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Proceedings Paper

Off-axial phase-matched high-order harmonic generation in extended medium under self-guiding of a laser beam
Author(s): V. T. Platonenko; V. V. Strelkov; G. Ferrante
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Paper Abstract

We present results of analytical and numerical calculations of the angular spectrum and the power of high-order harmonics generated with a limited laser beam in an extended medium. It is shown that the spectrum of harmonics generated in a thick target dramatically differs from that of the single-atom response. In particular, in this spectrum there are two plateaus due to off-axially phase-matched generation of some harmonics (phase-matching condition holds only for a part of the harmonic angular spectrum). The origin that makes the off-axially phase-matched generation effective is the amplitude modulation of the high-frequency single-atom response in the laser beam cross section that increases the divergence of the harmonic beam. In Gaussian beams the off- axially phase-matched generation in extended medium (i.e. under target thickness close to the confocal length) is effective under any value of geometrical dispersion (i.e. under arbitrary hard focusing). Our treatment explains features of the high harmonic spectra obtained experimentally using extended targets as well as high conversion efficiencies achieved in these experiments. It is shown that under self-guiding of a laser beam in a noble gas off-axially phase-matched high harmonic generation is possible if some easily ionizable gas is added to the main generating gas. In calculations of high-order harmonic generation in such mixtures conversion efficiency as high as approximately10-3 - 10-2 for 33-rd harmonic of Titanum-Sapphire laser and about 10-4 for 121-st one is obtained.

Paper Details

Date Published: 29 May 2002
PDF: 12 pages
Proc. SPIE 4752, ICONO 2001: Ultrafast Phenomena and Strong Laser Fields, (29 May 2002); doi: 10.1117/12.469105
Show Author Affiliations
V. T. Platonenko, M.V. Lomonosov Moscow State Univ. (Russia)
V. V. Strelkov, M.V. Lomonosov Moscow State Univ. (Russia)
G. Ferrante, INFM and Univ. degli Studi di Palermo (Italy)

Published in SPIE Proceedings Vol. 4752:
ICONO 2001: Ultrafast Phenomena and Strong Laser Fields
Vyacheslav M. Gordienko; Anatoly A. Afanas'ev; Vladimir V. Shuvalov, Editor(s)

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