scholarly journals Optical phase singularities and superluminal motion in unbounded space

2021 ◽  
Vol 5 (45) ◽  
pp. 654-660
Author(s):  
V.V. Kotlyar ◽  
A.A. Kovalev ◽  
A.G. Nalimov
Keyword(s):  
Topological Charge ◽  
Initial Plane ◽  
Optical Phase ◽  
Light Speed ◽  
Superluminal Motion ◽  
Remarkable Result ◽  
Phase Singularities ◽  
Waist Radius

In this paper, we summarize a remarkable result obtained by Soskin et al. in Phys Rev A 56, 4064 (1997). We show that for an on-axis superposition of two different-waist Laguerre-Gauss beams with numbers (0, n) and (0, m), the topological charge equals TC=m up to a plane where the waist radii become the same, given that the beam (0, m) has a greater waist radius, changing to TC=n after this plane. This occurs because in the initial plane the superposition has an on-axis op-tical vortex with TC=m and on different axis-centered circles there are (n – m) vortices with TC= +1 and (n – m) vortices with TC= –1. On approaching the above-specified plane, the vortices with TC= -1 "depart" to infinity with a higher-than-light speed, with the TC of the total beam becoming equal to TC=n. If, on the contrary, the beam (0, m) has a smaller waist, then the total TC equals n on a path from the initial plane up to a plane where the waist radii become the same, changing to TC=m after the said plane. This occurs because after the said plane, n–m vortices with TC= –1 "arrive" from infinity with a higher-than-light speed.

Optical phase singularities 'going to' infinity with a higher-than-light speed

2021 ◽  
Author(s):  
Victor V Kotlyar ◽  
Alexey Andreevich Kovalev ◽  
Anton Nalimov
Keyword(s):  
Optical Phase ◽  
Light Speed ◽  
Phase Singularities

scholarly journals Short- and long-range screening of optical phase singularities and C points

2008 ◽  
Vol 281 (17) ◽  
pp. 4194-4204 ◽  
Author(s):  
David A. Kessler ◽  
Isaac Freund
Keyword(s):  
Long Range ◽  
Optical Phase ◽  
Phase Singularities

scholarly journals Spiral phase plate with multiple singularity centers

2020 ◽  
Vol 44 (6) ◽  
pp. 901-908
Author(s):  
V.V. Kotlyar ◽  
A.A. Kovalev ◽  
E.S. Kozlova ◽  
A.P. Porfirev
Keyword(s):  
Topological Charge ◽  
Beam Power ◽  
Phase Plate ◽  
Circular Aperture ◽  
Vortex Beam ◽  
Finite Radius ◽  
Phase Singularity ◽  
Initial Plane ◽  
Topological Charges ◽  
Spiral Phase

We investigate a multispiral phase plate (MSPP) with multiple centers of phase singularity arbitrarily located in the MSPP plane. Equations to describe the topological charge of an optical vortex in the initial plane immediately behind the MSPP and orbital angular momentum (OAM) normalized relative to the beam power are derived. The topological charge in the initial plane is found as a sum of the topological charges of all singularities if their centers are located inside a finite-radius circular aperture. If the phase singularity centers are partially located on the boundary of a circular diaphragm limiting the MSPP, the total topological charge is found as the sum of all singularities divided by 2. Total OAM that the vortex carries depends on the location of the singularity centers: the farther from the center of the plate the singularity center is located, the smaller is its contribution to the OAM. If all singularity centers are located on the boundary of the diaphragm limiting MSPP, then the OAM of the vortex beam equals zero, although in this case the topological charge of the beam is nonzero.

scholarly journals Second-harmonic generation and the conservation of spatiotemporal orbital angular momentum of light

2020 ◽  
Author(s):  
Guan Gui ◽  
Nathan Brooks ◽  
Henry Kapteyn ◽  
Margaret Murnane ◽  
Chen-Ting Liao
Keyword(s):  
Angular Momentum ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Orbital Angular Momentum ◽  
Topological Charge ◽  
Second Harmonic ◽  
Space Time ◽  
Generation Process ◽  
Space And Time ◽  
Phase Singularities

