bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulating Ca2+ photoactivation of nerve cells by near-infrared light
Authors: Geng Jun-Xian , Li Shao-Qiang , Wang Shi-Qi , Huang Chun , Lü Yun-Jie , Hu Rui , Qu Jun-Le , Liu Li-Wei ,   Ministry of Education/Guangdong Key Laboratory of Optoelectronic Devices and Systems, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
Published: December 2020

Calcium ions (Ca2+) play a key role of the nerve cells generating universal intracellular signals and controlling important functions. Ca2+ activation is of great significance for explaining the subcellular-level biological process. Light stimulated nerve cells to control intracellular signals and membrane activities has become a main method in neuroscience, and the photoactivation is one of the main ways to study intracellular Ca2+ transmission. Nerve cells can be directly stimulated by light to produce action potentials, but such techniques are inaccurate in the delivered light energy. To improve this, here in this work we show that gold nanorods (GNRs) can be conjugated to ligands to bound to human neuroblast cells (SH-SY5Y), and introduce an optical method of stimulating and monitoring Ca2+ signal in nerve cells in which the plasmonic excitation of GNRs is used. In this paper, we use confocal microscopy to display the 488 nm continuous wave laser irradiating SH-SY5Y cells with Ca2+ indicator (Fluo-4, AM) to check fluorescence. Near-infrared pulsed light at the plasmon resonance absorption peak of GNRs is used to stimulate Ca2+ signal transduction in SH-SY5Y labeled with GNRs, and Fluo-4, AM is used for two-photon excited fluorescence imaging. In addition, we use the pulsed laser with power of 0.5 mW and a wavelength of 800 nm. The Ca2+ activation can be achieved in 10 s on average. The release rate of Ca2+ from SH-SY5Y cells labeled with GNRs is 6 times that without GNRs. Next, in order to determine the source of changes in Ca2+, we use the BPATA to deplete the intracellular Ca2+, after 5 min, 200 μmol/L Ca2+ solution is added, and its ΔF/F is found to be more than 1.5 times that without GNRs. Thus, we believe that GNRs could enhance photoactivation through local surface plasmon resonance induced membrane depolarization and generate an action potential. The results prove the feasibility of using GNRs to enhance the activation of Ca2+ in nerve cells, and provide an optical means of lower photodamage and more precise for studying nerve cell ion channels. Our study demonstrates that enhancing photoactivation by GNRs could provide an outlook of basic research in neuroscience.
Molecular dynamics study of interface thermal resistance in asymmetric nanochannel
Authors: Mei Tao , Chen Zhan-Xiu , Yang Li , Zhu Hong-Man , Miao Rui-Can ,   School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
Published: December 2020

Heat transfer in a micro-scale system has less thermal inertia and faster thermal response, which has unique advantages in controlling heat transfer. Interface thermal resistance is an important physical quantity that reflects the heat transfer performance of the interface on a micro-scale. In this paper, the interface thermal resistance os static fluid and flowing fluid in nanochannel, which are different in the wall temperature and wettability, are studied by the molecular dynamics method. In the static fluid, the results show that the wall wettability has a significant influence on the interface thermal resistance, and the stronger the wall wettability, the smaller the values of interface thermal resistance is. For the walls with different temperatures, it can be observed that the interface thermal resistance on high temperature wall is higher than that on low temperature, when the wall wettability is weaker. On the contrary, when the wall wettability is stronger, the effect of wall temperatures on the interface thermal resistance is negligible. An external force applied to the fluid domain makes the fluid flow. In the flowing fluid, the results show that the variation of wall wettability and external force can lead to the slip to different degrees at the interface, and the slip-induced frictional viscous heat is generated at the solid-liquid interface, and thus increasing the fluid temperature and the heat flux of the system. The effect of external force on the thermal resistance is limited by the wall wettability. When the wall wettability is weaker, the increase of the external force will make the interface slip more easily and the thermal resistance decrease. With the stronger wall wettability, it is difficult to make the interface slip obviously with the increase of external force, and the influence of external force on interface thermal resistance decreases. The heat transfer performance at the solid-liquid interface is related to the number of fluid molecules adsorbed on the wall surface. The results show that in the static fluid, the increase of wall wettability will make more fluid molecules adsorbed on the wall, and the arrangement becomes more and more regular, which causes the interface thermal resistance to decrease and is beneficial to the interface heat transfer. In the flowing fluid, the change of external force has less influence on the number of adsorbed molecules, and the wall wettability is the main factor affecting the adsorption of fluid molecules on the wall.
Enhanced-visual-cryptography-based optical information hiding system
Authors: Yu Tao , Yang Dong-Yu , Ma Rui , Zhu Yu-Peng , Shi Yi-Shi ,   School of Optoelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Recent years, with the rapid development of information technology, the information security has received more and more attention. A variety of encryption methods to protect the information have been reported. Visual cryptography is one of the encryption methods, which has highly security because of its threshold feature. And the cryptographic information can be explained by a naked eye in the decryption process. In the application of visual cryptography, however, each shared image is limited to transparency films and overlapping on computer. In our previous work, we proposed the scheme of invisible visual cryptography and developed the visual-cryptography-based optical hiding system (VCOH), which transformed the conventional visual cryptography shares into diffraction optical elements (DOEs). It not only increases the application range of visual cryptography, but also enhances security. In this paper, we propose an optical information hiding system based on the extended visual cryptography, which inherits the concept of invisible visual cryptography. In contrast to our previous work, the method proposed in this work can hide a meaningful image instead of text messages. Meanwhile, the capacity and imperceptibility of the method are greatly increased. The hiding process of the system contains two steps. Firstly, the secret image is converted into meaningful shares through the extended visual cryptography algorithm. Secondly, the meaningful shares are able to hide in phase-keys through an iterative phase retrieval algorithm, such as Gerchberg-Saxton algorithm and Yang-Gu iterative algorithm. Then the phase-keys can be made into diffraction optical elements (DOEs) to store and transport in a physical way. In the decryption process, DOEs are illuminated with the laser beam to reconstruct the meaningful shares. The secret image can be explained by the direct overlapping of the reconstructed shares without any optical or cryptographic knowledge. The simulation and optical experimental results show that the proposed method has good performance of security and validate the feasibility of the proposed method. Besides, in this paper the robustness and security issues are also analyzed. This system has a high security because of its indistinguishability under adaptive chosen ciphertext attack (IND-CCA2) security. Additionally, this system is relatively less robust than the VCOH because it shares meaningful images with highly complex and detailed structures.
Application of Ge50Te50/Zn15Sb85 nanocomposite multilayer films in high thermal stability and low power phase change memory
Authors: Zhu Xiao-Qin , Hu Yi-Feng ,   School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China
Published: December 2020

