STUDY OF THE DIFFUSION FROM MELTED ERBIUM SALT AS THE SURFACE-MODIFYING TECHNIQUE FOR LOCALIZED ERBIUM DOPING INTO VARIOUS CUTS OF LITHIUM NIOBATE

摘要

The results of the localized doping of erbium into lithium niobate (LN), mainly via diffusion from melted erbium salt (TD - thermal diffusion), are presented. Two different temperatures, 350 and 600 ℃, as well as commonly used and specially cut LN wafers were applied. The samples were characterized by Rutherford Backscattering Spectroscopy (RBS) for the erbium concentration depth profiles and by Photoluminescence Spectroscopy for the emission around 1530 nm. The samples revealed thin erbium-doped layers that contained from 7 to 24 at. % of erbium. The luminescence without the post-diffusion annealing appeared in all of the LN cuts. As expected, when a higher temperature of TD was used, the luminescence intensity increased. However, the big differences in the luminescence intensity were found between the various LN cuts. A higher value of luminescence intensity was always detected in the Y_⊥ cut <10-14>, which is perpendicular to the crystal cleavage plain. To clarify the different penetration of the crystallographic orientation of LN for incoming erbium ions as well as the mechanism of the thermal diffusion process, the erbium site in the LN structure was studied using a combination of RBS/channeling and Neutron Depth Profiling (NDP) methods.