Fig. 1. (a) Two orthogonally polarized laser electric fields and trajectories of ionized electrons in the laser pulses. The black curve is the driving field polarized along the z axis, and the red short dash dot curve is the controlling field polarized along the x axis. The olive curves and the colorful line with symbol curves represent the electrons’ trajectories regulated by the driving field and the controlling field, respectively. For clarity, the trajectories are reduced by 300 times. (b) The enlargement of the shadow area in (a).

Fig. 2. (a) High-order harmonic spectra of He in the driving pulse. (b) High-order harmonic spectra of He in two orthogonally polarized laser pulses. The top right corners of (a) and (b) are the partially enlarged details.

Fig. 3. Time-frequency analysis of harmonic spectra (a) in the driving pulse and (b) in the two orthogonally polarized laser pulses.

Fig. 4. Spectral redshift of high-order harmonics and asymmetry coefficients.

Fig. 5. Ionization rate of He at different times. The red solid curve represents the ionization rate in the driving pulse, and the blue short dash curve represents the ionization rate in the two orthogonally polarized laser pulses.

Fig. 6. (a) The harmonic spectrum and (b) the corresponding time-frequency analysis. The controlling pulse is added in the falling part of the driving pulse with tdelay=4.75T. The top right corner of (a) is the partially enlarged details.

Fig. 7. Partial harmonic spectra for different time delays between the two orthogonally polarized laser fields with (a) positive time delays and (b) negative time delays. The orange dash lines correspond exactly to odd harmonics.

Fig. 8. (a) Harmonic orders of different recombination moments, and the relation between the ionization moment (red circle) and recombination moment (violet short dash curve) in the z direction for electrons ionized from 5.75T to 6.0T. The black solid curve represents the partial driving field. The olive and orange triangles point to the ionization time and recombination time of the 33th harmonic, respectively. (b) and (c) demonstrate trajectories of electrons along the x direction in the two laser fields with positive and negative time delays, respectively. The starting and ending times correspond to triangle marks in (a).