3/2 harmonic generation by femtosecond laser pulses in steep-gradient plasmas.
The onset of an electron parametric instability and 3/2 harmonic generation in variable-scale-length plasmas on solid surfaces using femtosecond pulses is observed. With the intensity approaching 10(18) W/cm(2), the instability threshold is already reached at plasma scale lengths of the order of the laser wavelength. A well-collimated harmonic emission with unusually broad spectrum is obtained.
Tarasevitch
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A
Institut für Laser-und Plasmaphysik, Universität Essen-Duisburg, D-45117 Essen, Germany. tar@iep.physik.uni-essen.de
Dietrich
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C
Blome
C
C
Sokolowski-Tinten
K
K
von der Linde
D
D