Time-frequency analysis of two-color high-harmonic generation

We investigate the validity of classical rescattering models for describing high-harmonic generation with coherent bichromatic driving fields. We compare the fully time-dependent solution of the one-dimensional Schrödinger equation to the predictions of the semiclassical three-step model, with particular emphasis on the return times and cutoff energies. The classical return times can be compared to the time of harmonic emission, obtained from the solution of the time-dependent Schrödinger equation with the help of a time-frequency analysis. Our strikingly coincident results indicate that also in the bichromatic case, provided the field is sufficiently intense and the two driving harmonic fields of comparable intensity, the three-step model describes the essential physical process and has a very good predictive power.