Vector Vortex Beams Research Articles

High Energy Singular Beams Generation From a Dissipative Soliton Resonance Raman Fiber Laser

We demonstrated the high energy 1.65 μm singular beam generation from a dissipative soliton resonance (DSR) all-fiber Raman laser experimentally. By utilizing advantages of the high nonlinearity and home-made mode-selective coupler (MSC), different DSR pulsed singular beams, including cylindrical vector beam (CVB) and vortex beams (VB), have been generated experimentally. The maximum pulse energy can be enhanced up to 698.19 nJ with high signal to noise ratio of 80 dB by optimizing the intra-cavity nonlinearity. Our research may provide a new method to generate high energy pulsed singular beams with a flexible operation wavelength.

Generation of optical chirality by the tightly focused higher-order Poincaré sphere vector vortex beams

We derive the analytical expressions of the electric and magnetic field vectors as well as optical chirality density of tightly focused higher-order Poincaré sphere (HOPS) vector vortex beams based on the Richards-Wolf vector diffraction theory. The optical chirality density induced by the tightly focused HOPS vector vortex beams is systematically explored, and its roles with respect to ellipticity, handedness, orientation, polarization topological charge (PTC), and vortex topological charge (VTC) are deeply revealed. The research results show that apart from the orientation of the polarization ellipse, other parameters of the input vortex beams have a significant influence on the optical chirality density of the tightly focused fields. It is noteworthy that because of the introduction of vortex phase, the optical chirality density of linearly polarized light before being focused carrying no spin angular momentum (SAM) is no longer zero. The change of the sign of VTC and PTC has an important effect on the sign of optical chirality density of the tightly focused fields, whereas its spatial distribution and magnitude mainly arises from the change of the value of VTC and PTC. Furthermore, for the non-linearly polarized input beam, due to the interplay of the orbital angular momentum (OAM) and SAM, the sign and value of VTC and ellipticity have an important influence not only on the sign, but also on the spatial distribution and magnitude of the optical chirality density. These research results may provide new insights into the chiral light–matter​ interactions and find potential applications in chiral particle trapping, manipulation, and so on.

Energy Backflow in Tightly Focused Fractional Order Vector Vortex Beams with Binary Topological Charges

Using the Richards–Wolf diffraction integral, the longitudinal energy evolution on the focal plane of the fractional order vector vortex (FOVV) beams was studied. These beams possessed a vortex topological charge n and a polarization topological charge m, and were subjected to tight focusing through a larger numerical aperture. Our investigation revealed the existence of backflow energy when the binary topological charges n and m satisfied the conditions of n + m = 2 or n − m = −2. The component circularly polarized vortex beams of e−i2ϕe^+ (i.e., the minus second-order vortex right circularly polarized beam) and ei2ϕe^− (i.e., the second-order vortex left circularly polarized beam) played significant roles in the generation of reverse energy flux at the focal region. For FOVV beams with binary topological charges n and m, whose sum and difference were integers, the longitudinal energy on the focal plane exhibited axial symmetry. If the sum or the difference of the topological charges n and m was not an integer, the axisymmetric longitudinal energy on the focal plane was disrupted.

Trapping of Rayleigh Spheroidal Particles Using Tightly Focused Higher-Order Vector Vortex Beams

Considering the advantages of higher-order vector vortex beams (HOVVBs) with their diverse intensity distribution of the focal field and adjustable longitudinal field component, we investigated the optical forces and torques on Rayleigh spheroidal particles induced by tightly focused HOVVBs based on the Rayleigh scattering model and dipole approximation. It was found that the maximal optical forces were obtained when the major axis of the Rayleigh spheroidal particles was parallel to the x–y plane. We achieved the three-dimensional stable trapping of Rayleigh spheroidal particles at the focus by using an HOVVB. Further analysis showed that the optical torque caused the major axis of the spheroidal particle to rotate towards the x–y plane, which is conducive to the large-scale stable trapping of Rayleigh spheroidal particles in the two-dimensional plane. Moreover, the optical torque Γx could achieve a maximum of 0.869 pN·nm at φ0 = 90° and 270°, while Γy could achieve a maximum of 0.869 pN·nm at φ0 = 0° and 180° for the case of θ0 = 30°. Our findings provide a clear strategy for extending the degrees of freedom in the control of the beam. We envision a significant role for these results in optical micro-manipulation.

