基于相干电子源的量子自由电子激光的统计性质

We will study the statistical properties of the free electron laser based on Compton scattering. The coherent X-ray is generated via the collision of an ultrashort ultra-strong laser and a coherent electron source produced from a magneto-optical trap. We will study the single electron dynamics in a strong laser field from fully quantum mechanical approach, and then study the radiation mechanism of a coherent electron source in an ultra-strong laser field. Based on this, the statistical properties of a quantum free electron laser are studied. The coherent electron source is generated by laser exciting and ionizing the laser cooled rubidium atoms in a magneto-optical trap. The so-generated coherent electron source is accelerated up to a few tens of megaelectron volt (MeV), and then Compton scatters from an ultrashort ultra-strong laser field to generate high brightness, high flux X-ray free electron laser. In order to ensure the success of such a compact X-ray free electron laser, we study the dynamics and radiation mechanism of the electron in an ultra-strong laser field. We will make full use of the home-developed Orthogonal Coherent State approach, which was invented and improved during the past 10 years by the members of our research group to carry out semi-analytical calculation. On the meanwhile, we will develop full numerical simulation package. We hope, on one hand to understand the statistical properties of the free electron laser both theoretically and experimentally; on the other hand, we wish to resolve the discrepancy between the quantum optics approach and the statistical optics approach in calculating the high-order coherence. Our research is built up the on-going magneto-optical trap development in our laboratory, hence there is solid base for experimental study.

本项目研究基于康普顿原理的自由电子激光的统计特性。利用从冷原子阱中产生的相干电子源和超短超强激光相互作用而产生相干X射线源。我们会首先从全量子力学出发研究电子在强激光场中的行为，从而研究相干电子源在强激光中的发光特性。进而研究量子自由电子激光的统计性质。其中相干电子源的产生是通过激光电离冷原子阱中的激光冷却的铷原子而得到。 产生的相干电子源会被加速到几十兆电子伏特，然后与超快超强激光进行康普顿散射以产生高亮度，高通量的X射线自由电子激光。为了保证这种紧凑型X射线自由电子激光的成功，我们研究电子在强激光场中的行为和发光机制。我们会利用本团队在前十年中发展的相干态正交化方法，进行半解析的非微扰计算。同时开展数值模拟。希望一方面从理论和实验同时研究探索自由电子激光的统计性质；另一方面从根本上探讨量子光学和统计光学在高阶相干性方面的分歧。本项目是基于本实验室在建的冷原子阱而申请的，所以有实验基础。

本项目围绕量子自由电子激光及基于冷原子的相干电子源，研究了包括电子光子相互作用、相干衍射成像算法、相干纳秒脉冲产生及腔增强方法、高功率窄线宽激光器中的热效应等问题。研究了多电子与单模光场相互作用在量子区域的集体行为，其中光子数统计满足泊松或超泊松分布；获得了更窄的电子束动量分布可使量子自由电子激光活的更好的增益；研究了电子束与周期性光场相互作用，找到了电子束横向发射度对KD效应衍射结果的影响；提出了基于KK效应的CDI成像KK-OSS算法；开发了基于多重网格重建的CDI算法，减小了孪生像问题的发生概率；提出了复调制产生纳秒级相干方波脉冲的方法，并探索了该类相干脉冲在高精细度谐振腔内放大的可行性；研究了窄线宽高功率NPRO激光器中的热透镜效应，首次获得了该类激光器的OPD分析结果。同时在实验上初步完成了冷原子相干电子源。.上述研究结果，将对量子自由电子激光及相干电子源的研发提供有力的理论和实验条件支撑。