强流目标的DC-SRF-II光阴极驱动激光系统设计

为推动北京大学超导加速器实验装置不断向强流目标迈进，提出100 W红外高重频光阴极驱动激光的设计方案，主放大器采用先进的光子晶体增益光纤，保证输出光束的质量。对激光系统中的关键问题，如各部分功率指标、脉冲展宽和压缩、激光耦合等进行了设计，并且考虑了激光的非线性影响。为实现强流加速器开机运行所必备的诊断模式，也提出了对于高重频激光进行两级选频的独特设计方案。将高速的SOA光开关和低速的声光调制器相结合，产生宏脉冲结构的输出激光，从而实现加速器在诊断模式下的运行。

Design of the photocathode drive laser system for high current electron beam operation of DC-SRF-II gun

We present the design of a 100 W high repetition rate photocathode drive laser system for realizing high average current operation of the superconducting accelerator at Peking University. To achieve good beam quality and reliability, we choose photonic crystal fiber (PCF) as the gain medium of the main amplification unit. In addition, we address several key issues for the drive laser system, including the evaluation of the output power of each amplification unit, the design of pulse stretcher and compressor, the optimization of free space coupling setups for pump pulse and seed pulse, etc. We also combine a high-speed semi-conductor optical amplifier (SOA) optical switch with a low-speed acousto-optic modulator (AOM) to achieve the necessary diagnostic mode for the intense electron beam accelerator. This unique design is of importance for the photocathode drive laser with the repetition rate around or above 100 MHz.