Harmonic generation by atoms interacting with intense ultrashort laser pulses

The interaction of intense ultrashort laser pulses with a gas of argon atoms is numerically investigated. The investigation utilizes a model that solves both the time-dependent Schrödinger equation and the wave equation self-consistently. The time-dependent Schrödinger equation for single-active electron in the effective static potential and in the potential of electron-laser interaction is solved using alternating direction implicit (Peaceman-Rachford) method. The Maxwell’s wave equation is solved using an explicit finite-difference technique. We show that, under some conditions, propagation effects can significantly change and clean up the single-atom emission spectrum. In few-cycles regime, a strong fluctuation of the XUV emission in the cut-off region is observed. This is due to change of carrier phase during the propagation.