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Bismuth (Bi)‐doped laser glasses with broadband emission are of current interest in the fields of sensing, bio‐imaging, and photonics. For practical applications, it must be considered how to improve the emission efficiency, in particular, for borate glasses with wide glass‐forming range, low melting point, and excellent fiberizing ability. Herein, we experimentally demonstrate that addition of GeO2 to aluminoborate glasses can effectively enhance Bi NIR emission by more than 300 times with prolonged decay time (~500 μs) and good homogeneity, which is, to our best knowledge, seldom achieved in Bi‐doped borate multi‐component glasses. The addition of second glass‐former GeO2, as revealed by detailed optical and structural analysis, leads to the facile regulation on local glass structure, forcing the conversion of aluminum species from AlO5 and AlO6 to AlO4 and consequently pushes the conversion of Bi3+ to Bi+ and Bi0 and stabilizes Bi NIR centers, which finally results in highly enhanced Bi NIR emission. We believe these results could contribute to designing Bi‐activated multi‐component laser glass and fibers with efficient NIR photoemission. [ABSTRACT FROM AUTHOR]

Nd3+‐doped phosphate laser glasses have been attracting much attention and widespread investigation due to their high solubility of rare earth (RE) ions, excellent spectroscopic properties, and large damage threshold. However, the narrow NIR emission bandwidth (less than 30 nm) of these Nd3+‐doped phosphate glasses limits their further application toward ultrahigh power field and efficient fiber laser in new region. Here, we demonstrate the broadening and enhancing of Nd3+NIR emission in laser glass of zinc aluminophosphate through tuning the glass structure and covalency of Nd‐O bond without limiting the radiative properties of Nd3+. The maximum bandwidth of 1.05 μm emission is broadened to 50 nm, which is comparable to that of Nd3+‐doped aluminate laser glasses. Simultaneously, the lifetime of 4F3/2 level is elongated nearly by two times. Structural and optical properties of prepared glasses were discussed systematically to reveal the mechanism. Detailed analysis on optical spectra and glass structure indicates that the bandwidth is affected by not only the covalency of Nd‐O but also the compactness of glass structure. Our results could enrich our understanding about the relationship between local glass structure and luminescence behaviors of active centers, and may be helpful in designing new RE‐doped laser glass systems. [ABSTRACT FROM AUTHOR]

Tantalum silicate glasses serve as laser host materials to take advantage of their high refractive index and the ability to tailor their physical properties in the design of high‐performance photonic and photoelectric components. However, successful attainment of feature control in tantalum‐doped materials remains a longstanding problem due to the limited understanding of local structure around the tantalum ions, a problem that lies at the heart of predicting the micro‐ and macroscopic properties of these glasses. Herein, we present a novel approach for predicting the local structural environments in tantalum silicate glass based on a phase diagram approach. The phase relations and glass formation region of Li2O–Ta2O5–SiO2 ternary systems are explored to calculate the structure and additive physical properties of lithium tantalum silicate glasses. These measured and calculated results are in good quantitative agreement, indicating that the phase diagram approach can be applied broadly to Li2O–Ta2O5–SiO2 ternary glass systems. Using the phase diagram approach, the local structure of tantalum can be directly obtained. Each Ta atom is surrounded by six atoms, and its polyhedron, the TaO6 octahedron, bonds through oxygen to Li and Ta. As a network modifier, Ta5+ depolymerizes the silicate glass structure by modulating the local structure of lithium atoms in Li2O–Ta2O5–SiO2 ternary glass system. The compositional dependence of structure in lithium tantalum silicate glasses is quantitatively determined based on the structure of the nearest neighbor congruent compound through the lever rule. These findings offer a precise prediction of tantalum silicate glass properties with quantitative control over local structural environment of the disordered materials. [ABSTRACT FROM AUTHOR]

Abstract: Because of ultra‐broadband near‐infrared (NIR) emission bismuth‐activated glasses and fibers offer a new promising platform for novel photonic devices such as new type of optical amplifiers and broadly tunable fiber lasers. Yet, challenge remains to manipulate the NIR emission behavior of bismuth (Bi) in photonic glasses for efficient Bismuth‐doped fiber and fiber lasers. Here, by engineering phosphorus and aluminum's topology, broadly tunable NIR emission has been realized in Bismuth‐doped phosphate laser glass. Structural and optical analyses on 27Al magic‐angle spinning nuclear magnetic resonance (MAS NMR), 31P MAS NMR, fourier transform infrared (FTIR) and static emission spectra suggest that polymerization of glass network can be improved by proper addition of aluminum into the system, which can be evidenced by partial conversion of Q2 to Q3 species of phosphorus and the shift of P–O–P asymmetric stretching vibration toward lower frequency, and this turns out beneficial to Bi NIR emission. Embedding aluminum tetrahedra into phosphorus glass network can reduce the local crystal field around bismuth and therefore lead to the blueshift of Bi emission. This work presents new insights into the luminescent behavior of Bi ions in phosphate glass and it helps the design and fabrication of Bismuth‐doped glasses and fibers in future. [ABSTRACT FROM AUTHOR]

