多太瓦IR飞秒laser泵浦微焦耳脉冲能量的大气激光
Lasing of ambient air with microjoule pulse energy pumped by a multi terawatt IR femtosecond laser
摘要：
报道了峰值功率达4 TW的800 nm飞秒激光脉冲泵浦大气的激光作用。在428 nm处的激光发射在泵浦激光功率的小范围内迅速增加，然后在~ 1.5 TW以上饱和。最大激光脉冲能量被测量为2.6 μ J，对应于MW范围内的发射功率，而在中等泵浦脉冲能量下测量到的最大转换效率为。灯丝等离子体内部的光学增益估计超过0.7/cm。激光发射示出了甜甜圈轮廓，反映了泵浦产生的白光连续体的空间分布，其充当激光的种子。我们把这种明显的饱和归因于等离子体放大区域中种子的散焦和种子强度的饱和。
英文摘要：
We report on the lasing action of atmospheric air pumped by an 800 nm femtosecond laser pulse with peak power up to 4 TW. Lasing emission at 428 nm increases rapidly over a small range of pump laser power, followed by saturation above ~ 1.5 TW. The maximum lasing pulse energy is measured to be 2.6 uJ corresponding to an emission power in the MW range, while a maximum conversion efficiency of is measured at moderate pump pulse energy. The optical gain inside the filament plasma is estimated to be excess of 0.7/cm. The lasing emission shows a doughnut profile, reflecting the spatial distribution of the pump-generated white-light continuum that acts as a seed for the lasing. We attribute the pronounced saturation to the defocusing of the seed in the plasma amplifying region and to the saturation of the seed intensity.
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