Angular Momentum of Topologically Structured Darkness

Alperin, Samuel N.; Siemens, Mark E.

doi:10.1103/physrevlett.119.203902

Cited by 49 publications

(28 citation statements)

References 17 publications

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“…4. We find that in our setup using the OAM sorting process, the centre of mass which corresponds to the average OAM also shows a similar behaviour as the measurements of fractional OAM with a cylindrical lens from Alperin et al [24]. As discussed before, due to the phase discontinuity a fractional OAM state may show a non-zero total net linear momentum, which translates to the extrinsic OAM part of the beam.…”

Section: Resultssupporting

confidence: 84%

“…Under a certain angle the total angular momentum as sum of intrinsic and extrinsic OAM can be measured. We find this angle for the total OAM measurement to be θ = 180 • in our setup by utilizing the fact that also half-integer OAM states have no extrinsic OAM components [24]. Only for this orientation, the OAM-sorted intensity distribution shows the same centre of mass for half-integer OAM as the OAM-sorted intensity distribution for the intrinsic OAM measurement at θ = 0 • .…”

Section: Resultsmentioning

confidence: 79%

“…When the orientation angle deviates from 0 • , the peaks start to split into double peaks at positions, which do not match the peak positions for integer OAM states. At an orientation angle of 180 • the peak splitting becomes symmetric with respect to the central position between both nearest integer states.For a more detailed picture, we evaluate the centre of mass and sorted variance for a broader range of fractional OAM states at different orientation angles and compare them to the results of Alperin et al[24]. Here we focus on the relation between the intrinsic and extrinsic OAM components and the total OAM.…”

mentioning

confidence: 99%

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Spectroscopy of fractional orbital angular momentum states

et al. 2018

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We present an approach for measuring the orbital angular momentum (OAM) of light tailored towards applications in spectroscopy and non-integer OAM values. It is based on the OAM sorting method (Berkhout et al., Phys. Rev. Lett. 105, 153601 (2010)). We demonstrate that mixed OAM states and fractional OAM states can be identified using moments of the sorted output intensity distribution and OAM states with integer and non-integer topological charge can be clearly distinguished. Furthermore the difference between intrinsic OAM and total OAM for fractional OAM states is highlighted and the importance of the orientation of the fractional OAM beam is shown. All experimental results show good agreement with simulations. Finally we discuss possible applications of this method for spectroscopy of semiconductor systems such as exciton-polaritons in microcavities.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 79%

mentioning

confidence: 99%

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Spectroscopy of fractional orbital angular momentum states

et al. 2018

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“…5(c). This curve has certain similarity to the practical changes of the effective OAM of such beams [4,16]. For only integer values of α, M 2 T has similar property of linear increase, like those Laguerre-Gaussian beams as a function of integer azimuthal index n [23,24].…”

Section: Another Verification Measurement System Is Shown In the Bottmentioning

confidence: 62%

Vortex strength and beam propagation factor of fractional vortex beams

et al. 2019

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Fractional vortex beams (FVBs) with non-integer topological charges attract much attention due to unique features of propagations, but there still exist different viewpoints on the change of their total vortex strength. Here we have experimentally demonstrated the distribution and number of vortices contained in FVBs at Fraunhofer diffraction region. We have verified that the jumps of total vortex strength for FVBs happens only when non-integer topological charge is before and after (but very close to) any even integer number, which originates from two different mechanisms for generation and movement of vortices on focal plane. Meanwhile, we have also measured the beam propagation factor (BPF) of such FVBs, and have found that their BPF values almost increase linearly in one component and oscillate increasingly in another component. Our experimental results are in good agreement with numerical results.PACS numbers:

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“…The problem of using the properties of optical vortices in various areas of science and technology requires the development of reliable but simple techniques for measuring the spectrum of optical vortices in complex beams scattered by various objects. Therefore, the attention of many researchers is drawn to measuring the orbital angular momentum (OAM) of vortex beams [7,[21][22][23][24][25][26][27][28][29][30] that is directly related to the spectrum of optical vortices. Really, the complex amplitude Ψ x, y, z ðÞ of a composite paraxial beam can be written in the form of a superposition of the orthogonal vortex modes ψ m x, y, z ðÞ…”

Section: Introductionmentioning

confidence: 99%

Digital Sorting of Optical Vortices in Perturbed Singular Beams

Volyar¹,

Bretsko²,

Akimova³

et al. 2021

Nonlinear Optics - From Solitons to Similaritons

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The chapter provides a brief overview of shaping and measuring techniques of the vortex spectra (squared amplitudes and initial phases of vortex modes) including radial indices. The main physical mechanisms causing the formation of laser beams with a complex vortex composition, in particular, in biological media, are indicated, and the need for a digital analysis of vortex spectra is substantiated. It is the analysis of vortex spectra that allows us to find the orbital angular momentum and informational entropy (Shannon's entropy) of perturbed laser beams in real time. In the main part of the chapter, we consider in detail a new approach for measuring vortex spectra without cuts and gluing of the wavefront, based on digital analyzing high-order intensity moments of complex beams and sorting the vortex beam in computer memory sells. It is shown that certain types of weak local inhomogeneities cause a vortex avalanche causing a sharp dips and bursts of the orbital angular momentum spectra and quick ups and downs of the informational entropy. An important object of analysis is also the vortex spectra of beams scattered by simple opaque obstacles such as a hole, a disk, and a sector aperture.

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Angular Momentum of Topologically Structured Darkness

Cited by 49 publications

References 17 publications

Spectroscopy of fractional orbital angular momentum states

Spectroscopy of fractional orbital angular momentum states

Vortex strength and beam propagation factor of fractional vortex beams

Digital Sorting of Optical Vortices in Perturbed Singular Beams

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