Growth and characterization of Er-doped single crystal lithium niobate fibers

Single crystal lithium niobate fibers with diameters ranging from 1 to 3 mm have successfully been grown by the micro-pulling-down technique. The fibers are doped with various Er doping levels from 0 to 0.7 mol % and appear to be transparent and crack-free. The study includes x-ray structural investigation and complete spectroscopic characterization. The analysis shows a good homogeneity of composition, and the comparison with bulk crystals demonstrates the good optical quality of the samples. Particular attention has been devoted to the measurements of the fluorescence decay time of the 4I^13/2 Er level, which has been carried out with a particular technique in order to avoid radiation trapping effects. Results are in agreement with the literature both in the case of bulk crystals and of fibers. Reliable polarized emission cross section in the 1.5 um region are presented.