Er3+‐doped fluoride glass and fiber have been widely used in multiple fields such as mid‐infrared laser, visible laser, and amplifier. However, there is no unified conclusion on the thermal and optical properties with respect to varying concentrations of Er3+ doping. Furthermore, this is a paucity of systematic guidance on the preparation of Er3+‐doped fluoride glass and fiber. In this study, fluorozirconate fiberglass with Er3+ doping is systematically examined. Additionally, a preliminary explanation of the evolutionary behavior of glass devitrification, thermal properties, and fluorescence properties is provided. Energy transition models were built for 1.5 and 2.7 µm emissions in Er3+‐doped fluorozirconate at room temperature. Moreover, a suitable doping concentration is proposed based on the evolutionary behavior of thermal and optical properties. In this study, guidance on appropriate Er3+ doping concentration levels in fluorozirconate glass is provided and potential applications are explored.

Perfluoride glass ceramics (FGCs) with SrF2/CaF2 mixed crystals were prepared using a concurrent rapidquenching-crystallization process. The FGCs contained dense, homogeneous, round crystals of sizes less than 1 mu m with high transmittance (exceeding 80 % at 3-8 mu m) and low phonon energy (508 cm-1). The fluorescence properties of the FGCs doped with Er and Dy were investigated. The energy transfer efficiency between Er and Dy reached 93.81 % and 98.13 %, corresponding to Er: 4I11/2 to Dy: 6H5/2 and Er: 4I13/2 to Dy: 6H11/2, respectively. This enhancement is attributed to the enrichment of rare-earth ions in the crystals induced by phase-separation and low phonon energy of the host material, FGC. Moreover, the average lifetime of Er: 4I11/2 in FGC reached 10.13 ms, which is the highest reported value for glass ceramics to our knowledge. This study enriches the research theory of FGC and provides guidance for expanding the properties of materials for mid-infrared photonics.

Objective The mid - infrared band of 2-5 p.m, which contains the atmospheric transmission window and the fingerprint absorption peaks of many molecules, holds vast potential applications in areas such as biomedicine, precision machining, and mid - infrared photoelectrical countermeasures. Although high - power mid - infrared lasers can be generated using methods such as nonlinear frequency conversion, the existing devices are often bulky and structurally complex, making them unsuitable for scenarios with complex optical paths or spatial constraints. Optical fibers, as an excellent and flexible light guide medium, can realize miniaturized and lightweight systems and have been widely studied. The materials mainly used for optical fibers include silicate glass, tellurite glass, fluoride glass, and sulfide glass. Among them, silicate glass fibers have an infrared cut - off edge at approximately 2.5 p.m, making them unable to transmit lasers in the mid - infrared range. Tellurite glass fibers exhibit significant intrinsic absorption in the wavelength range greater than 4 mu m, leading to rapid increases in loss and an inability to meet low - loss transmission in the 2-5 mu m full spectrum. Sulfide fibers have a broader infrared transmission range; nevertheless, the absorption bands caused by S -H and Se -H bonds are challenging to eliminate, resulting in higher average loss in the 2-5 mu m wavelength range. Currently, the main choice for low - loss transmission across the entire 2-5 mu m range is fluoroindate fiber (InF 3 - based fiber). This study introduces the design and preparation of InF 3 - based fibers suitable for high - power mid - infrared laser transmission. Methods The early investigation by the research team on the crystallization behavior of fluoroindate glass indicated that in the molten state of multi - component InF 3 - based glass, high field strength fluoride cations compete for the nearby fluoride ions, leading to phase separation. The formation of phases reduces the activation energy for non - uniform nucleation in the melt, prompting spontaneous crystallization during the glass cooling stage. Based on this, the research team utilized inorganic glass engineering software for simulation analysis. Combining the team own accumulated experience in fluoroindate glass formulations, the composition of InF 3 - based optical fiber core/cladding glass is designed. Using the designed glass composition, a precursor for fluoroindate glass is prepared through the melt - quenching method. Combined with the team developed physical - chemical dehydroxylation technique, water is efficiently removed from the glass. Finally, high - power transmission InF 3 - based optical fibers are drawn by employing a " short heating zone " specialized optical fiber drawing process. Results and Discussions Figure 1 displays the mid - infrared transmittance spectrum of a 10 mm thick InF 3 - based glass precursor, which reveals no significant absorption near the 2.8 mu m wavelength, indicating effective elimination of hydroxyl groups in the glass. Through differential thermal analysis (DTA), the transition temperature (T g ) and crystallization temperature (T c ) of the glass are investigated (Fig. 2). The glass transition temperatures for the core and cladding glasses are 295 degrees C and 299 degrees C , respectively. The glass transition temperatures for the core glass and cladding glass are close, which is favorable for the fiber drawing process. The crystallization temperatures for the core and cladding glasses are 384 degrees C and 381 degrees C, respectively. Using the formula triangle T=T c -T g , the thermal stability parameters ( triangle T) for the core and cladding glasses are calculated to be 89 degrees C and 82 degrees C , which indicates that both glasses have good thermal stability, making them suitable for subsequent fabrication of fibers. The optical fiber preform rod is heated to the vicinity of the glass transition temperature. Once the preform rod forms a molten tip, it is drawn and elongated into an optical fiber under the influence of gravity. The dimensions of the fiber are illustrated in Fig. 3, with a core diameter of 200 mu m and a cladding diameter of 260 mu m. The average loss of the optical fiber is <= 0.22 dB/m @ 3-5 mu m [Fig. 3(b)]. In practical applications, optical fibers may encounter sharp and pointed objects, potentially leading to damage during use. Armoring the optical fiber to create a fiber optic cable can effectively address this issue, significantly enhancing the safety of optical fiber use (Fig. 4). The transmission results of optical fibers and cables are shown in Fig. 5. Pulsed laser with a wavelength of 3.7-4.8 mu m is used as the target light source. The transmission of pulsed laser at the 10 W level has been realized in a laboratory environment through spatial coupling. Conclusions The Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences has successfully produced high - power transmitting energy InF 3 - based optical fibers, demonstrating initial capabilities for independent production of mid - infrared fluoroindate optical fibers. The fiber products with independent intellectual property rights are initially realized the indigenization substitution. The manufactured cables have achieved pulsed laser output at the 10 W level in the 3.7-4.8 mu m wavelength range, showcasing excellent mid - infrared laser energy transmission performance. With the ongoing optimization and adjustments to fiber composition and manufacturing processes, the optical and mechanical properties of the fibers will further improve, providing robust support for the development of high - end infrared optical systems in our country.

