为了满足激光诱导等离子体(LPP)体制下极紫外(EUV)光源对CO2激光器提出的稳定性需求, 建立了简化的CO2激光传输系统模型, 根据光束稳定性需求对光束功率、指向和位置的监测与控制方法进行了理论和实验研究。根据高功率CO2激光传输系统特点, 在实验室内建立了上述光束监测和控制实验系统, 包括光束功率控制模块、光束指向控制模块和光束参数监测模块, 其中光束参数监测模块可实时测量光束功率、指向、尺寸及发散角等重要参数。仿真与实验结果表明: 光束功率控制模块对线偏振激光功率的控制接近1%~100%, 光束指向控制模块实现的光束指向稳定度在10 μrad以内, 可满足CO2激光驱动源的高稳定性要求。

To meet the high stability requirements of the extreme ultraviolet(EUV) light source driven by a CO2 laser under the Laser Produced Plasma(LPP) system, the simplified CO2 laser transmission system model is established. The monitoring and controlling methods of the beam power, pointing and the location are studied theoretically and experimentally based on the requirements of the beam stability. The beam monitoring and controlling experimental system is set up in a laboratory according to the characteristics of the high-power CO2 laser transmission system. The system includes a beam power control module, a beam pointing control module and a beam parameter monitoring module. The beam parameter monitoring module can accomplish the real-time measurements of beam powers, pointing, sizes and divergence angles and other important parameters. The simulation and experimental results show that the beam power control module can control the linearly polarized laser power from 1% to 100% and the beam pointing control module can control the beam pointing stability to be less than 10 μrad, which meets the high stability requirements of the extreme ultraviolet(EUV) lithography for the CO2 laser source under the Laser Produced Plasma(LPP) system.