Detailed time- and space-resolved electron density measurements are presented for laser-produced plasma waveguides. A density depression suitable for optical guiding begins to develop within the first few hundred picoseconds after plasma generation, during which rapid cooling occurs. At longer times the expansion closely follows that of a cylindrical blast wave, with further cooling due to expansion work. The waveguide profile is uniform over most of its length, with the density depression appearing within 150 μm of the ends.

• Received 12 November 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.2373