Acoustic phonon dynamics in nanometric multilayers
This thesis presents an experimental and theoretical study of the acoustic phonon dynamics at the nanometric scale, by picosecond acoustic techniques and Raman scattering. We have studied the acoustic phonon (with frequencies in the GHz-THz range) transmission, generation and detection in superlattices and nanocavities made of semiconductor or dielectric oxyde materials. We have designed, optimized and characterized aperiodic phonon devices and coupled acoustic nanocavity systems. Finally, we have used the optical confinenment effects to enhance the coherent acoustic phonon generation and detection processes and to change the selection rules. In addition, we have developed models to computen the acoustic and optical responses of structures excited by ultrashort laser pulses, and to evaluate the Raman scattering cross section in nanometric multilayers.