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All‐solid‐state sodium ion batteries (ASSIBs) attract growing attention as the next generation of batteries due to their high energy density, excellent safety, and the abundance of sodium resources. As a vital component of ASSIBs, chalcogenide Na‐ion solid‐state electrolytes (SSEs) have been widely studied due to their high ionic conductivity and outstanding ductility. However, due to the susceptibility to organic solvents and moisture, no chalcogenide Na‐ion SSEs membrane has been reported while only thick SSEs pellets have been investigated, which introduces abundant "dead" weight and lowers the energy density of ASSIBs. Herein, utilizing the excellent air stability of Na3SbS4, a thin (∼220 μm) Na3SbS4 membrane is prepared in air via a facile dry‐film method with polytetrafluoroethylene fibrillation, which exhibits a high ionic conductivity of 0.19 mS cm and an excellent critical current density of 0.6 mA/cm2. In summary, the chalcogenide Na‐ion SSEs membranes with high ionic conductivity and the simple preparation process could be readily adopted by pragmatic high‐performance ASSIBs. [ABSTRACT FROM AUTHOR]

Chalcogenides with high ionic conductivity and appropriate mechanical properties are promising solid‐state electrolytes (SSEs) to substitute current liquid electrolytes in lithium‐ion batteries. Yet, their practical applications in all‐solid‐state batteries are still retarded by both the low critical current density and the inferior interfacial stability toward electrodes. In this work, a series of superior SSEs, that is, Li2S‐P2S5‐B2S3 electrolytes, are developed via a ball‐milling and then melt‐quenching strategy. These SSEs exhibit a high critical current density of 1.65 mA cm−2 and a long cycling life of over 300 h. In addition, the evolution mechanism of the interphase between SSEs and metallic lithium is revealed via operando electrochemical impedance spectroscopy, depth‐profiling XPS, and in situ Raman spectroscopy. The structural and chemical heterogeneities are found to be the main origins of the continual interphase evolution. The resulting "multi‐layer mosaic like" interphase facilitates the suppression of Li dendrite growth, and hence, prolongs the lifetime of lithium‐ion all‐solid‐state batteries. In addition, the preparation technique of SSEs developed in the present work is feasible for scale‐up production. [ABSTRACT FROM AUTHOR]

Fiber‐based inorganic thermoelectric (TE) devices, owing to the small size, light‐weight, flexibility, and high TE performance, are promising for applications in flexible thermoelectrics. Unfortunately, current inorganic TE fibers are strictly constrained by limited mechanical freedom because of the undesirable tensile strain, typically limited to a value of 1.5%, posing a strong obstacle for further application in large‐scale wearable systems. Here, a superflexible Ag2Te0.6S0.4 inorganic TE fiber is demonstrated that provides a record tensile strain of 21.2%, such that it enables various complex deformations. Importantly, the TE performance of the fiber shows high stability after ≈1000 cycles of bending and releasing processes with a small bending radius of 5 mm. This allows for the integration of the inorganic TE fiber into 3D wearable fabric, yielding a normalized power density of 0.4 µW m−1 K−2 under the temperature difference of 20 K, which is approaching the high‐performance Bi2Te3‐based inorganic TE fabric and is nearly two orders of magnitude higher than the organic TE fabrics. These results highlight that the inorganic TE fiber with both superior shape‐conformable ability and high TE performance may find potential applications in wearable electronics. [ABSTRACT FROM AUTHOR]

Efficient optical modulation enables a significant improvement of optical conversion efficiency and regulation of optical response rate, showing great potential for optoelectronics applications. However, the weak interaction between photons poses a strong obstacle for manipulating photon–photon interactivity. Here, upon simultaneous excitation of 850 and 1550 nm, a fast–slow optical modulation of green up‐conversion (UC) luminescence in oxyfluoride glass ceramics containing NaYF4:Er3+ nanocrystals can be achieved. Compared with the sum of luminescence intensity excited by the two single‐wavelengths, green UC luminescence excited by simultaneous two‐wavelength presents an obvious increase by approximate six times. Interestingly, the response rate of green UC luminescence relies on the pump strategy of two‐wavelength excitation, showing as high as two times of the fast–slow response difference. The fast–slow optical modulation of green UC luminescence under two‐wavelength excitation is promising for emerging applications in all‐optical switching. [ABSTRACT FROM AUTHOR]

