基于激光等离子体加速的自由电子激光研究新进展

激光等离子体加速器能够在cm尺度内产生GeV量级的高品质电子束，为研制台式化自由电子激光提供驱动源。但是受限于激光等离子体加速中的难点和现有技术发展，电子束的品质难以达到自由电子激光的需求，尤其在稳定性、发散角和能散等方面，阻碍了台式化自由电子激光的研制。介绍了基于激光等离子体加速器的自由电子激光的最新进展，整理了目前高增益自由电子激光实验过程中存在的主要挑战和对应的解决方案与实验进展，并展望未来的发展方向。最近的研究结果证明，通过控制和优化激光等离子体加速器的注入和加速过程产生的高品质电子束可以在指数增益区域实现自发辐射放大，产生高增益的辐射，这也推动基于激光等离子体加速器的自由电子激光研究进入了一个新的阶段。

Research progress of free electron laser based on laser plasma acceleration

Laser plasma accelerator can accelerate electron beams to GeV level within a few centimeters, which provides a driving source for the development of table-top free electron laser. However, due to the difficulties in laser plasma acceleration and the development of existing technology, the quality of electron beam is not high enough to realize free electron laser, especially in the aspects of stability, divergence and energy spread of electron beam, which present substantial obstacles to the development of compact free electron laser. In this paper, the latest research progress of free electron laser based on laser plasma accelerator is introduced, the main challenges in the experiment for high gain free electron laser are analyzed, then corresponding solutions and experimental progress are summarized, and the future development is prospected. A recent research shows that the high-quality electron beam produced by controlling and optimizing the injection and acceleration of laser plasma accelerator can achieve spontaneous emission amplification and produce high gain radiation in the exponential gain regime, which promotes the research for free electron laser based on laser plasma accelerator to a new stage.