中国物理B ›› 2023, Vol. 32 ›› Issue (3): 34204-034204.doi: 10.1088/1674-1056/aca4bf

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Spectral shift of solid high-order harmonics from different channels in a combined laser field

Dong-Dong Cao(曹冬冬)1, Xue-Fei Pan(潘雪飞)2, Jun Zhang(张军)1,†, and Xue-Shen Liu(刘学深)1,‡   

  1. 1 Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;
    2 College of Science, Northeast Forestry University, Harbin 150040, China
  • 收稿日期:2022-09-06 修回日期:2022-11-09 接受日期:2022-11-22 出版日期:2023-02-14 发布日期:2023-02-21
  • 通讯作者: Jun Zhang, Xue-Shen Liu E-mail:junzhang@jlu.edu.cn;liuxs@jlu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12074142 and 11904122).

Spectral shift of solid high-order harmonics from different channels in a combined laser field

Dong-Dong Cao(曹冬冬)1, Xue-Fei Pan(潘雪飞)2, Jun Zhang(张军)1,†, and Xue-Shen Liu(刘学深)1,‡   

  1. 1 Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;
    2 College of Science, Northeast Forestry University, Harbin 150040, China
  • Received:2022-09-06 Revised:2022-11-09 Accepted:2022-11-22 Online:2023-02-14 Published:2023-02-21
  • Contact: Jun Zhang, Xue-Shen Liu E-mail:junzhang@jlu.edu.cn;liuxs@jlu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12074142 and 11904122).

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摘要： We investigate theoretically the spectral shift of the high-order harmonic generation (HHG) in ZnO driven by a combined laser field by solving the two-band semiconductor Bloch equations (SBEs) in the velocity gauge. The combined laser field is synthesized by a fundamental laser pulse and its seventh-frequency laser pulse. When the seventh-frequency laser pulse is added to the rising or falling parts of the fundamental laser field, we find that the spectral blueshift or redshift appears, which is due to the unequal contribution of the rising and falling parts in the fundamental laser field to the harmonics. By analyzing the time-dependent conduction band population in k space, we found that, in addition to the tunneling ionization channel, there is also the resonant electron injection channels which is induced by the seventh-frequency laser pulse. The harmonics generated by the different channels show the spectral redshift or the spectral blueshift, respectively. Through analyzing the k-integrated transient conduction band population of the electrons from different channels, we found that if there is a certain delay in the process of the electron excitation, it will lead to the delay in the harmonic emission, which results in the spectral redshift of the harmonics.

关键词: high-order harmonic generation, ZnO crystal, spectral shift of harmonics, resonant electron injection channels

Abstract: We investigate theoretically the spectral shift of the high-order harmonic generation (HHG) in ZnO driven by a combined laser field by solving the two-band semiconductor Bloch equations (SBEs) in the velocity gauge. The combined laser field is synthesized by a fundamental laser pulse and its seventh-frequency laser pulse. When the seventh-frequency laser pulse is added to the rising or falling parts of the fundamental laser field, we find that the spectral blueshift or redshift appears, which is due to the unequal contribution of the rising and falling parts in the fundamental laser field to the harmonics. By analyzing the time-dependent conduction band population in k space, we found that, in addition to the tunneling ionization channel, there is also the resonant electron injection channels which is induced by the seventh-frequency laser pulse. The harmonics generated by the different channels show the spectral redshift or the spectral blueshift, respectively. Through analyzing the k-integrated transient conduction band population of the electrons from different channels, we found that if there is a certain delay in the process of the electron excitation, it will lead to the delay in the harmonic emission, which results in the spectral redshift of the harmonics.

Key words: high-order harmonic generation, ZnO crystal, spectral shift of harmonics, resonant electron injection channels

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

  • 32.80.Rm
42.65.Ky (Frequency conversion; harmonic generation, including higher-order harmonic generation) 42.65.Re (Ultrafast processes; optical pulse generation and pulse compression)