Chalcogenide solid‐state electrolytes (SSEs) have been receiving growing attentions due to their high ionic conductivity and suitable mechanic properties, especially the Li2S–P2S5 systems incorporated with a second glass network formers (Si, Ge, Sn, and so on) besides P. Although the ionic conductivities are generally enhanced with the second glass network formers, the comprehensive effects of different glass formers on other properties, including electrochemical, cycling, and air stability, remain elusive. To acquire deeper understanding, herein, three common but representative glass network formers (SiS2, GeS2, and SnS2) were introduced into Li2S–P2S5, and their individual effects were investigated systematically. The results of multiscale characterizations before and after lithium stripping/plating cycling confirmed that the introduction of metal cations (Ge, Sn) generally leads to worse electrochemical stability and shorter cycle life of these SSEs toward lithium metal compared with SSEs with nonmetal cation (Si) modification. However, the air stability is related to the binding energy of M–S (M = Si, Ge, Sn), which is consistent with the hard base soft acid theory. This work provides valuable understanding for designing pragmatic Li2S–P2S5–MS2‐based SSEs with high electrochemistry, cycling, and air stability. [ABSTRACT FROM AUTHOR]

Ultrafast fiber lasers, due to their short pulse duration, excellent beam quality, and high brightness, are extensively used in precision processing, biomedicine, nonlinear optics, and spectroscopy. However, great challenges still exist in improving the optical conversion efficiency in glass‐based gain media because of the high non‐radiative transition probability. Here, we demonstrate an oxyfluoride glass–ceramic (GC) fiber containing NaYF4:Yb3+ nanocrystal that enables enhanced 1064‐nm continuous‐wave laser output with an optical signal‐to‐noise ratio of 60 dB. Compared with the as‐prepared glass fiber, the optical conversion efficiency of GC fiber is improved from 24.2% to 30.0%. The improvement of laser action is mainly caused by the preferential incorporation of Yb3+ into the NaYF4 nanocrystal with low phonon energy. Using this well‐developed GC fiber, we successfully built a passively mode‐locked pulsed fiber laser that deliveries laser pulses with a pulse duration of 8.1 ps and a repetition frequency of 56.92 MHz. These results highlight that the GC strategy may provide a roadmap for the development of ultrafast fiber laser and the application of GC fibers in various optoelectronic fields. [ABSTRACT FROM AUTHOR]

Fiber lasers, owing to the high beam quality and super robustness, are widely used in fields from optical communications, fiber sensing, biomedicine to material processing. The use of glass fibers as the gain medium has, however, posed a strong obstacle for improving efficiency and, especially, achieving efficient lasing action in the mid‐infrared (MIR) region, because of the relatively large nonradiative energy loss. Here, the fabrication of a Tm3+‐doped tellurate glass‐ceramic (GC) fiber is demonstrated, which enables enhanced lasing action at ≈2 µm. Compared with the as‐prepared fiber, the optical conversion efficiency of GC fiber is increased from 8.8% to 14.1%. The microstructure and spectral characterization analyses suggest that the improvement of the laser performance in GC fiber is induced by the significant change of the local environment surrounding Tm3+ ions due to the formation of nanocrystals within the glass fibers. Moreover, the developed GC fiber also enables Q‐switched pulsed laser output at ≈2 µm with a pulse energy of 3.2 J and pulse width of 4.1 ns. The results demonstrated here may have strong implications in the development of MIR fiber lasers and the applications of GC fibers in MIR photonics. [ABSTRACT FROM AUTHOR]

