查看更多>>摘要：Turbulence in complex environments such as the atmosphere and biological media has always been a great challenge to the application of beam propagation in optical communication,optical trapping and manipulation.To overcome this challenge,this study comprehensively investigates the robust propagation of traditional Gaussian and autofocusing beams in turbulent environments.In order to select stable beams that exhibit high intensity and high field gradient at the focal posi-tion in complex environments,Kolmogorov turbulence theory is used to simulate the propagation of beams in atmospheric turbulence based on the multi-phase screen method.We systematically analyze the intensity fluctuations,the variation of the coherence factor and the change in the scintillation index with propagation distance.The analysis reveals that the intensity fluctuations of autofocusing beams are significantly smaller than those of Gaussian beams,and the coherence of autofocusing beams is better than that of Gaussian beams under turbulence.Moreover,autofocusing beams exhibit less os-cillation than Gaussian beams,indicating that autofocusing beams propagate in complex environments with less distortion and intensity fluctuation.Overall,this work clearly demonstrates that autofocusing beams exhibit higher stability in prop-agation compared with Gaussian beams,showing great promise for applications such as optical trapping and manipulation in complex environments.
查看更多>>摘要：We propose a frequency-tunable router of single photons with high routing efficiency,which is constructed by two waveguides mediately linked by a single-mode whispering gallery resonator with a driven three-level emitter.Quantum routing probability in the output port is obtained via the real-space Hamiltonian.By adjusting the resonator-emitter cou-pling and the drive,the desired continuous central frequencies for the resonance peaks of routing photons can be manip-ulated nearly linearly,with the assistance of Rabi splitting effect and optical Stark shift.The proposed routing system may provide potential applications in designing other frequency-modulation quantum optical devices,such as multiplexers,filters,and so on.
查看更多>>摘要：A scheme of optical four-level pulse amplitude modulation(PAM-4)is proposed based on dual-Raman process in Rydberg atoms.A probe field counter-propagates with a dual-Raman field which drives the ground and the excited states transition,respectively,and the Rydberg transition is driven by a microwave(MW)field.A gain peak appears in the probe transmission and is sensitive to the MW field strength.Optical PAM-4 can be achieved by encoding an MW signal and decoding the magnitude of a probe signal.Simulation results show that the differential nonlinearity and the integral nonlinearity of the proposed scheme can be reduced by 5 times and 6 times,respectively,compared with the counterparts of previous scheme,and the ratio of level separation mismatch is close to the ideal value 1.Moreover,the scheme is extended to optical PAM-8 signal,which may further improve the spectral efficiency.
查看更多>>摘要：We theoretically study the transmission spectrum of the cavity field in a double-cavity optomechanical system with cross-Kerr(CK)effect.The system consists of two tunneling coupling optomechanical cavities with a mechanical resonator as a coupling interface.By doping CK medium into the mechanical resonator,CK couplings between the cavity fields and the mechanical resonator are introduced.We investigate the effects of CK coupling strength on the transmission spectrum of the cavity field,including the transmission rate,nonreciprocity and four-wave mixing(FWM).We find that the transmission spectrum of the probe field can show two obvious transparent windows,which can be widened by increasing the CK coupling strength.For the transmission between the two cavity fields,the perfect nonreciprocity and reciprocity are present and modulated by CK coupling and phase difference between two effective optomechanical couplings.In addition,the effects of the optomechanical and CK couplings on FWM show that the single peak of FWM is split into three symmetrical peaks due to the introduction of the CK effect.
查看更多>>摘要：Compared with well-developed free space polarization converters,polarization conversion between TE and TM modes in the waveguide is generally considered to be caused by shape birefringence,like curvature,morphology of waveguide cross section and scattering.Here,we study the polarization conversion mechanism in 1-THz-FSR X-cut lithium niobate microrings with multiple-resonance condition,that is the conversion can be implemented by birefringence of waveguides,which will also introduce an avoided-mode crossing.In the experiment,we find that this mode crossing results in severe suppression of one sideband in local nondegenerate four-wave mixing and disrupts the cascaded four-wave mixing on this side.Simultaneously,we propose one two-dimensional method to simulate the eigenmodes(TE and TM)in X-cut microrings,and the mode crossing point.This work will provide one approach to the design of polarization converters and simulation for monolithic photonics integrated circuits,and may be helpful to the studies of missed temporal dissipative soliton formation in X-cut lithium niobate rings.
