bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of mesoscale eddies on the vertical spatial characteristics of wind-generated noise in deep ocean
Authors: Jiang Guang-Yu , Sun Chao , Li Qin-Ran ,   School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China,   Key Laboratory of Ocean Acoustic and Sensing, Ministry of Industry and Information Technology, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Mesoscale eddy is a marine phenomenon occurring frequently in deep ocean, and it will disturb the sound speed in the upper water layer. As a result, the mesoscale eddies will influence the propagation of wing-generated noise and cause the noise field to vary. In this paper, we investigate the effects of mesoscale eddies on the vertical spatial characteristics (including the noise vertical directionality and the noise vertical correlation) of wind-generated noise at different depths of its horizontal center of the eddy. In the study, the Gaussian eddy model is used to describe the sound speed fluctuation, and the ray and parabolic equation theories are used to describe the noise propagating in the near field and far field, respectively. Simulations indicate as follows. 1) At the depth of the eddy center, a clod-core eddy causes both the width of the horizontal notch and the noise vertical correlation to decrease, while the effect of a warm-core eddy is contrary to that of the cold-core eddy. 2) At the depth far from the eddy center, the effect of eddies is reduced, a cold-core and a warm-core eddy only lead the peak at the down edge of the horizontal notch in the noise directionality to rise and fall, respectively, and do not influence the noise vertical correlation. 3) The effect of an eddy becomes severe as its absolute strength becomes higher. The ray reversion method based on the principle of reciprocity is used to explain the physical reason behind the above phenomena. By the method the rays are launched from the noise receiving point and the polar angle and the strength of the noise arriving reversely along the ray paths are analyzed. It is shown that the change of the polar angle and the strength of the noise arriving reversely along the surface reflected ray paths in the presence of eddies are the main cause for changing the noise vertical spatial characteristics. Furthermore, simulations show that the analyses and conclusions in the study are still approximately valid when the receiving point deviates from the eddy center but the horizontal distance between them is short.
Band gap engineering and applications in compound periodic structure containing hyperbolic metamaterials
Authors: Wu Feng , Guo Zhi-Wei , Wu Jia-Ju , Jiang Hai-Tao , Du Gui-Qiang ,   Ministry of Education Key Laboratory of Advanced Microstructure Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China,   School of Optoelectronic Engineering, Guangdong Polytechnic Normal University, Guangzhou 510665, China,   School of Space Science and Physics, Shandong Univeristy, Weihai 264209, China
Published: December 2020

Behaviours of light in materials strongly depend on the topological structure of the iso-frequency surface (IFS). The usual materials, of which the unit cell of photonic crystal is made up, are dielectrics, whose IFSs have the same closed topological structure. As a simplest photonic crystal, one-dimensional photonic crystal (1DPC) has attracted intensive attention due to its simple fabrication technique as well as numerous applications. However, in a conventional all-dielectric 1DPC, photonic band gaps (PBGs) for both transverse magnetic (TM) and transverse electric (TE) polarizations will shift toward short wavelengths (i.e. blueshift) as incident angle increases. The underlying physical reason is that the propagating phase in isotropic dielectric will decrease as incident angle increases. The blueshift property of band gap for TM and TE polarization will limit the band width of omnidirectional band gap and the range of operating incident angles in some PBG-based applications, including near-perfect absorption, polarization selection and sensitive refractive index sensing. However, for TM polarization, the propagating phase in a hyperbolic metamaterial (HMM) will increase with incident angle increasing. This special phase property of HMM provides us with a way to flexibly tune the angle-dependent property of band gap in periodic compound structure composed of alternative HMM with open IFS and dielectric with close IFS. In this review, we realize zeroshift (i.e. angle-independent) band gaps as well as redshift band gaps in 1DPCs containing HMMs, which can be utilized to realize near-perfect absorption, sensitive refractive index sensing and polarization selection working in a wide range of incident angles.
Analysis of ArF excimer laser system discharge characteristics in different buffer gases
Authors: Wang Qian , Zhao Jiang-Shan , Fan Yuan-Yuan , Guo Xin , Zhou Yi ,   Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100094, China,   Beijing Excimer Laser Technology and Engineering Center, Beijing 100094, China,   University of Chinese Academy of Sciences, Beijing 100049, China,   State Key Laboratory of Applied Optics, Changchun 130033, China
Published: December 2020

