A numerical study of transient stimulated Brillouin scattering and coherent beam combination

Stimulated Brillouin scattering (SBS) beam combination, transient SBS and optical phase conjugation by SBS in an optical waveguide were studied theoretically in this dissertation via numerical simulations. Efficient numerical algorithms were developed and implemented for the above physical processes.; Beam combination by SBS involves two pump beams interacting in a common SBS medium. When the two partially overlapped laser beams are incident on a Brillouin active medium, two backward propagated, partially coherent Stokes beams are generated. A mutual coherence function can be statistically defined and computed to measure the coherency between the two Stokes beams. In our numerical simulation for the mutual coherence function computations, we found that the degree of coherency is dependent on the degree of overlap of the two pump beams, the acoustic phonon lifetime and the pump pulse width.; Transient single beam SBS processes, ignoring transverse field variations, was studied numerically via an efficient non-iterative algorithm. The study observed transient decaying oscillations in the pump and Stokes output intensities. The period of these oscillations was found to be directly proportional to the process interaction time defined by the product of the medium phonon lifetime, the SBS cell length, the SBS coupling gain coefficients and the depleted pump intensity. A perturbation analysis is performed analytically which confirmed the numerical results.; Transient, optical phase-conjugation by SBS in an optical waveguide involves consideration of transverse field variations. Efficient numerical algorithms were developed which solve the 2D (one transverse, one longitudinal), transient, coupled, partial differential-integral equations. Transient conjugation fidelity and reflectivity were computed with a CRAY C-90 super computer. The results show transient oscillations in reflectivity measurements being consistent with that observed in the 1D transient SBS processes and a quick buildup of phase conjugation fidelity indicating phase locking of the Stokes phases to that of the pump laser. The progress of the buildup of conjugation fidelity is followed through strong transient regime to the steady state.; These studies are known to be the first successful and efficient studies for the above non-linear optical processes in the transient regime.