Study On Spatial Optical Limiting By Stimulated Brillouin Scattering

In the system of the high-power and high-energy laser, the research of optical limiter is very important for the protection of optical elements and the stability of system. Because the optical limiter in this system must have high damage threshold, the existing optical limiter can’t meet this demand. The damage of the Brillouin medium, which has the optical limiting effect, is up to 100GW/cm2 and will meet this demand. So this paper researches the spatial optical limiting of the SBS.First, according to the nonlinear wave equations and elastic wave equation, the couple-wave equations of the SBS, which describes the SBS process in the Brillouin medium, is derived. Because the SBS equations are partial differential equations and don’t have analytical solutions, they are numerically soluted on the method of backward difference-central difference-implicit difference. So the numerical simulation model of the 2D and 3D space SBS is established. This model is programmed with MATLAB, and the tools of this model based on MATLAB GUI is also realized.Then, according to the same parameters of the Brillouin medium, this paper researches the spatial Optical Limiting of the diffent pump laser by the SBS with the MATLAB tools of the SBS. It is innovationlly found that the optical limiting of the Brillouin medium will lose for the small beam radius of bump, because the transmitted light is obviously affected by the diffraction effect. It is also found that compared with spatial Gaussian bump, the spatial fourth-order super-Gaussian bump has the better effect of spatial optical limiting in the Brillouin medium, which has the better uniform distribution of the transverse section of transmitted light. In addition, the threshold of SBS for the FC-40 and CS2 in the 60 cm cell are calculated with the MATLAB tools of the SBS, and calculation results accord with the experimental results of Zhu Xuehua and Gong Huaping. So our numerical simulation model of the 3D space SBS is correct.At last, according to the same parameters of the pump laser, this paper researches the spatial Optical Limiting of the different medium paramter by the SBS with the MATLAB tools of the SBS. It is found that the spatial Optical Limiting effect of SBS can be controlled by the different parameter of Brillouin medium. It is found that the optical limiting effect of the Brillouin medium will lose for the too long cell, because the transmitted light is obviously affected by the diffraction effect.