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Large-mode-area anti-resonant fibers (LMA ARF) with high beam quality have the potential to revolutionize mid-infrared high-power laser delivery by mitigating mode instabilities and nonlinear degradation. However, their tens-of-microns mode field diameters and small numerical aperture significantly increase the mode field mismatch and coupling complexity, respectively. In this work, an LMA all-solid anti-resonant fiber-microlens with a robust operation of high beam quality in the mid-infrared region was designed and prepared. It can significantly stabilize the efficiencies of coupling and transmission at a large radial offset. Consequently, this AS-ARF demonstrates substantial potential for advancing mid-infrared laser power delivery via fiber, ensuring exceptional beam quality throughout the process. [ABSTRACT FROM AUTHOR]

Erbium-doped glass microsphere laser systems hold significant promise in the applications of bio-medicine and optical fiber sensing. However, their development has been hindered by the relatively high laser pump threshold. In this study, we proposed a unique dual microsphere system where two microspheres are affixed to a single-mode fiber taper and achieved a remarkably low lasing threshold of 19 μW for single-mode laser emission at 1544 nm. This is in sharp contrast with the lasing threshold of 56 μW observed in single microspheres. Our findings represent a significant achievement in the development of low-threshold, compact infrared laser sources for emerging applications in photonics. [ABSTRACT FROM AUTHOR]

In order to address the 'capacity crisis' caused by the narrow bandwidth of the current C band and the demand for wide-spectrum sensing sources and tunable fiber lasers, a broadband luminescence covering the C + L bands using Er3+/Yb3+ co-doped fluorotellurite glass fiber is investigated in this paper. The optimal doping concentrations in the glass host were determined based on the intensity, lifetime, and full width at half maximum (FWHM) of the fluorescence centered at 1.5 µm, which were found to be 1.5 mol% Er2O3 and 3 mol% Yb2O3. We also systematically investigated this in terms of optical absorption spectra, absorption and emission cross-sections, gain coefficients, Judd–Ofelt parameters, and up-conversion fluorescence. The energy transfer (ET) mechanism between the high concentrations of Er3+ and Yb3+ was summarized. In addition, a step-indexed fiber was prepared based on these fluorotellurite glasses, and a wide bandwidth of ~112.5 nm (covering the C + L bands from 1505.1 to 1617.6 nm) at 3 dB for the amplified spontaneous emission (ASE) spectra has been observed at a fiber length of 0.57 m, which is the widest bandwidth among all the reports based on tellurite glass. Therefore, this kind of Er3+/Yb3+ co-doped fluorotellurite glass fiber has great potential for developing broadband C + L band amplifiers, ultra-wide fiber sources for sensing, and tunable fiber lasers. [ABSTRACT FROM AUTHOR]

Solid electrolytes are promising candidates for addressing energy and environmental problems due to their excellent electrical conductivity and extremely high safety. To date, only a few alternative materials can meet the high ionic conductivity requirements of at least ≥1 mS cm−1 when using nontoxic and economical elements. For the first time, we report an Mn-doped sodium sulfide ion conductor Na3.24Mn0.08Sb0.92S4 that shows a maximum conductivity of 2.05 × 10−3 S cm−1 at 25 °C. In its sulfide superionic conductor structure, the antimony in the SbS43− cell is replaced with manganese with a low valence state, maintaining a good transport pathway and accelerating ion transport. This electrolyte exhibits good air stability in a humid environment and minimal H2S release. Moreover, its ionic conductivity is almost unchanged after the conductor is stored at room temperature for many days, which is crucial for promoting the development of sodium ion solid electrolytes. The stability of the conductor and sodium metal has also been evaluated, further studying its potential for practical applications. [ABSTRACT FROM AUTHOR]

The fabrication of all electrolytes from noncombustible ceramic materials offers a superior option for providing safer and higher-capacity batteries to fulfill future energy needs. To achieve a competitive performance with combustible liquid electrolytes used in commercial Li-ion batteries, the creation of ceramic material compositions with a high electrical conductivity is necessary. Here, we report that co-doping with W and halogens results in a superconductivity of 13.78 mS cm−1 in a cubic-phase Na3SbS4 glass ceramic electrolyte. After undergoing high-temperature heat treatments, the W ions in the electrolyte can facilitate the replacement of S atoms with halogens, introducing many Na vacancies. The samples also had a high degree of cycling stability. An excellent glass ceramic electrolyte for Na ion batteries will be constructed for Na3SbW0.25Cl0.25S4. [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]

Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot‐pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile. [ABSTRACT FROM AUTHOR]

Suspended graphene film is of great significance for building high-performance electrical devices. However, fabricating large-area suspended graphene film with good mechanical properties is still a challenge, especially for the chemical vapor deposition (CVD)-grown graphene films. In this work, the mechanical properties of suspended CVD-grown graphene film are investigated systematically for the first time. It is found that monolayer graphene film is hard to maintain on circular holes with a diameter of tens of micrometers, which can be improved greatly by increasing the layer of graphene films. The mechanical properties of CVD-grown multilayer graphene films suspended on a circular hole with a diameter of 70 µm can be increased by 20%, and multilayer graphene films prepared by layer-layer stacking process can be increased by up to 400% for the same size. The corresponding mechanism was also discussed in detail, which might pave the way for building high-performance electrical devices based on high-strength suspended graphene film. [ABSTRACT FROM AUTHOR]

