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- 摘要
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Exploring the optical beam shifts in monolayers of transition metal dichalcogenides using Gaussian beams
摘要： We have extensively studied Goos-H?nchen (GH) and Imbert-Fedorov (IF) shifts for reflection of a fundamental Gaussian beam using transfer matrix method. By considering a dielectric slab coated with monolayer of transition metal dichalcogenides (TMDC), we theoretically investigate the potential role of four different TMDC monolayers (WS2, WSe2, MoS2, and MoSe2) on the spatial and angular GH and IF shifts for reflection of the light beam that has not been explored previously. We find the nature of GH and IF shifts to be explicitly dependent on the mode of polarization of light beam. In case of partial reflection of light, both GH and IF shifts acquire moderate magnitude. In contrary, giant negative spatial GH shifts are examined for total internal reflection. Our analysis revealed that the typical characteristics of GH and IF shifts are significantly affected by the complex surface conductivity of TMDC monolayers and consequently the shifts are found to differ for different TMDC monolayers. We also present a comparison of the beam shifts for the monolayer TMDC-coated surfaces with the corresponding bulk TMDCs. Finally, we address the most significant question of how the GH and IF shifts depend upon the wavelengths of incident light, in particular, establishing the role of optical conductivity in beam shifts.
关键词： Light matter interaction,Goos-H?nchen shift,Surface Optics,Gaussian beam,Transition metal dichalcogenides,Imbert-Fedorov shift
更新于2025-09-23 15:23:52
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[IEEE 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Xuzhou (2018.7.21-2018.7.24)] 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Gaussian Beam Scattering from a Sphere on or Near a Plane Surface
摘要： A theoretical procedure is presented for calculating the scattered fields from a sphere on or near a plane surface. The incident Gaussian beam is expanded in series of cylindrical vector wave functions, and the scattered as well as internal fields in series of spherical ones. By using the boundary conditions and the method of moments technique, the unknown expansion coefficients are determined. Numerical results of the normalized differential scattering cross section are given, and the scattering characteristics are discussed concisely.
关键词： sphere above a plane surface,Scattering,Gaussian beam
更新于2025-09-23 15:23:52
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Controlling the relativistic self-focusing of Hermite-cosh-Gaussian beams in plasma
摘要： The purpose of current study was to find the effects of Hermite-cosh-Gaussian (HChG) beam characteristics on the relativistic self-focusing. The Self-focusing Parameter (SFP), for mode indexes of m=0, 1, and 2 is proposed which provides a basis for achieving the nonlinear self-focusing dependencies on the beam characteristics. The dissimilar nonlinear self-focusing dependencies of different mode indexes on the initial intensity and decentered parameter of HChG beam are founded. The predictions of SFP model are then validated by investigating the beam focusing/diverging along the propagation axis and the exact conformity is observed. The results of introduced model can by applied for HChG beams with higher mode indexes, the Hermite Gaussian and cosh-Gaussian beams.
关键词： Hermite-cosh-Gaussian beam,mode indices,Decentered parameter,Plasma,Relativistic self-focusing
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Radar (RADAR) - Brisbane, Australia (2018.8.27-2018.8.31)] 2018 International Conference on Radar (RADAR) - Radar Cross Section of Modified Target Using Gaussian Beam Methods: Experimental Validation
摘要： The aim of this paper is to study the Radar Cross Section (RCS) of modified radar targets (plate with notch) using Gaussian Beam techniques. The Gaussian methods used in this work are Gaussian Beam Summation (GBS) and Gaussian Beam Launching (GBL). We establish the theoretical formulation of the GBS and GBL techniques and analyze the influence of the main Gaussian beam parameters on the variation of the scattered field. Then, we present the simulations of RCS. The numerical results are compared with PO, MoM methods, and also with experimental measurements performed in the anechoic chamber at Lab-STICC (ENSTA Bretagne).
