Effect of annealing in Li-rich ambient on the optical absorption and crystallinity of Er doped LiNbO₃ crystals

Abstract

The crystalline perfection of Er doped LiNbO₃ crystals in near stoichiometric (SLN:Er) and congruent (CLN:Er) form was studied. Er doped (0.25, 0.5 and 1.0 mol. % Er₂O₃) CLN:Er crystals were grown by Czochralski technique from congruent melt composition. CLN:Er wafers were annealed in Li rich ambient (Vapor transport equilibrium; VTE) at 1100 °C for 100 h to prepare near SLN:Er doped crystal. Optical absorbance studies confirmed an increase in Li content of near SLN:Er crystals. Absorption spectra also shows narrowing of absorption peak linewidth for near SLN:Er crystals. High resolution X-ray diffraction (HRXRD) studies revealed single sharp diffraction peak with a FWHM of 21arc-sec for undoped crystal in comparison to relatively broad 70 arc-secs for as grown CLN:Er and near SLN:Er (annealed) crystal. Near SLN:Er shows an increase in diffraction peak intensity due to annealing induced reduction in Li-vacancies and disorderness of the structure. FT-IR spectra reveals elimination the H⁺ defects from the near SLN:Er crystals due to annealing.