Perfect Vortex Beam Research Articles

Recovery of encoded information from conjugate superimposed perfect vortex beams in scattering environments

Recovery of encoded information from conjugate superimposed perfect vortex beams in scattering environments

Compact multi-ring perfect vortex beam generator fabricated by laser direct writing

Perfect vortex beams (PVBs) have received much attention in recent years since the annular intensity distributions are independent of the topological charge (TC). However, the cost-effective preparation of micrometer-scale monolithic devices capable of generating multiple PVBs through a simple approach remains a significant challenge. In this work, a design of double-ring perfect spiral phase plates (DPSPPs) is presented for the generation of PVBs at two distinct locations along the radial direction. The respective radii and spacing of the double-ring PVBs can be tuned by changing the control parameters. The proposed DPSPPs are fabricated by the flexible femtosecond laser direct writing (FsDLW) technique. The experimentally generated double-ring vortex beams with different TCs possess an almost constant radius, which is consistent with the characteristics of PVBs. Furthermore, the double-ring PVBs with different fractional and trigonometric function TCs and the multi-ring PVB are also demonstrated. The design and fabrication methods are expected to facilitate the miniaturization of the applications of PVBs in optical manipulation, optical communication, and high-capacity information storage.

Three transmission properties of perfect vortex beam

Three transmission properties of perfect vortex beam

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.

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

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

Multi‐Concentric Generalized Perfect Vortex Beams by Hybrid Phase Metasurfaces

AbstractMetasurface‐based vortex beams are expected to overcome the current communication challenges of massive data and limited bandwidth by their theoretical infinite and mutually orthogonal states. However, limited by the spatial extension of array vortices, only finite orbital angular momentum (OAM) eigenstates are available, of which the expansion will boost the bandwidth toward an inexhaustible stage. In this manuscript, multi‐concentric generalized perfect vortex beams (G‐PVBs) are experimentally generated by the fabricated hybrid phase metasurfaces integrating generalized focusing phases and circular domain function into vortex phases. Diverse vortex shapes and helical lobes within beam patterns and spiral interferograms are both arranged in a non‐overlapping concentric manner instead of spatial arrays, respectively, breaking the limitation of symmetric shape while avoiding inter‐modal cross‐talk. The vortex shape, topological charge and vortex number are decoupled mutually in orthogonal polarization states, realizing both space and polarization multiplexing. Furthermore, shaped into anomalous profiles with asymmetric states of polarization, multi‐concentric vector G‐PVBs are experimentally generated to transmit parallelly stable order information with high robustness in turbulence environments. The proposed multi‐concentric G‐PVBs simultaneously expanded the novel vortex dimension by anomalous shapes and information channels of multi‐concentric OAM modes, providing potential application in high‐capacity vortex optical communication and information encryption.

Interference of high-order perfect optical vortex beams

We investigate the interference of high-order perfect optical vortex (POV) beams with different topological charges. Through numerical simulations, we reveal a remarkable phenomenon: keeping the beam width, and beam radius fixed while changing the topological charge, the splitting of the composite POV beam into two distinct individual perfect vortices occurs exactly at the same inter-axial separation. The observed interference pattern exhibits pronounced sensitivity to factors such as axial separation, phase shift, beam radius, and topological charges of the constituent beams. Notably, our findings are contrasted with the interference of high-order Laguerre-Gauss (LG) beams, highlighting that the splitting of composite vortices into their individual components is more rapid in the case of LG beams. We also investigate the evolution of the interference pattern for both POV, and LG beams along the propagation direction in free-space. Our research provides significant insights into the distinct interference properties of high-order POV beams, presenting potential applications in the fields of optical manipulation and communication systems.

Exploring the origin of stronger survival of polarized vortex beams through scattering media

Laguerre–Gaussian (LG) beams carrying orbital angular momentum (OAM) have shown promise in deep tissue imaging, medical diagnostics, and optical communication due to their robust propagation properties through scattering media. The insight on the mechanism for stronger survival of OAM carrying beam in tissue-like turbid media is expected to contribute towards a better understanding of light transport in the presence of scattering, as well as guide optimization of the intensity, phase, and polarization structure of light for use in biomedical applications like in tissue imaging. We examine the scattering properties by studying the propagation of polarized vortex beams transmitted through tissue-like turbid scattering media. We demonstrate that the intensity profile has a much more profound effect on depolarization than the phase profile for LG beams. Our results indicate that the observed stronger propagation for the higher-order LG beams is due to a higher anisotropy factor g, as seen by the incident beam. We have performed the degree of polarization measurements for the forward scattered light in the case of both LG beams and perfect vortex beams with varying topological charges. A comparison between the observed depolarization trends for the two classes of OAM-carrying beams suggests that the robust scattering properties of the LG beams originate from the intensity profile while the phase profile does not seem to play a major role in the stronger survival of OAM-carrying beam in turbid media.

