We study the influence of the driving laser intensity on the spectral features of high harmonic generation in a semi-infinite gas cell. The effects of the harmonic dipole phase and the dispersion phase mismatches induced by the ionized medium during the harmonic generation process are revealed and the interplay between the macroscopic response and the single-atom response is discussed. We consider the conditions for generation of a narrow bandwidth, bright, and highly coherent high harmonic source.
Received 12 December 2012Accepted 23 January 2013Published online 08 February 2013
Article outline: I. INTRODUCTION II. THEORETICAL BACKGROUND III. EXPERIMENTAL RESULTS AND DISCUSSION A. Spectral features of HHG at high laser intensity B. Spectral features of HHG with limitation of ionization fraction IV. CONCLUSIONS
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