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Photonics
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Light Focusing and Optical Vortices
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Light Focusing and Optical Vortices

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Lasers, Light Sources and Sensors".

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 12701

Special Issue Editor

Dr. Elena Kozlova

E-Mail Website1 Website2
Guest Editor
1. Department of Technical Cybernetics, Samara National Research University, 443086 Samara, Russia
2. Laser Measurement Laboratory, IPSI RAS - Branch of the FSRC «Crystallography and Photonics» RAS, 443001 Samara, Russia
Interests: diffractive optics; singular optics; femtosecond optics; numerical simulations, machine learning
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Solving a problem that is as fundamental as controlling the state of light is a one of the most important areas of study in modern optics and nanophotonics. To achieve this goal, it is essential to understand the physical effects that arise during the propagation of laser beams, including during their focusing, as well as the possibility of predicting these effects. This is possible by developing a theory which describes the characteristics of laser light. Singular optics, which studies vortex optical beams, can be called upon to answer these questions. 

Optical vortices are widespread in modern science. The energy in these beams propagates in a spiral in such a way that a "funnel" is formed, which is similar to an air vortex (tornado). Optical vortices were named as such for this reason. The worldwide scientific community is highly involved in the investigation of the formation, propagation, focusing, and detection of optical vortices. Over the past three decades, significant fundamental studies on vortex beams have been carried out, which presented new beam types and optical phenomena in vortex beams. Experimental research has been devoted to different approaches and technologies for the generation of vortex beams and the measurement of orbital angular momentum.

Vortex beams have become one of the most important light sources today because each photon in a vortex beam can carry orbital angular momentum. Therefore, vortex laser beams have been applied in a fairly wide range of fields and have caused the rapid development of optical technologies. They are primarily used to capture and rotate nanoparticles in a circle in the plane of a beam cross section. This property of optical vortices became the basis for the creation of optical tweezers, which made it possible to investigate tiny and complexly organized objects such as, for example, DNA molecules. Optical vortices are also used in optical communications, in quantum computing, in modulation nanolithography and cryptography, etc. In addition to optical vortex beams, some other vortices, such as  electron vortex beams, neutron atom vortex beams, plasmonic vortices, and radio vortices, can lead to new applications in science and technology.

This Special Issue aims to present state-of-the-art articles regarding both theoretical and experimental studies on the generation, propagation, focusing and measurement of light beams and applications of structured beams. Topics include, but are not limited to:

  • The design, simulation, and manufacturing of optical devices for light focusing (metasurfaces, zone plates, plasmonic lenses, etc.);
  • Properties of tightly focused light;
  • Photonic nanojet;
  • Light bullet;
  • Overcoming the diffraction limit;
  • Applications of tightly focused light;
  • Singular optics;
  • The generation of optical vortices;
  • Vortex dynamics;
  • Partially coherent vortex beams;
  • Fractional vortex beams;
  • Plasmonics vortices;
  • Cylindrical vector beams;
  • Vector vortex beams;
  • Orbital angular momentum;
  • Spin orbital conversion;
  • Applications of vortex beams.

Dr. Elena Kozlova
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • the design, simulation, and manufacturing of optical devices for light focusing (metasurfaces, zone plates, plasmonic lenses, etc.)
  • properties of tightly focused light
  • photonic nanojet
  • light bullet
  • overcoming the diffraction limit
  • applications of tightly focused light
  • singular optics
  • the generation of optical vortices
  • vortex dynamics
  • partially coherent vortex beams
  • fractional vortex beams
  • plasmonics vortices
  • cylindrical vector beams
  • vector vortex beams
  • orbital angular momentum
  • spin orbital conversion
  • applications of vortex beams

Published Papers (10 papers)

