Geometrical constraints on plasma couplers for Raman compression

Abstract

Backward Raman compression in plasma is based on a 3-wave resonant interaction, which includes two counter-propagating laser pulses (pump and seed pulses) and an electron plasma wave (Langmuir wave). The resonant interaction can be ensured in nearly homogeneous plasmas. However, for high-power, large-aperture experiments, the homogeneous region becomes pancake-shaped and would likely be surrounded by thicker regions of inhomogeneous plasma. When these inhomogeneous plasma regions are extensive, significant inverse bremsstrahlung and seed dispersion may impede the compression effect. These deleterious effects may, however, be mitigated by chirping the seed and pump pulses.