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he propagation of intense laser pulses in a medium can lead to the formation of white-light filaments. Through nonlinear effects (e.g. selfphasemodulation) a spectral broadening is induced which in general allows for the production of shorter pulses. Under suitable conditions, the temporal compression of the pulses can occur by self-steepening and plasma effects, as shown in [1]. In our experiment, intense bandwidth-limited laser pulses (40 fs, 2.5 mJ) are focussed into a gas cell filled with argon. In a systematic study, we have analyzed the formation of the filaments by varying the gas pressure and the focussing conditions. The pulses formed in the filamentation process are characterized by measuring their optical spectrum and their temporal length using single-shot techniques. By solving the nonlinear Schrödinger equation, the propagation of the pulses is simulated and the impact of nonlinear and plasma effects on the pulses is discussed. [1] G. Stibenz, N. Zhavoronkov and G. Steinmeyer. Opt. Lett., 31:274, 2006 |
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