查看更多>>摘要：With the rapid development of information and communication technology,a key objective in the field of optoelec-tronic integrated devices is to reduce the nano-laser size and energy consumption.Photonics nanolasers are unable to exceed the diffraction limit and typically exhibit low modulation rates of several GHz.In contrast,plasmonic nanolaser utilizes highly confined surface plasmon polariton(SPP)mode that can exceed diffraction limit and their strong Purcell effect can accelerate the modulation rates to several THz.Herein,we propose a parametrically tunable artificial plasmonic nanolasers based on metal-insulator-semiconductor-insulator-metal(MISIM)structure,which demonstrates its ability to compress the mode field volume to λ/14.As the pump power increases,the proposed artificial plasmonic nanolaser ex-hibits 20-nm-wide output spectrum.Additionally,we investigate the effects of various cavity parameters on the nanolaser's output threshold,offering potentials for realizing low-threshold artificial plasmonic nanolasers.Moreover,we observe a blue shift in the center wavelength of the nanolaser output with thinner gain layer thickness,predominantly attributed to the increased exciton-photon coupling strength.Our work brings inspiration to several areas,including spaser-based in-terconnects,nano-LEDs,spontaneous emission control,miniaturization of photon condensates,eigenmode engineering of plasmonic nanolasers,and optimal design driven by artificial intelligence(AI).
查看更多>>摘要：Natural creatures and ancient cultures are full of potential sources to provide inspiration for applied sciences.Inspired by the fractal geometry in nature and the fretwork frame in ancient culture,here we design the acoustic metasurface to realize sound anomalous modulation,which manifests itself as an incident-dependent propagation behavior:sound wave propagating in the forward direction is allowed to transmit with high efficiency while in the backward direction is obviously suppressed.We quantitatively investigate the dependences of asymmetric transmission on the propagation direction,incident angle and operating frequency by calculating sound transmittance and energy contrast.This compact fractal fretwork metasurface for acoustic anomalous modulation would promote the development of integrated acoustic devices and expand versatile applications in acoustic communication and information encryption.
查看更多>>摘要：This study numerically investigates the nonlinear interaction of head-on solitary waves in a granular chain(a noninte-grable system)and compares the simulation results with the theoretical results in fluid(an integrable system).Three stages(the pre-in-phase traveling stage,the central-collision stage,and the post-in-phase traveling stage)are identified to describe the nonlinear interaction processes in the granular chain.The nonlinear scattering effect occurs in the central-collision stage,which decreases the amplitude of the incident solitary waves.Compared with the leading-time phase in the incident and separation collision processes,the lagging-time phase in the separation collision process is smaller.This asymmet-rical nonlinear collision results in an occurrence of leading phase shifts of time and space in the post-in-phase traveling stage.We next find that the solitary wave amplitude does not influence the immediate space-phase shift in the granular chain.The space-phase shift of the post-in-phase traveling stage is only determined by the measurement position rather than the wave amplitude.The results are reversed in the fluid.An increase in solitary wave amplitude leads to decreased attachment,detachment,and residence times for granular chains and fluid.For the immediate time-phase shift,leading and lagging phenomena appear in the granular chain and the fluid,respectively.These results offer new knowledge for designing mechanical metamaterials and energy-mitigating systems.
查看更多>>摘要："Magnetic window"is considered as an effective method to solve the communication blackout issue.COMSOL soft-ware package based on the finite element method is utilized to simulate the propagation of right-handed circularly polarized wave in the magnetized plasma sheath.We assume a double Gaussian model of electron density and an exponential at-tenuation model of magnetic field.The propagation characteristics of right-handed circularly polarized wave are analyzed by the observation of the reflected,transmitted and loss coefficient.The numerical results show that the propagation of right-handed circularly polarized wave in the magnetized plasma sheath varies for different incident angles,collision fre-quencies,non-uniform magnetic fields and non-uniform plasma densities.We notice that reducing the wave frequency can meet the propagation conditions of whistle mode in the weak magnetized plasma sheath.And the transmittance of whistle mode is less affected by the variation of the electron density and the collision frequency.It can be used as a communication window.
