Perfect Vortex Beam Research Articles

All-dielectric geometric metasurfaces for the generation and manipulation of perfect high-order Poincaré sphere beams

A high-order Poincaré sphere (HOPS) can be used to describe high-order modes of waveguides and vector beams, since it generalizes the feature of spin and the orbital angular momentum of light. HOPS beams are such beams with polarization states on the HOPS, which have potential applications in optical manipulation and optical communication. In general, the intensity distribution of this kind of beam changes with the topological charge, which limits their practical applications. Based on the concept of perfect vortex beams (PVBs), perfect HOPS beams have been proposed to solve this problem. Here, a flexible and compact scheme based on all-dielectric metasurfaces for realizing and manipulating perfect HOPS beams at near-infrared wavelength was demonstrated. Geometric-phase-only manipulation was employed for simultaneously controlling the phase and polarization of the incident light. By varying the incident polarization, several selected polarization states on the HOPS could be realized by the proposed metasurface. Further, the single ultra-thin metasurface can also realize high quality multiplexing perfect HOPS beams that carry different topological charges. Finally, a cascaded metasurface system has been proposed for generating and manipulating multiple HOPS beams. This compact flat-optics-based scheme for perfect HOPS beam generation and manipulation demonstrated here can be used for on-chip optical manipulation and integrated optical communication in the future.

Elliptical spiral zone plate fabrication using direct laser writing for generating an elliptical perfect vortex beam.

We report and fabricate a novel, to our knowledge, vortex beam generator called elliptical spiral zone plate (ESZP) using direct laser writing (DLW), which can generate the elliptical perfect vortex beam (EPVB). It is shown that the radius of the EPVB can be adjusted by tuning the control parameters of the ESZP. It is verified through the interference experiment and the Hermitian-Gaussian light field that the topological charge of the EPVB is consistent with the design. In addition, we integrate the ESZP at the tip of the single-mode fiber. Our work may set the scene for applications in fiber optical tweezers, optical communications, and integrated optics.

Nonlinear frequency up-conversion of perfect vortex beams based on four wave-mixing in 85Rb atoms

Optical vortices are widely explored in quantum optics and communication because of their quantized orbital angular momentum, especially its applications in the frequency conversion process lay a foundation for establishing frequency interfaces. However, limited by the spatial mode matching, constructing the frequency interfaces with uniform conversion efficiency is still a challenge. Here, we propose and demonstrate a frequency up-conversion of perfect vortex beams for accommodating arbitrary topological charges in a diamond atomic system of 85Rb. In this process, the 780 nm, 776 nm and internally generated 5233 nm light fields induce the 420 nm coherent blue light generation. The 776 nm perfect vortex beam with transverse structure-invariance serves as the signal beam, which leads to the uniform conversion efficiency and is accompanied by orbital angular momentum transfer of output 420 nm coherent blue light. In addition, in view of the tunable radius and width, the perfect vortex beams with different transverse sizes are also successfully transferred, which further increases the encoding flexibility.

Metasurface-based perfect vortex beam for optical eraser

Perfect vortex beams (PVBs) take advantage of conventional vortex beams regarding their property of constant diameter of the annular intensity distribution on different topological charges (TCs), facilitating spatially coupling multiple beams with different TCs simultaneously. However, there are demands for PVBs with larger TCs that can be integrated with CMOS-fabrication processes in applications since conditional PVBs are composed of bulky optical components. In this work, we demonstrate metasurface-based PVBs (MPVBs) with TCs as high as −32 and 16 in the visible, manifesting annular intensity distributions capable of broadband operation. The optical eraser concept by integrating MPVBs has been conducted, and the flower-like interference performs a helicity switch to facilitate the uniformization of ring-shaped intensity profiles for the MPVBs with different TCs. The optical eraser experiments demonstrate the potential of MPVBs in advancing both quantum optics and optical device engineering and pave the way for probing quantum behaviors in optics.

Propagation of integral and fractional perfect vortex beams in a gradient-index medium.

The analytical expressions for the complex amplitude of integral and fractional perfect vortex (PV) beams propagating in a gradient-index (GRIN) medium are derived. The intensity and phase distributions, propagation trajectories, Poynting vectors, and the effects of topological charge and refractive index at the medium axis on the intensity of both beams in the medium are numerically investigated. It is shown that both beams propagate periodically in the GRIN medium with alternating spot focusing and reconstruction. Unlike the integral PV beam, the fractional PV beam has a dark line in intensity profiles and a line edge dislocation in phase distributions along the positive x-axis. These properties persist during the beam propagation in the GRIN medium. Moreover, the topological charge and the refractive index at the medium axis have little effect on the intensity of the PV beam propagating in the GRIN medium. The results presented in this paper may be useful for the application of integral and fractional PV beams in optical guiding and optical communications.