Mid‐infrared (mid‐IR) on‐chip photonic devices have attracted increasing attention because of their potential applications in chemical and biological sensing and optical communications. In particular, chalcogenide glasses (ChGs) have long been regarded as promising materials for mid‐IR integrated photonics, owing to their broad infrared transparency, high nonlinearity, and excellent processing capabilities. Here, an inverse design approach is introduced to ChG photonic device design with a new robust inverse design method. A high‐performance mid‐IR inverse design polarization beam splitter, waveguide polarizer, mode converter, and wavelength demultiplexer are demonstrated for the first time. They all have a footprint of only several micrometers. The robust inverse design method could improve the robustness of device performance against fabrication variations and would be a general approach for designing and optimizing miniaturized chalcogenide photonic devices. [ABSTRACT FROM AUTHOR]

It is significantly important to modulate the electrical properties of graphene films through doping for building desired electronic devices. One of the effective doping methods is the chemical vapor deposition (CVD) of graphene films with heteroatom doping during the process, but this usually results in nitrogen-doped graphene with low doping levels, high defect density, and low carrier mobility. In this work, we developed a novel condensation-assisted CVD method for the synthesis of high-quality nitrogen-doped graphene (NG) films at low temperatures of 400 °C using solid 3,4,5-trichloropyridine as a carbon and nitrogen source. The condensation system was employed to reduce the volatilization of the solid source during the non-growth stage, which leads to a great improvement of quality of as-prepared NG films. Compared to the one synthesized using conventional CVD methods, the NG films synthesized using condensation-assisted CVD present extremely low defects with a ratio of from D- to G-peak intensity (ID/IG) in the Raman spectrum lower than 0.35. The corresponding total N content, graphitic nitrogen/total nitrogen ratio, and carrier mobility reach 3.2 at%, 67%, and 727 cm2V−1S−1, respectively. This improved condensation-assisted CVD method provides a facile and well-controlled approach for fabricating high-quality NG films, which would be very useful for building electronic devices with high electrical performance. [ABSTRACT FROM AUTHOR]

An amorphous superionic conductor is a promising solid electrolyte (SE) with excellent ionic conductivity and high energy density, which would be promising candidates for all‐solid‐state lithium‐ion batteries. However, these advantageous features alone are difficult to achieve large‐scale practical applications. Having a simple, effective synthetic route and good air stability is also critically important for SEs. Here, Li3PS4–xLiBr glass SE with high conductivity was obtained by simple mechanical milling and subsequent short‐term low‐temperature treatment. The site disorder between S2− and Br− anions facilitates ionic transport. Our comparison of air stability before and after doping with halogen revealed that Br− doping well reduced the production of H2S gas and improved the air stability of the SE. [ABSTRACT FROM AUTHOR]

High ionic conductivity, low grain boundary impedance, and stable electrochemical property have become the focus for all‐solid‐state lithium–sulfur batteries (ASSLSB). One of the approaches is to promote the rapid diffusion of lithium ions by regulating the chemical bond interactions within the framework. The structure control of P5+ substitution for Sn4+ on lithium‐ion transport was explored for a series of Li3PS4–Li4SnS4 glass–ceramic electrolytes. Results showed that the grain boundary impedance of the glass electrolyte was reduced after heat treatments. The formation of LiSnPS microcrystals, a good superionic conductor, was detected by X‐ray diffraction tests. Electrochemical experiments obtained the highest conductivity of 29.5 S cm−1 at 100°C and stable electrochemical window from –0.1 to 5 V at 25°C. In addition, the cell battery was assembled with prepared electrolyte, which is promoted as a candidate solid electrolyte material with improved performance for ASSLSB. [ABSTRACT FROM AUTHOR]

We report on the investigation of multi-pulse Tm3+-doped double clad fiber laser (TDCFL) with an ultra-compact four devices-based all-fiber structure. This multi-pulse is implemented by the long relaxation time of gain-switched process. The number of pulse in a pulse cluster can be tuned from 1 to 8 by changing the pump pulse energy. With laser cavity design (i.e. large laser output coupling ratio and high gain mutual balance), the multi-pulse laser can finally generate an average output power of 7.25 W with corresponding pulse energy of $362.5~\mu \text{J}$. The 2017 nm multi-pulse TDCFL has a high laser conversion efficiency of ~30% and the good operation stability with signal to noise ratio (SNR) of 77 dB. The experimental results would be fruitful to the communities interested in all-fiber multi-pulse lasers. [ABSTRACT FROM AUTHOR]

