Topological edge and corner states of valley photonic crystals with zipper-like boundary conditions

We present a stable valley photonic crystal(VPC)unit cell with C_(3v)symmetric quasi-ring-shaped dielectric columns and realize its topological phase transition by breaking mirror symmetry.Based on this unit cell structure,topological edge states(TESs)and topological corner states(TCSs)are realized.We obtain a new type of wave transmission mode based on photonic crystal zipper-like boundaries and apply it to a beam splitter assembled from rectangular photonic crystals(PCs).The constructed beam splitter structure is compact and possesses frequency separation functions.In addition,we construct a box-shaped triangular PC structures with zipper-like boundaries and discover phenomena of TCSs in the corners,comparing its corner states with those formed by other boundaries.Based on this,we explore the regularities of the electric field patterns of TESs and TCSs,explain the connection between the characteristic frequencies and locality of TCSs,which helps better control photons and ensures low power consumption of the system.

Electronic structure and optical properties of Mg_xZn_(1-x)S bulk crystal using first-principles calculations

We perform the first-principles calculations within the framework of density functional theory to determine the elec- tronic structure and optical properties of MgxZnl-xS bulk crystal. The results indicate that the electronic structure and optical properties of MgxZnl_xS bulk crystal are sensitive to the Mg impurity composition. In particular, the MgxZnl-xS bulk crystal displays a direct band structure and the band gap increases from 2.05 eV to 2.91 eV with Mg dopant compo- sition value x increasing from 0 to 0.024. The S 3p electrons dominate the top of valence band, while the Zn 4s electrons and Zn 3p electrons occupy the bottom of conduction band in MgxZnl_xS bulk crystal. Moreover, the dielectric constant decreases and the optical absorption peak obviously has a blue shift. The calculated results provide important theoretical guidance for the applications of MgxZn1-xS bulk crystal in optical detectors.

Robust optical mode converter based on topological waveguide arrays

Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.

Efficient stochastic parallel gradient descent training for on-chip optical processor

In recent years,space-division multiplexing(SDM)technology,which involves transmitting data information on multiple parallel channels for efficient capacity scaling,has been widely used in fiber and free-space optical communication sys-tems.To enable flexible data management and cope with the mixing between different channels,the integrated reconfig-urable optical processor is used for optical switching and mitigating the channel crosstalk.However,efficient online train-ing becomes intricate and challenging,particularly when dealing with a significant number of channels.Here we use the stochastic parallel gradient descent(SPGD)algorithm to configure the integrated optical processor,which has less com-putation than the traditional gradient descent(GD)algorithm.We design and fabricate a 6×6 on-chip optical processor on silicon platform to implement optical switching and descrambling assisted by the online training with the SPDG algorithm.Moreover,we apply the on-chip processor configured by the SPGD algorithm to optical communications for optical switching and efficiently mitigating the channel crosstalk in SDM systems.In comparison with the traditional GD al-gorithm,it is found that the SPGD algorithm features better performance especially when the scale of matrix is large,which means it has the potential to optimize large-scale optical matrix computation acceleration chips.

Terahertz quasi-perfect vortex beam with integer-order and fractional-order generated by spiral spherical harmonic axicon

We propose a new method to generate terahertz perfect vortex beam with integer-order and fractional-order. A new optical diffractive element composed of the phase combination of a spherical harmonic axicon and a spiral phase plate is designed and called spiral spherical harmonic axicon. A terahertz Gaussian beam passes through the spiral spherical harmonic axicon to generate a terahertz vortex beam. When only the topological charge number carried by spiral spherical harmonic axicon increases, the ring radius of terahertz vortex beam increases slightly, so the beam is shaped into a terahertz quasi-perfect vortex beam. Importantly, the terahertz quasi-perfect vortex beam can carry not only integer-order topological charge number but also fractional-order topological charge number. This is the first time that vortex beam and quasi-perfect vortex beam with fractional-order have been successfully realized in terahertz domain and experiment.

Dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates

Interactive holography offers unmatched levels of immersion and user engagement in the field of future display.Despite of the substantial progress has been made in dynamic meta-holography,the realization of real-time,highly smooth interactive holography remains a significant challenge due to the computational and display frame rate limitations.In this study,we introduced a dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates.To our knowledge,this is the first reported practical dynamic interactive metasurface holographic system.We spa-tially divided the metasurface device into multiple distinct channels,each projecting a reconstructed sub-pattern.The switching states of these channels were mapped to bitwise operations on a set of bit values,which avoids complex holo-gram computations,enabling an ultra-high computational frame rate.Our approach achieves a computational frame rate of 800 kHz and a display frame rate of 23 kHz on a low-power Raspberry Pi computational platform.According to this methodology,we demonstrated an interactive dynamic holographic Tetris game system that allows interactive gameplay,color display,and on-the-fly hologram creation.Our technology presents an inspiration for advanced dynamic meta-holography,which is promising for a broad range of applications including advanced human-computer interaction,real-time 3D visualization,and next-generation virtual and augmented reality systems.

Research on Optimal Preload Method of Controllable Rolling Bearing Based on Multisensor Fusion

Angular contact ball bearings have been widely used in machine tool spindles,and the bearing preload plays an important role in the performance of the spindle.In order to solve the problems of the traditional optimal preload prediction method limited by actual conditions and uncertainties,a roller bearing preload test method based on the improved D-S evidence theorymulti-sensor fusion method was proposed.First,a novel controllable preload system is proposed and evaluated.Subsequently,multiple sensors are employed to collect data on the bearing parameters during preload application.Finally,a multisensor fusion algorithm is used to make predictions,and a neural network is used to optimize the fitting of the preload data.The limitations of conventional preload testing methods are identified,and the integration of complementary information frommultiple sensors is used to achieve accurate predictions,offering valuable insights into the optimal preload force.Experimental results demonstrate that the multi-sensor fusion approach outperforms traditional methods in accurately measuring the optimal preload for rolling bearings.

Acoustic Bilayer Gradient Metasurfaces for Perfect and Asymmetric Beam Splitting

We experimentally and theoretically present a paradigm for the accurate bilayer design of gradient metasurfaces for wave beam manipulation,producing an extremely asymmetric splitting effect by simply tailoring the interlayer size.This concept arises from anomalous diffraction in phase gradient metasurfaces and the precise combination of the phase gradient in bilayer metasurfaces.Ensured by different diffraction routes in momentum space for incident beams from opposite directions,extremely asymmetric acoustic beam splitting can be generated in a robust way,as demonstrated in experiments through a designed bilayer system.Our work provides a novel approach and feasible platform for designing tunable devices to control wave propagation.

Effects of power on ion behaviors in radio-frequency magnetron sputtering of indium tin oxide(ITO)

This study delves into ion behavior at the substrate position within RF magnetron discharges utilizing an indium tin oxide(ITO)target.The positive ion energies exhibit an upward trajectory with increasing RF power,attributed to heightened plasma potential and initial emergent energy.Simultaneously,the positive ion flux escalates owing to amplified sputtering rates and electron density.Conversely,negative ions exhibit broad ion energy distribution functions(IEDFs)characterized by multiple peaks.These patterns are clarified by a combination of radiofrequency oscillation of cathode voltage and plasma potential,alongside ion transport time.This elucidation finds validation in a one-dimensional model encompassing the initial ion energy.At higher RF power,negative ions surpassing 100 e V escalate in both flux and energy,posing a potential risk of sputtering damages to ITO layers.

Low-Dimensional Halide Perovskites and Their Advanced Optoelectronic Applications

Metal halide perovskites are crystalline materials originally developed out of scientific curiosity. They have shown great potential as active materials in optoelectronic applications. In the last 6 years, their certified photovoltaic efficiencies have reached 22.1%. Compared to bulk halide perovskites, low-dimensional ones exhibited novel physical properties. The photoluminescence quantum yields of perovskite quantum dots are close to 100%. The external quantum efficiencies and current efficiencies of perovskite quantum dot light-emitting diodes have reached 8% and 43 cd A^(-1),respectively, and their nanowire lasers show ultralow-threshold room-temperature lasing with emission tunability and ease of synthesis. Perovskite nanowire photodetectors reached a responsivity of 10 A W^(-1)and a specific normalized detectivity of the order of 10^(12 )Jones. Different from most reported reviews focusing on photovoltaic applications, we summarize the rapid progress in the study of low-dimensional perovskite materials, as well as their promising applications in optoelectronic devices. In particular, we review the wide tunability of fabrication methods and the state-of-the-art research outputs of low-dimensional perovskite optoelectronic devices. Finally, the anticipated challenges and potential for this exciting research are proposed.

