Search

Broadband near-infrared (NIR) light sources present attractive opportunities for potential applications in high-capacity telecommunication, temperature sensing, energy conversion, and NIR spectroscopy. While significant effort has been spent on materials doped with rare-earth and transition-metal ions, the achievement of these materials with ultrabroadband NIR emission and desired wavelength region remains a long-standing challenge, especially operating in the spectral region between 700 and 1300 nm. Here, such emission is developed in tellurium (Te) cluster-doped silicate glass for the first time. Furthermore, the mechanism of the NIR luminescence due to D2h-symmetric tetratellurium (Te4) clusters is identified by density functional theory (DFT) calculations. For intense luminescence, a model for the generation and stabilization of Te clusters by tailoring topological cages via adjustment of the Na2O and Al2O3contents and by optimizing the content of the dopant is proposed. Various stable Te clusters embedded into glass exhibit intense visible (Vis) to NIR broadband luminescence (400–1300 nm) with a spectral gap of 900 nm. In a demonstration experiment, a light-emitting diode (LED) device is fabricated from Te cluster-doped glass. This study opens a new opportunity for Te cluster-doped glass as a broadband NIR light source for spectroscopy applications.

Tunable light sources are highly anticipated for a variety of advanced applications. Precipitation of optically active centers in glass is an effective way to tune the optical properties of luminescent materials. However, it is challenging to obtain such stable precipitates at the subnanoscale in glass to obtain broad-band luminescence. Here, we show that stable subnanometric (<2 nm) tellurium (Te) clusters in TeO2-doped glasses can be generated directly by melt quenching. Density functional theory (DFT) was applied to calculate the energy levels of Tenclusters and thereby predict the luminescent behavior. On the basis of the DFT calculations, we designed a series of Te-doped germanate glass compositions which display broad-band luminescence. We propose the topological cage concept to tailor the cluster configuration and thus achieve tunable luminescence over a wide range of wavelengths from 600 to 1500 nm. Furthermore, the mechanism of Te luminescence in glasses is clarified in terms of cluster configurations defined by topological cages.

Long persistent phosphors (LPPs) with ultraviolet (UV) luminescence have great potential for application in the fields of biomedicine, environmental, and catalysis. However, it is currently limited by the design and development of remarkable UV LPPs with a suitable spectral region and an ultralong afterglow decay time. Herein, we develop a new type of Bi3+-activated LiScGeO4LPP, which exhibits bright ultraviolet-A (UVA) persistent luminescence (PersL). Because of the existence of numerous stabilized effective traps, the as-synthesized phosphors can undergo an ultralong PersL decay time far longer than 12 h. The PersL properties, effective trap depths, distributions, and types, as well as the possible mechanism for the PersL behavior of LiScGeO4:Bi3+, are comprehensively surveyed utilizing PersL excitation spectra, PersL decay analyses, thermoluminescence experiments, and X-ray photoelectron spectroscopy. This work can cover the shortage of LPPs in the UV region and also can lay the foundation for the development of more excellent UV LPPs toward versatile novel applications.

We report a narrow linewidth and low threshold single-frequency distributed Bragg reflector (DBR) fiber laser at 1120 nm based on a short 1.5 cm long Nd-doped silica fiber which, to the best of our knowledge, is the first demonstration of a Nd-doped fiber-based single-frequency fiber laser with a wavelength greater than 1100 nm. A stable single-longitudinal-mode laser operation with a signal-to-noise ratio greater than 67 dB was verified by a scanning Fabry–Perot interferometer. The laser threshold is as low as 10 mW. The DBR fiber laser has a maximum output power of 15 mW and optical-to-optical efficiency for the launched pump power reaches more than 8%. The narrow linewidth of 71.5 kHz is obtained in such a single-frequency fiber laser (SFFL). Our result is expected to offer an exciting new opportunity to realize high-performance SFFLs above 1100 nm.

Bi3+-activated photonic materials have received increased interest recently because they can be excited effectively with near-ultraviolet (NUV) but not visible light, thereby avoiding the reabsorption among phosphors, which cannot be solved intrinsically by traditional rare earth (e.g., Eu2+, Ce3+) phosphors. Such unique property suggests their potential application in NUV chip-based WLEDs. However, few Bi3+phosphors exhibit strong excitation peak in NUV, though the excitation tail of some can extend to NUV. Herein, we report a novel yellow-emitting La3BWO9:Bi3+(LBW:Bi3+) phosphor with strong NUV excitation. The photoluminescence (PL) spectroscopy analysis indicates that there are two Bi3+luminescent centers in LBW:Bi3+phosphor, which is clearly in contradiction with the established hexagonal structure of La3BWO9with P63space group because only one La site in this structure can accommodate Bi3+ions. Combining the luminescent properties of Bi3+with Rietveld refinement, La3BWO9was redefined as a trigonal structure with the lower space group of P3 in which there are two independent crystallographic La sites. In addition, the rationalization of P3 space group was further confirmed by the finding of the reflection (0001) according to the extinction rule. Therefore, the PL behavior of Bi3+can act as a complementary tool to determinate the real crystal structure especially when it is hard to distinguish by conventional X-ray diffraction techniques.