This work presents a gas-liquid sensor based on chalcogenide etched-tapered fiber (ETF) functionalized with graphene oxide film. Unlike the preparation of conventional tapered fiber sensors, the core diameter of the optical fiber of this gas-liquid sensor was kept constant, and part of its cladding was removed via the chemical corrosion method that the fiber optic modes were the invariant. The energy distribution of transmission mode in the original fiber and tapered fiber is simulated respectively, and obtained the conclusion that the tapered fiber structure has higher sensing sensitivity. The sensors could detect VOCs such as formaldehyde (HCOH) and butane (C4H10) in the mid-infrared band. Results showed that the ETF sensor had a high detection sensitivity of both HCOH solution (2.6731 a.u./mg·mL−1) and C4H10 gas (0.2773 a.u./vol.%). A layer of graphene oxide (GO) film was coated on the ETF to further improve the sensitivity of the sensor. The GO coated etched-tapered fiber (GO-ETF) sensor’ sensitivity was substantially improved owing to the strong hydrophilicity and biocompatibility of GO which can absorb bioactive molecules. The high detection sensitivity of both solution and gas were 4.5091 a.u./mg·mL−1 and 0.4812 a.u./vol.%, respectively, which were 1.69 and 1.74 times higher than that of the sensor without a coating of GO film. The results further showed that the sensor had a rapid response speed, low detection limit, good repeatability, and stability. [ABSTRACT FROM AUTHOR]

In this paper, a novel design of a 1×N multimode-interference power splitter is proposed and investigated. By using the finite difference time domain method and particle swarm optimization algorithm, our proposed 1×N optical power splitter can be optimized to realize compact size, good uniformity, low insertion loss, and broad bandwidth. To verify the effectiveness of this design, the designed 1×4 and 1×8 multimode-interference power splitters are experimentally demonstrated on an silicon-on-insulator platform. The lengths of the designed 1×4 and 1×8 power splitters are 36 μm and 47.8 μm, respectively. Experimental results show that, for the fabricated 1×4 power splitter, the uniformity ranges from 0.07 to 0.89 dB and the corresponding maximum insertion loss is 0.62 dB within a bandwidth from 1520 to 1624 nm. For the fabricated 1×8 power splitter, within a bandwidth from 1519 to 1623 nm, the uniformity varies from 0.19 to 0.83 dB and a maximum insertion loss of 0.64 dB are obtained. [ABSTRACT FROM AUTHOR]

A geometrical optimization study of Ge-Sb-Se chalcogenide glass tapered fiber sensors for concentration sensing of methanol is presented. The effects of the geometrical parameters such as taper waist diameter and transition region lengths on the evanescent wave penetration depth are discussed based on the ray-tracing theory. Numerical analysis results demonstrate that the performance of the tapered fiber sensor can be enhanced by decreasing the transition length of the down-taper combined with increasing the transition length of the up-taper. A homemade tapering platform enables controlling the taper waist diameter and transition region length of the tapered fiber accurately. An experimental study using tapered fiber sensors with different transition region lengths is carried out to detect the concentration of methanol aqueous solution. The highest sensitivity of 0.0120 a.u./% is obtained from the tapered fiber with a down-taper transition length of 5.4 mm and an up-taper transition length of 7.9 mm, which agrees with the trend presented by the simulation results. The effects of symmetric and asymmetric tapered fiber structure on the sensing characteristics are also investigated. [ABSTRACT FROM AUTHOR]

The acousto‐optic parameters of Ge10As90−xTex (x = 30, 40, 50, 60, 70 mol%) and Ge10As20Te70−ySey (y = 20, 30, 40, 50 mol%) glasses, were studied systematically to compare the pros and cons of Te‐based and Se‐based chalcogenide glasses in acousto‐optic performance, as well as the thermomechanical properties. In the Ge10As90−xTex system, the acousto‐optic figure of merit (M2) increased with increased Te content, and the maximum M2 of 2279 × 10−18 s3/g, which is 13 times that of commercial single‐crystal Ge, obtained in Ge10As20Te70 at 10.6 μm. However, its thermal properties and elastic modulus decreased and the acoustic attenuation (α) at different ultrasonic frequencies increased accordingly. In the Ge10As20Te70−ySey system, the thermomechanical performance of the glasses improved with the introduction of Se element, the overall α was lower than that of Te‐based chalcogenide glasses, and the minimum α was 5.29 dB/cm at 30 MHz ultrasonic frequency, although its M2 was inferior to that of Te‐based chalcogenide glasses. Additionally, the difference in the α of these glasses was smaller at low ultrasonic frequencies than at high ultrasonic frequencies. This work will promote the practical application of chalcogenide glasses as promising materials with outstanding acousto‐optic properties in low ultrasonic frequency acousto‐optic devices. [ABSTRACT FROM AUTHOR]

The translation matching method (TMM) was presented here to obtain the refractive index (RI) of chalcogenide films more accurately. It solved the problem of calculation errors of the RI of the film that resulted from using the Swanepoel method after conventional treatments such as illumination, electrical measurement, and annealing. The TMM was suitable for calculating the RI of the film by calibrating the transmission spectrum regardless of whether it had been dealt with. The accuracy of the RI calculation is about 0.1% using the method. Experimentally, the method was used to obtain the RI of three chalcogenide films: they are original homogeneous film and RI nonuniform film treated by annealing and by femtosecond laser direct writing, respectively. The results showed that the decrease in the transmittance and weakened interference effect were effectively overcome and the RI of the three kinds of films was accurately obtained by using the method. This work should provide a useful guideline for obtaining the RI of the transparent optical films. [ABSTRACT FROM AUTHOR]

