Photorefractive properties of Zn:Ce:Fe:LiNbO₃ crystals at abnormal temperature

Doped with 2%(in mole) Zn, 0.1% (in mass, the same below) Ce and 0.03% Fe and various mole ratios n(Li)/n(Nb) = 0.94, 1.10, 1.25, and 1.40 of LiNbO₃, Zn:Ce:Fe:LiNbO₃ crystals were grown by the Czochralski method. Using two wave coupling optical paths, the exponential gain coefficient of the crystals was measured. With n(Li)/n(Nb) increasing, the exponential gain coefficient of Zn:Ce:Fe:LiNbO₃ crystals increased. Using four wave mixing optical paths, the phase conjugate properties of the crystals were measured. As n(Li)/n(Nb) increasing, the phase conjugate reflectivity and response speed increase. The study of the temperature effect on Zn:Ce:Fe:LiNbO₃ crystals at 55, 70 °C and 110 °C find that the exponential gain coefficient and phase conjugate reflectivity increase, implied by the peak intensity increasing in exponential gain coefficient-temperature (Γ-T) curve and phase conjugate reflectivity- temperature (R-T) curve. The photorefractive properties of Zn:Ce:Fe:LiNbO₃ crystals at abnormal temperature is discussed based on the phase structure change.