Investigation of stimulated brillouin backscattering of nanosecond CO2 laser radiation from an extended underdense plasma

Thomson-Scattering Study of the Subharmonic Decay of Ion-Acoustic Waves Driven by the Brillouin Instability

“…Experiments carried out in the context of fusion [2] have reported limited levels of backscattering, less than 30%, which are much lower than the levels predicted by most theoretical models, which in some cases reach 100%. Nevertheless, such high levels have been measured under certain conditions [3]. The physical mechanisms responsible for the limited SBS reflectivity and for its saturation are not yet clear.…”

Thomson Scattering Measurements of Saturated Ion Waves in Laser Fusion Plasmas

“…The Thomson scattering spectra show saturated ion-wave amplitudes for intensities above 5 3 10 14 W cm 22 The stimulated Brillouin scattering (SBS) instability results from the parametric coupling of an intense incident light wave with an ion-acoustic wave to produce a reflected light wave. SBS can, in principle, reflect a large fraction of the incident energy (up to 100% reflectivity has been observed [1]) and therefore can have a large effect on the coupling of laser energy into targets. As one increases the incident laser energy above the SBS instability threshold, the growth of the SBS instability initially has an exponential dependence on laser intensity, but this growth is expected to saturate.…”

Greatly enhanced acoustic noise and the onset of stimulated Brillouin scattering

“…10-18. One of these 10 reported evidence of the convective finite-length threshold and two others 15,19 discussed the implications of data at high reflectivity for damping thresholds and for growth from noise. In experiments using ''short-wavelength'' lasers ͑those of wavelength р2 m͒, there have been many reports of the scaling of the ''SBS'' amplitude with the pump laser intensity, I pump , but there are no threshold results and no experiments which accessed the linear regime prior to 1993.…”