decompositions and the near-field distributions of the superlattice. The dual-band Fano resonances of the PNS possess polarization-independent feature, and they can be survived even when the geometric parameters of the PNS are significantly altered, making them more suitable for potential applications.

Highlights

Enhancing the interaction between light and matter, which is significant for improving performances of optical devices, can be realized by using high-quality (Q)factor responses [1]
The planar nanohole slab (PNS) consists of four nanoholes which can be shrunk (Δ < 0) or expanded (Δ > 0) with a shift distance of Δ along the diagonals of the superlattice, and Δ = 0 corresponds to simple lattice with period reduced to half, where each nanohole is located in the center of a quarter area of the superlattice
High-Q-factor dual-band Fano resonances can be realized by using a comparatively simple architecture of PNS based on the excitation of dual QBICs

Summary

Introduction

Enhancing the interaction between light and matter, which is significant for improving performances of optical devices, can be realized by using high-quality (Q)factor responses [1]. Metallic metamaterials are promising candidates for light manipulation, Fano resonance in plasmonic metamaterials typically suffers from low Q-factor in the visible to near-infrared (NIR) spectral regions due to the inherent ohmic losses in metal. All-dielectric metamaterials provide strong Mie-type resonances with induced displacement currents similar to those of plasmonic metamaterials, but feature less dissipative losses in the visible to NIR range [5]. The energy of the incident light can be highly localized in the dielectric nanostructures due to the excitation of the electric and/or magnetic dipolar resonances, which reduces the dissipative losses and achieves large resonant enhancement of both electric and magnetic fields. Bound states in the continuum (BICs) have emerged as the most promising scheme for achieving high-Q-factor responses in all-dielectric metamaterials [6, 7]. BICs reside inside the continuous spectrum of extended states but counterintuitively remain perfectly localized in space with theoretically infinite lifetime [8, Mi et al Nanoscale Res Lett (2021) 16:150

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Results

Conclusion