掺镁铌酸锂晶体抗光折变微观机理研究

研究了掺镁掺铁铌酸锂晶体的紫外，可见及红外光谱，首次发现当掺镁量超过通常所说的阈值（第一阀值）时，Fe^3 离子和部分Fe^2 离子的晶格占位由锂位变为铌位，但仍有部分Fe^2 离子留在锂位，晶体缺陷化学分析表明，继续增加掺镁量，占锂位的Fe^2 离子数瘵逐渐减小，当掺镁量达到另一个适当的值（第二阀值）时，全部Fe^2 都占铌位，晶体的抗光折变能力空前提高，这种现象称作双阀值效应。

SYUDY ON THE MICRO-MECHANISM OF MG-DOPED LITUIUM NIOBATE CRYSTALS AGAINST PHOTOREFRACTION

The ultraviolet-visible and infrared absorption spectra of Fe 2O 3 and MgO co-doped lithium niobate (LiNbO 3) crystals were studied. It was found that some Fe 2+ ions were still in Li-sites though Fe 3+ ions changed their site occupation from Li-sites to Nb-sites while the doping concentration of MgO was above the threshold (the first threshold). Defect chemical analysis shows that the amount of Fe 2+ ions will decrease as the doping concentration of Mg increases, and when the doping concentration reaches a suitable value (the second threshold) all Fe 2+ ions in Li-sites will diminish. It is expected that LiNbO 3 crystal doped with the second threshold will have an excellent ability to resist laser induced optical damage. This phenomenon is called as double thresholds effect.