  We propose to amplify and compress an ultrashort Light Spring laser seed with
a long Gaussian-shaped laser pump through Raman amplification. This Light
Spring, which has a helical spatio-temporal intensity profile, can be built on
the superposition of three distinct laser frequency components. In order to get
an independent frequency amplification, two criteria are established. Besides
these criteria, a non equal frequency separation is necessary to avoid
resonance overlapping when three or more frequencies are involved. The
independent set of equations, which describes the wave-wave interaction in a
plasma, is solved numerically for two different Light Spring configurations. In
both cases, the amplification and transversal compression of the seed laser
pulse have been observed, with a final profile similar to that of the usual
Gaussian-shaped seed pulses. In addition, two different kinds of helical plasma
waves are excited.
