Vector Beams Research Articles

The Propagation Characteristics of Circular Airy Beams with Propagational Fractional-Order Optical Vortices

We investigate the propagation properties of circular Airy beams (CABs) with propagational fractional-order optical vortices (OVs). The superposition of the phase singularity and polarization singularity from a vortex vector beam (VVB) plays a significant role in creating a propagational fractional vortex beam. Propagational fractional vortex beams can be considered as a superposition of left and right circularly polarized vortex beams with different integer topological charges (TCs). We study the propagation characteristics of two kinds of propagational fractional vortex CABs, and the results show that both of the two kinds of beams can stably propagate in free space, and they exhibit an “abruptly auto-focusing” property and “self-healing” property during the propagation. The intensity distribution of the first kind of propagational fractional vortex CAB has an odd number of petals (2m + 1), while the second kind of beam has a crescent-shaped intensity distribution. The influence of turbulence on the beam propagation through atmosphere under different turbulence strengths is also numerically studied in this paper. A fractional vortex CAB with an initial radius r0 = 10 mm can retain its shape after propagating 20 m when the atmospheric refractive-index structure constant CN2=0.2×10−12m−2/3. Our results are expected to broaden the application of CABs.

Monolayer Chiral Metasurface for Generation of Arbitrary Cylindrical Vector Beams

The cylindrical vector beam (CVB) has been widely studied and applied in recent years. However, many CVB generation methods suffer from complex systems, and large-size devices are required. Here, we propose a monolayer chiral metasurface composed of spin-sensitive unit cells which can generate different holograms for left- and right-circular polarization based on the combined modulation of geometric phase and detour phase. With a linearly polarized incident beam, the metasurface can generate CVBs with controllable polarization angles and orders, and even more complex vector beams. This work provides a new idea for the design of miniaturized optical devices for generating arbitrary vector beams.

3D Polarisation of a Structured Laser Beam and Prospects for its Application to Charged Particle Acceleration

A Structured Laser Beam (SLB) is a type of optical beam with spatially inhomogeneous 3D polarisation structures. Generating SLBs from vector beams allows the creation of Hollow Structured Laser Beams (HSLB) with a dark central core. In this way, atypical electric and magnetic field vectors, which are purely longitudinally polarized in the dark zones of the beam, are obtained. The SLB spatial distribution can also include regions with both the electric and magnetic fields longitudinally polarized and oriented in the same or opposite directions. The SLB has a transverse distribution similar to that of a Bessel beam but can theoretically propagate to infinity, therefore giving the potential to generate strong, longitudinally oriented electric fields over long distances, which could possibly allow the acceleration of charged particles. The results of the study of this phenomenon, including simulations of the spatial distribution of the electromagnetic field components, are presented in this paper.

Generation and 2D field imaging of THz vortex beams

Optical rectification along three-fold axis in zincblende-symmetry crystal is used to generate vector and scalar vortex beams in THz. 2D electro-optic imaging is used for frequency- resolved THz field amplitude and phase characterization.

Focusing Optimization and Control of Cylindrical Vector Beams with Blazed Subwavelength Grating Lens

Focusing Optimization and Control of Cylindrical Vector Beams with Blazed Subwavelength Grating Lens

Characterization of Thin Film Parameters Based on Polarization Properties of Vector Beams

Characterization of Thin Film Parameters Based on Polarization Properties of Vector Beams

Generation and high-resolution focusing of higher-order vector beam via metasurface

Generation and high-resolution focusing of higher-order vector beam via metasurface

Propagation properties of partially coherent vector beam with multiple off-axis vortex phases

In this paper, we investigate the propagation properties of radially polarized rectangular-symmetric cosine-Gaussian Schell-model (RCGSM) beam with multiple off-axis vortex phases by using Fourier transform and convolution method based on the unified theory of coherence and polarization. The results indicate that the radially polarized RCGSM beam has self-splitting properties and can be split into four identical lobes due to its unique spatial coherence structure. Furthermore, the modulation of multiple off-axis vortex phases can be acted on each lobe. For high coherence, the spot arrays with triangular or square hollow light intensity distribution can be generated in the focal plane by modulating the number of off-axis vortices (<i>N</i><sub>0</sub>) and the beam order, and the corresponding state of polarization on each lobe presents an inverted triangular or oblique square elliptic distribution. However, for small coherence, the modulation effect of multiple off-axis vortex phases disappears and the light intensity of each lobe degenerates into a quasi-Gaussian distribution, whereas its state of polarization keeps invariant, which is independent of the beam order and coherence length. In addition, the beam still has a certain self-healing ability for one of the off-axis vortex phases partially blocked by an obstacle, but it will be destroyed for completely blocking, resulting in a notch on each lobe.

