共查询到20条相似文献,搜索用时 15 毫秒
1.
Manoj Kumar Sharma Joby Joseph Paramasivam Senthilkumaran 《Applied physics. B, Lasers and optics》2014,117(1):325-332
In spatial filtering experiments, the use of vortex phase filters plays an important role in realizing isotropic edge enhancement. In this paper, we report the use of a vortex dipole phase filter in spatial filtering. A dipole made of fractional vortices is used, and its filtering characteristics are studied. It is observed that the filter performance can be tuned by varying the distance of separation between the vortices of the dipole to achieve better contrast and output noise suppression, and when this distance tends to infinity, the filter performs like a 1-D Hilbert mask. Experimental and simulation results are presented. 相似文献
2.
Swartzlander GA 《Optics letters》2006,31(13):2042-2044
A vortex lens is a useful optical device having applications ranging from astronomy to microscopy. Current vortex masks operate across a narrow bandwidth. Two design schemes are proposed for creating a vortex across a bandwidth exceeding 100 nm in the visible region of the spectrum. 相似文献
3.
S. V. Iordanski 《JETP Letters》2008,87(10):581-585
It is demonstrated that all observed fractions at moderate Landau-level fillings for the quantum Hall effect can be obtained
without recourse to the phenomenological concept of composite fermions. The possibility of having the special topologically
nontrivial many-electron wavefunctions is considered. Their group classification indicates the special values of the electron
density in the ground states separated by a gap from the excited states.
The text was submitted by the author in English. 相似文献
4.
An analytical expression for a Lorentz-Gauss vortex beam passing through a fractional Fourier transform (FRFT) system is derived. The influences of the order of the FRFT and the topological charge on the normalized intensity distribution, the phase distribution, and the orbital angular momentum density of a Lorentz-Gauss vortex beam in the FRFT plane are examined. The order of the FRFT controls the beam spot size, the orientation of the beam spot, the spiral direction of the phase distribution, the spatial orientation of the two peaks in the orbital angular momentum density distribution, and the magnitude of the orbital angular momentum density. The increase of the topological charge not only results in the dark-hollow region becoming large, but also brings about detail changes in the beam profile. The spatial orientation of the two peaks in the orbital angular momentum density distribution and the phase distribution also depend on the topological charge. 相似文献
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6.
《Nuclear Physics B》2004,679(3):597-620
An ideal gas of two-dimensional Dirac fermions in the background of a pointlike magnetic vortex with arbitrary flux is considered. We find that this system acquires fractional electric charge at finite temperatures and determine the functional dependence of the thermal average and quadratic fluctuation of the charge on the temperature, the vortex flux, and the continuous parameter of the boundary condition at the location of the vortex. 相似文献
7.
Fractional Talbot effect in a Selfoc gradient-index lens 总被引:2,自引:0,他引:2
The fractional Talbot effect is demonstrated inside a standard 0.25-pitch Selfoc gradient-index lens under uniform illumination. Comparisons with theoretical expressions of positions and magnification of fractional Talbot images are given. 相似文献
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9.
We investigate the influence of the coma of the lens on the focusing of partially coherent vortex beams. On the basis of the
generalized Huygens-Fresnel diffraction integral, the formula for the intensity distribution in the focal plane is derived.
The numerically calculated results are given to show that the coma of the lens leads to the asymmetry of focused intensity
distribution. The influence of coherence length on the focused intensity distribution is also investigated. It is found that
the effect of coma is not obvious when the coherence length is small. Intensity profiles for three different values of the
azimuthal angle are plotted to illustrate the effect of coma and the influence of coherence length. 相似文献
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11.
The focus-shaping technique of a cylindrically polarized vortex beam by a high numerical-aperture lens is reported. Such a polarized vortex beam is decomposed into radial and azimuthal polarization. It is shown that the total intensity distribution in the focal region is dependent not only on the numerical-aperture maximal angle and the polarization rotation angle but also on the topological charge. By choosing the proper combination of parameters, the adjustably confined flat-topped focus and focal hole can be obtained. The focus-shaping technique may find wide applications, such as optical tweezers, laser printing and material processing. 相似文献
12.
