2010, Babushkin, Ihar, Kuehn, Wihelm, Köhler, Christian, Skupin, Stefan, Bergé, Luc, Reimann, Klaus, Woerner, Michael, Herrmann, Joachim, Elsaesser, Thomas

We present a combined theoretical and experimental study of spatio-temporal propagation effects in terahertz (THz) generation in gases using two-color ionizing laser pulses. The observed strong broadening of the THz spectra with increasing gas pressure reveals the prominent role of spatio-temporal reshaping and of a plasma-induced blue-shift of the pump pulses in the generation process. Results obtained from (3+1)-dimensional simulations are in good agreement with experimental findings and clarify the mechanisms responsible for THz emission.