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A: Fachverband Atomphysik

A 25: Attosecond physics

A 25.6: Poster

Mittwoch, 13. März 2019, 16:15–18:15, S Fobau Physik

Trajectory control in XUV-initiated high-harmonic generation — •Michael Krüger, Doron Azoury, Barry D. Bruner, and Nirit Dudovich — Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel

A major limitation of high-harmonic generation (HHG) is the fact that the strong driving laser field governs the entire generation process. XUV-initiated HHG replaces the tunnel ionization step in HHG by XUV-driven photoionization, overcoming this limitation [1]. Controlling the delay between an ionizing XUV field and a strong IR laser pulse determines the time instant when electrons are promoted to the continuum and undergo IR-driven recollision. Moreover, an additional second harmonic (SH) field breaks the symmetry of the system, probing the strong-field driven trajectories. In our study, we use the XUV and SH fields to fully control the HHG process, switching between long and short trajectories and achieving frequency tuning of the resulting harmonics. Moreover, we are able to directly observe a new class of trajectories, so-called ``downhill'' and ``uphill'' trajectories; here the excess energy of the photoelectron following XUV ionization leads to an extra momentum kick in the direction of the instantaneous IR field force (downhill) or against it (uphill). Our study bears the prospect of increasing the dimensionality of high-harmonic generation spectroscopy for probing complex systems and multi-electron effects.

[1] D. Azoury et al., Nature Communications 8, 1453 (2017).