半导体基超表面的光学非线性增强机制及应用

The metasurfaces constructed by fabricating metal nanostructures on semiconductor may acquire optical nonlinearity superior to that of traditional nonlinear materials, whereas it needs exploration to comprehend mechanisms of nonlinearity enhancement. In this project, we will investigate for this type of metamaterials the mechanisms that effects of hot carrier injection and excitonic and intersubband oscillators contribute to the enhanced optical nonlinearity, and take their advantage to achieve optimized structures. We will (1) study a semi-classical theoretical model for the optical nonlinearity enhancement effect and take the influence of the nonlocal effect into account; (2) design low dimensional semiconductor-based metasurfaces to obtain superior optical nonlinearity; and (3) investigate their characteristics of optical nonlinearity by z-scan and pump probe experiments and improve theoretical modeling and design with these results. This project has merits including (1) the study of interactions between semiconductor and metal nanostructure for optical nonlinearity enhancement, and (2) band structure design for coupling low dimensional semiconductor electronic structures to surface plasmons for achieving optical nonlinearity, which is further studied in characterization experiment. Semiconductor-based metasurfaces break the limit of material choice met by traditional nonlinear materials, exhibit engineering advantages of artificial materials, and have prospective application on integrated chips. The exploration in this project will improve the understanding of optical nonlinearity enhancement effects of metasurfaces, and promote the technological advancement of nonlinear metasurfaces.

在半导体上制备金属纳米结构构建的超表面可获得超越常规非线性材料的光学非线性，而其增强机制尚需进一步探索与理解。本项目理论与实验研究这类超表面结构中热载流子注入、激子态及子带间跃迁振子等效应对增强光学非线性的贡献机制，进而加以利用并获得优化结果。在项目中拟①研究增强光学非线性效应的半经典理论模型及非局域效应的影响；②设计基于低维半导体的超表面结构，获得超高光学非线性系数；③通过Z扫描、泵浦探测等手段研究其非线性特性，完善理论模型与设计。特色在于①利用半导体与金属纳米结构相互作用及其增强光学非线性的机制；②通过能带设计获得低维半导体电子结构与表面等离子互耦，优化光学非线性效应，实验研究其特性。半导体基超表面突破了传统非线性材料的选择局限，体现了人工材料的可工程性，在集成芯片方面具有重要的应用前景，本项目的探索工作将增进人们对超表面的光学非线性增强效应的认识，促进非线性超表面技术的发展。

基于半导体纳米结构设计超表面可获得超越常规非线性材料的光学非线性响应，而其物理起源和增强机制需进一步探索与理解。本项目将纳米结构的亚波长局域增强效应和半导体的强光学非线性效应及易操控特性等优点相结合，理论与实验两方面研究半导体基超表面的光学非线性效应。我们建立了半导体的带内跃迁光学非线性的物理机制模型，基于电磁场多级分解理论，研究了镶嵌金纳米硅盘的电磁共振与等离子共振耦合的电场增强。我们发展了飞秒激光加工和纳米小球自组装掩膜技术，制备了超表面样品，实现了光学非线性的增强。此外，我们设计了金属-半导体的肖特基结构，研究了其热电子探测的应用。在光学非线性表征方面，我们出光束传播衍射模型以提高Z扫描手段表征光学非线性的准确性。半导体基超表面突破了传统非线性材料的选择局限，体现了人工材料的可工程性，在集成芯片方面具有重要的应用前景，本项目的探索工作增进了人们对超表面的光学非线性增强效应的认识，促进了非线性超表面技术的发展。