超表面中的连续谱束缚态研究进展

Research Progress of Bound States in the Continuum in Metasurfaces

摘要: 连续谱中的束缚态(Bound States in the Continuum, BICs)是一类特殊的光学局域态，其本质是在开放的辐射环境中存在但不与连续辐射通道发生能量交换的束缚模式。由于理论上具有无限大的品质因子(Quality Factor, Q)，BICs打破了传统光学谐振结构受到辐射损耗限制的瓶颈，为实现高性能光子器件提供了新的物理机制。近年来，随着超表面的快速发展，利用人工微纳结构调控光场成为构建和研究BICs的重要途径。本文围绕超表面中的BICs物理机制展开综述，首先介绍连续谱束缚态的基本概念及其形成条件，随后重点讨论Friedrich-Wintgen干涉型BICs、对称保护型BICs以及偶然型BICs的物理来源。在此基础上，进一步介绍利用结构扰动产生准连续谱束缚态(quasi-BICs)，以及通过对功能材料施加外部激励实现BIC动态调控的方法。最后，本文讨论当前BICs超表面研究面临的实际限制，并展望其在动态调控和集成光子学方向的发展前景。

Abstract: Bound States in the Continuum (BICs) are a special type of optical localized states, whose essence is the existence of a confined mode in an open radiation environment without energy exchange with the continuous radiation channel. Due to their theoretically infinite quality factor (Q), BICs break the bottleneck of traditional optical resonant structures that are limited by radiation losses, providing a new physical mechanism for the realization of high-performance photonic devices. In recent years, with the rapid development of metasurfaces, the use of artificial micro-nano structures to control the light field has become an important approach for constructing and studying BICs. This article provides a review of the physical mechanism of BICs in metasurfaces, starting with the basic concepts and formation conditions of continuum bound states, followed by a focus on the physical origins of Friedrich-Wintgen interference-type BICs, symmetric protected-type BICs, and accidental-type BICs. On this basis, it further introduces the generation of quasi-BICs through structural perturbations and the method of achieving dynamic control of BICs by applying external excitation to functional materials. Finally, this article discusses the current practical limitations of BICs research in metasurfaces and looks forward to its development prospects in dynamic control and integrated photonics.