Article

# Harmonic generation by atoms in circularly polarized two-color laser fields with coplanar polarizations and commensurate frequencies

11/2002; DOI:doi:10.1103/PhysRevA.68.053402
Source: arXiv

ABSTRACT The generation of harmonics by atoms or ions in a two-color, coplanar field configuration with commensurate frequencies is investigated through both, an analytical calculation based on the Lewenstein model and the numerical ab initio solution of the time-dependent Schroedinger equation of a two-dimensional model ion. Through the analytical model, selection rules for the harmonic orders in this field configuration, a generalized cut-off for the harmonic spectra, and an integral expression for the harmonic dipole strength is provided. The numerical results are employed to test the predictions of the analytical model. The scaling of the cut-off as a function of both, one of the laser intensities and frequency ratio $\eta$, as well as entire spectra for different $\eta$ and laser intensities are presented and analyzed. The theoretical cut-off is found to be an upper limit for the numerical results. Other discrepancies between analytical model and numerical results are clarified by taking into account the probabilities of the absorption processes involved. Comment: 8 figures

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### Keywords

8 figures

absorption processes

analytical calculation

analytical model

analyzed

coplanar field configuration

field configuration

frequency ratio $\eta$

generalized cut-off

harmonic dipole strength

harmonics

ions

laser intensities

numerical ab initio solution

numerical results

predictions

probabilities

scaling

selection rules

two-color