Dynamic control of hybrid grafted perfect vector vortex beams

Perfect vector vortex beams (PVVBs) have attracted considerable interest due to their peculiar optical features. PVVBs are typically generated through the superposition of perfect vortex beams, which suffer from the limited number of topological charges (TCs). Furthermore, dynamic control of PVVBs is desirable and has not been reported. We propose and experimentally demonstrate hybrid grafted perfect vector vortex beams (GPVVBs) and their dynamic control. Hybrid GPVVBs are generated through the superposition of grafted perfect vortex beams with a multifunctional metasurface. The generated hybrid GPVVBs possess spatially variant rates of polarization change due to the involvement of more TCs. Each hybrid GPVVB includes different GPVVBs in the same beam, adding more design flexibility. Moreover, these beams are dynamically controlled with a rotating half waveplate. The generated dynamic GPVVBs may find applications in the fields where dynamic control is in high demand, including optical encryption, dense data communication, and multiple particle manipulation.

Generation of mode-switchable nanosecond pulsed cylindrical vector beams and vortex beams from a Q-switched solid-state laser

We reported and demonstrated a Q-switched solid-state laser for the generation of mode-switchable nanosecond pulsed cylindrical vector beams and vortex beams between different orders. In the cavity, an order-switchable Q-plate, consisted of two Q-plates and two quarter wave plates, was applied to achieve the mode-switch between two different orders by adjusting the angles of quarter wave plates. Besides, two extra quarter wave plates and a Faraday rotator were utilized to realize the intracavitary self-reproducibility of cylindrical vector beams and vortex beams, respectively. The experimental results show that by using two Q-plates of 1st and 3rd orders, the cylindrical vector beams and vortex beams of 2nd and 4th orders can be directly generated from the solid-state laser. For the 2nd order cylindrical vector beam and vortex beam, the slope efficiency, pulse width, and repetition rate are 7.2%, 415 ns, and 227 kHz, respectively. To the best of our knowledge, it is the first time to realize the controlled generation of mode-switchable cylindrical vector beams and vortex beams between two different orders from a solid-state laser.

Phase control scheme of the coherent beam combining system for generating perfect vectorial vortex beams assisted by a Dammann vortex grating.

Based on Dammann vortex grating and adaptive gain stochastic parallel gradient descent algorithm, we theoretically proposed a phase control technology scheme of the coherent beam combining system for generating perfect vectorial vortex beams (VVBs). The simulated results demonstrate that the discrete phase locking for different types of VVBs (including vortex beams, vector beams, and generalized VVBs) can be successfully realized. The intensity distributions, polarization orientation, Pancharatnam phases, and beam widths of different |Hm,n〉 states with the obtained discrete phase distribution further prove that the generated beams are perfect VVBs. Subsequently, the phase aberration residual for different VVBs is evaluated using the normalized phase cosine distance function, and their values range from 0.01 to 0.08, which indicates the obtained discrete phase distribution is close to the ideal phase distribution. In addition, benefitting from the high bandwidth of involved devices in the proposed scheme, the influence of dynamic phase noise can be negligible. The proposed method could be beneficial to realize and switch flexible perfect VVBs in further applications.

