Vacancy defect MoSeTe embedded in N and F co-doped carbon skeleton for high performance sodium ion batteries and hybrid capacitors

Sodium-ion batteries(SIBs) and hybrid capacitors(SIHCs) have garnered significant attention in energy storage due to their inherent advantages,including high energy density,cost-effectiveness,and enhanced safety.However,developing high-performance anode materials to improve sodium storage performa nce still remains a major challenge.Here,a facile one-pot method has been developed to fabricate a hybrid of MoSeTe nanosheets implanted within the N,F co-doped honeycomb carbon skeleton(MoSeTe/N,F@C).Experimental results demonstrate that the incorporation of large-sized Te atoms into MoSeTe nanosheets enlarges the layer spacing and creates abundant anion vacancies,which effectively facilitate the insertion/extraction of Na^(+) and provide numerous ion adsorption sites for rapid surface capacitive behavior.Additionally,the heteroatoms N,F co-doped honeycomb carbon skeleton with a highly conductive network can restrain the volume expansion and boost reaction kinetics within the electrode.As anticipated,the MoSeTe/N,F@C anode exhibits high reversible capacities along with exceptional cycle stability.When coupled with Na_(3)V_(2)(PO_(4))_(3)@C(NVPF@C) to form SIB full cells,the anode delivers a reversible specific capacity of 126 mA h g^(-1) after 100 cycles at 0.1 A g^(-1).Furthermore,when combined with AC to form SIHC full cells,the anode demonstrates excellent cycling stability with a reversible specific capacity of50 mA h g^(-1) keeping over 3700 cycles at 1.0 A g^(-1).In situ XRD,ex situ TEM characterization,and theoretical calculations(DFT) further confirm the reversibility of sodium storage in MoSeTe/N,F@C anode materials during electrochemical reactions,highlighting their potential for widespread practical application.This work provides new insights into the promising utilization of advanced transition metal dichalcogenides as anode materials for Na^(+)-based energy storage devices.

High stability and low noise laser-diode end-pumped Nd:YAG ceramic passively Q-switched laser at 1123 nm based on a Ti_(3)C_(2)T_(x)-PVA saturable absorber

We report a high repetition frequency, high power stability and low laser noise laser-diode(LD) end-pumped Nd: YAG ceramic passively Q-switched laser at 1123 nm based on a Ti_(3)C_(2)T_(x)-polyvinyl alcohol(PVA) film as a saturable absorber(SA). A Brewster polarizer(BP) and a birefringent crystal(BC) are incorporated to enable frequency selection and filtering for the passively Q-switched 1123 nm pulsed laser to improve the power stability and reduce the noise. When the pump power is 5.1 W, an average output power of 457.9 m W is obtained, corresponding to a repetition frequency of 1.09 MHz,a pulse width of 56 ns, a spectral line width of 0.65 nm, a power instability of ±0.92%, and a laser noise of 0.89%.The successful implementation of the “Ti_(3)C_(2)T_(x)-PVA film passively Q-switching” combined with “frequency selection and filtering of BP + BC” technology path provides a valuable reference for developing pulsed laser with high repetition frequency, high stability and low noise.

Temperature-dependent photoluminescence of lead-free cesium tin halide perovskite microplates

Tin halide perovskites recently have attracted extensive research attention due to their similar electronic and band structures but non-toxicity compared with their lead analogues. In this work, we prepare high-quality CsSnX_(3)(X=Br,I) microplates with lateral sizes of around 1–4 μm by chemical vapor deposition and investigate their low-temperature photoluminescence(PL) properties. A remarkable splitting of PL peaks of the CsSnBr_(3)microplate is observed at low temperatures. Besides the possible structural phase transition at below 70 K, the multi-peak fittings using Gauss functions and the power-dependent saturation phenomenon suggest that the PL could also be influenced by the conversion from the emission of bound excitons into free excitons. With the increase of temperature, the peak position shows a blueshift tendency for CsSnI_(3), which is governed by thermal expansion. However, the peak position of the CsSnBr3microplate exhibits a transition from redshift to blueshift at ~160 K. The full width at half maximum of CsSnX_(3)broadens with increasing temperature, and the fitting results imply that longitudinal optical phonons dominate the electron–phonon coupling and the coupling strength is much more robust in CsSnBr3than in CsSnI_(3). The PL intensity of CsSnX_(3)microplates is suppressed due to the enhanced non-radiative relaxation and exciton dissociation competing with radiative recombination. According to the Arrhenius law, the exciton binding energy of CsSnBr_(3)is ~38.4 meV, slightly smaller than that of CsSnI_(3).

