Manipulating Bi NIR emission by adjusting optical basicity, boron and aluminum coordination in borate laser glasses

Abstract

Bismuth‐doped (Bi) glasses and fibers have raised considerable attention for broadband emission and tunable fiber lasers in the near infrared (NIR) region. However, they suffer from low efficiency and it remains challenging to enhance Bi NIR emission. Here, we propose a facile way to enhance and tune the Bi NIR emission by adjusting optical basicity and modulating the boron and aluminum coordination in borate glasses. We find that BO4 and AlO5 species favor Bi NIR emission, right followed by the analyses of static emission spectra, the Fourier transform infrared (FT‐IR), and nuclear magnetic resonance (NMR) spectroscopy. Furthermore, abnormal Bi NIR luminescence phenomenon and boron anomaly were observed, which are attributed to the synthetic effect of B and Al coordination transformation. Besides, we find that BO4 tetrahedron plays a major role in enhancing Bi NIR emission at low Al content, while AlO5 hexahedron group will dominate at high Al concentration. Our investigation may give an insight into the luminescent behaviors of Bi in borate glasses and contribute to improving the performance of Bi‐doped fiber and fiber lasers in future.

Enhanced NIR photoemission from Bi‐doped aluminoborate glasses via topological tailoring of glass structure

“…Previous reports indicate that local glass structure, especially the coordination of Al species, plays a vital role in modulating Bi NIR emission, including emission intensity and decay behaviors . Therefore, fully understanding the local glass structure will help us to comprehend the mechanism for this highly improved Bi NIR emission.…”

“…Moreover, the fluorescent decay curves could be fitted to the second exponential decay function, which might also manifest that the Bi NIR emission stems from multiple Bi centers in boron‐germanate mixed glass systems or the same Bi centers within diverse surrounding environment. It is worthy to note that the lifetime of 1135 nm in boron‐germanate glasses is much longer than that in Bi‐doped borate glasses . The character of the relatively long lifetime is a significant advantage for the application of Bi fiber and optical devices in the future …”

“…The distinguishing feature for this method is the amorphous solid is formed by the continuous hardening (ie increase in viscosity) of the melt. Moreover, we choose this composition based on our previous work, where we realized optimal Bi NIR emission intensity in the composition by adjusting optical basicity, boron and aluminum coordination in borate glasses. Here, we want to further improve the optical properties of Bi‐activated glasses so as to favor the fabrication of Bi fibers in the future.…”

“…Bismuth (Bi) ‐functionalized glasses can realize such broadband emission in diverse multi‐component glass systems, ranging from silicate, phosphate, germanate, borate to chalcohalide glasses . Particularly, Bi‐doped aluminoborate glasses, with good moisture resistance, excellent fiberizing ability, and wide glass‐forming range, provide a potential strategy to reduce the volatilization of Bi and obtaining efficient Bi NIR emission at lower melting temperature, and thus are considered as potential host for Bi doping . However, so far, it remains challenging to prepare Bi‐doped borate glasses with good homogeneity and efficient NIR emission due to the lack of exploration in Bi‐related luminescent regularities .…”

Mixed alkali effects in Er3+‐doped borate glasses: Influence on physical, mechanical, and photoluminescence properties

“…8 By controlling the borate speciation, a variety of physical properties of glass can be engineered of density, viscosity, refractive index, chemical durability, atom diffusion, ionic and thermal conductivities, thermal expansion coefficient, microhardness, biocompatibility, and aggregation/chemical state of dopants etc. 3,[9][10][11][12][13][14] For examples, recently, a record-high resistance to crack damage was reported in a lithium aluminoborate glass, owing to the self-adaptive nature of the glass network through the transformation of nonring [BØ 3 ] to [BØ 4 ] − during densification. 3 Trigonal boron was found to be more favorable than tetrahedral one for promoting fast and effective ion exchange.…”