Generation Of Vector Beams Research Articles

Broadband spatial polarization processing of light via a photopatterned dichroic medium

Vector beams, featured by a specific space-variant distribution of polarization, have attracted intensive attention. Arbitrary and broadband spatial polarization processing is a key pursuit for vector beam generation, modulation, and detection. Here, we introduce black dye into liquid crystals to form a dichroic medium and imprint high-resolution patterns into the medium via photopatterning. Continuous cylindrical and binary vector beams are freely generated. Switching between a vector beam generator and a high-transmittance homeotropic state can be realized due to the electro-optical tunability of liquid crystals. On the basis of a radial vector beam generator array, the polarization distribution is characterized by calculating the darkest line of each generator. This strategy provides a platform for arbitrary spatial polarization processing and may bring more possibilities for polarization imaging, structured light generation, and materials characterization.

Optical encryption technology based on spiral phase coherent superposition and vector beam generation system

A new optical encryption technology based on spiral structured phase coherent superposition and vector beam generation system is proposed. Firstly, the original image is scrambled by Arnold transform, and the scrambled image is encoded into two phase plates by using the spiral structured phase plates and the principle of coherent superposition. Then these two phases are brought into the vector beam generation system, and Stokes parameters of vector beam are recorded on the output plane to complete the image encryption. The original image can be recovered with the correct keys when decrypted. The system has good key sensitivity and resistance to occlusion attacks. The simulation results verified the correctness and effectiveness of the method.

Design of broadband terahertz vector and vortex beams: I. Review of materials and components

In this paper, we review the existing approaches for vortex and vector beam shaping and generation in the terahertz frequency range. The particular focus of this review is on the possibility of homogeneous topological charge formation in the ultra-wide spectral interval inherent to ultrashort terahertz pulses. We review the available materials and components, analyse proposed and potentially possible solutions for broadband terahertz vortex and vector beam shaping, compare all developed approaches, and put forward a unified concept for constructing passive shapers of such beams from the existing component base.

High-Order Cylindrical Vector Beam Generation and Its Polarization Detection Based on Cascade Vortex Half-Wave Plates

High-Order Cylindrical Vector Beam Generation and Its Polarization Detection Based on Cascade Vortex Half-Wave Plates

Cylindrical Vector Beam Generation from a Passively Mode-Locked Raman Fiber Laser

Cylindrical Vector Beam Generation from a Passively Mode-Locked Raman Fiber Laser

High‐Efficiency Phase and Polarization Modulation Metasurfaces

Use of metasurfaces to control the characteristics of electromagnetic waves is an emerging trend at present. Multifunctional metasurfaces, which can modulate multiple wave parameters, greatly reduce the complexity and enrich the functionality of optical systems. Herein, a high‐efficiency multifunctional metasurface for operation in the terahertz band is proposed and demonstrated. Use of a trilayer structure allows the working efficiency to reach 85% at the designed operating frequency. The phase and polarization states of the transmitted waves are modulated individually via subtle adjustment of the geometric parameters of each layer. Two terahertz‐band vector beam generators are demonstrated based on the proposed metasurface. The two devices individually generate radial and azimuthal terahertz vortex beams that can carry arbitrary orbital angular momentum. The experimental results demonstrate the validity of the proposed approach. This method represents a route toward easy fabrication of high‐performance phase and polarization modulation metasurfaces that can improve the information‐carrying capabilities of terahertz systems and offers benefits for structured light generation, optical information security, and optical communication applications.

Mid-infrared cylindrical vector beams enabled by dielectric metasurfaces

Over the last decade, photonics in the mid-infrared (mid-IR) frequency range had major advances in both generation and detection of light. However, efficient manipulation of the mid-IR light still faces many challenges. Spatially inhomogeneous control over the wavefront and polarization of mid-IR radiation is particularly difficult. Many standard techniques used for visible and near-infrared frequencies, such as liquid crystal-based spatial light modulation, are not applicable in the mid-IR due to unfavorable material properties in that spectral range. Here, we demonstrate spatially inhomogeneous polarization control of the mid-infrared light using custom-designed vortex retarders. Vortex retarders, while being widely used in the near-infrared and visible spectral ranges for generation of cylindrical vector beams, have been missing in the mid-infrared spectral range. Our implementation of mid-infrared vortex retarders is based on the concept of metasurfaces. We demonstrate metasurface-based vortex retarders at the wavelengths of 2.9 and 3.5 μm. We compare the performance of all-dielectric metasurface vortex retarders with the elements arranged in square and hexagonal lattices [Arbabi et al., Nat. Nanotechnol. 10, 937–943 (2015) and Arbabi et al., Nat. Commun. 6, 7069 (2015)]. Our work could accelerate the adoption of metasurfaces for the development of novel classes of mid-infrared optical components.

