基于贵金属纳米孔/单层二维材料复合超构表面的二次谐波多维度调控

纳米结构中的二次谐波具有信号稳定、波长可调谐、相干性好、快速响应和偏振敏感等优点，是一种具有较好应用前景的新型纳米相干光源。如何提高纳米结构中二次谐波转换效率，同时对其进行多维度调控，是纳米光子学领域的研究热点之一。然而，由于贵金属中的二阶非线性极化率非常小，常用的贵金属超构表面在高效率二次谐波的产生方面存在严重不足。针对此问题，我们提出贵金属纳米孔/单层二维材料复合超构表面的新方案，通过设计和加工具有不同形状、尺寸和排列方式的贵金属纳米孔阵列调控入射基频光场的相位或偏振，再和具有高的二阶非线性极化率的单层二维材料作用产生二次谐波，以期提高二次谐波转换效率，同时对产生的二次谐波信号的相位、偏振和超快动态调制等进行多维度调控，实现各种二次谐波功能器件，如聚焦、全息成像、光束操控和矢量光束等，推动多功能的相干纳米光源在激光扫描显微成像、精密纳米探测和非线性微纳光学器件等中的应用。

Second harmonic generation (SHG) in nanostructures has the advantages of stable signal, tunable wavelength, coherence, fast response and polarization sensitive, thus is a new coherent light source of nanometer size with good application prospect. How to improve the SHG conversion efficiency in the nanostructures and tailor the SHG response in multi-dimensionality is one of the research hotspots in the area of nanophotonics. However, as the second-order nonlinear susceptibility in noble metal materials is very small, usual metal metasurfaces are of insufficient to generate high efficient SHG. Aiming at this problem, we proposed a new paradigm of metal nanoholes and 2D material monolayer hybrid metasurface. By designing and fabricating different shape, size and arrangement of metal nanohole array, the phase and polarization of incident fundamental light can be tailored. The tailored fundamental light interacting with the 2D material monolayer of high second-order nonlinear susceptibility is able to increase the SHG conversion efficiency and meanwhile control the SHG phase, polarization and ultra-fast process. Therefore, our proposed hybrid metasurface can be used to realize various SHG functional devices, such as focusing, hologram, beam control and vector beams, which promote the application of multi-functional coherent light source of nanometer size in scanning laser microscopy, precise nano-detection and nonlinear nanodevices.