【作者】 李廷红；

【导师】 张彬；

【作者基本信息】 四川大学 ， 光学， 2004， 硕士

【摘要】 为了顺利实现惯性约束聚变(ICF)点火，强激光的能量和光束质量是非常重要的因素。然而，强激光在空气长程传输过程中产生的受激旋转拉曼散射(SRRS)效应会对激光能量和光束质量产生影响。当超过SRRS效应阈值时，强激光通过空气长程传输时，不但其光束质量有可能变差，而且还会损失一部分能量。因此，本论文针对强激光在空气长程传输过程中产生的SRRS效应，详细讨论了多种因素对SRRS阈值和光束质量的影响。全文取得的主要结果如下： (1) 建立了强激光在空气长程传输产生SRRS效应的物理模型 建立了SRRS效应的物理模型，详细考虑了Stokes光和泵浦光的衍射、Langevin(郎兹万)噪声源、激光脉冲波形、介质的非线性极化、泵浦光的衰减、斯托克斯光的非线性放大以及拉曼线宽等诸多因素。 (2) 编写了SRRS效应计算模拟程序，并进行了校核 编写了SRRS计算程序，利用美国罗切斯特大学针对Omega激光装置的计算模拟和实验数据作了校核，证明了本文所编程序及计算方法的正确性和可靠性。 (3) 对SRRS效应特性进行了研究 详细讨论了影响入射泵浦光的强度、脉宽、时间位相调制和衍射等影响摘要SRRS闻值的因素，计算分析了这些因素对达到产生斯托克斯光闭值时的传输距离以及斯托克斯光转换效率的影响。在此基础上，提出了一些抑制SRRS效应的方法，以减小SRRS效应对强激光长程传输的影响。 (4)研究了影响光束质量的因素 详细讨论了SRRS效应、衍射、热斑等因素对长程传输过程中激光光束质量的影响，并进一步提出了一些改善光束质量的方法。关键词:受激旋转拉曼散射(S RRS)、光束质量、闲值、转换效率更多还原

【Abstract】 In the inertial confinement fusion (ICF), to achieve optimum fuel compression, the laser beams must irradiate the target uniformly, requiring excellent beam quality. But the effect of stimulated rotational Raman scattering (SRRS) will influence the power of laser and beam quality. At the case of excess of stimulated rotational Raman scattering threshold, not only the beam quality of the wave front will be degraded, but also the energy will be lost in process of high-power laser propagation in long air path. In this thesis, the factors that influence the threshold of SRRS effect and the laser beam quality have discussed in detail. The main results obtained here can be summarized as follows:(1) The physical model of SRRS in long air path has been built up.The physics model of SRRS have been built up, which considered the diffraction effects of stokes and pump lasers, Langevin noise sources, pulsed-shaped laser beams, the nonlinear polarization of the medium, the depletion of pumped laser, the nonlinear amplifier of the Stokes field, and the Raman bandwidth etc.(2) The simulation code of SRRS effect in long air path has been built up and verified.The simulation code of SRRS effect in long air path has been built up andverified in the use of the experimental and modeled data for Omega presented by Rochester University, showing the validity of our code and the simulation method.(3) The characteristics of SRRS effect in long air path have been studied.The factors that influence threshold of SRRS effect, such as the intensity of pump laser, pulse width, phase modulations in the time and the diffraction effect have been discussed in detailed. The effect of the factors including the intensity of pump laser, pulse width, phase modulations in the time and the diffraction effect on the propagation distance corresponding to the stokes threshold and conversion efficiency of stokes beam have been analyzed and discussed. In order to decrease the effect of SRRS effect on high-power laser in long air path, the methods that can restrain the SRRS effect have been proposed (4) The factors that influence the beam quality have been studied.The factors including SRRS effect, diffraction effect, hot spots, and so on that influence beam quality have been discussed in detailed. The methods that can improve the beam quality have been proposed.更多还原