Vortex Beams Research Articles

Three transmission properties of perfect vortex beam

Three transmission properties of perfect vortex beam

Competition between turbulence and thermal blooming of coherent vortex beam array propagating in non-Kolmogorov marine atmosphere

Competition between turbulence and thermal blooming of coherent vortex beam array propagating in non-Kolmogorov marine atmosphere

Perfect vortex beams generation based on reflective geometric phase metasurfaces

Perfect vortex beam (PVB) is a propagating light field with radial intensity distribution independent of topological charge and carrying orbital angular momentum (OAM). PVBs can be generated through the Fourier transformation of a Bessel-Gaussian (BG) beam, which traditionally requires a precisely aligned optical setup consisting of a spiral phase plate, a conical lens, and a Fourier lens. However, such traditional schemes are usually bulky and unstable. Here, we have utilized a method that differs from conventional approaches, employing metasurfaces designed as planar Pancharatnam-Berry (PB) phase elements to substitute for all the required components. Unlike traditional methods based on reflective or refractive elements, metasurface elements can significantly reduce the system's footprint. Because the use of metallic metasurfaces allows for a more flattened design plane, in this paper, we have demonstrated the generation of PVB within the 8 GHz microwave frequency band based on a single-layer metallic metasurface. The metasurface is composed of a square ring metal structure, which can serve as a half wave plate to provide the required geometric phase distribution for incident circularly polarized light to generate PVB. By rigorously optimizing the parameters of the square-ring structures, we have generated vortex beams carrying OAM with different topological charges. These vortex beams exhibit a constant radial intensity distribution, which validates their "perfect" characteristics. In addition, we also extracted the mode purity of different vortex beams, so that the mode states of different vortex beams can be distinguished. These results provide broader value for the application of perfect vortex beams in communication.

A novel multiple-image encryption with multi-petals structured light

The study proposed a novel multiple-image encryption scheme using spatial multiplexing under the illumination of a multi-petals structured light. The security is enhanced through the multi-petals structured light with coherent superposition of several vortex beams with different topological charges. Through the system, an image array is formed behind the sub-petals of the complex structured light. Using Fresnel diffraction, each image is encrypted into the ciphertext by the Fibonacci Lucas transform. The multi-petals structured light with different orbital angular momentum can integrate more system parameters as the additional keys resulting in rich key space with improved security level of the cryptosystem. The feasibility and security of the proposed methods are validated through both numerical simulation and experiments. The research has strong and practical applications for three-dimensional information encryption system.

Micro-displacement measurement of optical interference with two-ring conjugated vortices

In this paper, we propose a two-ring conjugated vortex beam interferometer. The inner ring and outer ring of the vortex beams has different signs and topological charges. When combined, they produce an intricate pattern of interference fringes that resemble a flower petal, featuring both concentric inner and outer rings which rotates with different directions. We use the scale-invariant feature transformation algorithm to find the feature points. Then we use these points to measure the rotation angle of the outer ring relative to the inner ring and calculate the displacement based on it. We realize the measurement of sub-nanometer displacement. The displacement resolution is 0.38° nm−1. It is improved by about 12.55% compared with only the inner ring. The displacement corresponding to the minimum detectable angle of CCD is reduced from 0.080 nm to 0.060 nm. It will be a promising method in precision machining micro-vibration sensing, surface unevenness sensing, and microbial movement sensing and high-precision measurement of micro-displacement.

Bessel–Bessel–Gaussian vortex laser beams

Abstract We obtain and investigate Bessel–Bessel–Gaussian vortex beams (BBG beams) with the complex amplitude being equal to a product of the Gaussian function with two Bessel functions, whose arguments are expressed as complicated radicals including the cylindrical coordinates and a free parameter that defines the shape of the intensity distribution. If this parameter is small, the intensity has the shape of an inhomogeneous ring. For larger values of this parameter, the intensity has the shape of two arcs or ‘crescents’, oriented by their concave sides to each other. The complex amplitude of such beams is derived in explicit form for an arbitrary distance from the waist. We demonstrate that the BBG beams rotate upon propagation anomalously fast: at a distance much shorter than the Rayleigh length, the intensity distribution is already rotated by almost 45°, whereas typically, the rotation angle of vortex Gaussian beams is equal to the Gouy phase. It is also shown that the parameter of the BBG beam allows controlling its topological charge (TC): when the parameter value is positive and increases, the beam TC also increases stepwise by an even number. Besides, we study two other similar vortex BBG beams: either with four local intensity maxima, lying on the Cartesian coordinates axes, or with one intensity maximum with a crescent shape, whose center is on the horizontal axis. The derived three new families of asymmetric vortex laser beams, whose complex amplitude is described by explicit analytical expressions at an arbitrary distance from the waist, extend the variety of laser beams that can be used for manipulating and rotating microparticles, free space data transmission, and in quantum informatics.

