Mode control in a two-pulse-excited plasma waveguide

Abstract

We demonstrate that the application of a second excitation pulse to a laser-driven plasma waveguide [ Phys. Rev. Lett.71, 2409 ( 1993)] strongly influences the propagation of a guided probe pulse and offers further opportunity for mode control beyond that already demonstrated [ Opt. Lett.19, 1937 ( 1994)]. Under the conditions of leaky-mode propagation, the second excitation pulse promptly enhances the guided pulse transmission by driving the channel’s electron density barrier to increased height and thickness. The second excitation pulse also induces an inwardly directed compression wave in the channel, so that the guided pulse spot size is observed to decrease for early delays after the arrival of the second pulse. Guiding in a low-order mode is inhibited as this compression wave reaches the channel center but resumes at later times, as the channel center density relaxes.