用于高平均功率ERL的双波长光阴极驱动激光系统实验研究

The best method of beam current ramping while ERLs trun on is to gradually increase the repetition of electron bunches and keep the full bunch charge. But this is an international problem unresolved for the lack of suitable EO switch.The project put forward an innovative type of the photocathode laser,and try to solve the problem. The project intends to adopt a high-speed fiber-optic waveguide modulator to change repetition rate of the laser into the desired pulse sequence, meanwhile, using another identical modulator, to produce the filling pulse sequence used to fill in the gaps along the desired laser pulse sequence. Then to combine the two pulse sequences, a new pulse sequences with the same time structure as the pulse sequence from the laser before modulation regardless what repetition rate the desired pulse sequence is. So the multi-stage cascaded fiber optics amplifiers can maintain their stable operating condition since its input stays the same. The key important is the Ytterbium-doped fiber laser we built has a wide range of gain spectrum, therefore we can chose different optical wavelengths for the said two pulse sequences. After the amplifiers, we can separate them with a high extinction ratio filter. To build a laser system with this innovative idea can obtain electron bunches with a wide range repetition, so the experimental study is of great significance for the ERL facility in the future.

高平均功率ERL开机时，需要逐步提高流强。最佳流强渐增方法是，保持电子束团的电荷量不变，逐步提高其重复频率，但至今这仍是无法解决的国际难题。本项目提出一种创新的驱动激光结构，试图解决这一问题。采用高速光波导调制器，开关高重复频率激光脉冲，改变脉冲重复频率，得到一个期望的激光脉冲序列。用另一个同样的波导调制器，反相调制出一个填充的脉冲序列，用来填充期望脉冲序列中缺失的激光脉冲。只要把这样的两路脉冲序列合并，无论期望的脉冲序列如何变化，填充后的脉冲序列仍然保持了调制前的脉冲结构，保证了多级激光放大器能够稳定工作。选择有很宽增益光谱范围的掺镱光纤激光，可以放大这两个激光波长。因为放大后的激光脉冲波长不同，可以用高消光比的滤光片分离出期望的激光脉冲。这一激光结构的创新，使得大范围调整电子束团重复频率成为可能，该项目的研究，将对未来高平均功率ERL装置的建设具有重要意义。

高平均功率ERL 开机运行时，目前国际上公认的最佳流强渐增方法是，电子束团的电荷量不变，逐步提高其重复频率，但这至今仍是一个无法解决的国际难题。本项目提出一种创新的驱动激光结构，解决这一问题。对高重复频率激光进行脉冲选取，调制出一个所需的激光脉冲序列，同时用反相调制的另一个冲序列，来填充所需的脉冲序列中缺失的激光脉冲。只要把这样的两路脉冲序列合并，无论期望的脉冲序列如何变化，填充后的脉冲序列仍然保持了调制前的脉冲结构，保证了多级激光放大器能够稳定工作。放大后的激光脉冲根据波长不同，用高消光比的滤光片分离出期望的激光脉冲。这一激光结构的创新，将对未来高平均功率ERL 装置和高平均功率超快激光的高速调制加工具有重要意义。通过与国内外调制器厂家交流，项目选用普克尔盒电光调制器，产生互补结构的双波长激光脉冲，能够达到1:1000的开关消光比。