Achieving broadband multifunctional modulation of wavefront via terahertz anisotropic metasurface

Vanadium dioxide (VO2) has become a reliable phase change material (PCM) and is increasingly utilized in multifunctional metasurface design. This study introduces designs of bilayer anisotropic VO2meta-atoms in simulation for multifunctional wavefront modulation in the terahertz band. By leveraging the phase change property of VO2 and incident wave polarization, a reconfigurable metasurface composing anisotropic meta-atoms is proposed with four distinct functions. When VO2 is in its insulating state, the metasurface serves as a hologram generator for the x-polarized wave and a focusing reflector for the y-polarized wave. Upon the transition of VO2 into the metallic state, the metasurface functions as a generator of vortex beam for the x-polarized wave, while as an anomalous reflector for the y-polarized wave. The proposed metasurface showcases an outstanding broadband performance, delivering impressive four-channel wavefront modulation within a frequency range of 2.2–3.0 THz. Depending on the compact structure and integrated multi-functionalities, our design may have immense potential across a wide range of terahertz applications, including communication exchange and multiplexing utilization.

Computerized simulation of 2-dimensional phase contrast images using spiral phase plates in neutron interferometry

Abstract We present calculations of interferograms (interference patterns) of one or multiple spiral phase plates that would be observed with a perfect crystal neutron interferometer of Mach–Zehnder type. A spiral phase plate (SPP) in one of the two coherent beam paths produces a twist in the phase front and thus a vortex beam with intrinsic angular momentum, which in the case of neutrons should be observed as a characteristic interference pattern that appears complementary to each other in both detectors behind the interferometer. Adding additional SPPs in one beam path of the interferometer yield interference patterns similar to that of a single SPP but only due to the cumulative step height. All simulated interferograms have been calculated on the basis of dynamical neutron diffraction without any assumption of a neutron orbital angular momentum and show very convincing agreement with experimental results from the literature, see e.g. (C. W. Clark, R. Barankov, M. G. Huber, M. Arif, D. G. Cory, and D. A. Pushin, “Controlling neutron orbital angular momentum,” Nature, vol. 525, pp. 504–506, 2015). In particular, this clarifies, that the cited experiments do not give evidence of the quantization of interactions caused by a twist of the phase front of a neutron wave in the interferometer and thus no evidence for the effect of a neutron orbital angular momentum.

Transfer learning of recognizing orbital angular momentum modes through atmospheric turbulence and oceanic turbulence

The transmission of vortex beam in wireless optical communication is susceptible to atmospheric turbulence (AT) and oceanic turbulence (OT), leading to crosstalk among different modes and posing significant challenges in the recognition of orbital angular momentum (OAM) modes. This study introduces a novel integration of transfer learning with the VGG16 neural network to form a transfer learning method, which is adeptly applied to the recognition of OAM modes between AT and OT speckle images. The model is trained the model with a substantial amount of data from AT speckle dataset, and then test the performance of recognizing OAM modes using OT speckle dataset. The recognition accuracy, precision, recall and F1-score for both 5 OAM modes and 8 OAM modes using the method are studied, with additional exploration into the impact of training with hybrid datasets on the model’s efficacy. The results show that the transfer learning method is effective to recognize OAM modes from speckle images affected by OT. It is observed that training with a mixed dataset fosters a greater degree of similarity between the source domain data and the target domain data, thereby enabling the model to capture intricate features and enhance recognition accuracy. The approach delineated in this paper highlights the versatility of employing transfer learning method for OAM modes recognition across analogous domains, offering a robust solution for effective recognition of OAM modes.

Investigation of the Propagation Characteristics of Double-Ring Perfect Vortex Beams in Atmospheric Turbulence

Investigation of the Propagation Characteristics of Double-Ring Perfect Vortex Beams in Atmospheric Turbulence

Off-Axis X-Ray Vortex Beam Ptychography

Off-Axis X-Ray Vortex Beam Ptychography

Topological Structures of Energy Flow: Poynting Vector Skyrmions.

Topological properties of energy flow of light are fundamentally interesting and may introduce novel physical phenomena associated with directional light scattering and optical trapping. In this Letter, skyrmionlike structures formed by Poynting vectors are unveiled in the focal region of two pairs of counterpropagating cylindrical vector vortex beams in free space. The appearance of local phase singularities, and the distinct traveling and standing wave modes of different field components passing through the focal spot lead to a Néel-Bloch-Néel transition of Poynting vector skyrmion textures along the light propagating direction. By shaping the wave front of the incident beams with patterned amplitudes, the topological invariant of the Poynting vector skyrmions can be further tuned in a prospective area. This work expands the family of optical skyrmions and holds great potential in energy flow associated applications.

