scholarly journals Backward flow of energy for an optical vortex with arbitrary integer topological charge

2018 ◽  
Vol 42 (3) ◽  
pp. 408-413
Author(s):  
V. V. Kotlyar ◽  
A. A. Kovalev ◽  
A. G. Nalimov
Keyword(s):  
Energy Flow ◽  
Topological Charge ◽  
Optical Vortex ◽  
Radial Coordinate ◽  
Arbitrary Integer ◽  
Absolute Value ◽  
Left Hand ◽  
Electric And Magnetic Fields ◽  
Sharp Focusing ◽  
Focus Intensity

We analyze the sharp focusing of an arbitrary optical vortex with the integer topological charge m and circular polarization in an aplanatic optical system. Explicit formulas to describe all projections of the electric and magnetic fields near the focal spot are derived. Expressions for the near-focus intensity (energy density) and energy flow (projections of the Pointing vector) are also derived. The expressions derived suggest that for a left-hand circularly polarized optical vortex with m > 2, the on-axis backward flow is equal to zero, growing in the absolute value as a power 2(m – 2) of the radial coordinate. These relations also show that upon the negative propagation, the energy flow rotates around the optical axis.

scholarly journals The near-axis backflow of energy in a tightly focused optical vortex with circular polarization

2018 ◽  
Vol 42 (3) ◽  
pp. 392-400 ◽  
Author(s):  
V. V. Kotlyar ◽  
A. G. Nalimov ◽  
S. S. Stafeev
Keyword(s):  
Energy Flow ◽  
Focal Plane ◽  
Topological Charge ◽  
Optical Axis ◽  
Optical Vortex ◽  
Diffractive Lens ◽  
Circularly Polarized ◽  
Left Hand ◽  
Maximum Value ◽  
Airy Disk

Using the Richards-Wolf formulae for a diffractive lens, we show that in the focal plane of a sharply focused left-hand circularly polarized optical vortex with the topological charge 2 there is an on-axis backflow of energy (as testified by the negative axial projection of the Poynting vector). The result is corroborated by the FDTD-aided rigorous calculation of the diffraction of a left-hand circularly polarized plane wave by a vortex zone plate with the topological charge 2 and the NA≈1. Moreover, the back- and direct flows of energy are comparable in magnitude. We have also shown that while the backflow of energy takes place on the entire optical axis, it has a maximum value in the focal plane, rapidly decreasing with distance from the focus. The length of a segment along the optical axis at which the modulus of the backflow drops by half (the depth of backflow) almost coincides with the depth of focus, and the transverse circle in which the energy flow is reversed roughly coincides with the Airy disk.

scholarly journals Topological charge of optical vortices and their superpositions

2020 ◽  
Vol 44 (2) ◽  
pp. 145-154
Author(s):  
V.V. Kotlyar ◽  
A.A. Kovalev ◽  
A.V. Volyar
Keyword(s):  
Finite Number ◽  
Topological Charge ◽  
Optical Axis ◽  
Weight Coefficient ◽  
Optical Vortex ◽  
Optical Vortices ◽  
Vortex Center ◽  
Absolute Value ◽  
The Individual ◽  
Weight Coefficients

An optical vortex passed through an arbitrary aperture (with the vortex center found within the aperture) or shifted from the optical axis of an arbitrary axisymmetric carrier beam is shown to conserve the integer topological charge (TC). If the beam contains a finite number of off-axis optical vortices with different TCs of the same sign, the resulting TC of the beam is shown to be equal to the sum of all constituent TCs. For a coaxial superposition of a finite number of the Laguerre-Gaussian modes (n, 0), the resulting TC equals that of the mode with the highest TC (including sign). If the highest positive and negative TCs of the constituent modes are equal in magnitude, then TC of the superposition is equal to that of the mode with the larger (in absolute value) weight coefficient. If both weight coefficients are the same, the resulting TC equals zero. For a coaxial superposition of two different-amplitude Gaussian vortices, the resulting TC equals that of the constituent vortex with the larger absolute value of the weight coefficient amplitude, irrespective of the relation between the individual TCs.

scholarly journals Supercontinuum optical vortex pulse generation without spatial or topological-charge dispersion

2009 ◽  
Vol 17 (17) ◽  
pp. 14517 ◽  
Author(s):  
Yu Tokizane ◽  
Kazuhiko Oka ◽  
Ryuji Morita
Keyword(s):  
Topological Charge ◽  
Optical Vortex ◽  
Pulse Generation

scholarly journals Mie scattering distinguishes the topological charge of an optical vortex: a homage to Gustav Mie

2009 ◽  
Vol 11 (1) ◽  
pp. 013046 ◽  
Author(s):  
Valeria Garbin ◽  
Giovanni Volpe ◽  
Enrico Ferrari ◽  
Michel Versluis ◽  
Dan Cojoc ◽  
...  
Keyword(s):  
Topological Charge ◽  
Optical Vortex ◽  
Mie Scattering

scholarly journals DETERMINATION OF AN OPTICAL VORTEX TOPOLOGICAL CHARGE USING AN ASTIGMATIC TRANSFORM

2016 ◽  
Vol 40 (6) ◽  
pp. 781-792 ◽  
Author(s):  
V. V. Kotlyar ◽  
A. A. Kovalev ◽  
A. P. Porfirev
Keyword(s):  
Topological Charge ◽  
Optical Vortex

Topological Charge in Situ Measuring of Perfect Optical Vortex

2019 ◽  
Vol 48 (7) ◽  
pp. 726001
Author(s):  
任斐斐 REN Fei-fei ◽  
梁言生 LIANG Yan-sheng ◽  
蔡亚楠 CAI Ya-nan ◽  
何旻儒 HE Min-ru ◽  
雷铭 LEI Ming ◽  
...  
Keyword(s):  
Topological Charge ◽  
Optical Vortex

scholarly journals Topological Charge Detection Using Generalized Contour-Sum Method from Distorted Donut-Shaped Optical Vortex Beams: Experimental Comparison of Closed Path Determination Methods

2019 ◽  
Vol 9 (19) ◽  
pp. 3956
Author(s):  
Wang ◽  
Huang ◽  
Toyoda ◽  
Liu
Keyword(s):  
Topological Charge ◽  
Circle Method ◽  
Transformation Method ◽  
Optical Vortex ◽  
Experimental Comparison ◽  
Average Intensity ◽  
Closed Path ◽  
Light Modulator ◽  
Watershed Transformation ◽  
Determination Methods

A generalized contour-sum method has been proposed to measure the topological charge (TC) of an optical vortex (OV) beam using a Shack–Hartmann wavefront sensor (SH-WFS). Moreover, a recent study extended it to be workable for measuring an aberrated OV beam. However, when the OV beam suffers from severe distortion, the closed path for circulation calculation becomes crucial. In this paper, we evaluate the performance of five closed path determination methods, including watershed transformation, maximum average-intensity circle extraction, a combination of watershed transformation and maximum average-intensity circle extraction, and perfectly round circles assignation. In the experiments, we used a phase-only spatial light modulator to generate OV beams and aberrations, while an SH-WFS was used to measure the intensity profile and phase slopes. The results show that when determining the TC values of distorted donut-shaped OV beams, the watershed-transformed maximum average-intensity circle method performed the best, and the maximum average-intensity circle method and the watershed transformation method came second and third, while the worst was the perfect circles assignation method. The discussions that explain our experimental results are also given.

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