Bismuth (Bi)-doped materials are a new family of laser materials, and they usually exhibit extremely broad near-infrared (NIR) luminescence in 1000–1700 nm. Therefore, they can be utilized for a new generation of ultra-broadband tunable laser sources and ultra-broadband fiber amplifier. The broadband characteristics of Bi-active NIR luminescence can meet the needs of special wavelength laser sources that rare-earth-doped lasers cannot provide. However, at present, the Bi-doped NIR luminescence materials are mainly concentrated on glass, while Bi-doped NIR luminescence laser crystals are rarely reported. In this work, a novel Bi-doped crystal Sr_2B_5O_9Cl:Bi is reported with NIR luminescence, which exhibits broadband absorption in ultraviolet and visible regions, and can produce ultra-broadband from red to NIR luminescence covering 600–1600 nm. The results of excitation, emission spectra, and fluorescence lifetime show that the Sr_2B_5O_9Cl:Bi crystal contains three different Bi-active NIR emission centers. This work could enrich our understanding on Bi NIR emission behaviors in crystals. And this material provides a possibility for the development of a new laser source.

The fiber laser in the range of 900–1000 nm is essential to generate the blue fiber laser through frequency doubling for the laser display, laser underwater communications, and laser lighting. Yet, the well-developed three-level Yb-doped fiber laser can only realize the blue-green fiber laser at around 490 nm, which is far from the pure blue area (450 nm). To further achieve the pure blue fiber laser, the Nd-doped fiber has emerged as a proper choice to realize a shorter wavelength laser (<920  nm) through the F_3/24→I_9/24 transition of Nd^3+. Here, based on the facile “melt-in-tube” (MIT) method, a novel Nd-doped high alumina and yttria glass @ silica glass hybrid fiber was successfully prepared using the Nd:YAG crystal as the precursor core. The crystal core converts to the amorphous glass state after the drawing process, as evidenced by Raman spectra. The gain coefficient at 915 nm of the hybrid fiber reaches 0.4 dB/cm. Further, the laser oscillation at 915 nm with over 50 dB signal-to-noise ratio was realized by a short 3.5 cm gain fiber. Our results indicate that MIT is a feasible strategy to produce novel fiber for generating fiber laser at special wavelengths.

Computer tomography (CT) and magnetic resonance imaging (MRI) are noninvasive cancer imaging methods in clinics. Hence, a material that enables MRI/CT dual-modal imaging-guided therapy is in high demand. Currently, the available materials lack active tumor targeting, deep tumor penetration, and ultralong tumor retention and may lose their imaging elements. To overcome these drawbacks, herein, nanoparticles (NPs) were developed by integrating an MRI contrast-enhancing chelated gadolinium (Gd) complex within a doxorubicin (DOX)-loaded protective silica shell as well as a CT imaging/photothermal biocompatible bismuth (Bi) nano-core, which surface-displayed an MCF-7 breast tumor-homing peptide (AREYGTRFSLIGGYR, termed AR); we found that the resultant NPs AR-Bi@SiO2-Gd/DOX could home to and penetrate deep into the tumors with the unexpected ultralong retention of at least 14 days (as determined by CT/MRI imaging) and the tumor retention half-life of 104.5 h (as determined by ICP-MS analysis) under the guidance of the AR peptide. These NPs can be further used to image tumors with significantly increased sharp contrasts viaboth CT and MRI, which are much better than the commercial standard contrast agents; moreover, they significantly inhibit tumor growth viathe synergistic action of both Bi-enabled photothermal therapy and DOX-induced chemotherapy. The NPs are cleared by the spleen, liver and kidney and then excreted from the body along with faeces and urine. The precise tumor targeting and ultralong tumor retention of these unique NPs would enable both precise tumor detection for early diagnosis and signal-persistent tumor tracking for monitoring the treatment with only a single injection of these NPs.

Narrow band red-emitting Mn4+-doped fluoride phosphor is an essential red component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6compound crystallizes in the orthorhombic crystal system with space group Pbcm(No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+emits intense red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ion in Cs2GeF6, Na2GeF6, and CsNaGeF6are calculated using the exchange charge model of crystal-field theory. The local Mn4+environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+phosphor as the red component. Our results not only reveal that a high-performance Mn4+red phosphor is achieved through cationic substitutions but also construct a relationship of performance–structure to guide the design of Mn4+phosphors in the future.

We report an unusual thermal response of tellurium (Te) near-infrared (NIR) luminescence in phosphate laser glass, where the luminescence first increases and then decreases with heat-treatment temperatures increasing from 250°C to the glass transition temperature (T_g). This is followed by a distinct revival of Te NIR luminescence at temperatures above T_g. This result differs from the scenario in conventional rare-earth (Er^3+, Nd^3+, and Yb^3+)-doped phosphate glasses, where the rare-earth NIR emission decreases with increasing heat-treatment temperature. The difference may originate from conversion between Te_4 and other Te species, which depends on the evolution of the glass structure and molecular motion during the reheating processes, leading to unusual thermal response of Te NIR luminescence. The increase in Te_4 clusters enhances Te NIR emission, indicating that Te NIR luminescence is assigned to the Te_4 cluster, in contrast to previous studies. Heating and cooling cycles between 50°C and 250°C reveal strong dependence of the thermal degradation on glass structure. Te-doped phosphate laser glass with zero thermal degradation can be realized by stabilizing NIR luminescence center Te_4 by adjusting the glass structure with reduced network crosslinking. The superior optical performance has been confirmed in our previous study that the NIR luminescence properties can be well maintained in Te-doped fiber. The findings indicate that Te-doped phosphate glass with unusual thermal responses can potentially be used in fiber laser devices.