LSPR-susceptible metasurface platform for spectrometer-less and AI-empowered diagnostic biomolecule detection

In response to the growing demand for biomolecular diagnostics, metasurface (MS) platforms based on high-Q resonators have demonstrated their capability to detect analytes with smart data processing and image analysis technologies. However, high-Q resonator meta-atom arrays are highly sensitive to the fabrication process and chemical surface functionalization. Thus, spectrum scanning systems are required to monitor the resonant wavelength changes at every step, from fabrication to practical sensing. In this study, we propose an innovative dielectric resonator-independent MS platform that enables spectrometer-less biomolecule detection using artificial intelligence (AI) at a visible wavelength. Functionalizing the focused vortex MS to capture gold nanoparticle (AuNP)-based sandwich immunoassays causes the resulting vortex beam profiles to be significantly affected by the localized surface plasmon resonance (LSPR) occurring between AuNPs and meta-atoms. The convolutional neural network algorithm was carefully trained to accurately classify the AuNP concentration-dependent focused vortex beam, facilitating the determination of the concentration of the targeted diagnostic biomolecule. Successful in situ identification of various biomolecule concentrations was achieved with over 99 % accuracy, indicating the potential of combining an LSPR-susceptible MS platform and AI for continuously tracking various chemical and biological compounds.

Energy-flow-reversing dynamics in vortex beams: OAM-independent propagation and enhanced resilience: erratum

An erratum is given to correct three typographical errors in Optica 11, 531 (2024).OPTIC82334-253610.1364/OPTICA.517474 The corrections do not impact the results and conclusions of the original paper.

Propagation Properties of Partially Coherent Vortex Beams with Twist Phase in Oceanic Turbulence

Propagation Properties of Partially Coherent Vortex Beams with Twist Phase in Oceanic Turbulence

Tailoring an arbitrary large vectorial structured light beam array utilizing the tensor theory of multiplexed polarization holograms

Vectorial structured light beams, characterized by their topological charge and non-uniform polarization distribution, are highly promising beam modes for several applications in different domains of optics and photonics. To harness its potential specifically in optical communication, data encryption, and optical trapping, it is necessary to tailor a multitude of these beams with arbitrary and large topological charge and polarization distribution. However, achieving the above-mentioned requires bulky optical setups that necessitate the superposition of two beams or involve complex material fabrication techniques that can directly generate these beams. In this paper, we report the generation of a large structured light beam array by utilizing multiplexed polarization holograms, computer-generated holography, and azo-carbazole polymer film. We have developed a theoretical framework for double-exposure polarization holography that enables the possibility of tailoring such a vectorial light beam array. Utilizing the developed theory, we showcase the experimental generation of a structured vector beam array of size 8 × 8 with arbitrary topological charges and polarization distribution in 3 mm × 3 mm area of the polymer film. Exploiting the large space bandwidth of the polymer film, we also demonstrate the generation of vector vortex beam arrays with exceptionally large topological charges (l=100). All the above has been experimentally realized by simply illuminating the hologram with a plane Gaussian beam, and no additional optics are needed. This reported method offers huge potential and opens up new possibilities for the utilization of vectorial structured light beams.

A new generalized perspective to establish vortex beams

Vortex beams are powerful primitives for optical operations and communications. We propose general mathematical methods to establish new vortex beams and optimize existing vortex beams. Based on these methods, two new types of vortex beams are demonstrated theoretically and experimentally. The propagation characteristics of these vortex beams can be finely controlled through specific parameters. Additionally, influences of periodic discontinuities and orbital angular momentum of two vortex beams are analyzed. The innovative concept of beam modulation and the introduction of new vortex beams in this paper indicate significant potential for applications in particle trapping, spatial communication, and quantum computation.

High-dimensional signal encoding and decoding method based on multi-ring perfect vortex beam

High-dimensional signal encoding and decoding method based on multi-ring perfect vortex beam

Multidimensional Manipulation and Encoding of Versatile Vector Vortex Beams Empowered by Phase-Change Metasurfaces

Multidimensional Manipulation and Encoding of Versatile Vector Vortex Beams Empowered by Phase-Change Metasurfaces

Topological‐Charge‐Dependent Dichroism and Birefringence of Optical Vortices

AbstractMaterial anisotropy and chirality produce polarization‐dependent light‐matter interactions. Absorption leads to linear and circular dichroism, whereas elastic forward scattering produces linear and circular birefringence. Here a form of dichroism and birefringence is highlighted whereby generic anisotropic media display locally different absorption and scattering of a focused vortex beam that depends upon the sign of the topological charge . The light‐matter interactions described in this work manifest purely through dominant electric‐dipole coupling mechanisms and depend on the paraxial parameter to first‐order. Previous topological‐charge‐dependent light‐matter interactions require the significantly weaker higher‐order multipole moments and are proportional to the paraxial parameter to second‐order. The result represents a method of probing the nano‐optics of advanced materials and the topological properties of structured light.