Abstract: It is proposed to replace the traditional
counter-propagating laser seed in backward Raman amplifiers with a
plasma wave seed. In the linear regime, namely for constant pump
amplitude, a plasma wave seed may be found by construction that
strictly produces the same output pulse as does a
counter-propagating laser seed. In the nonlinear regime, or
pump-depletion regime, the plasma-wave initiated output pulse can be
shown numerically to approach the same self-similar attractor
solution for the corresponding laser seed. In addition, chirping the
plasma wave wavelength can produce the same beneficial eects as
chirping the seed wave frequency. This methodology is attractive
because it avoids issues in preparing and synchronizing a
frequency-shifted laser seed.