Measuring the topological charge of an optical vortex by using a tilted convex lens

Vaity, Pravin; Banerji, J.; Singh, R. P.

doi:10.1016/j.physleta.2013.02.030

Cited by 222 publications

(95 citation statements)

References 12 publications

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“…There are several ways to measure the topological charge of a beam. Some of the methods include the use of tilted spherical lens [39], various apertures [40,41] and interferometric method [42]. However, the interferometric method was chosen since the number of bifurcation in the interference pattern gives the topological charge of the beam automatically.…”

Section: Methodsmentioning

confidence: 99%

OAM beams from incomplete computer generated holograms projected onto a DMD

2017

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We show that optical beams with orbital angular momentum (OAM) can be generated even with incomplete computer generated holograms (CGH). These holograms are made such that random portions of it do not contain any information. We observe that although the beams produced with these holograms are less intense, these beams maintain their shape and that their topological charges are not affected. Furthermore, we show that superposition of two or more beams can be created using separate incomplete CGHs interspersed together. Our result is significant especially since most method to generate beams with OAM for various applications rely on pixelated devices or optical elements with imperfections.

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Section: Methodsmentioning

confidence: 99%

OAM beams from incomplete computer generated holograms projected onto a DMD

2017

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“…The topology is such that all the wavefronts which are disconnected and separated by distance k with each other in an otherwise non-singular beam, become connected thereby forming a single wavefront filling the entire space. The optical vortices can be characterized by various interferometry techniques [4][5][6][7]. In two beam interferometry, fork-type fringes (characteristic of phase singularity) appear at the singular region.…”

Section: Introductionmentioning

confidence: 99%

Singularities in cylindrical vector beams

Verma

Pal

Joshi

et al. 2015

Journal of Modern Optics

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Cylindrical vector beams with azimuthal and radial polarization distributions are studied for singularities. It is shown experimentally that these beams have screw dislocation as well as edge dislocation at the same time. The relation between phase and polarization of light beam is the key to understand this fact. We envisage that this has potential application in phase synthesis using polarization engineering. Further, the polarization singularities in these inhomogeneously polarized beams are examined by measuring Stokes parameters across the cross-section of these beams.

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“…These well-established schemes achieved impressive operation performance for OAM detection. Another simple method that only uses a tilted convex lens was proposed to enable the measurement of the topological charge magnitude and sign25. Despite its simplicity, the footprint of the titled lens is relatively large.…”

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confidence: 99%

Measuring Orbital Angular Momentum (OAM) States of Vortex Beams with Annular Gratings

Zheng

Wang

2017

Sci Rep

113

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Measuring orbital angular momentum (OAM) states of vortex beams is of great importance in diverse applications employing OAM-carrying vortex beams. We present a simple and efficient scheme to measure OAM states (i.e. topological charge values) of vortex beams with annular gratings. The magnitude of the topological charge value is determined by the number of dark fringes after diffraction, and the sign of the topological charge value is distinguished by the orientation of the diffraction pattern. We first theoretically study the diffraction patterns using both annular amplitude and phase gratings. The annular phase grating shows almost 10-dB better diffraction efficiency compared to the annular amplitude grating. We then experimentally demonstrate the OAM states measurement of vortex beams using annular phase grating. The scheme works well even for high-order vortex beams with topological charge value as high as ± 25. We also experimentally show the evolution of diffraction patterns when slightly changing the fractional topological charge value of vortex beam from 0.1 to 1.0. In addition, the proposed scheme shows potential large tolerance of beam alignment during the OAM states measurement of vortex beams.Angular momentum can be divided into spin angular momentum (SAM) and orbital angular momentum (OAM) in paraxial beams, which are related to circular polarization and spatial distribution, respectively. In 1992, Allen and coworkers recognized that helically phased beams comprising an azimuthal phase term exp(ilϕ), have an OAM of lħ per photon, where l is topological charge value, ϕ is azimuthal angle, and ħ is Plank's constant h divided by 2π1 . In recent years, optical beams carrying OAM (i.e. OAM modes), also referred to as vortex beams, have attracted more and more attention owing to their distinct characteristics such as the phase singularity at the beam center and the resultant doughnut shape intensity profiles. OAM modes with different topological charge value l, are theoretically unbounded and orthogonal to each other. Similar to other mode bases in free space or fiber, OAM modes are another basis with which to represent spatial modes. Different mode bases including OAM modes can be employed in mode-division multiplexing (MDM), which a subset of space-division multiplexing (SDM). Very recently, OAM modes have shown great potential for MDM both in free space and fiber-based optical communications [2][3][4][5] . Vortex beams or OAM modes also provide unique opportunities for manipulation of micro-/nano-particles as it asserts torque in addition to forces related to optical intensity gradient, giving rise to orbital and spin movements beyond trapping. Remarkably, for diverse applications of vortex beams in optical communications 2-5 , optical tweezers 6,7 , optical trapping 8 and quantum information technology 9 , an accurate measurement of the topological charge values of vortex beams, which includes the magnitude and the sign, is of great importance.Until now, a wide variety of methods have been proposed t...

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Measuring the topological charge of an optical vortex by using a tilted convex lens

Cited by 222 publications

References 12 publications

OAM beams from incomplete computer generated holograms projected onto a DMD

OAM beams from incomplete computer generated holograms projected onto a DMD

Singularities in cylindrical vector beams

Measuring Orbital Angular Momentum (OAM) States of Vortex Beams with Annular Gratings

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