Gain characteristics of steady-transient SBS and energy distribution of pulse width compression

Stimulated Brillouin scattering (SBS) is an effective method for obtaining high-brightness and high-beam-quality lasers. The research work on SBS has made great progress, but it is basically limited to the independent study of steady state and transient state, and there is a lack of ways to accurately characterize and predict the evolution law of SBS output characteristics in complete time range (from steady state to transient continuous change process). We use the concept of redundant gain Gf to quantitatively characterize the output characteristics of steady-transient SBS pulse compression process, and establish bidirectional mapping relationships of pump intensity and energy reflectivity, pump pulse width and compression ratio. The accurate prediction of the output characteristics of SBS under arbitrary conditions during the steady-transient continuous change process is realized, and it is verified experimentally. In addition, the evolution law of energy distribution in time domain in steady-transient SBS pulse compression is investigated by using the SBS frequency detuning effect. Essential differences in the compression mechanism and physical processes of steady-transient SBS are elucidated. The energy reflectivity of the whole system is nearly 40%, and the effective compression ratio is ~ 96.