基于超构表面的非线性光学调控的新原理探索

光的偏振态和频率是光的重要特性，调控这些特性在微纳光子学和量子信息学中有广泛的应用。本项目拟围绕亚波长微纳结构制备和光学性质，发展新的超构材料的设计原理，通过调节微结构的材料参数和几何结构参数调控结构单元的附加相位，特别是设计和筛选具有高非线性光学系数的薄膜材料作为超构材料的衬底，研究电磁波与该类复合结构作用后的波前传播规律，对电磁波的传播方向、相位、偏振态和频率实现调控。本项目拟从理论和实验两方面深入研究超构表面的非线性光学效应，设计若干新的二维/三维微纳结构，通过引入特定的相位梯度实现不同于入射光频率的多偏振态同时输出。实验上拟通过电子束光刻微加工和飞秒脉冲激光双光子聚合三维直写技术实现样品制备，并获得较高的非线性转化率。在研究物理新原理和机制的同时，期望为集成光学、量子信息编码和传输提供集成度高、体积小、效率高的光学器件原型。

Polarization and frequency are intrinsic features of light with profound applications in nano photonics and quantum information. This project is targeting on the physics mechanism of metasurfaces and metamaterials in tuning the phase, polarization, frequency and wave vector of electromagnetic waves. Upon illumination each resonator diffracts light with a geometry-scaling-induced phase modulation. We plan to apply the phase modulation approach to metasurfaces loaded by highly nonlinear substrates made of MQW or semiconductor, establishing a platform to control the nonlinear wave front at will based on giant localized nonlinear effects. With electron beam lithography and two-photon absorption fabrication, we plan to fabricate several nonlinear metasurfaces and metamaterials for efficient second-harmonic radiation. The unit cell consists of an assembly of resonators with different structural parameters. Depending on the category and sequence of the elements in the unit cell, several second-harmonic beams with different polarization states can be simultaneously generated with any desired combination and propagation direction. This new approach provides new perspectives in generating arbitrary polarization states with high integration, and hence is enlightening in constructing qubit gates and developing quantum cryptography.