Plasma Wave Seed for Raman Amplifiers

TL;DR

This paper proposes replacing laser seeds with plasma wave seeds in backward Raman amplifiers, enabling similar pulse outputs and benefits like chirping without complex seed preparation or synchronization.

Contribution

It introduces a novel plasma wave seed method for Raman amplifiers that replicates laser seed effects in both linear and nonlinear regimes.

Findings

Plasma wave seeds can produce the same output as laser seeds in linear regime.

Numerical simulations show plasma wave seeds approach the same attractor solutions as laser seeds in nonlinear regime.

Chirping plasma wave wavelengths mimics the effects of seed wave frequency chirping.

Abstract

It is proposed to replace the traditional counterpropagating laser seed in backward Raman amplifiers with a plasma wave seed. In the linear regime, namely, for a constant pump amplitude, a plasma wave seed may be found by construction that strictly produces the same output pulse as does a counterpropagating 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 effects as chirping the seed wave frequency. This methodology is attractive because it avoids issues in preparing and synchronizing a frequency-shifted laser seed.