CHARACTERIZATION OF STIMULATED BRILLOUIN SCATTERING

Abstract

Stimulated Brillouin scattering has been well investigated in a varety of materials. Stimulated Brillouin scattering, this originates from the χ3 nonlinearity of the medium especially related to acoustic phonon interaction. Now days studies are going on the field of stimulated Brillouin scattering for many applications. In my work I have analysed the properties of stimulated Brillouin scattering in different materials such as Acetone, Xylene, methanol, methyl acetate and demineralised water. Threshold laser power for stimulated Brillouin scattering emission is different for all the above materials. The samples prepared by adding dyes such as methylene blue, Rhodamine 6G and Rhodamine B to the above materials having threshold power greater than the pure material. The threshold power in some dyes in the above materials and for all the concentration have the same threshold power for some dyes in the above materials the threshold power is decreasing as the concentration decreases. For methanol and acetone there have change in wavelength of scattered wave with different dyes at different concentrations and for methyl acetate and demineralised water the wavelength is remains constant for all the concentrations of the dyes. For all the materials with all the dyes at all the concentrations `the amplitude scattered wave is increasing with the laser power. This is due to the increased phonon generation at the higher power due to the reduced radiative effect. In some dyes in the above materials as the concentration increases the amplitude of the scattered wave decreases due to the increased molecular interaction. In some dyes at some particular points of concentration the amplitude increases with concentration. There has no stimulated Brillouin scattering is observed from xylene since it is not optically polarisable. From the work methyl acetate is found to be the good medium to have stimulated Brillouin scattering with all the dyes at all the concentrations. We can use this methyl acetate for the study of phase conjugation and its properties Optical phase conjugation has got variety of application in now days. Optical phase conjugation can be created by forward mixing and stimulated scattering. If the phase conjugation is created by the stimulated scattering the properties of phase conjugation can be controlled by the medium properties since it is active process and it has got an energy transfer between medium and the photon. The work can be extended to study symmetry of a solid system by analysing the photon – phonon interaction in solids because the photon - phonon interaction is depend on the symmetry of the system.