Authors Referees APS Members |
December 2007, to be published in Physical Review A
Amplification of high-order harmonics using weak perturbative high-frequency
radiation
The mechanism underlying the substantial amplification of the high-order harmonics $q \pm 2K$ ($K$ integer) upon the addition of a weak seed XUV field of harmonic frequency $q\omega$ to a strong IR field of frequency $\omega$ is analyzed in the framework of the quantum-mechanical Floquet formalism and the semiclassical re-collision model. According to the Floquet analysis, the high-frequency field induces transitions between several Floquet states and leads to the appearance of new dipole cross terms. The semiclassical re-collision model suggests that the origin of the enhancement lies in the time-dependent modulation of the ground electronic state induced by the XUV field. © 2008 The American Physical Society.
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