Enhanced Population on Ionic Excited States by Synchronized Ionization and Multiphoton Resonance
Abstrak
We study population distributions and lasing actions of N_2^+ driven by femtosecond lasers with various wavelengths, and uncover an efficient ionic excitation mechanism induced by synchronized ionization and multiphoton resonance. Our results show that the strongest N_2^+ lasing appears around 1000 nm pump wavelength. At the optimal wavelength, the pump-energy threshold for air lasing generation is reduced by five folds compared with that required by the previous 800 nm pump laser. Simulations based on the ionization-coupling model indicate that although the Stark-assisted three-photon resonance can be satisfied within a broad pump wavelength range, the optimal pump wavelength arises when the dynamic three-photon resonance temporally synchronizes with the ionization injection. In this case, the ionic dipoles created at each half optical cycle have the same phase. The dipole phase locking promotes the continuous population transfer from ionic ground state to the excited state, giving rise to a dramatic increase of excited-state population. This work provides new insight on the photoexcitation mechanism of ions in strong laser fields, and opens up a route for optimizing ionic radiations.
Topik & Kata Kunci
Penulis (30)
Yewei Chen
H. Lei
Quanjun Wang
Hongqiang Xie
He Zhang
Xu Lu
Ning Zhang
Shunlin Huang
Yuzhu Wu
Jianpeng Liu
Qian Zhang
Yi Liu
Zengxiu Zhao
Jing Zhao
J. C. D. O. Physics
Shanghai Institute of Optics
Fine Mechanics
Chinese Academy of Sciences
D. Physics
National Institute of Technology
School of Optical-Electrical
Computer Engineering
University of Shanghai for Science andTechnology
School of Materials Science
East China University of Technology
Center of Materials Science
Optoelectronics Engineering
U. Sciences
School of Microelectronics
S. University
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