CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Science. 2023 Feb 10;379(6632):558-561. doi: 10.1126/science.adf1251. Epub 2023 Feb 9.
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-MoO 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.
负折射为分子传感和热辐射应用提供了一个操控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方式在该光谱范围内存在光学损耗、有限的空间限制和缺乏主动可调谐性等挑战。我们在范德瓦尔斯异质结构中使用混合拓扑极化激元演示了中红外频率下的栅控负折射。具体来说，我们在部分被石墨烯修饰的α-MoO 薄膜中可视化了宽角度负折射极化激元，它们经历了可逆的平面纳米级聚焦。我们的原子层厚异质结构削弱了界面处的散射损耗，同时通过电门控实现了正常折射到负折射的主动可调谐转变。我们提出了基于极化激元的负折射，作为一种有前途的红外应用平台，例如电可调谐超分辨率成像、纳米级热操控、增强的分子传感和片上光电路。
