,Spectral attenuation of a 400-nm laser pulse propagating through a plasma filament induced by an in

• 作 者: Quan-Jun Wang Rao Chen Jia-Chen Zhao Chun-Lin Sun Xiao-Zhen Wang Jing-Jie Ding Zuo-Ye Liu Bi-Tao Hu
• 机 构: School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China“,”College of Che
• 出 处: 中国物理B（英文版）
• 发表日期: 2020年1期
• 关键词: defocusing effect energy loss enhanced fluorescence

The spectral attenuation of a 400-nm probe laser propagating through a femtosecond plasma in air is studied. De-focusing effect of the low-density plasma is an obvious effect by examining the far-field pattes of the 400-nm pulse. Besides, the energy of 400-nm pulse drops after interaction with the plasma, which is found to be another effect leading to the attenuation. To reveal the physical origin behind the energy loss, we measure fluorescence emissions of the interaction area. The fluorescence is hardly detected with the weak 400-nm laser pulse, and the line spectra from the plasma filament induced by the 800-nm pump pulse are clearly shown. However, when the 400-nm pulse propagates through the plasma filament, the fluorescence at 391 nm from the first negative band system of N+2 is enhanced, while that from the second positive band of neutral N2 at 337 nm remains constant. Efficient near-resonant absorption of the 400-nm pulse by the first negative band system occurs inside the plasma, which results in the enhanced fluorescence. Furthermore, the spectral attenuation of the 400-nm probe laser is measured as a function of the pump-probe time delay as well as the pump-pulse energy.