提出一种基于全光纤光谱干涉的多路超短脉冲大动态范围时间同步单次测量方法,弥补了非线性相关法测量同步状态时测量范围小和示波器测量时分辨率差的不足,解决了同步测量中空间光路的复杂性和单次实时测量的难题。首先对多路光纤阵列干涉测量进行仿真计算,然后设计四路脉冲传输的光路并在实验中验证多路同步单次测量方法的可行性,最后详细分析测量误差的来源和影响。该测量方法的最小同步时间精度为5.3 fs,测量范围为1.055~14.751 ps,与仿真结果有较好的一致性。该测量方法具有光纤链路易于集成、光谱干涉数据处理速度快、测量信号能量需求低等优势,在多路超短脉冲激光相干合束系统中有重要应用前景。

基于单光子雪崩二极管(SPAD)阵列探测器的三维成像技术在工业和科学领域具有重要的应用前景。然而现有的SPAD阵列器件仍存在小阵列规模和低像素填充率所导致的低空间分辨率问题,为此基于SPAD阵列(32 pixel×32 pixel)和衍射光学元件(DOE)搭建收发共光路扫描三维成像实验系统。利用DOE将出射激光整形为激光点阵并与接收视场匹配可以提升激光能量利用效率,通过共光路扫描可以实现高分辨三维成像。利用基于滑动时间窗的噪声光子滤除算法和基于全变分正则化的图像重构算法对回波光子数据进行处理。实验结果表明,图像重构算法可以获取10 m外目标64 pixel×64 pixel的三维图像,且在平均每像素0.86个信号光子的条件下实现清晰成像,成像结果的平均绝对误差为0.016 m。

由于超短超强激光装置中光谱带宽较宽,使用传统的空间滤波器透镜组扩束会导致装置色差的积累,严重影响终端焦斑的质量。介绍了国内外用于超短超强激光装置中消除色差影响的主要技术与研究进展,对比总结了几种主要方案的优缺点,并提出了一种可动态精确补偿装置色差的方案,经实验验证已应用于实际工程中。最后对色差补偿的发展方向进行了分析与展望。

等离子体镜是一种有效提升高功率超短脉冲激光信噪比的方法,但在一部分实验中使用等离子体镜后焦斑出现了退化现象。为了定量研究等离子体镜的焦斑退化问题,提出基于等离子体膨胀和衍射传输的时空聚焦多步传输算法,通过光束质量评价函数定量分析等离子体膨胀时间、波前误差幅值和空间频率对焦斑退化的影响。仿真结果表明,等离子体镜引起的远场焦斑退化主要是由等离子体膨胀时间和波前误差引起的等离子体膨胀不均匀所致,其中,等离子体膨胀时间是主导因素。并且波前误差的幅度越大、空间频率越低,对聚焦能力的影响相对越大。从高信噪比、高功率激光系统输出能力的角度考虑,对于使用等离子体镜的高功率超短脉冲激光系统提出时空上的光束质量要求,以避免远场焦斑的退化问题。

高功率超短脉冲激光系统中,空间滤波器透射元件引入的色差会影响系统的聚焦功率密度。针对这一问题,提出一种具备动态调节能力的色差预补偿方案。该方案由正负透镜和反射系统构成共焦像传递系统,能够实现全系统色差的动态精确补偿。基于该方案为神光-II 5 PW(SG-II 5 PW)激光系统设计并搭建了色差预补偿光路。实验结果表明,通过精密调节该单元内部透镜间距能够精确补偿全系统的色差,显著提升系统峰值功率密度。经过色差补偿后,在SG-II 5 PW系统开展质子加速实验,获得了超过16 MeV的质子产额。

The stretcher system is an important part in the high-engery petawatt laser facility. The stretcher system design has a direct impact on the quality of the output pulses. The stretcher systems in some famous high-energy petawatt laser facility are summarized. And the structure and parameters are compared and discussed.

The impact of the stretcher on the contrast ratio of the out pulse is analyzed making use of the ray -tracing method , which is based on the contrast ratio model of chirped pulse.When the beam size in the stretcher is increased from 2 mm to 40 mm ,the contrast of the output pulse approximately increase two magnitude. When the input pulse is Sech2 ,the contrast of the output pulse is better than what the input pulse is Gassian or Rectangular.

In the design of the Offner stretcher, it is very important to investigate the mirror curvature radius errors, which has a direct impact on the quality of the output pulse. So it is necessary to analyse the effect on the output pulse contrast due to the mirror curvature radius manufacture errors in the ffner stretcher. A ray-tracing model for ffner stretcher with these errors is established. Based on the model, effects on output pulse contrast through the stretcher is analyzed.When the mirror curvature radius error is between 0.2%～0.5%, it can fully meet the requirements for the SHENGUANG Ⅱ petawatt laser facility. Also, when there is error for the mirror curvature radius, keeping the distance between concave mirror and convex mirror half of curvature radius of the concave mirror is better than keeping the two curve mirrors in the same center.

In a stretcher,it is important of spectral clipping. It has a direct impact on the quality of the output pulse. Base on the ray-tracing,an analytical spectral clipping model is present in the ffner stretcher . When the stretcher parameters is determined, the location of the grating placed has a very important influence on the pulse spectral clipping. When the grating placed on the symmetric center about optical axis, the spectral distribution through stretcher will be asymmetric about center wavelength of the laser, that is to say,the spectral clipping will be asymmetric spectral clipping.Therefore,the output pulse contrast will be droped approximately one magnitude in the SGII ninth beam petawatt upgrade laser facility. In order to keeping the spectral symmetry distribution about center wavelength of the laser through the stretcher, the grating must be placed on the asymmetrical position about optical axis.