氧氟玻璃具有良好的透红外性能,且可实现低成本、短周期和大尺寸制备,是高端红外窗口的优质候选材料.随着红外技术的不断革新和光学系统技术的不断进步,对超大尺寸、高性能的红外窗口玻璃提出了更高的要求.基于此,中国科学院上海光学精密机械研究所研究团队经过十余年技术积累,通过精密温场控制技术和脱羟除铂技术,首次实现了国内米级高性能镓酸盐氧氟红外玻璃及大尺寸半球整流罩的制备,此材料可作为红外窗口应用于新一代红外探测等多个领域.

To the best of our knowledge, this paper first reports ErF3 microcrystals controllably deposited in perfluoride glass using phase-separation engineering techniques. The sample exhibited strong upconversion red-light emission owing to the small distance between Er3+ ions and low phonon energy (585 cm-1). The sample has a high red/green ratio of up to 18.6, which, to our knowledge, is the highest reported value in Er3+-doped fluoride glass ceramics. Furthermore, the sample has a long fluorescence lifetime (3.18 ms @660 nm), good color saturation (0.6255,0.3707), and good thermal stability (Δ E=0.31e V). Therefore, this sample has the potential for application across multiple fields, such as color display, visible laser, and lighting.

This Letter proposes a simple approach for the realization of a broadband near-infrared (NIR) luminescence source in erbium ion single-doped tellurite glass, which is bent on tailoring the network structure. Under the collective action of multiple broadening mechanisms and fluorescence capture, broadband fluorescence with a full width at half maximum (FWHM) of 132 nm (1500-1632 nm) was achieved. To the best of our knowledge, this is the largest FWHM reported for erbium single-doping of tellurite glass materials. Meanwhile, this fiberglass exhibits excellent thermal stability and high visible to NIR transmittance. Furthermore, a novel equivalent five-level Stark splitting model is proposed that can effectively explain the spectrum broadening. This study is beneficial for the further development of broadband optical amplification.

