Effect of heating on spectral characteristics of Er-doped laser glasses

The absorption and fluorescence spectra of Er-doped phosphate and silicate laser glasses were investigated in a temperature range of 20-300 degrees C. On heating, the differential spectra demonstrated variations of spectral profiles. The effects of heating for silicate and phosphate glasses are similar. The contours of the absorption and luminescence bands varied nonmonotonically with the temperature. These variations were explained by a redistribution of the populations of the Stark sublevels of the I-4(15/2) ground and the I-4(13/2) excited terms. The heating resulted in 5-10% decrease of oscillator strengths of spectral bands. On the base of temperature variations of spectral profiles we proposed an energy levels model, which allowed to explain the thermal variation of spectrum of EI-doped laser at 1.54 mu m. According to this model, the transitions in two range of lasing (1534 and 1542 Mm) come from two Stark sublevels of the I-4(13/2) excited manifold to two sublevels of the I-4(15/2) ground manifold. The effective energy gaps between neighbouring Stark components are equal to 50 cm(-1) and 100 cm(-1) for the I-4(13/2) and the I-4(15/2) states, respectively.