Cut-off law for high-harmonic generation by an elliptically polarized laser field

A quasi-classical three-step model for high-harmonic generation is presented. The results for the harmonic emission rate obtained using this model agree very well with the exact results. For an elliptically polarized laser field a staircase of plateaux is observed. Both the heights and the cut-off positions of these plateaux are explained. An analytical formula for the cut-off law is derived and applied to determine the cut-off of the harmonic spectrum for each of the observed plateaux. We also present the electron orbits, obtained as solutions of the classical equation of motion with the complex time.