查看更多>>摘要：Through theoretical analysis,we construct a physical model that includes the influence of counter-external driven current opposite to the plasma current direction in the neoclassical tearing mode(NTM).The equation is used with this model to obtain the modified Rutherford equation with co-current and counter-current contributions.Consistent with the reported experimental results,numerical simulations have shown that the localized counter external current can only par-tially suppress NTM when it is far from the resonant magnetic surface.Under some circumstances,the Ohkawa mechanism dominated current drive(OKCD)by electron cyclotron waves can concurrently create both co-current and counter-current.In this instance,the minimal electron cyclotron wave power that suppresses a particular NTM was calculated by the Ruther-ford equation.The result is marginally less than when taking co-current alone into consideration.As a result,to suppress NTM using OKCD,one only needs to align the co-current with a greater OKCD peak well with the resonant magnetic surface.The effect of its lower counter-current does not need to be considered because the location of the counter-current deviates greatly from the resonant magnetic surface.
查看更多>>摘要：Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial strength distribution of magnetic fields can be accurately predicted by calculating the net flow caused by the superposition of source flow and return flow of hot electrons.The theoretical model established shows good agreement with the simulation results,indicating that the magnetic-field strength scales positively to the temperature of hot electrons.This provides us a way to improve the magnetic-field generation by using a micro-structured plasma grating in front of the solid target.Compared with that for a common flat target,hot electrons can be effectively heated with the well-designed grating size,leading to a stronger magnetic field.The spatial distribution of magnetic fields can be modulated by optimizing the grating period and height as well as the incident angle of the laser pulse.
查看更多>>摘要：A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m-3)to collision frequency(unit:Hz)exceeds 1 × 1011,enabling an electron density to exceed 1 × 1020 m-3 and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.
查看更多>>摘要：Dual-phase and three-phase grating x-ray interference is a promising new technique for grating-based x-ray differen-tial phase contrast imaging.Dual-phase grating interferometers have been relatively completely studied and discussed.In this paper,the corresponding imaging fringe formula of the three-phase grating interferometer is provided.At the same time,the similarities and differences between the three-phase grating interferometer and the dual-phase grating interferom-eter are investigated and verified,and that the three-phase grating interferometer can produce large-period moiré fringes without using the analyzing grating is demonstrated experimentally.Finally,a simple method of designing three-phase grat-ing and multi-grating imaging systems from geometric optics based on the thin-lens theory of gratings is presented.These theoretical formulas and experimental results provide optimization tools for designing three-phase grating interferometer systems.
查看更多>>摘要：The high-pressure structure and elastic properties of calcium azide(Ca(N3)2)were investigated using in-situ high-pressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa,respectively.The compressibility of Ca(N3)2 changed as the pressure increased,and no phase transition occurred within the pressure from ambient pressure up to 54 GPa.The measured zero-pressure bulk modulus of Ca(N3)2 is higher than that of other alkali metal azides,due to differences in the ionic character of their metal-azide bonds.Using CASTEP,all vibration modes of Ca(N3)2 were accurately identified in the vibrational spectrum at ambient pressure.In the high-pressure vibration study,several external modes(ext.)and internal bending modes(v2)of azide anions(N3-)softened up to～7 GPa and then hardened beyond that pressure.This evidence is consistent with the variation observed in the FE-fE data analyzed from the XRD result,where the slope of the curve changes at 7.1 GPa.The main behaviors under pressure are the alternating compression,rotation,and bending of N3-ions.The bending behavior makes the structure of Ca(N3)2 more stable under pressure.
查看更多>>摘要：One hallmark of glasses is the existence of excess vibrational modes at low frequencies ω beyond Debye's prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency depen-dence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow Dexc(ω)～ω2 in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that inter-action potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interac-tion to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.
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