Excimer laser is the current mainstream source of international semiconductor lithography. The stable operation of the laser system directly affects the working efficiency of the semiconductor lithography machine, so it is very important to optimize the laser system. The buffer gas commonly used in ArF excimer laser systems is He, Ne. In the early years, Shinjin Nagai and Mieko Ohwa have studied the output characteristics of the system when using He or Ne as a buffer gas from the aspect of pump efficiency and gain coefficient, and pointed out that using Ne instead of He has no obvious advantages in terms of efficiency. However, when Ne is used as the buffer gas, the reaction between Ne and electrons is more complicated. In addition to direct ionization and excitation reactions, it also contains a large amount of step ionization and secondary ionization, which releases free electrons. The stability of the system is improved, when Ne is used as the buffer gas. The ArF excimer laser system discharge characteristics in different buffer gases are analyzed based on fluid model in the paper. The role of photoionization is discussed. The simulation results show that the width of the electron depletion layer and the cathode sheath are both smaller, and the discharge stability is higher when Ne is used as the buffer gas. The expansion of the discharge region is accelerated and the threshold voltage of the discharge is reduced by adding Xe into Ne to trigger photoionization. The excimer laser discharge process is very complicated and is affected by many factors. Only two factors of the buffer gas and the photoionization process are studied in this paper. The simulation model will be extended from one-dimensional case to two-dimensional case in the future, and multiple physical factors of the ArF excimer laser system will be considered.
Two-dimensional simulation of dynamic characteristics of N2–O2 corona discharge at micro scale
Authors: Chai Yu , Zhang Ni , Liu Jie , Yin Ning , Liu Shu-Lin , Zhang Jing-Yuan ,   College of Electrical and Control Engineering, Xi'an University of Science and Technology, Xi'an 710054, China,   Postdoctoral Station of Mechanical Engineering, Xi’an University of Science and Technology, Xi’an 710054, China,   Jiangsu Province Laboratory of Mining Electric and Automation, China University of Mining and Technology, Xuzhou 221008, China
Published: December 2020

Based on the principle of micro-scale discharge, the micro-nano ionization gas sensor has the characteristics of fast response, high precision and easy integration. It is expected to achieve rapid and accurate detection of gas. At present, there is a lack of systematic analysis of the inter-polar discharge process of the new sensor. This paper uses the fluid-chemical dynamics methodology to create a 2D space discharge model of the N2-O2 mixed gas at the micron gap and the nano-tip field in ambient atmosphere at normal temperature and pressure. Meanwhile, by analyzing the mutual coupling between the space electron transport process, the discharge current density, and the space electric field strength, the paper clarifies the dynamics of space discharge in the field, improves how internal discharges work in such micro-nano structured ionization gas sensors, and analyzes the pattern of influence of different polar distances on space discharges. The results show that the electric field in the space remains constant as the production and consumption of positive and negative ions reaches a dynamic equilibrium in the field. It is reflected in the field strengthening effect of positive ion groups to the cathode plate and of negative ion groups to the anode plate, as well as in the field weakening effect between positive and negative ion groups. The resulting stable and strong electric field of the cathode makes sure that space discharge is maintained, and the discharge current density stabilizes. Initially, as the polar distance decreases gradually, the electric field strength between the poles and plates increases. It plays a leading role in the accumulation of electron energy and in the increase in the number density of electrons, thus leading to the increase of the output current density up to the peak value when the polar distance D = 50 μm. As the polar distance decreases, the field strength between the poles and plates increases. Despite that, when electrons accumulate energy up to such a level that gas molecules can be ionized, the necessary movement distance and the distance required to increase the number density of electrons decreases. As a result, the degree of ionization weakens, and the field strengthening effect of positive ions decreases. In other words, the increment of the field strength caused by positive ions at the tip decreases, and in turn, the discharge current density decreases. This pattern serves as a theoretical support in the optimization of the micro-nano structured ionization gas sensors.
Characterization of phase separation on AlGaN surfaces by in-situ photoluminescence spectroscopy and high spatially resolved surface potential images
Authors: Liu Bo-Yang , Song Wen-Tao , Liu Zheng-Hui , Sun Xiao-Juan , Wang Kai-Ming , Wang Ya-Kun , Zhang Chun-Yu , Chen Ke-Bei , Xu Geng-Zhao , Xu Ke , Li Da-Bing ,   School of Nano-Tech and Nano-Bionics, University of Science and Technology of China, Hefei 230026, China,   Suzhou Institue of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China,   Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

AlGaN is a key material for deep ultraviolet optoelectronic and electronic devices. With the increase of the Al composition ratio, the phase separation on the surface, caused by small-scale compositional fluctuations, is prone to affecting the performance of the device. In order to explore the mechanism of the phase separation on a nanoscale, the AlGaN wafers with different quantities of Al compositions are investigated by the confocal photoluminescence spectroscopy and the single-pass Kelvin force probe microscopy. The composition ratios of Al for the three samples are about 0.3, 0.5, and 0.7, respectively. The single-pass Kelvin force probe microscopy based on dual-frequency phase-locking is used to obtain high spatially resolved (about 10 nm) surface potential images. In the area where the phase separation phenomenon is obvious in the photoluminescence spectrum, the sharp change of the surface potential can be observed at the irregular steps and the edges of the surface pits. The potential changes can be ascribed to the inhomogeneous composition distribution. In the area where the topography turns into step flow, the surface pits shrink and merge. No obvious surface potential domain boundaries appear at the steps nor on the edges of the surface pits. Meanwhile, the phase separation phenomenon in the photoluminescence spectrum almost disappears. Our experiments show that the steps and the edges of the surface pits on AlGaN surfaces are main reasons for small-scale compositional fluctuations and the phase separation in the spectrum. Combining with in-situ confocal photoluminescence spectra, high spatially resolved surface potential image by single-pass Kelvin force probe microscopy is an effective method to characterize the phase separation on AlGaN surface on a nanoscale.
Illumination and temperature analysis for CE-5 candidate landing site Mons Rümker
Authors: Zhong Zhen , Zhang Teng , Zhang Jie , Chen Shi-Guo ,   School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, China,   School of Geography and Resources, Guizhou Education University, Guiyang 550018, China
Published: December 2020

