ring-Airy Beams Research Articles

Poincaré tornados.

We show that Poincaré polarization singularities, spiraling like a tornado, can be generated by superimposing two orthogonally polarized, abruptly auto-focusing ring-Airy beams that carry orbital angular momentum (OAM). Seeded by phase vortices of the same helicity, which are adapted to the high-intensity rings of one of the superimposing beams, these polarization singularities follow trajectories that twist and shrink in an accelerating fashion along their propagation. Reaching angular acceleration that exceeds 120 rad/mm2, these Poincaré tornados can find application in singular optics, wavefront shaping, polarization engineering, and imaging through complex media.

An optimum design of a ring Airyprime beam array based on dimensionless eccentric position

The beam array with abruptly autofocusing capability weakens the turbulence effect in free space optical (FSO) communication systems with relatively low complexity, thereby improving the communication quality of FSO communication systems. Based on the perspective of dimensionless eccentric position B, the design of a ring Airyprime beam array (RAPBA) is optimized to achieve the strongest autofocusing capability. When B increases from zero, the autofocusing capability of a RAPBA first increases, then reaches a maximum value, and finally decreases. With given the exponential decay factor a, an optimum value of B under which the autofocusing capability is the strongest is searched out. With the decrease of a, the optimum value of B increases. When a = 0.05, the autofocusing capability of a RAPBA with the optimum B is enhanced by 373.66 % compared with the maximum autofocusing capability of a circular Airyprime beam, while the corresponding focal length is only shortened by 4.73 %. Also, we construct a concise experimental optical setup for the acquisition and the measurement of a RAPBA. The measured results support the theoretical predictions. The physical logical principles underlying the autofocusing capability and the dimensionless eccentric position is interpreted. This research offers a novel approach for an optimum design of a RAPBA with the strongest autofocusing capability. A similar variation pattern of autofocusing capability and dimensionless eccentric position exists in a ring Airy beam array (RABA). Accordingly, our proposed scheme is also suitable for the optimum design of a RABA.

Spin-orbit coupling induced polarization transform in the autofocusing of ring Airy beams with hybrid polarizations.

Manipulating polarization is of significance for the application of light. Spin-orbit coupling provides a prominent pathway for manipulating the polarization of light field but generally requires tight focusing conditions or anisotropic media. In this paper, we construct ring Airy beams with hybrid polarizations and reveal the controllable polarization transforms in their autofocusing dynamics by manipulating concomitant spin-orbit coupling in free space. The numerical and experimental results show that the polarization transform is dependent on the azimuthal orders of amplitude and vortex phases of two spin constituents of ring Airy beams, that the focal spots present pure linear polarization whose orientation is determined by the initial phase when the vortex phase topological charge is equal to the amplitude angular factor, otherwise, the focal fields present cylindrical vector polarizations whose orders depend on the difference of amplitude angular orders and topological charges. Our work provides new insights for studying spin-orbit interactions and the depolarization of complex polarization.

Generation of a modulated versatile spiral beam with varying intensity distribution along the propagation.

A new type of versatile spiral beam (VSB) is generated based on the competition mechanism between the self-focusing property of ring Airy beam and metalens phase distribution, which exhibits twisted properties and optical bottle structure along the propagation direction. The number of spiral lobes, rotation direction, shape and magnification times on the cross section of the proposed beam can be customized by flexibly tuning diffraction distance, topological charge and constant parameter. Therefore, the VSB can be viewed as tunable three-dimensional (3D) spiral beam, and our scheme has the superiority with more diverse and tunable intensity distribution. The properties of intensity distribution variation depended on the propagation distance and topological charge are demonstrated convincingly by employing the Poynting vector intuitive presentation the energy flow. The VSBs with the aid of above-mentioned properties are beneficial for guiding microparticles along the designed spiral path and capturing multiple microparticles into the closed dark regions. Finally, the modulated spiral beams are implemented as tool for particle manipulation in the three dimensional space to demonstrate the advantages of the modulated spiral beam and we can observe the stable trapping of the particles.