Interfacial photoconductivity effect of type-Ⅰ and type-Ⅱ Sb2Se3/Si heterojunctions for THz wave modulation

An in-depth understanding of the photoconductivity and photocarrier density at the interface is of great significance for improving the performance of optoelectronic devices. However, extraction of the photoconductivity and photocarrier density at the heterojunction interface remains elusive. Herein, we have obtained the photoconductivity and photocarrier density of 173 nm Sb2Se3/Si(type-Ⅰ heterojunction) and 90 nm Sb2Se3/Si(type-Ⅱ heterojunction) utilizing terahertz(THz) time-domain spectroscopy(THz-TDS) and a theoretical Drude model. Since type-Ⅰ heterojunctions accelerate carrier recombination and type-Ⅱ heterojunctions accelerate carrier separation, the photoconductivity and photocarrier density of the type-Ⅱ heterojunction(21.8×10^(4)S·m^(-1),1.5 × 10^(15)cm^(-3)) are higher than those of the type-Ⅰ heterojunction(11.8×10^(4)S·m^(-1),0.8×10^(15)cm^(-3)). These results demonstrate that a type-Ⅱ heterojunction is superior to a type-Ⅰ heterojunction for THz wave modulation. This work highlights THz-TDS as an effective tool for studying photoconductivity and photocarrier density at the heterojunction interface. In turn, the intriguing interfacial photoconductivity effect provides a way to improve the THz wave modulation performance.

Transverse manipulation of particles using Bessel beam of tunable size generated by cross-phase modulation

We report on a method to achieve multiple microscopic particles being trapped and manipulated transversely by using a size-tunable Bessel beam generated by cross-phase modulation(XPM)based on the thermal nonlinear optical effect.The results demonstrate that multiple polystyrene particles can be stably trapped simultaneously,and the number of the trapped particles can be controlled by varying the trapping beam power.In addition,the trapped particles can be manipulated laterally with micron-level precision by changing the size of J_(0)Bessel beam.This work provides a simple but efficient way to trap and manipulate multiple particles simultaneously,which would have potential applications in many fields such as cell sorting and transportation.

Numerical study of converting beat-note signals of dual-frequency lasers to optical frequency combs by optical injection locking of semiconductor lasers

The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations.The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides.

Resolution for Forward and Phase-Conjugate Degenerate Four-Wave Mixing in Hot Atomic Media

Resolutions of degenerate four-wave mixing with forward and phase-conjugate configurations (FDFWM and PCDFWM) are investigated and compared theoretically and experimentally in hot rubidium (Rb) atomic vapor.The theoretical simulations indicate that PCDFWM is of much higher resolution than FDFWM.The resolution of PCDFWM is less dependent on Doppler broadening.The experimental results are in good agreement with the theoretical expectation.PCDFWM can resolve the hyperfine transitions and crossover resonances of 87 Rb which cannot be achieved by FDFWM.Additionally,with sample temperature increasing,the linewidth of FDFWM spectrum obviously broadens.In comparison,no obvious broadening can be observed in the PCDFWM spectrum.

Perovskite Termination-Dependent Charge Transport Behaviors of the CsPbI3/Black Phosphorus van der Waals Heterostructure

Fundamental understanding of interfacial charge behaviors is of great significance for the optoelectronic and photovoltaic applications.However, the crucial roles of perovskite terminations in charge transport processes have not been completely clear.We investigate the charge transfer behaviors of the CsPbI3/black phosphorus(BP)van der Waals heterostructure by using the density functional theory calculations with a self-energy correction.The calculations at the atomic level demonstrate the type-Ⅱ band alignments of the CsPbI3/BP heterostructure,which make electrons transfer from the perovskite side to monolayer BP.Moreover, the stronger interaction and narrower physical separation of the interfaces can lead to higher charge tunneling probabilities in the CsPbI3/BP heterostructure.Due to different electron affinities, the PbI2-terminated perovskite slab tends to collect electrons from the adjacent materials, whereas the CsI-termination prefers to inject electrons into transport materials.In addition, the interface coupling effect enhances the visible-light-region absorption of the CsPbI3/BP heterostructure.This study highlights the importance of the perovskite termination in the charge transport processes and provides theoretical guidelines to develop high-performance photovoltaic and optoelectronic devices.

