Ultrafast Stimulated Scattering

Several novel stimulated scattering mechanisms are investigated. These studies are aimed at developing new techniques to efficiently excite the stimulated scattering of ultrashort optical pulses. To develop a convenient source of ultrashort optical pulses, novel techniques for mode-locking solid state lasers are explored. These techniques include mode-locking using a reverse saturable absorber, as well as pulse shortening using a linear cavity coupled to the main oscillator cavity. Using these techniques, pulses as short as 9 ps and 2 ps have been generated from a pulsed Nd:YAG and alexandrite laser, respectively. Vector phase conjugation, the simultaneous conjugation of both the phase and polarization of the incidence wave, is demonstrated by stimulated Rayleigh-wing scattering (SRWS). The 2 ps response time of SRWS allows efficient phase conjugation of the 30 ps optical pulses. Stimulated Rayleigh-wing scattering is used to remove distortions in both the phase and polarization of the incident wave. Stimulated Brillouin scattering of chirped optical pulses is shown using a cumulative pulse technique. When the separation of several short optical pulses is shorter in duration than the phonon lifetime of the Brillouin active medium, each pulse will contribute to the effective phonon field. The technique is demonstrated using chirped optical pulses. It is formed that not only does the SBS process return an efficient scattered wave, but it replicates the linear chirp of the input wave. The scattered wave is compressed to a duration of less than 8 ps using a dispersive grating pair. The interaction between stimulated Rayleigh-wing scattering and stimulated librational scattering is also examined. It is found that these two processes can compete through the process of self-focusing. A theoretical model is developed to describe this interaction, and the model agrees with the experimental observations.