Design of Metasurface with Nanoslits on Elliptical Curves for Generation of Dual-Channel Vector Beams.

The manipulations of nanoscale multi-channel vector beams (VBs) by metasurfaces hold potential applications in various important fields. In this paper, the metasurface with two sets of nanoslits arranged on elliptic curves was proposed to generate the dual-channel focused vector beams (FVBs). Each set of nanoslits was composed of the in-phase and the out-of-phase groups of nanoslits to introduce the constructive interference and destructive interference of the output light field of the nanoslits, focusing the converted spin component and eliminating the incident spin component at the focal point. The two sets of nanoslits for the channels at the two focal points were interleaved on the same ellipses, and by setting their parameters independently, the FVBs in the two channels are generated under illumination of linearly polarized light, while their orders and polarization states of FVBs were controlled independently. The generation of the FVBs with the designed metasurfaces was demonstrated by the finite-difference time domain (FDTD) simulations and by the experimental verifications. The work in this paper is of great significance for the generation of miniaturized multi-channel VBs and for broadening the applications of metasurfaces.

Spin-decoupled metasurface for broadband and pixel-saving polarization rotation and wavefront control.

In this paper, a strategy to achieve a simultaneous wavefront shaping and polarization rotation, without compromising the number of pixels and energy efficiency as well as having broadband operation range, is proposed. This strategy is based on the application of a spin-decoupled phase metasurface composed by only one set of metal-insulator-metal (MIM) umbrella-shaped chiral unit cells. Quasi-non-dispersive and spin-decoupled phase shift can be achieved simply by changing single structural parameter of the structure. By further merging the Pancharatnam-Berry (PB) geometric phase, conversion of an incident LP light beam into right- and left-handed circularly polarized reflected beams with similar amplitudes, desired phase profiles and controlled phase retardation on a nanoscale is enabled with high efficiency. Based on the proposed strategy, a polarization-insensitive hologram generator with control optical activity, and a multiple ring vortex beam generator are realized. The results obtained in this work provide a simple and pixel-saving approach to the design of integratable and multitasking devices combining polarization manipulation and wavefront shaping functions, such as vectorial holographic generators, multifocal metalenses, and multichannel vector beam generators.

Practical generation of arbitrary high-order cylindrical vector beams by cascading vortex half-wave plates

A practical direct-view scheme for generating arbitrary high-order cylindrical vector (HCV) beams by cascading vortex half-wave plates (VHPs) is presented. The combination of odd number 2n-1 VHPs for n≥1 can realize (m2n-1-m2n-2+…+m1)-order CV beams, in which m is the order number of VHP and the corresponding subscript 2n-1 represents the arrangement number of VHPs, and the cascading of even number 2n ones can obtain (m2n-m2n-1+…+m2-m1)-order CV beams. All 1-12 order CV beams, including the high-order anti-vortex CV (ACV) beams, are generated only by selectively cascading the VHPs with m=1, 3 and 8. The polarization properties of the generated HCV beams are investigated by measuring the corresponding Stokes parameters. It is experimentally demonstrated that arbitrary HCV beams are effectively achieved by the proposed method. The order numbers of CV beams can be greatly expanded by cascading limited types of VHPs.

Efficient generation of annular cylindrical vector beams by refractive axicons with high-transmission thin-film retarders

A new type of energy-efficient thin-film-coated (TF) conical optics is presented that combines annular beam shapers and cylindrical polarization converters to transform a linearly polarized laser beam into annular cylindrical vector beams. The main operational steps of the polarization converters include the generation of a circularly polarized vortex beam, the compensation of a quarter-wave shift between its p- and s-polarized components, and the summation of these components, with the last two steps being carried out simultaneously by means of such key elements as conically illuminated high-transmission TF retarders. Three optical configurations are considered and analyzed, of which the TF retarders are located on the conical surfaces of two refractive beam-shaping axicons. The total light throughput of such configurations approach 100% and they are suitable for operation at deep UV wavelengths and high power density. As potential elements of these configurations, five TF retarders are designed and optimized at a wavelength of 266 nm. Numerical simulations and comparison of the angular and spectral characteristics of these TF retarders confirm that they comply with the tolerances on the acceptable deviations of axicon wedge angles and wavelengths of typical high-power CW lasers with the above wavelength. Also presented are the results of a tolerance analysis of the TF retarders with respect to their TF thicknesses.

