Time-dependent density functional theory study of high-order harmonic generation from benzene driven by an orthogonally polarized two-color field

Abstract We investigate high-order harmonic generation (HHG) from a benzene molecule fixed in the xy plane and driven by an orthogonally polarized ω–2ω field using time-dependent density-functional theory (TDDFT). We systematically compare the effects of the relative phase, the second-harmonic-to-fundamental intensity ratio, and the polarization geometry. For the (ω, 2ω) = (x, y) configuration, odd harmonics dominate the x-polarized response, whereas even harmonics dominate the y-polarized response, in agreement with the dynamical-symmetry selection rules. Variation of the relative phase mainly redistributes individual harmonic intensities and modifies the orbital-depletion amplitudes, while the overall plateau extent, high-order spectral decay, and ordering of the most strongly depleted orbitals remain nearly unchanged. The orbital-resolved and coherent multiorbital spectra further show that orbital depletion is not directly correlated with the orbital contribution to HHG: although HOMO and HOMO-1 exhibit the strongest depletion, HOMO-7 contributes substantially to the total harmonic response. Compared with relative-phase variation, changes in the intensity ratio and polarization geometry produce larger changes in the mid- and high-order harmonic intensities, particularly along the second-harmonic polarization direction. Overall, the results show that relative phase primarily redistributes spectral weight, whereas the intensity ratio and polarization geometry more strongly reshape the mid- and high-order HHG response, with multiorbital effects playing an essential role in the molecular harmonic emission.