The Numerical Simulation Of Transverse Stimulated Brillouin Scattering

Transverse stimulated Brillouin scattering (TSBS) in large optics has been paid more and more attention in recent years with the gradual improvement of laser's energy density and power. This article mainly discusses the characteristics and induced damage mechanisms of TSBS in large optics, as well as the suppression of TSBS due to finite laser bandwidth by the way of numerical simulations.First the theoretical models of TSBS initiated by seeded light and by distributed noise respectively have been raised based on the nonlinear coupling wave equations. Then the equations are solved in numerical methods, the space and time distributions of optical and acoustical waves under different conditions are derived, and the difference of these two models are analyzed from these numerical simulation results. Last the model of broadband pumped TSBS has been created and the corresponding numerical simulations are presented.The investigation shows that TSBS can be induced easily in large optics exposed to high intensity laser. When the pump laser intensity is sufficiently high and the transverse scale of optics is sufficiently long, the strength of the elastic acoustic waves may surpass materials' yielding ability and induce mechanical damage. The space distributions of optical and acoustical waves of TSBS process manifest the feature of focusing and that feature becomes more and more remarkable with the evolution of TSBS from strong transient case to steady-state case. Besides possible mechanical damages, TSBS may also bring significant loss of transmitted energy of optics. For the TSBS, even small amounts of laser bandwidth lead to enough reduction in the SBS gain to decrease the energy loss and avoid possible mechanical damage.