Knowledge of site occupation of activators in phosphors is of essential importance for understanding and tailoring their luminescence properties by modifying the host composition. Relative site preference of Eu2+for the two distinct types of alkaline earth (AE) sites in Ba1.9995–xSrxEu0.0005SiO4(x= 0–1.9) is investigated based on photoluminescence measurements at low temperature. We found that Eu2+prefers to be at the 9-coordinated AE2 site at x= 0, 0.5, and 1.0, while at x= 1.5 and 1.9, it also occupies the 10-coordinated AE1 site with comparable preference, which is verified by density functional theory (DFT) calculations. Moreover, by combining low-temperature measurements of the heat capacity, the host band gap, and the Eu2+4f7ground level position, the improved thermal stability of Eu2+luminescence in the intermediate composition (x= 1.0) is interpreted as due to an enlarged energy gap between the emitting 5d level and the bottom of the host conduction band (CB), which results in a decreased nonradiative probability of thermal ionization of the 5d electron into the host CB. Radioluminescence properties of the samples under X-ray excitation are finally evaluated, suggesting a great potential scintillator application of the compound in the intermediate composition.

Mechanoluminescent (ML) materials are mechano-optical converters that can emit light under an external mechanical stimulus. All the existing ML materials can only emit light from near ultraviolet to red, which is outside the near-infrared (NIR) windows desired for biomechanical imaging. No studies have been done on doping rare earth (RE) ions with photoluminescence (PL) in the NIR region into a compound to form a ML material that emits NIR light in response to an external force. Here, we show that doping RE ions with a NIR PL into an inorganic compound does not usually result in the formation of a NIR ML material, which can only be achieved in the combination of Nd3+ions and a CaZnOS compound among the combinations we studied. The newly discovered NIR ML material (CaZnOS:Nd3+) is biocompatible and can efficiently convert mechanical stress into NIR light over the first and second tissue-penetrating bioimaging window. Its NIR ML emission appeared at a very low force threshold (even when the material was shaken slightly), increased sensitively and linearly with the increase in the force (up to >5 kN), and could penetrate the tissue as deep as >22 mm to enable biomechanical detection. Such a force-responsive behavior is highly reproducible. Hence, CaZnOS:Nd3+is a new potential ultrasensitive biomechanical probe and expands the ML application horizons into in vivo bioimaging.

The Earth’s magnetic field has significant effects that protect us from cosmic radiation and provide navigation for biological migration. However, slow temporal variations originating in the liquid outer core invariably exist. To understand the working mechanism of the geomagnetic field and improve accuracy of navigation systems, a high-precision magnetometer is essential to measure the absolute magnetic field. A helium optically pumping magnetometer is an advanced approach, but its sensitivity and accuracy are directly limited by the low-frequency relative intensity noise and frequency stability characteristics of a light source. Here, we demonstrate a near quantum-noise limited and absolute frequency stabilized 1083 nm single-frequency fiber laser. The relative intensity noise is only 5 dB higher than the quantum-noise limit, and the root mean square of frequency fluctuation is ∼17  kHz after locked. This fiber laser could suppress the fluctuation of magnetic resonant frequency and improve the signal-to-noise ratio of the magnetic resonance signal detection.

The resistance to thermal quenching is an essential factor in evaluating the performance of luminescent materials for application in white light emitting diodes (WLEDs). In this work, we studied the site occupancy preference and thermal quenching of luminescence in β-Ca2P2O7:Bi2+red phosphor at low (10–300 K) and high temperatures (303–573 K). In β-Ca2P2O7, the host lattice has four different calcium sites, at which Bi2+dopant can be located. After comparing the change of bond energy when the Bi2+ions are incorporated into the four calcium sites, we found out that Bi2+would preferentially occupy the smaller energy variation sites Ci(2) and Ci(1) in this compound, which can be assigned to Bi(2) and Bi(1), respectively. Surprisingly, we noticed that the variation of emission intensity is different under different excitations when the temperature changes from 10 to 300 K. When exciting into the typical absorption of Bi(1) sites at 419 nm, the emission intensity at 300 K remains only 38% as compared to that at 10 K, while exciting into typical Bi(2) absorption at 460 nm, the emission intensity increases to 110%. When further increasing the temperature from 303 to 573 K, we observed a similar phenomenon, and the emission at 460 nm excitation starts to quench at 453 K. The emission intensity at 573 K still remains 86.1% of that at 303 K. This might be attributed to the Bi(2) → Bi(1) energy transfer. It is also evidenced by the time-resolved emission spectra and lifetime values. This work gives new insights into better understanding luminescent behaviors of Bi2+-doped materials with multiple cation sites. This should be helpful in the future when designing the bismuth doped phosphor for WLEDs with better resistance to thermal quenching.

