Abstract

Femtosecond filaments occur as the focusing nature of the Kerr-effect is balanced by plasma defocusing. The fundamental pulse undergoes complex spatio-temporal dynamics as it forms a high-intensity self-guiding channel, in which the intensity is assumed to be clamped to a value of approximately 5×10¹³ W/cm² [1]. The emerging pulse shows characteristic features of spectral broadening, pulse-splitting as well as self-shortening. Experimentally however, accessing direct information about the pulse’s structure and its intensity as it propagates in the self-induced channel remains a challenging task. Approaches to measure the intensity rely on implications drawn from burn patterns on paper or fluorescence induced by the filament [2,3]. The pulse’s structure can be reconstructed by directly applying a pulse-reconstruction method [4] or by using a differential pumping stage setup consisting of two consecutive pinholes to truncate the filament in the self-guiding area, as it is done in our previous and present works [5].

© 2015 IEEE