微纳金属结构矢量光场变换及在光学模拟计算中的应用

Optical analog computing offers high-throughput low-power-consumption operation for specialized computational tasks. Traditionally, optical analog computing in the spatial domain uses a bulky system of lenses and filters. Recently spatial field transformation with optical nanostructures becomes a rather attractive topic in nanophotonics researches, which realizes the miniaturization of such bulky computing system down to a wavelength or even subwavelength scale. In this program, we focus the investigation on the vectorial-field transformation when light excites surface plasmon polaritons (SPPs) in metallic nanostructures. We will study the underlying physical mechanisms of vectorial-field transformation and realize spatial analog operation by manipulating the coupling and the interference involved with the SPP excitation. Additionally, we design, fabricate, and characterize analog spatial field processers reconfigurable with multiple operation frequencies. The aim of such a proposed vectorial-field transformation is to overcome the limitation of single polarization and single operation frequency in the scalar-field scheme. As great advantages, the vectorial-field optical analog computation not only offers more degrees of freedom with different polarizations but also enables direct measurement of vectorial quantities, such as angular orbital momentum of optical vortex vectorial field. Such a study is of great significance to understand vectorial-field transformation with nanostructures, and furthermore promises a variety of applications regarding new generation optical information processing.

基于微纳结构的空间光场变换是光场调控中新的研究领域，其目标是将传统基于透镜的4f光信息处理系统从宏观量级尺寸压缩至光波长甚至亚波长量级，从而为光信息处理提供一种全新的方法。本项目在前期标量光场变换工作的基础上，研究面向光学模拟计算的矢量光场变换。提出使用空间模式耦合干涉原理，设计基于表面等离激元的、亚波长厚度的矢量光场模拟运算器件。同时将采用微纳加工工艺制备矢量光场模拟运算器件，演示并拓展其在光信息处理方面的应用。这些新原理和器件将突破目前光场变换中单一偏振、单一频率的限制，不仅为光学模拟计算提供更多的自由度，而且将能够直接实时测量、表征矢量光场的特殊物理量，如轨道角动量等。本项目拟研究的矢量空间光场模拟运算涉及复杂的结构特性，是一种具有特定空间谱特征和分布的光场传播行为，它不仅对微纳光学研究具有重要意义，而且在新一代光信息处理中具有潜在的应用价值。

本项目研究了矢量光场变换实现空间光学模拟运算的物理机理和应用，在国际光学领域刊物上共发表论文12篇（其中ESI高被引论文2篇），包括Nature Communications 1篇，Physical Review Letters 1篇, Physical Review Applied 4篇，Optics Letters 2篇。项目培养博士生4人。项目取得代表性研究成果总结概括为三个方面： 1）针对标量模拟运算器件只能对单一偏振光场进行空间微分运算的不足，提出了利用光学自旋霍尔效应设计微分器件，可对s/p偏振分别进行一阶空间微分运算，并实验上展示了对图像的边缘提取；2）设计并制备了基于拓扑非平庸传递函数的空间光场微分器，实现了多波长的模拟运算器件，并展示了其在各向同性图像边界实时检测方面的应用；3）基于矢量光学模拟计算，分别提出了相位定量测量技术、空间光调制器校准方法和计算散度的空间光场模拟运算器件等具体应用。这些新原理不仅突破了标量光场模拟计算的限制和不足，而且对于发展超快光信息技术处理具有重要应用价值。