Optical vortices shape optical tornados.

We demonstrate that by seeding an accelerating ring-Airy beam with a finite number of off-axis optical vortices, it transforms into a tornado wave (ToW) upon propagation. Using numerical simulations, we show that both the spiraling high-intensity lobes and the optical vortices exhibit angular acceleration and follow interwinding braid-like trajectories. Likewise, we study the effect of the number, position, and topological charge of the vortices on the propagation dynamics and reveal the connection between optical vortices and optical tornados.

Stabilization of Axisymmetric Airy Beams by Means of Diffraction and Nonlinearity Management in Two-Dimensional Fractional Nonlinear Schrödinger Equations

The propagation dynamics of two-dimensional (2D) ring-Airy beams is studied in the framework of the fractional Schrödinger equation, which includes saturable or cubic self-focusing or defocusing nonlinearity and Lévy index ((LI) alias for the fractionality) taking values 1≤α≤2. The model applies to light propagation in a chain of optical cavities emulating fractional diffraction. Management is included by making the diffraction and/or nonlinearity coefficients periodic functions of the propagation distance, ζ. The management format with the nonlinearity coefficient decaying as 1/ζ is considered too. These management schemes maintain stable propagation of the ring-Airy beams, which maintain their axial symmetry, in contrast to the symmetry-breaking splitting instability of ring-shaped patterns in 2D Kerr media. The instability driven by supercritical collapse at all values α<2 in the presence of the self-focusing cubic term is eliminated, too, by the means of management.

Dependence of autofocusing ability of a ring Airyprime beams array on the number of beamlets.

A ring Airyprime beams (RAPB) array, which consists of N evenly displaced Airyprime beamlets in the initial plane, is first introduced, to the best of our knowledge, in this Letter. Here, we focus on the effect of the number of beamlets N on the autofocusing ability of the RAPB array. With the given beam parameters, an optimal number of beamlets, which is the minimum number of beamlets to realize the saturated autofocusing ability, is selected. The focal spot size of the RAPB array remains unchanged before the number of beamlets reaches the optimal number of beamlets. More importantly, the saturated autofocusing ability of the RAPB array is stronger than that of the corresponding circular Airyprime beam. The physical mechanism of the saturated autofocusing ability of the RAPB array is interpreted by simulating the Fresnel zone plate lens. The influence of the number of beamlets on the autofocusing ability of the ring Airy beams (RAB) array under the same beam parameters with the RAPB array is also presented for comparison. Our findings are beneficial for the design and application of the ring beams array.

Sum-frequency generation of ring-Airy beams

Sum-frequency generation of ring-Airy beams

Broadband generation of abruptly autofocusing terahertz ring-Airy beams with all-silicon metasurface

Abruptly autofocusing terahertz (THz) ring-Airy beam has been generated by transmissive plasmonic metasurface at a single frequency in the earlier work. However, the transmission efficiency of it is low. Based on the waveguide effect, a design strategy for broadband generation of THz ring-Airy beams with transmissive all-silicon metasurface is proposed in this paper, which has an improved transmission efficiency and is more favorable in fabrication. Under the linearly polarized plane wave incidence, the amplitude and phase of the cross-polarized transmitted beam can be simultaneously modulated by controlling the rotation angles of the identical rectangular silicon pillars arranged on the silicon substrate. A polarization-independent antireflection square silicon pillar array is also proposed to be patterned at the other side of the substrate. The metasurface promises a working bandwidth from 2.12 to 2.72 THz with the overall transmission efficiency being over 51.18% (the highest transmission efficiency is up to 77.57% at 2.52 THz). The peak intensity positions of the generated beam during the propagation follow a parabolic trajectory. For the generated ring-Airy beam, the focal length is positively proportional to the frequency, while the abruptly autofocusing property and full width at half maximum (FWHM) of the focus are positively and negatively related with the frequency, respectively. This work can be expected to facilitate the applications of terahertz wave in biomedicine and manipulation of particles.

