bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of linear chirp on the output characteristics of cross polarized wave with saturated power density
Authors: Qin Shuang  , Wang Zhao-Hua  , Wang Xian-Zhi  , He Hui-Jun  , Shen Zhong-Wei  , Wei Zhi-Yi  ,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;,   School of Instrument Science and Opto-Electronics Engineering, Beijing Information Science and Technology University, Beijing 100192, China
Published: December 2020

Ultra-short and ultra-intense laser is one of the hottest research spot of laser technology and strong field physics, due to its challenging and the frontier application research. As the key specification of ultrafast ultrahigh intensity laser pulse, the contrast ratio is very influential on the effect of laser-matter interaction. To perform the laser-matter interaction experiments at a high power level, the contrast is required to be as high as 1010 to prevent preplasma dynamics. To solve these problems, one has proposed many methods to improve the contrast of ultrafast laser, such as using the saturable absorbers, double chirped pulse amplification, plasma mirrors and the cross-polarized wave (XPW) generation. The XPW technology can not only enhance the contrast of the pulse by 3-4 orders of magnitude without introducing any space dispersion, but also extend the output spectrum to support shorter pulse duration. The XPW is a nonlinear filter technique in third-order nonlinear crystal with anisotropic susceptibility. Because of its simple and all-solid-state structure, the XPW technique has become one of the most effective methods to enhance the temporal pulse contrast and deliver shorter pulse duration in the field of high peak-power ultrafast lasers. This method has been used in many large laser facilities under construction or upgrades, such as the Apollon and ELI, the contrast ratio as high as 1010 has been achieved. It is known that the conversion efficiency and spectral characteristics of XPW have a strong dependence on the spatial and temporal magnitudes of the input driving pulse. In our experiment, it is found that the various changes of the driven pulse properties have different influences on the characteristics of XPW pulses. The relationship between the linear dispersion of driven pulse and temporal property of XPW is investigated theoretically. In addition, an experiment on verifying the theory is conducted by taking advantage of a programmable acousto-optic dispersion filter. The experimental results fit well to the theoretical results while some new phenomena emerge when the intensity in the BaF2 crystal reaches a saturation threshold. The spectral broadening capability of XPW becomes stronger and exceeds a theoretical upper limit. The pulse width can also be compressed to shorter than the theoretical limit. It is found that there are significant differences in spectral shape and conversion efficiency between the XPW signals by applying the opposite linear chirps to the driving pulse. A further analysis and theoretical explanation of these new phenomena are also presented.
Spin and charge Nernst effect in a four-terminal double quantum dot system
Authors: Zheng Jun  , Li Chun-Lei  , Yang Xi  , Guo Yong  ,   College of New Energy, Bohai University, Jinzhou 121013, China;,   College of Elementary Education, Capital Normal University, Beijing 100048, China;,   Department of Physics, Tsinghua University, Beijing 100084, China;,   Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
Published: December 2020

