Temporal characteristics of active stimulated Brillouin scattering optical limiting

Characteristics of transmitted temporal profile of active stimulated Brillouin scattering (SBS) optical limiting arc studied. Methods of impairing transmitted residual peak power and shortening the delay time of SBS are proposed. Based on coupled wave equations of SBS process, physical models of optical limiting based on active SBS are constructed. Using an implicit finite differencing in time and a downward differencing scheme in space, theoretical calculation models of active SBS limiting for numerical simulations are built up. Three parameters, i.e. residual peak power, delay time and limited power are defined renewably to characterize active SBS optical limiting. The relationship of transmitted temporal profile to seed peak power is obtained by numerical calculations. The influence of the injected seed power on transmitted residual peak power is analyzed in detail. It is shown that the residual peak power is weakened with strengthening of the seed power. By selecting suitable power of seed, residual peak is removed and consequently the ideal flat pulse output is achieved. On the basis of theoretical analysis, active SBS optical limiting temporal characteristics are examined experimentally with a 20 ns Nd:YLF laser and one nonlinear medium (CCl₄). The experimental results are compared with analytical and numerical calculations.