基于光克尔效应的径向匀滑方案参数优化

在基于光克尔效应的径向匀滑方案中，抽运光脉冲序列利用非线性介质的光克尔效应对激光束附加周期性的球面位相调制，从而使激光束远场焦斑内部散斑产生周期性的径向扫动，以改善远场焦斑均匀性。为了分析抽运光时间特性的改变对匀滑效果的影响，建立了径向匀滑方案的理论模型，并利用该模型对抽运光的时间特性参数进行了分析及优化。结果表明，在抽运光子脉冲之间的延迟时间一定时，子脉冲的脉宽过大或过小均会降低激光束远场的辐照均匀性，而随着子脉冲脉宽的增大，激光束远场的辐照均匀性随积分时间的波动相对趋于稳定，因而在避免产生明显“拍频”现象的前提下，选取较大的抽运光子脉冲脉宽更有利于实现稳定的匀滑效果。激光束与抽运光的时间同步精度对初期的匀滑效果有较大的影响，当抽运光提前1/5个周期左右时，可以在更短的积分时间内达到较好的径向匀滑效果。此外，不同的抽运光时间波形所获得的匀滑效果也有所不同，当抽运光的时间波形为三角波时，焦斑内部散斑的径向扫动速度较为稳定，可以使径向匀滑的整体效果及稳定性得到有效改善。

Abstract

In the scheme of radial smoothing based on the optical Kerr effect, pump laser pulse train uses optical Kerr effect of nonlinearity medium to add periodical spherical phase modulation, which makes the speckle inside the focal spot of the laser beam in far field sweep periodically at radial direction, and the uniformity of the focal spot in far field is improved. To analyze the influence of temporal characteristics change of the pump laser on beam smoothing effect, a theoretical model of the radial smoothing scheme has been established, and the time characteristic parameters of the pump laser has been analyzed and optimized. The results indicate that, for the given delay time between pump photon pulses, the sub-pulse with either too large or too small pulse width will reduce the irradiation uniformity of laser beam in far field. Meanwhile, with the increase of the pulse width of sub-pulse, the volatility of irradiation uniformity of laser beam in far field with integral time is trending toward stability relatively. Thus, the relatively large pulse width of the pump laser would be beneficial to obtain a more stable smoothing effect under the condition that the obvious beat wave effect should be avoided as far as possible. The time synchronous precision between the laser beam and the pump laser has a significant influence on the initial beam smoothing effect. For the pump laser of about one fifth period of the pulse train in advance, a better smoothing effect can be obtained in a relatively shorter integral time. In addition, for different temporal shapes of the pump laser, different smoothing effects can be achieved. When the temporal shape of the pump laser is triangular, the radial direction sweeping speed of the speckle inside the focal spot is relatively stable, and the radial smoothing effect and its stability can be improved effectively.

参考文献

[1] Lindl J D, Amendt P, Berger R L, et al. The physics basis for ignition using indirect-drive targets on the National Ignition Facility[J]. Physics of Plasmas, 2004, 11(2): 339-491.

[2] 温圣林, 颜浩, 张远航, 等. 波前畸变下连续相位板焦斑的计算与实验[J]. 光学学报, 2014, 34(3): 0314001.

Wen Shenglin, Yan Hao, Zhang Yuanhang, et al. Calculation and experiment of the focal spot caused by continuous phase plate with incident wavefront distortion[J]. Acta Optica Sinica, 2014, 34(3): 0314001.

[3] 江秀娟, 周申蕾, 林尊琪. 利用二维光谱色散和透镜列阵改善靶面辐照均匀性[J]. 中国激光, 2007, 34(11): 1533-1537.

Jiang Xiujuan, Zhou Shenlei, Lin Zunqi. Improved target irradiation uniformity using two-dimensional Spectral Dispersion and Lens Array[J]. Chinese J Lasers, 2007, 34(11): 1533-1537.