Following pioneering work, solution-processable Mn4+-activated fluoride pigments, such as A2BF6(A = Na, K, Rb, Cs; A2= Ba, Zn; B = Si, Ge, Ti, Zr, Sn), have attracted considerable attention as highly promising red phosphors for warm white light-emitting diodes (W-LEDs). To date, these fluoride pigments have been synthesized via traditional chemical routes with HF solution. However, in addition to the possible dangers of hypertoxic HF, the uncontrolled precipitation of fluorides and the extensive processing steps produce large morphological variations, resulting in a wide variation in the LED performance of the resulting devices, which hampers their prospects for practical applications. Here, we demonstrate a prototype W-LED with K3AlF6:Mn4+as the red light component via an efficient and water-processable cation-exchange green route. The prototype already shows an efficient luminous efficacy (LE) beyond 190 lm/W, along with an excellent color rendering index (Ra = 84) and a lower correlated color temperature (CCT = 3665 K). We find that the Mn4+ions at the distorted octahedral sites in K3AlF6:Mn4+can produce a high photoluminescence thermal and color stability, and higher quantum efficiency (QE) (internal QE (IQE) of 88% and external QE (EQE) of 50.6%.) that are in turn responsible for the realization of a high LE by the warm W-LEDs. Our findings indicate that the water-processed K3AlF6may be a highly suitable candidate for fabricating high-performance warm W-LEDs.

Because of ultra-broadband luminescence in 1000–1700 nm and consequent applications in fiber amplifier and lasers in the new spectral range where traditional rare earth cannot work, bismuth-doped laser glasses have received rising interest recently. For long-term practical application, thermal degradation must be considered for the glasses. This, however, has seldom been investigated. Here we report the thermal degradation of bismuth-doped germanate glass. Heating and cooling cycle experiments at high temperature reveal strong dependence of the thermal degradation on glass compositions. Bismuth and tantalum lead to the reversible degradation, while lithium can produce permanent irreversible degradation. The degradation becomes worse as lithium content increases in the glass. Absorption spectra show this is due to partial oxidation of bismuth near-infrared emission center. Surprisingly, we notice the emission of bismuth exhibits blueshift, rather than redshift at a higher temperature, and the blueshift can be suppressed by increasing the lithium content.

In this work, we report the first fabrication of hierarchical nickel oxide nanosheet@nanowire arrays on nickel foam (NiO NS@NW/NF) through a hydrothermal process followed by annealing treatment. When directly used as a 3D anode for electro-oxidation of methanol in alkaline media, the NiO NS@NW/NF electrode exhibits high electrocatalytic activity and stability. It can afford a current density of 89 mA cm−2at 1.62 V (vs.RHE) in 1 M KOH with 0.5 M methanol.

The design of luminescent materials with widely and continuously tunable excitation and emission is still a challenge in the field of advanced optical applications. In this paper, we reported a Eu2+-doped SiO2-Li2O-SrO-Al2O3-K2O-P2O5(abbreviated as SLSAKP:Eu2+) silicate luminescent glass. Interestingly, it can give an intense tunable emission from cyan (474 nm) to yellowish-green (538 nm) simply by changing excitation wavelength and adjusting the concentration of Eu2+ions. The absorption spectra, photoluminescence excitation (PLE) and emission (PL) spectra, and decay curves reveal that there are rich and distinguishable local cation sites in SLSAKP glasses and that Eu2+ions show preferable site distribution at different concentrations, which offer the possibility to engineer the local site environment available for Eu2+ions. Luminescent glasses based color and white LED devices were successfully fabricated by combining the as-synthesized glass and a 385 nm n-UV LED or 450 nm blue LED chip, which demonstrates the potential application of the site engineering of luminescent glasses in advanced solid-state lighting in the future.

We report on a red-emitting ScVO4:Bi3+phosphor which does not show excitation at energies below 2.88 eV (430 nm). X-ray diffraction, time-resolved, and quantitative photoluminescence (PL) spectroscopy were employed to characterize relations between crystal structure and luminescence properties of the material. Results show that incorporation of Bi3+renders the blue photoemission of blank ScVO4to red. Dynamic luminescence analysis between 10 and 300 K reveals a complicated dependence of energy transfer from VO43–groups to Bi3+ions and population redistribution of 3P1and 3P0of Bi3+on temperature. This reflects in distinct changes in the luminescence decay functions. That is, a dramatic decrease of Bi3+luminescence lifetime occurs from hundreds to only several microseconds. Density functional theory is employed to reveal how the unusual red Bi3+luminescence comes, and results indicate that the perturbation of oxygen vacancies which is generated readily when bismuth precipitates into ScVO4is the reason for the experimental observation, although the vacancies themselves do not show photoluminescence. Upon excitations at 330 and 380 nm, internal quantum efficiencies can be up to ∼56% and ∼47%, respectively, implying the potential application of the red phosphor in warm-white-light-emitting diodes. As a proof of concept, an exemplary device was developed by combining the present phosphor with an ultraviolet-light-emitting diode and a commercial phosphor (Ba, Eu)MgAl10O17:Mn. We obtain a color rendering index (CRI) of >90 and a color temperature of ∼4306 K at chromaticity (0.3744, 0.3991).