Transparent glass ceramics (GCs) consisting of an homogeneous glass phase and a well‐dispersed crystal phase are considered as ideal optical gain materials potentially applied in optoelectronic devices due to the combination of facile processability of glass and the intense crystal field of nanocrystals. Here, a heat‐induced nanocrystal‐in‐glass method is employed to integrate the active ions Tm3+ into Bi2Te4O11 nanocrystals with an intense crystal field to realize an enhanced microlaser output. This strategy endows the efficient tellurate GC microcavity laser operating at ≈2 µm. Compared with the laser properties of as‐prepared glass microcavities, the pump threshold (260 µW) is as low as less than a quarter and the slope efficiency (0.0296%) is 5.5 times higher. Furthermore, by carefully engineering the heat treatment temperature and duration, the crystal size and distribution can be precisely controlled. Thus, the Rayleigh scattering loss that is detrimental to quality (Q) factor is effectively suppressed and the GC microcavities with high Q factors up to 105 are successfully obtained. This work provides useful insight on the development of optical functional materials and expands the practical applications of GC microcavities in various optoelectronic fields. [ABSTRACT FROM AUTHOR]

Rational design and fabrication of multicolor fluorescent sources represent one of the significant challenges in the development of high‐performance solid‐state lighting, tunable coherent lasing, and full‐color display technologies. However, generation of simultaneous multicolor emission, especially white light generation with a wide color gamut is usually beyond the ability of a single material. Heterogeneous structures made by combinations of red, green, and blue emission building blocks are bulky, inefficient, complicated, and costly. Here reported is a bottom‐up strategy to generate simultaneous multicolor emission with continuous tunability in a single monolithic material based on the "nanocrystals‐in‐glass composite" (NGC) architecture. In this approach, a self‐sustained low‐temperature solution combustion process enables homogeneous solvent dispersion and eventually stable immobilization of multiple nanocrystals in transparent matrix. With transparency of up to 80%, further demonstrated is drawing of fiber from the melt of these combustion‐processed NGC materials. The optical spectra of the as‐drawn glass fiber can be precisely tuned and clustering is effectively suppressed. Moreover, the NGC materials exhibit remarkable anti‐thermal quenching behavior at temperatures of up to 200 °C. The bottom‐up strategy for NGC provides a versatile platform for the fabrication of high‐performance multifunctional fiber‐based devices for advanced applications in lasers, illumination, displaying, and biophotonics. [ABSTRACT FROM AUTHOR]

Rare earth (RE) ions‐doped luminescent nanocrystals (NCs) with numerous unique advantages have attracted tremendous interest for the wide applications from science to engineering, yet suffering from the shortcoming of thermal quenching coming from surface organic ligands. We propose utilizing a facile acid‐base reaction to remove surface organic ligands introduced choosing carboxylic acids as stabilizing agent and weaken thermal quenching. The results showed that the acid‐base reaction displayed an outstanding cleaning effect. After acid‐treatment, most surface organic ligands were removed, and there was no influence on crystal structure and morphology of as‐prepared β‐NaYF4:Er3+ NCs. Meanwhile, with no surface organic ligands capping, β‐NaYF4:Er3+ NCs preferred brighter emission after thermal treatment, including up‐conversion (UC), near‐infrared (NIR), and mid‐infrared (MIR) emission. When calcined the acid‐treated β‐NaYF4:Er3+ NCs in different atmosphere, such as oxygen and reducing atmosphere (15%H2 + 85%N2), an unexpected enhancement of all emission bands in Er3+ was determined under phase transformation temperature, especially in oxygen atmosphere. Furthermore, all the fluorescence lifetimes of Er3+ also exhibited obvious extension. Our results supposed that the β‐NaYF4:Er3+ NCs have promising applications in safety ink, and the acid‐treatment by diluted hydrochloric acid is a general approach to remove deleterious organic ligands on NC surface further to weaken thermal quenching. [ABSTRACT FROM AUTHOR]

