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SYLF: Symposium Wechselwirkung in starken Laserfeldern
SYLF 2: Strahlung
SYLF 2.5: Talk
Monday, March 15, 1999, 15:15–15:30, zo1
Cutoff law for phase-dependent two-color high-harmonic generation — •C. Figueira de Morisson Faria1, W. Becker1, M. Dörr1,2, and W. Sandner1 — 1Max Born Institut, Rudower Chaussee 6, 12489 Berlin,Germany — 2Physique Théorique, CP 227, Université Libre, B-1050 Bruxelles
We discuss the cutoff law for high-harmonic generation with bichromatic
driving fields of commensurate ω-2ω
frequencies, which replaces the simple
|Ip|+3.17 Up of the monochromatic case. We use numerical solutions of the
one-dimensional time-dependent Schrödinger equation (TDSE) and
compare them
to the three-step model [1]. We concentrate on how the amplitudes of both
driving fields and their
relative phase influence the cutoff frequencies
which, within the three-step model picture, correspond to extremal
kinetic energy of an electron returning to its parent ion. The phase-
and intensity-dependence of these trajectories are recovered by the
TDSE results [1,2]. However, the cutoff is a complicated function of
these two parameters, such that there is no simple analog of the result
for the monochromatic case. For the harmonics corresponding
to the most energetic cutoff, the intensity yield roughly follows the
quasi-static Landau ionization rate exp(−c/|E(t0)|) [2],
with E(t0) being the field at the classical
emission time t0 of the electron into the continuum.
[1]C. Figueira de Morisson Faria, W. Becker, M. Dörr and W. Sandner,
Laser Phys. to be published.
[2] C. Figueira de Morisson Faria, M. Dörr, W. Becker and W. Sandner, preprint.