Optimization of wireless optical communication using perfect vortex beam

The current perfect vortex beam (PVB) is a novel type of vortex beam that is produced by modulating Bessel–Gaussian beam (BGB) and exhibits intensity distribution structures virtually unaffected by orbital angular momentum (OAM). Compared to an ideal PVB, an PVB based on BGB modulation can only realize a stable intensity structure within a limited range. The stable intensity structure allows higher-order PVB to exhibit better anti-diffraction ability than higher-order BGB, enhancing PVB’ received probability over BGB throughout the communication process when m0=10. The PVB exhibit the self-focusing effect and are influenced by OAM once the limited range is exceeded. The self-focusing effect aids in improving the communication quality of low-order PVB beyond that of BGB during the self-focusing stage. In stronger turbulent, the self-focusing effect exhibits a superior capability to restore PVB’s transmission performance. As the order of OAM modes multiplexing increases, the gap in channel capacity between PVB and BGB during the anti-diffraction stage gradually reduces.

Separation and detection of orbital angular momentum states of composite vortex beams in atmospheric turbulence channels

The separation and detection of compound orbital angular momentum (OAM) modes are the basis for achieving high-speed and high-capacity communication, but the atmospheric turbulence causes distortion of the phase fronts of vortex beams, which hinders the recognition of OAM modes. To solve this problem, in this work, we propose and investigate a joint scheme of combining the Gerchberg–Saxton (GS) algorithm and the phase of addition and subtraction model that can achieve high recognition accuracy and a wide range of OAM modes of compound perfect optical vortex beam under long-distance turbulence environment. At the receiving end, the GS algorithm and phase addition and subtraction are used to compensate and modulate the incident vortex light field to obtain the pre-processed light field, and then the OAM is detected by the coordinate transformation method. The simulation results show that: The detection range of the OAM of the three optical path detection model for the vortex beam transmitting 1000 m reaches −37 to +37 in the vacuum environment, and the mode purity of −37 to +37 can reach more than 0.3 when the turbulence intensity is Cn 2 = 2 × 10−15 m−2/3. The detection range of the OAM of the vortex can be further expanded by increasing the optical path. This study provides a new method for the separation and detection of OAM of composite vortex beams.

Generation of Perfect Vortex Beams with Complete Control over the Ring Radius and Ring Width

We have experimentally created perfect vortex beams (PVBs) by Fourier transformation of Bessel–Gaussian vortex beams, which are generated by modulating the fundamental Gaussian beam with the spiral phase plates and the axicons, respectively. Although the method has been used many times by other authors, as far as we know, few people pay attention to the quantitative relationship between the control parameters of the PVB and ring width. The effects of the waist radius of the fundamental Gaussian beam wg, base angle of the axicon γ, and focal length of the lens f on the spot parameters (ring radius ρ, and ring half-width Δ) of PVB are systematically studied. The beam pattern of the generated Bessel–Gaussian beam for different propagation distances behind the axicon and the fundamental Gaussian beam wg is presented. We showed experimentally that the ring radius ρ increases linearly with the increase of the base angle γ and focal length f, while the ring half-width Δ decreases with the increase of the fundamental beam waist radius wg, and increases with enlarging the focal length f. We confirmed the topological charge (TC) of the PVB by the interferogram between the PVB and the reference fundamental Gaussian beam. We also studied experimentally that the size of the generated PVB in the Fourier plane is independent of the TCs. Our approach to generate the PVB has the advantages of high-power tolerance and high efficiency.

Broadband multifunctional metasurfaces for concentric perfect vortex beam generation via trigonometric functions

Metasurfaces are engineered structures that offer an unprecedented nanoscale solution for precisely manipulating light’s magnitude, phase, and polarization, exhibiting the potential to reduce the size of optical configurations significantly. However, these structures often encounter performance limitations and are typically operational for a single design wavelength. Integrating multiple optical functionalities into a single-layered structure and achieving a highly efficient broadband response is an active metasurface research topic. In this study, we showcased a single-cell driven broadband metasurface capable of generating concentric perfect vortex (PV) beams, where each PV beam is realized by multiplexing the phase profiles of multiple optical components and trigonometric phase features to achieve infinite topological charges. The proposed all-silicon metasurface demonstrates broadband functionality in “E” and “S” optical communication bands spanning from 1460 nm to 1565 nm, covering critical telecom wavelengths, and this characteristic facilitates seamless integration of our work with the existing ecosystem. Our multifunctional approach prioritizes simplicity that yields maximum polarization conversion efficiency and produces different outcomes for different handedness of incident light without introducing complexity. To prove the concept, we numerically simulated multiple metasurfaces for different trigonometric functions, with periods of axicon of 4 µm and 6 µm. The results indicate that this work will pave the way for diverse applications like optical trapping, particle manipulation, quantum processing, optical communication, and high-capacity information processing.

