We report theoretical calculations of high-order harmonic generation (HHG) by intense infrared lasers in atomic and molecular targets taking into account the macroscopic propagation of both fundamental and harmonic fields. On the examples of Ar and N₂, we demonstrate that these ab initio calculations are capable of accurately reproducing available experimental results with isotropic and aligned target media. We further present detailed analysis of HHG intensity and phase under various experimental conditions, in particular, as the wavelength of the driving laser changes. Most importantly, our results strongly support the factorization of HHG at the macroscopic level into a product of a returning electron wave packet and the photorecombination transition dipole under typical experimental conditions. This implies that the single-atom or single-molecule structure information can be retrieved from experimentally measured HHG spectra.



Keywords and Phrases

Ab Initio Calculations; Electron Wave Packet; Experimental Conditions; Harmonic Field; High Order Harmonic Generation; Macroscopic Levels; Molecular Targets; Photorecombination; Propagation Effect; Single-Molecule; Structure Information; Theoretical Calculations; Transition Dipole, Atomic Spectroscopy; Harmonic Analysis; Harmonic Generation; Isomers, Infrared Lasers

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Article - Journal

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