External focusing dependence of spatial distribution of air lasers during femtosecond laser filamentation in air  

作　　者：Jiayun Xue Hui Gao Nan Zhang Lu Sun Lie Lin Weiwei Liu 薛嘉云;高慧;张楠;孙陆;林列;刘伟伟(Institute of Modern Optics,Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology,Nankai University,Tianjin 300350,China;School of Physical Science and Technology,Tiangong University,Tianjin 300387,China)

机构地区：[1]Institute of Modern Optics,Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology,Nankai University,Tianjin 300350,China [2]School of Physical Science and Technology,Tiangong University,Tianjin 300387,China

出　　处：《Chinese Optics Letters》2021年第8期18-22,共5页中国光学快报（英文版）

基　　金：supported by the National Key R&D Program of China (No.2018YFB0504400)。

摘　　要：The spatial distribution of the forward-propagating amplified spontaneous emission(ASE) of nitrogen molecular ions during femtosecond laser filamentation in air is studied via numerical simulations. The results suggest that the divergence angle and signal intensity are extremely sensitive to the external focal length. Concurrently, we show that the optical Kerr effect plays a significant role in concentrating the directivity of ASE signals, particularly in cases of loose focusing. Furthermore,the simulations demonstrate that ASE signals are enhanced for a tight focus, although the corresponding filament length is shorter. The main physical mechanism underlying this process is the competition between the plasma defocusing and optical Kerr effects. The result is important for filamentation-based light detection and ranging applied to remote sensing.

关 键 词：air laser amplified spontaneous emission femtosecond laser filamentation 

分 类 号：TN24[电子电信—物理电子学]