We report high quality (Q) photonic crystal (PhC) nanobeam cavities in the chalcogenide glass Ge28Sb12Se60 near 1550 nm wavelength. By optimizing the structure of the PhC cavity, an ultra-high Q factor as large as 5 × 106 is predicted by simulation, and up to 1.2 × 104 is measured in the experiment. Such high-Q cavities in this strongly nonlinear material create an attractive platform for compact, ultrafast all-optical switches. [ABSTRACT FROM AUTHOR]

We present the development of an As2S3 fiber-based reusable inline optical connector; and, for the first time to the best of our knowledge, integrated it into a 2 μm chirped pulse amplification system as the pulse stretcher. By this mechanism, a near 20 times pulse stretching ratio was achieved in 0.5 m-long this As2S3 fiber and the introduction of insertion loss as low as 2.84 dB while it was connected with silica fiber. After the follow-up fiber amplification and self-compression mechanism, the laser average output power was boosted to 1.97 W and pulse duration was optimized to 2.53 ps. Moreover, to further inspect the laser pulse property, the pulses were then delivered into a 5.3 m-long ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber which was fusion spliced to SM1950 fiber. Thanks to the 0.4-dB low fusion splice loss between these fibers, a 1.56-W supercontinuum source with bandwidth of 1.93-3.50 μm is obtained. The measured two hours of root-mean-square value of power fluctuation of this laser source is 0.13%, indicating an ultra-high long-term power stability. This work will lay a solid foundation in the realization of the all-fiber structured high-power thulium-doped fiber amplifier with high compactness. [ABSTRACT FROM AUTHOR]

Chalcogenide glass (ChG) optical fibers have excellent transmission performance in the mid-infrared range, and microstructured devices prepared on ChG fibers play an important role in the field of infrared sensing and optical integration. In this study, high-quality chalcogenide optical fibers were prepared, and grating structures were produced on their end surfaces. An easy-to-use FC cable was first prepared and polished to high flatness with the surface roughness of less than 0.08 μm. 1- and 2-D diffraction gratings were then prepared on the end surfaces of the chalcogenide fibers via femtosecond laser line-by-line direct writing technology. The ChG fiber end surface gratings prepared with optimized femtosecond laser parameters exhibited high diffraction efficiency and clear diffraction pattern, indicating that they had excellent optical performance. The performance of the grating was tested by using a laser source with wavelengths covering the visible to the near-infrared regions. This measurement showed that the first-order diffraction efficiency of the grating on the end face could reach close to 50% at 1550 nm. [ABSTRACT FROM AUTHOR]

In this paper, a design of a silicon mode (de)multiplexer based on cascaded counter-tapered couplers is proposed and investigated. By using the particle swarm optimization algorithm and finite difference time domain method, structural parameters of each counter-tapered coupler in our proposed mode (de)multiplexer are optimized so that high conversion efficiencies can be obtained and coupling lengths can be significantly shortened. The coupling lengths of counter-tapered couplers in the proposed silicon four-mode (de)multiplexer operating in transverse-electric polarization are 8 μm, 9 μm, and 10 μm. The corresponding conversion efficiencies are respectively 98.98%, 99.98%, and 98.68%. Experimental results show that, the fabricated device exhibits a demultiplexed crosstalk of −32.76 dB, −27.10 dB, −32.45 dB, or −33.29 dB at 1550 nm wavelength, when the fundamental transverse-electric mode is respectively launched into the ports Input0, Input1, Input2, or Input3. The measured demultiplexed crosstalk is less than −15.15 dB from 1525 to 1596 nm and lower than −18.12 dB from 1525 to 1561 nm. [ABSTRACT FROM AUTHOR]

In this work, we successfully prepared gold nanoparticles (AuNPs) within a germanium–tin–sulfur (Ge–Sn–S, GSS) chalcogenide glass (ChG). The formation of AuNPs in the GSS ChG relies on the reduction capacity of Sn2+ ions, which we found their existence in the glass matrix by the characteristic emissions at nearly 450 nm. The AuNPs exhibit strong optical activity which caused a significant enhancement of third-order optical nonlinearity of the GSS ChG as well as photon luminescence of the Sn2+ ions. In addition, optical properties the AuNPs-embedded GSS ChGs can be modified by further gold doping and one-step heat-treatment process. [ABSTRACT FROM AUTHOR]

Ion‐conducting chalcogenide glass is a promising solid electrolyte with excellent conductivity and energy density for all‐solid‐state batteries. A suitable ionic channel for carriers in the amorphous network is urgently needed. In this work, the structural evolution of co‐doped metal cations (Ge and Ga) in the glass matrix and its influence on electrochemical behavior were studied using a series of GexGa16‐xSb64S128‐40AgI glass samples. The macroscopic properties of samples were examined by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Raman tests. The electrochemical behavior of samples was investigated by AC impendence spectroscopy and cyclic voltammetry (CV) measurement. Furthermore, a deliquescence experiment was applied for the chemical stability test of glass samples. The ionic conductivity of samples was developed by adding Ga components. Notably, the electrochemical window of electrolytes was remarkably wide at approximately 5 V. The resistance of samples to humidity was characterized by the decreased Raman peaks. Analysis results show that the Ga‐related bonding structure evidently increased the chemical stability compared with the non‐Ga sample. This work provides an insight into the effective and stable ions transport, especially in the Ge(Ga)SbS glass system. These results promote the further investigation of sulfide solid electrolytes and practical application of all‐solid‐state batteries. [ABSTRACT FROM AUTHOR]