The Ge50Te50/Zn15Sb85 nanocomposite multilayer films are prepared by the magnetron sputtering. The variation of resistance with temperature and with crystallization activation energy is studied. The multilayer structure of the section before and after the crystallization for Ge50Te50/Zn15Sb85 nanocomposite multilayer film is compared by transmission electron microscope. The phase change memory device based on [GT(7nm)/ZS(3nm)]5 is manufactured, and the electrical performance is measured. The fast switching speed, low operating power consumption, and good cycling performance are achieved for Ge50Te50/Zn15Sb85. Ge50Te50/Zn15Sb85, which is a kind of nanocomposite multilayer film, a promising phase change storage material with high thermal stability and low power consumption.
Study of nano particle stripping and composition inspection on wafer surface
Authors: Liu Li-Tuo , Wang Chun-Long , Yu Xiao-Ya , Shi Jun-Kai , Li Yao , Chen Xiao-Mei , Zhou Wei-Hu ,   Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100094, China,   Liberation Army 32180, Beijing 100012, China,   Key Laboratory of Experimental Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

Nano-scale particle stripping and inspection on silicon wafer are critical issues for Integrated Circuit(IC) manufacture industry. As more new materials are used in IC manufacture, not only particle itself but also its composition should be inspected. Particles are mainly adhered by the van der waals force. One of potential particle desorption method is laser cleaning which is environment friendly. However, the mechanism of laser cleaning is not clear and more studies should be done for laser ablation. In this paper, the kinetic process of nano particle on silicon wafer induced by nanosecond pulsed laser as well as the on-line detection method of particle composition were studied. A potential method of nano particle dynamic analysis and particle composition inspection were presented. A dual nanosecond pulse laser system both wavelengths at 532 nm is designed in which one laser pumps the particles away from wafer surface almost without damage, the other laser breakdowns the particles in air above the wafer surface to obtain the emission lines of the contaminated particles of 300 nm Cu by a spectroscopy with CCD. Particle motion trail in z direction was observed after laser cleaning by analyzing particle spectral features. The particle dynamic model after stripping was established in which the resistance of air collision and gravity were included. And the model parameters were obtained by calculation using experimental results. The initial velocity of particle at the end of laser pulse and the average acceleration during laser interaction were calculated which were 7.6 m/s and 7.6 × 108 m/s2 respectively. The sensitivity of the dual laser system was evaluated which was between 2.1 × 1013 to 5.1 × 1013 atoms/cm2. As result, it is found that the gravity of the particle should not be ignored and the velocity divergence between different stripping particles is existed. The study not only provides a methodology for the study of laser-induced removal of nano particles on the wafer surface and laser induced nano particle dynamics, but also provides a potential method for the inspection of particle composition and pollution source monitoring on line in integrated circuit manufacture process. As the results were not the optimum one and further study should be done in which a better laser power density should be used.
Analysis of frequency tuning process of dual coupled optical microcavities
Authors: Xu Xin , Jin Xue-Ying , Gao Hao-Ran , Cheng Jie , Lu Yang , Chen Dong , Yu Lian-Dong ,   School of Instrument Science and Opto-electronics Engineering, Hefei University of Technology, Hefei 230009, China
Published: December 2020

