Electric field manipulation of multiple nonequivalent Dirac cones in the electronic structures of hexagonal CrB_4 sheet

Two-dimensional materials with Dirac cones have significant applications in photoelectric technology. The origin and manipulation of multiple Dirac cones need to be better understood. By first-principle calculations, we study the influence of external fields on the electronic structure of the hexagonal CrB4 sheet with double nonequivalent Dirac cones. Our results show that the two cones are not sensitive to tensile strain and out-of-plane electric field, but present obviously different behaviors under the in-plane external electric field（along the B-B direction）, i.e., one cone holds while the other vanishes with a gap opening. More interestingly, a new nonequivalent cone emerges under a proper in-plane electric field. We also discuss the origin of the cones in CrB4 sheet. Our study provides a new method on how to obtain Dirac cones by the external field manipulation, which may motivate potential applications in nanoelectronics.

Multidimensional manipulation of wave fields based on artificial microstructures

Artificial microstructures,which allow us to control and change the properties of wave fields through changing the geometrical parameters and the arrangements of microstructures,have attracted plenty of attentions in the past few decades.Some artificial microstructure based research areas,such as metamaterials,metasurfaces and phononic topological insulators,have seen numerous novel applications and phenomena.The manipulation of different dimensions(phase,amplitude,frequency or polarization)of wave fields,particularly,can be easily achieved at subwavelength scales by metasurfaces.In this review,we focus on the recent developments of wave field manipulations based on artificial microstructures and classify some important applications from the viewpoint of different dimensional manipulations of wave fields.The development tendency of wave field manipulation from single-dimension to multidimensions provides a useful guide for researchers to realize miniaturized and integrated optical and acoustic devices.

A look at field manipulation and antenna design using 3D transformation electromagnetics and 2D surface electromagnetics

While many techniques have been developed for the design of different types of antennas,such as wire antenna,patch antenna,lenses,and reflectors,these cannot be said general-purpose strategies for the synthesis and design of antennas to achieve the performance characteristics specified by users.Recently,there has been an increasing need for the development of antenna design techniques because of the advent of 5 G and a variety of space,defense,biological,and similar applications,for which a robust and general-purpose design tool is not to be developed.The main objective of this study is to take a look at antenna design from the field manipulation point of view,which has the potential to partially fulfill this need.We review the existing field manipulation techniques,including field transformation methods based on Maxwell’s and wave equations,point out some limitations of these techniques,and then present ways to improve the performance of these methods.Next,we introduce an alternative approach for field manipulation based on two-dimensional(2 D)metasurfaces,and present laws of the generalized reflection and refraction that are based on 2 D surface electromagnetics.Then,we explore how to overcome the limitations of conventional reflection and refraction processes that are strictly bounded by the critical angle.Finally,we provide some application examples of field manipulation methods in the antenna design,with a view on developing a general-purpose strategy for antenna design for future communication.

Revolutionizing plasmonic platform via magnetic field-assisted confined ultrafast laser deposition of high-density,uniform,and ultrafine nanoparticle arrays

The remarkable capabilities of 2D plasmonic surfaces in controlling optical waves havegarnered significant attention.However,the challenge of large-scale manufacturing of uniform,well-aligned,and tunable plasmonic surfaces has hindered their industrialization.To address this,we present a groundbreaking tunable plasmonic platform design achieved throughmagnetic field(MF)assisted ultrafast laser direct deposition in air.Through precise control of metal nanoparticles(NPs),with cobalt(Co)serving as the model material,employing an MF,and fine-tuning ultrafast laser parameters,we have effectively converted coarse and non-uniform NPs into densely packed,uniform,and ultrafine NPs(~3 nm).This revolutionary advancement results in the creation of customizable plasmonic‘hot spots,’which play a pivotal role insurface-enhanced Raman spectroscopy(SERS)sensors.The profound impact of this designable plasmonic platform lies in its close association with plasmonic resonance and energyenhancement.When the plasmonic nanostructures resonate with incident light,they generate intense local electromagnetic fields,thus vastly increasing the Raman scattering signal.This enhancement leads to an outstanding 2–18 fold boost in SERS performance and unparalleled sensing sensitivity down to 10^(-10)M.Notably,the plasmonic platform also demonstratesrobustness,retaining its sensing capability even after undergoing 50 cycles of rinsing andre-loading of chemicals.Moreover,this work adheres to green manufacturing standards,making it an efficient and environmentally friendly method for customizing plasmonic‘hot spots’inSERS devices.Our study not only achieves the formation of high-density,uniform,and ultrafine NP arrays on a tunable plasmonic platform but also showcases the profound relation betweenplasmonic resonance and energy enhancement.The outstanding results observed in SERS sensors further emphasize the immense potential of this technology for energy-relatedapplications,including photocatalysis,photovoltaics,and clean water,propelling us closer to a sustainable and cleaner future.