Ultraviolet waveband vector beams generation assisted by the nonlinear frequency conversion

Vector beams with a nonseparable polarization distribution are almost thoroughly studied from their generation to application in infrared and visible regimes. Until now, the nonlinear generation of ultraviolet vector beams is only focused on the nonlinear optical processes of gas molecules, which seriously impacts its further applications due to the unstable property. Here, we present a study on the generation of ultraviolet vector beams assisted by the nonlinear frequency conversion processes in potassium dihydrogen phosphate crystals. The vectorial properties of the generated ultraviolet waveband vector beams are characterized in both theoretical and experimental environments. The proposed method paves the way for the generation of extreme ultraviolet vector beams with solid-state nonlinear crystal, which is a more compact and stable way compared with the gas nonlinear method. This work also opens a route for photolithographic techniques and laser processing based on ultraviolet waveband vector beams.

Metasurface of Combined Semicircular Rings with Orthogonal Slit Pairs for Generation of Dual Vector Beams.

Manipulation of multichannel vector beams (VBs) with metasurfaces is an important topic and holds potential applications in information technology. In this paper, we propose a novel metasurface for the generation of dual VBs, which is composed of orthogonal slit pairs arranged on multiple groups of combined semicircular rings (CSRs). A group of CSRs include a right-shifted set and a left-shifted set of semicircular rings, and each set of semicircular rings has two halves of circles with different radii, sharing the same shifted center. Under the illumination of linearly polarized light, the two shifted sets of semicircular rings generate the two VBs at the shifted center positions on the observation plane. The slit units of each set are designed with independent rotation order and initial orientation angle. By adjusting the linear polarization of illumination, both two VBs with their orders and polarization states are independently controlled simultaneously. The principle and design are demonstrated by the finite-difference time domain (FDTD) simulation. The work is of significance for miniatured devices of VB generators and for related applications.

Arbitrary cylindrical vector beam generation enabled by polarization-selective Gouy phase shifter

Cylindrical vector beams (CVBs), which possess polarization distribution of rotational symmetry on the transverse plane, can be developed in many optical technologies. Conventional methods to generate CVBs contain redundant interferometers or need to switch among diverse elements, thus being inconvenient in applications containing multiple CVBs. Here we provide a passive polarization-selective device to substitute interferometers and simplify generation setup. It is accomplished by reversing topological charges of orbital angular momentum based on a polarization-selective Gouy phase. In the process, tunable input light is the only condition to generate a CVB with arbitrary topological charges. To cover both azimuthal and radial parameters of CVBs, we express the mapping between scalar Laguerre–Gaussian light on a basic Poincaré sphere and CVB on a high-order Poincaré sphere. The proposed device simplifies the generation of CVBs enormously and thus has potential in integrated devices for both quantum and classic optical experiments.

Concise and efficient direct-view generation of arbitrary cylindrical vector beams by a vortex half-wave plate

A concise, efficient, and practical direct-view scheme is presented to generate arbitrary cylindrical vector (CV) beams, including CV beams, vortex beams, and cylindrical vector vortex (CVV) beams, by a vortex half-wave plate (VHP). Six kinds of first-order and other high-order CV beams, such as azimuthally polarized (AP) beams, antivortex radial polarization mode beams, and three-order AP beams, are formed by simply rotating a half-wave plate. The Stokes parameters and double-slit interference of multitype CV beams are investigated in detail. The polarization parameters, including degree of polarization, polarization azimuth, and ellipticity, are obtained, which demonstrates the efficient generation of CV beams. In addition, the double-slit interference experiment is introduced in the setup, and fringe misplacement and tilt appear for CVV beams, in which the misplacement number M is 2 P + 1 for P ≤ 2 and 2 P − 1 for P ≥ 3 , where P is the polarization order number, and the fringe tilt offset is positively related to the topological charge number l of CVV beams. In addition, new types of VHPs can be formed by cascading two or more VHPs when the types of available VHPs are limited, assisting in more flexible generation of multitype CV beams. It is experimentally demonstrated that arbitrary CV beams with high quality are effectively achieved by the proposed setup, and the double-slit interference method can be utilized to determine and analyze CV beams rapidly and concisely by practical performance, which shows the potential to be implemented as a commercial device.

