Enhancement of the switched phase conjugate reflectivity in a BaTiO3 crystal

We experimentally investigated the response of the photorefractive phase conjugation to a pulsed reading beam in an undoped BaTiO₃ crystal with a four-wave mixing geometry. A single longitudinal-mode Ar⁺ laser was used as a light source. The reading beam with a pulse width of ～1 s was switched on after writing a steady-state grating in the crystal by two recording beams under a suitable condition and the generated phase conjugation was measured. The phase conjugate output was found to be increased by some factors of magnitude over the initial value for a given peak power and period of the reading pulses. A maximum of the enhanced reflectivity can be controlled by adjusting the interacting beam powers. An increase in the diffraction efficiency was also found with the same read-out process, which plays a key role to increase the phase conjugation as our knowledge.