Study on the structure, mechanical properties, and 2-μm fluorescence of Ho 3+ -doped transparent TeO 2 -based glass–ceramics

Ho2O3-doped transparent tellurite glass–ceramics containing a metastable cubic crystalline phase were prepared. The structure, mechanical properties, 2-μm fluorescence, and decay times of the glass and glass–ceramics were investigated. The Judd–Ofelt intensity parameters, spontaneous radiative probability, and absorption and stimulated-emission cross-sections were calculated. After crystallization, the tellurium coordination number increased (3/3 + 1 → 4), which indicates that the structure changed substantially. The density, refractive index, and Knoop hardness of the glass–ceramics were enhanced compared with those of the precursor glass. After heat treatment, the spontaneous radiative probability and maximum stimulated emission cross-section increased to 172.24 s−1 and 0.744 × 10−20 cm2, respectively. Moreover, the 2-μm emission intensity of the glass–ceramic increased threefold under excitation by a 640-nm laser diode. The lifetime of the Ho3+:5I7 level in the transparent glass–ceramic was longer than that of precursor glass. The split in the absorption and emission bands and the reduction of the Ω2 parameter for the glass–ceramic confirmed the incorporation of Ho3+ ions into the crystalline phase. The results indicate that TeO2-based glass–ceramics are a promising candidate material for 2-μm lasers.