Observations of transition to strongly coupled stimulated Brillouin scattering in laser-plasma interactions

Observation of ion acoustic waves associated with plasma-induced incoherence of laser beams using Thomson scattering

We have carried out experiments to investigate the physical processes responsible for the recently discovered phenomenon of plasma-induced incoherence (PII) of a laser beam. Using a Thomson scattering diagnostic, we have observed ion acoustic waves (IAW) having wave vectors transverse to the interaction beam spectral and temporal characteristics of which show a clear correlation with other signatures of PII for various conditions of plasma density and laser intensity. These results support the recent theoretical interpretation for which the IAW result from the coupling between forward stimulated Brillouin scattering and self-focusing of the laser light in PII mechanisms.