- 标题
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- 实验方案
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Fractional Generalized Inverse Gaussian Process for Population Dynamics of Phase Singularities
摘要： In this paper, a generalized inverse Gaussian (GIG) process is studied in conjunction with the population dynamics of phase singularities (PSs). Special attention is paid to a stochastic analysis of PSs based on combined methods with (i) the theory of information geometry, (ii) the eigenvalue problem related to the double confluent Heun equation, (iii) classification of the statistics (sub-Poisson, Poisson, and super-Poisson), and (iv) fractional generalization to introduce a memory effect. The present theoretical method is applied to describe two-dimensional (2D) spiral wave turbulence in CO oxidation on a Pt surface and in the Aliev–Panfilov model. It is demonstrated that the fractional GIG process with the fractional index μ (μ = 0.5) can capture the profile of the PS number distribution and the scaling law of ω?1.5 in the power spectral density at large frequencies, which have been observed in real experiments and numerical simulations.
关键词： spiral wave turbulence,population dynamics,phase singularities,information geometry,generalized inverse Gaussian process,double confluent Heun equation,fractional generalization
更新于2025-09-23 15:21:21
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Research on image de-disturbing algorithm based on dark channel prior and anisotropic Gaussian filtering
摘要： In order to solve the problem of serious degradation of images collected outdoors in dense fog weather, a defogging algorithm for dense fog images was proposed. The fog-day imaging physical model was simplified; the concept of fog concentration factor was proposed. The single image de-hazing algorithm based on dark channel priors solves the problem of estimating the transmittance of fog and sky scenes. The image recovered by the algorithm is clear and natural. The algorithm has high computational complexity. It takes a long time to meet real-time requirements. The principle of anisotropic Gaussian filtering is introduced. It combines with the dark channel. The value of the fog concentration coefficient is obtained by estimating the visibility value of a single fog image. It is then combined with an anisotropic Gaussian filter of the image to estimate the atmospheric light value. Defogging of the fog image is performed by using the repair function. It is necessary to perform effective de-hazing processing on smog images. Experiments show that the improved algorithm can greatly reduce the complexity of the algorithm while ensuring the defogging effect of the original algorithm.
关键词： anisotropy,Gaussian filter,foggy image removal,dark channel prior principle
更新于2025-09-23 15:21:21
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Sufficient condition for a quantum state to be genuinely quantum non-Gaussian
摘要： We show that the expectation value of the operator position and momentum operators x? and p? with a positive parameter c can serve as a tool to identify quantum non-Gaussian states, that is states that cannot be represented as a mixture of Gaussian states. Our condition can be readily tested employing a highly efficient homodyne detection which unlike quantum-state tomography requires the measurements of only two orthogonal quadratures. We demonstrate that our method is even able to detect quantum non-Gaussian states with positive–definite Wigner functions. This situation cannot be addressed in terms of the negativity of the phase-space distribution. Moreover, we demonstrate that our condition can characterize quantum non-Gaussianity for the class of superposition states consisting of a vacuum and integer multiples of four photons under more than 50 % signal attenuation.
关键词： Wigner functions,quantum information,continuous variables,non-Gaussian states,quadrature measurements,Gaussian state
更新于2025-09-23 15:21:01
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Relativistic Self Focusing and Frequency Shift of super-Gaussian Laser Beam in Plasma
摘要： Relativistic self focusing and frequency shift of laser beam having super-Gaussian profile in space and Gaussian profile in time is studied in a plasma. The relativistic mass nonlinearity is found to cause time dependent self focusing of the laser pulse and the saturation effect of nonlinearity avoids point focusing of the beam. For ultrashort laser pulse, the front of the pulse undergoes frequency down shift while that of the tail undergoes up shift. Frequency shift increases and self focusing becomes stronger for higher intensity of the laser. The self focusing is also stronger for the laser beam carrying larger wavelength.
关键词： Beam width parameter,Self focusing,Frequency shift,super-Gaussian laser,Moment Theory,Relativistic nonlinearity
更新于2025-09-23 15:21:01
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Self-focused amplitude modulated super Gaussian laser beam in plasma and THz radiation with high efficiency
摘要： Based on self- focusing of an amplitude modulated super Gaussian laser beam in preformed ripple density plasma, one scheme can be proposed for generating terahertz (THz) radiation at the modulation frequency when pondermotive nonlinearity is operative. The eikonal in paraxial ray approximation (PRA) along with higher order terms in the expansion of the dielectric function have been taken into account. Intensity variation in the direction transverse to the propagated laser causes a pondermotive force which generates transient transverse nonlinear current. At the modulation frequency, the mentioned current drives radiation in THz domain. Therefore, comparing to simple PRA, inclusion of terms with higher order enhances beam self-focusing, THz radiation field and, efficiency. In addition, the degree of the self-focusing is reduced in higher laser beam orders and has changed by the modulation index and the time. Here, by considering higher order paraxial ray approximation and optimizing laser beam and ripple density, plasma parameters are investigated and the efficiency of THz radiation reaches up to 6.5%. This method can be applied for the efficient types of THz radiation.