Different frequency detuning can excite different working mode in a dual coupled optical microcavities. Based on the nonlinear Schrödinger equations of dual coupled field, and by using the split-step Fourier method, the optical field evolution in the microcavities is analyzed under the condition of both positive and negative tuning, and various optical distributions are generated in the process of frequency tuning. Simulation results indicate that the field can develop into the bright soliton in the region of positive tuning. However, the region in which the bright soliton is maintained is small, and the field in the microcavities grows into direct current (DC) distribution because of the serious frequency detuning. In the region of negative tuning, the field of “turning pattern” with high power is generated. There is only chaos inside the microcavities without frequency detuning or the detuning parameters close to 0. In addition, under the condition of strong coupling, the bright soliton and the “turning pattern” cannot be excited. Even stronger coupling leads to optical field in the form of DC directly. After the bright soliton exciting in the microcavity, it can be preserved by selecting appropriate detuning parameters and pump power. Moreover, the bright soliton can be changed into “turning pattern” with low power by continuously changing the detuning parameter of the first microcavity. Theoretical analyses are significant for experimental research on the dual coupled microcavities.
Piezoelectric and electrocaloric properties of high performance potassium sodium niobate-based lead-free ceramics
Authors: Wei Xiao-Wei , Tao Hong , Zhao Chun-Lin , Wu Jia-Gang ,   College of Materials Science and Engineering, Sichuan University, Chendu 610065, China
Published: December 2020

Piezoelectric ceramics, as a kind of functional material, can realize the mutual transformation between mechanical energy and electrical energy, and has been widely used in civil and military fields. With the improvement of people's awareness of environment protection and self-health care, the study of lead-free piezoelectric ceramics with excellent performance and environmental friendliness has become an urgent task. Among several kinds of lead-free piezoelectric materials, potassium sodium niobate [(K, Na)NbO3, KNN]-based ceramics has attracted much attention due to its good comprehensive properties, but there have been carried out few studies focusing on the utilization of phase boundary to regulate the properties of high piezoelectric and electrocaloric effect simultaneously. In this work, lead-free 0.944K0.48Na0.52Nb0.95Sb0.05O3 -0.04Bi0.5(Na0.82K0.18)0.5ZrO3-1.6%(AgxNa1–x)SbO3-0.4%Fe2O3 ceramics is prepared via the conventional solid-state method, and the effect of AS/NS ratio on phase structure, electrical properties, and electrocaloric effect are studied. The obtained results show that the ceramics has a multiphase coexistence with “rhombohedral-orthorhombic-tetragonal” (R-O-T) in all compositions. With the increase of AS content, the piezoelectric and ferroelectric properties of the ceramics fluctuate (d33 = 518–563 pC/N, kp = 0.45–0.56; Pmax = 21–23 μC/cm2, Pr = 14–17 μC/cm2). In addition, the electrocaloric effect (ECE) for each of the samples is studied by the indirect method. Broadening temperature span (～90 K) of electrocaloric effect is obtained in the vicinity of O-T phase transition region, while a low ECE value is observed. A stronger ECE peak (ΔTmax > 0.6 K) can be observed when the measurement temperature reaches near the Curie temperature. Consequently, both large piezoelectric property and high electrocaloric performance can be realized in KNN-based ceramics by new phase boundary construction.
Phasor analysis of fluorescence lifetime data and its application
Authors: Lin Dan-Ying , Niu Jing-Jing , Liu Xiong-Bo , Zhang Xiao , Zhang Jiao , Yu Bin , 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

Fluorescence lifetime imaging microscopy (FLIM) is widely used in biomedical, materials and other fields. It not only has strong specificity and high sensitivity, but also has the capability of quantitative measurement because the fluorescence lifetime is not affected by the intensity of excitation, the concentration of fluorophores and photobleaching, and consequently is able to monitor the changes of microenvironment and reflecting the interaction between molecules. However, its application is limited to some extent by the complexity of data analysis. In order to make FLIM technology more suitable for fast analysis of high-throughput data, a variety of new algorithms for fluorescence lifetime analysis have emerged in recent years, such as phasor analysis, maximum likelihood estimation, first-order moment, Bayesian analysis, and compressed sensing. Among them, the phasor analysis (PA) method obtains the fluorescence lifetime by converting the fitting in the time domain to the direct calculation in the frequency domain. Compared with traditional least-square fitting method, it is not only simpler and faster, but also more suitable for the case of low photon counts. In addition, in the PA approach to FLIM, the fluorescence decay is directly converted into a phasor diagram by simple mathematics, where the phasor points originating from different pixels in the image are represented by the positions in the phasor plot, and thus the graphical representation obtained by PA method is convenient for data visualization and cluster analysis. Therefore, it has become a simple and powerful analysis method for FLIM, and is increasingly favored by researchers. In this paper, the basic principle of PA method and how we can use it are described in detail. And on this basis, the latest application research progress of the method in cell metabolism state measurement, protein interaction study, cell microenvironment measurement, auxiliary pathological diagnosis, and resolution improvement in super-resolution imaging are introduced and summarized. The advantages of PA method in these FLIM applications are focused on, providing useful reference for the research in related fields. Finally, the phasor analysis method for FLIM data analysis and the development trend of its application are prospected.
Morphology control of zinc oxide nanorods and its application as an electron transport layer in perovskite solar cells
Authors: Zhang Chen , Zhang Hai-Yu , Hao Hui-Ying , Dong Jing-Jing , Xing Jie , Liu Hao , Shi Lei , Zhong Ting-Ting , Tang Kun-Peng , Xu Xiang ,   School of Mathematics and Physics, China University of Geosciences (Beijing), Beijing 100084, China
Published: December 2020

