基于超表面结构的涡旋电磁波非线性电磁仿真与应用研究

Vortex electromagnetic waves have enormous potential applications in the fields of microwave communication, optical micro-operation, optical microscopic imaging and quantum information. Instead of traditional lens, using the nonlinear metasurfaces to generate the optical vortex provides a new promising way for ultra-compact optical device and increasing the information capacity. At present, research on the generation of nonlinear vortex electromagnetic waves from metasurfaces lacks a precise, fast and universal solver that can simultaneously simulate the linear and nonlinear electromagnetic properties of metallic metasurface. In this proposal, by introducing the hydrodynamic model in the classical electromagnetic theory, the time-domain finite-difference method will be adopted to model the linear and nonlinear electromagnetic response of metallic structures. Based on the multi-physics electromagnetic solver, the nonlinear electromagnetic manipulation principle of metallic metasurface will be studied, the new mechanism of generating optical will be explored. The research of our proposal can not only provide a theory basis and technical support for the design of vortex field and nonlinear metasurface, but also expand the application field of traditional computational electromagnetic.

涡旋电磁波在微波通信、光学微操作、光学显微成像和量子信息等领域具有巨大应用潜力。使用非线性超表面替代传统透镜产生涡旋光场，为光学器件微型化和灵活的相位调控提供了新手段，同时非线性涡旋光场提高了信息载量。目前，关于超表面非线性涡旋电磁波产生的研究，缺乏可以同时实现金属超表面涡旋波线性和非线性电磁特性仿真的精准、快速和通用的求解器。项目基于时域有限差分法，在经典电磁理论框架下引入自由电子气流体模型，对金属结构线性和非线性电磁响应电磁建模；结合所建模型深入研究金属超表面的非线性电磁调控机理，探索基于非线性超表面产生涡旋光场的物理新机制。项目的成果不仅为涡旋光场、超表面理论和应用发展提供理论工具，而且拓展了传统计算电磁学应用领域。

目前已有的针对金属超表面涡旋光场线性与非线性电磁仿真的求解器，存在模型误差大、算法效率低、未充分验证其有效性、守恒性和收敛性等缺点。通过该项目的资助，研究按照计划顺利进行，超过项目预期成果，目前已开发一款等离子体微纳结构电磁仿真软件包，可以对等离子体微纳结构的线性和非线性电磁响应进行精准仿真，通过CUDA并行技术对算法进行加速。软件包能计算任意形状、任意周期、准周期金属纳米天线阵列的非线性电磁响应。同时能给出基波和不同谐波下的近场分布、远场辐射方向图、散射/消光/吸收截面、传输/反射系数等后核心工程参数。通过该软件包，建立并完善使用金属超表面非线性响应产生涡旋光场的理论和工程设计方案，为实验提供有效的理论工具（与实验课题组天津大学韩家广教授及香港大学张霜）。

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