With the increase of integration scale, heat dissipation becomes one of the major problems in high density electronic devices and circuits. Controlling and reusing the heat energy in such miniaturized structures are essential topics for current and future technologies. With the development of microfabrication technology and low-temperature measurement technology in the last two decades, the thermoelectric measurement in low-dimensional sample has been feasible, and the thermal transport has received more and more attention. For the multi-terminal device, there is a novel thermoelectric phenomenon, called the spin Nernst effect, in which spin currents (or spin voltages) are generated perpendicularly to the temperature gradient. The spin Nernst effect has been confirmed experimentally, and has been theoretically studied in a variety of materials. In this paper, the spin and charge Nernst effect in a pair of vertically aligned quantum dots attached to four leads are studied in the Coulomb blockade regime based on the nonequilibrium Green's function technique. We focus on the influences of magnetic configuration and intra-dot (inter-dot) Coulomb interaction on the spin and charge Nernst effect. It is found that the signs and the magnitudes of spin and charge Nernst effect can be modulated by adjusting the magnetization directions of ferromagnetic electrodes. When the magnetic moments in the 1 and 3 electrodes are turned to antiparallel alignment, the pure spin Nernst (without charge Nernst) effect can occur by applying a transverse temperature gradient. Conversely, the spin and charge Nernst effect disappear if the magnetic moments of lead 1 and lead 3 are in the case of parallel configuration. Except for left and right thermal leads, we investigate the effect of the middle lead (lead 4) on the property of the Nernst effect. We find that when the normal metal lead 4 is transferred to ferromagnetic metal, the spin and charge Nernst effect both can be obtained simultaneously. In the end of the paper, we study the influences of intra-dot and inter-dot Coulomb interaction on the spin dependent Nernst coefficient. Through numerical calculations, we demonstrate that the magnitude of the Nernst effect is less dependent on the polarization strength of ferromagnetic electrodes, but can be remarkably enhanced by the Coulomb blockade. The spin Nernst coefficient is predicted to be more than two orders of magnitude larger than that of the case of zero Coulomb interaction. All the results indicate that the proposed four-terminal double quantum dot nano system is a promising candidate for spin caloritronic device.
Far-field analysis of third-order distributed feedback terahertz quantum cascade lasers
Authors: Zhu Yong-Hao  , Li Hua  , Wan Wen-Jian  , Zhou Tao  , Cao Jun-Cheng  ,   Key Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The single lobe far-field patterns produced from terahertz quantum cascade lasers (QCLs) are greatly demanded for various applications, such as imaging, data transmission, etc. However, for a ridge waveguide terahertz QCL, the far-field beam divergence is large due to the fact that the waveguide aperture is far smaller than the terahertz wavelength. This is the case typically for double-metal waveguide terahertz QCL which emits terahertz photons in almost every direction in the space. Even for a single plasmon waveguide terahertz QCL, the divergence angle is as large as 30 in both horizontal and vertical direction. Here, in this work we design and fabricate a double metal third-order distributed feedback terahertz QCL emitting around 4.3 THz, and investigate the characteristics of the longitudinal and transverse modes. This work aims to achieve high beam quality for terahertz QCL by exploiting the third-order distributed feedback geometry, and in the meantime to achieve single longitudinal mode operation. The electromagnetic field distribution in the waveguide is modelled by employing a finite element method. The mode selection mechanism is studied by using the eigen frequency analysis, and the far-field beam is simulated by applying the near-field to far-field Fourier transform technique. The QCL active region used in this work is based on the resonant-phonon design, which is grown by a molecular beam epitaxy (MBE) system on a semi-insulating GaAs (100) substrate. The wafer bonding and traditional semiconductor device fabrication technology, i.e., optical lithography, electron beam evaporation, lift-off, wet and dry etching, are used to process the MBE-growth wafer into the third-order distributed feedback geometry with double-metal waveguides. By carefully designing the grating structures and optimizing the fabrication process, we achieve third-order distributed feedback terahertz QCL with quasi-single-longitudinal mode operation and single lobe far-field beam pattern with low beam divergence in both vertical and horizontal directions. The effect of grating duty cycle on the far-field beam divergence is systematically studied theoretically and experimentally. By the simulation, we finally achieve the divergence angle of 1213 for a third-order distributed feedback laser with a grating duty cycle of 12% that results in an effective refractive index close to 3. The experimental results show good agreement with the simulation. There is still room to further reduce the beam divergence of third-order distributed feedback terahertz QCL by improve the accuracy of the simulation and the fabrication.
Design of an embedded tricolor-shifting device
Authors: Xu Ping  , Tang Shao-Tuo  , Yuan Xia  , Huang Hai-Xuan  , Yang Tuo  , Luo Tong-Zheng  , Yu Jun  ,   Institute of Micro-Nano Optoelectronic Technology, College of Electronic Science and Technology, Shenzhen University, Shenzhen 518060, China
Published: December 2020

Insufficient anti-counterfeiting performance and difficulties in manufacturing lead to performance degradation of the subwavelength rectangular structure grating, when it is applied to the field of optical anti-counterfeiting. To solve the problem, an embedded subwavelength one-dimensional simple periodic sinusoidal grating structure is proposed in this paper to replace the previous structure with a rectangular structure. By using equivalent medium theory, we find that the rectangular structure whose duty ration is 0.5 has the same effective refractive index as the sinusoidal structure. Then equivalent structure parameters of a sinusoidal structure are obtained based on a rectangular structure tricolor-shifting device, and the characteristics of the reflection peak are analyzed. The result shows that the sinusoidal structure gating can realize the same tricolor-shifting properties with a higher reflective efficiency as the rectangular structure gating. When the incidence angle of natural light is 45 for TE and TM polarization, the highest reflectivity values of 90%, 89% and 100% in blue, green and red bands can be obtained at the azimuths of 24, 63 and 90, respectively. Then the azimuth-induced color shifts of blue, green and red are realized. Physical mechanism of the equivalent rectangular structure to sinusoidal structure is explained in non-resonance and resonance conditions. Under the non-resonance condition, both of them can be regarded as a layer of completely equivalent optical film, possessing exactly the same optical properties. Under the resonance condition, they can be regarded as a slab waveguide. So when their effective refractive indexes, periods, film thicknesses and depths are equal, they have the same optical characteristic matrixes, supported guided modes, and resonant peak positions. In addition, we investigate the influences of the deviations of key parameters, including grating period, grating depth, coating film thickness, and incidence angle, and propose the rigorous redundancy of these parameters. When the values of period, depth, thickness, and incidence angle are kept within the ranges of 430-455 nm, 88-160 nm, 10-40 nm, and 40-50, respectively, the device can well keep the color-shifting effects of blue, green and red light. A model structure of the sinusoidal grating is fabricated by two-beam laser interference lithography experimentally. The tricolor-shifting device based on the sinusoidal structure presented in this paper can realize high diffraction efficiency azimuth-induced color shifts of blue, green and red light when natural light is incident, which breaks through the limit of bi-color shifting technology and lowers the difficulties in manufacturing, and may have great applications in the field of the optically variable image security.
Spatial resolution study of soft X-ray laser backlight shadow imaging technique
Authors: Wang Chen  , An Hong-Hai  , Fang Zhi-Heng  , Xiong Jun  , Wang Wei  , Sun Jin-Ren  ,   Shanghai Institute of Laser Plasma, Shanghai 201800, China
Published: December 2020

