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Terahertz emission from laser-driven gas-plasmas: a plasmonic point of view
preprintposted on 2023-11-30, 05:26 authored by I. Thiele, B. Zhou, A. Nguyen, E. Smetanina, R. Nuter, K. J. Kaltenecker, J. Déchard, P. González de Alaiza Martínez, L. Bergé, P. U. Jepsen, S. Skupin
We disclose an unanticipated link between plasmonics and nonlinear frequency down-conversion in laser-induced gas-plasmas. For two-color femtosecond pump pulses, a plasmonic resonance is shown to broaden the terahertz emission spectra significantly. We identify the resonance as a leaky mode, which contributes to the emission spectra whenever electrons are excited along a direction where the plasma size is smaller than the plasma wavelength. As a direct consequence, such resonances can be controlled by changing the polarization properties of elliptically-shaped driving laser pulses. Both, experimental results and 3D Maxwell consistent simulations confirm that a significant terahertz pulse shortening and spectral broadening can be achieved by exploiting the transverse driving laser beam shape as an additional degree of freedom.