【作者】 刘兰琴；

【导师】 彭翰生；

【作者基本信息】 中国工程物理研究院 ， 光学工程， 2005， 博士

【摘要】 高功率超短脉冲激光技术自二十世纪八十年代中期以来得到了飞速地发展,世界科技大国已相继建立了数台大型的高功率超短脉冲钛宝石激光装置,提高靶面峰值功率密度始终是追求的目标之一。本论文依托于中国工程物理研究院激光聚变研究中心研制的SILEX-Ⅰ超强超短脉冲钛宝石激光装置,为解决影响靶面功率密度的两大主要因素:压缩脉冲质量和聚焦光束质量,而展开研究工作的。 论文采用数值模拟为主要技术手段,结合实验研究,探讨光谱增益窄化补偿以及色散控制方面的若干问题,同时对高功率超短脉冲的远场描述方法以及大口径离轴抛物镜聚焦的时空耦合特性进行了研究。论文主要工作包括以下几个部分: 1、阐述了超强超短脉冲的需求背景以及发展现状,分析了超强超短脉冲激光光束控制中的科学技术问题,如光束空间质量控制、光束时间质量控制、光谱增益窄化补偿以及色散控制等问题,同时对相应的控制方法进行了较为详细的调研分析。 2、概括性地介绍了中国工程物理研究院激光聚变研究中心研制的SILEX-Ⅰ超强超短脉冲钛宝石激光装置,并对其中涉及的一些科学问题和关键技术,如增益窄化、光束脉冲质量、光束空间质量、啁啾脉冲的传输放大技术、大口径晶体横向ASE、光栅压缩的时空耦合、超短脉冲聚焦等进行了分析和讨论。 3、研究分析了可编程声光色散滤波器在SILEX-Ⅰ超强超短脉冲激光装置中实现光谱整形与控制的成功应用,对其工作原理、光谱补偿调制函数的设计以及实验结果进行了阐述和讨论。设计了一种与高功率超短脉冲激光放大过程中获得的总增益、增益介质的带宽、激光带宽、脉冲中心波长等参数相关的光谱调制函数,通过将放大前的注入脉冲进行调制,可以很好地补偿放大过程中的增益窄化。并利用声光光谱可编程色散滤波器,实现了对脉冲光谱振幅和位相的主动控制,削弱了增益窄化效应对光谱的影响,并最终获得更窄的变换极限的压缩脉宽。 4、较为系统地、详细地对展宽压缩系统的各阶色散特性进行了理论研究。在啁啾脉冲放大激光系统中,展宽器和压缩器是非常关键的单元技术,其色散的大小和匹配程度最终将决定整个系统压缩脉冲的脉宽和信噪比。通过对前人工作的不足之处进行分析和改进,重新推导了更为完善的各阶色散解析式。通过解析方法和光线追迹的方法,以实现高功率超短脉冲激光系统的优化设计为目的,更加系统、完善地对两类比较常用的展宽压缩系统的各阶色散进行了理论研究与分析,得到了一些可供参考的有价值的结论。 5.研究分析了初始啁啾以及展宽器高阶色散对展宽脉冲的影响,并指出了展宽器压缩器在二阶色散完全补偿的情况下,要补偿高阶色散二者入射角之间需要满足的关系。研究分析了啁啾脉冲放大系统中展宽压缩系统在不同条件、不同匹配方式下的更多还原

【Abstract】 Over the past ten years, high-power ultra-short pulse Ti: sapphire laser technologies based on chirped pulse amplification(CPA) have been rapidly developed and a number of large facilities have been built, increasing peak power density is always pursued aim for scientists. This dissertation was based on the SILEX-I (Super Intense Laser for Experiment on the Extremes) ultra-intense ultra-short pulse Ti:sapphire laser built at Research Center of Laser Fusion, CAEP. Two major factors affecting peak power density, compressed pulse quality and focused spot quality, were studied, respectively.Using numerical simulation and experimental methods, spectral properties such as spectral gain narrowing and dispersive control were mostly studied. The far-field description methods of high power ultra-short pulse lasers and the spatio-temporal characteristic of lager-aperture off-axis parabolic focusing systems were also studied. The main research topics included:1. The development, application and general status of ultra-high ultra-short pulse laser systems were summarized in this thesis, the key scientific and technological points in beam control of ultra-short pulse lasers, such as spatial quality, temporal quality, spectral gain narrowing compensation and dispersive control, et al. were analyzed, and the corresponding beam control techniques were elaborated.2. The SILEX-I ultra-intense ultra-short pulse Ti:sapphire laser was briefly depicted. Besides, the key techniques in this facility, such as gain narrowing, spatial quality, temporal quality, propagation of chirped pulse, ASE in lager-aperture crystal, spatio-temporal characteristics in grating compression and the focus of ultra-short pulse were analyzed and discussed.3. Theoretical analysis and experimental study of active spectrum control were completed. The gain of the regeneration amplifier in CPA system is higher than 106, gain-narrowing effects are generally produced when laser propagates through the gain medium in the regeneration amplifier, leading to a broadened pulse duration after compressed. With the active spectrum control, the compressed pulse of near the transform limit can be obtained. Among the controlling ways, acoustic-optic programming dispersive filter(AOPDF) can be used to fulfill the gain spectral amplitude and phase shaping, and decrease the gain-narrowing effects.4. Dispersive characteristics of stretcher and compressor were studied more systematically and detailedly. In a chirped pulse amplification system, the stretcher and thecompressor are the key components, the dispersive of the stretcher and the compressor and the matching degree of dispersive will determinate the pulse width and the signal-to-noise ratio of the pulse after compressed. Based on the research of some scientists, dispersive formulas were deduced renewedly and detailedly, and by ray tracing methods, validity of the formula was testified. Using ray tracing method and formula method, the stretcher models with a folded telescope and Offner triplet were studied in detail to optimize the high power ultra-short pulse laser system.5. The influence of initial chirp and high order dispersive on the stretched pulses were analyzed. It indicated that the incident angle of compressor must be larger than the incident angle of the stretcher to compensate high-order dispersive in CPA systems. The influence of residual dispersive on compressed pulse under different conditions and different matching modes were studied in detail. Optimum methods and dispersive compensation techniques were studied too, it showed that mixed dispersive compensation methods could get Fourier transform limited pulses. Finally, experiments about pulse compressions in SILEX-I laser were carried out. To ensure a good alignment of the compressor gratings a diagnostic device was suggested with simultaneous monitoring both temporal and spatial behaviors.6. Using statistical method and numerical simulation, the far-field description methods of high power ultra-short pulse lasers were established. The research results point out that FWHM of focus cannot be simply used to give the peak power density. Strehl ratio or the encircled energy within FWHM are more appropriate.7. The spatio-temporal characteristics of lager aperture OAP focus in high-power ultra-short pulse laser system were studied carefully. From simulations, It concluded that OAPs not only determine the focal spot as a focal element, but also affect the temporal property. Mislignments of OAP could lead to elongated pulse durations, and thus decrease the power density.更多还原