Microwave coherent manipulation of cold atoms in optically induced fictitious magnetic traps on an atom chip

We propose a novel on-chip platform for controlling and manipulating cold atoms precisely and coherently. The scheme is achieved by producing optically induced fictitious magnetic traps（OFMTs） with 790 nm（for -（87）Rb） circularly polarized laser beams and state-dependent potentials simultaneously for two internal atomic states with microwave coplanar waveguides. We carry out numerical calculations and simulations for controlled collisional interactions between OFMTs and addressable single atoms＇ manipulation on our designed hybrid atom chips. The results show that our proposed platform is feasible and flexible, which has wide applications including collisional dynamics investigation, entanglement generation,and scalable quantum gates implementation.

Graphene-empowered dynamic metasurfaces and metadevices

Metasurfaces,with extremely exotic capabilities to manipulate electromagnetic(EM)waves,have derived a plethora of advanced metadevices with intriguing functionalities.Tremendous endeavors have been mainly devoted to the static metasurfaces and metadevices,where the functionalities cannot be actively tuned in situ post-fabrication.Due to the in-trinsic advantage of active tunability by external stimulus,graphene has been successively demonstrated as a favorable candidate to empower metasurfaces with remarkably dynamic tunability,and their recent advances are propelling the EM wave manipulations to a new height:from static to dynamic.Here,we review the recent progress on dynamic metasur-faces and metadevices enabled by graphene with the focus on electrically-controlled dynamic manipulation of the EM waves covering the mid-infrared,terahertz,and microwave regimes.The fundamentals of graphene,including basic ma-terial properties and plasmons,are first discussed.Then,graphene-empowered dynamic metasurfaces and met-adevices are divided into two categories,i.e.,metasurfaces with building blocks of structured graphene and hybrid metasurfaces integrated with graphene,and their recent advances in dynamic spectrum manipulation,wavefront shap-ing,polarization control,and frequency conversion in near/far fields and global/local ways are elaborated.In the end,we summarize the progress,outline the remaining challenges,and prospect the potential future developments.

Integrated structured light manipulation

Structured light,also known as tailored light,shaped light,sculpted light,or custom light,refers to a series of special light beams with spatially variant amplitudes and phases,polarization distributions,or more general spatiotemporal profiles.In the past decades,structured light featuring distinct properties and unique spatial or spatiotemporal structures has grown into a significant research field and given rise to many developments from fundamentals to applications.Very recently,integrated structured light manipulation has become an important trend in the frontier of light field manipulation and attracted increasing interest as a highly promising technique for shaping structured light in an integrated,compact,and miniaturized manner.In this article,we give a comprehensive overview of recent advances in integrated structured light manipulation(generation,processing,detection,and application).After briefly introducing the basic concept and development history of structured light,we present representative works in four important aspects of integrated structured light manipulation,including multiple types of integrated structured light generation,many sorts of integrated structured light processing,diverse forms of integrated structured light detection,and various kinds of integrated structured light applications.We focus on summarizing the progress of integrated structured light manipulation from basic theories to cutting-edge technologies,to key devices,and to a wide variety of applications,from orbital angular momentum carrying light beams to more general structured light beams,from passive to active integration platforms,from micro-nano structures and metasurfaces to 2D photonic integrated circuits and 3D photonic chips,from in-plane to out-of-plane,from multiplexing to transformation,from linear to nonlinear,from classical to quantum,from optical communications to optical holography,imaging,microscopy,trapping,tweezers,metrology,etc.Finally,we also discuss in detail the future trends,opportunities,challenges,and solutions,and give a vision for integrated structured light manipulation.

Dynamically taming focal fields of femtosecond lasers for fabricating microstructures

Micromachining based on femtosecond lasers usually requires accurate control of the sample movement,which may be very complex and costly.Therefore,the exploration of micromachining without sample movement is valuable.Herein,we have illustrated the manipulation of optical fields by controlling the polarization or phase to vary periodically and then realized certain focal traces by real-time loading of the computer-generated holograms(CGHs) on the spatial light modulator.The focal trace is composed of many discrete focal spots,which are generated experimentally by using the real-time dynamically controlled CGHs.With the designed focal traces,various microstructures such as an ellipse,a Chinese character "Nan",and an irregular quadrilateral grid structure are fabricated in the z-cut LiNbO_(3) wafers,showing good qualities in terms of continuity and homogeneity.Our method proposes a movement free solution for micromachining samples and completely abandons the high precision stage and complex movement control,making microstructure fabrication more flexible,stable,and cheaper.