The forthcoming lunar exploration of Chang’e-5 (CE-5) mission will be the first sampling return project of China. The actual drilling needs the information about real-time illumination and corresponding temperature. To give a support for the project, in this paper the SPICE software system is first used to calculate the real-time illumination at the CE-5 candidate landing site Mons Rümker. It is found that our synthetic map of illumination is consistent with the morning map of illumination provided by the Japan’s SELENE satellite. This result verifies the rationality of our algorithm and the corresponding code. According to the calculated illumination and considering a one-dimensional heat conduction model, we study the temperature distribution over Mons Rümker. It is found that the regolith temperature near the surface is greatly related to the illumination, but varies a little with the depth increasing. It is also discovered that the regolith temperature beneath a depth of 0.57 m will not change any more. To give a support for the actual drilling program, it is recommended to consider the temperature difference between the outside and inside of the regolith, especially their stresses caused by such a temperature difference. Moreover, considering the drilling depth of CE-5 larger than 0.57 m, it is likely to measure the heat flow for the constant-temperature layer. We propose that for the next lunar exploration following CE-5 the measurement of heat flow is considered. This will promote the research of lunar science.
Diffusion of Al atoms and growth of Al nanoparticle clusters on surface of Ni substrate
Authors: Zhang Yu-Wen , Deng Yong-He , Wen Da-Dong , Zhao He-Ping , Gao Ming ,   College of Physics, Mechanical and Electrical Engineering, Jishou University, Jishou 416000, China,   School of Computational Science and Electronics, Hunan Institute of Engineering, Xiangtan 411100, China
Published: December 2020

NiAl nanoparticles possess high-energy density and good mechanical properties at elevated temperatures, and are considered as an important material. However, the differences in the diffusion behavior of Al adsorbed atoms on different Ni substrate surfaces and the effects of different diffusion mechanisms on the deposition growth of Al atoms on the Ni substrate surface are highly desired to be clarified. Therefore, in the present work, the diffusion behavior of single Al adsorbed atoms and nanoparticle cluster growth on the Ni substrate surface of decahedral (DEC), cuboctahedral(CUB) and icosahedral(ICO) structures are systematically studied by molecular dynamics (MD) throuh analyzing the embedded atom potentialand using the nudged elastic band method. The diffusion barriers of Al adsorbed atoms on three different Ni substrates are calculated by nudged elastic band methodand analyzed, showing that the diffusion barrier is greatly affected by the smoothness of the step edge and the atomic coordination number of substrate as well. The diffusions of Al adsorption atoms on the surfaces of three Ni substrates are realized by two mechanisms, namely exchanging or hoping, and the lowest Ehrlich-Schwoebel (ES) barrier is 0.38 eV for exchange CUB{111} → {100}, 0.52 eV for exchange DEC{111} → {100}, and 0.52 eV for hoping ICO {111} → {111}. The exchanging mechanismsupports Al adatoms diffusing from {111} to {100} facet on the three Ni substrates, while the diffusion between two adjacent {111} facets is mainly driven by the hoping mechanism. On this basis, atom-by-atom growth MD simulation is used to study the structure of the Ni-Al cluster. The deposited Al atoms first tend to diffuse near the edges of the steps and the vertices. The deposited Al atoms begin to aggregate into islands with the increase of their number. For Al atoms on the Ni cluster, a good Ni-core/Al-shell structure can be obtained by depositing Al atoms on the surface of Ni substrate at lower temperatures. In this core-shell structure, Al atoms have a larger surface energy and atom radius compared with Ni atoms. For the ICO substrate, the corresponding defect number of core-shell clusters is smaller than for the CUB and the DEC substrate, which is in good agreement with the diffusion behavior of Al adsorbed atoms on the Ni substrate cluster surface. The surface of Ni-Al bimetal is gradually alloyed with the increase of growth temperature. This study provides a good insight into the diffusion and growth of Al adsorbed atoms on Ni substrates surface on an atomic scale.
Controllable nano-friction of graphene surface by fabricating nanoscale patterning based on atomic force microscopy
Authors: Zhang Yu-Xiang , Peng Yi-Tian , Lang Hao-Jie ,   College of Mechanical Engineering, Donghua University, Shanghai 201620, China
Published: December 2020

