Effect of doping ions on congruent LiNbO₃ single-crystal fibers

Er³⁺-doped LiNbO₃:MgO single crystal fibers with a diameter of 1 mm were grown using the micro-pulling-down method. The transmission and the luminescence spectra from the Er³⁺ ions in these materials were investigated together with the luminescence decay. Transmission lines were observed, which were assumed to be due to the Er³⁺ ions with various site symmetries. Excitation with 514.5-nm radiation caused luminescence bands to appear at 526-, 551-, 660-, and 1530-nm. The 551-nm luminescence due to the ⁴S_3/2→⁴I_15/2 transition was found to have a decay time of about 100 μsec. Also, the effective segregation coefficients of Er and Mg in LiNbO₃ were found to be about 1.02 and 0.86, respectively, at a growth rate of 0.5 mm/min.