Superposition Of Vortices Research Articles

Study of some components of the influence and formation of blood flow in patients with "slow flow".

"Slow flow" is one very important concept in modern fundamental and clinical biomedicine. Slow coronary flow is indicative of delayed filling of the terminal coronary artery vessels, occurring in the absence of significant coronary stenosis. This group patient of patients exhibits a high incidence of disability and represents a significant financial and material burden for the state and the healthcare system in general. The primary objective of our study was to examine patients with slow coronary flow. We studied the standard parameters recommended by the international health care system (electrocardiography (by Medica QRS-12, Germany), through the electrical activity of a patient's heart by the electrical impulses (beating) of the heart; HC1(Germany); coagulogramma by Coatron M1 (Germany), troponin by AQT 90 (Germany); general blood test we used automatic human counting device HC1(Germany). Also, we investigate the original parameters (non-standard parameters, which we use in this pilot study) that we were first studied for this diagnosis and non-standard parameters. A general blood test showed that patients with slow flow had a higher blood leukocyte count than the control group, but the amount of hemoglobin was normal, the hematocrit was much higher than in the control group, and the platelet count was close to the lower limit of clinical standards.We obtained details of blood flow by coagulation situation, such as prothrombin time, prothrombin index, international normalized ratio, activated partial thromboplastin time, thrombin time, fibrinogen, and rheological properties such as index of erythrocyte aggregability, index of erythrocyte deformability, plasma viscosity, in silico blood rheological index. Blood flow can be considered as a superposition of vortices with similar frequencies and wave vectors that change after bifurcations or other obstacles in the vascular network. These factors together determine the conditions for structuring the flow of moving blood. Disruption or alteration of these factors results in slow flow. It has been found that the speed of blood flow in the coronary arteries depends on changes in the number and function of red blood cells. Slow flow is directly influenced by the aggregation and deformation of red blood cells, their number, and plasma viscosity. Consequently, the rheological status plays a crucial role in determining blood flow and its velocity.

Where is the orbital angular momentum in vortex superposition states?

In this paper, we explore the distribution of the orbital angular momentum (OAM) in the coaxial vortex superposition states based on the independent propagation principle of light in this interference process. We find that in this case, some specific singular points exist in the spatial intensity distribution. The first type of singular point is located at the center point of the spatial intensity distribution. The second type of specific singular point is at the critical location of the overlapping area in angular direction. By analogy with the angular momentum superposition of two axially rotating homogeneous disks with different radius in rigid body, We present a suggestion: the center point is located at the overlapping area of all the superposed components. Therefore, the topological charge value in the center point should be doubled by the actual number of superposition field components. The singular point at the critical location of the overlapping area in angular direction should also be co-owned by the superposition components outside the position of the ring (including the corresponding component of the ring). The total OAM is exactly equal to the sum of those two types contained in the superposition states, which is equal to the input OAM of the superposition state components. The conservation of the OAM in the coaxial interference process is demonstrated.

Spin Angular Momentum at the Focus of a Superposition of an Optical Vortex and a Plane Wave with Linear Polarizations

In this paper, tight focusing of a superposition of a vortex laser beam with topological charge n with linear polarization and a plane wave with the same linear polarization directed along the horizontal axis is considered. Using the Richards–Wolf formalism, analytical expressions are obtained for the intensity distribution and longitudinal projection of the spin angular momentum in the focal plane. It is shown that for even and odd numbers n, the intensity and the spin angular momentum have different symmetries: for even n they are symmetric about both Cartesian axes, and for odd n they are symmetric only about the vertical axis. The intensity distribution has n local maxima at the focus, and it is nonzero on the optical axis for any n. The distribution of the longitudinal spin angular momentum (spin density) in the focal plane has (n + 2) subwavelength regions with a positive spin angular momentum and (n + 2) regions with a negative spin angular momentum, the centers of which alternately lie on a circle of a certain radius with a center on the optical axis. This spin distribution with different signs demonstrates the spin Hall effect at the focus. Negative and positive spins are mutually compensated, and the total spin is equal to zero at the focus. We have shown that by changing the topological charge of the optical vortex, it is possible to control the spin Hall effect at the focus, that is, to change the number of regions with spins of different signs.