Friction-controlled graphene has great potential as a solid lubricant in micro/nano electromechanical systems. In this work, the conductive atomic force microscope was used to conduct oxidation etching on the graphene surface to produce different nanoscale patterns. The frictional properties of graphene nanoscale patterns were compared under different etching parameters, and the degree of oxidation of the etching patterns was analyzed by Scanning Kelvin Probe Microscopy. The results indicated that the degree of graphene oxidation can be controlled by changing the tip voltage, load and thickness so that graphene forms stable, adjustable oxidation point, line and nanometer patterns on the Au/SiO2/Si substrate. The diameter of oxidation point and width of oxidation line increased with the increase of voltage. The continuity and uniformity of nanometer patterns was improved by Increasing the thickness of graphene. The friction increased with the increase of tip voltage, which was attributed to the increase of meniscus force and electrostatic force. These nanostructures can precisely regulate nano-friction of graphene surface. The realization of the processing of nanoscale patterns and the adjustment of nano-friction characteristics provides a new idea and method for the study of electrical friction behavior of graphene in micro/nano electromechanical systems and the preparation of nano-devices with patterned surfaces.
Optical field enhancements and applications by epsilon-near-zero medium with dielectric dopant
Authors: Zhao Lin , Feng Yi-Jun ,   School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China,   School of Electronic Engineering, Naval University of Engineering, Wuhan 430033, China
Published: December 2020

Field enhancement is an interesting and important topic in electromagnetic study. Electromagnetic field concentration and enhancement devices have wide applications in high directional antenna design, laser ignition, optical control, etc. At present, there are usually two ways of implementing the field enhancement, one is to use the artificial electromagnetic materials to realize the radiation direction control and energy concentration, which is more suitable for the applications at microwave or lower frequencies, and the other is to use the materials with high permittivity or high permeability. However, the latter is extremely sensitive to the position and characteristic of the radiation source and the cross-sectional area of the material, and depends heavily on the value of the relative permittivity or the relative permeability of the material. Therefore, both methods cannot fully meet the application requirements of creating high field intensity in optical band, such as laser ignition, etc. In this paper, based on the theory of photonic crystal doping, the strong electromagnetic field enhancement has been successfully realized by epsilon-near-zero medium filled with ordinary dielectric dopant. We first make the comprehensive theoretical analysis of the field enhancement in the structure of epsilon-near-zero medium with dielectric dopant. The method of calculating the central magnetic field in the doped medium is then rigorously derived, and the formula for the ratio of the central magnetic field in the doped medium to the external radiation field is deduced. We find that the optimal magnetic field enhancement occurs only when the proposed structure is equivalent to an epsilon-mu-near-zero medium. Subsequently, under the above condition, various parameters (radius of the cylindrical dopant, number of sources, etc.) are studied to analyze the magnetic field enhancement performance inside the doped medium. The theoretical analysis and simulation results show that the proposed structure can significantly enhance the magnetic field which is applicable in a broad frequency band from microwave to optical region, and meets the application requirements of providing high field intensity. Finally, as a practical realization example, an ultraviolet ignition device working at 270 nm is designed, which presents an efficient and alternative way of developing electromagnetic (optical) devices for producing strong field enhancement.
Characteristics of multi-crystals monfiguration X-ray diffraction and application in characterizing synchrotron beamline bandwidth
Authors: Yang Jun-Liang , Li Zhong-Liang , Li Tang , Zhu Ye , Song Li , Xue Lian , Zhang Xiao-Wei ,   Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China,   Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 200120, China,   University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this paper, the X-ray diffraction experiment with multiple crystals configuration and its application in characterizing the emission characteristics of double crystal monochromator (DCM) on BL09 beamline of Shanghai Synchrotron Radiation Facility (SSRF) are reported. It is a non-dispersion configuration when the second crystal of DCM and the crystal analyzer form a (+n, –n) type experimental configuration. The rocking curve of the analyzer crystal can only reflect the operation of the DCM. It is the dispersion configurations when the second crystal of DCM and the crystal analyzer form the (+n, +n), (+n, –m) and (+n, +m) type experimental configuration. The width of the analyzer crystal rocking curve includes not only the intrinsic bandwidth of the DCM and the analyzer crystal, but also the angular divergence of the beamline. In this paper, we use the method of DuMond diagram to explicitly illustrate the characteristics of the output beam of the DCM which can be measured under the above two kinds of experimental configurations, and distinguish the diffraction characteristics of different experimental configurations at the same time. Finally, the angular bandwidth and the relative energy bandwidth of the DCM are 5.40(4) arcsec and1.30(1) × 10–4 @ 10 keV, respectively, which are obtained by deconvolution of the analyzer crystal in (+1, –1) nondispersive configuration. The angular distribution and the relative energy bandwidth of the synchrotron radiation beams are 26(1) arcsec and 6.3(2) × 10–4 @ 10 keV, respectively, which are obtained by deconvolution of the analyzer crystal and removal of dispersion broadening in (+1, +1), (+1, –3) and (+1, +3) dispersion configuration. After removing the influence of the DCM, the obtained angular divergence of the light source by 25(1) arcsec @ 10 keV, is consistent with the theoretical value of the bending source. In addition, under a series of different white beam entrance slit widths, we characterize the divergence and bandwidth of the beam emitted from the monochromator by the method of multi-crystals dispersion configuration and the DuMond diagram.
Study on a novel probe for stimulated emission depletion Super-resolution Imaging of Mitochondria
Authors: Zhang Jia , Samanta Soham , Wang Jia-Lin , Wang Lu-Wei , Yang Zhi-Gang , Yan Wei , Qu Jun-Le ,   Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
Published: December 2020

