A novel and precise micron-scale nanosecond laser spot measurement based on film-scanning method is presented. The method can be used to measure the spot size, beam profile, and intensity distribution of the pulse. The central spot radius of the pulsed Bessel beams with pulse width of 25 ns is measured to be 94.86+-5 \mum in our experiment through the analysis of the digital image by film scanning, and the result is consistent with the theoretical value of 92.33 \mum. Compared with charge-coupled device/complementary metal oxide semiconductor (CCD/CMOS) laser beam profilers, the film-scanning method shows higher measurement accuracy, single shot ultrashort pulse measurable, larger measurable size, and wider measurable wavelength range.

从理论和实验两方面分析测定了纳秒无衍射贝塞耳光脉冲的相关参量。由广义惠更斯-菲涅耳衍射积分理论出发给出了平行光通过轴棱锥后的光场分布、最大无衍射准直距离、最小中心光斑半径等参量的表达式,并进行相关参量的数值模拟。实验采用平-抗共振环(ARR)腔被动调Q Nd:YAG激光器和轴棱锥系统获得了高稳定的纳秒贝塞耳光脉冲,测定了其脉冲宽度、最大无衍射距离、横面光强分布及最小中心亮斑尺寸,实验结果与理论分析相吻合。利用胶片扫描法给出了光脉冲的截面光强分布精细结构,其分辨率远高于普通的光束分析仪。