https://doi.org/10.1140/epjd/e2014-50086-6
Regular Article
High-order harmonic generation at high laser intensities beyond the tunnel regime⋆
1 Centro de Láseres Pulsados (CLPU),
Parque Científico, 37185 Villamayor, Salamanca, Spain
2 Department of Physics, Auburn
University, Auburn,
Alabama
36849,
USA
3 ICFO-Institut de Ciències Fotòniques, Av. Carl Friedrich
Gauss 3, 08860 Castelldefels (Barcelona), Spain
4 ICREA-Institució Catalana de Recerca
i Estudis Avançats, Lluis Companys 23, 08010
Barcelona,
Spain
5 Department of Physics, Blackett
Laboratory, Imperial College
London, London
SW7 2AZ,
UK
a
e-mail: joseap@usal.es
b
Present address: Max-Planck-Institut für Quantenoptik,
Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
Received:
31
January
2014
Received in final form:
23
April
2014
Published online:
24
July
2014
We present studies of high-order harmonic generation (HHG) at laser intensities well above saturation. We use driving laser pulses which present a particular electron dynamics in the turn-on stage. Our results predict an increasing on the harmonic yield, after an initial dropping, when the laser intensity is increased. This fact contradicts the general belief of a progressive degradation of the harmonic emission at ultrahigh intensities. We have identified a particular set of trajectories which emerges in the turn-on stage of these singular laser pulses, responsible of the unexpected growth on the harmonic efficiency at this high intensity regime. Our study combines two complementary approaches: classical analysis and full quantum mechanical calculations resulting from the numerical integration of the 3-dimensional time-dependent Schrödinger equation complemented with the time-frequency analysis.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2014