Toroidal dipole response in rectangular waveguide: used to generate vector beams and vector vortex beams

Toroidal dipole response in rectangular waveguide: used to generate vector beams and vector vortex beams

Ultrafast vectorial calculation of tightly focused vortex and non-vortex fields in a meridional plane

It is shown that for vortex and non-vortex vector beams diffracted by the exit pupil of a high numerical aperture (NA) focusing system with axial symmetry, the electromagnetic field near the focus can be represented in a general form involving several one-dimensional (1D) discrete Fourier transforms associated with three orthogonally polarized components of the field. Based on this form, a simple and effective method is proposed for ultrafast calculation of the tightly focused fields in an arbitrary meridional plane using the algorithms of 1D fast Fourier transform or 1D chirp Z transform. To compare the proposed method with the traditional method of direct calculation, three typical examples are given with an emphasis on estimating the time and accuracy of calculating tightly focused vortex and non-vortex electromagnetic fields produced by a high NA aplanatic lens, with linear or radial polarization of the light field at the annular entrance pupil of the lens.

Multi-Mode Vector Light Field Generation Using Modified Off-Axis Interferometric Holography and Liquid Crystal Spatial Light Modulators

The increasing enhancement in the modulation accuracy of spatial light modulators has garnered significant attention towards real-time control technology for light fields based on these modulators. It has been demonstrated that this technology possesses a remarkable capability to generate vector beams with arbitrary complex amplitude distributions. Nevertheless, past studies indicate that the generation of only one vector beam at a time has been observed. The simultaneous generation of numerous vector light fields can give rise to several challenges, including compromised picture quality, limited single-mode operation, and intricate optical path configurations. In pursuit of this objective, we present a novel methodology that integrates the coding methodology of modified off-axis interferometric holography with the idea of optical superposition. This technique facilitates the concurrent generation of several vector beams. In this study, we present a demonstration of the simultaneous creation of twelve vector beams using a single spatial light modulator (SLM) as a proof of concept. Significantly, this technology has the ability to generate an unlimited quantity of vector light fields concurrently under the assumption that the resolution of the SLM does not impose any limitations. The findings indicate that the imaging quality achieved by this technology is of a high standard. Furthermore, it is possible to separately control the beam waist radius, topological charge, polarization order, and extra phase of each beam.

Lissajous singularities in Young's interference experiment.

We explore the interference of two bichromatic vector beams in Young's interference experiment. Our analysis focuses on determining the conditions under which the superposition of such beams, emerging from the pinholes, can give rise to Lissajous-type polarization singularities on the observation screen. Two independent sufficiency conditions are derived. This analysis aids in comprehending the inherent characteristics of Lissajous singularities. To the best of our knowledge, this is the first demonstration of the singular behavior of polarization in a two-frequency field in Young's interference experiment.

Polarization of the third harmonic emission from the filamentation of femtosecond cylindrical vector beams.

We experimentally generate a third harmonic (TH) vector optical field in deep ultraviolet wavelength range using femtosecond vector laser beams. The generated TH beams are characterized by analyzing the Stokes parameters with different input laser energies. The results show that the TH predominantly preserves the vector polarization distribution of the fundamental frequency beam. Moreover, the intensity profile of the TH exhibits a multiple-ring structure. A hybrid polarization pattern is observed in the TH, where the ellipticity is influenced by the input laser energy. Our work provides an effective and straightforward method for producing TH vector optical fields, which may facilitate potential applications such as micro/nanofabrication and super-resolution microscopy.

Generation of high radial node vector vortex beams based on digital micromirror device

The modulation of amplitude, phase, and polarization to generate complex vector light fields with spatially variant polarization distribution has become a hot research topic in recent years. We propose a new method for generating high radial node vector vortex beams (VVB) based on a digital micromirror device (DMD). Firstly, we propose a multiplexed binary hologram with varying ellipticity, which can significantly optimize the vortex beam generated by DMD while the mode purity of the scalar vortex beam after optimization can reach 97.23%. Secondly, a novel interference experimental setup is proposed based on the Wollaston prism, which can realize arbitrary control of VVBs. Based on this, the high radial node VVBs with p=10 and high polarization order VVBs with polarization order up to 25 are generated experimentally. Finally, we reconstruct the State of Polarization (SoP) of the vector beam l=4,m=-4,p=4 based on the Stokes parameter S1,S2,S3, and the variation of vector quality factor (VQF) on the high-order Poincaré sphere (HOPS) is analyzed. Our technology provides a high-quality vector beam generation scheme with important applications in laser detection, optical communication, and optical micro-manipulation.