A review:Photonics devices,architectures,and algorithms for optical neural computing

The explosive growth of data and information has motivated various emerging non-von Neumann computational approaches in the More-than-Moore era.Photonics neuromorphic computing has attracted lots of attention due to the fascinating advantages such as high speed,wide bandwidth,and massive parallelism.Here,we offer a review on the optical neural computing in our research groups at the device and system levels.The photonics neuron and photonics synapse plasticity are presented.In addition,we introduce several optical neural computing architectures and algorithms including photonic spiking neural network,photonic convolutional neural network,photonic matrix computation,photonic reservoir computing,and photonic reinforcement learning.Finally,we summarize the major challenges faced by photonic neuromorphic computing,and propose promising solutions and perspectives.

Recent Advances of Graphitic Carbon Nitride-Based Structures and Applications in Catalyst, Sensing, Imaging, and LEDs

The graphitic carbon nitride(g-C_3N_4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C_3N_4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are ‘‘earth-abundant.'' This review summarizes the latest progress related to the design and construction of g-C_3N_4-based materials and their applications including catalysis, sensing,imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C_3N_4-based research for emerging properties and applications is also included.

Enhanced ion conductivity and electrode–electrolyte interphase stability of porous Si anodes enabled by silicon nitride nanocoating for high-performance Li-ion batteries

Silicon (Si) is a promising anode material for next-generation high-energy lithium-ion batteries (LIBs) due to its high capacity.However,the large volumetric expansion,poor ion conductivity and unstable solid electrolyte interface (SEI) lead to rapid capacity fading and low rate performance.Herein,we report Si nitride (SiN) comprising stoichiometric Si_(3)N_(4) and Li-active anazotic SiN_(x) coated porous Si (p-Si@SiN)for high-performance anodes in LIBs.The ant-nest-like porous Si consisting of 3D interconnected Si nanoligaments and bicontinuous nanopores prevents pulverization and accommodates volume expansion during cycling.The Si_(3)N_(4) offers mechanically protective coating to endow highly structural integrity and inhibit superfluous formation of SEI.The fast ion conducting Li_(3)N generated in situ from lithiation of active SiN_(x) facilitates Li ion transport.Consequently,the p-Si@SiN anode has appealing electrochemical properties such as a high capacity of 2180 mAh g^(-1)at 0.5 A g^(-1) with 84%capacity retention after 200cycles and excellent rate capacity with discharge capacity of 721 mAh g^(-1) after 500 cycles at 5.0 A g^(-1).This work provides insights into the rational design of active/inactive nanocoating on Si-based anode materials for fast-charging and highly stable LIBs.

Recent progress of the optoelectronic properties of 2D Ruddlesden-Popper perovskites

Two-dimensional(2 D) hybrid organic-inorganic perovskites have recently attracted attention due to their layered nature, naturally formed quantum well structure, large exciton binding energy and especially better long-term environmental stability compared with their three-dimensional(3 D) counterparts. In this report, we present a brief overview of the recent progress of the optoelectronic applications in 2 D perovskites. The layer number dependent physical properties of 2 D perovskites will first be introduced and then the different synthetic approaches to achieve 2 D perovskites with different morphologies will be discussed. The optical, optoelectronic properties and self-trapped states in 2 D perovskites will be described, which are indispensable for designing the new device structures with novel functionalities and improving the device performance. Subsequently, a brief summary of the advantages and the current research status of the 2 D perovskite-based heterostructures will be illustrated.Finally, a perspective of 2 D perovskite materials is given toward their material synthesis and novel device applications.

Toward high-performance two-dimensional black phosphorus electronic and optoelectronic devices

Recently, black phosphorus （BP） has joined the two-dimensional material family as a promising candidate for elec- tronic and photonic applications due to its moderate bandgap, high carrier mobility, and unusual in-plane anisotropy. Here, we review recent progress in BP-based devices, such as field-effect transistors, contact resistance, quantum transport, stabil- ity, photodetector, heterostructure, and in-plane anisotropy. We also give our perspectives on future BP research directions.