Simple experimental realization of optical Hilbert Hotel using scalar and vector fractional vortex beams

Historically, infinity was long considered a vague concept—boundless, endless, larger than the largest—without any quantifiable mathematical foundation. This view changed in the 1800s through the pioneering work of Georg Cantor, who showed that infinite sets follow their own seemingly paradoxical mathematical rules. In 1924, David Hilbert highlighted the strangeness of infinity through a thought experiment now referred to as the Hilbert Hotel paradox, or simply Hilbert’s Hotel. The paradox describes a “fully” occupied imaginary hotel having an infinite number of single-occupancy rooms. The manager can always find a room for new guests by simply shifting current guests to the next highest room, leaving the first room vacant. The investigation of wavefield singularities has uncovered the existence of a direct optical analogy to Hilbert’s thought experiment. Since then, efforts have been made to investigate the properties of Hilbert’s Hotel by controlling the dynamics of phase singularities in “fractional” order optical vortex beams. Here, we have taken such proposals to the next level and experimentally demonstrated Hilbert’s Hotel using both phase and polarization singularities of optical fields. Using a multi-ramped spiral-phase-plate and a supercontinuum source, we generated and controlled fractional order vortex beams for the practical implementation of Hilbert’s Hotel in scalar and vector vortex beams. Using a multi-ramped spiral-phase-plate, we show the possibility for complicated transitions of the generalized Hilbert’s Hotel. The generic experimental scheme illustrates the usefulness of structured beams in visualizing unusual mathematical concepts and also for fractional vector beams driven by fundamental and applied research.

Structured Light Generation Using Angle‐Multiplexed Metasurfaces

AbstractOn the basis of the Jones matrix, independent control over the amplitude and phase of light has been demonstrated by combining several meta‐atoms into the supercell of a metasurface. However, due to the intrinsic limitation of a planar achiral structure, the maximum number of independent, complex elements in one Jones matrix is three, giving rise to up to three‐channel amplitude and phase control. In this work, more Jones matrices corresponding to different angles of incidence are proposed to add, so that the degrees of freedom in the amplitude and phase control can be further increased. The supercell of the designed metasurfaces consists of three dielectric nanoblocks with predefined rotation angles and displacements in the 2D space, which can be inversely determined with the help of the genetic algorithm. Empowered by the ability to realize four‐ or even eight‐channel amplitude and phase control, the generation of multiple structured light, including two independent perfect Poincaré beams, two double‐ring perfect Poincaré beams, two perfect Poincaré beam arrays, and four vector vortex beam arrays, is numerically demonstrated. Such novel designs are expected to benefit the development of modern optical applications, including but not limited to optical communications, quantum information, and signal encryption.

Optical Manipulation of Nanoparticles: A Selective Excitation Approach Using Highly Focused Orbital Angular Momentum Beams

Orbital angular momentum and polarization states of highly focused vector vortex beams can be engineered to selectively excite the desired multipoles in nanoparticles, making them ideal candidates for complex optical applications. A platform based on the generalized Lorenz–Mie theory integrated with the complex source point method is developed to model the interaction of such beams with particles analytically. The existing platform is extended for obtaining the full‐vector electromagnetic fields, outlining the observed effects that adding a substrate brings to the problem space. Despite the cross‐coupling between different multipoles induced by the substrate, it is concluded that the proper choice of beam parameters enables the selective excitation of multipoles even in the critical case of a plasmonic substrate. The proposed formalism is general and allows a multipole study of the optical forces. Selective excitation is exploited to control the imparted optical forces on particles placed on a plasmonic substrate. 3D trapping regions are achievable for highly absorptive and high‐refractive‐index particles. Motion trajectory analyses are performed to demonstrate the trapping stability, concluding that highly focused optical beams, owing to the exceptional selective excitation ability, are suitable candidates for novel optical manipulation applications.

Propagation of noninteger cylindrical vector vortex beams in a gradient-index fiber

The characteristics of two noninteger cylindrical vector vortex beams (NCVVBs) propagating through a radial gradient-index (GRIN) fiber are analyzed on the basis of the generalized Huygens-Fresnel principle. The NCVVBs exhibit periodic and stable transmission characteristics in the radial GRIN fiber. Polarization changes, the presence of spin angular momentum (SAM), and changes in the orbital angular momentum (OAM) of the NCVVBs are observed at the focal plane of the radial GRIN fiber. Spin-orbit interactions of NCVVBs are verified in the radial GRIN fiber for the first time, to the best of our knowledge.