Optical microscopy has the advantages of real-time, non-invasive, tomography, three-dimensional imaging and living imaging. However, its spatial resolution cannot exceed half wavelength due to the existence of optical diffraction limit, which limits the development of optical microscopy. The primary task of super-resolution imaging is to break the diffraction limit and improve the resolution of optical microscopy for study of subcellular structure. Many kinds of super-resolution imaging technologies have been reported, among which the stimulated emission depletion (STED) microscopy is the earliest imaging technology to break the optical diffraction limit at present. STED microscopy can achieve nanometer-scale spatial resolution by breaking the optical diffraction limit with pure optical methods and a clever optical design. However, the application of STED microscopy in biomedicine, especially in live cell imaging is limited by high illumination power of STED light. In this paper, a new type of STED probe has been developed. The spectral analysis results show that the peak of the excitation and emission spectrum of this probe is as far as 122 nm away from each other, which is very suitable for the study of STED super-resolution because of its long stokes redshift. After colocalization with commercial mitochondrial dyes, it was found that the probe had a higher localization coefficient with commercial dyes and could be well positioned on mitochondrial organelles. At the same time, it was found that strong mitochondrial signal could be detected with low-power excitation light (only 1 μW in the experiment), and can get higher resolution of 62 nm under the STED light with 39.5 mW. The result of measuring the transverse resolution obtained by STED light under different power shows that the saturated light power of the probe is 3.5 mW (1.1 MW·cm–2). Through the anti-bleaching testing, the probe still has a strong fluorescence intensity after more than 300 times of high power light irradiation, which indicates that the probe has a strong anti-bleaching property. Through a series of tests, this paper present a novel STED probe which has good mitochondrial targeting, excellent photobleaching-resistance, high resolution and low saturation power, which provides a new research tool for long-term live cell mitochondrial super-resolution imaging.
Research progress of monolayer two-dimensional atomic crystal materials grown by molecular beam epitaxy in ultra-high vacuum conditions
Authors: Wang Xing-Yue , Zhang Hui , Ruan Zi-Lin , Hao Zhen-Liang , Yang Xiao-Tian , Cai Jin-Ming , Lu Jian-Chen ,   Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China
Published: December 2020

Two-dimensional atomic crystal materials have similar lattice structures and physical properties to graphene, providing a broad platform for the scientific research of nanoscaled devices. The emergence of two-dimensional materials presents the new hope of science and industry. As is well known, graphene is the most widely studied two-dimensional (2D) material in recent ten years. Its unique atomic structure and electronic band structure make it have novel physical and chemical properties and broad applications in electronic devices, optical devices, biosensors, solar cell, and lithium ion battery. In recent years, graphene-like single-layered 2D materials have attracted much attention. Researches of these 2D atomic crystal materials and their physical properties, on the one hand, are expected to make up for the lack of band gap in graphene, and on the other hand, continue to explore their unique properties, expand the application of 2D atomic crystal materials. Among all the preparation methods of single-layered 2D atomic crystal materials, the molecular beam epitaxy (MBE) is considered to be the most competitive method. The manufacturing process of MBE is usually carried out under ultra-high vacuum condition, which ensures the cleanness of the 2D material surface. At the same time, the solid growth substrate needed for epitaxial growth can be used as a carrier to support and stabilize the growth of 2D materials. In this review, we summarize many single-layered 2D materials prepared by MBE under ultra-high vacuum conditions in recent years, including monatomic 2D atomic crystal materials (silicene, germanene, stanene, hafnene, borophene, phosphorene, bismuthene, antimonene) and binary atomic crystal materials (hexagonal boron nitride, transition metal dichalcogenides, copper selenide, silver telluride). In addition, by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED) and first-principles calculations, we investigate the atomic structures, energy gap modulations, and electrical properties of 2D materials. These 2D atomic crystal materials exhibit the excellent physical properties, which will make them have broad application prospects in future electronic devices. Finally, we summarize the problems faced by the further development of 2D materials and suggest several potential development directions.
Controllable quantum interference and photon transport in three-mode closed-loop cavity-atom system
Authors: Dai Yu-Fei , Chen Yao-Tong , Wang Lan , Yin Kai , Zhang Yan ,   Center for Quantum Sciences, School of Physics, Northeast Normal University, Changchun 130024, China,   Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083, China
Published: December 2020