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Research

14 pages, 5257 KiB  
Article
Simple Method of Light Field Calculation for Shaping of 3D Light Curves
by Svetlana N. Khonina, Alexey P. Porfirev, Sergey G. Volotovskiy, Andrey V. Ustinov and Sergey V. Karpeev
Photonics 2023, 10(8), 941; https://doi.org/10.3390/photonics10080941 - 17 Aug 2023
Viewed by 1010
Abstract
We propose a method for generating three-dimensional light fields with given intensity and phase distributions using purely phase transmission functions. The method is based on a generalization of the well-known approach to the design of diffractive optical elements that focus an incident laser [...] Read more.
We propose a method for generating three-dimensional light fields with given intensity and phase distributions using purely phase transmission functions. The method is based on a generalization of the well-known approach to the design of diffractive optical elements that focus an incident laser beam into an array of light spots in space. To calculate purely phase transmission functions, we use amplitude encoding, which made it possible to implement the designed elements using a single spatial light modulator. The generation of light beams in the form of rings, spirals, Lissajous figures, and multi-petal “rose” distributions uniformly elongated along the optical axis in the required segment is demonstrated. It is also possible to control the three-dimensional structure of the intensity and phase of the shaped light fields along the propagation axis. The experimentally generated intensity distributions are in good agreement with the numerically obtained results and show high potential for the application of the proposed method in laser manipulation with nano- and microparticles, as well as in laser material processing. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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13 pages, 2459 KiB  
Communication
Nonparaxial Focusing of Partially Coherent Gaussian Schell-Model and Bessel-Correlated Beams in Free Space
by Nikolai I. Petrov
Photonics 2023, 10(7), 857; https://doi.org/10.3390/photonics10070857 - 24 Jul 2023
Cited by 1 | Viewed by 686
Abstract
The nonparaxial focusing of partially coherent beams in free space has been studied using the coherent-state and coherent-mode decomposition methods. Analytical expressions for the width and angular divergence of partially coherent Gaussian Schell-model (GSM) beams have been obtained using the coherent-state method. It [...] Read more.
The nonparaxial focusing of partially coherent beams in free space has been studied using the coherent-state and coherent-mode decomposition methods. Analytical expressions for the width and angular divergence of partially coherent Gaussian Schell-model (GSM) beams have been obtained using the coherent-state method. It has been shown that the focusing plane is shifted in the opposite axial direction compared to the geometric focusing plane. The influence of the nonparaxiality and spatial coherence of Bessel-correlated vortex beams on the intensity distribution and displacement of the focus plane has been analyzed. It has been shown that the shift of the focus plane increases with a decrease in the coherence radius of the source. A smaller diffraction spread has been shown for partially coherent Bessel-correlated beams compared to GSM beams. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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12 pages, 4891 KiB  
Article
Multi-User Nonlinear Optical Cryptosystem Based on Polar Decomposition and Fractional Vortex Speckle Patterns
by Vinny Cris Mandapati, Harsh Vardhan, Shashi Prabhakar, Sakshi, Ravi Kumar, Salla Gangi Reddy, Ravindra P. Singh and Kehar Singh
Photonics 2023, 10(5), 561; https://doi.org/10.3390/photonics10050561 - 11 May 2023
Cited by 5 | Viewed by 1140
Abstract
In this paper, we propose a new multiuser nonlinear optical cryptosystem using fractional-order vortex speckle (FOVS) patterns as security keys. In conventional optical cryptosystems, mostly random phase masks are used as the security keys which are prone to various attacks such as brute [...] Read more.
In this paper, we propose a new multiuser nonlinear optical cryptosystem using fractional-order vortex speckle (FOVS) patterns as security keys. In conventional optical cryptosystems, mostly random phase masks are used as the security keys which are prone to various attacks such as brute force attack. In the current study, the FOVSs are generated optically by the scattering of the fractional-order vortex beam, known for azimuthal phase and helical wavefronts, through a ground glass diffuser. FOVSs have a remarkable property that makes them almost impossible to replicate. In the input plane, the amplitude image is first phase encoded and then modulated with the FOVS phase mask to obtain the complex image. This complex image is further processed to obtain the encrypted image using the proposed method. Two private security keys are obtained through polar decomposition which enables the multi-user capability in the cryptosystem. The robustness of the proposed method is tested against existing attacks such as the contamination attack and known-plaintext attack. Numerical simulations confirm the validity and feasibility of the proposed method. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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7 pages, 10525 KiB  
Communication
Near-Field Evolution of Optical Vortices and Their Spatial Ordering behind a Fork-Shaped Grating
by Denis A. Ikonnikov, Sergey A. Myslivets, Vasily G. Arkhipkin and Andrey M. Vyunishev
Photonics 2023, 10(4), 469; https://doi.org/10.3390/photonics10040469 - 20 Apr 2023