Propagation characteristics of the blocked terahertz ring-Airy beam generated by all-silicon metasurface

Based on the all-silicon metasurface, we study the propagation characteristics of the abruptly autofocusing terahertz (THz) ring-Airy beam when its primary ring is blocked. Identical rectangular silicon pillars with meticulously designed rotation angles are arranged on a silicon substrate to shape the incident linearly polarized plane wave into a cross-polarized blocked ring-Airy beam. The transmission efficiency of the metasurface can be up to 77.57% since a polarization-independent square silicon pillar array is patterned at the other side of the substrate to suppress the reflection loss. Compared to the ring-Airy beam, the abruptly autofocusing property of the blocked ring-Airy beam is promoted since the intensity contrast at the focus is greatly enhanced. In addition, the focus of the blocked ring-Airy beam is smaller and the focus position of it slightly moves forward. The principle feasibility of the metasurface and influences of imperfections on the propagation characteristics of the generated blocked ring-Airy beam are also discussed. Our study is expected to be of great significance for applying THz waves in manipulation of particles and biomedicine.

Propagation properties of ring Airy beams array in a nonlinear media

The control of lasers is one of the most important subjects in optics. In this paper, we investigate the propagation behavior of three ring Airy beams (RABs) with an equilateral triangle arrangement. The visualized intensity distribution of RABs array exhibits two types of autofocus: 1. sudden autofocus, which can be applied in producing laser bullets; 2. triangle autofocus, which can be used as laser-tweezers. The properties of laser bullets are investigated. The results reveal that the center intensity (position) of laser bullets increases (decreases) in a power-law way versus initial RABs' intensity. Moreover, we discuss the range of parameters to produce laser-tweezers with the best quality. Since the position and power of the RABs-bullet and RABs-tweezers can be controlled with high precision, it has important application value in many fields such as laser targeted therapy of cancers, manipulation of microscopic objects, photoresist technology in chips and so on.

Abruptly autofocusing polycyclic tornado ring Airy beam

We introduce numerically a new polycyclic tornado ring Airy beam (PTRAB) induced by annular spiral zone phases with the second order chirped factor. The PTRAB has such properties of controllable multi focuses, the multi optical bottles and rotation. By choosing appropriate parameters, we can control the times of the multi autofocus and the autofocusing distance, the size and the number of the OBs, the quantity of the spots and the location where the rotary direction changes from counterclockwise to clockwise. We believe our results have potential applications in laser energy focusing, optical tweezers, optical spanners and manufacturing tunable chiral meta-materials.

Autofocusing of ring Airy beams embedded with off-axial vortex singularities.

We report the autofocusing behaviors of ring Airy beams (RABs) embedded with two kinds of off-axial vortex singularities. The influences of embedded positions and topological charges of point and r vortices on the autofocusing dynamic are numerically and experimentally investigated. The results show that, for the first-order vortex, the embedded position significantly affects the focal field, and once the singularity is located on the main ring of RAB, the symmetric Bessel profile of the focal field will be broken, otherwise the Bessel-like focus can self-heal at the focal plane. However, for the higher-order vortex embedded near the main ring, it will split into several fundamental vortices and then separate with each other along the radial direction under the interaction with the RAB background. Our results hold potential for the practical application of RABs in the atmosphere and other propagation systems with perturbation and even singularities.

Dual optical trap created by tightly focused circularly polarized ring Airy beam

The dual focus property of focused circularly polarized ring Airy beam (RAB) under the action of tightly focused lens is demonstrated in this paper. The radiation forces at two foci of tightly focused RAB are calculated, the numerical results show that the particle could be longitudinally and transversely trapped at the two foci. By varying corresponding parameters, we could control the property of two traps. The trapping force increases with NA and the scaling parameter w; and an appropriate initial radius r0 is necessary for the enhancement of either trap. The two traps could move closer as w increases or r0 decreases. To realize the dual optical trap, we should choose a smaller decaying parameter a and a larger NA, or the dual optical trap would degenerate into a single optical trap. Moreover, because of the influence of the Brownian motion and the scattering force, the size of the particle should be in a special range.