In this article, a design of integrated flexible-grid mode- and wavelength-selective switch consisting of silicon-based symmetric Y-junctions and double-series coupled microring resonators with interferometric couplers is introduced in detail. Using thermal tuning, the described device is capable of routing each mode and wavelength signal from the input port to any output port flexibly and independently, forming different bandwidths as needed. For fixed field coupling coefficients, the device can support multiple different wavelength-channel spacings. A silicon-based flexible-grid 1 × 6 mode- and wavelength-selective switch is carefully designed and analyzed as an example. The designed device works for two mode channels and three wavelength channels. The wavelength-channel spacing can vary from 0.10 to 0.80 nm and the 3-dB bandwidth changes from 0.08 to 2.00 nm. When the wavelength-channel spacing is set to be 0.80 nm, the extinction ratio is greater than 50.90 dB and the crosstalk is less than −15.36 dB. [ABSTRACT FROM AUTHOR]

By conventional melt‐quenching techniques, a series of Dy3+‐doped (0.1 to 1.0 wt%) Ga5Ge20Sb15S60 bulk glasses were fabricated and their potential for developing mid‐infrared fiber laser beyond 4 μm were evaluated, in which the optimal Dy3+ doping concentration was found to be 0.3 wt% and the largest laser quality factor value (σe × τmea = 2.62 × 10−23 cm2 s) among all of the Dy3+‐doped chalcogenide glass was obtained. On this basis, through using the chemical purification methods with chlorine gas combined with the dynamic distillation process, the high‐purity GGSS glasses with low O–H and S–H absorptions were successfully fabricated, which was confirmed by the optimized mid‐infrared linear transmittance and improved fluorescent lifetimes of Dy3+: 6H13/2, 6H11/2 levels. Furthermore, for the first time to the best of our knowledge, the Dy3+‐doped, single‐mode, and double‐cladding chalcogenide fibers with the core/cladding ratios of 125:60:11 and 125:66:11.5 were achieved by a multistage rod‐in‐tube fiber drawing process and extrusion methods, respectively. The GeS2‐based fiber exhibits excellent transmission performance at 1.0‐5.0 μm: 3.0 dB/m at 2.9 μm (O–H), 2.4 dB/m at 4.1 μm (S–H). Combining the advantages of high‐purity, high doping concentration and single‐mode double‐cladding structure, the optimized active fiber should be an ideal efficient and low‐threshold medium toward mid‐infrared fiber laser beyond 4 μm. [ABSTRACT FROM AUTHOR]

A switchable polarization beam splitter utilizing GST-on-silicon waveguides is introduced and comprehensively investigated in this paper. Based on the phase matching and mode hybridization, structural parameters of the presented device are optimized by using the particle swarm optimization algorithm and finite difference time domain method, so that the output fundamental transverse-electric (TE0) and transverse-magnetic (TM0) modes can be switched by controlling the phase state of GST and the device exhibits broad bandwidth, low crosstalk, and high polarization extinction ratio. For the designed device with the amorphous GST, the crosstalk is lower than −23.40 dB and the polarization extinction ratio is larger than 21.35 dB over the C-band. In the case of the crystalline GST, within the C-band, the crosstalk of less than −27.37 dB and the polarization extinction ratio of greater than 21.37 dB are achieved. [ABSTRACT FROM AUTHOR]

The design of functional materials with tunable broadband luminescence performance is still of great interest in the fields of lighting, solar cells, tunable lasers, and optical amplifiers. Here, via a melt‐quenching method, a series of bismuth (Bi)‐doped germanium‐borate glasses with composition of 40GeO2–25B2O3–25Gd2O3–10La2O3–xBi2O3 have been prepared, in which multiple Bi active centers can be stabilized simultaneously. Dual‐modulating modes of visible (380‐750 nm) and near‐infrared (NIR) (1000‐1600 nm) broadband photoemissions were effectively controlled under flexible excitation scheme. Photoluminescence (PL) spectra at low temperature 10‐298 K were appropriately employed to interpret such an unusual wide visible emission band. To further illustrate the origin of NIR component, transmission electron microscopy (TEM) measurement was carried out. It is demonstrated experimentally that the visible emission mainly originates from the collective contribution of the 3P1/3P0→1S0 transitions of Bi3+, while the broadband NIR luminescence should be related to the formation of low valent Bi+ and (or) Bi0 centers. This work may help to enhance the knowledge of the complex luminescence mechanism for the Bi species and it also enables such transparent glass materials to be a promising candidate for the multifunctional tunable light source. [ABSTRACT FROM AUTHOR]