Optically polarized selective transmission of a fractional vector vortex beam by the polarized atoms with external magnetic fields.

We investigate the role of external magnetic fields and linearly polarized pump light, especially when their directions are parallel or vertical, on the propagation of the fractional vector vortex beams (FVVBs) through a polarized atomic system. Herein, the different configurations of external magnetic fields lead to various optically polarized selective transmissions of FVVBs with different fractional topological charge α caused by the polarized atoms, which is theoretically demonstrated by the atomic density matrix visualization analysis and experimentally explored by Cesium atom vapor. Meanwhile, we find that the FVVBs-atom interaction is a vectorial process due to the different optical vector polarized states. In this interaction process, the atomic optically polarized selection property provides potential for the realization of the magnetic compass based on warm atoms. For the FVVBs, due to the rotational asymmetry of the intensity distribution, we can observe some transmitted light spots with unequal energy. Compared with the integer vector vortex beam, it is possible to obtain a more precise magnetic field direction by fitting the different "petal" spots of the FVVBs.

Generation of vector elliptical perfect optical vortices with mixed modes in free space.

Vector vortex beams are widely used because of their anisotropic vortex polarization state and spiral phase. Constructing mixed mode vector vortex beams in free space still requires complex designs and calculations. We propose a method for generating mixed mode vector Elliptical perfect optical vortex (EPOV) arrays in free space by mode extraction and optical pen. It is demonstrated that the long axis and short axis of EPOVs are not limited by the topological charge (TC). Flexible modulation of parameters in the array is achieved, including number, position, ellipticity, ring size, TC, and polarization mode. This approach is simple and effective, it will provide a powerful optical tool for optical tweezers, particle manipulation, and optical communication.

Propagation-induced changes in non-isotropically correlated vector vortex beams

We study the propagation of non-isotropically correlated vector vortex beams (NCVVBs) through an ABCD optical system. The statistical properties, namely, intensity, state of polarization, degree of polarization (DoP), and degree of coherence (DoC) of these beams are investigated. The terminology non-isotropically correlated is used for electromagnetic Gaussian Schell-model beams, that exhibit the distinguishability of spatial correlations between parallel and orthogonal electric field components. The non-isotropic feature of the correlation widths introduces an azimuthal asymmetry in the intensity, DoP, and DoC distributions. The azimuthal asymmetry in the intensity and DoC distributions become prominent around the focal plane. However, this asymmetry can be clearly observed in DoP distributions even at a very short propagation distance. It is found that the statistical properties of NCVVBs are dependent on both Poincaré–Hopf index (PHI) and the source correlation parameters. The number of beamlets in the intensity distribution is twice the magnitude of the PHI of the input beam. Unlike isotropically correlated vector vortex beams, correlation-induced polarization around the central core of the NCVVB is observed. The DoC distribution exhibits the evolution of correlation singularities in the form of dislocations at the far field plane. These dislocations in the DoC profile under lower correlations depend on the PHI, which provides a feasible approach to measure the index of NCVVBs. This study provides a technique to synthesize beams with structured correlation and polarization features.

Tight-focusing properties of propagable fractional-order vector vortex beams

We investigate the tight-focusing properties of propagable fractional-order vector vortex beams (VVBs). The superposition of the phase singularity from optical vortices (OVs) and polarization singularity from VVBs plays a significant role in creating propagable fractional-order VVBs. Applying this unique characteristic, we derive an integrated analytical model to calculate the tight-focused electromagnetic fields and Poynting vector distributions based on the Richards–Wolf vector diffraction integral. The results show that the tight-focusing intensity of fractional-order VVBs exhibits uniaxial symmetric distribution, in which an odd number of petals with non-uniform amplitude occurs as the beams pass through the polarizer. In contrast to classical integer-order OVs with homogeneously polarized states, propagable fractional-order VVBs show semi-circular patterns with different directions after the polarizer, owing to their intriguing polarization distributions. Besides, to deeply understand the focusing characteristics of the calculated fractional-order VVBs, the influence of different-order carrier VVBs and OVs is studied in detail. These results might provide a valuable reference for particle manipulation and optical trapping.

