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Yb doped Lu₃Al₅O₁₂ single crystal fibers has been grown with various Yb³⁺ ion concentrations: 2%, 5%, 10%, 15%, and 50% Yb doping levels. The diameter of the fibers is around 3  mm and their length is up to 110  mm. The fibers have been annealed in air at 1400  °C for 24  h to remove Yb²⁺ produced during the growth in the fibers. Structural characterization by x-ray diffraction method has been performed to confirm the monocrystalline phase and the orientation of the fibers. Absorption measurements have been performed on different pieces of the fibers to check the homogeneity of the distribution of Yb³⁺ along the fiber length. The results indicate that the distribution coefficient is close to 1. The fluorescence lifetime was measured for different Yb³⁺ concentrations. Results are in agreement with the literature and can be interpreted as a mixture of the radiation trapping and concentration quenching effects. The emission cross section has been calculated both from absorption spectra and from emission data. The two different independent methods give similar results, but emission data suffer from strong reabsorption effects on some of the lines. On the zero phonon line at high doping levels a central dip appears that can be interpreted with a reabsorption model. ©2008 American Institute of Physics

Contents

• INTRODUCTION
• CRYSTAL GROWTH
• CHARACTERIZATION: EXPERIMENTAL SETUP
• CHARACTERIZATION: RESULTS AND DISCUSSION
  • A.Structural analysis and absorption characterization
  • B.Yb³⁺ decay time measurements
  • C.Fluorescence measurements
  • D.Conclusion
• ACKNOWLEDGMENTS
• REFERENCES
• FIGURES
• FOOTNOTES