Ge–As–Se chalcogenide glasses were prepared and the surface damage characteristics under femtosecond laser irradiation were experimentally investigated. Femtosecond laser beams with different power intensities, focusing depths, pulse repetition rates, and pulse numbers were employed to determine the damage thresholds of the samples. The surface morphologies and feature sizes of the damage craters were studied with regard to laser energy density to evaluate the damage circumstances of the glasses. The generation of the surface damage was also recorded by using different numbers of pulses. Results showed that the damage area increased monotonically with the laser power at low energy density and tended to saturation when reaching a critical value. According to the linear circumstances of laser energy density on the damage crater area, the average damage thresholds of the Ge–As–Se glasses with different repetition rates and pulse numbers were obtained. Results showed that the damage threshold decreased with the increase in pulse repetition rate and number of pulse. [ABSTRACT FROM AUTHOR]

AgI‐based Ge–Sb–S, Ga–Sb–S, and Ge–Ga–Sb–S chalcogenide glasses were designed and prepared by melt‐quenching, thereafter their thermal properties and conductive performance were comparatively investigated on the basis of their composition‐induced network structures. Glass transition in each sample was examined by DSC measurements. Results showed that the samples containing Ge had a higher thermal stability than the Ga–Sb–S–AgI sample, and the Ge–Sb–S–AgI sample obtained had the highest conductivity ion. Raman spectrum analysis was performed, and the results indicated that the [GeS4‐xIx] structural units and [SbS3−xIx] pyramids in the matrix produced effective ion transport channel for dissolved conductive Ag+ ions. In the matrix containing Ga, the [Ga(Ge)S4‐xIx] structure was consumed by part of [S3Ga–GaS3] ethane‐like units, which had no contribution to the ion transition framework. The study provided the directions for composition and structure configuration control in effective conductive chalcogenide glasses. [ABSTRACT FROM AUTHOR]

This study reports on the synthesis of tellurium-based glasses that have a wide transmission far beyond the second atmospheric window. Several far-infrared(IR) transmitting glass systems including Ge-In-Te, Ge-Ga-Te, as well as some compositions containing alkali halides (KI, CsI) or metal halides (PbI2, CuI, AgI, CdI2 or ZnI2) are reported. Their glass-forming ability, thermal stability, and IR transmitting property are investigated. The results show that the broad absorption peak in the 15-20 μm disappear in the Fourier-transform infrared (spectrometer) spectra when gallium is replaced by indium. Te-based chalcogenide glasses containing metal-halides show superior glass-forming ability and better thermal stability than those containing alkali halides. Among these glasses, the ΔT of glass composition 65GeTe4-17In2Te6-18AgI can be as great as 115 °C. In ternary system, the glass composition Ge16Te69(AgI)15 (ΔT = 120 °C) is stable enough toward crystallization in combination with broad transmission region and good chemical durability to be drawn into optical fibers. [ABSTRACT FROM AUTHOR]

The spectroscopic properties and thermal stability of Er[sub 2]O[sub 3] doped Bi[sub 2]O[sub 3]-B[sub 2]O[sub 3]-Na[sub 2]O glasses are investigated experimentally. A close correlation is observed between the B[sub 2]O[sub 3] content and the spectroscopic properties such as Judd-Ofelt intensity parameters Ω[sub t] (t = 2,4,6), emission spectra, and lifetime of [sup 4]I[sub 13/2] level of Er[sup 3+]. The value of Ω[sub 6] increases with an increase of B[sub 2]O[sub 3] content, which is attributed to the decrease of the covalency of Er-O bond in terms of the glass microstructure and electronegativity theory. The emission spectra of [sup 4]I[sub 13/2] → [sup 4]I[sub 15/2] transition broadens as a consequence of the enhancement of the inhomogeneous distribution of Er[sup 3+] sites when increasing B[sub 2]O[sub 3] content. The lifetime of [sup 4]I[sup 13/]2 level of Er[sup 3+] in bismuth-based glass, compared with those in other glasses, is relative low due to the high-phonon energy of the B-O bond, the large refractive index of the host, and the existence of OH[sup -] in the glass. In addition, the glass stability is improved in which the substitution of B[sub 2]O[sub 3] for Bi[sub 2]O[sub 3] strengthens the network structure. The suitability of bismuth-based glass as a host for Er[sup 3+] doped for a broadband amplifier and its advantages over other glass hosts are also discussed. [ABSTRACT FROM AUTHOR]

Cr2+‐doped II‐VI crystals have witnessed an excellent gain media for continuously tunable and femtosecond‐pulsed lasers. Despite this, major challenges persist toward realizing ultrabroad emission bandwidth and efficient Cr2+‐doped fiber due to the valence diversity of Cr, especially in chalcogenide glasses. Here, we propose to prepare Cr2+:ZnSe/As2S3‐xSex composite glasses by Hot Uniaxial Pressing (HUP), a method that sinters uniformly mixed crystal and glass powders into geometrically designed composite chalcogenide glasses. The densification of the composite glasses reached 99.88%, indicating that a few or none pores remain. Our research shows that Cr2+:ZnSe crystals have good performance in chalcogenide glasses, and the composite glasses have the potential to be made into mid‐infrared–doped fibers. It was demonstrated by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) that the composite glasses have a uniform Cr2+:ZnSe distribution and no crystal disintegration. The transmittance of the composite glasses was significantly improved by tailoring the refraction index. The mid‐infrared (MIR) fluorescence and decay of the glasses were measured. The lattice constant was measured, calculated, and discussed to reveal the influence of sintering process on lifetime. [ABSTRACT FROM AUTHOR]

