The compression of a laser pulse by amplification of an ultra short pulse beam which seeds the stimulated Raman scatter of the first beam has been long been discussed in the context of solid and gas media. We investigate the possibility of using intersecting beams in a plasma to compress nanosecond pulses to picosecond duration by scattering from driven electron waves. Recent theoretical studies have shown the possibility of efficient compression with large amplitude, non-linear Langmuir waves driven either by SRS [1] or non-resonantly [2]. We describe experiments in which a plasma suitable for pulse compression is created, and amplification of an ultra short pulse beam is demonstrated.

The next generation of large-scale free-electron lasers (FELs) such as Euro-XFEL and LCLS are to be devices which produce coherent X-rays using Self-Amplified Spontaneous Emission (SASE). The performance of these devices is limited by the spread in longitudinal velocities of the beam. In the case where this spread arises primarily from large transverse oscillation amplitudes, beam conditioning can significantly enhance FEL performance. Future X-ray sources may also exploit harmonic generation starting from laser-seeded modulation. Preliminary analysis of such devices is discussed, based on a novel trial-function/variational-principle approach, which shows good agreement with more lengthy numerical simulations.

The compression of a laser pulse by amplification of an ultra short pulse beam which seeds the stimulated Raman scatter of the first beam has been long been discussed in the context of solid and gas media. We investigate the possibility of using intersecting beams in a plasma to compress nanosecond pulses to picosecond duration by scattering from driven electron waves. Recent theoretical studies have shown the possibility of efficient compression with large amplitude, non-linear Langmuir waves driven either by SRS [1] or non-resonantly [2].