意大利国家核物理研究所Della Valle, Giuseppe团队近日研究了利用瞬态光学对称破缺实现连续介质中超表面准束缚态的超快切换。该研究于2025年7月8日发表在《光：科学与应用》杂志上。

在光子结构中，连续介质中的束缚态（BICs）近年来引起了基础和应用研究的极大兴趣。准BIC泄漏模是由超表面的面内对称性破缺引起的，由于其高质量因子，其比例为不对称参数的平方反比，因此与应用尤为相关。

研究组从理论上提出了一种创新的方法，通过半导体超表面的光诱导对称性破缺在亚皮秒时间尺度上打开准BIC。利用光激发热载流子在单元原子纳米尺度上分布的空间不均匀性，获得了预期的效果。在他们的模拟中，准BIC状态表现为传输的超急剧下降，在泵到达时出现，并在载流子的扩散时间尺度内完全消失。他们的策略允许设想具有可切换的高Q共振的可重构平台，具有超越载流子弛豫限制的超快恢复，这是以前的典型策略。

附：英文原文

Title: Ultrafast switching of a metasurface quasi-bound state in the continuum via transient optical symmetry breaking

Author: Crotti, Giulia, Schirato, Andrea, Pashina, Olesiya, Sergaeva, Olga, Petrov, Mihail, De Angelis, Costantino, Della Valle, Giuseppe

Issue&Volume: 2025-07-08

Abstract: In photonic structures, bound states in the continuum (BICs) have recently attracted huge interest in both fundamental and applied research. Quasi-BIC leaky modes resulting from in-plane symmetry breaking in metasurfaces are particularly relevant to applications, due to their high quality factor, which scales as the squared inverse of the asymmetry parameter. Here, we theoretically propose an innovative approach to switch on quasi-BICs on sub-picosecond timescales via optically induced symmetry breaking in semiconductor metasurfaces. The desired effect is granted by exploiting the spatial inhomogeneities in the distribution of photo-excited hot carriers at the single meta-atom nanometric scale. In our simulations, the quasi-BIC state manifests itself as an ultra-sharp dip in transmission, emerging upon pump arrival, and disappearing completely within the carriers’ diffusion timescale. Our strategy allows to envision reconfigurable platforms with switchable high-Q resonances, with ultrafast recovery beyond the limits of carrier relaxation, typical of previous approaches.

DOI: 10.1038/s41377-025-01885-z

Source: https://www.nature.com/articles/s41377-025-01885-z