In recent years, it has been a hot research topic to study the interaction between atomic ensemble and cavities, and many researches have been done in this regard. In such a system, some atoms are trapped in the cavity, which can be used to study their dynamic characteristics, e.g., the evolution of photon numbers and photon transition. The Jaynes-Cummings model is an important model for studying the dynamic characteristics of the cavity-atom system, which is based on the interaction between a single two-level atom and the cavity field. Recently, coherent photon control in cavity under specific conditions has become an important part of quantum computing and communication. It is worth noting that the tunable photon transmission and all-optical switches based on the cavity have already aroused much interest and have been used in many areas. The quantum information and networks are mostly rooted in complex optical devices, which may show nonreciprocal or asymmetric photon transport. In this paper, we demonstrate that by using an optical closed-loop system the unconventional photon transport can be realized with two mutually perpendicular cavities coupled through external fiber and a two-level atom placed on the intersection. This three-mode system supports two orthogonal propagation directions, that is to say, and the interactions among probe fields are mutually perpendicular. Without ignoring the spontaneous decay of the natural atom, the complex and controllable quantum interference induced by the efficient hybrid interaction of the light, cavity modes, and the atom in such a closed-loop structure can result in a few interesting symmetric and asymmetric photon transport behaviors, i.e. coherent perfect synthesis and coherent perfect reflection. Aside from these compelling properties, the group velocity can also be modulated, i.e., fast and slow light effect. All of these processes can be dynamically controlled by using the probe field phase difference, the tunneling coupling between two cavities and the coupling between the cavity and the atom. Importantly, due to so many advantages, such a tunable scheme can be readily extended to some optical devices, e.g., the switch and the router that is challenging to conventional optical devices.
Plasmonic band structures and its applications
Authors: Liu Liang , Han De-Zhuan , Shi Lei ,   College of Math and Physics, Mianyang Teachers’ College, Mianyang 621000, China,   College of Physics, Chongqing University, Chongqing 401331, China,   Key Laboratory of Micro & Nano Photonic Structures (MOE), Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China
Published: December 2020

Due to its special optical properties the surface plasmon polariton (SPP) has been applied to many fields such as chemistry, biology, communication, nano energy. The more in-depth researches on plasmonic band structures can conduce to understanding more the properties of plasmonic micro- and nano-structures. In this review, we first introduce some metal structures which have plasmonic band structures. Then, we review some unique properties of plasmonic band structures including bound state in the continuum, waveguide, complete band gap, topology, etc. Based on the above properties, the plasmonic applications are introduced. Finally, we briefly introduce the band structures of graphene-based plasmonics and its applications.
Influence of bias magnetic field direction on band structure of magnetic photonic crystal and its role in constructing topological edge states
Authors: Xi Xiang , Ye Kang-Ping , Wu Rui-Xin ,   School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China
Published: December 2020

The topological transitions in two-dimensional photonic crystals (PCs) originate from the opening-closing-reopening of the bandgap, accompanied with the band order inversion. The topological bandgap in magnetic PC can be created by applying a bias magnetic field or deforming the geometry structure of the PC. In this paper, we demonstrate that the direction of the bias magnetic field also plays a key role in modifying the band structure in a two-dimensional magnetic PC. The results show that by reversing the direction of the bias magnetic field, the eigenstates with the same parity may exchange their orders in the band structure. We investigate this type of band order exchange in the applications of constructing topological edge states and its influence on the properties of edge states. We find, for example, reversing the direction of the bias magnetic field can create two almost degenerated topological edge modes, which propagate in the same direction but have opposite orbital angular momenta. The edge modes and their characteristics can be determined by the schematics of the band orders for the photonic crystals on the two sides of the boundary. The relative relationship of the band orders determines the emergence of the topological edge states, the number of edge states, and edge modes’ properties such as the orbital angular momentum and group velocity. Also, it affects the transmission efficiency of the electromagnetic wave on the boundary. The direction effect of the bias magnetic field on band order exchange presented in this paper provides us with a new way to change the feature of topological edge states and helps us to better understand the influence of band order on topological phases of photonic crystals. It may have potential applications, such as in pseudo-spin splitter and reflection-free one-way optical switch.
The theoretical study of terahertz-streaking photoionization for ultrafast imaging of density matrix in rubidium atom
Authors: Ling Zhong-Huo , Wang Shuai , Zhang Jin-Cang , Zhang Yi-Zhu , Yan Tian-Min , Jiang Yu-Hai ,   Materials Genome Institute, Department of Physics, Shanghai University, Shanghai 200444, China,   Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China,   Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China,   University of Chinese Academy of Sciences, Beijing 100049, China,   ShanghaiTech University, Shanghai 201210, China
Published: December 2020

