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 comp are the fully time-dependent solution of the one-dimensional Schrodinger eq uation to the predictions of the semiclassical three-step model, with parti cular emphasis on the return times and cutoff energies. The classical retur n times can be compared to the time of harmonic emission, obtained from the solution of the time-dependent Schrodinger equation with the help of a tim e-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 pow er. [S1050-2947(94)07208-X].