For transparent low melting inorganic glass, which is relevant for sealing and additional applications, Pb-containing glasses have reached the lowest melting point and best comprehensive performance. Considering potential toxicity and regulatory limitations, there is urgent need to develop Pb-free ultra-low melting point glass. Herein, we systemically investigated the structure and luminescence evolution of the Pb-free ultra-low melting quaternary tin fluorophosphate glasses (NaF-SnF2-SnO-P2O5), in which varied NaF content was tuned to affect the properties of glass. With NaF content increases, the Sn-O and P-O bonds have been gradually transformed to Sn-F and P-F bonds, and the phosphrous tetrahedron PO4 has been converted to PO3F. The weaken bonding results in the decrease of the ultra-low melting point to 329 degrees C when NaF increased to 15 a.t.%, 29(o)C lower than the ternary glass. The blue shifts of both absorption and photoluminescence spectra were observed due to the higher ionic character of glass structure with NaF increases. As reported previously in the ternary tin fluorophosphate glass, the quaternary glass system also shows a phosphorescence behavior (similar to 1 s) due to the existence of oxygen vacancies. Additionally, the changes in oxygen vacancy defects correlate with the NaF content, thus affecting the decay time as well. The ultra-low melting point luminescent quaternary tin fluorophosphate glasses (NaF-SnF2-SnO-P2O5) may be relevant for opto-electronic applications such as the packaging in displays or light-emitting diodes.

Fluoride glass is considered as an excellent optical material owing to its ultralow phonon energy (578 cm(-1)). However, its high thermal expansion coefficient (15.87 x 10(-6)/K) and deformability severely limit applications under service environments with high temperature, high humidity, and high-power irradiation. To overcome these limitations, we developed a ZBLAN-based fluoride glass ceramics (CZBLAN GCs) contained the negative thermal expansion material-CaZrF6 crystals by phase-separation engineering. The ability to control the precipitation of the desired crystal phase was achieved by adequate compositional design for phase separation, yielding improved or new properties in the development of fluoride GCs. With the successful precipitation of very uniformly dispersed single CaZrF6 crystals in the glass phase (up to similar to 40% crystallinity), a significantly lower thermal expansion coefficient (3.66 x 10(-6)/K) in the fluoride system was achieved. Moreover, enhanced fluorescence properties of Eu-doped CZBLAN GCs were observed compared with those of Eu-doped ZBLAN glass owing to the lower phonon energy in GCs.

Er3+-doped transparent perfluoride composite glass (PFCG) containing SrF2 crystals was obtained by a one-step method. PFCG was observed to maintain the formation of a single SrF2 crystal phase even when the Er3+ doping concentration was as high as 8 mol%. Importantly, Er3+ was enriched in the crystalline region, which promoted grain growth. This ensures effective emission of upconversion (UC). Interestingly, green and red UC emissions were found to be tunable in the range of 1-6 mol% Er3+ doping, and the UC emission and lifetime started to produce concentration quenching until 6 mol% Er3+ doping. To the best of our knowledge, this is the highest quenching concentration of Er3+ in composite-glass materials. Moreover, the dominant UC process was systematically analyzed at different doping levels. This research is expected to provide ideal candidate materials and appropriate Er3+ concentration doping level guidance in PFCG for the field of UC lasers.

Fluoindinate glass (FIG) is considered an ideal material for fiber laser devices and mid-infrared bulk optics components owing to its ultra-low phonon energy and broad transparency window. However, the heat generated by devices fabricated with FIG during their operation limits its application. Therefore, there is an urgent need to study its high-temperature properties. In this study, the thermal properties, microstructure, crystal phase behaviors, and optical and luminescent properties of high-temperature FIG were comprehensively evaluated. We also attempted to reveal the changes in its structure at high temperatures using variable-temperature Raman spectroscopy. We first found that the stretching vibration intensity of nonbridging F(F-nb) decreases, and the bending vibration of FIG increases with an increase in temperature, indicating that high temperatures could lead to the fracture of bridge bonds between some [InF6](3-) octahedrons. Certainly, this will lead to glass structural instability, which will further increase the tendency of FIG to undergo devitrification in high-temperature conditions. We believe that this work will provide a reference for the performance improvement and application of fluoride glass at high temperatures.

