&lt;title&gt;Free-space evolution of monochromatic mixed screw-edge wavefront dislocations&lt;/title&gt;

Vasnetsov, M. V.; Basistiy, I. V.; Soskin, M. S.

doi:10.1117/12.317711

Cited by 14 publications

(10 citation statements)

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“…An infinite chain of alternating-sign vortices for α = 1/2, persisting into the far field, is also described in [4] for the case of illumination by a beam of finite width, and it is pointed out that most of these lie in regions where the beam is very faint (i.e. large ρ) and so are hard to observe.…”

Section: Vortices Near the Positive X Axis For A Half-integer Stepmentioning

confidence: 99%

“…Moreover, spiral phase plates are commonly illuminated not by plane waves but by beams (e.g. Gaussian) of finite width [4,5]; such beams are easy to simulate numerically [2], and can easily be incorporated into the analytical theory, as described briefly below. The effects of finite width will be studied in detail elsewhere, since the model (2) already contains a rich structure of optical vortices, worth exploring for its own sake.…”

Section: Introductionmentioning

confidence: 99%

“…Then the initial wave (2) contains not only a fractionalorder singularity at R = 0 but also a step discontinuity along the positive x axis, which must also be healed by propagation to z > 0. Of course, vortices with fractional strength cannot propagate in free space [4]; instead, the step at z = 0 breaks up into a collection of strength ±1 vortices [5], in an intricate arrangement, described in detail, with interesting interactions as α increases through halfinteger values. Section 4 describes a curious analogy between diffraction from helicoidal phase steps and the Aharonov-Bohm effect [6] of quantum mechanics.…”

Section: Introductionmentioning

confidence: 99%

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Optical vortices evolving from helicoidal integer and fractional phase steps

Berry

2004

J. Opt. A: Pure Appl. Opt.

605

348

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The evolution of a wave starting at z = 0 as exp(iαφ) (0 φ < 2π), i.e. with unit amplitude and a phase step 2πα on the positive x axis, is studied exactly and paraxially. For integer steps (α = n), the singularity at the origin r = 0 becomes for z > 0 a strength n optical vortex, whose neighbourhood is described in detail. Far from the axis, the wave is the sum of exp{i(αφ + kz)} and a diffracted wave from r = 0. The paraxial wave and the wave far from the vortex are incorporated into a uniform approximation that describes the wave with high accuracy, even well into the evanescent zone. For fractional α, no fractional-strength vortices can propagate; instead, the interference between an additional diffracted wave, from the phase step discontinuity, with exp{i(αφ + kz)} and the wave scattered from r = 0, generates a pattern of strength-1 vortex lines, whose total (signed) strength S α is the nearest integer to α. For small |α − n|, these lines are close to the z axis. As α passes n + 1/2, S α jumps by unity, so a vortex is born. The mechanism involves an infinite chain of alternating-strength vortices close to the positive x axis for α = n + 1/2, which annihilate in pairs differently when α > n + 1/2 and when α < n + 1/2. There is a partial analogy between α and the quantum flux in the Aharonov-Bohm effect.

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Section: Vortices Near the Positive X Axis For A Half-integer Stepmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical vortices evolving from helicoidal integer and fractional phase steps

Berry

2004

J. Opt. A: Pure Appl. Opt.

605

348

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“…We find that the intrinsic OAM of such a beam containing a single off-axis vortex is noninteger and decreases exponentially with the square of the displacement of the vortex from the center of the beam in the near field. Note that this approach is fundamentally different from the approach using mixed screw-edge dislocation devices, 4,26,27 as can be shown by performing a mode decomposition; with the method outlined here 5 LG components sufficiently (ϳ88%) describe the ᐉ ϭ 1/2 beam, in contrast to the 11 LG components required when a device with a mixed screw-edge dislocation is used.…”

Section: Discussionmentioning

confidence: 99%

“…Examples of these are spiral phase plates and fork holograms with half-integer dislocation strength. 4,26,27 The method outlined in the present paper has thus added flexibility by the ability to simply tune the OAM. We will show that the OAM of the output beam calculated in the way presented here is intrinsic.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic orbital angular momentum of paraxial beams with off-axis imprinted vortices

et al. 2004

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We investigate the orbital angular momentum (OAM) of paraxial beams containing off-axis phase dislocations and put forward a simple method to calculate the intrinsic orbital angular momentum of an arbitrary paraxial beam. Using this approach we find that the intrinsic OAM of a fundamental Gaussian beam with a vortex imprinted off axis has a Gaussian dependence on the vortex displacement, implying that the expectation value of the intrinsic OAM of a photon can take on a continuous range of values (i.e., integer and noninteger values in units of h). Finally, we investigate, both numerically and experimentally, the far-field profiles of beams carrying half-integer OAM per photon, these beams having been created by the method of imprinting off-axis vortices.

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Propagation characteristics of circular-linear edge dislocation beams

Gao

Bai

2021

Opt Quant Electron

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<title>Free-space evolution of monochromatic mixed screw-edge wavefront dislocations</title>

Cited by 14 publications

References 0 publications

Optical vortices evolving from helicoidal integer and fractional phase steps

Optical vortices evolving from helicoidal integer and fractional phase steps

Intrinsic orbital angular momentum of paraxial beams with off-axis imprinted vortices

Propagation characteristics of circular-linear edge dislocation beams

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