The soft X-ray laser shadow imaging technique is a good tool for diagnosing shadow profiles near the critical surface of high-temperature dense plasma. The short-pulse plasma X-ray laser, driven by high-power laser, is used as the backlight, which spreads freely approximately 500 mm far, passes through the plasma to be diagnosed, and changes its optical path by using a multi-layer spherical lens and multi-layer plane mirror, is attenuated by filters, and is recorded by a soft X-ray charge-coupled device (CCD). The plasma to be diagnosed can be driven by one or multiple laser beams, according to the needs of the physical research being conducted, and is imaged onto the CCD surface through a multilayer spherical lens. The shadow profile image of the plasma to be diagnosed at a particular time is obtained by using the instantaneous photographic mode of short-pulse soft X-ray laser backlight imaging. Compared with the traditional keV hard X-ray backlight technique, the soft X-ray laser shadow imaging technique has two distinct advantages. One is the appropriate wavelength of the probe light, which makes it possible to diagnose plasma near the critical surfac, and the other is a better spatial resolution because of the use of mature multilayer optical elements for near-normal incidence imaging. However, there has been no systematic study on the extent to which the spatial resolution of the imaging technology can be achieved. In this study, a careful analysis is carried out considering three aspects:the optical path geometry, the diffraction limit, and the imaging aberration. The results show that a spatial resolution of approximately 2 m can be achieved. An experiment is carried out to measure the Rayleigh-Taylor instability of plasma from the lateral direction, by using the soft X-ray laser shadow imaging technique. Some microfluids with a width of several microns can be clearly distinguished in the experimental shadow image, indicating that the diagnostic technique has a good spatial resolution. Further analysis reveals that the main factor that limits the spatial resolution is the optical path geometry. It is possible to achieve a spatial resolution of up to 1 m by increasing the magnification, selecting CCDs with smaller receiving units, etc.
Point spread function of incoherent digital holography based on spiral phase modulation
Authors: Zhao Zhong-Chao  , Yang Xu-Feng  , Xu Tian-Xu  , He Jiu-Ru  , Gong Qiao-Xiao  , Du Yan-Li  , Dong Lin  , Yuan Bin  , Ma Feng-Ying  ,   School of Physical Engineering, Zhengzhou University, Zhengzhou 450001, China
Published: December 2020

Fresnel incoherent correlation holography (FINCH) has attracted much attention because it is able to record the holograms of three-dimensional (3D) samples under incoherent illumination with just a charge coupled device (CCD) and spatial light modulator (SLM). The FINCH technology achieves the splitting and phase shifting of the incident beam by loading a phase mask on an SLM. Three holograms, whose phase factors are different from each other, are recorded sequentially by a CCD. After the three holograms are superposed in the computer, the zero order image and a twin image are eliminated, and a complex hologram is obtained. The 3D properties of the object are revealed when the complex hologram is reconstructed in the computer. Spiral phase filters (SPFs) are commonly used to produce optical vortices, which can enhance and recognize image edges. In this paper, the spiral phase modulated FINCH system illuminated by Xenon lamp is built, in which the phase-only SLM is space-division multiplexed by a helical lens (superposed by an SPF and a lens) and a conventional lens. The mathematical model of spiral phase modulated FINCH system is established based on wave optics theory. The specific forms of the point spread function (PSF) and the reconstruction distance of the system are given for the first time. Experiments are conducted by using a small aperture with a diameter of 20 nm as a point source, the point source hologram recorded by CCD and the reconstructed image are consistent with the simulated ones. When the system is used for imaging resolution target and unstained onion cells, the edge contrast enhancement effects are obtained without the loss of resolution. The results show that the spiral phase modulated FINCH system can not only improve the edge contrast of the amplitude object, but also extract the edge information or recognition of the phase objects. This method has an important application prospect in the quantitative imaging of phase objects such as in real-time monitoring cell division and deformation of living cells.
Enhanced selfintegration algorithm for fiber torsion sensor based acoustically-induced fiber grating
Authors: Liu Yu  , Ren Guo-Bin  , Jin Wen-Xing  , Wu Yue  , Yang Yu-Guang  , Jian Shui-Sheng  ,   Key Laboratory of All Optical Network and Advanced Telecommunication Network of the Ministry of Education, Beijing Jiaotong University, Beijing 100044, China;,   Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