关键词： Efficiency,Self-focusing,Terahertz radiation,Super Gaussian beam,Amplitude modulated
更新于2025-09-23 15:21:01
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Laguerre-Gaussian Mode Laser Heater for Microbunching Instability Suppression in Free-Electron Lasers
摘要： Microbunching instability (MBI) driven by beam collective effects is known to be detrimental to high-brightness storage rings, linacs, and free-electron lasers (FELs). One known way to suppress this instability is to induce a small amount of energy spread to an electron beam by a laser heater. The distribution of the induced energy spread greatly affects MBI suppression and can be controlled by shaping the transverse profile of the heater laser. Here, we present the first experimental demonstration of effective MBI suppression using a LG01 transverse laser mode and compare the improved results with respect to traditional Gaussian transverse laser mode at the Linac Coherent Light Source. The effects on MBI suppression are characterized by multiple downstream measurements, including longitudinal phase space analysis and coherent radiation spectroscopy. We also discuss the role of LG01 shaping in soft x-ray self-seeded FEL emission, one of the most advanced operation modes of a FEL for which controlled suppression of MBI is critical.
关键词： Free-electron lasers,Microbunching instability,LG01 mode,Laser heater,Soft x-ray self-seeded FEL,Gaussian mode,MBI suppression
更新于2025-09-23 15:21:01
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Low-divergence relativistic proton jet from a thin solid target driven by an ultra-intense circularly polarized Laguerrea??Gaussian laser pulse
摘要： We propose a new ion acceleration scheme of irradiating a thin solid target with an ultra-intense circularly polarized Laguerre–Gaussian (LG) laser pulse. Three-dimensional particle-in-cell simulations are performed to demonstrate that this scheme can generate a low-divergence high-density relativistic proton jet. By this scheme, the number of protons emitted with a small angle (<1°) from the laser axis can be more than tens of times as high as that of the protons accelerated by a circularly polarized Gaussian pulse. The inward ponderomotive force of the LG pulse drives such a proton beam along the laser axis.
关键词： Laguerre–Gaussian pulse,laser-driven ion acceleration,radiation pressure acceleration
更新于2025-09-23 15:21:01
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Dynamics of an open double quantum dot system via quantum measurement
摘要： We study the dynamics of a double quantum dot (DQD) system interacting with a Gaussian white noise (GWN) environment which is measured by a quantum point contact (QPC) device. With both the transverse and longitudinal noise taken into account, we utilize an effective method by adding an additional Bloch vector to calculate the cumulant generating functions of the electron transfer in the QPC detector based on the full counting statistics. We study the average detector current, Fano factor, and average waiting time of the electron transfer in the presence of decoherence effects of the DQD system caused by both the QPC and the GWN environment. It indicates that the decoherence effects arising from the QPC and the GWN environment have obviously different influences on the electron transfer detected by the QPC device in both short-time and long-time limits. It is shown that the measurement process would localize the electron in a DQD in a short time and that the distribution of the average current and Fano factor versus level displacement in long-time limit are broadened due to the interaction between the system and GWN environment, which provides a reliable method to explore the dynamical behavior of an open quantum system and to extract the characteristics of the environment by analyzing the detector outcome. Our results provide theoretical support for studies of quantum measurement in a semiconductor device affected by a fluctuant environment.
关键词： full counting statistics,Gaussian white noise,quantum point contact,double quantum dot,decoherence
更新于2025-09-23 15:21:01
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[Laser Institute of America ICALEO?? 2017: 36th International Congress on Applications of Lasers & Electro-Optics - Atlanta, Georgia, USA (October 22a??26, 2017)] International Congress on Applications of Lasers & Electro-Optics - Transformation of Gaussian beams into M-beams for advanced microvia drilling
摘要： Typical laser systems produce Gaussian laser beams that may not be suitable for high precision materials processing. This study considers laser microvia drilling of multilayer polymeric substrates for high density interconnects of microelectronics devices. Closely spaced microvias reduce the interconnect distance between the processors to meet the ever increasing demand for transferring large volumes of data at high rates. CO2 lasers of 9.3 μm wavelength is commonly used for drilling microvias in current polymeric substrates because of their higher absorption coefficient at this wavelength than at 10.6 μm wavelength of conventional CO2 lasers. High absorption coefficient provides a volumetric heating mechanism of shallow depth to enable surface-controlled vaporization of the polymeric materials. Gaussian or top-hat laser beams generally leave carbonized polymeric residue at the bottom corner and on the side wall of the microvias, and this residue hinders the subsequent microsoldering of electronic devices to the interconnects. The formation of the residue can be reduced using M-beams for microvia drilling. A thermal model is developed to determine the intensity distribution of the M-beam. To achieve this M-beam from a Gaussian beam, a lens system is designed using the Fresnel diffraction model. Drilling experiments have been conducted using an M-beam and the shape and size of the microvia are found to match the theoretical predictions very well.
关键词： microvia drilling,high density interconnects,Gaussian beams,CO2 lasers,M-beams,polymeric substrates
更新于2025-09-23 15:21:01
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Reducing orbital angular momentum crosstalk of the Bessel Gaussian beam for underwater optical communications
摘要： We derive the analytical expressions of the probabilities for the signal and the crosstalk orbital angular momentum (OAM) states of a high order Bessel Gaussian beam used in underwater optical communications. Our numerical results show that the probabilities of the signal and crosstalk OAM states are effected by the propagation distance and the parameters of the oceanic turbulence. The receiver aperture can be used to reduce the probabilities of the crosstalk OAM states and the probability of the detected signal OAM states keeps almost unchanged. Our results may improve the quality of the optical communications system.
关键词： Bessel Gaussian beam,orbital angular momentum,oceanic turbulence,underwater optical communications
更新于2025-09-23 15:21:01