Array Beam Research Articles

Experimental synthesis of higher-order Poincaré sphere beam array with spatial coherence engineering

We propose a compact method to experimentally synthesize a class of vector beam arrays with periodic higher-order Poincaré sphere (HOPS) polarization states by engineering the spatial coherence structure of a partially coherent light source. We demonstrate that the spatial coherence structure and polarization state of the partially coherent source can be simultaneously controlled using a phase-only spatial light modulator and a common-path interferometric arrangement with the aid of a complex-random-mode representation method. We show experimentally that the polarization state of a single HOPS beam in the source plane can be mapped into a beam array generated in the far field, and the degree of polarization of the beam array can be conveniently controlled with spatial coherence engineering. Our method provides an alternative way to synthesize beam arrays with structured coherence and polarization properties.

Laser Doppler multi-beam differential vibration sensor for real-time continuous visualization of buried objects in multiple frequency bands.

Laser-acoustic detection of buried objects, such as landmines, uses elastic waves in the ground and a laser vibrometer to create a vibration image of the ground surface. A decision on the presence of a buried object is made by analyzing vibration images for multiple vibration frequencies. With traditionally used laser Doppler vibrometers, the vibration imaging data are saved to a computer memory to be analyzed, which increases the detection time. A novel laser multi-beam differential interferometric sensor (LAMBDIS) that provides simultaneous real-time visualization of vibration images for multiple frequencies has been developed. The sensor is capable of displaying vibration images for up to 32 frequency bands simultaneously in real time. The sensor employs a digital line-scan complementary metal-oxide semiconductor camera and field programmable gate arraysbased real-time signal processing and is capable of operating continuously by scanning an object with a linear array of laser beams. Performance of the sensor has been verified experimentally. The ability of the LAMBDIS for real-time continuous vibration imaging of the ground surface in multiple frequency bands for laser-acoustic detection of buried objects has been demonstrated.

Analytical solutions for Bloch waves in resonant phononic crystals: deep-subwavelength energy splitting and mode steering between topologically protected interfacial and edge states

Summary We derive analytical solutions based on singular Green’s functions, which enable efficient computations of scattering simulations or Floquet–Bloch dispersion relations for waves propagating through an elastic plate, whose surface is patterned by periodic arrays of elastic beams. Our methodology is versatile and allows us to solve a range of problems regarding arrangements of multiple beams per primitive cell, over Bragg to deep-subwavelength scales; we cross-verify against finite element numerical simulations to gain further confidence in our approach, which relies upon the hypothesis of Euler–Bernoulli beam theory considerably simplifying continuity conditions such that each beam can be replaced by point forces and moments applied to the neutral plane of the plate. The representations of Green’s functions by Fourier series or Fourier transforms readily follows, yielding rapid and accurate analytical schemes. The accuracy and flexibility of our solutions are demonstrated by engineering topologically non-trivial states, from primitive cells with broken spatial symmetries, following the phononic analogue of the Quantum Valley Hall Effect. Topologically protected states are produced and coexist along: interfaces between adjoining chiral-mirrored bulk media, and edges between one such chiral bulk and the surrounding bare elastic plate, allowing topological circuits to be designed with robust waveguiding. Our topologically protected interfacial states correspond to zero-line modes, and our topological edgestates are produced in accordance with the bulk-edge correspondence. These topologically non-trivial states exist within near flexural resonances of the constituent beams of the phononic crystal and hence can be tuned into a deep-subwavelength regime.

Interfacial flows past arrays of elastic fibers

Confined capillary flows can have dramatic effects on systems containing structures soft enough to be deformed by surface tension. In this work, we study the drainage of a defending oil phase by an immiscible water phase through channels textured with arrays of elastic beams, which constitute a compliant porous medium. The coupling of flow dynamics with elastocapillarity causes the entrapment of the defending phase within periodic self-assembled bundles.