Mechanical parameter monitoring based on optical mode detection benefits from its low cross sensitivity and inexpensive instrument. The key to improving detection accuracy is to generate high-quality detection light and use efficient algorithms. We present a strain-independent torsion sensor based on acoustically-induced fiber grating (AIFG) in the dual-mode fiber (DMF) and use the enhanced self-integration algorithm to improve the sensing accuracy. By tuning the radio frequency of driving signal, the LP11 mode generated by the AIFG can be exploited to measure the dynamic torsion variations. Without the complex device such as fiber interferometers and photonic crystal fibers (PCFs), the simple structure built by mode converter and charge coupled device (CCD) can track the dynamic variations and has less cross sensitivity of strain along the transmission direction. The AIFG driven by a radio frequency as a mode converter at specific wavelength does not participate in sensing but generates the high-purity LP11 mode that accounts for more than 90% of total power. With the twist from the rotator stage, the DMF keeps rotating and CCD records the spatial distribution of mode profiles. The features of optical mode is enhanced based on matrix analysis and then the relationship between twist angle and mode features is obtained. Based on image processing, the dynamic variation of spatial beam detected by CCD can be easily tracked and quantified. In experiment, the rotation angle can be obtained by calculating the feature value of the optical mode. Our image detection algorithm is specially designed for the optical fiber mode. Compared with traditional image recognition based on feature learning, it is simple and fast because it is needless to use image segmentation and stochastic processing. Through a series of experiments on angle rotation and parallel strain, we verify the correctness of the enhanced self-integration model and analyse the computational uncertainties that influence the stability of experiment. In the 0 to 180 measurement range, the maximum range of measurement error is less than 11%. When the axial strain is between 100 and 1500 , the sensor is strain-independent. Thus, it is verified that the torsion sensor based on AIFG has high sensitivity and can overcome the cross sensitivity of strain along a certain direction. The pertinent results have significant guidance in designing the multi-parameter sensor. The optical mode detection, instead of the traditional spectrum measurement, enables the whole structure to have the potential to be rebuilt by inexpensive devices that work in visible wavelengths.
Coupled oscillation and shape instability of bubbles in acoustic field
Authors: Ma Yan  , Lin Shu-Yu  , Xu Jie  ,   Shaanxi Key Laboratory of Ultrasonics, Shaanxi Normal University, Xi'an 710062, China;,   Engineering Research Center of Nanostructure and Functional Materials, College of Physics and Electronic Information Engineering, Ningxia Normal University, Guyuan 756000, China
Published: December 2020

Based on the Lagrange's equation, the dynamic equations and shape mode equations of two bubbles with nonspherical distortion are obtained. The radial oscillations and shape instabilities of two bubbles with nonspherical distortion in an acoustic field are numerically investigated. The numerical results show that there are two coupled modes between two nonspherical bubbles: shape coupled mode and radial coupled mode. The coupled modes between two nonspherical bubbles depend on the shape modes of two bubbles. When the shape mode of the first bubble is equal to that of the second bubble (n=m), the shape coupled mode and radial coupled mode both exist. The interaction force between bubbles is caused by these two coupled modes. If the two bubbles have different shape mode orders (n m), there is a radially coupled mode between two bubbles. The interaction force between two bubbles is caused by radially coupled mode. The interaction caused by the radial coupling and shape coupling has an influence on the instability of gas bubble. The influencing factors depend on the shape mode, the equilibrium radius of neighboring bubble, and the driving acoustic field. The results demonstrate that the shape coupling can change the severity of the collapse of a gas bubble, and increase the ability of a gas bubble to resist distortion under a certain condition. The nonspherical disturbance of a real bubble in an acoustic field is not a single shape mode, but the coupling of different shape modes, so the shape coupling has an obvious influence on the shape instability of a real bubble. These may be the reason why bubbles can form some stable structures and keep stable oscillations in an acoustic field.
Early time effects produced by neutral gas ionospheric chemical release
Authors: Zhao Hai-Sheng  , Xu Zhao-Hui  , Gao Jing-Fan  , Xu Zheng-Wen  , Wu Jian  , Feng Jie  , Xu Bin  , Xue Kun  , Li Hui  , Ma Zheng-Zheng  ,   National Key Laboratory of Electromagnetic Environment, China Research Institute of Radiowave Propagation, Qingdao 266107, China;,   School of Physics Optoelectronic Engineering, Xidian University, Xi'an 710071, China
Published: December 2020