 ZnO is a promising electron transport material. It has not only similar energy level position and physical properties to traditional TiO2, but also excellent light transmittance, conductivity, stability, low cost and low temperature preparation. Studies have shown that the one-dimensional nanostructured electron transport layer has a higher electron transport rate, provides a direct electron transport channel and avoids its being recombined at the grain boundaries, thereby improving carrier collection efficiency. It has also been reported that the electron transport rate of ZnO nanorods is significantly better than that of TiO2, showing their great potential applications. In perovskite solar cells, the verticality of ZnO nanorods is a key factor affecting device efficiency. The AZO (ZnO∶Al) glass, as an inexpensive transparent conductive substrate, is expected to obtain the best verticality because it has no lattice mismatch with ZnO nanorods. And in the field of perovskite solar cells, the light absorbing layer is usually prepared in a glove box and it has obviously not been industralized. However, there are few reports about perovskite solar cells prepared in atmospheric environment with AZO as substrate and ZnO nanorods as electron transport layer. And it is still much less efficient than the current perovskite solar cells with TiO2 as the electronic transport layer. It can be seen that further improving the efficiency of the structural battery prepared in the atmospheric environment is an urgent problem to be solved.

 In this paper, ZnO nanorods are prepared as an electron transport layer by the hydrothermal method. The effects of hydrothermal temperature, the number of seed layer, the precursor concentration, the substrate type, the hydrothermal time, and the other process parameters on the morphology and crystalline properties of ZnO nanorods are systematically studied, and the growth mechanism is analyzed. The results show that the length of the nanorods is mainly controlled by the hydrothermal time and hydrothermal temperature, and that the radial size is mainly determined by the number of seed layers and the concentration of the precursor solution. And the results also indicate that the verticality of ZnO nanorods’ growth is closely related to the substrate, and that the ZnO nanorods on the AZO substrate have the best growth verticality. On this basis, the perovskite solar cell is prepared in the atmospheric environment, and the optimal efficiency of the photovoltaic device prepared with AZO substrate increases from 7.0% reported in the literature to 9.63%. This is of great significance for enriching the design ideas of perovskite solar cells and further reducing costs.
Thermal annealing effects of InGaAs (1.0 eV) and InGaAs (0.7 eV) sub-cells of inverted metamorphic four junction (IMM4J) solar cells under 1 MeV electron irradiation
Authors: Zhang Yan-Qing , Qi Chun-Hua , Zhou Jia-Ming , Liu Chao-Ming , Ma Guo-Liang , Tsai Hsu-Sheng , Wang Tian-Qi , Huo Ming-Xue ,   Space Environment Simulation and Research Infrastructure, Harbin Institute of Technology, Harbin 150001, China,   School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China,   Institute of Microelectronics, Chinses Academy of Sciences, Beijing 100029, China
Published: December 2020

In this work, thermal annealing effects of InGaAs (1.0 eV) and InGaAs (0.7 eV) sub-cells for inverted metamorphic four junction (IMM4J) solar cells after being irradiated by 1 MeV electrons are investigated by using light I-V characteristic, dark I-V characteristic and spectral response. Annealing temperature range is 60–180 ℃ and annealing time is 0-180 min. The results indicate that the open-circuit voltage Voc, short-circuit current Isc, and maximum power Pmax of two sub-cells are gradually recovered with annealing time increasing, and the rate of recovery increases with annealing temperature increasing. Besides, the recovery rate of InGaAs (1.0 eV) sub-cell is less than that of InGaAs (0.7 eV) sub-cell under the same annealing temperature and time. Double exponential model is used to fit the dark I-V curve for the key parameters (the serial resistant Rs, the parallel resistant Rsh, the diffusion current Is1 and the recombination current Is2). It is found that Rs, Is1 and Is2 of two sub-cells decrease gradually and Rsh increases during annealing and the rate of recovery increases with annealing temperature rising. However, the recovery of Is1 and Is2 of InGaAs(1.0 eV) are much greater than that of InGaAs(0.7 eV). The equivalent model between short-circuit current density (Jsc) and defect concentration (N) induced by irradiation and annealing is established. N changes follow the first reaction kinetics, and the rate constant follows the Arrhenius equation with the annealing temperature. Therefore, the thermal annealing activation energy of InGaAs(1.0 eV) and InGaAs(0.7 eV) sub-cells are 0.38 eV and 0.26 eV, respectively. These efforts will contribute to the IMM4J solar cells, in particular, to space-based applications.
Phenomenon study on heat induced atomization of acoustic levitated methanol droplet
Authors: Wei Yan-Ju , Zhang Jie , Deng Sheng-Cai , Zhang Ya-Jie , Yang Ya-Jing , Liu Sheng-Hua , Chen Hao ,   School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China,   State Key Laboratory of Mechanical Strength and Vibration, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China,   School of Automobile, Chang’an University, Xi’an 710064, China
Published: December 2020