Fiber coupled high count-rate single-photon generated from InAs quantum dots

In this work,we achieve high count-rate single-photon output in single-mode(SM)optical fiber.Epitaxial and dilute InAs/GaAs quantum dots(QDs)are embedded in a GaAs/AlGaAs distributed Bragg reflector(DBR)with a micro-pillar cavity,so as to improve their light emission extraction in the vertical direction,thereby enhancing the optical SM fiber’s collection capabil-ity(numerical aperture:0.13).By tuning the temperature precisely to make the quantum dot exciton emission resonant to the micro-pillar cavity mode(Q~1800),we achieve a fiber-output single-photon count rate as high as 4.73×10^(6) counts per second,with the second-order auto-correlation g2(0)remaining at 0.08.

High Optical Magnification Three-Dimensional Integral Imaging of Biological Micro-organism

A high optical magnification three-dimensional imaging system is proposed using an optic microscope whose ocular （eyepiece） is retained and the structure of the transmission mode is not destroyed. The elemental image array is captured through the micro lens array. Due to the front diffuse transmission element, each micro lens sees a slightly different spatial perspective of the scene, and a different independent image is formed in each micro lens channel. Each micro lens channel is imaged by a Fourier lens and captured by a CCD. The design translating the stage in x or y provides no parallax. Compared with the conventional integral imaging of micro-objects, the optical magnification of micro-objects in the proposed system can enhanced remarkably. The principle of the enhancement of the image depth is explained in detail and the experimental results are presented.

1.6-μm single-frequency erbium-doped fiber laser based on two cascaded subrings

We demonstrate a stable narrow linewidth single-frequency erbium-doped fiber laser(EDFL)operating at 1.6μm.A Fabry–Perot fiber Bragg grating and two cascaded subrings are incorporated in the main ring cavity to achieve singlefrequency operation.The experimentally measured optical signal-to-noise ratio is greater than 73 dB.Furthermore,the linewidth of the EDFL is measured to be about 480 Hz by the self-built short-delayed self-heterodyne interferometry device.The laser shows superior stability,with no mode-hopping during the 60-min observation period.The proposed EDFL provides a new experimental idea for realizing a single-frequency fiber laser in the L-band.

设计并构建Ⅰ型SnSe_(2)/ZnS异质结构提升其光电化学探测及水分解性能

二维范德瓦尔斯异质结构广泛应用于光电化学(PEC)型光电探测器、水分解和太阳能电池等光电器件中.其中,Ⅰ型异质结构对于设计新型光电器件至关重要,然而其能带排列对光电响应的影响尚不清楚.本文利用两步物理气相沉积法构建了Ⅰ型SnSe_(2)/ZnS异质结构,并通过紫外光电子能谱和X射线光电子能谱进行了验证.基于Ⅰ型SnSe_(2)/ZnS异质结构的光电化学探测器在紫外可见范围内具有良好的光响应、高稳定性和高灵敏度.SnSe_(2)/ZnS的光响应可达172.60μA W^(-1),分别是单一ZnS和SnSe_(2)样品的7.4和2.0倍.并且,SnSe_(2)/ZnS异质结构具有较高的光电催化分解水活性,在2 h内总产氢量可达81.25μmol cm-2.SnSe_(2)/ZnS异质结优异的光电探测和水分解性能主要源于其更高的光利用率和高效电荷传输的协同作用.本工作为通过构建Ⅰ型异质结构来提高光电响应并设计高性能光电探测器和水分解等光电器件提供了一种新方法.

Size-controlled synthesis and red up-converted luminescence of CeO_(2):Yb^(3+)/Er^(3+) nanospheres

In this work,cubic-phased CeO_(2):18 mol%Yb^(3+)/2 moI%Er^(3+)nanospheres were prepared by coprecipitation method,in which the size of nanosphere was precisely controlled by regulating the amount of coprecipitator urea.The morphology evolution of CeO_(2):18%Yb3+/2%Er^(3+)samples that vary from nanosphere to nano-flower with extending the reaction time was elaborately investigated via increasing the amount of urea and increasing the reaction temperature.The influence of non-radiative relaxation(NR)processes and surface quenching on up-conversion emission output of CeO_(2):18%Yb^(3+)/2%Er^(3+)was investigated through varying the sizes and environmental temperatures.Tissue imaging experiment demonstrates that CeO_(2):18%Yb^(3+)/2%Er^(3+)nanospheres have the potential to act as luminescent imaging reagents in tissue imaging.

