Publisher’s Note: Analytic Description of the High-Energy Plateau in Harmonic Generation by Atoms: Can the Harmonic Power Increase with Increasing Laser Wavelengths? [Phys. Rev. Lett.102, 243901 (2009)]

Bicircular High-Harmonic Spectroscopy Reveals Dynamical Symmetries of Atoms and Molecules

“…Whereas the potential of high-harmonic spectroscopy (HHS) to probe the structure and dynamics of matter on the subfemtosecond and subangstrom scales has been well established [7][8][9][10][11][12][13][14], its ability to probe the symmetry of the medium on these time and length scales has not been addressed. High-harmonic generation from a linearly polarized driver is sensitive to inversion symmetry, the breaking of which leads to emission of even harmonics [15,16] that characterize the time-dependent electronic asymmetry of the studied sample [14,17].…”

Exchange and polarization effect in high-order harmonic imaging of molecular structures

“…Radiative recombination exhibits the richness and complexity * s.sukiasyan@imperial.ac.uk of its counterpart, the one-photon ionization. Not surprisingly, harmonic emission reflects this complexity (see, e.g., [11][12][13][14]), for example, through the coupling of different recombination channels via electron-electron interaction. Channel coupling induced by the returning electron can play an important role in significantly increasing the efficiency of harmonic generation at frequencies ∼10 2 eV [14].…”

“…These include: (i) (multielectron) polarization of the bound wave function in the neutral molecule and in the ion by the laser field [13,33,34], (ii) laser-induced electronic excitations on the subcycle time scale [32,33,35,36], including excitations in the ion between ionization and recombination, (iii) correlation-induced virtual and real excitations of the ionic electrons by the returning continuum electron, immediately prior and during recombination [13,14,37], (iv) excitations of collective modes (such as plasmons) in highly polarizable molecules and clusters [38,39], by both the laser field and the recolliding electron.…”

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

“…For a linearly polarized field, this factorization was proposed phenomenologically, based on numerical solutions of the time-dependent Schrödinger equation [3,4]. It has now been justified theoretically for a monochromatic field [5,6], for a short laser pulse [7][8][9], and for a two-colour field with collinearly polarized components [10].…”

“…Equation (7) shows that odd harmonics are linearly polarized along the directionx of the fundamental field polarization, while even harmonics are linearly polarized along the direction y of the second harmonic polarization, in agreement with results in [22] (see also [14]). 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].)…”