Preparation and optical properties of HoF3–BaF2–AlF3–GeO2 glasses

New oxide fluoride glasses containing HoF3 was successfully prepared in the glass system of HoF3–BaF2–AlF3–GeO2 in which the maximum content of HoF3 reached approximately 50 mol% as the nominal composition. Glass transition temperatures, densities and refractive indices of the prepared glasses with various HoF3 contents were 572.3–614.4 °C, 4.45–6.45 × 103 kg m−3 and 1.58–1.68, respectively. Absorption and the fluorescence spectra were measured for the glasses with HoF3 contents of 10–50 mol%. The profiles of the absorption and the fluorescence spectra were influenced by the content of HoF3. Especially, the intensity ratio of the fluorescence spectra at 550 and 660 nm changed drastically with the contents of HoF3 in the glasses. The experimental results were analyzed in the frame of the Judd–Ofelt theory.