Chen Wang, Yuan Ren
We apply the CP to CAVs for the first time experimentally. Firstly, we introduce the propagation properties of a CAV with the LOCP in the process of measuring TCs, and measure the TCs of CAVs in the self-focusing areas experimentally. Secondly, we shape the CAVs via the HOCP and discuss the manipulaiton of singularities.
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Propagation-invariant vortex Airy beam whose singular point follows its main lobe
本研究提出一种由艾里光束与其横向剪切光束π/2相移叠加而成的新型涡旋艾里光束，其奇点跟随主瓣、传输稳定，轨道角模纯度较传统类型最高提升10%，有望在多领域开辟新应用方向。
We study the self-focusing dynamics and collapse of vortex Airy optical beams in a Kerr medium. The collapse is suppressed compared to a non- vortex Airy beam in a Kerr medium as a result of the existence of vortex fields. The locations of collapse depend sensitively on the initial power, vortex order, and modulation parameters. Unlike the collapses reported before for any beam, the collapse may occur in a position where the initial field is nearly zero while no collapse appears in the region where the initial field is mainly distributed. This study sheds light on how to control and manipulate…
In this paper, we experimentally demonstrate reversible wavefront shaping through mimicking gravitational field. A gradient-index micro-structured optical waveguide with special refractive index profile was constructed whose effective index satisfying a gravitational field profile. Inside the waveguide, an incident broad Gaussian beam is firstly transformed into an accelerating beam, and the generated accelerating beam is gradually changed back to a Gaussian beam afterwards. To validate our experiment, we performed full-wave continuum simulations that agree with the experimental results. Furth…
We present the experimental generation and analysis of both the intensity and phase of an optical vortex beam originating from a superposition of Airy-vortex beams. A new theoretical proposal is accessible to generate an array of Airy-vortex beams (AiVBs) from a superposition of N identical AiBs symmetrically located with respect to the propagation axis, where each beam is superimposed with OV and are characterized by the same topological charge l. Additionally, a single experimental apparatus enables both the optical generation and reconstruction of computer-generated holograms implemented on…
Needle-like electromagnetic fields has various advantages for the applications in high-resolution imaging, Raman Spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device(DMD). Such amplitude modulation technique is able to shape traditional Airy …
Complex vector modes represent a general state of light nonseparable in their spatial and polarization degrees of freedom, which have inspired a wide variety of novel applications and phenomena, such as their unexpected propagation behaviour. For example, they can propagate describing periodic polarization transitions, changing from one vector beam to another. Here, we put forward a novel class of vector modes with the capability to experience an abruptly autofocusing behaviour. To achieve such beams, we encode the spatial degree of freedom in the Circular Airy Gaussian vortex (CAGV) beams. We…
In this paper we perform a fusion between two important theoretical methodologies, one related to the Frozen Wave beams, which are non-diffracting beams whose longitudinal intensity pattern can be chosen a priori in an medium (absorbing or not), and the other related to the Airy-Type pulses, which are pulses resistant to dispersion effects in dispersive materials. As a result, a new method emerges, capable of providing vortex pulses resistant to three concomitant effects, i.e.: diffraction, dispersion and attenuation; while concurrently the spatial variation of the wave intensity along its axi…
We address the propagation of vortex beams with the circular Airy-Gaussian shape in a (2+1)-dimensional optical waveguide modeled by the fractional nonlinear Schrodinger equation. Systematic analysis of autofocusing of the beams reveals a strongly non-monotonous dependence of the peak intensity in the focal plane on the corresponding Levy index, with a strong maximum at alpha =1.4. Effects of the nonlinearity strength, the ratio of widths of the Airy and Gaussian factors in the input, as well as the beam vorticity, on the autofocusing dynamics are explored. In particular, multiple autofocusing…
We study circular Airy vortex beams (CAVBs) with two same or opposite point vortices symmetrically loaded on x-axis, inside, onside and outside of the main ring (The absolute value of topological charge is one). It is found that the loading position (denoted as dv) can significantly tune the auto-focusing behaviour. For two vortices with same signs, when dv is near zero, the double vortices approximately merge at the focal plane. But as dv increases, the merged vortices will gradually separate along the y-axis. When dv is large, the focal spot becomes Bessel-shaped pattern. For opposite vortic…
The dynamics of 3D Airy-vortex wave packets is studied under the action of strong self-focusing Kerr nonlinearity. Emissions of nonlinear 3D waves out of the main wave packets with the topological charges were demonstrated. Due to the conservation of the total angular momentum, charges of the emitted waves are equal to those carried by the parental light structure. The rapid collapse imposes a severe limitation on the propagation of multidimensional waves in Kerr media. However, the structure of the Airy beam carrier allows the coupling of light from the leading, most intense peak into neighbo…
We demonstrate curved modifications with lengths of up to 2 mm within borosilicate glass produced by single 1030 nm picosecond laser shots with an Airy beam profile. Plasma ignition in the side lobes of the beam as well as surface damage prove to be the crucial limitations for confined bulk energy deposition on a curved trajectory. A combined experimental and numerical analysis reveals optimum laser parameters for confined bulk energy deposition. This way we achieved single pass cutting of a 525 $μ$m thick glass sheet with a well defined convex edge down to a bending radius of 774 $μ$m.