Correlating Space, Wavelength, and Polarization of Light: Spatiospectral Vector Beams

Correlating Space, Wavelength, and Polarization of Light: Spatiospectral Vector Beams

Detecting topological index of randomly scattered V-point singularities using Stokes correlations.

Topological defects in vector fields constitute polarization singularities that have numerous applications in classical and quantum optics. These beams are inhomogeneously polarized and are shown to self-heal under symmetric amplitude perturbations. Polarization singular beams are characterized using a singularity index that can be detected using Stokes polarimetry or other interferometric and diffraction approaches. However, the information about the singularity index is lost when these beams travel through random scattering media; this results in a spatially fluctuating polarization pattern known as polarization speckle. This paper proposes and experimentally demonstrates a new method to detect the topological index of these randomly scattered V-point singularities using higher-order Stokes correlations in a lensless condition. A detailed theoretical basis is developed, and the performance of the technique is demonstrated by retrieving the signature of polarization singularities with Poincaré-Hopf index |η|=1 and |η|=2. We also demonstrate that by studying the intensity-intensity correlations of the polarization speckle, it is possible to differentiate between different vector beams having the same magnitude as the Poincaré-Hopf index.

Generation of Complex Vector and Vortex Extreme Ultraviolet Beams Using the S-Waveplate and Spiral Phase Plate during High-Order Harmonics Generation in Argon

Generation of Complex Vector and Vortex Extreme Ultraviolet Beams Using the S-Waveplate and Spiral Phase Plate during High-Order Harmonics Generation in Argon

Violation of Bell’s inequality for helical Mathieu–Gauss vector modes

Vector beams display varying polarisation over planes transversal to their direction of propagation. The variation of polarisation implies that the electric field cannot be expressed as a product of a spatial mode and its polarisation. This non-separability has been analysed for particular vector beams in terms of non–quantum entanglement between the spatial and the polarisation-degrees of freedom, and equivalently, with respect to the degree of polarisation of light. Here we demonstrate theoretically and experimentally that Mathieu–Gauss vector modes violate a Bell-like inequality known as the Clauser–Horn–Shimony–Holt–Bell inequality. This demonstration provides new insights on the violation of Bell inequalities by a more general class of vector modes with elliptical symmetry.

An efficient Yb:YAG microchip laser for generating high-power cylindrical vector beams with four topological charges

High-power cylindrical vector beams (CVBs) in the form of Laguerre-Gaussian (LG0,l) with fixed topological charge and desirable state of polarization (SoP) have been widely needed for various applications such as quantum communication, optical trapping, manipulating microparticles, laser machining, and high-resolution imaging. Highly efficient high-order CVBs with fixed topological charge and SoP generated in solid-state lasers are desirable for various applications. Here, by adjusting annular pump beam waist and distance between focus spot and gain medium, we directly generated LG0,l (l = 2, 3, 4) CVBs with SoP in the form of E0,l(ϕ,r) = - Eϕ ×sin[(l + 1)ϕ]+ Er ×cos[(l + 1)ϕ] in a highly efficient Yb3+:Y3Al5O12 (Yb:YAG) microchip laser. The LG0,4 CVB is obtained when the input pump power is higher than 2.9 W and keeps as the input pump power further increases. The output power of the LG0,4 cylindrical vector laser is 1.3 W at the input pump power of 6.1 W. The optical conversion efficiency is as high as 21.3%. Polarization purity is over 93% for LG0,4 CVB generated in the Yb:YAG microchip laser.

Spin angular momentum at the sharp focus of a cylindrical vector vortex beam

Sharp focusing of a light field with double (phase and polarization) singularity is studied. Using the Richards-Wolf method, an exact analytical expression for the longitudinal projection of the spin angular momentum (SAM) vector at the focus is obtained. The expression derived suggests that 4 (n –1) subwavelength regions are formed at the focus, where n is the cylindrical vector beam order, with their centers located on a certain circle centered on the optical axis. Notably, the SAM projections are found to have the opposite sign in the neighboring regions. This means that in the neighboring focal regions, the light has alternating left or right elliptical polarization (manifestation of a spin Hall effect). At the center of the focal spot near the optical axis, the field is right-handed elliptically polarized at m > 0, or left-handed elliptically polarized at m < 0, where m is the vortex charge. The total longitudinal spin, i.e., the longitudinal SAM component averaged over the beam-cross section, is zero and preserved upon focusing. Due to the beam containing an optical vortex with charge m, the transverse energy flow rotates on a spiral path near the focal plane, rotating on a circle in the focal plane. The rotation direction near the optical axis is counterclockwise for m > 0, and clockwise for m < 0.