中心波长及脉宽对能量叠加光束远场的影响

Effects of center wavelength and pulse width on superposed energy beams in far field

多束激光的远场叠加对于提高远场靶面能量是一种有效的方法,单元光束的参数的变化对于远场合成光束都会产生影响。为了分析脉冲激光参数控制对远场能量分布的影响,利用夫琅禾费衍射积分公式导出了4束普通脉冲高斯光束合成的远场光强的解析式,并整理了激光中心波长和脉宽的改变对远场叠加后能量分布的影响之间的具体关系。通过MATLAB的数值模拟,结果表明:当光束的中心波长减小或者脉冲宽度减小时,远场能量向中心轴上汇聚,远场轴上光强增加。当轴上光强相对于理想中心波长和脉宽的远场轴上光强的变化率小于5%,中心波长变化率最大不能超过7.89%,或者脉宽变化率最大不能超过91%,因此,中心波长的变化对于远场光强分布的影响比脉宽更大。

Laser beam far-field superposition is an effective method for improving the far-field target surface energy. Changes of the parameters for unit beam will influence the far-field combined beam. In order to analyze the impact of pulsed laser parameter＇s control on the far-field energy distribution, the Fraunhofer diffraction integral formula was used and the analytic formula of far field intensity for four beams of ordinary pulsed Gauss beam synthesis was deduced and the specific relationship about laser center wavelength and pulse width change with the far-field stack power were proposed. Through the numerical simulation of MATLAB, the results show, when the center wavelength of beam decreases or pulse width decreases, the far field energy converges to the center axis and the far-field on axis intensity will increase. When the on axis intensity relative to the ideal center wavelength and pulse width in the far field intensity on axis changes rate is less than 5%, the center wavelength maximum rate of change should not exceed 7.89%, or pulse width maximum rate of change should not exceed 91%. Therefore, the center wavelength will have a greater impact on far-field intensity distribution compared with pulse width.