Optical characteristics of Er3+ ion in Er/Yb:LiNbO3 crystal: Comparison with the dissimilar effect of anti-photorefractive ions Zn2+, In3+ and Zr4+

The different influences of Zn2+, In3+ and Zr4+ ions on the optical characteristics of Er3+ ion in Er/Yb:LiNbO3 crystals were discussed. An enhanced 1.54 mu m emission was observed for Zr/Er/Yb:LiNbO3 crystal, but the Zn2+ tri-doping resulted in a decreased one, and the intensity of 1.54 mu m emission remained about same in In/Er/Yb:LiNbO3 crystal. The populations of the green emitting S-4(3/2)/H-2(11/2) states were achieved through the three-, two- and two-phonon processes in Zn/Er/Yb:LiNbO3, In/Er/Yb:LiNbO3 and Zr/Er/Yb:LiNbO3 crystals, respectively. Zn2+ and In3+ ions affected the optical characteristics of Er3+ ion via modifying the Er3+ ion occupancy in Er/Yb:LiNbO3 crystal. The formation of Er-Li(2+)-Er-Nb(2-) ion pairs caused by the Zn2+ and In3+ ions could increase the rate of cross relaxation process. The OH- absorption spectra showed that the incorporation of Zr4+ ions increased OH- content, which increased the probability of the nonradiative relaxation process of I-4(11/2)-> I-4(13/2) (Er) in Zr/Er/Yb:LiNbO3 crystal. The J-O intensity parameters Omega(t) (t=2, 4 and 6), the radiative lifetime (tau(rad)) and fluorescence branching ratio (beta) in Zr/Er/Yb:LiNbO3 crystal were predicted by Judd-Ofelt theory. Fuchtbauer-Ladenburg and McCumber methods were carried out to calculate the emission cross-sections at 1.54 mu m emission. The gain cross-section, estimated as a function of the population inversion ratio, allowed us to evaluate a potential laser performance of Zr/Er/Yb:LiNbO3 crystal. (C) 2013 Elsevier Ltd. All rights reserved.