The artificial release of electron adsorbing material can cause electron density to be depleted in the ionosphere, forming the ionospheric holes rapidly. At the same time, the shell structure of the electron density enhancement around the hole is produced, owing to the extrusion of background plasma caused by rapid expansion of the release. The coexistence of ionospheric hole and enhancement structure is the significant characteristics of the early time effects. In this paper, the early time effects of neutral chemicals released into ionosphere are studied, and a physical model of spatiotemporal evolution about early time electron density is set up. At t=1 s, the maximum electron density in the enhanced region is 2.46106 cm-3, approximately 2.8 times as great as background electron density, then the electron density at the boundary gradually decreases. At t=30 s, the maximum electron density is 1.58106 cm-3, which is about 1.7 times the background electron density. At t=120 s the maximum electron density in the enhanced region is 1.12106 cm-3, which is 1.2 times the background electron density. Within 120 s after release, the size of the ionospheric cavity increases gradually; at t=5 s the distribution range of the released chemical material is of a sphere of about 10 km in diameter; at t=120 s the distribution diameter of the released chemical material is more than 70 km, and at the same time, the depletion depth of the ionospheric hole decreases slowly. At t=1 s, the depletion depth of the ionospheric hole is about 100%, and at t=120 s the depletion depth of the ionospheric cavity decreases to 95%. The effects of different-frequency radio waves propagating through ionospheric disturbance at t=10 s and t=120 s are simulated by the ray tracing. At t=10 s, the effect of electron density enhancement is remarkable, and the thickness of the enhancement is about 10 km, and the electronic density enhancement area can reflect the radio wave signal at a frequency as high as 14 MHz. At t=120 s, the phenomenon of electron density enhancement becomes weak, the thickness of the enhanced area continues to increase, and the radio wave signal that the electronic density enhancement area could reflect decreases to 11 MHz. The radio waves at a frequency range between 9 MHz and 12 MHz each have a complex diffraction, focusing and dispersing effect in the disturbed area. Furthermore, according to the working principle of ionospheric vertical measurement instrument and ray tracing theory, the vertical ionization detection figures are obtained through inversion. The results are consistent with previous experimental results of rocket exhaust, which testifies the correctness of proposed model.
Modulation instabilities in equilateral three-core optical fibers for isosceles-triangle symmetric continuous waves
Authors: Pei Shi-Xin  , Xu Hui  , Sun Ting-Ting  , Li Jin-Hua  ,   School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Jiangsu Key Laboratory for Optoelectronic Detection of Atmosphere and Ocean, Nanjing 210044, China
Published: December 2020

Modulation instability (MI) of the isosceles-triangle symmetric continuous wave in equilateral three-core fibers (ETCFs) is studied in detail. The so-called isosceles-triangle symmetric continuous wave state is the planar wave where the fields in its two cores are identical but different from the field in the third core, and the premise of its existence is that the total power (P) exceeds a minimum value (Pmin) that depends on the linear coupling coefficient and nonlinear coefficient of ETCFs. For a given total power P (P ≥ qslant Pmin), set the power in one core to be P1, and the powers in the other two cores to be P2 (P=P1 + 2P2), then two kinds of filed distributions will be found. The first kind is for P1 > P2 with P1 becoming more and more large as total power P increases. By the linear stability analysis method, the main characteristics of MI in ETCFs are found which are quite similar to those of the asymmetric continuous wave states in two core optical fibers (TCFs). The other kind is that P1 becomes more and more small and P2 becomes more and more large as total power P increases. Through the same method, the main characteristics of MI in ETCFs are found which are distinctively different from those of the asymmetric continuous wave states in TCFs. On the one hand, MI can be generated in both normal and anomalous dispersion regimes without perturbations. In addition, the zero-perturbation frequency corresponds to the largest gain of MI in the normal dispersion regime. On the other hand, the coupling coefficient dispersion, which can dramatically modify the spectra of MI in TCFs, plays a minor role in both normal and anomalous dispersion regimes in ETCFs. In practical application, the findings in this paper are of guiding significance for studying the nonlinear effects of mode-division multiplexing system based on the multimode or multicore optical fibers.
Numerical study on conical two-dimensional photonic crystal in silicon thin-film solar cells
Authors: Chen Pei-Zhuan  , Yu Li-Yuan  , Niu Ping-Juan  , Fu Xian-Song  , Yang Guang-Hua  , Zhang Jian-Jun  , Hou Guo-Fu  ,   Engineering Research Center of High Power Solid State Lighting Application System, Ministry of Education, School of Electrical Engineering and Automation, Tianjin Polytechnic University, Tianjin 300387, China;,   Tianjin Key Laboratory of Photoelectronic Thin-Film Devices and Technique, Key Laboratory of Optical Information Science & Technology, Ministry of Education, Institute of Photoelectronic Thin-Film Devices and Technique, Nankai University, Tianjin 300071, China
Published: December 2020