Terahertz-streaking photoionization can be exploited to resolve ultrafast quantum beating and reconstruct the ultrafast evolution of density matrix. Here, we propose an experimental strategy to implement the method merely with the tabletop femtosecond system and magneto-optical trap reaction microscopy. The probe pulse consists of an ultraviolet pulse with pulse duration of about 30 fs and a strong terahertz pulse with strength of about 2.6 fs in rubidium-atom superposition. The population and coherence terms of the density matrix can be projected into different positions of the photoelectron momentum distribution. The reconstruction algorithm was designed to acquire the ultrafast evolution of density matrix from the time-dependent photoelectron spectrum. The experimental conception can demonstrate the newly proposed transient spectral method only with the commercial femtosecond laser system and magneto-optical trap reaction microscopy, thus preventing the complex laser system, such as extreme ultraviolet free electron lasers and attosecond higher harmonics, allowing a new metrology to explore the coherence dynamics of quantum systems.
Effect of straining flow on growth of columnar crystal in ternary undercooled melt
Authors: Fan Hai-Long , Chen Ming-Wen ,   School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

As an important microstructure, columnar crystal growth technology, especially the growth technology of single columnar crystal plays an important role in improving the performances of semiconductor, optical devices and other related products. In many practical applications, because the alloy is composed of multi-component and there is inevitably flow in the melt, it is necessary to study the growth of columnar crystals in multi-component melt with flow separately. The growth of columnar crystal in a ternary undercooled melt subjected to straining flow under non-isothermal conditions is studied, and the approximate analytical expression for growth morphology of columnar crystal is given by using asymptotic method. It can be seen from the expression that straining flow is an important reason for irregular columnar crystal. When analyzing the effect of straining flow on the growth of columnar crystal in ternary melt, it is found that the incoming flow accelerates the growth velocity of the interface, while the outgoing straining flow reduces the growth velocity of the interface, namely, the straining flow makes the interface of columnar crystal deformed. At the same time, it is found that the interface deformation becomes more intense with the increase of flow velocity. The above conclusion can also be applied to the effect of straining flow on the interface morphology of columnar crystal in pure melt and binary melt. The comparison of the effects of straining flow on the interface of columnar crystal among pure melt, binary melt and ternary melt, shows that the interface morphology of columnar crystal in dilute alloy melt is more affected by straining flow than in the pure melt, but the more components are more easily affected by flow. However, the number of components in melt is not a decisive factor for the change of interface morphology of the columnar crystal, but the constitutional undercooling is an important factor for determining the interface morphology of multicomponent alloy. According to the conclusion of this paper, the influence of straining flow on the interface morphology of columnar crystal growth can be quantitatively predicted, which provides the necessary theoretical guidance in accurately controlling the interface morphology in the future.
First-principles calculations of stabilities and physical properties of ternary niobium borocarbides and tantalum borocarbides
Authors: Hu Qian-Ku , Qin Shuang-Hong , Wu Qing-Hua , Li Dan-Dan , Zhang Bin , Yuan Wen-Feng , Wang Li-Bo , Zhou Ai-Guo ,   Henan Key Laboratory of Materials on Deep-Earth Engineering, School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China
Published: December 2020

Transition-metal light-element compounds are potential candidates for hard materials. In the past, most of studies focused on the binary transition metal borides, carbides and nitrides, while the researches of ternary phases are relatively rare. In this paper, the structure units of the known Nb3B3C and Nb4B3C2 phases are first analyzed to be Nb6C octahedron and Nb6B triangular prism, respectively. By stacking the Nb6C octahedron and Nb6B triangular prism, twenty ternary Nb-B-C and twenty ternary Ta-B-C configurations with different compositions are constructed. The chemical formula of these Nb-B-C and Ta-B-C configurations can be defined to be Nb(m + n + 2)B(2m + 2)Cn and Ta(m + n + 2)B(2m + 2)Cn, respectively. Using first-principles density functional calculations, thermodynamical, dynamical and mechanical stabilities of the constructed ternary Nb-B-C and Ta-B-C configurations are investigated through calculating their enthalpies of formation, phonon dispersions and elastic constants. Five Nb-B-C (Nb3B3C, Nb4B3C2, Nb6B4C3, Nb7B4C4 and Nb7B6C3) phases and six Ta-B-C (Ta3B3C, Ta4B3C2, Ta6B4C3, Ta7B4C4, Ta7B6C3 and Ta3BC2) phases are predicted to be stable by analyzing the constructed ternary Nb-B-C and Ta-B-C phase diagrams, in which the seven phases (Nb6B4C3, Ta3B3C, Ta4B3C2, Ta6B4C3, Ta7B4C4, Ta7B6C3 and Ta3BC2) are first predicted to be stable. The Nb6B4C3, Ta6B4C3, Ta4B3C2 and Ta3B3C phases are stable when temperature is higher than 1730, 210, 360 and 1100 K, respectively. And the Ta3BC2 phase is stable only when temperature is lower than 130 K. The calculated results about mechanical and electric properties show that these Nb-B-C and Ta-B-C phases are conductive materials with a high hardness in a range of 23.8–27.4 GPa.
High-power 1.6 μm noise-like square pulse generation in an all-fiber mode-locked laser
Authors: Dou Zhi-Yuan , Zhang Bin , Liu Shuai-Lin , Hou Jing ,   College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China,   State Key Laboratory of Pulsed Power Laser Technology, Changsha 410073, China,   Hunan Provincial Key Laboratory of High Energy Laser Technology, Changsha 410073, China
Published: December 2020