Manipulation of plasmonic vortex fields using positive elliptically polarized beams

Several studies have investigated methods for the direct excitation of surface plasmon polariton (SPP) vortex fields by using scalar beams with linear and circular polarization. In this paper, we propose novel devices for generating SPP vortex fields by using positive elliptically polarized beams. These devices excited SPP vortices with a uniform electric field intensity distribution, that did not vary arbitrarily with changes in the incident beam amplitude ratio. Moreover, when the incident scalar beam was transformed into a vector beam with different amplitude ratios at every point in space, the topological charge of the SPP vortex field could be dynamically modulated by changing the polarization order and rotation direction of the incident vector beam. The fields generated by different structures after the superposition of SPP vortices had spatial intensity distributions that varied with changes in the incident beam amplitude ratio. These properties provide a new idea for realizing different spatial intensity distributions for a dynamic modulation SPP field.

Optical Logic Gates Excited by a Gauss Vortex Interference Beam Based on Spatial Self-Phase Modulation in 2D MoS2.

Vortex beams with optical orbital angular momentum have broad prospects in future high-speed and large-capacity optical communication. In this investigation of materials science, we found that low-dimensional materials have feasibility and reliability in the development of optical logic gates in all-optical signal processing and computing technology. We found that spatial self-phase modulation patterns through the MoS2 dispersions can be modulated by the initial intensity, phase, and topological charge of a Gauss vortex superposition interference beam. We utilized these three degrees of freedom as the input signals of the optical logic gate, and the intensity of a selected checkpoint on spatial self-phase modulation patterns as the output signal. By setting appropriate thresholds as logic codes 0 and 1, two sets of novel optical logic gates, including AND, OR, and NOT gates, were implemented. These optical logic gates are expected to have great potential in optical logic operations, all-optical networks, and all-optical signal processing.

On the interaction of electroconvection at a membrane interface with the bulk flow in a spacer-filled feed channel

The operational range of electro-driven processes can be extended by (i) reducing diffusion resistances at the membrane/electrolyte interface using spacers and (ii) by electroconvective mixing of the boundary layer at overlimiting current densities. Although many studies have addressed each of these phenomena separately, the details of the interplay of spacer-engineered hydrodynamics and electroconvection are unexplored. In this study, we establish a methodology of a new membrane cell design and the use of a high-speed microparticle tracking velocimetry setup for direct observation and quantification of the 3D velocity field in a spacer-filled electrodialysis channel under process conditions relevant for real electrodialysis applications, i.e., overlimiting currents and elevated Reynolds. We unravel details of the superposition of electroconvective vortices and forced flow velocity with and without an inserted spacer. Overall, the forced flow flattens the vortex structure of electroconvection at increasing Reynolds numbers. In terms of vortex heights, a spacer with intentional dead zones outperforms a commercial spacer that decreases the boundary layer thickness. This study suggests a counter-intuitive spacer design: to exploit electroconvection, an engineered spacer design for maximum use of electroconvection in the far overlimiting region should aim to create intentional regions of low flow velocity.

Generation of V-point polarization singularity using single phase encoding with a spatial light modulator

A liquid crystal Spatial Light Modulator (SLM) can be used in various ways to produce vector-vortices. Superposition of scalar vortices with orthogonal polarization is a common approach, while a more recent technique is to use dual-phase modulation. These approaches require modulation of at least two phase patterns with a SLM or multiple SLMs. In this paper, we propose a novel technique to produce vector-vortices by modulating orthogonal light components through a single phase pattern with a SLM. It does not require interferometric setups, and simplifies the generation of light beams with V-point polarization singularities. Because of compact and robustness of our experimental setup, it can be easily integrated to any device for applications of vector-vortices.