To further improve the absorption of thin-film silicon solar cells (TFSSCs), it is essential to understand what kind of texture morphology could present the best light trapping effect, or rather, which structural parameter plays the most important role, and offers the required lateral feature size, height or others. In this paper, the influences of structural parameters of conical two-dimensional photonic crystal (2D PC) on each-layer absorption of the microcrystalline silicon thin film solar cells are numerically studied by using the finite-difference time-domain method when 2D PC is introduced into the intrinsic layer. The results show that both the intrinsic absorption and parasitic absorption are significantly enhanced via introduction of 2D PC into the intrinsic layer. The parasitic absorption is mainly caused by the ITO layer, and the intrinsic absorption shows a sinusoidal fluctuation with the increase of period. It is found that the aspect ratio (height/period) of the 2D PC has a decisive influence on the cell intrinsic absorption. When the period of the 2D PC is less than 1m, the intrinsic absorption first increases and then decreases with the increase of the aspect ratio, and reaches a maximum value with an aspect ratio of 1. For the case of period larger than 1m, the aspect ratio needed to obtain the maximum result is smaller than 1. What is more, the larger the period, the smaller the aspect ratio for maximizing the intrinsic absorption will be. The peak intrinsic absorption can be obtained when a 2D PC with a period of 0.5m and an aspect ratio of 1 is introduced. Compared with that of the flat cell, the short-circuited current density of the above optimized 2D PC cell can be significantly enhanced by 5.8 mA/cm2(from 21.9 to 27.8 mA/cm2), corresponding to a relative enhancement of 27%. In order to improve antireflection performance, it is critical to adopt a textured front-surface morphology where the aspect ratio is higher than 1/2. In addition, the intrinsic absorption increases with the increasing fill factor, and reaches a maximum value when the fill factor of the 2D PC is close to 0.9. The research results of this paper break through the traditional viewpoint of light trapping mechanism which points out that the light trapping effect is mainly dependent on the lateral feature size of the texture, and provide an important guide for obtaining optimized random or periodic texture via experiment.
Simulation analyses of 100-keV as well as low and high energy protons through insulating nanocapillary
Authors: Zhu Bing-Hui  , Yang Ai-Xiang  , Niu Shu-Tong  , Chen Xi-Meng  , Zhou Wang Shao  , Jian-Xiong  ,   School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China;,   The Longrui Technology Company Limited, China National Nuclear Corporation, Jiayuguan 735100, China
Published: December 2020

In order to clearly understand the physical images of incident ions passing through the insulating nanocapillary, in this work we establish a theoretical model, in which the matlab program is combined with the Monte Carlo method, to estimate the time evolution of transmission features, such as the angular and deposited charge distribution, three-dimensional (3D) trajectories of H+ particles with proton incident energies of 10 keV, 100 keV and 1 MeV at -1 title angle. The simulation results show that the transmission mechanism of 100 keV protons is different from those of 10 keV and 1 MeV protons. After a sufficiently charging and discharging stage, 10 keV H+ particles are guided along the direction of capillary axis, indicating that the guiding force from the surface charge patches is significant, and the small-angle scattering of 1 MeV protons under the capillary inner wall is a physical process that determines the transport of H+ particles through the nanocapillary. However, for 100 keV H+ particles, the centroid angle gradually shifts from the guiding direction to the direction close to the incident beam, which is attributed to the fact that the stochastic inelastic binary collision below the surface is the main transmission mechanism at the beginning. After the charging and discharging reach an equilibrium state, the H+ particles are likely to pass through the nanocapillary, and the main transmission mechanism is the charge-patch-assisted specular scattering. This mechanism deepens the understanding of the transport behavior of protons through the nanocapillary, which will contribute to the control and application of the 100 keV proton beam.
Theoretical study of coupling double-bubbles ultrasonic cavitation characteristics
Authors: Wang De-Xin  , Naranmandula  ,   College of Physics and Electronics, Inner Mongolia University for Nationalities, Tongliao 028043, China
Published: December 2020

When the distances between bubbles are small enough, the pressure acting on the bubble is not the same as the external driving pressure, because of the radiation pressure wave of the neighboring bubbles. The force between two bubbles due to the bubble-radiated pressure waves by the neighboring bubbles is called the secondary Bjerknes force. Considering the bubble-radiated pressure waves and using the modified Keller-Miksis equation and van der Waals equation, the changes of the radius, the secondary Bjerknes force and the temperature of the double bubbles, which have different sizes, interspaces in between, and noble gases, in the process of ultrasonic cavitation are calculated. The calculations are based on the assumption that the locations of double bubbles stay unchanged in the oscillation process and their shapes always keep spherical. The double bubbles can also oscillate synchronously under the influence of the driving ultrasonic field. Because the sound propagation speed in water extremely fast, the time-delay effect on the secondary Bjerknes force is neglected. From the calculated results, the following conclusions can be drawn: when the sizes of double bubbles are different, the smaller bubble is more restrained and the temperature change is larger. When the sizes of double bubbles are the same, the Bjerknes force is negative, indicating that the coupled double bubbles are attracted to each other during the oscillation and the Bjerknes force has two radial oscillations in one driving period. As the interspace between double bubbles increases from 100 m to 1 cm, the secondary Bjerknes force decreases from 10-4 N to 10-8 N, indicating that the interaction between double bubbles increases with the decreasing of the distance between the bubbles. The coupling double bubbles with different noble gases have only a small difference in maximum radius in the stage of expansion, but have different oscillation patterns clearly in the stage of rebound. This is because the bubble expansion process can be seen as an isothermal process, the effective polytropic exponent is approximately equal to 1. The collapse process can be regarded as an adiabatic process, so the effective polytropic exponent of noble gas with large molecules changes rapidly, and the influence of the oscillation of the bubbles becomes large. Our work provides a theoretical basis for establishing the acoustic cavitation model of different-number bubbles, and calculating the interaction force between different-number bubbles.
Construction of Breit quark potential in coordinate space and mass splits of meson and quarkonium
Authors: Jirimutu  , Aodeng  , Xue Kang  ,   College of Computer and Information, Inner Mongolia Medical University, Hohehot 010110, China
Published: December 2020

