氧化还原处理对Mg:Ce:Cu:LiNbO_3晶体光折变性能的影响

INFLUENCE OF OXIDATION AND REDUCTION ON PHOTOREFRACTIVE PROPERTIES OF Mg:Ce:Cu:LiNbO_3 SINGLE CRYSTALS

在同成分铌酸锂(LiNbO3,LN)晶体中,掺入的摩尔分数分别为0,1%,3%,6%MgO,掺入0.1%(质量分数,下同)CuO和0.05%CeO2,采用提拉法生长了优质的Mg:Ce:Cu:LN晶体,对生长后的晶体极化后分别进行了氧化和还原处理。测定了Mg:Ce:Cu:LN晶体的紫外-可见光吸收光谱和光折变性能。结果表明:与未经氧化和还原处理的晶体相比,在掺MgO量为1%和3%时,经氧化处理的晶体的吸收边发生了紫移,经还原处理的晶体的吸收边发生了红移;而在掺MgO量为6%时,氧化处理后晶体的吸收边紫移趋势不明显。氧化处理后晶体的抗光损伤能力R减弱,而还原处理后晶体的R增强;而当掺入MgO为6%时,Mg:Ce:Cu:LN晶体的R最大,Mg:Ce:Cu:LN晶体的R比Ce:Cu:LN晶体高2个数量级。结合铌酸锂晶体的锂空位缺陷模型解释了有关实验结果。

Mg：Ce：Cu：LiNbO3 （Mg：Ce：Cu：LN） crystals doped with 0, 1%（in mole, the same below）, 3%, 6%MgO, and 0.10% （in mass, the same below） CeO2 and 0.05%CuO respectively were grown by the Czochralski method from congruent LN melting. After polarization, the crystals were oxidized and reduced. The ultraviolet-visible absorption spectra and the photorefractive properties of the three kinds of Mg＇Ce：Cu：LN crystals were measured. The experimental results that compared to grown crystals, when doped-Mg content of 1% and 3%, the absorption edge of oxidized crystals is shifted to the violet band and that of reduced crystals is shifted to the infrared band, and at doped-Mg content of 6%, the absorption edge of oxidized crystals exhibited a no clear violet shift. The optical damage resistance ability R of oxidized crystals decrease, and R of reduced crystals increase and R of reduced crystals doped with 6%Mg achieve maximum. The R of Mg：Ce：Cu：LN crystal is increased about 2 order of magnitude compared to that of Ce：Cu：LN crystal. Some related experimental results were explained based on Li-vacancy defect model.