局域格位调控对YCOB晶体解理开裂和光参量过程的影响机制研究

Optical parametric chirped pulse amplification (OPCPA) is one of the main ways to achieve ultra-high peak power laser pulse amplification, since it has a broad gain bandwidth, high single-pass gain, good beam quality and so on. OPCPA can further increase the peak power of the laser pulse by cascading and/or combining. However, the lack of large aperture NLO-crystals limits the peak power of OPCPA. YCOB possesses good NLO properties, however, the usable aperture is less than 70mm due to cleavage cracking. A new idea of overcome cracking by doping is proposed in this project. Specifically, the local microstructure is regulated by doping to increase the bond strength between the cleavage planes, without changing the main functional groups of the crystal structure. The effects of doping on the binding energy of cleavage plane is calculated by using the first principle theory. Then, the results are verified by crystal growth and properties characterization. Finally, the effects of doping on OPCPA process is studied by using the Xingguang-III facility. The implementation of this project will reveal the mechanism of localized doping on cleavage cracking and optical parametric amplification of YCOB crystal. It is expected to provide a way to improve the usable aperture and properties of YCOB, as well as enrich the understanding of the YCOB doping crystallization chemistry, which may shed light on solving cracking of other crystal, and will provide materials support for the development of ultra-high peak power laser amplification technology in our country.

光参量啁啾脉冲放大（OPCPA）具有增益高、带宽大和光束质量好的优点，且通过级联、合束能进一步提升峰值功率，是实现超高峰值功率激光放大的主要途径。然而缺乏大口径非线性光学晶体限制了OPCPA的输出功率。硼酸氧钙钇（YCOB）是一种性能优异的非线性光学晶体，由于解理开裂，其使用口径小于70mm。通过调节生长工艺来降低晶体内应力的传统方法不仅耗时费力，且对大尺寸晶体没有效果。本研究拟通过局域格位掺杂增强解理面间结合力的新思路来抑制解理开裂。运用第一性原理计算格位调控对晶面结合能的影响，通过制备晶体及表征性能来验证计算结果，最后在星光III装置完成验证实验。通过以上步骤迭代，最终揭示局域格位调控对YCOB晶体解理开裂和光参量过程的影响机理，为提升晶体口径和性能提供理论依据，充实YCOB晶体掺杂结晶化学的基础理论，为其它晶体研究提供借鉴，为我国超高峰值激光放大技术的发展奠定材料基础。

本项目针对高能激光装置亟需的硼酸氧钙钇非线性光学晶体，利用第一性原理计算实验与晶体生长实验相结合的技术手段，紧紧围绕YCOB晶体掺杂的实现以及掺杂对YCOB晶体性能影响这两个基本问题。先开展第一性原理计算进行掺杂组分筛选，然后采用提拉法和下降法进行掺杂晶体生长与性能表征，最后总结局域格位调控对YCOB晶体性能及解理开裂的影响规律。结果表明稀土离子掺杂能够在一定程度上增强YCOB晶体解理面的结合力，提高解理面的断裂强度，起到抑制YCOB晶体解理开裂的作用，将为解决大口径YCOB晶体的解理开裂问题提供一条新途径。发表高质量SCI学术论文9篇（其中1篇在线发表），培养研究生4名，其中两名已经毕业，并在合作单位和相关单位实现YCOB晶体的应用验证，达到项目预期目标。

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