Effect of glass composition on the spectral and other properties of neodymium-doped borophosphate glasses

Abstract

Laser glasses of the system R2O(MO)—P2O5—B2O3—Ln2O3 (R = Li, Na, K; M = Ca, Sr, Ba; Ln2O3 = La2O3 + Nd2O3) at high Nd3+ concentrations of 1 ∙ 10^21 ions/cm3 were prepared. By using reactive atmosphere processing to remove hydroxyl groups, the infrared absorption coefficient at 3.5 μm due to OH- groups was below 1 cm^-1 . Absorption and fluorescence spectra, fluorescence lifetimes and thermal expansion coefficients were measured, and the stimulated emission cross-section for the 4F3/2 — 4I11/2 transition and the quantum efficiency were calculated. The results indicate that the borophosphate glass is possessed of a large stimulated emission cross-section, especially for alkali oxide containing borophosphate glass systems in which the stimulated emission cross-section is larger than 4.4 ∙ 10^-20 cm2 , and the effect of alkali and alkaline earth ions depends on the bonding strength between the cation and oxygen. The influence of B2O3 in borophosphate glasses on the fluorescence lifetime is much less than that in silicate glasses, and the quantum efficiency of borophosphate glasses, different from borate and borosilicate glasses, is high. The introduction of B2O3 strengthens the structure resulting in a lower thermal expansion coefficient and an excellent thermal shock resistance.