Using conventional melt-quenching and subsequent thermal treatment, Er^3+ doped CaF_2 transparent glass ceramic (GC) was prepared. X-ray diffraction and high-resolution transmission electron microscopy confirmed the formation and microstructure of CaF_2 nanocrystals in glass. An energy-dispersive spectrometer was used to investigate the distribution of Er^3+ ions and CaF_2 nanocrystals in glass. It was found that Er^3+ ions prefer to concentrate in the CaF_2 nanocrystals rather than in a glass matrix, and the amount of Er^3+ ions plays a key role in the formation of CaF_2 nanocrystals in a glass matrix with the Er^3+ ions as nucleating agent. An intense 2.7 μm emission due to Er^3+: I_11/24→I_13/24 was achieved upon excitation at 980 nm with a laser diode, while the 2.7 μm emission can be neglected in the as-prepared glass counterpart, which confirmed the incorporation of Er^3+ ions into CaF_2 nanocrystals. An obvious enhancement of 2.7 μm emerged in the GC doped with 3% Er^3+ and heat-treated at 620°C.

Structural design of photocatalysts is of great technological importance for practical applications. A rational design of architecture can not only promote the synthetic performance of photocatalysts but also bring convenience in their application procedure. Nanofibers have been established as one of the most ideal architectures of photocatalysts. However, simultaneous optimization of the photocatalytic efficiency, mechanical strength, and thermal/chemical tolerance of nanofibrous photocatalysts remains a big challenge. Here, we demonstrate a novel design of TiO2–SiO2composite fiber as an efficient photocatalyst with excellent synthetic performance. Core–shell mesoporous SiO2fiber with high flexibility was employed as the backbone for supporting ultrasmall TiO2nanowhiskers of the anatase phase, constructing core@double-shell fiber with luffa-sponge-like appearance. Benefitting from their continuously long fibrous morphology, highly porous structure, and completely inorganic nature, the TiO2–SiO2composite fibers simultaneously possess high photocatalytic reactivity, good flexibility, and excellent thermal and chemical stability. This novel architecture of TiO2–SiO2glass composite fiber may find extensive use in the environment remediation applications.

Abstract

A novel high efficiency red emitting Sr2MgAl22O36:Mn4+ phosphor is synthesized by solid-state reaction method. The optimized red emitting Sr2MgAl22O36:Mn4+ phosphor exhibits high quantum efficiency (QE) of [?]80%, fluorescence lifetime of [?]1.25 ms and the Commission International de I'Eclairage (CIE) chromaticity coordinates (0.72, 0.27). The Sr2MgAl22O36:Mn4+ phosphor shows excitation bands at [?]400 and 470 nm which matches well with working wavelength of existed LED chips can be used as excitation source to generate white emission. White LED was fabricated by using mixed phosphors Sr2MgAl22O36:Mn4+ and (Sr, Ba)2SiO4:Eu2+ (green emitting phosphor) excited with a 397 nm near UV-chip.

A significant broad-bandwidth near-shot-noise-limited intensity noise suppression of a single-frequency fiber laser is demonstrated based on a semiconductor optical amplifier (SOA) with optoelectronic feedback. By exploiting the gain saturation effect of the SOA and the intensity feedback loop, a maximum noise suppression of over 50 dB around the relaxation oscillation frequencies and a suppression bandwidth of up to 50 MHz are obtained. The relative intensity noise of −150  dB/Hz in the frequency range from 0.8 kHz to 50 MHz is achieved, which approaches the shot-noise limit. The obtained optical signal-to-noise ratio is more than 70 dB. This near-shot-noise-limited laser source shows important implications for the advanced fields of high-precision frequency stabilization, quantum key distribution, and gravitational wave detection.

The reduction of Eu3+ to Eu2+ in air has been observed in a silicate matrix for the first time in BaMgSiO₄∶Eu prepared by high-temperature solid-state reaction. Emission and excitation spectra were employed to detect the presence of Eu2+ ions in the compound and this reduction was explained by a charge compensation model proposed previously. In BaMgSiO₄∶Eu2+, Eu2+ ions occupy three different lattice sites by substitution for Ba2+ ions. Eu2+ ions on Ba(1) and Ba(2) sites gave emissions at about 500 nm while that on Ba(3) site showed an emission band at 398 nm. All the emissions of Eu2+ ions in BaMgSiO₄∶Eu2+ were not quenched at room temperature.

The reduction of Eu3to Eu2in air has been observed in a silicate matrix for the first time in BaMgSiO4Eu prepared by high-temperature solid-state reaction. Emission and excitation spectra were employed to detect the presence of Eu2ions in the compound and this reduction was explained by a charge compensation model proposed previously. In BaMgSiO4Eu2, Eu2ions occupy three different lattice sites by substitution for Ba2ions. Eu2ions on Ba1 and Ba2 sites gave emissions at about 500 nm while that on Ba3 site showed an emission band at 398 nm. All the emissions of Eu2ions in BaMgSiO4Eu2were not quenched at room temperature.

