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Start date: 2010 × DDC: 510 × Subject: nonlinear optics × WGL Institute: MBI ×

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Now showing 1 - 2 of 2
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    Directionality of THz emission from photoinduced gas plasmas
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2011) Köhler, Christian; Cabrera-Granado, Eduardo; Babushkin, Ihar; Bergé, Luc; Herrmann, Joachim; Skupin, Stefan
    Forward and backward THz emission by ionizing two-color laser pulses in gas is investigated by means of a simple semi-analytical model based on Jefimenko's equation and rigorous Maxwell simulations in one and two dimensions. We find the emission in backward direction having a much smaller spectral bandwidth than in forward direction and explain this by interference effects. Forward THz radiation is generated predominantly at the ionization front and is thus almost not affected by the opacity of the plasma, in excellent agreement with results obtained from a unidirectional pulse propagation model.
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    Tailoring THz radiation by controlling tunnel photoionization events in gases
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2011) Babushkin, Ihar; Skupin, Stefan; Husakou, Anton; Köhler, Christian; Cabrera-Granado, Eduardo; Bergé, Luc; Herrmann, Joachimj
    Applications ranging from nonlinear terahertz spectroscopy to remote sensing require broadband and intense THz radiation which can be generated by focusing two-color laser pulses into a gas. In this setup, THz radiation originates from the buildup of the electron density in sharp steps of attosecond duration due to tunnel ionization, and subsequent acceleration of free electrons in the laser field. We show that the spectral shape of the THz pulses generated by this mechanism is determined by superposition of contributions from individual ionization events. This provides a straightforward analogy with linear diffraction theory, where the ionization events play the role of slits in a grating. This analogy offers simple explanations for recent experimental observations and opens new avenues for THz pulse shaping based on temporal control of the ionization events. We illustrate this novel technique by tailoring the spectral width and position of the resulting radiation using multi-color pump pulses.