Bonn 2000 – scientific programme
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A: Atomphysik
A 16: Multiphotonenprozesse I
A 16.7: Talk
Thursday, April 6, 2000, 15:30–15:45, HS I
Phase-dependent effects in bichromatic high-harmonic generation — •C. F. de M. Faria1, D. B. Milošević2, and G. G. Paulus3 — 1Max Planck Institut für Physik komplexer Systeme, Nöthnizer Str. 38, 01187 Dresden — 2Max Born Institut für nichlineare Optik und Kurzzeitspektroskopie, Max Born Str. 2A, 12489 Berlin — 3Max Planck Institut für Quantenoptik, Hans-Kopfermann Str. 1, 85748 Garching
We give a physical explanation for a π-periodic modulation in the harmonic yield as a function of the relative phase between both driving waves, and an offset phase shift of this modulation for neighboring cutoff harmonics, observed in recent experiments on high-harmonic generation with phase-controlled ω−2ω bichromatic fields [1]. Using the “simple-man" or classical model, the strong-field approximation and the fully numerical solution of the time-dependent Schrödinger equation, we relate this offset phase shift to a particular set of electron trajectories [2]. We show that, with the introduction of the high-frequency field, the monochromatic cutoff energy Ip+3.17Up splits into an upper and lower branch, which present different types of behavior with respect to the relative phase. Whereas the energy of the upper branch does not vary considerably with this parameter, the energy of the lower branch is strongly phase-dependent. Precisely this phase dependence originates the offset phase shift in the modulation. Thus, using bichromatic fields, one is able to single out a set of trajectories according to its phase dependence, already at the single-atom-response level.
[1] U. Andiel et.al, Europhys. Lett. 47, 42 (1999).
[2] C. F. de M. Faria, D. B. Milošević, and G.G. Paulus, preprint