Friday, October 9, 2015

Abstract-Relativistic Doppler frequency up-conversion of terahertz pulses via reflection from photo-induced plasma fronts in solid-state media

Mark D. Thomson; Fanqi Meng; Hartmut G. Roskos

We have recently proposed and investigated the use of the relativistic Doppler reflection to up-shift the frequency of incident THz pulses, where the reflecting boundary is realized by a charge-carrier plasma front generated by a counter-propagating optical pump pulse in a semiconductor medium. In light of experimental results with high-resistivity silicon as the medium, here we employ numerical simulations to examine the effects of (i) the scattering time and (ii) pre-excitation of the plasma before the main pulse, which both can have a profound impact on the frequency up-conversion. These results also suggest that the initial effective Drude scattering time in silicon (before thermalization) may be below 10 femtoseconds, exemplifying the use of the Doppler reflective geometry as a novel probe of initial charge-carrier dynamics.

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