High-speed generation of singular beams through random spatial multiplexing

Complex vector modes have become topical of late due to their fascinating properties and the many applications they have found across a broad variety of research fields. Even though such modes can be generated in a wide variety of ways, digital holography stands out as one of the most flexible and versatile. Along this line, digital micromirror devices (DMDs) have gained popularity in recent times due to their high refresh rates, which allows the generation of vector modes at kHz rates. Nonetheless, most techniques are limited either by the diversity of vector modes that can be generated or by the speed at which they can be switched. Here we propose a technique based on the concept of random encoding, which allows the generation of arbitrary vector beams at speeds limited only by the refresh rate of the DMD. Our technique will be of great relevance in research fields such as optical communications, laser material processing and optical manipulation, amongst others.

All-fiber cylindrical vector beams laser based on the principle of mode superposition

We propose a novel method for the generation of a cylindrical vector beams (CVBs) laser in an all-polarization-maintaining fiber (PMF) configuration based on the principle of mode superposition. By using this method, a stable and high purity radially polarized (TM01) mode is obtained by stretching fiber to adjust phase shift. The laser with TM01 mode has a maximum power of (19.2 ± 0.1) mW and a slope efficiency of (22.02 ± 0.06) %, whose mode purity is approximately (91.8 ± 0.1) %. This method can be extended to generate azimuthally polarized (TE01) or higher order cylinder vector modes. Owing to its compact and high stability, this laser is promising for industrial processing and biomedical applications.

Generation of vector beams of Bell-like states by manipulating vector vortex modes with plasmonic metasurfaces

Metasurfaces with orthogonal nano-slit pairs arranged on spirals are proposed to generate vector beams (VBs) of Bell-like states and slanted polarizations. The design of the metasurfaces is based on the theoretically derived parameter condition for manipulation of the two vector vortex modes, which is satisfied by matching the three parameters of rotation order m , the spiral order n , and incident polarization helicity σ . The linear polarization states of the VBs are controlled by the initial orientation angle φ 0 of slit pairs. VBs of satisfying quality are experimentally obtained, with the analytical and simulated results validated.

Ultrathin freestanding terahertz vector beam generators with free phase modulation.

Simultaneous control of phase and polarization offers a large degree of freedom to tailor the beam properties, for instance, enabling generation of structured beams such as vector beams and vector vortex beams. Here, we propose an ultrathin freestanding metasurface operating at the terahertz frequency for efficient generation of vector vortex beam with an arbitrarily defined topological charge from linearly polarized excitation. The metasurface is composed of bilayer metallic patterns separated by a thin quartz slab, with one layer determining the transmission polarization and the other controlling the transmission phase. The tightly cascaded two layers form a Fabry-Perot cavity to maximize the efficiency of the polarization and phase control. Two metasurfaces for generation of radially polarized vector beam with uniform phase and vortex phase are fabricated and tested at 0.14 THz. The experimental results successfully demonstrate the generation of high-quality vector beams with the desired phase. In the experiment, the ultrathin and freestanding properties allow the metasurface to be easily combined with other components, which shows great potential for the development of various compact terahertz systems.

Generation of nanosecond cylindrical vector beams in two-mode fiber and its applications of stimulated Raman scattering

We present the generation of the nanosecond cylindrical vector beams (CVBs) in a two-mode fiber (TMF) and its applications of stimulated Raman scattering. The nanosecond (1064 nm, 10 ns, 10 Hz) CVBs have been directly produced with mode conversion efficiency of ∼18 dB (98.4%) via an acoustically induced fiber grating, and then the stimulated Raman scattering signal is generated based on the transmission of the nanosecond CVBs in a 100-m-long TMF. The transverse mode intensity and polarization distributions of the first-order Stokes shift component (1116.8 nm) are consistent with the nanosecond CVBs pump pulse.