It is interesting to explore a novel oxyfluoride glass with good glass stability to be applied in optical communication and optical windows at infrared (IR) wavelength. We demonstrated a new glass of Ga 2 O 3 -doped ZrF 4 −BaF 2 −LaF 3 −AlF 3 −NaF (ZBLAN) glass using a melt-quenched technique. The effect of Ga 2 O 3 -doping on glass properties and structure was characterized by differential thermal analysis (DTA), IR spectra, Raman spectra, and X-ray diffraction (XRD). It is found that the glass thermal stability (Δ T ) increases by 14% when the addition of Ga 2 O 3 reaches 1mol%. With the increase of Ga 2 O 3 content, the density and refractive index of the glasses increase. Ga 2 O 3 -doping does not affect the IR cut-off edge and maintains the transmittance near 90% in the range of 2.5–5 µm, which is almost equal to the undoped sample. Ga 2 O 3 -doping hardly changes the initial coordinated structure of Zr 4+ according to the results of IR spectra and Raman spectra. Ga 3+ holds in the interstice site of the network coordinated with F − and the part of O 2− introduced by Ga 2 O 3 is coordinated with Al 3+ forming Al−O bond. This study offers a new glass composition that may be potentially used in fabricating mid-IR optical fiber and large-size glasses for IR windows.

Perfluorinate glass ceramics with ultra-low phonon energy are very important optical and photonic materials. Unfortunately, there is no suitable method to obtain transparent perfluorinate glass ceramics due to poor thermal stability of fluoride glass. As a result, wide applications of glass ceramics in advanced infrared systems are restricted. Here, an effective method based on phase-separation engineering is used to develop transparent perfluorinate glass ceramics. In this article, a novel transparent Er2+-doped ZnZrF6-Ba6Zn7F26 perfluorinate glass ceramic was designed and fabricated by phase-separation engineering. The sample exhibits low phonon energy (564 cm(-1)), ultra-wide transmission range (0.33-8.2 mu m, T >= 50 %), and strong infrared emission, which is better than that of ZBLAN glass, oxide-, and oxyfluoride-glass ceramics. These good properties of the perfluorinate glass ceramic demonstrate that phase-separation engineering not only offers an effective approach to obtain perfluorinate glass ceramics but also provides wide-ranging opportunities for advanced infrared optical and photonic materials.

To obtain red-emitting luminescent material for high-power UV LED and UV LD applications, an additive-free Y2O3:Eu3+ phosphor ceramic was successfully prepared in this work. The nitrate pyrogenation method is applied to obtain raw nanopowders with high reactivity, and a hybrid sintering method combining low-temperature presintering and subsequent hot isostatic pressing (HIP) is then applied to realize full densification of the final ceramic products. The effects of the presintering temperature on the density, microstructural, and optical properties are investigated in detail. The HIP-treated Y2O3:Eu3+ ceramic presintered at 1450 degrees C exhibits a high transmittance near 80 % at 600 nm. Due to the nonuse of sintering additives, the thermal conductivity of Y2O3:Eu3+ ceramic product reaches 10.9 Wm(-1) K-1 at room temperature. The achieved Y2O3:Eu3+ ceramic also exhibits good applicability under the excitation of a UV LED chip and UV laser light, showing promise as a color converter for high-power UV LED and UV LD applications.

A highly transparent Nd,Y-codoped Ca1-xSrxF2 glass-ceramic with excellent optical properties was fabricated by the controllable spontaneous precipitation (CSP) under supersaturated state. The micron-sized Ca1-xSrxF2 crystal provides a favorable emission environment for Nd3+ ions. Meanwhile, the buffer ions Y3+ effectively addressed the fluorescence quenching originating from [Nd3+-Nd3+] clusters. The corresponding sample exhibited high transmittance (T-@1053 (nm) = 83%), large absorption coefficient (9 cm(-1) @796 nm), intense 1.053 mu m photo- luminescence, large emission bandwidth (similar to 32 nm), and moderate lifetime (167 mu s), implying the glass ceramic would be powerful candidates for application in ultrashort pulse lasers. In addition, the sample also showed low phonon energy (IR-cut edge similar to 4.5 mu m), a low absorption coefficient of -OH (alpha(.o11)similar to 1.0 x 10(-4) cm(-1)), and high mid-infrared transmittance (T-@2700 nm = 85.4%), which is expected to be applied in the field of mid-infrared.