Tornado waves

We show that light spiraling like a tornado can be generated by superimposing abruptly auto-focusing ring-Airy beams that carry orbital angular momentum of opposite handedness. With different parabolic propagation trajectories, the superimposing ring-Airy beams are tailored to abruptly auto-focus at overlapping focal regions. This results in a complex wave with intense lobes that twist and shrink in an accelerating fashion along propagation. By achieving angular acceleration values that exceed 295 rad / mm 2 , these tornado waves can find numerous applications in laser trapping, direct laser writing, and high-harmonic generation.

Funnel beams in the defocusing nonlinear media

The dynamics of the inward-focusing ring Airy beam in the defocusing nonlinear media is investigated. It is found an interesting phenomenon that the propagation of the inward-focusing ring Airy beam exhibits a “funnel” when the beam intensity is sufficiently high. Additionally, the focus spot of such a funnel beam monotonously changes with the nonlocality of the media. The gradient force of the funnel beam is also studied in detail. The findings may pave the way to the optical tweezers in the nonlinear regime.

Bottle Beams in Nonlocally Defocusing Nonlinear Media

The dynamics of the inward-focusing ring Airy beam in nonlocally defocusing nonlinear media is investigated in detail, and a bottle beam shape can be observed by adjusting the amplitude of the inward-focusing ring Airy beam and the nonlocality of the media. The gradient force of the bottle beam is numerically studied. It is worth mentioning that the bottle beams are formed in the nonlinear regime, which indicates that much higher intensity is allowable for these beams than those in the linear regime. Our approach and results may pave the way to the optical tweezers in the nonlinear regime.

Transformation of ring-Airy beams during efficient harmonic generation.

We theoretically study the evolution of ring-Airy beams during harmonic generation with the focus on the regime of pump energy depletion. We demonstrate that in this regime, ring-Airy beams still preserve their abrupt autofocusing properties, while transforming to a multiple ring-Airy structure. A similar transformation is observed on the beam of the generated harmonic. We suggest a simple analytical model that explains and predicts with precision our numerical findings.

Terahertz wave generation from ring-Airy beam induced plasmas and remote detection by terahertz-radiationenhanced- emission-of-fluorescence: a review

With the increasing demands for remote spectroscopy in many fields ranging from homeland security to environmental monitoring, terahertz (THz) spectroscopy has drawn a significant amount of attention because of its capability to acquire chemical spectral signatures non-invasively. However, advanced THz remote sensing techniques are obstructed by quite a few factors, such as THz waves being strongly absorbed by water vapor in the ambient air, difficulty to generate intense broadband coherent THz source remotely, and hard to transmit THz waveform information remotely without losing the signal to noise ratio, etc. In this review, after introducing different THz air-photonics techniques to overcome the difficulties of THz remote sensing, we focus mainly on theoretical and experimental methods to improve THz generation and detection performance for the purpose of remote sensing through tailoring the generation and detection media, air-plasma.

Tailoring the focal region of abruptly autofocusing and autodefocusing ring-Airy beams

We theoretically study the properties of the focal region of abruptly autofocusing and, their variant, autodefocusing ring-Airy beams, under the action of a conical phase gradient. By expanding the analysis of 1D Airy beams to cylindrically symmetric Airy beams, we derive analytic formulas for the position and dimensions of the focus. Our analysis covers in a unified way both beam types, and numerical simulations over a broad parameters range are in excellent agreement with our theoretical predictions. Our results allow the tailoring of the focal region both in size and in position by tuning the initial parameters.