Study of Laser-Hole Boring into Overdense Plasmas

Abstract

Laser channeling into an overdense plasma was studied using time-resolved spectra of a backscattered laser light. A 1053 nm laser light was focused on a preformed plasma at a laser intensity of $2\ifmmode\times\else\texttimes\fi{}{10}^{17}\phantom{\rule{0ex}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$ with a pulse duration of 100 psec. The preformed plasma was created with a $100\ensuremath{-}\ensuremath{\mu}\mathrm{m}$ plastic target irradiated by 351-nm laser lights. Temporal profiles of the backscattered light and the angular distribution of scattered light indicate laser-hole boring in the preformed plasma. The x-ray pinhole images and strong redshift of the backscattered light spectrum are consistent with the channel formation into an overdense region.