Cited by 3 | Viewed by 1006
Abstract
Fork-shaped gratings are periodic structures containing a spatial dislocation known to be used for the production of optical vortices in a far field. Spatial overlapping of diffraction orders in a near field results in complex spatial evolution of optical vortices. In this paper, [...] Read more.
Fork-shaped gratings are periodic structures containing a spatial dislocation known to be used for the production of optical vortices in a far field. Spatial overlapping of diffraction orders in a near field results in complex spatial evolution of optical vortices. In this paper, we report the results of near-field diffraction on fork-shaped gratings with different topological charges and analyze the evolution of specific optical vortices during propagation. Optical vortices have been shown to form two-dimensional well-ordered spatial configurations in specific transverse planes. The locus of points of optical singularities has been shown to form two helical lines twisted around the ±1 diffraction order directions. Our results demonstrate that the spatial behaviour of optical vortices is in close connection with the spatial ordering arising from the Talbot effect. The quantity of optical vortices demonstrates complex spatial dynamics, which includes spatial oscillations and decreasing along the propagation direction. These results provide a foundation towards a deeper understanding of near-field singular optics phenomena. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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10 pages, 3602 KiB  
Communication
Computer Simulation of Multichannel Beam Focusing System in Turbulent Atmosphere
by Petr Konyaev and Vladimir Lukin
Photonics 2023, 10(4), 431; https://doi.org/10.3390/photonics10040431 - 11 Apr 2023
Cited by 1 | Viewed by 1041
Abstract
The results of a computer simulation of laser beams focused by a combined multichannel array system in the atmosphere are presented. Beam propagation on atmospheric paths is considered taking into account the influence of turbulence and time-dependent thermal blooming interactions. The increase in [...] Read more.
The results of a computer simulation of laser beams focused by a combined multichannel array system in the atmosphere are presented. Beam propagation on atmospheric paths is considered taking into account the influence of turbulence and time-dependent thermal blooming interactions. The increase in the maximum intensity of the focal spot due to the optimization of the initial power density of the emitting aperture is estimated. It is shown that the scaling of the optimal initial power in multichannel arrays preserves the proportional dependence of the maximum intensity in focus with an increase in the number of channels. For wave-optics simulation, custom made software was developed based on the split-step method and modified for parallel algorithms using the functions of the Intel ® Math Kernel Library. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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8 pages, 3517 KiB  
Communication
Plasmonic Generation of Spatiotemporal Optical Vortices
by Artem I. Kashapov, Evgeni A. Bezus, Dmitry A. Bykov and Leonid L. Doskolovich
Photonics 2023, 10(2), 109; https://doi.org/10.3390/photonics10020109 - 20 Jan 2023
Cited by 6 | Viewed by 1484
Abstract
We investigate the transformation of spatiotemporal optical signals using the Kretschmann configuration with an additional dielectric layer, which can be referred to as the “generalized Kretschmann setup”. We demonstrate that in the considered structure, it is possible to achieve the condition of generating [...] Read more.
We investigate the transformation of spatiotemporal optical signals using the Kretschmann configuration with an additional dielectric layer, which can be referred to as the “generalized Kretschmann setup”. We demonstrate that in the considered structure, it is possible to achieve the condition of generating a reflected optical pulse containing a spatiotemporal optical vortex, which appears to be impossible in the conventional Kretschmann configuration. High-quality generation of spatiotemporal optical vortices using the investigated structure was confirmed by the results of rigorous numerical simulations. The obtained results are promising for applications in analog optical computing and optical information processing systems. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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12 pages, 8994 KiB  
Article
Flat-Top Focal Spot and Polarization Conversion Obtained in Tightly Focused Circularly Polarized Light
by Sergey S. Stafeev, Vladislav D. Zaitsev and Victor V. Kotlyar
Photonics 2023, 10(1), 32; https://doi.org/10.3390/photonics10010032 - 28 Dec 2022
Viewed by 1232
Abstract
In this paper, using the Richards–Wolf equations, the focusing of circularly polarized light with flat diffractive lenses is considered. It is shown that, as the numerical aperture (NA) of the lens increases, the size of the focal spot first decreases and then begins [...] Read more.
