| This thesis studies coherent Rayleigh-Brillouin scattering (CRBS) experimentally and theoretically. The power spectrum of CRBS in gases in the kinetic regime is observed for the first time. Theoretical and numerical studies on CRBS based on electromagnetic and kinetic theories are presented. The theoretical results match the experimental data satisfactorily.; The first chapter reviews the related literature and locates CRBS in the broad areas of nonlinear optics and gas dynamics. The physics of CRBS is explained in the second chapter. Two crossing pump laser beams generate a gas density perturbation; A probe laser beam is then coherently scattered from the perturbation. Details of the experiment and the data reduction are described.; A theoretical model of CRBS for atomic gases is developed in Chapter 3. Based on a kinetic equation with the linearized Bhatnagar-Gross-Krook collision term, the model gives analytical expressions for the CRBS line shape and gasdynamic quantities. The theoretical line shape compares favorably with the observation in argon and krypton. The internal energy modes of molecular gases are considered in a model developed in Chapter 4. The model is based on the linearized Wang-Chang-Uhlenbeck equation. Comparison of the model with experimental data in nitrogen, oxygen, carbon dioxide, as well as atomic gases is discussed.; Several topics are discussed in Chapter 5. A nonlinear power narrowing phenomenon of CRBS line shape, due to intensive pumping, is predicted. Different phase matching schemes are discussed and illustrated from an experimental perspective. CRBS represents a new laser diagnostic technique. It has the ability to perform localized, high signal-to-noise ratio measurements of gas parameters. This is demonstrated by CRBS-based temperature measurements in a weakly ionized plasma. Finally, we summarize this thesis work and discuss the implications of CRBS on kinetic theory and photon-matter interactions, which are the subjects of future work. |