Binary encoding-inspired generation of vector vortex beams

Binary encoding-inspired generation of vector vortex beams

Effect of rotating target on speckle and orbital angular momentum characteristics of vector vortex beams

Based on angular spectrum diffraction theory, the scattering field of vector vortex beams (VVBs) passing through a rotating random rough surface is derived. The speckle produced by VVBs passing through the rotating ground glass is collected experimentally. The effects of ground glass roughness and rotational speed on the speckle and orbital angular momentum (OAM) of different order VVBs are discussed in detail. Furthermore, the speckle characteristics of the VVB are compared with the scalar vortex beam. The change in the OAM states of VVBs before and after passing through the rotating ground glass was detected by double-slit interference. The results show that the speckle of VVBs is generated after passing through the static ground glass, and the speckle contrast increases with the increment of roughness. Compared with the scalar vortex beam, the speckle contrast of the VVB changes faster with the roughness of ground glass. When the ground glass rotates, the speckle reduction effect appears and the contrast is reduced. When the rotational speed is >15 r / s, the speckle reduction effect is the strongest. The intensity distributions and OAM states of VVBs are not affected by the rotating ground glass. The research results provide a theoretical basis for the application of VVBs in optical communication, optical detection, and other fields.

Generation of perfect vectorial vortex beams by employing coherent beam combining.

Based on coherent beam combining, we propose a method for generating the perfect vectorial vortex beams (VVBs) with a specially designed radial phase-locked Gaussian laser array, which is composed of two discrete vortex arrays with right-handed (RH) and left-handed (LH) circularly polarized states and in turn adjacent to each other. The simulation results demonstrate that the VVBs with correct polarization order and topological Pancharatnam charge are successfully generated. The diameter and thickness of generated VVBs independent of the polarization orders and topological Pancharatnam charges further prove that the generated VVBs are perfect. Propagating in free space, the generated perfect VVBs can be stable for a certain distance, even with half-integer orbital angular momentum. In addition, constant phases φ0 between the RH and LH circularly polarized laser arrays has no effect on polarization order and topological Pancharatnam charge but makes polarization orientation to rotate φ0/2. Moreover, perfect VVBs with elliptically polarized states can be flexibly generated only by adjusting the intensity ratio between the RH and LH circularly polarized laser array, and such perfect VVBs are also stable on beam propagation. The proposed method could provide a valuable guidance for high power perfect VVBs in future applications.

Imprinting Spatial Helicity Structure of Vector Vortex Beam on Spin Texture in Semiconductors

We present the transfer of the spatially variant polarization of topologically structured light to the spatial spin texture in a semiconductor quantum well. The electron spin texture, which is a circular pattern with repeating spin-up and spin-down states whose repetition rate is determined by the topological charge, is directly excited by a vector vortex beam with a spatial helicity structure. The generated spin texture efficiently evolves into a helical spin wave pattern owing to the spin-orbit effective magnetic fields in the persistent spin helix state by controlling the spatial wave number of the excited spin mode. By tuning the repetition length and azimuthal angle, we simultaneously generate helical spin waves with opposite phases by a single beam.

Longitudinal evolution from scalar to vector beams assembled from all-dielectric metasurfaces.

Vector vortex beams (VVBs) with non-uniform polarization states have a wide range of applications, from particle capture to quantum information. Here, we theoretically demonstrate a generic design for all-dielectric metasurfaces operating in the terahertz (THz) band, characterized as a longitudinal evolution from scalar vortices carrying homogeneous polarization states to inhomogeneous vector vortices with polarization singularities. The order of the converted VVBs can be arbitrarily tailored by manipulating the topological charge embedded in two orthogonal circular polarization channels. The introduction of the extended focal length and the initial phase difference effectively guarantees the smoothness of the longitudinal switchable behavior. A generic design approach based on vector-generated metasurfaces can assist in the exploration of new singular properties of THz optical fields.