Raman Scattering and Chirped Pulse Amplification in Plasma
A high efficiency broad-band Raman chirped pulse amplifier
is being developed. The scheme involves a short seed pulse injected into
a preformed plasma waveguide channel where it is amplified by a counter-propagating,
high energy, long duration chirped pump pulse. Energy is transferred from
the pump to the seed by resonant excitation of a plasma wave.
This new type of amplifier presents unique features:
• Plasma, being a broken down medium, can sustain much higher power
densities than other amplifying media. Moreover interactions can take
place over several cm.
• A chirped pump distributes the gain spatially and provides the
bandwidth necessary to either amplify a short pulse or compress a long
• For a chirped pump pulse or a sufficiently intense seed pulse,
the superradiant regime can be accessed which allows for strong amplification
and compression of the seed pulse.
Moreover not only the Raman amplification mechanism represents a extremely
interesting new scheme to amplify short laser pulses without the need
of using a stretcher and a compressor, but it can also have important
implications for particle acceleration since it could provide a means
of energy replenishment for the main short laser pulse. It could therefore
play in a role in the staging of multiple accelerating structures.
Snapshots of amplitudes of probe vector potential
g (top), developing from a short seed, and corresponding density
modulations h (bottom) where g0
is the small-signal growth rate and hlim is the limiting
value of h.