Topological charge of superposition of optical vortices described by a geometric sequence

Here, we investigate coaxial superpositions of Gaussian optical vortices that can be described by a geometric sequence. For all superpositions analyzed, a topological charge (TC) is derived. In the initial plane, the TC can be either integer or half-integer, acquiring an integer value upon free-space propagation of the light field. Generally, the geometric sequence of optical vortices (GSOV) has three integer parameters and one real parameter. Values of these four parameters define the TC of the GSOV. Upon free-space propagation, the intensity pattern of the GSOV is not conserved, but can have intensity petals whose number is equal to one of the four beam parameters. If the GSOV has a unit real parameter, all constituent angular harmonics in the superposition have the same weight. In this case, the TC of the superposition is equal to the average index of the constituent angular harmonics. For instance, if the TC of the first and of the last angular harmonics, respectively, equals k and n, then the total TC of the superposition in the initial plane will be (n + k) /2, becoming equal to n upon free-space propagation.

Numerical modeling for the characteristics study of a focusing ultrashort spatiotemporal optical vortex.

Spatiotemporal (ST) wave packet carrying pure transverse orbital angular moment (OAM) with subwavelength spatial size has attracted increasing attentions in recent years, which can be obtained by tightly focusing a linear superposition of ST vortices with different topological charges. In this work, numerical models are proposed to explore the impact of the pulse width of the ST vortex on the characteristics of its focal field. We demonstrate that the rigorous model for calculating the focused ST wave packet is essential for ultrashort optical pulse, while the simplified model has the advantage of high efficiency but can only provide credible results when the pulse width of the illumination is long enough. Specifically, when the pulse width decreases from 100 fs to 5 fs, the accuracy of the simplified model would decrease significantly from 99% to 65.5%. In addition, it is found that the pulse duration would still lead to the collapse of transverse OAM structure near the focus of a high numerical aperture lens, even though the ST astigmatism has already been corrected. To analyze the physical mechanism behind this distortion, Levenberg-Marquardt algorithm is adopted to retrieve the OAM distribution of the focal field. It is shown that the contributions from undesired OAM modes would become nontrivial for short pulse width, leading to the formation of the focal field with hybrid OAM structures. These findings provide insight for the focusing and propagation studies of ultrashort ST wave packets, which could have wide potential applications in microscopy, optical trapping, laser machining, nonlinear light-matter interactions, etc.

Conservation of the orbital angular momentum carried by superposition of optical vortices after passing through a sector diaphragm

In optical communications, it is desirable to know some quantities describing a light field, that conserve on propagation or resist to distortions. Typically, vortex beams are characterized by their orbital angular momentum (OAM) and topological charge (TC). Here, we show that the OAM of a single rotationally symmetric optical vortex is not affected by an arbitrary-shape aperture. For superposition of several optical vortices, we study what happens with its OAM behind a sector aperture. We discover that a specific sector angle does not violate the OAM carried by the superposition. The aperture half-angle should be equal to π multiplied by an integer number and divided by the greatest common divisor of all possible differences between the TCs. We show that such a sector aperture also conserves the orthogonality between the complex amplitudes of the constituent vortex beams. This property allows their effective demultiplexing after being distorted by such an aperture.

Orbital Angular Momentum of Superpositions of Optical Vortices Perturbed by a Sector Aperture