查看更多>>摘要：We performed ultrasonic measurements on a quaternary cubic compound PrRu2In2Zn18 to explore the ground state properties derived from non-Kramers Γ3 doublet of Pr3+.PrRu2In2Zn18 is a quaternary derivative of the ternary compound PrRu2Zn20 that exhibits a structural phase transition at Ts=138 K.In PrRu2In2Zn18,the Zn atoms at the 16c site in PrRu2Zn20 are selectively replaced by In atoms.A monotonic increase was observed in the temperature dependence of elastic constants CL=(C11+2C12+4C44)/3 and CT=(C11-C12+C44)/3 in the temperature range around Ts to which an elastic softening was observed in(C11-C12)/2 for PrRu2Zn20.The disappearance of the softening indicates that the structural transition in PrRu2Zn20 is suppressed by the substitution of Zn ions by In ones with a larger ionic radius.Alternatively,the CT of PrRu2In2Zn18 exhibits a precursor Curie-type elastic softening toward low temperatures being responsible for the non-Kramers Γ3 ground state.We discuss the ground state and the evolution of the elastic properties of the different single-crystal samples of PrRu2In2Zn18 grown under different conditions.
查看更多>>摘要：As a common transportation facility,speed humps can control the speed of vehicles on special road sections to reduce traffic risks.At the same time,they also cause instantaneous traffic emissions.Based on the classic instantaneous traffic emission model and the limited deceleration capacity microscopic traffic flow model with slow-to-start rules,this paper has investigated the impact of speed humps on traffic flow and the instantaneous emissions of vehicle pollutants in a single lane situation.The numerical simulation results have shown that speed humps have significant effects on traffic flow and traffic emissions.In a free-flow region,the increase of speed humps leads to the continuous rise of CO2,NOX and PM emissions.Within some density ranges,one finds that these pollutant emissions can evolve into some higher values under some random seeds.Under other random seeds,they can evolve into some lower values.In a wide moving jam region,the emission values of these pollutants sometimes appear as continuous or intermittent phenomenon.Compared to the refined NaSch model,the present model has lower instantaneous emissions such as CO2,NOX and PM and higher volatile organic components(VOC)emissions.Compared to the limited deceleration capacity model without slow-to-start rules,the present model also has lower instantaneous emissions such as CO2,NOy and PM and higher VOC emissions in a wide moving jam region.These results can also be confirmed or explained by the statistical values of vehicle velocity and acceleration.
查看更多>>摘要：A fractal geometric boundary with natural wall features is introduced into a hybrid lattice-Boltzmann-method(LBM)multiphase model.The physical model of cavitation bubble collapse near the irregular geometric wall is established to study the thermodynamic characteristics of the bubble collapse.Due to the lack of periodicity,symmetry,spatial uniformity and obvious correlation in the LBM simulation of the bubble collapse near the fractal wall,the morphological analysis based on Minkowski functional is introduced into the thermodynamic investigation of cavitation bubble so as to analyze and obtain the effective information.The results show that the Minkowski functional method can employed to study the temperature information in complex physical fields hierarchically and quantitatively.The high/low temperature region of the cavitation flow is explored,and thermal effect between irregular and fractal geometric wall and cavitation bubble can be revealed.It illustrates that LBM and morphological analysis complement each other,and morphological analysis can also be used as an optional and potential tool in research field of complex multiphase flows.
查看更多>>摘要：The study of a droplet spreading on a circular cylinder under gravity was carried out using the pseudo-potential lattice Boltzmann high-density ratios multiphase model with a non-ideal Peng-Robinson equation of state.The calculation results indicate that the motion of the droplet on the cylinder can be divided into three stages:spreading,sliding,and aggregating.The contact length and contact time of a droplet on a cylindrical surface can be affected by factors such as the wettability gradient of the cylindrical wall,the Bond number,and droplet size.Furthermore,phase diagrams showing the relationship between Bond number,cylinder wall wettability gradient,and contact time as well as maximum contact length for three different droplet sizes are given.A theoretical foundation for additional research into the heat and mass transfer process between the droplet and the cylinder can be established by comprehending the variable rules of maximum contact length and contact time.
查看更多>>摘要：The driven-dissipative Langevin dynamics simulation is used to produce a two-dimensional(2D)dense cloud,which is composed of charged dust particles trapped in a quadratic potential.A 2D mesh grid is built to analyze the center-to-wall dust density.It is found that the local dust density in the outer region relative to that of the inner region is more nonuniform,being consistent with the feature of quadratic potential.The dependences of the global dust density on equilibrium tem-perature,particle size,confinement strength,and confinement shape are investigated.It is found that the particle size,the confinement strength,and the confinement shape strongly affect the global dust density,while the equilibrium temperature plays a minor effect on it.In the direction where there is a stronger confinement,the dust density gradient is bigger.
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