Qu Wei-Xing

Temporal Behaviour of Harmonics from One-Dimensional H2+ in an Ultrashort Laser Pulse

With the method of wavelet transform, we consider the temporal behaviour of high-order harmonic generation from one-dimensional H2+ exposed to an ultrashort laser pulse with a duration of tens of femtoseconds. The results, which are calculated by numerically solving the corresponding time-dependent Schrodinger equation with the split-operator method in the non-Born-Oppenheimer approach, show that: (1) the high-order harmonics in the cut-off range emitted as a train of pulses have better coherence than those in the plateau; (2) the harmonics are emitted early in time when the intensity of the laser pulse increases.

Two-Colour Effect on the Ionization and Harmonic Generation of One-Dimensional He+

Using the one-dimensional ion mode, we theoretically investigate the dynamics ionization process and the high-order harmonic generation of the He+ subject to different kinds of two-colour laser pulses with the same fundamental frequency but various harmonic frequencies. It is found that from the results calculated by numerically solving the time-dependent Schrodinger equation, the two-colour laser pulse with the fundamental and harmonic frequencies enables the power spectrum of high-order harmonic generation to increase by a few orders of magnitude and the yield of He2+ to enhance significantly when the harmonic frequency of the laser pulse is close to the energy interval between the ground state and the first excited state of He+; even the harmonic field added into the pulse is much weaker than the fundamental one.

Dynamics of Interaction of H2+ with Intense Ultrashort Laser Pulse

The dynamic process of H2+ in intense ultrashort laser pulses with intensities of 1014 ~ 1015 W/cm2, wavelength of 532 nm and duration of 22 fs is theoretically investigated by using collinear model and numerically solving the time-dependent Schr?dinger equation. The results show that: (1) the dissociation and dissociative ionization compete each other in the case of intensities between 2.5 ? 1014 and 4.0 ? 1014 W/cm2; (2) both the dissociation and the dissociative ionization are much smaller and appear at about 5 cycles (?9 fs) later than the ionization. In addition, we estimate the spectrum of high harmonic generation and find that the well-known cutoff rule is invalid for the ultrashort laser pulse (e.g. the duration???25 fs), because the shorter pulse can produce higher order harmonics than the longer one.

Dynamics of H2+ in two-color ultrashort laser pulse

Numerical simulations of ionization and dissociation processes of hydrogen molecular ion H2+ interacting with two-color intense ( 1014W/cm2-1015W/cm2) ultrashort (the duration ≈ 22fs) laser pulse are made. The result shows that the ionization and dissociation processes are strongly dependent upon the relative phase between the two color fields. It means that, in the case of ultrashort pulse, the phase coherence control of ionization and dissociation processes can be realized.