Study On Growth And Spectrum Properties Of Lithium Niobate Doped With Magnesium And Erbium

Series of Mg:Er:LiNbO₃ crystals were grown by the Czochralski method. The growth and structure and the optical properties of the crystals were studied. Appropriate parameters (temperature gradient, pulling speed and rotating speed) are chosen during the crystal growth process to maintain the flat solid-liquid interface. The main purpose doping Mg in the crystals is important for increasing the pump light intensity in waveguide laser and amplifier made from Er:LiNbO₃.The infrared spectra indicates that the O-H absorption peak of Mg(6mol%): Er:LiNbO₃ crystal shifts to 3537cm-1 compared with that of other crystals doped with lower Mg concentration 3486cm-1,which indicates that Mg doping concentration of 6mol% is over the threshold. With the increase of Mg doping amount , the absorption edge in ultraviolet-visible absorption spectra of Mg:Er:LiNbO₃ crystal shifts to the violet. Using infrared spectra and absorption spectra, the location of Mg in doped LiNbO₃ crystals were confirmed, and the location model was given. Before the doped concentration of Mg achieves its threshold Mg takes anti-site Nb(NbLi),and when the doped concentration of Mg over its threshold, Mg enters NbNb and LiLi sites at the same time.The optical damage resistant properties were measured by facula-distortion method, it indicated that the optical damage resistant property of Mg:Er:LiNbO₃ crystals was more than two orders of magnitude higher than that of Er:LiNbO₃ crystal, it was superior to that of Er:LiNbO₃ crystal.The 550nm lifetime characteristics of Er: LiNbO₃ crystals codoped with MgO were measured. The 550nm lifetime of Mg:Er:LiNbO₃ crystals showed the inverse increase tendency with the increase of the doped contents of MgO below and above the MgO threshold values. More important, the lifetimes of Mg:Er:LiNbO₃ crystals sharply decreased when the contents of doped MgO exceeded the threshold values.