In optical communications, it is desirable to know some quantities describing a light field, which are conserved on propagation or resistant to some distortions. Typically, optical vortex beams are characterized by their orbital angular momentum (OAM) and/or topological charge (TC). Here, we show analytically that the OAM of a single rotationally symmetric optical vortex is not affected by an arbitrary-shape aperture or by other amplitude perturbations. For a superposition of two or several optical vortices (with different TCs), we studied what happens to its OAM when it is distorted by a hard-edge sector aperture. We discovered several cases when such perturbation does not violate the OAM of the whole superposition. The first case is when the incident beam consists of two vortices of the same power. The second case is when the aperture half-angle equals π multiplied by an integer number and divided by the difference between the topological charges. For more than two incident beams, this angle equals π multiplied by an integer number and divided by the greatest common divisor of all possible differences between the topological charges. We also show that such a sector aperture also conserves the orthogonality between the complex amplitudes of the constituent vortex beams. For two incident vortex beams with real-valued radial envelopes of the complex amplitudes, the OAM is also conserved, when there is a ±π/2 phase delay between the beams. When two beams with the same power pass through a binary radial grating, their total OAM is also conserved. We hope that these findings could be useful for optical communications since they allow for the identification of incoming optical signals by their OAM by registering only part of the light field within a sector aperture, thus reducing the cost of the receiving devices.

Orbital angular momentum of superpositions of optical vortices after passing through a sector diaphragm

In optical communications, it is desirable to know some quantities describing a light field, that are conserved on propagation or resistant to some distortions. Typically, optical vortex beams are characterized by their orbital angular momentum (OAM) and/or topological charge (TC). Here, we study what happens with the OAM of a superposition of two or several optical vortices (with different TCs) when it is distorted by a hard-edge sector aperture. We discover several cases when such perturbation does not violate the OAM of the whole superposition. The first case is when the incident beam consists of two vortices of the same power. The second case is when the aperture half-angle equals an integer number of π divided by the difference between the topological charges. For more than two incident beams, this angle equals an integer number of π divided by the greatest common divisor of all possible differences between the topological charges. For two incident vortex beams with real-valued radial envelopes of the complex amplitudes, the OAM is also conserved when there is a ±(pi)/2 phase delay between the beams. When two beams with the same power pass through a binary radial grating, their total OAM is also conserved.

Conservation of the Orbital Angular Momentum of a Superposition of Optical Vortices after Passing Through a Sector Diaphragm

Conservation of the Orbital Angular Momentum of a Superposition of Optical Vortices after Passing Through a Sector Diaphragm

Polarization-controlled generation and superposition of surface plasmon polariton vortices with a plasmonic metasurface

Optical vortex that carries orbital angular momentum has shown great potential in various applications, including high-density optical communication, quantum information, and manipulation of small particles. Here, an approach to design a plasmonic metasurface that can control both the generation and superposition of surface plasmon polariton (SPP) vortices is proposed and demonstrated. Under circularly polarized light incidence, the SPP vortices with different topological charges can be generated depending on the spin of the incidence, and the superposition state can be achieved when the polarization of incident light turns to linear polarization. Furthermore, it is demonstrated that the superposition of SPP vortices can be accurately controlled by the polarization states of the incidence. This proposed approach is quite versatile for generating and controlling SPP vortices and provides a feasible way to design miniaturized photonic devices for on-chip optical micromanipulation, sensing, and other related applications.

Analysis for vortex superposition state evolution of microcavity exciton polariton excited by ring-shaped pump

