SHG CHARACTERISTIC OF Co-DOPED LiNbO3 SINGLE CRYSTAL

In order to investigate the doping effect of LiNbO3 by cobalt ion, LiNbO3 single crystals doped with CoO, 0.02, 0.05, 0.2, and 1 mol% were synthesized. SHG characteristics were measured using CW YAG:Nd laser in the temperature range from 120 to 310 K. Optical absorption measurements were carried out in the wavelength between 300 and 1800 nm in the y direction. The largest conversion efficiency of SHG was observed in the 0.02 mol% doped crystal, which is due to harmonic effect. Microscopic observation of domain structure was also carried out. It is found that the domain layers of positive and negative orientation lie on top of another in the direction of the c axis, the thickness of which is of the order of microns. SHG intensity is discussed based on the relation between laser beam diameter and the thickness of domain layers.