Bismuth-doped soda alumino germanate glass part I: examination of the role of Na/Al atomic ratio on glass matrix and bismuth luminescence properties in the 300-900 nm spectral range

Abstract

A significant shift in luminescence spectra of bismuth-containing glasses was investigated for a range of non-bridging oxygen (NBO) containing glasses following excitation between 248-375 nm. Emission behavior variation for glasses was evaluated as a function of alkali to aluminum ratio which is known to vary the concentration of NBO thereby imparting locally different environments for multivalent dopant Bi ions. We report that the structural variation imparted by NBO variation significantly impacted the emission features of both the undoped base glass matrix as well as glasses containing Bi where emission features could be directly ascribed to defects within glasses and the changing Bi valence states. A significant shift in the luminescence spectra (out to 900 nm) between NBO containing and deficient undoped and bismuth doped glasses to shorter wavelengths was seen to occur. This was attributed to the differing defects which form in the two classes of glass matrices as well as a tightening of the glass structure as the Na/Al ratio was decreased. Specifically, we show that an NBO containing environment leads to red shifted absorption edges along with stabilization and emission from Bi2+ (615 nm) and Bi0 (810 nm) while NBO deficient environments enable stabilization and emission from Bi2+ centered at 750-795 nm. A transition in the luminescence and excitation spectra was seen to occur with increasing bismuth concentration in two different matrices containing NBOs when excited with 248 and 325 nm, respectively. These results show promise in leveraging the host glass matrix to directly influence the luminescence properties of the dopant.