Influence of orbital angular momentum of light on random spin-split modes in disordered anisotropic optical media

Spin–orbit interaction of light in a disordered anisotropic medium is known to yield spin split modes in the momentum domain because of the random spatial gradient of the geometric phase of light. Here, we have studied the statistics of such spin-split modes for beams carrying intrinsic orbital angular momentum through the quantification of momentum domain entropy and investigated its dependence on various beam parameters. The influence of the spatial structure of the beam and the phase vortex on the statistics of the spin split modes were separately investigated using input Laguerre–Gaussian and Perfect Vortex beams passing through a disordered anisotropic medium with controlled input disorder parameter, which was realized by modulating the pixels of a liquid crystal-based spatial light modulator. The results of systematic investigations on the impact of beam waist, spot size and topological charge of the vortex beam show that the influence of the spot size on the emergence of the random spin split modes is much more significant as compared to the other beam parameters.

Wigner distribution and entropy of partially coherent light generated by perfect optical vortices.

We developed analytical expressions for the Wigner distribution function of partially coherent fields generated by the scattering of beams with a particular phase structure, namely perfect optical vortex beams. In addition, we provide the modal decomposition of the field correlations and evaluate the evolution of Shannon entropy associated with the partially coherent field.

Rotation of a Tricomi–Gaussian beam and its focusing characteristics through a thin lens system

The rotation behaviors of an asymmetric Tricomi–Gaussian beam (aTGB) propagating in free space and through a thin lens system are mainly investigated. The focusing characteristics of TGB with symmetric and asymmetric modes propagating through a thin lens system are also presented. Influences of complex constants α and β, the topological charge n, and the lens focal length f on the field distributions of TGB are studied thoroughly. The results indicate that when a symmetric TGB propagates through a thin lens system, a perfect vortex beam could be generated at the lens focal plane. TGB undergoes two focusing processes through the thin lens system, and the peak intensities at two focal planes, the rotation, and the focal characteristics of TGB can be manipulated by α,β,n, and f. Moreover, f has more significant effects on the focal depths of two foci and the self-focusing focal length than α,β, and n.

Dual perfect vectorial vortex beam generation with a single spin-multiplexed metasurface

Perfect optical vortex beams (POVBs) carrying orbital angular momentum (OAM) possess annular intensity profiles that are independent of the topological charge. Unlike POVBs, perfect vectorial vortex beams (PVVBs) not only carry orbital angular momentum but also exhibit spin angular momentum (SAM). By incorporating a Dammann vortex grating (DVG) on an all-dielectric metasurface, we demonstrate an approach to create a pair of PVVBs on a hybrid-order Poincaré sphere. Benefiting flexible phase modulation, by engineering the DVG and changing the input-beam state we are able to freely tailor the topological OAM and polarization eigenstates of the output PVVBs. This work demonstrates a versatile flat-optics platform for high-quality PVVB generation and may pave the way for applications in optical communication and quantum information processing.

Double-Ring perfect vectorial vortex beams distribution regulation

Perfect vector beams with radius independent of topological charges have garnered significant interest owing to their unique capabilities in optical manipulation, microscopy imaging, and laser micro-machining. However, their polarization state is limited to four modes, restricting their information capacity and re-usability. To address this, we introduce double-ring perfect vectorial vortex beams that leverage the axicon phase to theoretically generate double-ring structures through a Fourier transform. By applying a transformation matrix and introducing a cross phase, we can manipulate the beam distribution. This approach is expected to enhance for development of particle capture and optical communications.

