Spectral properties of Nd 3+ in aluminophosphate glasses

Abstract

The spectral properties of laser glasses in the system R 2O(MO)·Al 2O 2·Ln 2O 3·P 2O 5(R = Li, Na, K; M = Ca, Sr, Ba; Ln 2O 3 = Nd 2O 3 + La 2O 3), at a high Nd 3+ ion doping concentration of 1 × 10 21 ions/cm 3, were studied. Fe 2O 3 and other common transition metal oxide impurities were less than 10 ppm, and the absorption coefficient at 3.5 μm caused by OH − was below 1.0 cm −1 after removing the hydroxyl groups thoroughly by reactive atmosphere processing (RAP). Absorption and fluorescence spectra were measured at each composition. The effective linewidth was determined from the emission spectrum. The stimulated emission cross section for the 4 F 3 2 − 4 I 11 2 transition was calculated using the Judd-Ofelt model and the modified Deutschbein method. The results show that the influence of Al 2O 3 in phosphate glasses on fluorescence lifetime is much less than that in silicate glasses, and that both the fluorescence lifetime and the stimulated emission cross section decrease with increasing attraction between the alkali or alkaline-earth ions and oxygen. From the spectral and thermomechanical properties measured it is concluded that high Al 2O 3 containing aluminophosphate glasses with a high stimulated emission cross section of 3.3 × 10 −20 cm 2, a fluorescence lifetime of 180 μs at 10 21 Nd 3+ ions/cm 3 amd a thermal expansion coefficient of 80 × 10 −7 °C −1 can be obtained from these systems.