时间地点：2023年4月11日周二16:00，理科楼C302

Abstract：To confine light at the nanoscale and enhance light-matter interactions, scientists are exploring the vast library of polaritonic modes in van der Waals (vdW) materials. In this talk, I will discuss the manipulation of nanoscale-confined polaritons in anisotropic vdW materials (h-BN, MoO₃, V₂O₅), specifically their dispersion, propagation and optical losses. With the help of state-of-the-art infrared nano-imaging technique, we demonstrate that vdW polaritons exhibit exotic phenomena (e.g. anomalous refraction, negative reflection, high-momentum interference etc.) and unique properties (e.g. highly collimated propagation, enhanced photonic density of states, indefinite dispersion etc.). By stacking and twisting these materials, we enable the diffraction-free lensing and nano-focusing of mid-infrared light at the nanoscale. We also design tunable polaritonic nanoantennas with ultra-narrow resonances, which could find applications in active nanooptics and (bio)-sensing.

Biography：段嘉华，教授，博士生导师。2018年毕业于中国科学院物理研究所，之后在西班牙奥维耶多大学从事博士后工作。2023年至今为北京理工大学教授，入选国家海外高层次人才引进计划青年项目、北京理工大学特立青年人才项目。主要从事深亚波长尺度光场能量传播调控、低维量子材料中新奇光学现象及其微观物理机制解读、纳米光学器件设计等方面研究。多项工作入选西班牙皇家物理学会年度最具价值论文奖，发表于Nature Materials、Nature Reviews Physics、Nature Communications、Science Advances、Advanced Materials、Nano Letters等期刊。