Hannover 2020 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 20: Laser plasma and laser applications 2
P 20.5: Vortrag
Donnerstag, 12. März 2020, 15:15–15:30, b302
Efficiency of bi-circular High Harmonic Generation with a kHz Laser — •Zahra Chitgar1, Roman Adam2, and Paul Gibbon1,3 — 1Jülich Supercomputing Centre, Forschungszentrum Jülich, Germany — 2Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich GmbH, Germany — 3Centre for Mathematical Plasma Astrophysics, KU Leuven, Belgium
Circularly-polarized (CP) extreme UV- and X-ray radiation is an essential tool for analyzing the magnetic properties of materials. Recently, CP high harmonic generation (HHG) has been demonstrated experimentally by focusing bi-chromatic (800 + 400nm wavelength), counter-rotating CP laser pulses into gas targets [Kfir, O. et al, Nat. Phot. (2015)], thus overcoming a long-standing limitation of HHG being only possible with linearly polarized light. The efficiency and brightness of such gas-based harmonics is ultimately restricted by the need to keep laser intensities below the ionization threshold, a limitation that can be overcome by using plasmas. Theoretical [Sharma, P. et al, Phys Plasmas (2018)] and numerical [Chen, Z. Phys Rev E (2018)] analysis have shown that a bi-circular laser driver can also work in under- and over dense plasmas with apparently the same selection rules as in gases, i.e. every third harmonic is suppressed and adjacent harmonics have opposite helicity. Here we demonstrate using both fluid and kinetic (PIC) modelling that bi-circular HHG has a comparable efficiency to the HHG source driven by linearly polarized laser light reflected from or transmitted through a thin ionized foil target with JuSPARC-VEGA laser parameters (40mJ, 25fs, 1kHz).