Effect of doping ions on congruent LiNbO3 single-crystal fibers

Er3+-doped LiNbO3:MgO single crystal fibers with a diameter of 1 mm were gr own using the micro-pulling-down method. The transmission and the luminesce nce spectra. from the Er3+ ions in these materials were investigated togeth er with the luminescence decay. Transmission lines were observed, which wer e assumed to be due to the Er3+ ions with various site symmetries. Excitati on with 514.5-nm radiation caused luminescence bands to appear at 526-, 551 -, 660-, and 1530-nm. The 551-nm luminescence due to the S-4(3/2)--> I-4(15 /2) transition was found to have a decay time of about 100 mu sec. Also, th e effective segregation coefficients of Er and Mg in LiNbO3 were found to b e about 1.02 and 0.86, respectively, at a growth rate of 0.5 mm/min.