Digital generation of super-Gaussian perfect vortex beams via wavefront shaping with globally adaptive feedback

Abstract High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion (ICF) and optical communication. However, traditional optical vortices featuring nonuniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam (PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm (GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve a flat-top PVB with dramatically reduced beam speckle contrast. The GAFA-based flat-top PVB generation method can pave the way for high-intensity vortex beam generation, which is crucial for potential applications in ICF, laser processing, optical communication and optical trapping.

Spatial quantum coherent modulation with perfect hybrid vector vortex beam based on atomic medium

The perfect hybrid vector vortex beam (PHVVB) with helical phase wavefront structure has aroused significant concern in recent years, as its beam waist does not expand with the topological charge (TC). In this work, we investigate the spatial quantum coherent modulation effect with PHVVB based on the atomic medium, and we observe the absorption characteristic of the PHVVB with different TCs under variant magnetic fields. We find that the transmission spectrum linewidth of PHVVB can be effectively maintained regardless of the TC. Still, the width of transmission peaks increases slightly as the beam size expands in hot atomic vapor. This distinctive quantum coherence phenomenon, demonstrated by the interaction of an atomic medium with a hybrid vector-structured beam, might be anticipated to open up new opportunities for quantum coherence modulation and accurate magnetic field measurement.

Frequency conversion of orbital angular momentum with optimized efficiency and modal purity

The use of nonlinear optics for the creation, control, and detection of structured light has gained prominence of late, but it is plagued by low efficiency and variable modal purity. Here, we show how to optimize the efficiency and modal purity in the nonlinear conversion of structured light modes. Using difference frequency generation of orbital angular momentum carrying Laguerre–Gaussian modes as an example, we achieved more than a 40% rise in efficiency while maintaining the modal purity above 90% compared to conventional methods. To demonstrate the versatility of our approach, we show the frequency conversion of perfect vortex beams up to ℓ=40 in a topological charge, achieving a new state of the art. We believe this theoretical treatment will facilitate our work’s translation to other modal forms and nonlinear processes.

Transmission of optical communication signals through ring core fiber using perfect vortex beams.

Orbital angular momentum can be used to implement high capacity data transmission systems that can be applied for classical and quantum communications. Here we experimentally study the generation and transmission properties of the so-called perfect vortex beams and the Laguerre-Gaussian beams in ring-core optical fibers. Our results show that when using a single preparation stage, the perfect vortex beams present less ring-radius variation that allows coupling of higher optical power into a ring core fiber. These results lead to lower power requirements to establish fiber-based communications links using orbital angular momentum and set the stage for future implementations of high-dimensional quantum communication over space division multiplexing fibers.

Analysis of rotational Doppler shift with multi-ring vortex beams.

Vortex beams (VBs) with orbital angular momentum have shown great potential in the detection of transverse rotational motion of spatial targets which is undetectable in the classical radar scheme. However, most of the reported rotational Doppler measurements based on VBs can only be realized under ideal experimental conditions. The long-range detection is still a challenge. The detection distance based on rotational Doppler effect (RDE) is mainly limited by the scattered signal's signal-to-noise ratio (SNR). In this work, we investigated the influence of multi-ring vortex beams (MVBs) on the rotational Doppler frequency spectrum of scattered light from an object based on RDE and proposed a method of SNR enhancement of RDE signal. Firstly, different types of MVBs composed of a set of single-ring VBs with the same topological charge and different radii are designed, including multi-ring Laguerre Gaussian beam (MLGB), multi-ring perfect vortex beams (MPVB), and high-order Laguerre Gaussian beam (HLGB). Then, the influence of the number of rings and radial radius interval on the intensity profiles of MVBs and rotational Doppler frequency spectra under aligned and misaligned conditions is studied in detail. And the reasons why different types of MVBs lead to different SNR enhancement effectiveness with the increase of rings are also analyzed theoretically. Finally, proof-of-concept experiments were conducted to verify the effectiveness of the SNR enhancement method for RDE signals. The results showed that the amplitudes of the Doppler spectra generated by the MLGB and MPVB are improved substantially with the increase of rings, but the enhancement effect caused by the former is superior to the latter. The gain of HLGB on the RDE signal is the lowest. This study provides a useful reference for the optimization of rotational Doppler detection systems and may be of great application value in telemetry, long-range communication and optical imaging.