Fiber lasers, especially single-frequency fiber lasers, are highly desirable due to their long coherent length and narrow spectral linewidth that are unattainable in common photonic devices. However, significant challenges in the fabrication of high quality fiber laser devices still exist. In this paper, fibers with 1.55 μm laser output have been achieved using Er3+/Yb3+-codoped glass-ceramic (GC) as a core material and a “molten core” fiber-drawing technique. The prepared GC fibers demonstrate enhanced laser output with an optical signal-to-noise ratio of 65 dB and a slope efficiency of 11.8%, which are higher than those of the as-prepared glass fiber. Furthermore, a single-longitudinal mode laser with a linewidth of 7.4 kHz and a relative intensity noise (RIN) of −148.8 dB/Hz is achieved, manifesting the potential applications of the GC fibers in optoelectronic fields. Theoretical calculations and simulations are employed to understand the relation between the optical performance of the fiber laser and the atomic structure in the phase-separated region of the oxyfluoride glass cores. The demonstrated GC fibers provide a new platform for the development of multifunctional fiber lasers and open a new avenue towards practical applications for crystallized fibers. [ABSTRACT FROM AUTHOR]

Novel nanocomposite glass ceramics (GCs), containing bi-functional NaYF4:Yb3+/RE3+(RE3+ = Er3+, Nd3+) and NaAlSiO4:Cr3+ nanocrystals, were synthesized by a melt-quenching process and subsequent heat-treatment. XRD and TEM results indicate that two types of nanocrystals, NaYF4 and NaAlSiO4, disperse homogeneously in the glass matrix. Photoluminescence (PL) spectra and lifetime measurements demonstrate that RE3+ and Cr3+ ions selectively enter into the precipitated NaYF4 and NaAlSiO4 nanocrystals, respectively, after crystallization, which restrains the potential energy transfer (ET) between the rare earth (RE) and transition metal (TM) ions. Significantly, there are three modes to carry out the optical thermometry based on the fluorescence intensity ratio (FIR) from two thermally coupled levels of Nd3+, the FIR from the Cr–Nd non-thermally coupled system and the fluorescence lifetime of Cr3+. Compared to standard temperature sensors based on a single mode technique, the Yb3+/Nd3+/Cr3+ codoped oxyfluoride GCs, with excellent sensitivity and high precision, open up a new path in the optical thermometry field. [ABSTRACT FROM AUTHOR]

Abstract: It is well recognized that a widely wavelength‐tunable mid‐infrared (MIR) fiber laser plays an important role in the development of compact and efficient coherent sources in the MIR range. Herein, the optimizing Er/Ho ratio for enhancement of broadband tunable MIR emission covering 2.6‐2.95 μm in the Er3+/Ho3+‐codoped transparent borosilicate glass‐ceramic (GC) fibers containing NaYF4 nanocrystals under 980 nm excitation was investigated. Specifically, the obtained GC fibers with controllable crystallization and well fsd‐maintained structures were prepared by the novel melt‐in‐tube approach. Owing to the effective energy transfer between Er3+ and Ho3+ after crystallization, the 2.7 μm MIR emission was obviously enhanced and the emission region showed a notable extension from 2.6‐2.82 μm to 2.6‐2.95 μm after the addition of Ho3+. Importantly, we conducted a theoretical simulation and calculation related to the MIR laser performance, signifying that the GC fiber may be a promising candidate for MIR fiber laser. Furthermore, the melt‐in‐tube approach will provide a versatile strategy for the preparation of diverse optical functional GC fibers. [ABSTRACT FROM AUTHOR]

