Session CP1 - Poster Session II.
POSTER session, Monday afternoon, November 15
Room Exhibit Hall A, SCC
An approach to compressing high-power laser beams in plasmas via coherent Raman sideband generation is described. The technique requires two beams: a pump and a probe detuned by a near-resonant frequency Ømega<ømega_p. The two laser beams drive a high-amplitude electron plasma wave (EPW) which modifies the refractive index of plasma so as to produce a periodic phase modulation of the incident laser with the laser beat period 2\pi/Ømega. Thus, a train of chirped laser beatnotes (each of duration 2\pi/Ømega) is formed in plasma. The chirp is positive (the longer-wavelength sidebands are advanced in time) when Ømega<ømega_p and negative otherwise. Finite group velocity dispersion (GVD) of radiation in plasma can compress the positively chirped beatnotes to a few-laser-cycle duration thus creating in plasma a sequence of sharp electromagnetic spikes separated in time by 2\pi/Ømega. Driven EPW locks the phase of laser sidebands and thus reduces the effect of GVD. Compression of the chirped beatnotes can be implemented in a separate plasma of higher density, where the laser sidebands become uncoupled.