Triple‐negative breast cancer (TNBC) exhibits aggressive behavior and high levels of metastasis owing to its complex heterogeneous structure and lack of specific receptors. Here, tumor cell membrane (CM)‐coated bismuth/manganese oxide nanoparticles (NPs) with high indocyanine green (ICG) payload up to 50.6 wt% (mBMNI NPs) for targeted TNBC therapy are constructed. The extra‐high drug load Bi@Bi2O3@MnOxNPs (honey‐comb like structure) are formed by Kirkendall effect and electrostatic attraction. After modified with CM, they can home into tumor sites precisely, where they respond to internal overexpressed glutathione (GSH), releasing Mn2+for chemodynamic therapy (CDT) with GSH depletion, while H2O2degrades into O2enabling relief of tumor hypoxia. In response to external near‐infrared irradiation, mBMNI NPs intelligently generate vigorous heat and single oxygen (1O2) for photothermal therapy (PTT) and photodynamic therapy (PDT) owing to high load. Importantly, O2production and GSH consumption during the internal response reinforce external PDT, while the heat generated through PTT during the external response promotes internal CDT. The honeycomb‐like structure with high ICG load and mutual reinforcement between internal and external response results in excellent therapeutic effects against TNBC. This work represents a biomimetic honeycomb‐like nanoparticle which exhibits high indocyanine green payload (50.6 wt%), enables homologous targeted ability and establishes a mutually reinforcing mechanism between internal tumor microenvironment responses (H2O2for O2generation, glutathione for chemodynamic therapy) and external response (photothermal and photodynamic therapy) for triple‐negative breast cancer therapy. In addition, the formation mechanism of honeycomb‐like structure is proposed.

Bismuth (Bi)-activated luminescence materials have attracted much attention for their tunable broad emissions ranging from a visible to near-infrared (NIR) region. However, it remains a challenge to regulate the Bi valence state and achieve NIR emission via a facile way. Here, we report the design and preparation of Ba3Sc4O9:Bi phosphors, which emit visible and NIR emissions simultaneously even prepared in the air condition. The self-reduction mechanism of Bi3+species in Ba3Sc4O9with a rigid crystal structure is illustrated based on the charge compensation model, and the coexistence of different Bi-active centers, Bi3+for visible emission, while Bi+and Bi0for NIR emission, is confirmed by the spectroscopic data and X-ray photoelectron spectroscopy (XPS) analysis. The enhanced NIR emission was further achieved through controlled reducing treatment and the related mechanism has also been clarified. This work paves a new way to control bismuth valence and tune the emission of Bi-based luminescence materials for emerging photonics applications.

We present a low noise single-frequency and single-polarization distributed Bragg reflector fiber laser at 1083 nm by using a 1.8 cm long newly developed ytterbium-doped phosphate single mode glass fiber. The maximum output power is more than 100 mW with a slope efficiency of >29.6%. The signal to noise ratio is higher than 61 dB and the laser linewidth of less than 2 kHz is estimated. The obtained relative intensity noise for frequencies of over 4.0 MHz is less than −150  dB/Hz, which approaches the shot noise limit. The achieved linear polarization extinction ratio is more than 30 dB.

Ultrabroad near-infrared (NIR) photoluminescence from Ni^2+-centers in nanocrystalline Ba-Al titanate glass ceramics was studied by temperature-dependent static and dynamic photoluminescence spectroscopy in the regime of 10 to 300 K. Photoluminescence covers the spectral range of about 1100 nm to >1600??nm with a typical bandwidth (FWHM) greater than 300 nm. For UV-LED excitation at 352 nm, an internal quantum efficiency of 65% is obtained. The excited state lifetime τ at room temperature is 39 μs. The stimulated emission cross section σ_em is 8.5×10^−20??cm^2, resulting in a practical figure of merit, σ_em*τ, of 3.3×10^−24??cm^2?s at room temperature. These properties suggest suitability as a broadband gain medium for tunable lasers and optical amplifiers.

A compact, low-noise, single-frequency fiber laser by using a newly developed Yb^3+ heavily doped single-mode phosphate glass fiber has been demonstrated. Over 400?mW stable continuous wave single transverse and longitudinal mode laser at 1.06?μm was achieved from a 0.8?cm long active fiber. The measured slope efficiency and estimated quantum efficiency of laser emission are 72.7% and 93%, respectively. The signal-to-noise ratio is higher than 72?dB, and the linewidth of the fiber laser is less than 7?kHz, while the measured relative intensity noise is less than −130?dB/Hz at frequencies of over 1.5?MHz.

We report on photoluminescence of Sr_2P_2O_7:Bi^2+ as a potential red-emitting phosphor for multichromatic light sources. If excited with blue light, photoluminescence of this compound spans the spectral range of about 600 to 760nm. Static and dynamic spectral data reveal the presence of two distinct emission centers. Based on bond covalency and emission lifetime, luminescence can clearly be assigned to Bi^2+ ions on Sr(1) and Sr(2) lattice sites, respectively. Energy transfer is observed from Bi(1) to Bi(2). Transfer efficiency, estimated from the lifetimes of the excited states, increases with increasing dopant concentration.