Dynamics of frequency detuning in a hybrid Er-doped mode-locked fiber laser

Frequency detuning of mode-locked fiber lasers displays many remarkable nonlinear dynamical behaviors.Here we report for the first time the evolution of pulses from mode-locking through period pulsation to Q-switched mode-locking for three fundamental cases.Our experiments are performed in a hybrid actively and passively amplitude-modulated all-fiber polarization-maintaining mode-locked fiber laser,where the amplitude modulation frequency artificially deviates from the fundamental frequency of the cavity.We design and numerically simulate the laser with coupled Ginzburg–Landau equations.The experimentally observed dynamics of the mode detuning process is discussed with the assistance of the fitted model and numerical simulations,showing the generalizability of the optical mode detuning variation process.Our work provides fundamental insights for understanding perturbations in nonlinear optical resonant cavities and expands the ideas for studying chaotic path theory in hybrid mode-locked fiber lasers.

Construction of MoS_(2) nanoarrays and MoO_(3) nanobelts:Two efficient adsorbents for removal of Pb(Ⅱ),Au(Ⅲ) and Methylene Blue

Toxic heavy metal ions,valuable noble metal ions and organic dyes are significant concerns in wastewater treatment.In this work,MoO_(3) nanobelts(MoO_(3) NBs)prepared by solvothermal method and MoS_(2) nanoarrays(MoS_(2) NAs)constructed using MoO_(3) NBs precursor were proposed to effectively remove heavy/noble metal ions and organic dyes,such as Pb(II),Au(III)and Methylene Blue(MB).The two adsorbents exhibited the excellent adsorption capacity towards Pb(II),Au(III)and MB.The maximum removal capacity of Pb(II)and MB on MoO_(3) NBs was 684.93 mg/g and 1408 mg/g,respectively,whereas that of Au(III)and MB on MoS_(2) NAs was 1280.2 mg/g and 768 mg/g,respectively.Furthermore,the thermodynamic parameters were calculated from the temperature-dependent curves,suggesting that the removal of Pb(II)and Au(III)on both adsorbents was spontaneous and endothermic.The new adsorbents introduced here were high adsorption activity,ease of fabrication,high scalability,good chemical stability,great repeatability and abundant and cheap supply,which were highly attractive for wastewater treatment.

Saturable and reverse saturable absorption in molybdenum disulfide dispersion and film by defect engineering

Understanding and controlling defect in two-dimensional materials is important for both linear and nonlinear optoelectronic devices,especially in terms of tuning nonlinear optical absorption.Taking advantage of an atomic defect formed easily by smaller size,molybdenum disulfide nanosheet is prepared successfully with a different size by gradient centrifugation.Interestingly,size-dependent sulfur vacancies are observed by high-resolution X-ray photoelectron spectroscopy,atomic force microscopy,and transmission electron microscopy.The defect effect on nonlinear absorption is investigated by Z-scan measurement at the wavelength of 800 nm.The results suggest the transition from saturable absorption to reverse saturable absorption can be observed in both dispersions and films.First principle calculations suggest that sulfur vacancies act as the trap state to capture the excited electrons.Moreover,an energy-level model with the trap state is put forward to explain the role of the sulfur vacancy defect in nonlinear optical absorption.The results suggest that saturable absorption and reverse saturable absorption originate from the competition between the excited,defect state and ground state absorption.Our finding provides a way to tune the nonlinear optical performance of optoelectronic devices by defect engineering.

Switchable single-and dual-wavelength femtosecond mode-locked Er-doped fiber laser based on carboxyl-functionalized graphene oxide saturable absorber

In this Letter, we demonstrated the switchable single-and dual-wavelength femtosecond soliton generation in single-mode Er-doped fiber lasers with the usage of carboxyl-functionalized graphene oxide(GO-COOH) saturable absorbers(SAs) for the first time, to the best of our knowledge. The fiber laser generated a stable single-wavelength conventional soliton at 1560.1 nm with a pulse duration of 548.1 fs. The dual-wavelength solitons centered at 1531.9 nm and 1555.2 nm with a spacing of approximately 23 nm can be obtained by adjusting the pump power of the cavity. Our experimental results indicated the GO-COOH has great potential to be used in ultrafast fiber lasers as broadband SAs.