A fast-response mid-infrared gas sensor based on a chalcogenide suspended-core fiber with microchannels fabricated by a tightly focused femtosecond laser pulse was demonstrated. Chalcogenide four-hole suspended-core fiber was fabricated by extrusion and exhibited the lowest transmission loss of 1 dB/m at 4.7 μm. The 50-μm-diameter solid core in the suspended-core fiber was protected by an outside solid jacket to avoid other environmental factors, such as dust and liquid pollution and touch damage. To increase gas filling rate, we introduced microchannels on the side of the suspended-core fiber by femtosecond laser writing to allow gases to enter into the fiber and fully interact with the core. The distribution, shape, and size of the channels could be controlled by laser writing technology. The engineered technique showed the advantage of increased minor loss in the suspended-core fiber. Methane gas sensing utilizing evanescent wave in the core was carried out in the prepared suspended-core fiber with several hundred microchannels. The methane sensitivity was 100 ppm, and the response time was estimated to be less than 20 s. [ABSTRACT FROM AUTHOR]

High nonlinear fibers with low zero‐dispersion wavelength (ZDW), high laser power tolerance and large band‐gap are urgent for all‐optical‐band supercontinuum (SC) generations. Widely used chalcogenide fibers usually have a large ZDW and low laser power tolerance, and thus are not ideal for such purpose. Here, an ultra‐low material ZDW chalcohalide (ChH) glass fiber with high nonlinearity as well as high laser power tolerance has been fabricated successfully via a novel peeling‐off‐extrusion method. The step‐index fiber has double‐cladding structure, the inner cladding is GeGaSe‐CsI glass and the outer one is GeSbS jacket. The core glass has an ultra‐low material ZDW of 3.5 μm and large absorption edge of 2.0 eV. The nonlinear refractive index is 6.67 × 10−18 m2/W @1.55 μm. Broadband SC generation covering 1.05‐13.0 μm is demonstrated in this novel ChH fiber. Such glass fiber with high nonlinearity, wide transparent range, low ZDW and high laser damage threshold is promising for the applications in the mid‐infrared. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally that in microsphere laser resonators, significant leakage of pump light can be caused by refractions on the microsphere/air boundary. We employ a ray-tracing model to analyze such a light leakage and experiment on applying an external light-blocking barrier to reduce it. In this letter, Nd3+-doped tellurite glass microspheres are fabricated and a flat-ended copper tip is employed as the light-blocking barrier. We show that such a light-blocking barrier causes two instable phenomena to our microsphere lasers, including enhancements of microsphere laser powers and generations of additional lasing peaks. We attribute such phenomena to improved utilization efficiencies of the pump light resulted from the application of the light-blocking barrier. [ABSTRACT FROM AUTHOR]

In this work, two kinds of GeS2–Ga2S3–CsI chalcogenide glasses had been fabricated in conventional meltquenching method, and these glasses express excellent transmittance (0.52–10.5 µm), low refractive index difference, high Raman gain and good thermal stability against crystallization. We designed a highly nonlinear step-index fibre consisting of a 72GeS2–18Ga2S3–10CsI core and a 73GeS2–15Ga2S3–12CsI cladding with the zero dispersion wavelength in near-infrared (<1 µm), and theoretically analysed the optical and nonlinear characteristics of this fibre in detail. Substantial simulation results revealed that wide ultra-flat supercontinuum broadening from the visible to the mid-infrared range can be achieved by pumping this fibre at 1064 nm. [ABSTRACT FROM AUTHOR]

The microhardness of chalcogenide glasses (ChGs) of the Sn–Sb–Se (SSS) ternary system was investigated, and the correlation of microhardness with the mean coordination number of the SSS ChGs was determined. To prepare infrared‐transparent SSS glass‐ceramics (GCs), two SSS ChGs (A, Sn6.23Sb14.11Se79.66; B, Sn9.8Sb17.22Se72.98; by molar composition) were selected and thermally treated at 433 and 448 K, respectively. The improved microhardness (with values that increased by 11.5% and 7.3% for SSS ChG A and B, respectively) of the resulting SSS GCs is attributed to the formation of Sb2Se3 nanocrystals. [ABSTRACT FROM AUTHOR]

