The Transformation from Translucent into Transparent Rare Earth Ions Doped Oxyfluoride Glass‐Ceramics with Enhanced Luminescence

Abstract

This material bears the advantages of both the fluoride crystallites and the oxide glass matrix. [3] The crystallites have a low phonon energy environment, while the oxide glass matrix possesses both high optical transparency and excellent chemical and thermal stabilities, which are crucial for protecting the fluoride crystallites from reacting with the moisture from the environment. For the oxyfluoride GCs doped with rare earth (RE) ions, the RE ions, which serve as the up-conversion (UC) luminescence centers, preferentially enter the fluoride crystallites, and hence, reduce the rate of nonradiative relaxation, thereby benefiting the UC luminescence. [4] Thus, oxyfluoride GCs are a promising candidate for optical applications such as optical amplifiers, [5] multicolor displays, [6] UC fibers, [7] lasers, [8] and optical thermometry. [9] However, it is a challenge to achieve the oxyfluoride GCs with both high transparency and superior UC luminescence.Usually, the optical transmittance of the oxyfluoride GCs is lower than that of their corresponding precursor glass since the former has stronger optical absorption and light scattering It is known that the optical transparency of an oxide glass decreases with an increase in the size and fraction of crystals in the glass during heat-treatment. Here, the authors report an opposite scenario, where a translucent Er 3+ −Yb 3+ doped oxyfluoride precursor glass-ceramic (P-GC) becomes transparent with increasing crystal size and crystallinity. Specifically, in the heat-treated P-GC samples, the authors observe that the growth of the existing Ba 2 LaF 7 crystals and particularly the formation of small spherical Ba 2 LaF 7 crystals greatly enhanced the light transmittance. To reveal the origin of this anomalous pheno menon, the authors perform detailed morphology and structure analyses on both P-GC and the heat-treated P-GC samples and molecular dynamics simulations of the precursor glass. The results show that the composition of the residual glass phase is altered (e.g., depletion of La 3+ ) in the way that the differences in refractive index between the glass matrix and the crystals are greatly reduced. As a consequence, the light scattering of the heat-treated P-GC is suppressed, and hence, the derived P-GC becomes transparent. In addition, a proper heat-treatment can also enhance the luminescence of the studied P-GC system.

Broadband Optical Amplification in Bi‐Doped Multicomponent Glass Fiber

“…To determine the underlying mechanism, the relation between the thermal properties and optical response was investigated. [32][33][34] In Figure 2c, the left inset displays the differential scanning calorimetry (DSC) curve of the sample; it indicates that glass crystallization occurs at 820°C. The right inset displays the NIR emission spectra under heat treatment at various temperatures.…”

Theoretical and experimental investigation of Al3+ ion-suppressed phase-separation structures in rare-earth-doped high-phosphorus silica glasses

“…[11][12][13][14] In recent years, RE-doped silica-based composite glasses (Re-SCGs) have attracted considerable attention due to their high gain efficiencies, tunable crystal-field environments, and unique thermodynamic properties. [15][16][17] As is known, the luminescence efficiency of RE ions is closely related to their chemical state and the surrounding chemical environment provided by the host glass. 18 Appropriate doping, heat treatment, or deliberate topology design can be employed to make RE ions occupy sites with very different chemical environments, which have been shown to induce new photoluminescence features such as ultra-broadband and enhanced up/down conversion emission.…”

Fluorine in Complex Alumino-Boro-Silicate Glasses: Insight into Chemical Environment and Structure

“…Various glass oxyfluoride systems are also important for optical and photonic applications, , including glass ceramics with F-containing optically active crystals − and rare-earth fluoride-containing systems for lasers . Of the oxyfluoride glass-forming systems that have been investigated, including silicate and borate systems, perhaps the most important for optics has been fluoride-containing phosphate glasses. , …”