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P: Fachverband Plasmaphysik

P 10: Laser Plasmas I

P 10.5: Vortrag

Dienstag, 6. März 2018, 15:15–15:30, KI 1.174

Plasma Diagnostics with sub-15-fs time resolution via pump-probe experiments — •Michael Stumpf, Christian Greb, Julian Wegner, and Georg Pretzler — Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität Düsseldorf

We present a novel experimental setup using a pump-probe technique for observing the expansion of a laser-produced plasma in its early stage. Therefore, the probe beam is reflected at the evolving plasma and then imaged onto the detector by an achromatic lens. The generated phase shift is measured with a Mach-Zehnder interferometer and evaluated using Fourier Transformation. The whole apparatus has exceptional resolution in time (sub-15-fs), space (2 µm) and phase (0.3 rad). As an example, we present an experiment in which the plasma was generated by a laser pulse (pulse-duration 9 fs, maximum intensity 2.4·10¹⁷ W/cm²) focused onto an aluminum mirror. The probe beam was then reflected off the expanding plasma with various delays. To calculate the phase shift, the data from reflection on the plasma is compared with a clean reflection on the metallic mirror. The results illustrate the early-stage plasma expansion with unprecedented temporal resolution.