In this paper, using the Richards–Wolf equations, the focusing of circularly polarized light with flat diffractive lenses is considered. It is shown that, as the numerical aperture (NA) of the lens increases, the size of the focal spot first decreases and then begins to grow. The minimum focal spot is observed at NA = 0.96 (FWHM = 0.55 λ). With a further increase in the numerical aperture of the lens, the growth of the longitudinal component leads to an increase in the size of the focal spot. When a flat diffractive lens is replaced by an aplanatic lens, the size of the focal spot decreases monotonically as the numerical aperture of the lens increases. In this case, the minimum focal spot will be FWHM = 0.58 λ and, with a larger numerical aperture, NA = 0.99. We also reveal that, at the focus of a circularly polarized laser beam, different radius circles are observed to be centered on the optical axis, where polarization vectors rotate oppositely (clockwise and anticlockwise). This phenomenon of radius-dependent ‘spin’ separation may be interpreted as a manifestation of the radial spin Hall effect at the focus. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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16 pages, 12986 KiB  
Article
Astigmatic-Invariant Structured Singular Beams
by Alexander Volyar, Eugeny Abramochkin, Yana Akimova and Mikhail Bretsko
Photonics 2022, 9(11), 842; https://doi.org/10.3390/photonics9110842 - 08 Nov 2022
Cited by 7 | Viewed by 1101
Abstract
We investigate the transformation of structured Laguerre–Gaussian (sLG) beams after passing through a cylindrical lens. The resulting beam, ab astigmatic structured Laguerre–Gaussian (asLG) beam, depends on quantum numbers (n,ℓ) and three parameters. Two of them are control parameters of [...] Read more.
We investigate the transformation of structured Laguerre–Gaussian (sLG) beams after passing through a cylindrical lens. The resulting beam, ab astigmatic structured Laguerre–Gaussian (asLG) beam, depends on quantum numbers (n,ℓ) and three parameters. Two of them are control parameters of the initial sLG beam, the amplitude ϵ and phase θ. The third one is the ratio of the Rayleigh length z0 and the focal length f of the cylindrical lens. It was theoretically revealed and experimentally confirmed that the asLG beam keeps the intensity shape of the initial sLG beam when the parameters satisfy simple conditions: ϵ is unity and the tangent of the phase parameter θ/2 is equal to the above ratio. We also found sharp bursts and dips of the orbital angular momentum (OAM) in the asLG beams in the vicinity of the point where the OAM turns to zero. The heights and depths of these bursts and dips significantly exceed the OAM maximum and minimum values of the initial sLG beam and are controlled by the radial number n. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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11 pages, 6770 KiB  
Article
Measuring of Transverse Energy Flows in a Focus of an Aluminum Lens
by Elena Kozlova, Sergey Stafeev, Sergey Fomchenkov, Vladimir Podlipnov, Alexandra Savelyeva and Victor Kotlyar
Photonics 2022, 9(8), 592; https://doi.org/10.3390/photonics9080592 - 20 Aug 2022
Cited by 3 | Viewed by 1177
Abstract
In this study, we theoretically and experimentally investigate the propagation of a second-order cylindrical vector beam through an aluminum lens which forms a tight focus at the distance of the wavelength. Simulation by the finite-difference time-domain method and the Richards–Wolf formulae produces light [...] Read more.
In this study, we theoretically and experimentally investigate the propagation of a second-order cylindrical vector beam through an aluminum lens which forms a tight focus at the distance of the wavelength. Simulation by the finite-difference time-domain method and the Richards–Wolf formulae produces light field distributions which coincide with experimental measurements provided with scanning near-field optical microscopy. We demonstrate that a pyramidal metallized cantilever with a hole is more sensitive to the transversal component of intensity than to the full intensity or to the Umov–Poynting vector in areas of reverse energy flow. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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14 pages, 5180 KiB  
Article
Geometric Progression of Optical Vortices
by Victor Kotlyar, Alexey Kovalev, Elena Kozlova, Alexandra Savelyeva and Sergey Stafeev
Photonics 2022, 9(6), 407; https://doi.org/10.3390/photonics9060407 - 09 Jun 2022
Cited by 3 | Viewed by 1644
Abstract
We study coaxial superpositions of Gaussian optical vortices described by a geometric progression. The topological charge (TC) is obtained for all variants of such superpositions. The TC can be either integer or half-integer in the initial plane. However, it always remains integer when [...] Read more.
We study coaxial superpositions of Gaussian optical vortices described by a geometric progression. The topological charge (TC) is obtained for all variants of such superpositions. The TC can be either integer or half-integer in the initial plane. However, it always remains integer when the light field propagates in free space. In the general case, the geometric progression of optical vortices (GPOV) has three integer parameters and one real parameter, values which define its TC. The GPOV does not conserve its intensity structure during propagation in free space. However, the beam can have the intensity lobes whose number is equal to one of the family parameters. If the real GPOV parameter is equal to one, then all angular harmonics in the superposition are of the same energy. In this case, the TC of the superposition is equal to the order of the average angular harmonic in the progression. Thus, if the first angular harmonic in the progression has the TC of k and the last harmonic has the TC of n, then the TC of the entire superposition in the initial plane is equal to (n + k)/2, but the TC is equal to n during propagation. The experimental results on generating of the GPOVs by a spatial light modulator are in a good agreement with the simulation results. Full article
(This article belongs to the Special Issue Light Focusing and Optical Vortices)
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