Influences of optical breakdown on stimulated Brillouin scattering

Abstract

Avalanche ionization model is introduced to the coupled stimulated Brillouin scattering (SBS) equations. Numerical simulation of SBS energy reflectivity as a function of pump intensity is made with and without the optical breakdown factor in the equations. In the experiment, purified and unpurified CCl４ media are studied with an Nd:YAG laser system with Q switch, the results are found to agree well with the numerical solutions. It is observed that under conditions that the optical breakdown does not occur, the energy reflectivity increases nonlinearly with pump intensity until reaching a certain value above which it tends to grow slowly. In cases with the breakdown, the energy reflectivity first increases nonlinearly with the pump intensity to a peak value and then decreases dramatically as optical breakdown occurs. The stability of energy reflectivity in the cases without optical breakdown is obviously better than cases otherwise.

Spectrum evolutions of spontaneous and pump-depleted stimulated Brillouin scatterings in liquid media

“…5. Here the decrease and the instability of SBS energy reflectivity caused by optical breakdown [15,16] may be used to explain the reduced intensity and the spectral fluctuation. In addition, we find that the serious modulation appeared in SBS temporal waveshape after the breakdown occurred.…”

“…Therefore, in SBS experiments, the optical breakdown should be avoided as much as possible by using appropriate methods such as medium purification. [16] Because the optical breakdown is not included in the above model, the spectrum shown in Fig. 5 cannot be numerically simulated.…”