Optical bound states in the continuum in periodic structures:mechanisms,effects,and applications

Optical bound states in the continuum(BICs)have recently stimulated a research boom,accompanied by demonstrations of abundant exotic phenomena and applications.With ultrahigh quality(Q)factors,optical BICs have powerful abilities to trap light in optical structures from the continuum of propagation waves in free space.Besides the high Q factors enabled by the confined properties,many hidden topological characteristics were discovered in optical BICs.Especially in periodic structures with well-defined wave vectors,optical BICs were discovered to carry topological charges in momentum space,underlying many unique physical properties.Both high Q factors and topological vortex configurations in momentum space enabled by BICs bring new degrees of freedom to modulate light.BICs have enabled many novel discoveries in light-matter interactions and spin-orbit interactions of light,and BIC applications in lasing and sensing have also been well explored with many advantages.In this paper,we review recent developments of optical BICs in periodic structures,including the physical mechanisms of BICs,explored effects enabled by BICs,and applications of BICs.In the outlook part,we provide a perspective on future developments for BICs.

Generation and reconfiguration of interference-pattern helico-conical beams

We proposed an approach for the generation of interference-pattern helico-conical beams(HCBs)both theoretically and experimentally.The HCBs exhibiting intricate fringe structures are obtained by exploiting amplitude modulation and interference techniques.To precisely control the optical field distributions,we manipulate the azimuthal term within the helicoconical phase expression,presenting several illustrative cases that highlight the versatility of our approach.Through further combinations,more sophisticated comprehensive HCB patterns are investigated.This study deepens our knowledge about spiral-like optical patterns and paves a new avenue for potential applications,especially in the fields of particle manipulation,nanostructure fabrication,and optical metrology.

Magnetic properties and anomalous Hall effect of Mn3Sn thin films controlled by defects and ferroelectric 0.7Pb(Mg_(1/3)Nb_(2/3))O_(3)–0.3PbTiO_(3) substrate

Noncollinear antiferromagnetic Mn_(3)Sn films have received much attention due to their potential applications in antiferromagnetic spintronic devices. In this work, single-phase polycrystalline antiferromagnetic Mn_(3)Sn thin films were successfully prepared by magnetron sputtering. The defects in the thin films were regulated by adjusting the sputtering power. The relationship among the films structure, the anomalous Hall effect(AHE) and the defects was investigated. High defect concentration in the Mn_(3)Sn films led to large room temperature ferromagnetic moments. The maximum saturation magnetization reached up to ~16 k A·m^(-1)(36 mlB/Mn), which was much larger than the values reported in literatures. The coercive field of38 mT was obtained in a high-quality Mn_(3)Sn film, which effectively reduced the flipping magnetic field. Moreover,the anomalous Hall resistance and coercive field of the Mn_(3)Sn films prepared on the ferroelectric substrates were manipulated through an applied electric field, indicating that the piezoelectric stress has a great influence on the nonzero Berry curvature of the triangular spin structure in the antiferromagnetic materials. These results will promote the potential application of Mn_(3)Sn in high-density and lowpower antiferromagnetic spintronic devices.

SIMULATION OF TANK SLOSHING BASED ON OPENFOAM AND COUPLING WITH SHIP MOTIONS IN TIME DOMAIN

Tank sloshing in ship cargo is excited by ship motions, which induces impact load on tank wall and then affects the ship motion. Wave forces acting on ship hull and the retardation function are solved by using three-dimensional frequency domain theory and an impulse response function method based on the potential flow theory, and global ship motion is examined coupling with nonlinear tank sloshing which is simulated by viscous flow theory. Based on the open source Computational Fluid Dynamics （CFD） development platform Open Field Operation and Manipulation （OpenFOAM）, numerical calculation of ship motion coupled with tank sloshing is achieved and the corresponding numerical simulation and validation are carried out. With this method, the interactions of wave, ship body and tank sloshing are completely taken into consideration. This method has quite high efficiency for it takes advantage of potential flow theory for outer flow field and viscous flow theory for inside tank sloshing respectively. The numerical and experimental results of the ship motion agree well with each other.