The glass-forming ability of Er3+-doped fluorozirconate glasses was systematically investigated by replacing Na+ ions by Li+ ions. As Li+ content increased, the glass-forming ability showed an approximate Gaussian distribution, and an optimal thermal stability was obtained with the dopant of 5 mol% Li+ The mechanism for the enhancement of glass-forming ability in fluoride glasses upon partial substitution of Li+ ions was preliminarily investigated. Moreover, an Er3+-doped fluorozirconate glass modified by 5 mol% Li+ exhibited stronger fluorescence than the unmodified original glass. The results provided a suitable approach for fluoride glass modification.

Step-index fluorozirconate (ZBLAN) and fluoroindate (InF3) fibers with all-normal dispersion (ANDi) are proposed for mid-infrared (MIR) nonlinear application. The fibers have a flat and near-zero ANDi profile at the MIR region to generate a highly coherent MIR supercontinuum (SC). A multiwatt coherent MIR SC is allowed to guide in the ANDi ZBLAN and InF3 fibers of 5.5 µm and 6.5 µm core diameters. The MIR SC is simulated in the ANDi fluoride fibers pumped with high peak power at 1960 nm and 2700 nm. The simulation results show that a highly coherent MIR SC spanning from 1100 to 3000 nm with flatness <10dB generates from the ANDi ZBLAN fiber pumped at 1960 nm, and a highly coherent MIR SC extending from 1500 nm to 3800 nm can generate from the ANDi InF3 fiber pumped at 2700 nm. These ANDi step-index fluoride fibers are available and promising nonlinear media for achieving a high-power all-fiber structure-coherent MIR SC source.

This Letter highlights a cost-effective, simple, and rapid one-step process leading to the (Sr0.84Lu0.16) F-2.16 glass ceramic in a completely new perfluoride system. The mechanism was demonstrated clearly. This material shows high transparency in the UV (0.35 mu m) range up to far-IR (10.8 mu m). In addition, low phonon energy, as well as good mechanical properties, chemical durability, spectral performance, and long lifetime (7.2 ms) of Er3+:2.7 mu m are also possessed by this material. This Letter effectively breaks through the performance limitation of a glass matrix on fluoride crystallites in glass ceramics for the first time, to the best of our knowledge. Meanwhile, it also provides a promising optical material for windows and lasers by a simple and cheap method. (C) 2019 Optical Society of America

The effect of chloride ions on the properties of Er3+-doped fluorozirconate glass is systematically studied. We first observed a nonlinear mutation of the glass-forming abilities and fluorescence properties of glass when 1 mol % fluoride ions were replaced by chloride ions. The results differed from previous reports. In order to explain this special phenomenon, we investigated the changes of the structure and the Judd-Ofelt theory of glass before and after halogen anion substitution. The results indicate that part of the fluorozirconium octahedral network was destroyed and transformed into a chain structure due to the bridging chlorine atoms, of which the electronegativity is lower than F-. With the increase of the glass-forming abilities gradually recovered due to the decrease of the liquids temperature. Therefore, a non-linear mutation of Cl-, the glass-forming abilities was exhibited. Furthermore, the predictor chi, the ratio between the Judd-Ofelt parameters Omega(4) and Omega(6), and the reduction in phonon density caused a mutation on the fluorescence properties of glass, such as the intensity and lifetime. This research could provide a new reference for the anion modification of fluoride glass.

The structure of glasses in the systems (100 - x)B2O3-xPbF(2) (x = 30, 40, and 50) and 50B(2)O(3)-(50 - x)PbO-xPbF(2) (x = 5, 10, 15, 20, 25, 30, 35, 40, and 45) has been studied by solid state NMR and EPR spectroscopies.-On the basis Of B-11 and F-19 high resolution solid state NMR as well as on B-11/F-19 double resonance results, we develop a quantitative structural description on the atomic scale. F-19 NMR results indicate a systematic dependence of the fluoride speciation on PbF2 content: At low x-values, F- ions are predominantly found on BO3/2F- units, whereas, at higher x-values, fluoride tends to be sequestrated into amorphous domains rich in PbF2. In addition, both pulsed EPR studies of Yb3+ doped glasses and photophysical studies of Eu3+ doped samples indicate a mixed fluoride/borate coordination of the rare-earth ions, and the absence of nanophase segregation effects.