We report on Bi^2+-doped SrB_4O_7 and SrB_6O_10 as orange and red phosphors for white-light-emitting diodes. In both compounds, absorption due to ^2P_1/2-->^2S_1/2 in Bi^2+ could be observed and quantified. The emission redshift from SrB_4O_7 to SrB_6O_10 and their different phonon satellite spectra are attributed to the enhancement of phonon-electron interaction. Investigation of the reduction mechanism of Bi^3+ to Bi^2+ suggests that in oxidizing atmosphere, Bi^2+ can be stabilized on Sr^2+ sites only in such lattices that are dominated by tetrahedrally coordinated boron.

We report all-solid bandgap-guiding fibers formed by pumping molten tellurite glass into silica-air photonic crystal fiber at high pressure. The spectral positions of the guidance bands agree well with multipole simulations and bandgap calculations. The micrometer-diameter tellurite strands are found to contain microheterogeneities (most probably originating from devitrification), which increase the fiber attenuation, although no evidence of crystallization is seen in the bulk tellurite glass. The technique offers a potential route to employing difficult-to-handle glasses, or glasses unsuitable for fiber drawing, in fiber-based amplifiers, modulators, filters, and nonlinear devices.

Smart materials which are capable of responding to external stimuli such as strain, temperature, electronic or magnetic fields have seen increasing demand from various fields of application. Mechanoluminescence (ML) is light emission phenomenon induced by external mechanical stimuli, which is often used to monitor and record the action of invisible forces in visible space. However, existing ML materials with limited spectral window has largely limited its applications. Extending ML operation to UV or near-infrared (NIR) regions would overcome this issue. In this work, materials with simultaneous visible to NIR ML is realized based on rare-earth (RE) ions doped CaZnOS, in particular, CaZnOS:Er3+demonstrates ML on multiple spectral bands, including 510–538 nm, 538–570 nm, 640–680 nm, 845–880 nm, 960–1000 nm and 1450–1700 nm. Insight on the origin of ML in CaZnOS:RE3+is discussed with the aid of in situhigh-pressure studies. These observations indicate that the oriented migration of electrons which can be modulated or accelerated in a strain-induced piezoelectric field is a key in ML process. This interpretation provides a new tool for leveraging tailored ML performance in the further design of strain- and force-responsive materials.

With the rapid development of precision measurements relying on atom absorption such as atomic inertial sensors and optical magnetometry, advanced lasers are urgently required especially ultralow-noise lasers corresponding to the atom absorption line. For the D2 line of rubidium atoms, an ultralow-intensity-noise 780 nm single-frequency fiber-based laser with an output power of 340 mW is demonstrated. By eliminating polarization sensitivity in the noise suppression process based on the gain saturation of a semiconductor optical amplifier, a relative intensity noise of ?151 dB Hz?1in the frequency range from 0.1 to 50 MHz is achieved, which approaches the shot noise limit.

Nd^3+-doped fiber lasers at around 900 nm based on the ^4F_3/2???^4I_9/2 transition have obtained much research attention since they can be used as the laser sources for generating pure blue fiber lasers through the frequency doubling. Here, an all-fiber laser at 915 nm was realized by polarization-maintaining Nd^3+-doped silica fiber. A net gain per unit length of up to 1.0 dB/cm at 915 nm was obtained from a 4.5 cm fiber, which to our best knowledge is the highest gain coefficient reported in this kind of silica fiber. The optical-to-optical conversion efficiency varies with the active fiber length and the reflectivity of the output fiber Bragg grating (FBG), presenting an optimal value of 5.3% at 5.1 cm fiber length and 70% reflectivity of the low reflection FBG. Additionally, the linear distributed Bragg reflector short cavity was constructed to explore its potential in realizing single-frequency 915 nm fiber laser. The measurement result of longitudinal-mode properties shows it is still multi-longitudinal mode laser operation with 40 mm laser cavity. These results indicate that the Nd^3+-doped silica fiber could be used to realize all-fiber laser at 915 nm, which presents potential to be the seed source of high-power fiber laser.

Near-infrared broadband emission from bismuth–tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260–1625 nm), with a maximum peak at ?1310?nm, a FWHM broader than 400 nm, and a lifetime longer than 200??s. The observed broadband luminescence was attributed to bismuth clusters in the glasses. Bismuth–tantalum-codoped germanium oxide glass might be promising as amplification media for broadly tunable lasers and wideband amplifiers in optical communications.

Broadband infrared luminescence from bismuth-doped germanium oxide glasses prepared by a conventional melting–quenching technique was discovered. The absorption spectrum of the glasses covered a wide range from the visible to the near-infrared wavelength regions and consisted of five broad peaks below 370, 500, 700, 800, and 1000 nm. The fluorescence spectrum exhibited broadband characteristics (FWHM) greater than 300 nm with a maximum at 1300 nm pumped by an 808-nm laser. The fluorescence lifetime at room temperature decreased with increasing Bi_2O_3 concentration in the glass. Codoping of aluminum and bismuth was indispensable for the broadband infrared luminescence in GeO_2:Bi, Al glass.

