高功率高重频皮秒激光器及在周期量级高能太赫兹产生中的应用

Table-top Free-Electron-Laser (FEL) is highly demanded due to the massive needs of 4D electron microscopy with <1nm-level spatial resolution and as-level time resolution. FEL driven by THz wave rather than RF wave is considered to be one of the most promising techniques to achieve it. Yet generation of the few-cycle high power THz by nonlinear conversion is constrained by the current available picosecond laser. Based on previous research, different from the reported Innoslab mechanism with chirped pulse amplification technique, a mechanism of parasitic lasing suppressed Nd:YVO4 Innoslab is proposed in this project to achieve high power high repetition rate output. And this laser will be used to study the process of the few-cycle, high flux THz generation. By 3D finite element thermal analysis, the average power will be upgraded. Through parasitic lasing suppressing technique, the energy storage will be enormously enhanced. Adopting the cavity damping technique, the energy extraction ability of the seeding will be significantly improved. The output pulse energy would be 3 orders higher than that of the current typical Innoslab laser source. This high power and high repetition rate character would be greatly helpful for the few-cycle, high flux THz generation. Research fields of table-top FEL, ultrafast THz microscopy, and THz nonlinear optics will be significantly benefited from this research project.

对物质结构在<1nm空间分辨率和阿秒量级时间分辨率上进行观测的巨大需求，使人们迫切期待小型化自由电子激光器的诞生。太赫兹替代RF波进行电子加速是最有望实现台式化自由电子激光器的途径之一。非线性变换产生周期量级高能太赫兹的发展，受到了现有皮秒激光水平的严重制约。本项目在以往工作基础上，区别于文献报道的结合啁啾脉冲放大技术的Innoslab，提出一种基于寄生振荡抑制的Nd:YVO4 Innoslab方法，以获得高功率高重频皮秒激光，且用其于周期量级高能太赫兹产生的探索研究。利用3D有限元热分析，对功率进行升级；利用对寄生振荡的抑制，大幅提升储能总量；利用腔倒空技术改善种子光，提高其能量抽取能力，输出脉冲能量有望比现有常规Innoslab高三个量级，其高功率高重频的特性将大大帮助周期量级高能太赫兹的产生。该项目研究对台式化自由电子激光器、超快太赫兹成像、太赫兹非线性光学等领域的发展有重要意义。

高重复频率，高功率，高光束质量皮秒激光器在科研，生物医学，工业微纳加工等诸多领域有着重要的应用和需求。特别是近几年来，利用高功率皮秒激光器作为驱动源产生太赫兹波被认为是最有潜力和最先进的方法之一。本项目在本研究小组的基础上对皮秒激光器系统性能的提升做了大量的工作。创新性地提出了分立路径的Innoslab激光放大器，彻底消除了该类激光器的寄生振荡现象，突破了该类激光器的主要瓶颈；结合σ线偏振带内泵浦泵浦技术和正交热补偿技术，实现了高功率，衍射极限级光束质量的高功率皮秒种子源；同时也对新型激光材料进行了积极的探索，从材料性能上探索未来高能量皮秒激光可行性。本项目的工作为皮秒激光的未来应用和太赫兹非线性转化奠定了良好的基础。