SELF-FOCUSING AND RAMAN-SCATTERING OF LASER-PULSES IN TENUOUS PLASMAS

The propagation of laser pulses of intensity which is large enough for relativistic self-focusing to occur is strongly affected by Raman instabilities. Both large and small angle scattering are important. The latter is the most severe since it couples with relativistic self-focusing leading the pulses to acquire significant axial and transverse structure in a time of the order of the self-focusing time. This prevents smooth self-focused pulses propagation for distances longer than the Rayleigh length except for pulse duration of the order of the plasma period.