中国物理B ›› 2015, Vol. 24 ›› Issue (7): 73201-073201.doi: 10.1088/1674-1056/24/7/073201

• ATOMIC AND MOLECULAR PHYSICS • 上一篇    下一篇

Dependence of above-threshold ionization spectrum on polarization directions of two-color laser fields

刘敏a b, 郭迎春a, 王兵兵b   

  1. a Department of Physics, East China Normal University, Shanghai 200241, China;
    b Laboratory of Optical Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 收稿日期:2014-12-23 修回日期:2015-03-05 出版日期:2015-07-05 发布日期:2015-07-05
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (Grant Nos. 11474348 and 61275128).

Dependence of above-threshold ionization spectrum on polarization directions of two-color laser fields

Liu Min (刘敏)a b, Guo Ying-Chun (郭迎春)a, Wang Bing-Bing (王兵兵)b   

  1. a Department of Physics, East China Normal University, Shanghai 200241, China;
    b Laboratory of Optical Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • Received:2014-12-23 Revised:2015-03-05 Online:2015-07-05 Published:2015-07-05
  • Contact: Guo Ying-Chun, Wang Bing-Bing E-mail:ycguo@phy.ecnu.edu.cn;wbb@aphy.iphy.ac.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Grant Nos. 11474348 and 61275128).

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摘要：

Using the frequency-domain theory, we investigate the above-threshold ionization (ATI) process of an atom in two-color laser fields. When both photon energies of the two-color laser fields are much smaller than the atomic ionization threshold, the ATI spectrum depends on the angle between the two lasers' polarization directions. While when the photon energy of one laser is comparable with or larger than the atomic ionization threshold, the ATI spectrum is independent of the angle, and only several dips appear at certain angles. By analyzing the contributions of different quantum channels, we find that, for the case that both frequencies of the two color lasers are low, the quantum interferences between the channels are strong, and hence the spectrum changes with the angle between the two lasers' polarization directions. While for the case that the frequency of one of the two color lasers is high, the contributions of the channels to the ATI spectrum decrease dramatically with increasing channel order, hence the interferences between the channels disappear, and the ATI spectrum has a step-like structure, which is independent of the angle between the two lasers' polarizations. These results can shed light on the study of the corresponding relation between classical and quantum mechanisms of the matter–laser interaction in high-frequency laser fields.

关键词: above-threshold ionization, two-color laser fields, quantum interference

Abstract:

Using the frequency-domain theory, we investigate the above-threshold ionization (ATI) process of an atom in two-color laser fields. When both photon energies of the two-color laser fields are much smaller than the atomic ionization threshold, the ATI spectrum depends on the angle between the two lasers' polarization directions. While when the photon energy of one laser is comparable with or larger than the atomic ionization threshold, the ATI spectrum is independent of the angle, and only several dips appear at certain angles. By analyzing the contributions of different quantum channels, we find that, for the case that both frequencies of the two color lasers are low, the quantum interferences between the channels are strong, and hence the spectrum changes with the angle between the two lasers' polarization directions. While for the case that the frequency of one of the two color lasers is high, the contributions of the channels to the ATI spectrum decrease dramatically with increasing channel order, hence the interferences between the channels disappear, and the ATI spectrum has a step-like structure, which is independent of the angle between the two lasers' polarizations. These results can shed light on the study of the corresponding relation between classical and quantum mechanisms of the matter–laser interaction in high-frequency laser fields.

Key words: above-threshold ionization, two-color laser fields, quantum interference

中图分类号:  (Multiphoton ionization and excitation to highly excited states)

  • 32.80.Rm
42.50.Hz (Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift) 42.65.Ky (Frequency conversion; harmonic generation, including higher-order harmonic generation)