Stuttgart 2012 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 25: Poster: Attosecond physics

A 25.2: Poster

Mittwoch, 14. März 2012, 16:30–19:00, Poster.V

Quantitative measurement of phase matching in high harmonic generation — Sudipta Mondal¹, •Frederic L. Condin^1,2, Philipp L. Klaus^1,3, Kristen Gould⁴, Benjamin Wilson⁴, Erwin D. Poliakoff⁴, and Carlos A. Trallero-Herrero¹ — ¹Department of Physics, Kansas State University, Manhattan, Kansas 66506, USA — ²Eberhard Karls Universität Tübingen, D-72074 Tübingen, Germany — ³Institut für Kernphysik, Goethe-Universität Frankfurt am Main, D-60438 Frankfurt am Main, Germany — ⁴Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA

Phase matching in high harmonic generation (HHG) is crucial for the quality and intensity of the generated harmonics and has important applications in modern attosecond science. We present a quantitative measurement of phase matching in HHG. In our experiments we simultaneously detect the generated harmonics and the produced ions as a function of laser focus position relative to a thin gas jet, intensity, and pressure for two pulse durations. The ion signal, the HHG yield, and the HHG yield divided by the squared ion signal serve as a measure of phase matching [cf. PRL 103, 073902 (2009) for a justification of the latter]. We find that the conditions for ideal phase matching drastically change when we switch from Gaussian to Bessel mode. The results have implications for our ongoing research efforts to use HHG as a spectroscopic method. Using the recently developed quantitative rescattering theory of HHG [PRA 80, 013401 (2009)], we want to extract photoionization cross sections from HHG spectra.