Determining topological charge of an optical beam using a wedged optical flat

Khajavi, Behzad; Galvez, Enrique J.

doi:10.1364/ol.42.001516

Cited by 43 publications

(16 citation statements)

References 19 publications

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“…The shear interference pattern of a beam bearing an optical vortex of topological charge has the following characteristics [23] (details of the interferometer and a visual schematic of the angular parameters are shown in Section 5.1):…”

Section: Shear Interference Patternmentioning

confidence: 99%

“…Numerous methods have been developed for the detection of optical modes of a beam bearing an optical vortex. They include non-collinear interferometry of the beam with itself [15], or in nested interferometers bearing parity-changing optical elements [16], or more simply, with single optical elements, such as a double slit [17], a single slit [18], a triangular aperture [19], cylindrical lenses [20], conformational optics [21], decoding by phase reconstruction and imaging [3,22], a shear interferometer [23] or a space-variant half-wave plate [24]. Beyond a beam carrying a singly-or multiply-charged vortex, it is quite necessary to be able to detect superpositions or to be able to sort the modal content of beams.…”

Section: Introductionmentioning

confidence: 99%

“…A more conventional approach is one that uses shear interferometry to recognize the vortex [27]. We also use shear interference by a single element, an extension of a method developed by two of us [23]. Some of the advantages of this method include: the use of very few optical elements, the determination of both the sign and magnitude of the vortices and its availability either commercially as a unit or easily constructed with standard optical components.…”

Section: Introductionmentioning

confidence: 99%

“…We start the article with the theoretical underpinnings, which are a summary of previous analyses adapted to the present problem [23,28]. This is divided into the two key aspects of the generated patterns: Section 2.1 for modal superpositions and Section 2.2 for shear interferometry.…”

Section: Introductionmentioning

confidence: 99%

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Determining Vortex-Beam Superpositions by Shear Interferometry

2018

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Optical modes bearing optical vortices are important light systems in which to encode information. Optical vortices are robust features of optical beams that do not dissipate upon propagation. Thus, decoding the modal content of a beam is a vital component of the process. In this work, we present a method to decode modal superpositions of light beams that contain optical vortices. We do so using shear interferometry, which presents a simple and effective means of determining the vortex content of a beam, and extract the parameters of the component vortex modes that constitute them. We find that optical modes in a beam are easily determined. Its modal content can be extracted when they are of comparable magnitude. The use of modes of well-defined topological charge, but not well-defined radial-mode content, such as those produced by phase-only encoding, are much easier to diagnose than pure Laguerre–Gauss modes.

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Section: Shear Interference Patternmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determining Vortex-Beam Superpositions by Shear Interferometry

2018

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“…For these applications, identifying the OAM states carried by an arbitrary light beam is an essential and significant problem. In some earlier works, the OAM topological charge is extracted by analyzing intensity distributions after passing some optical elements, such as double slits [11], triangular apertures [12], single slits [13], wedged flat [14], and annular gratings [15]. For these methods, it is hard to measure the whole OAM spectrum since the detected charge range is limited by a certain optical element.…”

mentioning

confidence: 99%

Measuring the orbital angular momentum spectrum with a single point detector

Zhao

Feng

et al. 2018

Opt. Lett.

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It is tough work to measure the orbital angular momentum (OAM) spectrum due to the requirement of a reference light or photodetector arrays, while measuring the spin angular momentum (SAM) is readily convenient and matured. In this work, the so-called OAM-SAM nonseparable states are employed, and the OAM spectrum can be obtained only by measuring the Stokes parameters of an arbitrary light beam with low loss noncascading structure and a single point detector. According to the experimental results, the fidelity of the measured OAM spectrum can be as high as 95.2% and 94.3% for OAM eigenstates and superposed states, respectively.Verified by Allen et al. in 1992, the orbital angular momentum (OAM) can be well defined by a Laguerre-Gaussian light beam with azimuthal phase term of expil ϕ [1], which can also be treated as the l th eigenstate of an infinite Hilbert space. One of the unique characteristics of OAM beams is their high dimensional nature, which has attracted research interest for various applications of free space [2] and on-chip [3] optical communications, optical imaging [4], and quantum information [5], including high performance quantum metrology [6], new quantum communication protocols [7], quantum dense coding [8], quantum simulation [9], and quantum cryptography [10]. For these applications, identifying the OAM states carried by an arbitrary light beam is an essential and significant problem. In some earlier works, the OAM topological charge is extracted by analyzing intensity distributions after passing some optical elements, such as double slits [11], triangular apertures [12], single slits [13], wedged flat [14], and annular gratings [15]. For these methods, it is hard to measure the whole OAM spectrum since the detected charge range is limited by a certain optical element. Recently, several improved approaches for measuring the OAM spectrum emerged; the operation principles include the rotational Doppler effect [16] and interference pattern analysis [17,18]. However, since a reference light beam is required, these methods cannot be applied to single photon measurement. Another approach toward the OAM spectrum is an OAM sorter, which is available for single photons with high performance and low insertion loss. Representative methods are based on cascaded OAM beamsplitters [19,20] and optical field transformation [21], which is further developed to reduce the overlap between adjacent eigenstates of OAM [22] and minimize the device footprint [23]. Most recently, the complete OAM density matrix of a single photon can be characterized [24]. Furthermore, with the help of an interferometer, the OAM spectrum of parametric downconverted photons with high Schmidt number has been successfully extracted [25]. However, either a charge coupled device (CCD) or photodetector array is still required, which is obviously not cost effective. As mentioned above, how to identify the OAM spectrum with a single point detector and without a reference light beam is still an open question.In this work, an approach with a ...

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Tunable Liquid Crystal Twisted‐Planar Fresnel Lens for Vortex Topology Determination

Melnikova,

Pantsialeyeva,

Gorbach

et al. 2024

Laser & Photonics Reviews

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The development of straightforward and effective methods to determine the topological charge of phase singular beams is crucial for broadening the applications of optical vortices. Here, a straightforward and elegant method for determining the topological charge of an optical vortex using an innovative switchable achromatic nematic liquid crystal Fresnel lens is proposed. The approach allows for the unambiguous determination of both the absolute value and the sign of the topological charge of a singular beam across a wide range of the visible spectrum, as demonstrated both experimentally and theoretically. The research outcomes are promising for applications in optical information transmission systems, cryptography, and quantum computing.

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Determining topological charge of an optical beam using a wedged optical flat

Cited by 43 publications

References 19 publications

Determining Vortex-Beam Superpositions by Shear Interferometry

Determining Vortex-Beam Superpositions by Shear Interferometry

Measuring the orbital angular momentum spectrum with a single point detector

Tunable Liquid Crystal Twisted‐Planar Fresnel Lens for Vortex Topology Determination

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