[4] 李平, 王伟, 赵润昌, 等. 基于焦斑空间频率全域优化的偏振匀滑设计[J]. 物理学报, 2014, 63(21): 215202.

Li Ping, Wang Wei, Zhao Runchang, et al. Polarization smoothing design for improving the whole spatial frequency at focal spot[J]. Acta Physica Sinica, 2014, 63(21): 215202.

[5] Lehmberg R H, Schmitt A J, Bodner S E. Theory of induced spatial incoherence[J]. Journal of Applied Physics, 1987, 62(7): 2680-2701.

[6] Kline J L, Glenzer S H, Olson R E, et al. Observation of high soft X-ray drive in large-scale Hohlraums at the National Ignition Facility[J]. Physical Review Letters, 2011, 106(8): 085003.

[7] Miyaji G, Miyanaga N, Urushihara S, et al. Three-directional spectral dispersion for smoothing of a laser irradiance profile[J]. Optics Letters, 2002, 27(9): 725-727.

[8] Zhong Z Q, Hou P C, Zhang B. Radial smoothing for improving laser-beam irradiance uniformity[J]. Optics Letters, 2015, 40(24): 5850-5853.

[9] 钟哲强, 侯鹏程, 张彬. 基于光克尔效应的径向光束匀滑新方案[J]. 物理学报, 2016, 65(9): 094207.

Zhong Zheqiang, Hou Pengcheng, Zhang Bin. A novel radial beam smoothing scheme based on optical Kerr effect[J]. Acta Physica Sinica, 2016, 65(9): 094207.

[10] Haynam C A, Wegner P J, Auerbach J M, et al. National Ignition Facility laser performance status[J]. Applied Optics, 2007, 46(16): 3276-3303.

[11] 曾曙光, 胡静, 王飞, 等. 基于波分复用思想的啁啾脉冲堆积方法[J]. 光学学报, 2013, 33(5): 0514001.

Zeng Shuguang, Hu Jing, Wang Fei, et al. Pulse stacking scheme based on wavelength division multiplexing[J]. Acta Optica Sinica, 2013, 33(5): 0514001.

[12] Bel′kov S A, Voronich I N, Garanin S G, et al. Study of the apodization of a laser beam by serrated aperture stops for high-power installations of laser thermonuclear synthesis[J]. Journal of Optical Technology C, 2015, 82(6): 330-338.

[13] Bowers M, Burkhart S, Cohen S, et al. The injection laser system on the National Ignition Facility[C]. SPIE, 2007, 6451: 64511M.

[14] 张锐. 高功率激光装置靶面光强分布精密控制技术研究[D]. 合肥: 中国科学技术大学, 2013.

Zhang Rui. Research on precise control technologies of intensity distribution on target of high power laser facilities[D]. Hefei: University of Science and Technology of China, 2013.

[15] Qiao B, Dai S, Xu Y, et al. Third-order optical nonlinearities of chalcogenide glasses within Ge-Sn-Se ternary system at a mid-infrared window[J]. Optical Materials Express, 2015, 5(10): 2359-2365.

[16] Qiao B, Chen F, Huang Y, et al. Investigation of mid-infrared optical nonlinearity of Ge20SnxSe80-x ternary chalcogenide glasses[J]. Materials Letters, 2016, 162: 17-19.

[17] Jiang Y, Zhou S, Wu R, et al. Experimental investigation on beam smoothing by combined spectral dispersion and lens array technology[J]. Chinese Optics Letters, 2013, 11(8): 081404.

李腾飞, 侯鹏程, 张彬. 基于光克尔效应的径向匀滑方案参数优化[J]. 光学学报, 2016, 36(11): 1114002. Li Tengfei, Hou Pengcheng, Zhang Bin. Parameters Optimization for Radial Smoothing Based on Optical Kerr Effect[J]. Acta Optica Sinica, 2016, 36(11): 1114002.

基于光克尔效应的径向匀滑方案参数优化

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