构建Ⅰ型SnS_(2)/Bi_(2)Se_(3)和Ⅱ型SnS_(2)/Bi_(2)Te_(3)范德瓦尔斯异质结构提升其光电性能

基于新型先进材料的异质结构为提高光电器件的光电性能奠定了基石.能带排列是理解异质结构中载流子输运机理和界面动力学的关键.本文利用物理气相沉积法和化学气相沉积法制备了SnS_(2)/Bi_(2)X_(3)(X=Se,Te)范德华异质结构.通过高分辨率X射线光电子能谱测量的能带排列证实了Ⅰ型SnS_(2)/Bi_(2)Te_(3)和Ⅱ型SnS_(2)/Bi_(2)Te_(3)异质结构的成功制备.基于SnS_(2)/Bi_(2)X_(3)异质结构的光电化学型光电探测器的光电响应得到了极大的提高.Ⅰ型SnS_(2)/Bi_(2)Te_(3)和Ⅱ型SnS_(2)/Bi_(2)Te_(3)异质结构的光电流密度均比SnS_(2)、Bi_(2)Te_(3)和Bi_(2)Te_(3)的光电流密度高一个数量级以上.SnS_(2)/Bi_(2)X_(3)异质结构光电性能的显著提高主要是由于:(i)异质结构中光激发电子和空穴的有效分离;(ii)SnS_(2)/Bi_(2)X_(3)异质结构与电解质界面具有更高的电荷转移效率和载流子密度;(iii)异质结构的构建拓宽了光的吸收范围.此外,直立的SnS_(2)还可以有效地捕获光子以提高其光电性能.Ⅰ型SnS_(2)/Bi_(2)Te_(3)异质结构的光电性能优于Ⅱ型SnS_(2)/Bi_(2)Te_(3)异质结构,这主要源于异质结构/电解质界面上更高效的电荷传输能力.实验研究结果表明,Ⅰ型和Ⅱ型异质结构的构建为开发高性能光电探测器及其他光电器件提供了新思路.

Wavelength-flexible all-polarization-maintaining self-sweeping fiber laser based on intracavity loss tuning

We reported a wavelength-flexible all-polarization-maintaining self-sweeping fiber laser based on the intracavity loss tuning brought by the bent optical fiber. The bidirectional cavity structure achieved the self-sweeping effect due to the appearance of the dynamic grating in the active fiber with the spatial hole burning effect. Under this, a section of fiber was bent into a circle for adjusting the loss of the cavity. With a descending diameter of bent fiber circle, the sweeping range moves to the shorter wavelength and covers a wide range from 1055.6 to 1034.6 nm eventually. Both the initial wavelength of self-sweeping regime and the threshold of the fiber laser show exponential correlation with the diameter of the circular fiber. Our work provides a compact and low-cost way to achieve the broad wavelength-flexible self-sweeping operation.

Third-order nonlinear optical properties of WTe2 films synthesized by pulsed laser deposition

The prominent third-order nonlinear optical properties of WTe2 films are studied through the Z-scan technique using a femtosecond pulsed laser at 1030 nm.Open-aperture(OA)and closed-aperture(CA)Z-scan measurements are performed at different intensities to investigate the nonlinear absorption and refraction properties of WTe2 films.OA Z-scan results show that WTe2 films always hold a saturable absorption characteristic without transition to reverse saturable absorption.Further,a large nonlinear absorption coefficientβis determined to be-3.37×10^3 cm∕GW by fitting the OA Z-scan curve at the peak intensity of 15.603 GW∕cm^2.In addition,through the slow saturation absorption model,the ground state absorption cross section,excited state absorption cross section,and absorber's density were found to be 1.4938×10^-16 cm^2,1.2536×10^-16 cm^2,and 6.2396×10^20 cm^-3,respectively.CA Z-scan results exhibit a classic peak–valley shape of the CA Z-scan signal,which reveals a self-defocusing optical effect of WTe2 films under the measured environment.Furthermore,a considerable nonlinear refractive index value n2 can be obtained at-1.629×10^-2 cm^2∕GW.Ultimately,the values of the real and imaginary parts of the third-order nonlinear susceptibility of WTe2 are roughly estimated to be-5.93×10^-9 and-1.01×10^-8 esu with the help of first-principles calculations.WTe2 possesses sizeable thirdorder nonlinear coefficients compared with other materials,which suggests that it has great potential to improve performance in nonlinear optical devices.