强激光非线性热像与克尔介质厚度的关系

通过理论分析与数值模拟方法,研究了高功率激光系统中非线性热像位置及光强随介质厚度的变化规律。基于角谱传输和Bespalov-Talanov小尺度自聚焦理论,在不作薄介质近似情况下得到了热像光强表达式,并用数值模拟结果进行了验证。结果表明,在一定的入射功率下,热像光强随介质厚度的增加而增大;而在一定的B积分下,热像光强随介质厚度的增加先单调增加,达到一极大值后,单调减小。此外,当模糊斑相对于克尔介质的距离的菲涅耳数远大于1时,可采用薄介质近似。数值模拟结果与解析结果吻合得很好。

Dependence of Nonlinear Hot Image of Intense Laser Beam on the Thickness of Kerr Medium

Dependence of the position and light intensity of nonlinear hot image in high power laser system on the thickness of Kerr medium has been investigated theoretically and numerically.Based on the propagation of angular spectrum and Bespalov-Talanov small-scale self-focusing theory,the expression for hot image intensity is obtained without thin medium approximation,and verified by numerical simulation.It is shown that,for a given obscuration, the hot image intensity increases monotonously with the medium thickness for a given input laser power,while it firstly increases to reach a maximum value,then decreases as the medium thickness increases for a given B integral. In addition,it is shown that the thin medium approximation is applicable to hot image analysis when the Fresnel number of an obscuration with respect to the length of the Kerr medium is much more than 1.The analytic results are in good agreement with numerical simulations.