Abstract Light with spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured electromagnetic field with characteristic space-time spiral phase structure and transverse OAM. In this work, we present the first generation and characterization of the second-harmonic of ST-OAM pulses. By uncovering the conservation of transverse OAM in a second-harmonic generation process, where the space-time topological charge of the fundamental field is doubled along with the optical frequency, we establish a general nonlinear scaling rule— analogous to that describing the spatial topological charges associated with the conventional longitudinal OAM of light. Furthermore, we observe that the topology of a second-harmonic ST-OAM pulse can be modified by complex spatiotemporal astigmatism, giving rise to multiple phase singularities separated in space and time. Our finding thus confirms that a spatiotemporal phase winding, surrounding one or many phase singularities in space and time, can be interpreted as a new class of topological charge. Our study opens a new route for nonlinear conversion and scaling of light carrying ST-OAM with the potential for driving other secondary ST-OAM sources of electromagnetic fields, electron pulses, and beyond.

scholarly journals Measuring optical phase singularities at subwavelength resolution

2004 ◽  
Vol 6 (5) ◽  
pp. S189-S196 ◽  
Author(s):  
René Dändliker ◽  
Iwan Märki ◽  
Martin Salt ◽  
Antonello Nesci
Keyword(s):  
Optical Phase ◽  
Subwavelength Resolution ◽  
Phase Singularities

scholarly journals Fresnel and Fraunhofer diffraction of a Gaussian beam with several polarization singularities

2018 ◽  
Vol 42 (2) ◽  
pp. 179-189 ◽  
Author(s):  
A. A. Kovalev ◽  
V. V. Kotlyar
Keyword(s):  
Regular Polygon ◽  
Transverse Plane ◽  
Gaussian Beams ◽  
Optical Vortices ◽  
Far Field ◽  
Radial Polarization ◽  
Fraunhofer Diffraction ◽  
Initial Plane ◽  
Phase Singularities ◽  
Analytic Expression

Alongside phase singularities (optical vortices), there may be light fields with polarization singularities (PS), i.e. isolated intensity nulls with radial, azimuthal, or radial-azimuthal polarization around them. Here, we study Gaussian beams with several arbitrarily located PS. An analytic expression is obtained for their complex amplitude. A partial case is studied when the PS are at the vertices of a regular polygon. If the beam has one or two PS, then these are points with radial polarization. If there are four PS, then two of the points will have azimuthal polarization. It is shown that while propagating in free space, the PS can appear only in a discrete set of planes, in contrast to the phase singularities, which exist in any transverse plane. In the case of two PS, it is shown that their polarization transforms from radial in the initial plane to azimuthal in the far field.

Spiral forces established by optical phase singularities

2010 ◽  
Vol 55 (35) ◽  
pp. 3998-4004
Author(s):  
Xiang Fang ◽  
ZhaoJun Ding ◽  
YanLi Feng ◽  
JianPeng Zhang
Keyword(s):  
Optical Phase ◽  
Phase Singularities

Detection of Phase Singularities in Triangular Meshes

2007 ◽  
Vol 46 (06) ◽  
pp. 646-654 ◽  
Author(s):  
L. Wieser ◽  
M. C. Stühlinger ◽  
F. Hintringer ◽  
B. Tilg ◽  
G. Fischer ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Topological Charge ◽  
Quantitative Data ◽  
Triangular Meshes ◽  
Phase Information ◽  
Time Step ◽  
Phase Singularity ◽  
Cardiac Fibrillation ◽  
Oriented Path ◽  
Phase Singularities

Summary Objectives : Phase singularities have become a key marker in animal and computer models of atrial and ventricular fibrillation. However, existing algorithms for the automatic detection of phase singularities are limited to regular, quadratic mesh grids. We present an algorithm to automatically and exactly detect phase singularities in triangular meshes. Methods : For each node an oriented path inscribing the node with one unit of spatial discretization is identified. At each time step the phase information is calculated for all nodes. The so-called topological charge is also computed for each node. A non-zero (± 2π) charge is obtained for all nodes with a path enclosing a phase singularity. Thus all charged nodes belonging to the same phase singularity have to be clustered. Results : With the use of the developed algorithm, phase singularities can be detected in triangular meshes with an accuracy of below 0.2 mm – independent of the type of membrane kinetics used. Conclusions : With the possibility to detect phase singularities automatically and exactly, important quantitative data on cardiac fibrillation can be gained.

scholarly journals Generation of optical phase singularities by computer-generated holograms

1992 ◽  
Vol 17 (3) ◽  
pp. 221 ◽  
Author(s):  
N. R. Heckenberg ◽  
R. McDuff ◽  
C. P. Smith ◽  
A. G. White
Keyword(s):  
Optical Phase ◽  
Phase Singularities ◽  
Computer Generated Holograms
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