Atomization of droplets is ubiquitous in many natural and industrial processes, such as falling rain drops, inkjet printing, fuel injection in automotive and gas-turbine engines. Acoustic irradiation provides a very effective method of atomizing fluid. However, the acoustic atomization of acoustically levitated droplet is seldom studied. To assess the possibility of achieving ultrafine atomization, we, in this paper, systematically study the atomization of an acoustically levitated droplet placed in a hot gas of a flame. High speed camera is utilized to investigate the atomization characteristics of various droplets with diameters ranging from 0.5 mm to 3.5 mm.

The experimental results show that the sound pressure of the resonance acoustic field has the ability to atomize the droplet when it is suddenly bathed in hot gas. Here the heating acts as a switch to convert the droplet surface from an acoustic isolator to conductor by heating the surface to strong evaporation. The presence of a high concentration of vapor molecules surrounding the droplet caused the acoustic field to change, thus, a much larger pressure gradient is established along the droplet surface, resulting in the atomization of droplet from the equator. Furthermore, Faraday wave stimulation and discretization on the film cause the droplet to further disintegrate when the droplet diameter is large enough. The atomization consists of three different styles, i.e. rim spray (RS), film disintegration (FD) and normal sputtering (NS). When exposed to hot gas, the droplets with equivalent diameter D0 < 2.8 mm are depleted with RS until the whole mass is atomization. A thin rim is extruded at the equator and then splashed in the equator plane, the spray speed is around 9.5 m/s. Larger droplets end with the sudden FD of liquid film of the residual mass after the the RS has been consumed up. When the thickness of the rim and buckled film decrease to half of wave length, Faraday wave emerges, resulting in the vertical droplet ejection and the disintegration of the thin films. And the droplets with D0 > 3.2 mm undergo further film buckling, forming a closed bubble due to the Helmholtz resonator effect and NS at the bottom. This sound driven atomization of droplets enriches the understanding of fluid mechanism in multi-physical fields, and may provide new ideas for relative application research.
Efficient and stable blue perovskite light emitting diodes based on defect passivation
Authors: Wu Hai-Yan , Tang Jian-Xin , Li Yan-Qing ,   Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou 215123, China,   School of Physics and Electronics Science, Ministry of Education Nanophotonics & Advanced Instrument Engineering Research Center, East China Normal University, Shanghai 200241, China
Published: December 2020

Solution-processable metal halide perovskites materials have many advantages, such as adjustable band gap, high photoluminescence quantum yield (PLQY), high color purity, high carrier mobility, low temperature solution process, excellent charge transport property and so on. These make them potential application in the display field. In the past few years, the device performance of perovskite light emitting devices (PeLEDs) have been greatly improved by manipulating the perovskite microstructures through various strategies, such as stoichiometry control, dimensional engineering, defect passivation and so on. At present, except for blue PeLEDs, the external quantum efficiencies (EQEs) over 20% have been achieved for green, red, and near-infrared PeLEDs. The low efficiency of blue PeLEDs is retarding their potential applications in full-color display and solid-state lighting. The main reasons in blue PeLEDs are the poor film coverage of blue perovskite materials and the spectral instability during device operation. In order to improve the quality of perovskite film and device performance, the quasi two-dimensional perovskite materials phenylethylammonium cesium lead bromide chloride (PEAxCsPbBr3–yCly) are used as the main perovskite emission material, by partially replacing Br with Cl to enlarge their bandgap to achieve the blue emission. The Lewis base polyethyleneglycol (PEG) is introduced to passivate the surface trapping defects and improve perovskite film coverage. The potassium bromide (KBr) is introduced to reduce perovskite grain size, suppress mobile ion migration and exhibit excellent spectral stability. Dual additives PEG and KBr are incorporated into the quasi-2D blue perovskite for inhibiting the nonradiative losses by passivating the traps in the perovskite films. Eventually, the PEAxCsPbBr3–yCly + PEG + KBr based blue PeLEDs with the emission peak of 488 nm are accompanied, which maximum brightness, current efficiency, and external quantum efficiency reached 1049 cd·m–2, of 5.68 cd·A–1, and of 4.6%, respectively, with high color purity (the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates is (0.0747, 0.2570)) and the narrow full width at half maximum (FWHM) of 20 nm. Compare to the devices without additives, the efficiency has increased by nearly 3 times. Furthermore, the devices also show better spectral stability and operation lifetime. This work provides an effective method of blue PeLEDs toward the practical applications.
Effect of laser illumination conditions on focusing performance of super-oscillatory lens
Authors: Liu Kang , He Tao , Liu Tao , Li Guo-Qing , Tian Bo , Wang Jia-Yi , Yang Shu-Ming ,   State Key Labortory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