Owing to its light effective mass, polariton can easily realize Bose-Einstein condensates (BEC) and can also produce gyro effect under external drive. Therefore, it has a promising application prospect. Based on the Gross-Pitaevskii equation, the evolution of the exciton polaron BEC system in the annular microcavity is studied. Two key parameters affecting the characteristics of the exciton polaron system, namely the size of the microcavity and the configuration of the ring-shaped pumped beam, are investigated. The size of microcavity often directly affects the volume and power consumption of integrated devices. In addition, the number of coherent petals of exciton polariton superposition state matter wave propagated in microcavity is closely related to the precision and sensitivity of gyro, and the size of microcavity has a direct effect on the number of coherent petals. At the same time, whether the pumping region is continuous or not also has a key effect on the evolution of the system, and different pump configurations will affect the evolutions of the system. We find that in the microcavity radius on a micron scale, the annular microcavity can excite the petal of vortex superposition state when pumped by pumping light, and the petals can be stable, but circular cavity with a certain radius can “accommodate” a limited vortex quantum number, when vortex quantum number is too large, the system will be unstable and unable to support the formation of stable petals. However, with the increase of the radius of the annular microcavity, the superposition petal number of the exciton polariton system contained in the annular region will also increase, and the maximum petal number contained in the exciton polariton system has a positive linear correlation with the inner radius of the annular microcavity. At the same time, we find that when the pump laser configuration is changed, the system will evolve into a special form of steady state. The calculation results show that when microcavity parameters are the same but for only changing the radial width of single pump, the number of petals obtained is three times that before changing the radial width. In such a case, the number of superposition petals not only exceeds the previously calculated maximum number of petals accommodated by the annular cavity under the radius but also there appear the multiple petals combined radially. Under the double-ring pump system, changing the width of the hollow ring may produce not only the new exciton polariton condensation in the hollow ring, but also vortex states in the original petal. Under each of the three-ring and four-ring pumping condition, the evolution of the system finally presents a multi-petal state in the radial direction. Because these vortex superposition states contain the information about the density and the phase, it has important guiding significance for designing the new system of gyroscope. Therefore, these special evolutionary results open a new direction for studying the new system gyroscope.

Simultaneous measurement of cloud microphysical parameters based on digital holographic interferometry

Investigation of cloud microphysical is of great significance in deepening the understanding of the radiation energy budget, water cycle process, and precipitation mechanism, and improving the scientificity and effectiveness of artificial precipitation. Especially under the action of turbulence, in addition to shear and inertia, the turbulence in the cloud will accelerate the collision of cloud droplets through vortex superposition. The above process will further complicate the cloud microphysical characters. At present, the methods of measuring cloud microphysical parameters based on light scattering, collision and imaging theories encounter bottlenecks: the inversion process needs to make the assumptions about cloud droplet spectrum and particle characteristics, the impact process will destroy particle characteristics, and the three-dimensional characteristics of cloud particles cannot be obtained. Because of its many advantages, such as fast, real-time, non-destructive, non-invasive, high-resolution, full-field optical measurement, etc., in-line digital holographic interferometry is considered as a new potential tool for the dynamical measurement of cloud microphysical property. In particular, the mutual interference between the particle image and twin image is small under far-field recording conditions. In this paper, the measurement method of the on-line digital holographic interferometry based on interference theory, combining optical information processing, depth of field compression, and gray gradient variance technology of fusion holograms, is investigated. This method, with a <i>z</i>-axis position accuracy of 0.01 mm and system resolution of 2 μm, is employed for simultaneously and finely detecting the cloud droplet spectrum, cloud particle diameter, and number concentration. In the experiment, the liquid droplet with a median diameter of 3.9 μm, produced by the ultrasonic atomizer, is used as an example of the cloud particle. The measurement results are consistent with realistic scenario. By using a high speed charge coupled device or complementary metal oxide semiconductor camera, this method can solve the technical bottleneck of three-dimensional fine characteristics of cloud particle in airborne measurement by using cloud droplet spectrometer. It can provide effective support for the research of liquid water in the cloud, entrainment, condensation, collision, and temporal and spatial evolution laws. In addition, it has reference significance for the study of particle dynamics. Simultaneously, this method provides a feasible solution for the measurement of cloud in land-based and airborne platforms.

