PHOTOREFRACTION RESISTANCE OF NA2O-DOPED LITHIUM-NIOBATE SINGLE-CRYSTALS

Na-2 O-doped (up to 3 mol% Na in the melt) LiNbO3 crystals have been g rown by the Czochraski method. The experimental results show that Na2O dopants can increase the ability of LiNbO3 to resist light-induced op tical damage, but the photorefraction of LiNbO3:Na(3 mol%) is larger t han that of LiNbO3:Na(1 mol%) and the absorption edge of the former cr ystal has a longer wavelength compared with that of the latter. These two abnormal phenomena were interpreted as that some ilmenite structur e (NaNbO3) regions are formed in doped LiNbO3 crystals with the increa sing dopant concentration of Na2O.