Математическое моделирование воздействия слабых низкочастотных сейсмических волн на ледниковый массив

Introduction. The Kolka glacial massif repeatedly broke off from the freezing surface and thereby formed powerful glacial mudflows that caused great material damage to the Republic of the Republic of Alania with numerous human casualties. In the work of Muzaev I. D. and Sozanov V. G., the first step was taken in mathematical modeling of seismic vibrations of the glacial massif and the statement was proved that weak earthquakes of 3-3.5 MSK points can provoke bending and shear stresses several times higher than the destructive stresses of ice on the underlying surface of the glacial massif. The considered mathematical model proposed in the article has been amended, significantly clarifying the scientific results. The purpose of the work is to formulate and solve an initial boundary value problem that resembles the problems of mathematical physics and simulates the fluctuations of a glacial massif. The oscillation of the array is caused by the freezing of a weak traveling harmonic seismic wave with an intensity of 3-3.5 MSK points falling on it and on its underlying surface. Materials and methods. Due to the fact that the longitudinal dimensions of glacial massifs are an order of magnitude larger than their transverse dimensions, the article assumes that the mechanics of such massifs are most adequately modeled if their geometric configurations are considered as girder bodies with their physical and mechanical characteristics. The losses of mechanical energy due to internal resistance in the array material are taken into account in accordance with the hypothesis of S. A. Sorokin. The elastic rebound force from a seismically oscillating base is taken into account in accordance with Winkler’s hypothesis. Due to the fact that the coefficient of the differential equation of vibrations of the beam array is complex, the equation splits into a system of two fourth-order differential equations with real coefficients, where the desired functions are the real and imaginary parts of the originally sought complex function. The initial boundary value problem is solved analytically. Results. On the example of the Kolka glacier (North Caucasus Highlands), which collapsed in 2002 and claimed 126 human lives, computer experiments were performed to calculate induced stresses. Discussion. Comparative computational experiments have proved the claims that the seismic stresses caused by the Winkler elastic rebuff of the seismically oscillating surface of the base: a) are significantly greater than the stresses from the bending component of the vibrations of the array; b) can significantly exceed all the values of the destructive stresses of the ice. Conclusion. It is proved that the superiority of the Winkler stress over the destructive stress of ice can also occur in weak earthquakes with an intensity of 3-3.5 MSK points. Such superiority can play the role of a trigger for the breakaway of the glacial massif from the freezing surface and thereby the formation of a powerful glacial mudflow, as happened on the Kolka glacier. Suggestions for practical application and directions for future research. The paper presents a method for directly determining the cause of the breakaway of the glacial massif from the freezing surface. In the future, it is desirable to check the effect of a sharp induced maximum stress for steels intended for mechanical engineering purposes. It is desirable to study in detail the time dependence of the effect of inducing maximum stresses in arrays using low-intensity waves.

Controllable self-rotating array beam with an arc-shaped accelerating trajectory.

In this study, a modified interfering vortex phase mask (MIVPM) is proposed to generate a new type of self-rotating beam. The MIVPM is based on a conventional and stretched vortex phase for generating a self-rotating beam that rotates continuously with increasing propagation distances. A combined phase mask can produce multi-rotating array beams with controllable sub-region number. The combination method of this phase was analyzed in detail. This study proves that this self-rotating array beam has an effectively enhanced central lobe and reduced side lobe owing to adding a vortex phase mask compared with a conventional self-rotating beam. Furthermore, the propagation dynamics of this beam can be modulated by varying the topological charge and constant a. With an increase in the topological charge, the area crossed by the peak beam intensity along the propagation axis increases. Meanwhile, the novel self-rotating beam is used for optical manipulation under phase gradient force. The proposed self-rotating array beam has potential applications in optical manipulation and spatial localization.

Self-focusing effect of focused array beams propagating from the space orbit through the atmosphere to the ground

For the incoherent beam combination, the self-focusing effect of focused array beams propagating from the space orbit through the atmosphere to the ground is studied. It is shown that the self-focusing effect in the atmosphere becomes stronger as the fill factor increases. When the circumcircle diameter and the fill factor of array beams are fixed, the self-focusing effect in the atmosphere becomes stronger as the element number N decreases. However, for the maximal beam compression case, the self-focusing effect in the atmosphere can assist delivering much more powerful array beams from the space orbit to the ground as N increases, and an array beam has the advantage to deliver powerful laser beam compared with a single laser beam. In particular, an effective design rule for maximal compression without filamentation of transported array beams from orbit to the ground is derived.

Flow Cytometry with Anti-Diffraction Light Sheet (ADLS) by Spatial Light Modulation.