Detection of degenerate Stokes index states

Stokes phase is the phase difference between orthogonal component states in the decomposition of any polarization state. Phase singularities in the Stokes phase distribution are Stokes singularities of an inhomogeneous polarization distribution. Under circular decomposition, Stokes phase distribution (phi _{12}) represents polarization azimuth (gamma ) distribution and the singularities present in it are polarization singularities. Therefore, the charge of the Stokes vortices depicted as Stokes index sigma _{12} is an important parameter associated with the polarization singularity. The Hybrid order Poincaré sphere (HyOPS)/Higher order Poincaré sphere (HOPS) beams, all having same Stokes index, contain a Stokes singularity at the center of the beam as these beams are constructed by vortex superposition. These beams, being superposition of orthogonal orbital angular momentum (OAM) states in orthogonal spin angular momentum (SAM) states can offer great multiplexing capabilities in communication. In this article, we identify these degenerate Stokes index states and discuss the ways and means of lifting this degeneracy. Otherwise, there are limitations on intensity based detection techniques, where demultiplexing or segregation of different HOPS/HyOPS beams is warranted. The method adduced here uses the diffraction of these beams through an equilateral triangular aperture in combination with polarization transformation as a probe to lift the Stokes index/Stokes phase degeneracy. Successively, the novelty of the detection scheme is discussed in the context of beams with alike polarization distributions where even the technique of Stokes polarimetry fails to predict the OAM and SAM content of the beam.

Spin-independent metalens for helicity-multiplexing of converged vortices and cylindrical vector beams.

The converged vortex beam with a well-defined focal plane is an essential ingredient for trapping and rotating microparticles. Metasurfaces, two-dimensional metamaterials, provide an ultra-compact and flexible platform for designing a converged vortex by integrating the functions of a lens and vortex plate. A spin-defocused metasurface can further boost information capacity such as the multiplexing of helicity-dependent functionalities. Here we propose an approach to realize spin-defocused metalenses that can simultaneously focus terahertz (THz) waves with orthogonal spin states into helicity-dependent vortices based on pure geometric phases. Under the illumination of linearly polarized terahertz waves, all of the helicity-dependent vortices are observed, leading to helicity-multiplexing of converged vortices. Furthermore, the longitudinal multiplexing of converged cylindrical vector beams is demonstrated by superposition of helicity-dependent vortices. This unique approach for multiplexing converged vortices and cylindrical vector beams may open a window for designing future ultra-compact and multifunctional devices with potential applications in communications, optical trapping, and focusing.

Spatial-diversity detection of optical vortices for OAM signal modulation.

We propose a method for identifying orbital angular momentum (OAM) states within a vortex superposition using a Shack-Hartmann (SH) sensor as a spatial-diversity detector. We define a local OAM at every pixel of the SH image, from which we construct an OAM spectrum. The topological charges are determined from the OAM spectrum using a low-complexity algorithm, resulting in estimates that are robust to beam wandering. Data from a 200 m experimental transmission are successfully tested using the proposed technique.

Evolvement rule and hydrodynamic effect of fluid field around fish-like model from starting to cruising

Underwater vehicles are widely used in underwater detection, and bionic design, e.g. imitating fish, is an important way to improve their hydrodynamic performance. Most research is on the mechanical structure and kinematics of fish-like models, while evolvement rules and hydrodynamic effects of fluid field around fish have not been studied adequately. In this paper, a kinematic model to simulate the swimming motion of fish is established according to the actual movement of tuna, and the model is optimized to achieve convenient adjustment in the initial oscillating position and maximum oscillating amplitude. A numerical simulation model is established and the boundary condition is verified by experiments with a physical fish-like prototype and a set of force measuring devices. The evolvement rule of the fluid field around the fish-like model from starting to cruising is determined and the hydrodynamic effect is analyzed. The issue of the effect of fluid fields with various averaged fish-like model densities in the buoyancy regulating process is discussed. Finally, a novel way to calculate the Strouhal number is proposed. The results show that the averaged drag force coefficient decreases as the fish-like model speeds up, because the water pressure near the fish head strengthens to generate a larger resistance force and the vortex in the wake field disperses to produce a less positive effect. The viewpoint that the superposition of vortices will benefit the fish-like model instead of weakening the positive effect is confirmed. The width value of the reversed Kármán vortex street can be connected with the Strouhal number, and the Strouhal number can be calculated by the evolvement rule of the fluid field. This research will contribute to bionic autonomous underwater vehicle design.