Super-oscillatory lens (SOL), a new type of planar optical element developed in recent years, may play an important role in the integrated optics, microscopy, advanced sensor, and astronomy. Based on the vectorial angular spectrum theory and genetic algorithm, both binary amplitude-type and phase-type SOLs are designed. Various sub-diffraction focusing properties can be realized by optimizing the design procedure. In order to investigate the focusing characteristics of SOLs under different illumination conditions, rigorous electromagnetic simulation calculations of the diffracted focusing light field are implemented by the finite-difference time-domain method. The results show that when the beam waist radius w0 of the illuminating laser is less than the SOL radius a, not only the capability of super-diffraction limit focusing will decrease significantly, but also the intensity of the focal spot will attenuate by more than 50%. Comparing with the amplitude-type SOL, the waist radius w0 has a strong effect on the phase-type SOL and causes a significant focus to shift in the positive direction. However, if w0 is larger than 2a, the ideal focusing characteristics of SOL can be maintained. Under the condition of oblique illumination, the high numerical aperture amplitude-type SOL generally only allows a small inclination angle of less than 10°, while the phase-type SOL has a wide inclination adaptability (can exceed 40°) regardless of the numerical aperture. For the latter, the focal spot will expand laterally and the intensity will decrease sharply with the increase of inclination angle. As for low numerical aperture phase-type SOL, the focusing characteristics, including focal spot size, focusing intensity and the angular position of the focus, can keep stable within an inclination angle of 18°. For imaging infinitely distant objects, the oblique illumination will produce a fluctuating field curvature and significant negative distortion for high numerical aperture SOLs, while for the low numerical aperture SOLs, the field curvature increases with inclination angle increasing and the distortion disappears almost. The research results of this paper provide an important theoretical basis for practical applications of super-oscillatory lens in the fields of sub-diffraction light focusing, super-resolution microscopic imaging, and micro-nano processing of femtosecond laser direct writing.
Deposition and growth mechanism of graphene on copper crystal surface based on molecular dynamics simulation
Authors: Bai Qing-Shun , Dou Yu-Hao , He Xin , Zhang Ai-Min , Guo Yong-Bo ,   School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin 150000, China
Published: December 2020

Chemical vapor deposition (CVD) is an essential method of depositing and fabricating large-area and high-quality graphene. In this work, molecular dynamics (MD) simulation technology is adopted to simulate the fabrication of graphene on the copper (111) crystal surface by chemical vapor deposition method. In order to eliminate the adverse effects of traditional MD method, an adapted potential system between carbon and copper atoms is introduced into the modeling of deposition and growth simulation of graphene. The results reveal the microscale growth mechanism of the graphene depositing on Cu(111) crystal surfaces, and the influence of temperature and carbon deposition rate (CDR) on the quality of graphene. The simulation results indicate that the deposition and growth of graphene consists of two stages. The first stage is to form binary carbons, trinary carbons and carbon chains. The second stage is to form carbon rings and the defects healing. The research results also reveal that high temperature can provide the carbon atoms with sufficient energy, which can help the carbon atoms to skip the energetic barrier between the two stages, and then achieve the deposition and growth of graphene. Moreover, the influence of temperature and carbon deposition rate are investigated in detail. The temperature mainly affects the defects and the flatness of graphene. The defects of graphene are the least and the surface can become the flattest at a deposition temperature of 1300 K. Higher temperature can cause the carbon atoms to irregularly move, and lower temperature can suppress the catalysis of the copper substrate. Both the higher and lower temperature can degrade the quality of the graphene surface. The CDR can influence the defects of graphene in growth. The lower value of CDR can lead to local growth on the graphene surface because of the lower nucleation density while the higher CDR is also able to cause the defects to form because of the uneven free energy distribution on the copper surface that has thermal fluctuation. It is shown that graphene can present the flattest surface when the value of CDR is set to be 5 ps–1. According to the simulation process of deposition, it validates that the bi-layer and multi-layer graphene may grow based on the deposition of original single layer of graphene. As to the deposition and growth practice, it is suggested that the temperature 1300K should be suitable for the graphene CVD process of Cu(111) surface. The results in this work can provide a reference for understanding and implementing the fabrication of graphene on the Cu substrate by CVD methods.
Selection of whispering-gallery modes and Fano resonance of prolate microbottle resonators
Authors: Wang Meng-Yu , Meng Ling-Jun , Yang Yu , Zhong Hui-Kai , Wu Tao , Liu Bin , Zhang Lei , Fu Yan-Jun , Wang Ke-Yi ,   Key Laboratory of Nondestructive Test, Ministry of Education, Nanchang Hangkong University, Nanchang 330063, China,   Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Optical microresonators supporting whispering-gallery modes have been intensively studied in past decades due to their practical applications ranging from fundamental science to engineering physics. Among such microresonators, microsphere resonators have been demonstrated to possess ultra-high quality (Q) factor, however, their shapes usually become non-standard spherical body, leading to irregular resonant spectra. Microring resonators have unique potential in integraibility on chip, but the fabrication imperfection limits their Q-factor only to 106. In addition, the free spectral range (FSR) just depends on their radius. Due to the advantages of high Q-factor, standard shape, slender mode field distribution, the microbottle resonators are demonstrated to possess excellent performance in cavity quantum dynamics, nonlinear optics, high-sensitivity sensing, and micro-laser.