We introduce axisymmetric Airy-Gaussian vortex beams in a model of an optical system based on the (2+1)-dimensional fractional Schrödinger equation, characterized by its Lévy index (LI). By means of numerical methods, we explore propagation dynamics of the beams with vorticities from 0 to 4. The propagation leads to abrupt autofocusing, followed by its reversal (rebound from the center). It is shown that LI, the relative width of the Airy and Gaussian factors, and the vorticity determine properties of the autofocusing dynamics, including the focusing distance, radius of the focal light spot, a…
With Rytov approximation theory, we derive the analytic expression of detection probability of Airy vortex beam carrying orbital angular momentum (OAM) through an anisotropic weak oceanic turbulence. We investigate the influences of turbulence parameters and beam parameters on the propagation properties of Airy-OAM beam. The numerical simulation results show that the anisotropic oceanic turbulence with a lower dissipation rate of temperature variance, smaller ratio of temperature and salinity contributions to the refractive index spectrum, higher dissipation rate of kinetic energy per unit mas…
In this letter, we introduce a new class of light beam, the circular symmetric Airy beam (CSAB), which arises from the extensions of the one dimensional (1D) spectrum of Airy beam from rectangular coordinates to cylindrical ones. The CSAB propagates at initial stages with a single central lobe that autofocuses and then defocuses into the multi-rings structure. Then, these multi-rings perform the outward accelerations during the propagation. That means the CSAB has the inverse propagation of the abruptly autofocusing Airy beam. Besides, the propagation features of the circular symmetric Airy vo…
We have investigated the propagation dynamics of the circular Airy Gaussian vortex beams (CAGVBs) in a (2+1)-dimesional optical system discribed by fractional nonlinear Schrödinger equation (FNSE). By combining fractional diffraction with nonlinear effects, the abruptly autofocusing effect becomes weaker, the radius of the focusing beams becomes bigger and the autofocusing length will be shorter with increase of fractional diffraction Lévy index. It has been found that the abruptly autofocusing effect becomes weaker and the abruptly autofocusing length becomes longer if distribution factor of …
According to Rytov approximation theory, we derive the analytical expression of the detection probability of the autofocusing Airy beam (AAB) with powerexponent-phase carrying orbital angular momentum (OAM) mode, AAB-PEPV. We analyze the influence of oceanic turbulence on the propagation characteristics of the AAB-PEPV. The results show that the AAB-PEPV beam has a higher detection probability at the receiver when the anisotropic ocean turbulence has a larger unit mass fluid dynamic energy dissipation rate, a larger internal ratio factor, and a higher anisotropy factor. At the same time, the d…
Evolutions of ring Airy vortex beam and ring Pearcey vortex beam in turbulent atmosphere and a comparative analysis of their channel efficiencies and OAM spectra
该研究对比了环形Airy涡旋光束与环形Pearcey涡旋光束在不同强度湍流大气中复用/非复用场景下的传输特性，分析了信道效率与OAM谱差异，为湍流环境下的OAM光通信提供参考。
In this article we propose a new type of optical vortex, the X-type vortex. This vortex inherits and develops the conventional noncanonical vortex, i.e., it no longer has a constant phase gradient around the center, while the intensity keeps invariant azimuthally. The strongly focusing properties of the X-type vortex and its effect on the beam shaping in three-dimensional (3D) fields are analyzed. The interesting phenomena, which cannot be seen in canonical vortices, are observed, for instance the 'switch effect' which shows that the intensity pattern can switch from one transverse axis to ano…