Despite its 5‐year event‐free survival rate increasing to 60–65% due to surgery and chemotherapy, osteosarcoma (OS) remains one of the most threatening malignant human tumors, especially in young patients. Therefore, a new approach that combines early diagnosis with efficient tumor eradication and bioimaging is urgently needed. Here, a new type of mesoporous silica–coated bismuth sulfide nanoparticles (Bi2S3@MSN NPs) is developed. The well distributed mesoporous pores and large surface areas hold great promise for drug protection and encapsulation (doxorubicin (DOX), 99.85%). Moreover, the high photothermal efficiency of Bi2S3@MSNs (36.62%) offers great possibility for cancer synergistic treatment and highly near‐infrared‐triggered drug release (even at an ultralow power density of 0.3 W cm−2). After covalently conjugated to arginine‐glycine‐aspartic acid (RGD) peptide [c(RGDyC)], the NPs exhibit a high specificity for osteosarcoma and finally accumulate in the tumor cells (tenfold more than peritumoral tissues) for computed tomography (CT) imaging and tumor ablation. Importantly, the synergistic photothermal therapy–chemotherapy of the RGD–Bi2S3@MSN/DOX significantly ablates the highly malignant OS. It is further proved that the superior combined killing effect is achieved by activating the mitochondrial apoptosis pathway. Hence, the smart RGD–Bi2S3@MSN/DOX theranostic platform is a promising candidate for future applications in CT monitoring and synergistic treatment of malignant tumors. A smart near‐infrared responsive and osteosarcoma‐targeted theranostic platformbased on arginine‐glycine‐aspartic acid (RGD)–mesoporous silica–coated bismuth sulfide nanoparticles (Bi2S3@MSNs) is constructed. The unique synergistic photothermal therapy–chemotherapy of the RGD–Bi2S3@MSN/doxorubicin significantly ablates the highly malignant osteosarcoma. It is further proved that the superior combined killing effect is associated with elevated mitochondrial apoptosis pathway.

Bismuth (Bi)-doped laser glasses and fiber devices have aroused wide attentions due to their unique potential to work in the new spectral range of 1 to 1.8 μm traditional laser ions, such as rare earth, cannot reach. Current Bi-doped silica glass fibers have to be made by modified chemical vapor deposition at a temperature higher than 2000°C. This unavoidably leads to the tremendous loss of Bi by evaporation, since the temperature is several hundred degrees Celsius higher than the Bi boiling temperature, and, therefore, trace Bi (∼50??ppm) resides within the final product of silica fiber. So, the gain of such fiber is usually extremely low. One of the solutions is to make the fibers at a temperature much lower than the boiling temperature of Bi. The challenge for this is to find a lower melting point glass, which can stabilize Bi in the near infrared emission center and, meanwhile, does not lose glass transparency during fiber fabrication. None of previously reported Bi-doped multicomponent glasses can meet the prerequisite. Here, we, after hundreds of trials on optimization over glass components, activator content, melting temperature, etc., find a novel Bi-doped gallogermanate glass, which shows good tolerance to thermal impact and can accommodate a higher content of Bi. Consequently, we successfully manufacture the germanate fiber by a rod-in-tube technique at 850°C. The fiber exhibits similar luminescence to the bulk glass, and it shows saturated absorption at 808 nm rather than 980 nm as the incident power becomes higher than 4 W. Amplified spontaneous emissions are observed upon the pumps of either 980 or 1064 nm from germanate fiber.

We present a compact passively Q-switched single-frequency fiber laser based on a 12-mm-long laboratory-built highly Er3+/Yb3+codoped phosphate fiber (EYDPF) and a semiconductor saturable absorber mirror (SESAM). An effective cavity length of less than 20 mm ensures the stable single-frequency operation of the Q-switched fiber laser. By employing a SESAM for Q-switching, a single-pulse energy of more than 34.4 nJ is realized with the narrowest pulse duration of 95 ns, and the repetition rate of the Q-switched fiber laser reaches over 600 kHz. In addition, the optical signal-to-noise ratio of the output laser is as high as 68.0 dB.

A novel high efficiency red emitting Sr2MgAl22O36:Mn4+phosphor is synthesized by solid-state reaction method. The optimized red emitting Sr2MgAl22O36:Mn4+phosphor exhibits high quantum efficiency (QE) of ∼80%, fluorescence lifetime of ∼1.25 ms and the Commission International de I’Eclairage (CIE) chromaticity coordinates (0.72, 0.27). The Sr2MgAl22O36:Mn4+phosphor shows excitation bands at ∼400 and 470 nm which matches well with working wavelength of existed LED chips can be used as excitation source to generate white emission. White LED was fabricated by using mixed phosphors Sr2MgAl22O36:Mn4+and (Sr, Ba)2SiO4:Eu2+(green emitting phosphor) excited with a 397 nm near UV-chip.