Perfect vortex beams with periodic coherence properties

Partially coherent perfect vortex beams with periodic coherence properties, namely, optical coherence perfect vortex lattices (OCPVLs), are proposed in this letter. Rhombus-, spiral-, and circle-shaped OCPVLs were investigated in detail both theoretically and experimentally through the manipulation of the coherent structures. Manipulating the coherence width yielded unique advantages, such as maintaining uniformity over a longer distance, more efficient optical trapping, and high-capacity free-space optical communications. OCPVLs with such advantages hold outstanding potential for applications in multi-particle trapping and manipulation.

Flexible Modulation of Perfect Vortex Beams by Combining Coherent Beams

Flexible Modulation of Perfect Vortex Beams by Combining Coherent Beams

High-performance switchable perfect composite vortex beam generator based on halogen perovskite metasurfaces

We propose and realize a novel high-performance switchable perfect composite vortex beam (PCVB). We introduce the concept of composite vortex beam and then present a design for a PCVB generator based on halogen perovskite metasurfaces, which can convert circularly polarized light into a parametrically tunable PCVB using a single halogen perovskite fully dielectric metasurface. The PCVB exhibits a constant toroidal intensity distribution and the ability to superimpose different topological charges. We demonstrate the high feasibility of this design to generate PCVBs with different operating wavelengths, topological charges, and numerical apertures. Additionally, we explore the practical application potential of our design by demonstrating reversible exchange between three halogen perovskite metasurfaces using chemical vapor deposition. This exchange leads to corresponding imaging effects at specific wavelengths. The proposed generator has significant application prospects in optical communication encryption, optical data storage, and optical tweezers.

Propagation of perfect vortex beam beyond the focal depth

Perfect vortex beam (PVB) has emerged as a promising candidate in the field of optical communication, which is currently limited due to its realization only at the focal depth of Fourier lens. The present letter reports devising of a unique technique for the propagation of PVB beyond this point and has been verified experimentally, inside laboratory, up to a distance of 5 m. The properties of PVBs, observed at the focus of the Fourier lens, were well preserved in the propagated beams. This proposed approach ensures preserving of the invariance of the annular radius of propagating PVBs, carrying different orbital angular momentum, which has emerged as a unique property for their potential application in the fields of communication, particle trapping, and micro-machining.

Generation of elliptical perfect optical vortex beams and their propagation in free-space.

We investigate the generation of an elliptical perfect optical vortex (EPOV) beam through the optical Fourier transformation of an elliptical Bessel-Gaussian beam and derive an analytical expression for its complex field amplitude. Our analysis includes the examination of the beam's propagation in free-space and the influence of topological charge on its transmission. The EPOV beam's propagation in free-space can be categorized into non-diffracting and diffracting stages. During the non-diffracting stage, the beam intensity and profile size are effectively preserved over a short transmission distance. Subsequently, in the diffracting stage, the beam profile initially contracts and then expands with a change in the beam intensity. Notably, the impact of topological charge on the beam intensity and profile size varies across different stages of propagation. We compare our results with those of the circular perfect optical vortex beam propagating in free-space, observing that the EPOV beam exhibits non-diffracting behavior for short propagation distances compared to its circular counterpart. The signature of the focusing behavior of the EPOV beam is observed at a relatively small propagation distance compared to the circular case.

Rotational Vortex Metasurface Arrays Enabling Tunable Perfect Petal‐Shaped Beam Emissions

AbstractActively tunable petal‐shaped pattern emissions have been successfully demonstrated by the cascade of two innovative rotational vortex metasurface arrays (RVMAs). To ensure accurate cascade, each RVMA comprises a central unit with the capability to converge light, surrounded by six units designed for emitting converging vortex beams (VBs) and converging perfect vortex beams (PVBs) with topological numbers (TCs) of 3, 6, and 9, respectively. Notably, although the number of spiral branches and the diameters of the VB and PVB are determined in accordance with specific design TCs, the diameters and the number of petals for the petal‐shaped beam emissions are actively adjusted through the rotation of the RVMAs. Interestingly, the superimposition of these VBs, PVBs, or both, consistently generates petal‐shaped beams with various petal numbers and diameters, highlighting the remarkable versatility of the approach. To demonstrate the proposed concept across wavelengths, indicating its broadband operation capability, RVMA performance in the visible spectrum is thoroughly investigated, ranging from 450 to 600 nm. The tunability of the cascade of RVMAs for petal‐shaped emissions featuring diverse diameters and petal numbers has been validated at visible wavelengths, affirming the broad capabilities of the concept presented in this study.