High-order-harmonic-generation spectroscopy with an elliptically polarized laser field

Harmonic generation spectroscopy with a two-colour laser field having orthogonal linear polarizations

“…This approach for describing HHG by a linearly polarized field has been presented in detail in [21] (for a monochromatic field) and [10] (for a two-colour field with parallel linear polarizations) and was generalized to the case of elliptic polarization in [16]. We extend it here to the case of a two-colour field with orthogonal polarizations, whose electric vector is…”

“…In the low-frequency (quasiclassical) approximation [21], the exact TDER result for the HHG amplitude reduces to a onedimensional integral similar to that for an elliptically polarized field [16], so that the harmonic rate R l,q (N) (l = 0, 1) for the Nth harmonic with energy E = N ω is given by…”

“…Thus, for a given electron energy E, 'one-dimensional' HHG spectroscopy with a linearly polarized field, provides only a single atomic parameter and does not allow one to retrieve the angular dependence of σ (E, α). Adding a phase-locked field polarized orthogonally to the fundamental driving field turns one-dimensional HHG spectroscopy into multi-dimensional spectroscopy [14][15][16][17] and provides access to more detailed information about the atomic and molecular response to the laser field, including the contributions of multiple ionic states and ionization timedelays. As shown in [16], the parameters σ 0 and β can be retrieved from HHG spectra in an elliptically polarized field with small ellipticity by means of polarization measurements, i.e.…”

“…In figure 1 we present 2D maps of the partial harmonic rates (4) of odd and even harmonics for substates ψ ±1 as functions of the harmonic number and the phase shift φ obtained by numerical evaluations of the integral in (5). (For the explicit dependence of the recombination matrix element ψ κlq |r|ψ K(t ) in (5) on the vector K(t ) see [16].) We note a number of qualitative features near the cutoff of HHG spectra for a p state:…”

“…For an initial s (l = 0) or p (l = 1) state, we use the same superpositions as for the case of elliptic polarization [16]:…”