Construction of a valid interaction potential function between quarks is a crucial issue in hadronic physics and also one of the frontier issues. Non-relativistic Breit potential is a common model to describe the interaction between quarks. It is used to successfully calculate the bound states of quarks and quark scatterings. These spur people to improve it. As is well known, the full Breit potential function, which includes the color-Coulomb term, the mass term, the orbit-orbit interaction term, the spin-spin interaction term, the spin-orbit interaction term, the tensor force term, and the constant term, contains singularity factors. How to eliminate the singularity factors is the most urgent task for developing Breit potential model. In this paper, we carry out a replacement method to eliminate the singularity factors in the full Breit quark potential function in coordinate space. Except for the color-Coulomb term and the constant term, remaining terms in the Breit quark potential function are all reconstructed. The replacement of (r) 3 e-r/8 is applied to the mass term and the spin-spin interaction term. The replacement of 1/r (1-e-r)/r is applied to the obit-obit interaction term. The replacement of 1/r3[1-(1+r)e-r]/r3 is applied to the spin-obit interaction term and the tensor force term. We calculate mass splits of heavy mesons and quarkonium species by using the reconstructed potential function and test the validity of the reconstructed potential function. The screening mass used in the calculations is not a simple constant but a variable relating to the quark mass mi and mj. It is found that the simple screening-mass expression cannot give the accurate value of B-meson mass, although it may give the mass splits of light mesons. However, the calculated results of the mass splits of the light mesons -, the heavy mesons, c-J/, b-(1s), c0-c2, etc., are highly consistent with the experimental data only when the screening mass is taken to be the Laurent series, =c-3(a+0.512)-3+ c-2(a+0.512)2 +c-1(a+0.512)-1+c0+c1(a+0.512) with respect to the average quark mass a=(mi+mj)/2. In this case, the mass accuracy of other mesons, especially the six D mesons, is improved significantly. Our calculated results indicate that a valid quark potential model, which gives not only the mass values of light mesons accurately but also the mass splits of heavy quarkonium species, is thus constructed in this paper.
Path-entanglement microwave signals detecting method based on entanglement witness
Authors: Zhu Hao-Nan  , Wu De-Wei  , Li Xiang  , Wang Xiang-Lin  , Miao Qiang  , Fang Guan  ,   Information and Navigation College, Air Force Engineering University, Xi'an 710077, China
Published: December 2020

In recent years, the great progress of studying the quantum entanglement has been made. In the field of optics, the great success has been achieved in quantum entanglement theory and technology. Then researchers concentrate on the microwave frequency band whose frequency is lower than that of optical frequency band. The signal in the microwave frequency band has a longer wavelength, and it has the diffraction capability that the optical signal does not possess. Furthermore, it can spread further in complex environments. Now it is possible to experimentally produce squeezed state of microwave signals and spatially separated path-entangled microwave signals. It is an important issue to judge whether the microwave signals received through dual paths are in entanglement state. In this paper, we firstly introduce the method of using squeezed state of microwave and microwave beam splitter to prepare path-entangled microwave signals. Then we use entanglement witness method to detect entanglement. Through constructing the entanglement witness operator in path-entangled microwave signals, the entanglement of path-entangled microwave signals can be effectively detected. We decompose the expression of the continuous variables path-entangled microwave signals into a large number of 2 2 entangled superposition states, deduce an entangled witness operator of path-entangled microwave signals based on the principle of partial transpose criterion and entanglement witnessing, and prove that the entangled witness can be used to detect the path-entangled microwave signals. Finally, we propose a physical verification of path-entangled microwave signal entanglement. The verification can be realized as follows:firstly, we reverse the phase of a received quantum-state microwave signal by utilizing continuous variable controlled phase gate in a range of 0-, then we send two microwave signals into the two input ports of the microwave beam splitter, and we operate coincidence counting of microwave photons on the two output ports after entanglement microwave signals have passed through the microwave splitter. By analyzing the results of the whole process, we have the following conclusions:if the coincidence rate of two input signals is higher than that of non-entangled microwave signals under the same power, signals can be counted as entanglement. The proposed method can detect the entangled microwave signals more efficiently than the conventional methods, such as quantum state reconstruction, and thus reduce the detection and computational complexity. The entanglement of the two microwave quantum state signals can be observed directly by using this method. This paper provides a new idea for detecting the path-entangled microwave signals.
Magnetoelectric effect analysis of magnetostrictive/piezoelectric laminated composites
Authors: Zhou Yong  , Li Chun-Jian  , Pan Yu-Rong  ,   Nanjing University of Information Science and Technology, Nanjing 210044, China;,   Jiangsu Technology Engineering Center of Meteorological Sensor Network, Nanjing 210044, China
Published: December 2020