In this paper, we carry out a systematic study on the spectral characteristics of prolate microbottle resonator theoretically and experimentally. First, theoretically, the field distribution theory of the microbottle resonator is studied in detail based on Helmholtz equation. Experimentally, prolate microbottle resonators are fabriated via arc discharge technology. Second, the radial modes and axial modes of the microbottles are efficiently excited with the help of a coupled tapered fiber waveguide. By adjusting the coupling gap between the microbottle and the waveguide, The controlling of three cupling states i.e. undercoupling, critical coupling and overcoupling are realized. In our experiment, the whispering-gallery modes excited are identifiable and recognizable. The resonant mode with an ultra-high Q-factor of up to 1.78 × 108 is achieved. The characteristic of ultra-high Q-factor makes the microbottle hold great potential in biochemical sensing, nonlinear optics, and micro-laser. The tuning stability is enhanced by keeping the waveguide in touch with the microbottle. We investigate the selective excitation of whispering-gallery modes by adjusting different coupling points. As a result, clean spectra with robust coupling are observed. The stable device is suitable for improving the sensing performance. Finally, Fano resonance effect is obtained by choosing the diameter of the tapered fiber waveguide. The results presented in this paper will be of great significance for enhancing the sensing, nonlinear optics and cavity quantum dynamics.
Physical problems of diffraction waveguide used in large field of view
Authors: Wu Rong , Sun Ming-Ying , Zhou Shen-Lei , Qiao Zhan-Feng , Hua Neng ,   National Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Published: December 2020

Diffraction gratings have been widely used in waveguides. They can transmit light beams or images from the in-coupling end to the out-coupling end at predetermined positions. However, when they are applied to augmented reality and virtual reality with large field of view and color light sources, there will arise some problems such as mismatch and missing field of view, non-uniform emission, and others. Therefore, starting from these physical problems, the upper limit of the field of view for diffractive waveguide and the complete theoretical boundary formula of the field of view are derived, and on this basis, in-depth research is conducted on monochromatic waves and multicolor waves, respectively. It is concluded that the single-layer diffractive waveguide supports the theoretical upper limit of the monochromatic wave field angle of about 48° under normal high refractive index of n = 1.75, and supports the theoretical upper limit of the multicolor wave field angle of 26.4° for coefficient q = 1.3. Clearly, a larger field of view requires a higher refractive index n and a smaller q value. The boundary conditions of field integrity indicate that reducing the maximum diffraction angle of the long wave and thinning the thickness of the waveguide layer can solve the problem of missing field of view. The practical maximum diffraction angle generally does not exceed 75°, and the thickness of the waveguide layer is about 0.5 to 1.0 mm generally based on the incident field of view. Finally, a method of expanding each total internal reflection field of view into a ray tracing diagram and a distribution function of pupils to receive light energy at various angles are obtained. In this way, the optimal position of the out-coupling grating region can be achieved, and the inverse of the distribution function is used to constrain the angular distribution of the projected light or the grating efficiency, and then receiving uniform exit image at any position becomes possible. The uniformity of the monochromatic waveguide increases from 0.27 to 0.15, and the uniformity of the long wave in the single grating multicolor waveguide rises from 0.4 to 0.28. The results of these studies will undoubtedly help to solve the problem in the diffractive waveguides used in large field of view and multicolor light.
Bipartite and tripartite entanglement caused by squeezed drive in magnetic-cavity quantum electrodynamics system
Authors: Zhou Ying , Xie Shuang-Yuan , Xu Jing-Ping ,   Key Laboratory of Advanced Micro-Structured Materials, Ministry of Education, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China,   Department of Physics, Taizhou University, Taizhou 318000, China
Published: December 2020