Increasing demand for practical applications is forcing deeper research into optical vortices (OVs): from the generation and measurement to shaping and multiple singularities manipulation of OVs. Herein, we propose a new type of phase structure called the high-order cross phase (HOCP) can be employed to modulate OVs to implement both polygonal shaping and singularities manipulation. Theoretically, we investigate the propagation characteristics of OVs with the HOCP. In experiments, we achieve the shaping and singularities manipulation of OVs by utilizing the HOCP. On this basis, we discuss the …
We investigate a method for the measurement and shaping of a perfect optical vortex (POV) by using the cross-phase for the first time. Experimentally, we propose a method to measure the topological charges +3 and +-5 of POVs with the low-order cross-phase (LOCP) at the Fourier plane; we realize shaping intensity distributions of POVs at the Fourier plane with the high-order cross-phase (HOCP) and show the asymmetric modulation ability of the HOCP for an optical field. Furthermore, we discuss the influence of parameters on the optical field in the shaping process. On this basis, we propose a se…
The focal field properties of radially/azimuthally polarized Zernike polynomials are studied. A method to design the pupil field in order to shape the focal field of radially or azimuthally polarized phase vortex is introduced. With this method, we are able to obtain a pupil field to achieve a longitudinally polarized hollow spot with a depth of focus up to $12λ$ and $0.14λ$ lateral resolution for a optical system with numerical aperture 0.99; A pupil field to generate 8 circularly polarized focal spots along the optical axis is also obtained with this method.
Dynamic generation of obitial angular momentum (OAM) of light has enabled complex manipulation of micro-particles, high-dimension quantum entanglement and optical communication. We report an analog vortex transmitter made of one bilaterally symmetric grating and an aperture, emitting optical vortices with the average OAM value continuously variant in the entire rational range. Benefiting from linearly-varying transverse dislocation along its axis of symmetry, this diffractive transmitter possesses extra degree of freedom in engineering broadband optical vortices meanwhile preserving a novel sp…
We have experimentally and theoretically shown that the circularly polarized beam bearing singly charged optical vortex propagating through a uniaxial crystal can be split after focusing into the radially and azimuthally polarized beams in vicinity of the focal area provided that the polarization handedness and the vortex topological charge have opposite signs. Quality of the polarization structure can reach unity.
Non-symmetrical vortex beam shaping in VECSEL laser arrays
提出一种在简并垂直外腔面发射激光器中生成非对称涡旋光束的新方法，通过二元振幅掩模控制激光阵列间的复耦合与相移，并推广了Henry因子公式以覆盖复耦合情况。
Square-shaping of sturdy optical vortex droplets in quasi-phase-matched photonic crystals
本文提出在准相位匹配光子晶体中，利用竞争非线性和方形几何约束，实现方形涡旋液滴的稳定形成，揭示涡旋稳健性不依赖圆对称的普适性。
We address vortex solitons supported by optical lattices featuring modulation of both the linear and nonlinear refractive indices. We find that when the modulation is out-of-phase the competition between both effects results in remarkable shape transformations of the solitons which profoundly affect their properties and stability. Nonlinear refractive index modulation is found to impose restrictions on the maximal power of off-site solitons, which are shown to be stable only below a maximum nonlinearity modulation depth.
We report the fabrication of large-area phase masks on thin fused-silica substrates that are suitable for shaping multi-terawatt femtosecond laser beams. We apply these phase masks for the generation of intense femtosecond optical vortices. We further quantify distortions of the vortex beam patterns that result from several common types of mask defects.
