该研究组利用范德华异质结构中的混合拓扑极化激元，演示了中红外频率时的栅极可调谐负折射。具体地说，研究团队在部分用石墨烯修饰的α-MoO3薄膜中看到了广角负折射极化激元，正在进行可逆的平面纳米聚焦。它们原子厚度的异质结构削弱了界面上的散射损失，同时通过电门控实现正向折射到负折射的主动可调转变。
研究人员提出了极化激元负折射作为一个有前途的红外应用平台，如电可调超分辨率成像，纳米级热调控，增强分子传感和片上光学电路。
据悉，负折射为分子传感和热辐射应用提供了一个操纵中红外和太赫兹辐射的平台。然而，基于超材料和等离子体介质的实现面临着光学损耗、有限的空间限制以及在该光谱范围内缺乏主动可调性的挑战。
附：英文原文
Title: Gate-tunable negative refraction of mid-infrared polaritons
Author: Hai Hu, Na Chen, Hanchao Teng, Renwen Yu, Mengfei Xue, Ke Chen, Yuchuan Xiao, Yunpeng Qu, Debo Hu, Jianing Chen, Zhipei Sun, Peining Li, F. Javier García de Abajo, Qing Dai
Issue&Volume: 2023-02-10
Abstract: Negative refraction provides a platform to manipulate mid-infrared and terahertz radiation for molecular sensing and thermal emission applications. However, its implementation based on metamaterials and plasmonic media presents challenges with optical losses, limited spatial confinement, and lack of active tunability in this spectral range. We demonstrate gate-tunable negative refraction at mid-infrared frequencies using hybrid topological polaritons in van der Waals heterostructures. Specifically, we visualize wide-angle negatively refracted polaritons in α-MoO3 films partially decorated with graphene, undergoing reversible planar nanoscale focusing. Our atomically thick heterostructures weaken scattering losses at the interface while enabling an actively tunable transition of normal to negative refraction through electrical gating. We propose polaritonic negative refraction as a promising platform for infrared applications such as electrically tunable super-resolution imaging, nanoscale thermal manipulation, enhanced molecular sensing, and on-chip optical circuitry.
DOI: adf1251
Source: https://www.science.org/doi/10.1126/science.adf1251