Because of superbroad luminescence in the range of near infrared ( NIR), Bi-doped glasses and fibers have received more attentions recently for the applications in super broadband optical fiber amplifiers or new wavelength lasers. As the luminescence comes from the transitions between naked 6p orbitals of bismuth, it is very susceptible to slight changes of local field around Bi. Therefore, it is always very challenging to predict NIR emission of bismuth in advance. Here, we found bismuth NIR emission shows predictable tendency in ternary glass system of MgO-Al2O3-SiO2. The emission peak shifts red along the content of magnesium upon the excitation of 484 nm, which follows a single exponential growth equation. In the meantime, the full width at half maximum ( FWHM) is broadened while the lifetime keeps decreasing. Glass structure analysis on basis of FTIR, 27Al NMR, 29Si NMR spectra reveals that these changes correlate to integrity of glass network, the increased disorder of local field around bismuth and the enhanced interaction between bismuth and host, which are perhaps due to the linear increase of nonbridging oxygen, and the enhanced Si-O asymmetric stretching vibrations along with magnesium, respectively. Electron probe microanalysis shows good homogeneity of Si, Al, Mg, Bi, and O distribution within the samples, and yoyo experiments of heating and cooling between 30°C and 300°C reveal the good resistance of such doped glasses to thermal degradation. This makes the glasses promising in applications of fiber devices even under extreme condition such as at higher temperature. The finding in this work should be helpful for the design of Bi-doped laser glasses in future. [ABSTRACT FROM AUTHOR]

Nd3+‐doped phosphate laser glasses have been attracting much attention and widespread investigation due to their high solubility of rare earth (RE) ions, excellent spectroscopic properties, and large damage threshold. However, the narrow NIR emission bandwidth (less than 30 nm) of these Nd3+‐doped phosphate glasses limits their further application toward ultrahigh power field and efficient fiber laser in new region. Here, we demonstrate the broadening and enhancing of Nd3+NIR emission in laser glass of zinc aluminophosphate through tuning the glass structure and covalency of Nd‐O bond without limiting the radiative properties of Nd3+. The maximum bandwidth of 1.05 μm emission is broadened to 50 nm, which is comparable to that of Nd3+‐doped aluminate laser glasses. Simultaneously, the lifetime of 4F3/2 level is elongated nearly by two times. Structural and optical properties of prepared glasses were discussed systematically to reveal the mechanism. Detailed analysis on optical spectra and glass structure indicates that the bandwidth is affected by not only the covalency of Nd‐O but also the compactness of glass structure. Our results could enrich our understanding about the relationship between local glass structure and luminescence behaviors of active centers, and may be helpful in designing new RE‐doped laser glass systems. [ABSTRACT FROM AUTHOR]

• A series of Bi and nonactive rare earth (RE) codoped aluminoborate glasses were prepared and systematically investigated. • The effect of nonactive RE on aluminoborate glasses structure and optical basicity was determined. • When discussing the energy transfer between optical centers with multiple valences and RE ions (such as Bi, Mn and Cr), the effect of RE on glass structure and optical basicity should be considered. Bismuth (Bi) doped glasses and fibers, as a new generation of gain media, have been drawing wide attention for the super broad and long lived near infrared (NIR) emission. Yet, great challenge exists for modulating the Bi NIR emission in multi-component glasses. Codoping rare earth ions is a feasible way to modulate the NIR emission properties of Bi, yet limited success have been achieved. Here, to provide deeper understanding on Bi-RE codoped glass, we prepared a series of Bi and nonactive rare earth (RE) codoped aluminoborate glasses and systematically investigated the optical and structure properties. Evidenced by detailed structural and optical characterizations, it is found that the addition of nonactive RE ions changes the glass structure and optical basicity, so as to alter the optical properties of Bi. These results indicate that one should consider the effect of codopant on glass structure and optical basicity when modulating the optical spectra of active ions based on energy transfer, especially for those with multiple valences. [ABSTRACT FROM AUTHOR]