Dramatic Spectral Broadening of Ultrafast Laser Pulses in Molecular Nitrogen Ions
Jin-Ming Chen1,3,4, Jin-Ping Yao1**, Zhao-Xiang Liu1,3, Bo Xu1,3, Fang-Bo Zhang1,3, Yue-Xin Wan1,3, Wei Chu1, Zhen-Hua Wang2, Ling-Ling Qiao1, Ya Cheng1,2,5**
1State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 2State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 3University of Chinese Academy of Sciences, Beijing 100049 4School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031 5Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006
Abstract：We investigate nonlinear interaction of nitrogen molecules with a two-color laser field composed by an intense 800 nm laser pulse and a weak 400 nm laser pulse. It is demonstrated that the spectrum of 400 nm pulses is dramatically broadened when the two beams temporally overlap. In comparison, the spectral broadening in argon is less pronounced, although argon atoms and nitrogen molecules have comparable ionization potentials. We reveal that the dramatic spectral broadening originates from the greatly enhanced nonlinear optical effects in the near-resonant condition of interaction between the 400 nm pulses and the nitrogen molecular ions.
2019, Vol. 36 