Flow cytometry is a widespread and powerful technique whose resolution is determined by its capacity to accurately distinguish fluorescently positive populations from negative ones. However, most informative results are discarded while performing the measurements of conventional flow cytometry, e.g., the cell size, shape, morphology, and distribution or location of labeled exosomes within the unpurified biological samples. Herein, we propose a novel approach using an anti-diffraction light sheet with anisotroic feature to excite fluorescent tags. Constituted by an anti-diffraction Bessel-Gaussian beam array, the light sheet is 12 μm wide, 12 μm high, and has a thickness of ~0.8 μm. The intensity profile of the excited fluorescent signal can, therefore, reflect the size and allow samples in the range from O (100 nm) to 10 μm (e.g., blood cells) to be transported via hydrodynamic focusing in a microfluidic chip. The sampling rate is 500 kHz, which provides a capability of high throughput without sacrificing the spatial resolution. Consequently, the proposed anti-diffraction light sheet flow cytometry (ADLSFC) can obtain more informative results than the conventional methodologies, and is able to provide multiple characteristics (e.g., the size and distribution of fluorescent signal) helping to distinguish the target samples from the complex backgrounds.

Theoretical analysis of combining efficiency and beam quality degradation in a misaligned diffractive coherent combining system.

We theoretically investigate the combining efficiency and combined beam quality degradation induced by beam array misalignment in a coherent combining system based on diffractive optical elements. Theoretical model is established based on the Fresnel diffraction. We consider pointing aberration, positioning error and beam size deviation in array emitters as typical misalignments, and discuss their influences on beam combining by this model. The statistical analysis results and the accurate fitting curves of the degradation have been given based on the repetitive simulations with normal distributed random misalignments. According to the results, the combining efficiency is affected greatly by the pointing aberration and position error of the laser array, while the combined beam quality is just affected by the pointing aberration generally. Based on calculation with a series of typical parameters, the standard deviations of the laser array's pointing aberration and position error are required to less than 15μrad and 1μm respectively to maintain an excellent combining efficiency. If we only concentrate on the beam quality, the pointing aberration need to be less than 70μrad.

An Analytical Method of Beamwidth under Different Angles of Planar Array

It is widely recognized that the calculation of the beam width of the large-aperture planar array through beam pattern simulation is slow and inefficient, and obtaining the ability to distinguish the target from different angles within the observation range quickly is difficult. This paper uses methods such as the array product theorem, discrete array, continuous array beam width equivalence, and coordinate transformation to acquire a more accurate analytical solution of the beam width of the planar array. The analytical value of the beam width of the planar array at different angles and the number of array elements were compared with the simulated value. The results show that with the usage of the new method, the average deviation of the beam width analytical values in different main maxima directions can reach less than 1% when the number of array elements is less than 10 elements. Compared with the simulation method, the planar array beam width can be obtained quickly and accurately by the new method.

Orientation of the NV centers are determined using the cylindrical vector beam array.

The determination of nitrogen-vacancy centers plays an important role in quantum information sensing. Efficiently and rapidly determining the orientation of multiple nitrogen-vacancy center s in a low-concentration diamond is challenging due to its size. Here, we solve this scientific problem by using an azimuthally polarized beam array as the incident beam. In this paper, the optical pen is used to modulate the position of beam array to excite distinctive fluorescence characterizing multiple and different orientations of nitrogen-vacancy centers. The important result is that in a low concentration diamond layer, the orientation of multiple NV centers can be judged except when they are too close within the diffraction limit. Hence, this efficient and rapid method has a good application prospect in quantum information sensing.

Design and realization of an autofocusing Airyprime beams array

An Airyprime beams array that consists of four centrosymmetric Airyprime beamlets is designed for the first time, and the analytical expression of the Airyprime beams array propagating in free space is derived. The Airyprime beams array is shown to possess the autofocusing property. The effects of the transverse displacement parameter, the exponential decay factor and the scaling factor on the autofocusing ability and the focus position of the Airyprime beams array are investigated in detail. The autofocusing ability of the Airyprime beams array is improved by increasing the transverse displacement parameter or reducing the exponential decay factor. Further, the autofocusing ability of the Airyprime beams array in the case of nonzero off-centre position can be enhanced by decreasing the scaling factor. The focus position of the Airyprime beams array can be controlled by adjusting the transverse displacement parameter or the scaling factor. The autofocusing evolutionary process of the Airyprime beams array is quite different from that of the Airy beams array. The trajectory of the peak intensity for the Airyprime beams array is more regular than that for the Airy beams array. The Airyprime beams array has stronger autofocusing ability and smaller focusing dominant spot than the Airy beams array with the same beam parameters. Moreover, we experimentally generate the Airyprime beams array, and the autofocusing properties of the Airyprime beams array are demonstrated. The Airyprime beams array will find important potential applications in free space optical communication and so on.

