Effect of composition on the thermal properties and spontaneous emission probabilities of Tm3+-doped TeO2–LiCl glass

The effect of composition on the thermal properties and the spontaneous emission probabilities of various 0.5 mol% Tm2O3 containing (1 − x)TeO2 + (x)LiCl glasses were investigated using differential thermal analysis (DTA) and ultraviolet–visible– near-infrared (UV/VIS/NIR) absorption measurements. DTA curves of the samples were obtained in the 23–600 °C temperature range with a heating rate of 10 °C/min. The value of the glass transition temperature Tg and the crystallization temperatureTc were found to vary with the glass composition. Melting was not observed for the glasses containing less than 50 mol% LiCl in this temperature range. However, a melting peak was observed at Tm = 401 °C for the glasses having higher than 50 mol% LiCl, which were also found to be moisture-sensitive. Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f−4f transitions of Tm3+ ions. Six absorption bands corresponding to the absorption of the 1G43F23F33F43H5, and 3H4 levels from the 3H6 ground level were observed. An integrated absorption cross section of each band, except that of 3H5 level, was found to vary with the glass composition. The role of the Judd–Ofelt parameters and therefore the effect of the glass composition on the radiative transition probabilities for the metastable levels of Tm3+ ions are discussed in detail.