该研究团队提出一种新方法，将非手性元结构在亚皮秒级时间内光学转化为瞬态手性介质，在可见光区域实现所需的手性，并揭示了其在等离子激元热电子不均匀产生中的应用潜力。作为概念验证，研究人员利用线偏振激光脉冲，实现了非手性元平台中自旋灵敏度的近乎完全转换，这一功能以非机械方式实现。该技术利用热电子的产生、扩散和弛豫动力学，呈现出全光学快速产生手性的特性，为按需自旋选择性的手性平台的超快光谱-时间构建开辟了全新途径。
据悉，手性是描述缺乏镜像对称性的一种几何性质。这一独特的特性使得光-物质相互作用中的光子自旋选择性成为可能，在立体化学、药物开发、量子光学和光偏振控制等领域具有重要意义。光学几何的多功能控制使得光学超材料在指定的光谱状态下成为工程化手性的有效平台。不幸的是，几何施加的限制只允许光子的一个圆偏振态有效地与手性元结构相互作用。这种限制激发了发现替代技术的想法，以快速和方便的方式动态地重新配置超材料的热效应响应。
附：英文原文
Title: Phototransformation of achiral metasurfaces into handedness-selectable transient chiral media
Author: Kim, Andrew S., Goswami, Anjan, Taghinejad, Mohammad, Cai, Wenshan
Issue&Volume: 2024-3-18
Abstract: Chirality is a geometric property describing the lack of mirror symmetry. This unique feature enables photonic spin-selectivity in light–matter interaction, which is of great significance in stereochemistry, drug development, quantum optics, and optical polarization control. The versatile control of optical geometry renders optical metamaterials as an effective platform for engineered chiral properties at prescribed spectral regimes. Unfortunately, geometry-imposed restrictions only allow one circular polarization state of photons to effectively interact with chiral meta-structures. This limitation motivates the idea of discovering alternative techniques for dynamically reconfiguring the chiroptical responses of metamaterials in a fast and facile manner. Here, we demonstrate an approach that enables optical, sub-picosecond conversion of achiral meta-structures to transient chiral media in the visible regime with desired handedness upon the inhomogeneous generation of plasmonic hot electrons. As a proof of concept, we utilize linearly polarized laser pulse to demonstrate near-complete conversion of spin sensitivity in an achiral meta-platform—a functionality yet achieved in a non-mechanical fashion. Owing to the generation, diffusion, and relaxation dynamics of hot electrons, the demonstrated technique for all-optical creation of chirality is inherently fast, opening new avenues for ultrafast spectro-temporal construction of chiral platforms with on-demand spin-selectivity.
DOI: 10.1073/pnas.2318713121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2318713121