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Author: Elsaesser, Thomas × Start date: 2010 × DDC: 510 × WGL Institute: MBI ×

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    Ultrafast spatio-temporal dynamics of terahertz generation by ionizing two-color femtosecond pulses in gases
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 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.
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    Non-instantaneous polarization dynamics in dielectric media
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2014) Hofmann, Michael; Hyyti, Janne; Birkholz, Simon; Bock, Martin; Das, Susanta K.; Grunwald, Rüdiger; Hoffmann, Mathias; Nagy, Tamas; Demircan, Ayhan; Jupé, Marco; Ristau, Detlev; Morgner, Uwe; Brée, Carsten; Woerner, Michael; Elsaesser, Thomas; Steinmeyer, Günter
    Third-order optical nonlinearities play a vital role for generation1,2 and characterization 3-5 of some of the shortest optical pulses to date, for optical switching applications6,7, and for spectroscopy8,9. In many cases, nonlinear optical effects are used far off resonance, and then an instantaneous temporal response is expected. Here, we show for the first time resonant frequency-resolved optical gating measurements1012 that indicate substantial nonlinear polarization relaxation times up to 6.5 fs in dielectric media, i.e., significantly beyond the shortest pulses directly available from commercial lasers. These effects are among the fastest effects observed in ultrafast spectroscopy. Numerical solutions of the time-dependent Schrödinger equation13,14 are in excellent agreement with experimental observations. The simulations indicate that pulse generation and characterization in the ultraviolet may be severely affected by this previously unreported effect. Moreover, our approach opens an avenue for application of frequency-resolved optical gating as a highly selective spectroscopic probe in high-field physics.