Reconfigurable perfect vortex beam generator based on a liquid crystal spiral phase plate.

A transmissive adaptable optical setup to generate a range of perfect vortex beams (PVBs) carrying different topological charges (TC) without using moving parts is presented. The setup is composed of an ad hoc transparent reconfigurable liquid crystal (LC) spiral phase plate (SPP), a refractive axicon and a convergent refractive lens. The LC SPP electrodes are manufactured ablating indium-tin oxide (ITO) glass substrates using direct laser writing (DLW) resulting in a very high fill factor device. In-house tailored electronics drive the 72 LC SPP electrodes giving rise to 72 different configurations with orbital angular momentum. In this work, the generation of PVBs with 36 positive or 36 negative TCs using this optical setup is accomplished.

Generating broadband nondiffracting perfect vortex beams in the visible regime

Generating broadband nondiffracting perfect vortex beams in the visible regime

Crosstalk characteristics of orbital angular momentum of focused perfect vortex beam in atmospheric turbulence

The perfect optical vortex beam (POV) is a special kind of vortex beam, whose radius is independent of its orbital angular momentum (OAM) mode, but the atmospheric turbulence (AT) causes crosstalk between different topological charges, which is a serious challenge in OAM-based communication system. We establish a theoretical model with a turbulence suppression effect for deriving the spiral spectrum of a focused perfect optical vortex beam (FPOV) after propagation through anisotropic AT. Through numerical analysis, we simulate the behavior of FPOV under different turbulence and beam parameters to better understand the effect of the received probability and its corresponding modal crosstalk under various conditions. In addition, the simulation of AT uses the multi-phase screen method to verify the theoretical results. The results show that the changes in topological charge, wavelength, receiving aperture, beam waist, and hollow radius all have an influence on the received probability. Also, some strategies for selecting turbulence parameters to reduce modal crosstalk in anisotropic AT are also discussed. The focus would reduce the effect of turbulent aberrations on the signal OAM mode received probability, and the FPOV provided better performance than the POV, which may be useful in OAM-based free space optical communication.

Detection of fluid motion direction based on the rotational Doppler effect of grafted perfect vortex beam.

Vortex beams have attracted much attention due to their unique rotational Doppler effect. With the in-depth study of vortex beams, many new vortex beams have been proposed gradually, while the detection of fluid motion is of great significance for the study of ocean turbulence. Based on the rotational Doppler effect of the grafted perfect vortex beam, we propose a non-embedded optical method for real-time detection of the magnitude and direction of fluid velocity and establish a two-dimensional fluid model for simulation verification. It is proved that the grafted perfect vortex beam can detect the magnitude and direction of the fluid velocity at the same time, which may provide a new way and theoretical support for the detection of fluid motion direction.

Terahertz quasi-perfect vortex beam with integer-order and fractional-order generated by a spiral spherical harmonic axicon

Abstract We have proposed a new method to generate terahertz perfect vortex beam with integer-order and fractional-order. A new optical diffractive element which is composed of the phase combination of a spherical harmonic axicon and a spiral phase plate is designed, and called spiral spherical harmonic axicon. A terahertz Gaussian beam passes through the spiral spherical harmonic axicon to generate a terahertz vortex beam. When only increasing the number of topological charges carried by spiral spherical harmonic axicon, the ring radius of terahertz vortex beam increases slightly, so it is a terahertz quasi-perfect vortex beam. Importantly, the terahertz quasi-perfect vortex beam can carry not only integer-order but also fractional-order topological charges. This is the first time that vortex beam and quasi-perfect vortex beam with fractional-order has been successfully realized in terahertz domain and experiment.

Elliptic perfect vortex beam generation with selective modes based on single layer metasurface in broadband near-infrared range

Asymmetric and multiple modes of perfect vortex beams (PVBs) are of great significance in the manipulation of nanoscale biological cells. As a powerful artificial subwavelength platform, miscellaneous metasurfaces have been reported to generate PVBs. However, these reported PVBs are always symmetric, that is, only one simple annular shape in the observation plane, which cannot provide multiple modes. Here, using multi-coordinate transformation techniques (MCTT), we established the phase profile of mode-selective elliptic perfect vortex beams (MS-EPVBs) in elliptical coordinate and generated multiple modes of EPVBs with arbitrary eccentricity and orientation in broadband near-infrared range based on all-dielectric metasurface, greatly enriching the modes of PVBs. Composed of optimized half-waveplate-like silicon cylinders, the designed metasurface can freely transform the incident light into EPVBs with arbitrary eccentricity and orientation with high efficiency. Furthermore, during the mode transformation, the properties of the “perfect” and broadband were preserved. This work will find potential applications in advanced fields like biophotonics and genetic engineering.