高功率超短脉冲激光的远场描述方法

Far-field description methods for high power ultra-short pulse laser

以随机统计和数值模拟为研究手段,对高功率超短脉冲激光的远场描述方法进行了分析研究。结果表明:对理想超高斯光束,半高全宽内包含的能量百分数最大不超过70%,且随着阶数增大而逐渐降低。在光束质量较好时,远场焦斑的半高全宽基本保持不变。由焦斑的半高全宽计算得到的聚焦功率密度,与半高全宽之间没有明确的关系,但与Strehl比以及半高全宽内包含的能量之间具有明确的线性增长关系。对追求高的功率密度的激光脉冲,单纯用半高全宽或者几倍的衍射极限来描述远场是远远不够的,用Strehl比或者半高全宽内包含的能量百分数来表征功率密度更为恰当。

Using statistical methods and numerical simulation, the far-field description methods for high power ultra-short pulse laser were established. The results show that the percentage of energy in FWHM of the ideal super-Gaussion beam is no more than 70℃, and it reduces with the order of the super-Gaussian beam increasing. The FWHM of focus will keep a constant when beam quality was good, and the power density in FWHM has no relationship with FWHM, whereas, it has a linear relationship with Strehl ratio and percentage of energy in FWHM. Therefore, the paper points out that FWHM of focus or severalfold diffraction limits cannot be simply used in giving the peak power density. Strehl ratio or the encircled energy within FWHM is more appropriate.