We demonstrate generation of high-power and large-energy noise-like square pulses at 1612 nm in an all-fiber dumbbell-shaped mode-locked Er: Yb co-doped double-clad fiber (EYDF) laser. The custom couplers with high power handling keep the laser function well. Large-mode-area EYDF with high power handling and enough high pump power make it possible to obtain high output power in the oscillator. Compared with figure-eight structure, strictly all-fiber dumbbell-shaped structure without isolator and optimizing splicing loss could reduce intra-cavity loss and improve optical to optical efficiency, which could reduce heat accumulation and enhance the power carrying capacity of EYDF. In order to study the influence of in-band absorption on output wavelength, EYDF1 and EYDF2 with different in-band absorption coefficients are accessed to intracavity, respectively. It is directly demonstrated that regulation of in-band absorption is an effective way to control the output wavelength. Strong in-band absorption could restrain the emission of C-band and make the wavelength range above 1.6 μm obtain enough gain. Linear insertion loss is another important factor to affect the emission wavelength in EYDF fiber laser. At pump power of 8 W, maximum average output power with emission wavelength above 1.6 μm can reach 1.16 W, corresponding to a single pulse energy of 1.26 μJ. SNR of output pulse is 70 dB which indicates the high stability of mode-locking. In order to verify and evaluate influence of insertion loss on the output characteristics of mode-locked laser, a variable attenuator is inserted in experimental setup, allowing us adjust the linear loss of the cavity. By increasing pump power and adjusting PCs, mode-locked pulses could be obtained on the condition of large additional insertion loss. Even though ~ 10 dB additional insertion loss is introduced, the oscillation still could function at 1612 nm and keep stable mode-locked state. This result demonstrates our oscillation could bear strong additional loss and own strong robustness. If excessively large additional insertion loss is added, 1566 nm becomes the central emission wavelength and wavelength component at 1612 nm almost disappears. Our investigation supplies a direct guideline to design high-power fiber laser with emission wavelength above 1.6 μm.
Three-dimensional transmon coherence measurement method based on network analyser
Authors: Wu Xiao-Yu , Zhao Hu , Li Zhi ,   College of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China,   AVIC Xi’an Flignt Automatic Control Research Institute, Xi’an 710065, China
Published: December 2020

Three-dimensional(3D) transmon is a kind of superconducting qubit with long decoherence time, which has important applications in superconducting quantum computation, quantum optics, cavity quantum electrodynamics, et al. Rabi oscillation is a vital method to characterize the decoherence time of quantum system, and it is also a basic experiment to demonstrate the energy level evolution of quantum system. In order to test the Rabi oscillation of 3D transmon, strict timing control is necessary, and the process of testing and debugging is complicated. In this paper, 3D transmon samples are fabricated and their basic parameters EC = 348.74 MHz and EJ = 11.556 GHz are tested and characterized. The coupling coefficient g2/Δ between qubit and the 3D cavity is 43 MHz, which is located in the dispersive regime. The qubit’s first transition frequency f01 = 9.2709 GHz, and the second transition frequency f12 = 9.0100 GHz. The 3D resonator is fabricated by the material 6061T6 aluminum, the loaded quality factor is 4.8 × 105, and the bare frequency of the resonator is 8.108 GHz.

Through comparison, it is found that the Rabi oscillation time obtained by the proposed method is shorter than by the Jaynes-Cummings method. The main reasons are as follows. First, the measurement of network analyzer is a continuous measurement, and the test signal always affects the decoherence process of 3D transmon. Second, the quantum bit is in the ground state after decoherence, and the ground state measured by the network analyzer accounts for a relatively high proportion, which causes the curve measured by the network analyzer to be one-sided attenuation oscillation. Third, the dispersive readout method is related to the quality factor of the superconducting cavity. The storage time of microwave photons in the superconducting cavity is longer than the decoherence time of 3D transmon, so the quantum information is partially decohered before leaving the superconducting cavity, which will shorten the Rabi oscillation time.

An innovative Rabi oscillation test method based on network analyzer is presented. The test system based on this method is simple to build and can be used as a new way to quickly verify whether 3D transmon has quantum characteristics. This method can also be extended to other quantum systems for preliminarily verifying the time domain characteristics.