Abstract

We experimentally demonstrate third-harmonic generation (THG) in gases ionized by a femtosecond laser pulse superimposed on its second-harmonic (SH). The mechanism of THG has been investigated, and it demonstrates that a third-order nonlinear process dominates at low pump intensity. Asymmetric third-harmonic (TH) spectra are observed at different time delays in two color fields, which are attributed to the process of the four-wave mixing (FWM) of the broad spectrum of pump pulses. A joint measurement on the terahertz (THz) and the TH is performed. It reveals that the optimized phase for the THG jumps from 0 to 0.5π as the pump intensity increases, which is different from the THz being a constant, and indicates that the THG arises from the nonlinearity of the third-order bound electrons to the tunnel-ionization current.

© 2023 Chinese Laser Press

Combined action of the bound-electron nonlinearity and the tunnel-ionization current in low-order harmonic generation in noble gases

Usman Sapaev, Anton Husakou, and Joachim Herrmann
Opt. Express 21(21) 25582-25591 (2013)

Third-order harmonic generation in a bi-chromatic elliptical laser field

Tao He, Yizhu Zhang, J. J. Zhao, Xincheng Wang, Zhenjie Shen, Zuanming Jin, Tian-Min Yan, and Yuhai Jiang
Opt. Express 29(14) 21936-21946 (2021)

Enhanced XUV harmonics generated in mixed noble gases using three-color laser fields

Ganjaboy S. Boltaev, Rashid A. Ganeev, and Ali S. Alnaser
Opt. Express 32(1) 113-124 (2024)

Trajectory analysis for low-order harmonic generation in two-color strong laser fields

Xingwang Fan, Yuan Gao, Tian-Min Yan, Yuhai Jiang, and Yizhu Zhang
Opt. Express 31(1) 86-94 (2023)

Quasi-phase-matching for third harmonic generation in noble gases employing ultrasound

U. K. Sapaev, I. Babushkin, and J. Herrmann
Opt. Express 20(20) 22753-22762 (2012)