Utilizing optical nonlinearity for generating the entanglement is still a most widely used approach due to its quality and simplicity. Here in this paper, we propose a theoretical scheme to generate bipartite and tripartite entanglement in a cavity quantum electrodynamics (QED) system with one Yttrium iron garnet (YIG) sphere by using a squeezed drive. In such a system, the parametric down-conversion process is used to generate the nonlinearity and further increase the coupling between cavity and YIG. Thus, the enhanced coupling between the microwave cavity photons and the ferromagnetic resonance (FMR) mode/magnetostatic (MS) mode results in bipartite entanglements. By using the mean field theory, we show that the bipartite entanglements strongly depend on the detuning of the cavity and magnon mode. When the driving field is tuned to be resonant with the FMR mode, but the MS mode is far off-resonant, the entanglement between photons and the FMR mode reaches its maximum. However, when the driving field is tuned to be resonant with the MS mode, but the FMR mode is detuned very well, the entanglement between photons and the MS mode reaches its maximum. We show that the dissipation of the FMR/MS mode affects the entanglement greatly, and the bipartite entanglement decreases as the dissipation rate of the FMR/MS mode increases. Under the steady-state approximation, we also show that the tripartite entanglement can be generated, and the minimum residual contangle increases with the enhancement of the nonlinear gain coefficient. With the nonlinearity induced by the parametric down conversion process, the interaction between the driving field and the magnetic-cavity QED system leads to the tripartite entanglement involving the cavity photons, FMR mode and the MS mode. Likewise, we show that the tripartite entanglement also strongly depends on the dissipation rate of MS mode, and the minimum residual contangle increases as the dissipation rate of the MS mode decreases. We also show that the squeezed field induced tripartite entanglement is insensitive to the temperature and has good robustness. Our results suggest that the magnetic-cavity QED system could provide a promising platform for studying the macroscopic quantum phenomena, and the squeezing field opens a new method of generating the entanglement.
Dual control of magnetism in LaMnO3/BaTiO3 superlattice by epitaxial strain and ferroelectric polarization
Authors: Chen Dong , Yu Ben-Hai ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000
Published: December 2020

The controlling of magnetism of perovskite oxides is scientifically interesting and technically important for numerous functionalities in spintronic devices and next-generation magnetic memories. The experimenally prepared superlattices often contain strain, polarization, oxygen vacancy and other factors, which can affect their magnetic properties. The magnetism of superlattice materials, controlled by using both epitaxial strain and ferroelectric polarization, is not only close to the real state of the material, but also can induce rich physical properties. In this work, we demonstrate a strong magnetoelectric coupling that appears in the LaMnO3/ BaTiO3 superlattice. First-principles calculations reveal that the reversible transitions among ferromagnetism, ferrimagnetism and anti-ferromagnetism are achieved by precisely controlling the magnitude and spin-direction of the magnetic moments of the Mn ions. A maximal change can be achieved to be 100.1% of the net magnetization by switching the ferroelectric polarization, which is much higher than the previous value 93.9%. The half-metallicity is demonstrated in the MnO2 layer, and accompanied by the spin polarization of the superlattice varying from 100% to 0. In addition, we realize the coexistence of ferroelectric polarization and metallicity, i.e. “ferroelectric metal”. Neither of the strong covalent Mn—O bond and La—O bond acts as an obstacle that prevents the ferroelectric polarization from penetrating the LMO layer. The Jahn-Teller effect, the tilt and rotation of oxygen octahedron, and the charge transfer of the superlattice are systemically analyzed. The variation of strain and re-orientation of polarization lead the electrons to transfer between the eg and t2g orbitals of Mn, which determines the magnetism of our system. Our purpose-designed LMO/BTO superlattice with robust intrinsic magnetoelectric coupling is a particularly interesting model system that can provide guidance for developing the spintronics for future applications.
Failure mechanism of lithium metal anode under practical conditions
Authors: Wang Xin-Meng , Shi Peng , Zhang Xue-Qiang , Chen Ai-Bing , Zhang Qiang ,   College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China,   Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Lithium (Li) metal is regarded as one of the most promising anodes in the next-generation high-energy-density rechargeable batteries due to its ultrahigh theoretical specific capacity and low reduction potential. Nevertheless, the unstable solid electrolyte interphase on the surface of Li metal anode and the nonuniform Li deposition seriously hinder its practical applications. Currently, mild conditions are employed in the researches of Li metal anode, which is of great significance for fundamentally understanding the physicochemical features of the anode interface and the mechanisms of Li deposition. However, practical conditions including ultrathin Li metal anode (< 50 μm), low negative/positive electrode areal capacity ratio (< 3.0), and lean electrolyte (< 3.0 g·Ah–1) are the premise to realize high energy density of Li metal batteries (> 350 W·h·kg–1). Herein, the gaps of Li metal anode under mild and practical conditions in terms of the cycling stability and surface morphology are compared and the reasons for the gaps are analyzed carefully. The total quantity of active Li metal decreases and the utilization depth of Li per cycle has been greatly improved under practical conditions. Therefore, the huge volume fluctuation and uneven Li deposition result in ceaseless destruction and regeneration of solid electrolyte interphase, and thus consuming the lean electrolyte and generating a large quantity of dead Li rapidly. Consequently, the polarization voltage of Li metal anode increases rapidly and the cycling stability of Li metal batteries deteriorates evidently under practical conditions. Moreover, the electrochemical reaction of Li metal anode is accelerated while fast charge/discharge process is employed, which further aggravates the stability of Li metal anode. This work reveals the challenges of Li metal anode under practical conditions and present the perspectives for the further researches in practical Li metal anode, which conduces to the solid development of high-energy-density Li metal batteries.