Research On Characteristics And Applications Of Ce:BaTiO₃ Self-pumped Phase Conjugator

Photorefractive phase conjugation, which is one of the most important methods for producing phase conjugation wave, is of potential use in many fields due to its low build-up threshold, high fidelity and high damage threshold, etc. In this thesis, we present a complete research to the characteristics and applications of Ce:BaTi03 self-pumped phase conjugation (SPPC).Characteristics of Ce:BaTiO3 self-pumped phase conjugation are studied through abundant experiments. The efficient SPPC had been performed with 1-Hz-repetition-rate 532nm nanosecond pulses, in which phase conjugate reflectivity as high as 21.5% was obtained. When SPPC were operated in Ce:BaTiO3 with 532nm, 632.8nm and 790nm CW lasers, the maximum SPPC reflectivity of 54.1%, 88.2% and 80.5% were obtained, respectively. Unlike the results reported before that four-wave mixing by stimulated photorefractive backscattering (SPB-FWM) only exists at short wavelengths while four-wave mixing by total internal reflection (TIR-FWM) only exists at long wavelengths, both of these two mechanisms coexist at all wavelengths from 532nm to 790nm in our experiments. Experimental results are reported on temporal instability of phase-conjugate beam in a self-pumped Ce:BaTiO3 phase conjugator at 532nm.Dark decay behaviors of SPPC gratings in Ce:BaTiO3 are studied, for the first time to our knowledge, by measuring the decay of SPPC reflectivities at 532nm and 790nm wavelengths at room temperature. SPPC grating at 790nm mainly attributes to the charge grating in Ce-ion deep trap while the Fe-ion deep trap contributes more at 532nm wavelength than that at 790nm. SPB-FWM forms the charge grating in Fe-ion deep trap, while TIR-FWM builds up the charge grating in the Ce-ion deep trap. We present a charge-transport model of the photorefractive effect with two deep traps (two deep-trap model) based on one deep-trap model and shallow-deep-trap model. We also found dark decay behaviors which accord with the two deep-trap model in the two-beam interference experiments. The fast decay-time constant of the space-charge field is obtained as 714s. The effects of multi-grating diffraction result in enhancement of the diffraction efficiency in two-beam interference experiments.With self-pumped phase-conjugate external cavity of Ce:BaTiO3 for the CW Ti: sapphire laser, the frequency shift of the laser output due to the self-scanning effect was observed, which approve the possibility of the self-scanning tunable method. The laser threshold decreases from 4.7W (without external cavity) to 3.6W (with externalcavity).With the cavity of output from zero-order diffractive beam applying to solid-state pyrromethene 567(P567), tunable range of about 70nm from 543-610nm, the largest range reported as we know, had been achieved. And the highest slope efficiency of 17.2% was obtained at 583nm wavelength. We propose and analyze an experimental scheme for studying the self-scanning effects of Ce:BaTiO3 phase conjugator. Then we propose a tunable experimental scheme for P567 laser output using self-scanning effect.