甚多束高功率激光精密聚焦调控技术

As a new fusion ignition program, the Fast Ignition is expected to play an important role in the inertial confusion projects. In practical application, 50% energy of the combined 8-beam far field focal spot is required to be concentrated in less than 40 micrometers, and the physical boundary conditions are demanding. Especially since 2012, more physical extreme demands are reported by American. This requires not only the strict control of wavefront of each beam, but also the precise control of the phase differences between beams at the same time..Around such international frontier research field on precise control of the phase error between high power laser beams, the interference method is proposed in this item to measure the phase error between beams, and exploring development on adaptive phase compensation evaluation criteria between beams as well as the feedback controlling algorithm are also proposed, based on the characteristics of the dynamic distortion of high power laser near field wavefront. What's more, demonstration system of closed-loop feedback experiments and precisely focusing controlling technology is wished to be developed to realize the influence analysis of far field focal spot because of the phase differences among various beams in the same bunch. This study is expected to provide key technologies routes and core algorithms for the precise focus and flexible regulation of the multi-beam high power laser facilities.

快点火作为一种新的聚变点火方式，有望在激光惯性约束聚变工程中得到重要应用。实际应用中要求八束激光合成的远场焦斑50%的能量集中于40微米内，物理边界条件要求苛刻。特别是2012年度以来，美国国家点火工程试验不断报道出更高的物理极限需求，这就需要对每一束激光自身的波前进行严格控制的同时，还要对光束之间的位相差进行精确控制。.围绕高功率激光束间相位误差精密调控这一国际前沿研究方向，本课题提出了短脉冲束间相位误差四通道移相实时干涉测量方法；基于高功率激光近场波前的动态畸变特征，探索性发展束间自适应相位补偿评估标准与反馈控制算法；针对同一束组内不同光束间相位差对远场焦斑的影响分析，发展精密聚焦调控技术与闭环反馈实验演示系统。该研究有望为甚多束高功率激光精确聚焦及其灵活调控提供关键技术路线与核心算法。

本研究项目主要围绕高功率激光系统中，光束间相位误差精密调控这一国际前沿研究方向，重点开展了束间相位误差四通道移相实时干涉测量方法、探索性发展束间自适应相位补偿评估标准与反馈控制算法、发展精密聚焦调控技术与闭环反馈实验演示系统等方面的研究，目标是为甚多束高功率激光精确聚焦及其灵活调控提供关键技术路线与核心算法。. 在项目执行周期内，主要完成的研究内容和成果为：. 1、细化并完善了高功率激光系统中波前传输的分析体系，针对影响高能激光实际焦斑形态的波前位相空间分布尺寸特征有，提出了波前畸变梯度GRMS作为评价高功率激光远场聚集性能的重要指标，为大口径高能激光束的远场控制和评价提供了重要理论依据。. 2、建立了高功率激光放大与传输三维分析模型，形成了空间周期性调整波前在增益介质和传输介质中的非线性传输过程的数值仿真能力，强化了相位调制在高功率激光波前放大传输过程中的重要性，为高功率激光光束间相位误差的综合评估与反馈控制算法建立了重要的理论依据。同时，结合神光大型高功率激光系统的实际输出性能参数，实现了关键参数的精确反演实验验证。. 3、基于短脉冲时空特性，利用铌酸锂晶体的双折射相位调制和偏振器件分光特性，设计并实现了三维空间集成式四通道移相实时干涉测量方案，完成了两通道干涉测量实验验证，为大口径束间波前相位误差测量提供了有效的技术途径。. 4、以核心高效频率转换DKDP晶体为研究对象，从折射率微观参数入手，研究了含氘量对频率转换过程中温度和匹配角等宏观量的影响关系，形成了三倍频远场焦斑时空物理特性的精确评估与分析，建立了三倍频传输过程中波前控制策略，为高功率激光单束和甚多束光束波前畸变控制提供了重要理论依据。. 上述研究内容形成两通道波前干涉测量实验验证平台一套，高功率激光波前传输与反馈控制计算仿真软件一套，完成了高功率激光参数在线反演实验验证。共发表期刊与会议论文7篇，申请发明专利4项，完成论著2项，培养研究生5名。