Xiaoyun Liu 《Optik》2009,120(12):574-578
Based on the propagation law of partially coherent beams, the propagation equations of the partially coherent vortex beams focused by an aperture lens are derived. Based on these equations, the focal shift of partially coherent vortex beams is studied, and illustrative numerical results are given. It is found that the focal shift of the partially coherent vortex is dependent not only on the Fresnel number but also on the relative coherent length and the topological charge of the vortex. 相似文献
13.
We demonstrate, analytically and experimentally, a simple, but effective method to determine the topological charge of an optical vortex by using a spherical bi-convex lens, a ubiquitous optical element found in any optics laboratory. Just by tilting the lens and recording the intensity distribution of a propagating vortex at a predicted position past the lens, we have been able to measure both the sign and the magnitude of the topological charge m up to m=±14. Our experimental results are in excellent agreement with analytical predictions. 相似文献
14.
Dumitru Baleanu Ali Khalili Golmankhaneh Alireza Khalili Golmankhaneh Mihaela Cristina Baleanu 《International Journal of Theoretical Physics》2009,48(11):3114-3123
The generalized physics laws involving fractional derivatives give new models and conceptions that can be used in complex
systems having memory effects. Using the fractional differential forms, the classical electromagnetic equations involving
the fractional derivatives have been worked out. The fractional conservation law for the electric charge and the wave equations
were derived by using this method. In addition, the fractional vector and scalar potentials and the fractional Poynting theorem
have been derived. 相似文献
15.
The Fourier transform method is used to solve fractional Poisson’s equation with Riesz fractional derivative of order α. It is shown that the solution is given in terms of the fractional dimensional space D. Gauss law for the electrostatic problem is given and the total electric flux is obtained in terms of α and D. 相似文献
16.
Experimental dynamics of a vortex within a vortex 总被引:1,自引:0,他引:1
We report the experimental dynamics of a new two-dimensional (2D) fluid phenomenon that occurs when an intense, pointlike vortex is placed within a diffuse, circular vortex. Our observations, made using strongly magnetized electron columns to model the 2D fluid, support the analysis performed by Jin and Dubin. 相似文献
17.
A simple-yet plausible-model for B-type vortex breakdown flows is postulated; one that is based on the immersion of a pair of slender coaxial vortex rings in a swirling flow of an ideal fluid rotating around the axis of symmetry of the rings. It is shown that this model exhibits in the advection of passive fluid particles (kinematics) just about all of the characteristics that have been observed in what is now a substantial body of published research on the phenomenon of vortex breakdown. Moreover, it is demonstrated how the very nature of the fluid dynamics in axisymmetric breakdown flows can be predicted and controlled by the choice of the initial ring configurations and their vortex strengths. The dynamic intricacies produced by the two ring + swirl model are illustrated with several numerical experiments. 相似文献
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19.
A theoretical view of vortex core states and of their effects on physics of vortices in clean s- and d-wave-type II superconductors is presented based on a semi-classical picture of a vortex core as an Andreev potential well containing many quasiparticle states. We discuss the density of states, the vortex dissipation, Hall effect, and the vortex mass. The dynamic characteristics are determined by relaxation of core excitations driven by a moving vortex. In a d-wave superconductor, gap nodes make the core states more extended and introduce novel features into thermodynamics and kinetics of vortices. 相似文献
20.
Walter Wyss 《Foundations of Physics Letters》1991,4(3):235-246
Fractional noiseN(t),t 0, is a stochastic process for every , and is defined as the fractional derivative or fractional integral of white noise. For = 1 we recover Brownian motion and for = 1/2 we findf
–1-noise. For 1/2 1, a superposition of fractional noise is related to the fractional diffusion equation. 相似文献