基于表面等离激元的碱金属锑化物光阴极研究

High brightness, high average current electron sources are a key element of new types of x-ray sources such as the free electron lasers (FELs), attracting much attention of scientists of the world. With the virtue of high quantum efficiency (~10%), low thermal emittance (~0.5 mm-mrad/mm), driven by green light, bialkali photocathode holds promise in high brightness, high average current electron sources. However, with the increasing demand, the performance of the photocathode is required to be improved. The surface plasmon polaritons (SPPs) can enhance the couple between the electrons and photons, reducing the reflectivity of the device, modulating the distribution of the incident laser power density. In this project, the surface plasmon polaritons are introduced to enhance the performance of the bialkali photocathode photoncathode. The characteristics of the bialkali photocathode with SPPs is to be studied based on the theoretical analysis, software of electric magnetic field and Monte Carlo simulation code. And the parameters of the photocathode is to be optimized. Then the photocathode will be fabricated and tested to demonstrate the performance of the introduction of the SPPs.

在先进光源自由电子激光的驱动下，发展高亮度、高平均流强电子源已然成为国际上的一个热点课题。锑钾铯光阴极具有量子效率高（~10%）、本征热发射度低（~0.5mm-mrad/mm）、绿光驱动等优点，是一种极具潜力的高亮度、高平均流强电子源。然而，随着需求提高，对其性能也提出更高要求。表面等离激元能够增强光子和电子耦合，降低反射率，调控界面处电磁场能量分布。本项目拟将表面等离激元引入至锑钾铯光阴极中，以提高阴极材料对驱动激光的吸收、调控阴极内初始光电子分布，从而提升光阴极性能。本项目将在理论分析的基础上，结合电磁场仿真软件及蒙特卡洛仿真对表面等离激元引入后光阴极的光电子发射特性进行研究，进而优化光阴极参数，完成所设计光阴极加工制备及测试，采用实验手段验证表面等离激元引入对光阴极性能提升效果。

在先进光源自由电子激光的驱动下，发展高亮度、高平均流强电子源已然成为国际上的一个热点课题。本项目提出引入表面等离激元提升锑钾铯光阴极量子效率，从理论仿真及实验两方面对表面等离激元的引入效果进行研究。在本项目执行期间，搭建了表面等离激元增强光阴极光电子发射仿真模型，基于python语言编写了仿真程序。仿真结果指出表面等离激元引入后锑钾铯光阴极量子效率可提升2~3倍，光阴极热发射度基本未变。实验上，开展了表面等离激元增强锑钾铯光阴极制备。开展了采用多孔氧化铝掩膜方式大面积低成本微纳阵列制备研究，经测试所制备基底可实现表面等离激元激发。开展了K/Cs共蒸锑钾铯光阴极制备工艺研究，获得了稳定的工艺参数，所制备光阴极量子效率可稳定至4~5%。开展了表面等离激元增强锑钾铯光阴极制备及测试，实验上光阴极量子效率增长不明显。经分析主要原因实际制备过程锑钾铯光阴极参数与仿真中采用的理想值存在差异有关。下一步将开展工艺参数优化，调控制备的锑钾铯光阴极参数，同时开展不同锑钾铯参数下光阴极性能仿真研究，进一步优化光阴极性能参数。