| Popis: |
We present the dependence of the main spectroscopic properties of Ho:YAG on Ho doping contraction estimated at room temperature. Five Ho:YAG crystals with various Ho-doping concentrations were grown by Czochralski method: 0.34 at.% Ho/Y, 0.51 at.% Ho/Y, 0.90 at.% Ho/Y, 1.61 at.% Ho/Y, and 1.98 at.% Ho/Y. Detailed absorption spectra with high resolution were measured in the range from 185 up to 6500 nm. The emission spectra were measured in the range from 500 up to 3500 nm under excitation in UV (450 nm) and IR (1862 nm) range. The 5I7 upper-laser-level lifetime was measured using the confocal method. From the measured transmission data, the absorption cross-sections in all investigated spectral ranges were determined. Using the absorption spectrum data, the Judd-Ofelt analysis was performed to reach nett spontaneous radiative lifetime of the 5I7 level. Based on these data and measured fluorescence spectra, the emission cross-sections for 2.1 μm laser band were determined together with non-radiative relaxation rates. It was found that the Ho-doping concentration significantly influenced mainly the upper laser level lifetime, which drops from 7 ms for the lowest doping to 5.8 ms for the highly doped Ho:YAG sample. |
