Brillouin scattering, two‐plasmon decay, and self‐focusing in underdense ultraviolet laser‐produced plasmas

Underdense foam targets were irradiated with a single UV laser beam at intensities up to 1015 W/cm2. The incident laser propagated into the foam a distance of 500–1000 μm, depending on the average target density. The backscattered Brillouin and 3ω0/2 radiation were observed to have the same dependence on the incident laser intensity, indicating a strong interrelation of these processes. A possible coupling mechanism is proposed.