MOF-Like 3D Graphene-Based Catalytic Membrane Fabricated by One-Step Laser Scribing for Robust Water Purification and Green Energy Production

Increasing both clean water and green energy demands for survival and development are the grand challenges of our age.Here,we successfully fabricate a novel multifunctional 3D graphene-based catalytic membrane(3D-GCM)with active metal nanoparticles(AMNs)loading for simultaneously obtaining the water purification and clean energy generation,via a“green”one-step laser scribing technology.The as-prepared 3D-GCM shows high porosity and uniform distribution with AMNs,which exhibits high permeated fluxes(over 100 L m^(−2) h^(−1))and versatile super-adsorption capacities for the removal of tricky organic pollutants from wastewater under ultra-low pressure-driving(0.1 bar).After adsorption saturating,the AMNs in 3D-GCM actuates the advanced oxidization process to self-clean the fouled membrane via the catalysis,and restores the adsorption capacity well for the next time membrane separation.Most importantly,the 3D-GCM with the welding of laser scribing overcomes the lateral shear force damaging during the long-term separation.Moreover,the 3D-GCM could emit plentiful of hot electrons from AMNs under light irradiation,realizing the membrane catalytic hydrolysis reactions for hydrogen energy generation.This“green”precision manufacturing with laser scribing technology provides a feasible technology to fabricate high-efficient and robust 3D-GCM microreactor in the tricky wastewater purification and sustainable clean energy production as well.

Hydroiodic Acid Additive Enhanced the Performance and Stability of PbS-QDs Solar Cells via Suppressing Hydroxyl Ligand

The recent emerging progress of quantum dot ink(QD-ink)has overcome the complexity of multiple-step colloidal QD(CQD)film preparation and pronouncedly promoted the device performance.However,the detrimental hydroxyl(OH)ligands induced from synthesis procedure have not been completely removed.Here,a halide ligand additive strategy was devised to optimize QD-ink process.It simultaneously reduced sub-bandgap states and converted them into iodide-passivated surface,which increase carrier mobility of the QDs films and achieve thicker absorber with improved performances.The corresponding power conversion efficiency of this optimized device reached 10.78%.(The control device was 9.56%.)Therefore,this stratege can support as a candidate strategy to solve the QD original limitation caused by hydroxyl ligands,which is also compatible with other CQD-based optoelectronic devices.

Time-Resolved Optical Emission Spectroscopy Diagnosis of CO_2 Laser-Produced SnO_2 Plasma

The spectral emission and plasma parameters of SnO2 plasmas have been investigated. A planar ceramic SnO2 target was irradiated by a CO2 laser with a full width at half maximmn of 80 ns. The temporal behavior of the specific emission lines from the SnO2 plasma was characterized. The intensities of Sn I and Sn Ⅱ lines first increased, and then decreased with the delay time. The results also showed a faster decay of Sn I atoms than that of Sn II ionic species. The temporal evolutions of the SnO2 plasma parameters （electron temperature and density） were deduced. The measured temperature and density of SnO2 plasma are 4.38 eV to 0.5 eV and 11.38×1017 cm 3 to 1.1×1017^ cm-3, for delay times between 0.1 μs and 2.2 #s. We also investigated the effect of the laser pulse energy on Sn02 plasma.

Effect of optical pumping on the momentum relaxation time of graphene in the terahertz range

The momentum relaxation time of a photoexcited graphene in the THz frequency range has been studied by using terabertz time domain spectroscopy under optical pumping at room temperature. It is found that the momentum relaxation time of the graphene as a function of the optical pumping intensity exhibits a threshold behavior. The features of the momentum relaxation time as a function of the optical pumping intensity are also investigated. The results are useful for understanding the basic underlying physics of graphene scattering as well as finding the possible applications in carbon- based electronics.

Spectral and ion emission features of laser-produced Sn and SnO2 plasmas

We have made a detailed comparison of the atomic and ionic debris, as well as the emission features of Sn and SnO2 plasmas under identical experimental conditions. Planar slabs of pure metal Sn and ceramic SnO2 are irradiated with 1.06 μm, 8 ns Nd：YAG laser pulses. Fast photography employing an intensified charge coupled device （ICCD）, optical emission spectroscopy （OES）, and optical time of flight emission spectroscopy are used as diagnostic tools. Our results show that the Sn plasma provides a higher extreme ultraviolet （EUV） conversion efficiency （CE） than the SnO2 plasma. However, the kinetic energies of Sn ions are relatively low compared with those of SnO2. OES studies show that the Sn plasma parameters （electron temperature and density） are lower compared to those of the SnO2 plasma. Furthermore, we also give the effects of the vacuum degree and the laser pulse energy on the plasma parameters.