The glass‐ceramics of AgI‐based electroconductive chalcogenide system was realized using an appropriate heat treatment at a fairly high temperature (Tg + 40°C) and different times ranging from 4 to 20 hours. The crystallization behavior and electroconductive properties of the heat‐treated samples were studied in detail. Transmission study was performed, and the results show that the cut‐off edge of the short wavelength is red‐shifted at prolonged annealing time but remains an excellent transmittance in the mid‐infrared (IR) region. XRD and scanning electron microscopy results indicated that the precipitated crystalline phases are mainly β‐/γ‐AgI. Moreover, a small amount of α‐AgI, which rarely existed at room temperature, is precipitated in the AgI‐rich chalcogenide glass‐ceramics. The ionic conductivity of all glass‐ceramics was enhanced by heat treatment in contrast to that of base glass. Raman analysis exhibited the structure variation in the glass sample after heat treatments. This study provided an observation of crystallization in chalcogenide glass containing large amounts of AgI and be of good guidance to fabricate novel AgI‐based chalcogenide glass‐ceramics that can be candidates in infrared optics and solid electrolyte applications. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses have the advantages of a wide transparency window (over 20 μm) and high optical nonlinearity (up to a thousand times greater than that of silica glasses), making them good candidates for mid-infrared supercontinuum generation. In this review, we describe both the history and recent developments in mid-infrared supercontinuum generation from chalcogenide fibers according to three kinds of fiber structures: step-index, microstructured and tapered fibers. We also review the coherence properties of mid-infrared supercontinuum generation and all-fiber supercontinuum sources based on chalcogenide fibers. [ABSTRACT FROM AUTHOR]

In this work, a theoretical study was conducted on temperature sensing in Ge-Sb-Se multimode fibre Bragg grating (MM-FBG). The sensing characteristics of the designed MM-FBGs with different fibre parameters and operating wavelengths were calculated using a coupled model method. The temperature sensitivity of this MM-FBG was found to improve significantly by shifting the operating wavelength from telecom range to mid-infrared (MIR) and utilizing the wide transmission range of Ge-Sb-Se glasses. The temperature sensitivity of the proposed Ge-Sb-Se MM-FBG was calculated to be 0.0758 nm/°C at 1550 nm, which is 7.58 times higher than silica FBGs at 1550 nm, and the temperature sensitivity was calculated to be more than 0.16 nm/°C at 3390 nm, which is 2.2 times higher than that at 1550 nm. In addition, the proposed MM-FBGs provided multi-peak information, and the sensitivity of each peak was calculated to be comparable to the single-mode FBG. The proposed Ge-Sb-Se MM-FBG has great potential for temperature sensing in MIR because of its advantages of simple preparation, high coupling efficiency, multi-peak information and wide working window. [ABSTRACT FROM AUTHOR]

A novel family of Ga2S3-Sb2S3-XI (XI = PbI2, CsI, AgI) was investigated to understand the role of metal halides and exploit new chalco-halide glasses for infrared optics. The dependence of the thermal properties, infrared optical properties, and structural information of the novel family on different metal-iodines was investigated. Results showed that metal halides increase the glass stability but decrease the glass network connectivity. The compositional dependence of the short-wave cut-off edge is associated with the electronegativity difference between the cations and anions of the metal halides. Raman study showed that the metal- iodine modified the glass structure mainly through the iodide content, and the cations dissolved in the glass network mostly as charge compensators for the aperiodic network. For the glasses in the series Ga2S3-Sb2S3-XI-Dy3+, Dy3+ emission increased in the PbI2- and CsI-doped glasses but decreased in the AgI-doped glass due to the combined effect of dysprosium and oxygen. For all that, these novel glasses are highly promised for use in infrared optics. [ABSTRACT FROM AUTHOR]

Obtaining information about crystallization kinetics is crucial to understand the transformation speed of phase-change materials and select materials for phase-change memory. In the current work, we first investigated the temperature dependence of the resistance of undoped and In-doped Sb4Te films and found that the crystallization temperature (Tp) and 10-year data retention of Sb4Te increased significantly when it was doped with In. We further employed ultrafast differential scanning calorimetry to explore the crystallization kinetics of In-doped Sb4Te with various compositions, and found In20(Sb4Te)80 to have has the fastest crystallization rate (∼7.1 m s−1 at 726.2 K). The In20(Sb4Te)80 film exhibited a high Tp (∼503 K), better data retention ability (∼418.7 K for 10 years), and ultrafast crystallization with strong non-Arrhenius behavior. These results indicated In20(Sb4Te)80 to be a promising candidate for use in applications of phase change materials. [ABSTRACT FROM AUTHOR]

A series of GeSbSe ( x = 5, 10, 15, 20, 25, and 30 mol%) chalcogenide glasses were prepared by traditional melt-quenching method. The refractive indexes, infrared transmissions, and spontaneous Raman spectra of the glass samples were measured. Based on the spontaneous Raman scattering theory and considering the measured Raman spectral data, we calculated the Raman gain coefficients of the chalcogenide glasses. The effect of Sb on the structures and Raman gain coefficients of the glass samples was then systematically investigated to understand the role of chemical composition in glass structure and Raman gain coefficient. In the GeSbSe glasses, the number of heteropolar Ge-Se, Sb-Se bonds increased, whereas that of homopolar Se-Se bonds decreased at increased Sb concentration. The Raman gain coefficients increased until it reached a maximum value (290 × 10 m/W at GeSbSe) and then decreased when the Sb concentration further increased. These results showed that the Raman gain coefficients of Ge-Sb-Se chalcogenide glasses without poisonous elements were over 300 times of that of commonly fused silica and closely correlated with the structures of the glasses, suggesting that the Raman gain coefficient can be adjusted by modifying the structures of the glasses. This work provides a new possibility for environment-friendly Raman fiber laser and amplifier materials. [ABSTRACT FROM AUTHOR]