Homogeneous linewidth measurements of Yb3+ ions in congruent and stoichiometric lithium niobate crystals

We report the result of a series of pump{probe spectral hole burning measurements on Yb 3+ doped stoichiometric and congruent lithium niobate single crystal. The measurements were performed with a stabilized diode laser tuned to the 980 nm transition of the dopant ions. The crystal samples were placed in a closed cycle helium cryostat, the experiments have been done in the temperature range 9{20 K. The observed spectral holes have complex structure, at least two Lorentzian curves are needed to reproduce their shape (double spectral hole). A simple theoretical model has been developed to describe the line-shape resulting from the interaction between the light pulses and the dopant ions. Using the predictions of the theory, the homogeneous linewidths and the population relaxation rates have been estimated for both crystal samples. Using these results, the temperature dependence of the spectral hole widths and the spectral diusion rates have also been determined. Some considerations are presented to explain the origin of the double spectral hole structure.