| In photorefractive crystal light illumination changes the refractive index of the crystal due to linear electrooptical effect,which in turn changes the light distribution. As a result of the development of this process,a beam,called the phase conjugation wave,leaves the crystal back along the direction of the incident beam and is its phase conjugate replica. This feature makes it possible for photorefractive phase conjugator to find applications in many fields where the wavefront-reversing properties are required. For example,phase-conjugating mirrors (PCM) which applied to double-pass solid-state MOPA system can be used to overcome the problem that the quality of the beam delivered by the oscillator is often corrupted by thermally induced aberration in the amplifier,especially in solid-state laser systems.This thesis analyzed the physical mechanism of the self-pumped phase conjugation(SPPC) changing from a stimulated backscattering and four-wave-mixing(SPB-FWM) mechanism to a totally internal reflecting(TIR) mechanism with the different pump wavelengths and the doping concentrations. Based on analysis and research,many experiments were done. They include:(1) Self-pumped phase conjugation(SPPC) in Ce:BaTiO3 with 532nm nanosecond pulse operated at either a 1- or 10-Hz repetition rate. (2) SPPC operated in Ce:BaTiO3 with 532nm continuous wave,especially concentrated on the self-pulsation phenomenon. (3) SPPC operated in Ce:BaTi03 with 790nm continuous wave,especially concentrated on the different grating decay between TIR and SPB-FWM.(4) SPPC operated in 632.8nm continuous wave,especially concentrated on comparing the experiment results with the theoretical results. Unique and valuable results have beenachieved as follows:1. Through math modal,the relation between the phase conjugation reflective of Ce.'BaTiOs and incident angle,incident position were calculated. Experiment results are quite accordance with theoretical calculations.2. We advance,for the first time to our knowledge,that efficient self-pumped phase conjugation performed with an CeiBaTiOa crystal with low repetition (lHz-10Hz) nanosecond pulses from a Q-switched Nd:YAG laser. Phase conjugation reflectivity as high as 21.5% were obtained at an incident angle of 50 .3. Grating decay time of photorefractive crystal is important for low-repetition-rate pulse applications and memory applications. In our experiments every time after the phase conjugate reflectivity reached its steady-state value,we turned off the incident beam for a certain time (placing the crystal in a dark room). Then we turned in the input laser to observe the decline of phase conjugate reflectivity. Measuring dark storage time,we found that the phase conjugate reflectivity declined to 50% of steady-state value when photorefractive crystal was in dark condition for 30 minutes. Even after 9 hours,there still existed remaining reflectivity,which couldn't be measured by our detector.4. When SPPC operated in Ce:BaTiO3 with 532nm continuous wave,the phase conjugate reflectivity was measured as a function of incident angle,incident spot dimension,incident position in the crystal and incident power. A maximum reflecting of 53.8% was obtained. Furthermore we advanced,for the first time to our knowledge,which the self-pulsation of phase conjugation wave was related to the incident power intensity. Through calculation we concluded that the phase conjugation was instable when the incident power density ranged in 700-1240mW/cm2.5. Experiment about researches on SPPC totally internal reflection mechanism were done when Ce:BaTiO3 is performed in CW titanium laser at 790nm wavelength. We compared the grating decay of TIR mechanism with that of SPB-FWM mechanism.
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