与传统化学颜料滤光片相比，基于微纳光学结构的滤光片所呈现的颜色不仅纯度高、亮度大而且不易褪色，更重要的是不会对环境产生污染。超构表面结构色滤光片因在光学装饰、彩色显示、成像以及光伏等领域存在潜在的应用价值而受到广泛关注。随着微纳加工技术的进步，基于不同共振机理的超构表面结构色滤光片相继实现。本文首先介绍了基于超构表面产生结构色的三种典型共振机理，然后介绍超构表面结构色滤光片在全彩显示、全息成像、信息加密以及彩色光伏器件等领域的应用现状，最后对超构表面结构色滤光片的发展前景进行展望。

High-index dielectric resonators support different types of resonant modes. However, it is challenging to achieve a high-Q factor in a single dielectric nanocavity due to the non-Hermitian property of the open system. We present a universal approach of finding out a series of high-Q resonant modes in a single nonspherical dielectric cavity with a rectangular cross section by exploring the quasi bound-state-in-the-continuum (QBIC). Unlike conventional methods relying on heavy brutal force computations (i.e., frequency scanning by the finite difference time domain method), our approach is built upon Mie mode engineering, through which many high-Q modes can be easily achieved by constructing avoid-crossing (or crossing) of the eigenvalue for pair-leaky modes. The calculated Q-factor of mode TE(5,7) can be up to Q_theory = 2.3 × 10⁴ for a freestanding square nanowire (NW) (n = 4), which is 64 times larger than the highest Q-factor (Q_theory ≈ 360) reported so far in a single Si disk. Such high-Q modes can be attributed to suppressed radiation in the corresponding eigenchannels and simultaneously quenched electric (magnetic) field at momentum space. As a proof of concept, we experimentally demonstrate the emergence of the high-Q resonant modes [Q ≈ 211 for mode TE(3,4), Q ≈ 380 for mode TE(3,5), and Q ≈ 294 for mode TM(3,5)] in the scattering spectrum of a single silicon NW.

The study of resonant dielectric nanostructures with a high refractive index is a new research direction in the nanoscale optics and metamaterial-inspired nanophotonics. Because of the unique optically induced electric and magnetic Mie resonances, high-index nanoscale structures are expected to complement or even replace different plasmonic components in a range of potential applications. We study a strong coupling between modes of a single subwavelength high-index dielectric resonator and analyze the mode transformation and Fano resonances when the resonator’s aspect ratio varies. We demonstrate that strong mode coupling results in resonances with high-quality factors, which are related to the physics of bound states in the continuum when the radiative losses are almost suppressed due to the Friedrich–Wintgen scenario of destructive interference. We explain the physics of these states in terms of multipole decomposition, and show that their appearance is accompanied by a drastic change in the far-field radiation pattern. We reveal a fundamental link between the formation of the high-quality resonances and peculiarities of the Fano parameter in the scattering cross-section spectra. Our theoretical findings are confirmed by microwave experiments for the scattering of high-index cylindrical resonators with a tunable aspect ratio. The proposed mechanism of the strong mode coupling in single subwavelength high-index resonators accompanied by resonances with high-quality factors helps to extend substantially functionalities of all-dielectric nanophotonics, which opens horizons for active and passive nanoscale metadevices.