Multi-dimensional observation of white-light filaments generated by femtosecond laser pulses in condensed medium.

The generation dynamics of white-light filaments in a transparent condensed medium is investigated experimentally in both spatiotemporal and frequency domains. We visualize the creation of multiple refocusing filaments with gradual increase of laser power by characterizing their spatial distributions of plasma luminescence and corresponding far-field emission patterns. The spatial fusion of multiple refocusing filaments into a single relatively long plasma channel is found to take place at higher laser powers. The measurement of supercontinua indicates that filamentation of ultrashort laser pulses in dispersive bulk media is closely connected with subsequent temporal events of pulse single splitting, then multiple splittings and finally coalescence. In addition, typical interference patterns of far-field emission are observed in the experiment, which reveals the spatial coherent properties among transverse filaments that are produced by a single laser beam.