Based on the finite element analysis software COMSOL5.0,a three-dimensional (3D) model of cantilever beam composed of magnetostrictive/piezoelectric/magnetostrictive laminated composites is established using the piezoelectric module and magnetic field module.The magneto electro coupling coefficient αME of the composite is analyzed.The effect of geometrical parameter on magnetoelectric coefficient is studied,and the geometrical parameters are optimized. Firstly,the stress,strain,displacement and potential distributions of the magnetoelectric layered structure are analyzed by the steady-state solver.The stress and strain concentrate on the fixed terminal while the maximum displacement exists in the free end of the structure.As a result,the potential appears between the upper and lower surface of the piezoelectric layer and the voltage distribution is not uniform.The output voltage in the fixed terminal is larger than that in the free end,which is about 49 V compared with 42 V in the free end.And the dynamic distributions of various variables in magnetoelectric composite structure are analyzed by transient solution.Secondly,the resonance frequency of the structure and the influence of the bias magnetic field on the output voltage are studied by small signal analysis in frequency domain.The results show that the output voltage decreases with the increase of Hdc.Also,the maximum output voltage is about 3.36 V at the second-order resonance frequency,which is far higher than the voltage at the first-order resonant frequency in the condition of bias magnetic fields Hdc=200 Oe and alternating magnetic fields Hac=1 Oe.The reason is that the composite structure has a larger deformation at the second-order resonance frequency.Furthermore,the effect of thickness ratio between magnetostrictive and piezoelectric layers tm/tp on coupling coefficient is analyzed by changing the thickness of magnetostrictive layer and piezoelectric layer,respectively.The results show that the magnetoelectric coefficient increases with the augment of the thickness ratio,but the increasing rate decreases gradually.The research also shows that it has a greater influence on magnetoelectric coefficient to change tp rather than tm.Finally,the variations of magnetoelectric coefficient with the area of composite structure and the aspect ratio are analyzed.The results show that the magnetoelectric coefficient increases gradually with the augment of magnetoelectric composite area,but the increasing rate declines gradually.With the constant composite area,the magnetoelectric coefficient first increases and then drops with the increase of aspect ratio L/W,demonstrating the existence of an optimized value.Besides,the width W acts more importantly than length L because strain concentrates on the fixed terminal along
Dynamic analysis and finite time synchronization of a fractional-order chaotic system with hidden attractors
Authors: Zheng Guang-Chao  , Liu Chong-Xin  , Wang Yan  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Shilnikov criteria believe that the emergence of chaos requires at least one unstable equilibrium, and an attractor is associated with the unstable equilibrium. However, some special chaotic systems have been proposed recently, each of which has one stable equilibrium, or no equilibrium at all, or has a linear equilibrium (infinite equilibrium). These special dynamical systems can present chaotic characteristics, and the attractors in these chaotic systems are called hidden attractors due to the fact that the attraction basins of chaotic systems do not intersect with small neighborhoods of any equilibrium points. Since they were first found and reported in 2011, the dynamical systems with hidden attractors have attracted much attention. Additionally, the fractional-order system, which can give a clearer physical meaning and a more accurate description of the physical phenomenon, has been broadly investigated in recent years. Motivated by these two considerations, in this paper, we propose a fractional-order chaotic system with hidden attractors, and the finite time synchronization of the fractional-order chaotic systems is also studied.Most of the researches mainly focus on dynamic analysis and control of integer-order chaotic systems with hidden attractors. In this paper, based on the Sprott E system, a fractional-order chaotic system is constructed by adding an appropriate constant term. The fractional-order chaotic system has only one stable equilibrium point, but it can generate various hidden attractors. Basic dynamical characteristics of the system are analyzed carefully through phase diagram, Poincare mapping and power spectrum, and the results show that the fractional-order system can present obvious chaotic characteristics. Based on bifurcation diagram of system order, it can be found that the fractional-order system can have period attractors, doubling period attractors, and chaotic attractors with various orders. Additionally, a finite time synchronization of the fractional-order chaotic system with hidden attractors is realized based on the finite time stable theorem, and the proposed controller is robust and can guarantee fast convergence. Finally, numerical simulation is carried out and the results verify the effectiveness of the proposed controller.The fractional-order chaotic system with hidden attractors has more complex and richer dynamic characteristics than integer-order chaotic systems, and chaotic range of parameters is more flexible, meanwhile the dynamics is more sensitive to system parameters. Therefore, the fractional-order chaotic system with hidden attractors can provide more key parameters and present better performance for practical applications, such as secure communication and image encryption, and it deserves to be further investigated.