Optical phase conjugation in pure and Fe doped LiNbO3

The time evolution of a phase grating was studied. The studies were carried out using pure LiNbO₃ and a Fe-doped samples. The formation and erasure times of the phase grating and the phase conjugate signal were measured using a 488-nm wavelength with the pump beams of power 8 mW and a probe beam of power 1.2 mW. In the Fe-doped crystal, the formation and decay of the phase grating follow a near exponential pattern. The phase conjugate signal also behaves similarly with a formation time of 840 s and a decay time of 1200 s. In pure LiNbO ₃ crystal, though the decay of the phase grating follows the exponential form, with a decay time of 2000 s, the formation of the phase grating was observed to follow a different pattern. After a gradual increase in the diffraction efficiency in the first 600 s, there was a fall during the next 200 s and an increase thereafter and subsequent fall