Abstract: White lasers are promising illuminants for emerging visible light communication, which can overcome bottlenecks of lower energy conversion efficiencies and output powers in traditional white light‐emitting (WLE) diodes. However, optical gain materials for white lasers are suffering from great challenges of material growth and growth‐compatible cavity structure where lasing of all three elementary colors can be supported simultaneously. Here, an exquisite physical strategy is demonstrated to realize simultaneous red, green, and blue (RGB) upconversion (UC) photoluminescence for white light modulation for the first time, namely using dual lasers at 850 and 980 nm to stimulate easy‐fabricated glass ceramics (GCs) fiber laser materials (Pr3+ single‐doped germanium oxyfluoride GCs). It is shown that tailorable white light is much more sensitive to lower dopant concentration for GCs than that for glass. Furthermore, compared to glass, UC fluorescence intensities in GCs have approximately two orders of magnitude enhancement. The feasibility of the judicious dual‐lasers excitation tactic is validated for high efficacious RGB fluorescence emission for white light from Pr3+ single‐doped GCs via electronics transition dynamics and theoretical calculations. The white light emission from Pr3+ single‐doped GCs, adjusted by simultaneous dual‐lasers excitation, may open a novel door to develop white light GCs fiber lasers for application in future wireless communication. [ABSTRACT FROM AUTHOR]

All solid-state PbS quantum dot (QD)-doped glass fibers with tunable near-infrared (NIR) emission were successfully fabricated by using the “melt-in-tube” method for the first time. The precursor fibers were first prepared without any obvious element diffusion or crystallization by drawing the fiber preform at a heating temperature at which the fiber core was already melted while the fiber cladding was softened. Then the PbS QDs were precipitated evenly in the matrix of the glass fiber core after a careful heat treatment at low temperature. From the PbS QD-doped glass fibers, intense wavelength-tunable broad NIR emission bands were observed upon excitation with an 808 nm laser. The transmission loss of the fibers can be reduced by further matching the thermal expansion of the fiber core and cladding glass. Therefore, after further optimizing the composition and optical properties of the PbS QD-doped glass fiber, it is expected to be a potential gain medium for the development of wavelength-tunable lasers and broadband fiber amplifiers. More importantly, the melt-in-tube method exhibits a feature of completely controllable crystallization in the fiber formation process, which would open a new route for fabricating novel functional QD-doped glass fibers. [ABSTRACT FROM AUTHOR]

We demonstrated remarkably enhanced 2.7 μm emission in glass-ceramic (GC) fibers containing NaYF4:Er3+ nanocrystals with 980 nm excitation for the first time. The melt-in-tube technique is of scientific and technical significance for the fabrication of GC fibers in comparison to the conventional rod-in-tube technique. The obtained precursor fibers, in which the structure can be maintained well, exhibit no obvious element diffusion or crystallization during the fiber-drawing process. After a careful heat treatment, NaYF4 nanocrystals were controllably precipitated in the glass fiber core. Owing to the incorporation of Er3+ ions into the low phonon energy NaYF4 nanocrystals, enhanced 2.7 μm emission was achieved from the Er3+-doped GC fibers, which was almost undetectable in precursor fibers due to the high phonon energy of the borosilicate glass fiber matrix. Moreover, the 2.7 μm emission lifetime was obtained due to the excellent emission properties of Er3+ in the GC fibers. The transmission loss values of precursor fibers and GC fibers at 1310 nm were measured to be 7.44 dB m−1 and 11.81 dB m−1, respectively. In addition, a theoretical simulation based on the rate equations and propagation equations was performed to evaluate the possibility of 2.7 μm laser output. The excellent optical properties endow the GC fibers with potential applications for mid-infrared fiber lasers. [ABSTRACT FROM AUTHOR]