Propagation of circular Airy derivative beams in complex media
本文通过实验与数值模拟研究圆艾里导数光束在湍流复杂介质中的突然自聚焦特性，证明其相较高斯光束具有更强的抗湍流畸变与聚焦能力。
Quantum vortices are the analogue of classical vortices in optics, Bose-Einstein condensates, superfluids and superconductors, where they provide the elementary mode of rotation and orbital angular momentum. While they mediate important pair interactions and phase transitions in nonlinear fluids, their linear dynamics is useful for the shaping of complex light, as well as for topological entities in multi-component systems, such as full Bloch beams. Here, setting a quantum vortex into directional motion in an open-dissipative fluid of microcavity polaritons, we observe the self-splitting of th…
Intense X-ray Vortices Generation via Wavefront Shaping in high-gain Free-Electron Lasers
提出一种在高增益自由电子激光器中通过调整波前倾斜产生强X射线涡旋光束的简单方法，无波长限制，可放大至饱和。
Optical holography has undergone rapid development since its invention in 1948, but the accompanying speckles with randomly distributed intensity are still untamed now due to the fundamental difficulty of eliminating intrinsic fluctuations from irregular complex-field superposition. Despite spatial, temporal and spectral averages for speckle reduction, it is extremely challenging to reconstruct high-homogeneity, edge-sharp and shape-unlimited images via holography. Here we predict that holographic speckles can be removed by narrowing the probability density distribution of encoded phase to hom…
In-situ integrated nonlocal Huygens metasurfaces enable robust vortex beams from multimode fibers
该研究将硅非局域惠更斯超表面原位集成到多模光纤端面，无需预补偿即可将散斑图案转为涡旋光束，提升了抗光纤扰动的鲁棒性，为多模光纤结构光应用提供了紧凑平台。
Turbulence Impacted Wavefront Corrections Using Beam Modulation Technique
本文提出一种利用涡旋相位板与伪随机相位板的光束整形技术，通过实验测量不同拓扑荷LG光束的闪烁指数，以抑制Kolmogorov型湍流影响并实现波前校正。
Accurate and Noise-Robust Wavefront Reconstruction with an Optical Vortex Wavefront Sensor
本文提出在Shack-Hartmann波前传感器子孔径中引入光学涡旋，通过专用跟踪算法在宽信噪比范围内降低残余相位方差，实现精确抗噪的波前重建，无需根本性重新设计。
High-fidelity holographic beam shaping with optimal transport and phase diversity
本文提出利用最优传输和相位多样性技术实现高保真光束成形，提升SLM相位计算的准确性和效率。
In TEM, a typical goal consists of making a small electron probe in the sample plane in order to obtain high spatial resolution in scanning transmission electron microscopy. In order to do so, the phase of the electron wave is corrected to resemble a spherical wave compensating for aberrations in the magnetic lenses. In this contribution we discuss the advantage of changing the phase of an electron wave in a specific way in order to obtain fundamentally different electron probes opening up new application in the (S)TEM. We focus on electron vortex states as a specific family of waves with an a…
Temporal modulation of the quantum vacuum through fast motion of a neutral body or fast changes of its optical properties is known to promote virtual into real photons, the so-called dynamical Casimir effect. Empowering modulation protocols with spatial control could enable to shape the spectral, spatial, spin, and entanglement properties of the emitted photon pairs. Space-time quantum metasurfaces have been proposed as a platform to realize this physics via modulation of their optical properties. Here, we report the mechanical analog of this phenomenon by considering systems whose lattice str…
Orbital-angular-momentum dependent speckles for spatial mode sorting and multiplexed data transmission
本文研究涡旋光束透过毛玻璃散射片后形成的OAM依赖散斑，发现互相关环带尺寸由拓扑荷差决定，并据此实现OAM模式分选及OAM编码数据传输解复用。
Metasurfaces are engineered thin surfaces comprising two dimensional (2D) arrays of sub-wavelength spaced and sub-wavelength sized resonators. Metasurfaces can locally manipulate the amplitude, phase and polarization of light with high spatial resolution. In this study, we report numerical and experimental results of a vortex-beam-generating metasurface fabricated specifically for infrared (IR) and terahertz (THz) wavelengths. The designed metasurface consisted of a 2D array of dielectric cross-shaped resonators with spatially varying length, thereby providing desired spatially varying phase s…
A plane-wave approximation in particle physics implies that a width of a massive wave packet $σ_{\perp}$ is much larger than its Compton wavelength $λ_c = \hbar/mc$. For Gaussian beams or for packets with the non-singular phases (say, the Airy beams), corrections to this approximation are attenuated as $λ_c^2/σ_{\perp}^2 \ll 1$ and usually negligible. Here we show that this situation drastically changes for particles with the phase vortices associated with an orbital angular momentum $\ell\hbar$. For highly twisted beams with $|\ell| \gg 1$, the non-paraxial corrections get $|\ell|$ times enha…
Ray Optics Approach to Holography
针对相位恢复中涡旋形成导致现有方法无法收敛的问题，提出基于最优传输的高效算法，规避相位涡旋并实现精度与效率的最优解，还揭示了其与射线光学极限的理论联系并在量子学习框架下重述问题，为相位恢复和激光束整形提供工具。
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