Open AccessA quantitative S-Matrix approach to high-order harmonic generation from multiphoton to tunneling regimes.
Author(s) -
Luis Plaja,
J. A. Pérez-Hernández
Publication year - 2007
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.15.003629
Subject(s) - physics , high harmonic generation , ionization , quantum tunnelling , optics , harmonic , coherent states , pulse (music) , phase (matter) , tunnel ionization , density matrix , second harmonic generation , atomic physics , quantum mechanics , laser , ion , quantum , detector
We present a S-matrix description of the process of high order harmonic generation during the interaction of atoms with strong electromagnetic fields. In contrast with the state-of-the-art approaches, our model does not employ the stationary phase approximation and accounts as well for the continuum-continuum transitions. Therefore we are able to reproduce quantitatively the higher frequency part of the spectrum for arbitrary pulse shapes, and for intensities corresponding to multiphoton, tunnel and soft over-the barrier ionization regimes. In addition this model can be implemented very efficiently in a Personal Computer to calculate the harmonic generation for the atom interacting with an eight-cycle pulse at lambda =800 nm in, roughly, ten minutes (a reduction of two orders of magnitude from the typical time requirements of the exact integration).