Tailoring Large Asymmetric Laguerre–Gaussian Beam Array Using Computer-Generated Holography

Laguerre–Gaussian beams are structured light beams with a donut-shaped symmetric intensity profile and a helical phase profile. The beam profile is defined by a quantized parameter known as the mode number which extends to infinity. The availability of unbounded modes makes these beams a promising candidate for next-generation optical computing, and optical communication technologies. The symmetric intensity profile of a Laguerre–Gaussian beam can be made asymmetric through certain techniques and these beams are known by the term ‘asymmetric Laguerre–Gaussian beams’. Here, the asymmetricity adds another degree of freedom to the beam (apart from its mode number) which helps in encoding more information compared to a symmetric beam. However, in order to harness the benefits of all the available degrees of freedom, it is required to generate a large number of such beams in a multiplexed fashion. Here, we report the generation of such a large array of asymmetric Laguerre–Gaussian beams for the first time. Computer-generated holography and spatial multiplexing techniques were employed to generate a large array comprising of 12 × 16 = 192 asymmetric Laguerre–Gaussian beams with an arbitrary mode index and asymmetricity.

3D single shot lensless incoherent optical imaging using coded phase aperture system with point response of scattered airy beams

Interferenceless coded aperture correlation holography (I-COACH) techniques have revolutionized the field of incoherent imaging, offering multidimensional imaging capabilities with a high temporal resolution in a simple optical configuration and at a low cost. The I-COACH method uses phase modulators (PMs) between the object and the image sensor, which encode the 3D location information of a point into a unique spatial intensity distribution. The system usually requires a one-time calibration procedure in which the point spread functions (PSFs) at different depths and/or wavelengths are recorded. When an object is recorded under identical conditions as the PSF, the multidimensional image of the object is reconstructed by processing the object intensity with the PSFs. In the previous versions of I-COACH, the PM mapped every object point to a scattered intensity distribution or random dot array pattern. The scattered intensity distribution results in a low SNR compared to a direct imaging system due to optical power dilution. Due to the limited focal depth, the dot pattern reduces the imaging resolution beyond the depth of focus if further multiplexing of phase masks is not performed. In this study, I-COACH has been realized using a PM that maps every object point into a sparse random array of Airy beams. Airy beams during propagation exhibit a relatively high focal depth with sharp intensity maxima that shift laterally following a curved path in 3D space. Therefore, sparse, randomly distributed diverse Airy beams exhibit random shifts with respect to one another during propagation, generating unique intensity distributions at different distances while retaining optical power concentrations in small areas on the detector. The phase-only mask displayed on the modulator was designed by random phase multiplexing of Airy beam generators. The simulation and experimental results obtained for the proposed method are significantly better in SNR than in the previous versions of I-COACH.

Laser multibeam differential interferometric sensor for acoustic detection of buried objects

A laser multibeam differential interferometric sensor (LAMBDIS) was developed that provides measurement of vibration fields of objects with high sensitivity, while having low sensitivity to the whole-body motion of the object, or the sensor itself. The principle of operation of the LAMBDIS is based on the interference of light reflected from different points on the object surface illuminated with a linear array of laser beams. The Doppler shift induced by the sensor motion is approximately the same for all beams and is automatically subtracted from the measurements. The performance of the sensor for laser-acoustic detection of a buried object was experimentally investigated. The ability of LAMBDIS to detect buried objects from a moving vehicle has been demonstrated in field experiments.

Simultaneously enhancing autofocusing ability and extending focal length for a ring Airyprime beam array by a linear chirp.

It is of great significance to solve the problem that improving autofocusing ability is always at the cost of shortening focal length. By introducing a linear chirp into a ring Airyprime beam array, an optimization scheme to simultaneously achieve the enhancement of autofocusing ability and the extension of focal length is proposed. The autofocusing ability can be enhanced by up to 72.28%, and the corresponding focal length is extended by 34.81%. The focal length can be extended by 110.28% at most, and the corresponding autofocusing ability is improved by 48.59%. To verify the feasibility of this scheme, we have carried out an experiment for the generation of a ring Airyprime beam array with a linear chirp, and the experimental results for autofocusing ability and focal length are in good agreement with theoretical results. Our findings have potential applications in many aspects, such as free space optical communication.