关键词： Radar Cross Section (RCS),Physical Theory of Diffraction (PTD),Physical Optic (PO),Gaussian Beam Summation (GBS),Gaussian Beam Launching(GBL),Method of Moment (MoM)
更新于2025-09-23 15:22:29
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Bandwidth-limited orbital angular momentum mode of Bessel Gaussian beams in the moderate to strong non-Kolmogorov turbulence
摘要： We investigate the effects of the moderate to strong fluctuation on the propagation of orbital angular momentum (OAM) modes carried by Bessel Gaussian beams in turbulent atmosphere. The analytic expression of the received probability of the signal and crosstalk OAM mode is derived based on the theories of extended Rytov and non-Kolmogorov turbulence. Our results show that turbulence with smaller non-Kolmogorov index, smaller inner-scale factor is more easily to induce OAM crosstalk between modes. With the increase of turbulence strength, the OAM spreads from adjacent modes to peripheral modes. Our results also indicate that the received signal intensity can be improved by use of Bessel Gaussian beams with small initial radii of beam, low OAM quantum number and long wavelength.
关键词： Bandwidth-limited mode,Non-Kolmogorov turbulence,Extended Rytov theory,Bessel Gaussian beam,Orbital angular momentum
更新于2025-09-23 15:22:29
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Tuning of non-paraxial effects of the Laguerre-Gaussian beam interacting with the two-component Bose–Einstein condensates
摘要： We present the theory of microscopic interaction of the spin-orbit coupled focused Laguerre-Gaussian beam with the two-component Bose–Einstein condensate, composed of two hyperfine states of 87Rb in a harmonic trap. We have shown that Raman Rabi frequency distributions over the inter-component coupling identify phase separation coupling strength. A significant enhancement of side-band transitions due to non-paraxial nature of vortex beam is observed for particular values of inter-component coupling around 1.25 and 0.64 in unit of 5.5 nm for 105 and 106 number of atoms, respectively. The uncertainty in the estimation of these coupling strengths is improved with the focusing angles of the beam. We discuss an experimental scheme to verify this non-paraxial effect on ultra-cold atoms.
关键词： Laguerre-Gaussian beam,Bose–Einstein condensate,non-paraxial effects
更新于2025-09-23 15:22:29
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An optimized space-time Gaussian beam migration method with dynamic parameter control
摘要： In the Gaussian beam (GB) method, initial beam parameters are principal factors influencing the accuracy and computational efficiency of seismic depth imaging. Various optimized beam parameter strategies for Gaussian beam migration (GBM) have been proposed to improve imaging quality as well as computational efficiency, while optimized space-time Gaussian beam schemes for seismic migration have still not been fully investigated. In this paper, an optimized space-time Gaussian beam approach with dynamic parameter control for seismic depth imaging is developed. We first provide an expression for dynamic beam parameter by taking in account the effect of velocity field variation on the beam forming. Based on dynamic beam parameters, the new space-time adaptive Gaussian beam generated by an arbitrary source wavelet is obtained, which can adaptively calculate the beam width to make the seismic beam energy better focused in the central ray neighborhood. Then, the forward wavefield is constructed in two-dimensional (2D) acoustic media by space-time adaptive Gaussian beam for the implementation of migration. Adhering to the framework of conventional space-time Gaussian beam method, we perform the up-going ray tracing from subsurface imaging points to the receiver surface to compute the asymptotic Green function for the construction of the backward wavefield. Numerical experiments demonstrate that the new presented approach has a superior accuracy for seismic depth imaging in both shallow and deep regions compared to the conventional space-time Gaussian beam migration scheme.
关键词： Space-time Gaussian beam,Green function,Up-going ray tracing,Dynamic beam parameter
更新于2025-09-23 15:21:21
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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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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
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Focusing properties of spirally polarized sinh Gaussian beam
摘要： The tight focusing properties of spirally polarized sinh-Gaussian beam is investigated numerically by vector diffraction theory. Results show that the optical intensity in focal region of spirally polarized sinh Gaussian beam can be altered considerably by the beam order, relative waist width and the spiral parameter that indicates the polarization spiral degree of the spirally polarized sinh Gaussian beam. Many novel focal patterns including flattop profile, focal hole axially separated focal spots and focal spot with long focal depth are evolved considerably for the suitable beam parameters. We expect such a tunable focal patterns are useful for optical manipulation of micro particles.
关键词： Vector diffraction theory,spirally polarized sinh Gaussian beam,Focusing property
更新于2025-09-23 15:21:01