Nanocrystallized glass ceramics (NGCs) are important optical materials, but few studies have focused on their laser actions. Here, by precipitation of NaYF4 nanocrystals enriched with Er3+ ions in an oxide glass matrix, great enhancement of the luminescence properties for the NGC microspheres is realized. By carefully matching the refractive index of the glass matrix with that of the NaYF4 nanocrystals and controlling the size and distribution of the precipitated nanocrystals, the absorption and Rayleigh scattering losses that are harmful to quality (Q) factors are efficiently suppressed. As a result, the NGC microsphere cavities present ultrahigh Q factors up to 106 (@ 1610 nm), which is slightly lower than that of the microsphere cavities made by precursor glass. Moreover, single mode whispering gallery modes (WGMs) lasing from the NGC microsphere cavities for the first time is successfully realized. Compared with the microsphere cavity based on glass, the NGC microsphere cavity exhibits large enhancement of the pumping efficiency by more than 7 times and a decrease in the threshold by more than 2.5 times. The results demonstrated here suggest a novel method for improving the laser output performances of microcavities, which may have potential applications in areas of photonics and optical communication. [ABSTRACT FROM AUTHOR]

Applications of trivalent rare earth (RE3+)‐doped light sources in solid‐state laser technology, optical communications, biolabeling, and solar energy management have stimulated a growing demand for broadband emission with flexible tunability and high efficiency. Codoping is a conventional strategy for manipulating the photoluminescence of active RE3+ ions. However, energy transfer between sensitizers and activators usually induces nonradiative migration depletion that brings detrimental luminescent quenching. Here, a transparent framework is employed to assemble ordered RE3+‐doped emitters to extend the emission spectral range by extracting photons from a variety of RE3+ ions with sequential energy gradient. To block migration‐mediated depletion between different RE3+ ions, a nanoscopic heterogeneous architecture is constructed to spatially confine the RE3+ clusters via a "nanocrystals‐in‐glass composite" (NGC) structure. This bottom‐up strategy endows the obtained RE3+‐doped NGC with high emission intensity (nearly one order of magnitude enhancement) and broadband near‐infrared emission from 1300 to 1600 nm, which covers nearly the whole low‐loss optical communication window. Most crucially, NGC is a versatile approach to design tunable broadband emission for the potential applications in high‐performance photonic devices, which also provides new opportunities for engineering multifunctional materials by integration and manipulation of diverse functional building units in a nanoscopic region. A tunable broadband emission is demonstrated by assembly of ordered rare‐earth‐doped emitters with sequential energy gradient. Migration‐mediated energy quenching has been successfully suppressed by nanoscopic heterogeneous structures constructed in transparent nanocrystals‐in‐glass composites. This assembly strategy highlights the possibility to fabricate multifunctional materials by linking different building units with photonic, magnetic, and electronic properties in a transparent framework. [ABSTRACT FROM AUTHOR]

Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8-1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. [ABSTRACT FROM AUTHOR]

Rare earth doped mid-infrared (MIR) fluorescent sources have been widely investigated due to their various potential applications in the fields of communication, chemical detecting, medical surgery and so forth. However, with emission wavelength extended to MIR, multiphonon relaxation process that strongly quenched the MIR emission is one of the greatest challenges for such practical applications. In our design, we have described a controllable gas-aided annealing strategy to modulate the phase, crystal size, morphology and fluorescent performance of a material simultaneously. Uniform and monodispersed Er3+-doped La2O2S and La2O2SO4 nanocrystals with a similar lattice structure, crystallinity, diameter and morphology have been introduced to investigate the impact of multiphonon relaxation on luminescence performance. Detailed spectroscopic evolutions in the region of MIR, near-infrared (NIR), visible upconversion (UC) and their corresponding decay times provide insight investigation into the fluorescent mechanism caused by multiphonon relaxation. A possible energy transfer model has also been established. Our results present direct observation and mechanistic investigation of fluorescent evolution in multiphonon relaxation process, which is conductive to design MIR fluorescent materials in the future. To the best of our knowledge, it is the first investigation on MIR fluorescent performance of La2O2S nanocrystals, which may find various applications in many photoelectronic fields. [ABSTRACT FROM AUTHOR]