Editorial: Laser field manipulation and its advanced applications

Laser field manipulation is currently one of hot topics in the field of photonics. A wide variety of novel beams, for instance, vectorial vortex beams [1], orbital angular momentum (OAM) comb [2], toroidal vortices [3], high-dimensional beam arrays [4], can be well generated through tailoring various spatial and temporal degrees of freedom (DoFs) as OAM, spin angular momentum (SAM), phase, time/frequency, amplitude, and wave vector. Such novel beams from laser field manipulation have inspired lots of advanced applications covering classical and quantum physics as large-capacity optical communications, lidar, optical tweezer, laser processing, high-dimensional quantum entanglement, and also gravity wave detection [5]. In recent years, many efforts have been paid on laser field manipulation and achieve a leaping development. Hence, to show recent advances in laser field manipulation and their enabled applications, we organize this research topic, and expect to motivate more state-of-art scenarios.The seven published papers in this topic involve both fundamental and engineering research, regarding complex laser field tailoring and applications. M. Zhang et al. In summary, this research topic collects seven representative work of state-of-art laser field manipulation and its advanced applications. We expect this topic will build a bridge of distinct sub-areas integration, and further promote the development of laser field manipulation.

Design of the Polarization-Independent Wavelength Multiplexing Holographic Metasurface

Metasurface regulates the polarization, phase, amplitude, frequency, and other characteristics of electromagnetic waves through the subwavelength microstructure. By using its polarization characteristics, it can realize the functions of optical rotation and vector beam generation. It is the most widely used method of regulation. However, parallel optical manipulation, imaging, and communication usually require polarization-insensitive focused (or vortex) arrays of beams, so polarization-independent wavelength multiplexing optical systems need to be considered. In this paper, the genetic algorithm combined with the computer-generated hologram (CGH) is used to control the transmission phase of the structure itself, and on the basis of wavelength multiplexing, the corresponding array of focused or vortex beams without the polarization selection property is realized. The simulation software results show that the method has a huge application prospect in optical communication and optical manipulation.

Rotating anisotropic rectangular hollow Gaussianarray.

A new class of partially coherent sources that can produce stable rotating anisotropic rectangular hollow Gaussian array profiles in the far field is presented. The cross-spectral density function and the spectral density of this kind of source on the propagation are derived, and its propagation characteristics, which are quite different from twisted Gaussian Schell-model beams, are discussed. The results show that each hollow lobe in the array tends to rotate around the axis during propagation. In addition, the dimension of the array, the distance between the lobes of the array, and the number of rows and columns of the rectangular array can be flexibly manipulated by adjusting the source parameters. Our work may provide a method to generate rotating anisotropic array beams with hollow lobes, which could have certain reference values in optical manipulation.

Study on Supermode Control of External Cavity VCSEL Array with Parallel-Coupled Model

A vertical-cavity surface-emitting laser (VCSEL) is easily made into a two-dimensional array to improve its output power. However, if the near-field complex amplitude output cannot be stabilized in the lowest supermode generated by the fundamental transverse mode, the spot cannot converge on the center normal of the far-field array geometry, and the energy will be diverged. The external cavity is prepared for the VCSEL array, and the output of the array can be stabilized in the lowest order supermode generated by the fundamental transverse mode by supermode control through diffraction coupling. In this study, the parallel-coupled model for the 2-dimensional VCSEL array based on Fresnel diffraction integration was established and used to numerically calculate and analyze the influence on the supermodes’ thresholds of different array distributions, array elements’ transverse modes and duty ratios versus the length of the external cavity. The simulation results show that the square array provides a wider range of external cavity control length (0.2d2/λ and approximately 0.9 to 1.0d2/λ). The lowest supermode of the fundamental transverse mode can be outputted. For the regular hexagonal array with the length of the external cavity of 0.15d2/λ and 0.6d2/λ. The results have important reference significance for the design of an external cavity VCSEL array, which can control the supermode and obtain VCSEL coherent array beams with high power and near diffraction limits.