An acoustic communication device based on a metasurface vortex stack

Abstract

The application provides an acoustic communication device based on a super-surface vortex stack, the communication device comprising a multi-topological charge structure of a multi-OAM super-surface stack, and the multi-topological charge structure is a multi-layer annular structure with the same center.The application has the advantages that the application can realize a multi-vortex (OAM) superposition design scheme.The application provides a simple multi-layer topological charge superposition scheme to obtain a plurality of vortex field superpositions, and due to the multi-layer design scheme, the topological charge geometric structures do not interfere with each other, which is beneficial to flexible regulation and control such as rotation, twisting and the like.The OAM superposition scheme provided by the application has a sub-wavelength size, and has important significance for the requirements of integration and miniaturization in the actual application process of the device.The structure of the application obtains a plurality of singular points with zero acoustic pressure through simple superposition, and the spatial position of the singular points can be flexibly regulated and controlled through structure topological charge rotation, which has important significance for particle manipulation and movement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of acoustic communication devices, and particularly relates to an acoustic communication device based on super- surface vortex stacking. BACKGROUND

[0002] Acoustic vortices are of great significance to improve information capacity. However, only a few works have been devoted to reveal the interaction characteristics of high degrees of freedom acoustics, such as acoustic beams with composite orbital angular momentums (OAMs). Due to the angular phase dependence, the phase profile of acoustic vortices is with orbital angular momentum (OAM) with discrete values of integer q. Based on the unique non-trivial behavior of vortices, such as the phase singularity at the center of the mode and the zero pressure (black point), they have been applied to many research frontiers such as medicine, particle manipulation, acoustic tweezers and communication. However, vortex beams usually have only one single point, which limits the data capacity and application flexibility. Although some studies can generate vortex arrays, their design is complex and bulky. Due to the orthogonality between different acoustic OAMs, it provides high flexibility and stability for the transmission of OAMs, which has attracted widespread attention. However, the works reported in the past almost all focus on the recovery of multiple oam (i.e. demultiplexing technology), which greatly ignores the exploration of the interaction characteristics of high degrees of freedom beams, making the regulation mechanism of acoustic vortex stacking propagation still difficult to understand. Recently, in the field of optics, the newly emerging vortex stacking effect has been widely studied, resulting in many fascinating results, such as the petal beam using a pinhole binary array, multiple optical traps using a spatial light modulator, and a Ferris wheel using a single metasurface. These new phenomena based on composite vortices are of great significance to the design of a new generation of optical devices. There are some similarities between optics and acoustics, but sound is a mechanical wave without polarization, and the physical scales between acoustics and optics are very different. Therefore, acoustics plays an irreplaceable role in medical and underwater communication. Surprisingly, there are few studies on the physical mechanism of vortex stacking in acoustics, not to mention the vortex stacking evolution process and information transmission based on composite OAMs. There has been an acoustic stacking multiplexing OAM using an active transducer array, which provides an independent channel and can effectively improve the data transmission rate. However, the active scheme is complex, bulky and expensive, which is not conducive to miniaturization and popularization. Recently, there has been a passive scheme for obtaining an acoustic focusing multi-oam beam using an artificial plate, which is conducive to improving the data capacity of acoustic information encoding and decoding. However, the model is fixed and requires two opposite topological charges, which is a focusing acoustic vortex for this scheme, limiting the flexibility and working scenarios. How to propose a flexible and simple scheme to explore the physical mechanism of acoustic vortex stacking and improve the data capacity is an urgent problem to be solved in the field of acoustics.

[0003] The existing acoustic solutions have two types of active and passive solutions, however, the former has problems of complexity, large size and high price, which is not conducive to miniaturization and popularization, and the latter model is fixed, which needs two opposite topological charges, and the solution is a focused acoustic vortex, which limits flexibility and working scenarios. SUMMARY

[0004] The purpose of the present application is achieved by the following technical solutions.

[0005] The present application provides an acoustic communication device based on a super surface vortex stack, which comprises a multi-topological charge structure of a multi-OAM super structured surface, and the multi-topological charge structure is a multi-layer ring structure with the same center.

[0006] Further, when the acoustic wave is incident on the multi-layer ring structure, a composite OAM wave field is obtained at the exit end of the structure:

[0007] l out =(l in +q1)&(l in +q2),l in is the incident wave field, l out is the exit wave field, q1 is the inner layer topological charge number, and q2 is the outer layer topological charge number.

[0008] Further, the cross section of the exit wave field is:

[0009]

[0010] wherein, p represents the angle of the corresponding phase point, φ represents the phase at the corresponding angle position, z represents the vertical distance from the structure, t represents the time parameter; m represents the number of small holes on each ring, A0 represents the amplitude of the wave, D is the distance from any point in space to the center of the structure, i represents the number of rings, k represents the acoustic wave vector in free space, ω represents the angular frequency, and p total represents the total acoustic field.

[0011] Further, each layer of the multi-topological charge structure can be manually rotated or driven by a driving device, and is independently rotated relative to other layers.

[0012] Further, the spatial singularity is freely controlled by twisting the multi-topological charge structure, and the control depth is proportional to the topological charge size of the twisted ring.

[0013] Further, the relationship between the topological charge and the number of singularities conforms to the formula N=|q i+1 -q i |, N is the number of singularities, q i+1 and q i are the topological charge numbers of two adjacent layers.

[0014] Further, the structure surface of the multi-topological charge structure comprises a plurality of holes penetrating through the structure, and the holes are uniformly distributed on each annular structure.

[0015] Further, there is a phase gradient between the holes on each annular structure, and it meets the relationship of 2πq / B, where B is the number of holes on each annular structure, and the number interval of B is [3, 25].

[0016] Further, the two adjacent holes are not in contact, and there is a microstructure inside the hole to support the phase.

[0017] Further, the material of the acoustic communication device is one of the following materials: photosensitive resin, steel, and iron.

[0018] The advantages of the present application are:

[0019] 1. The present application can realize a design scheme of multi-OAM superposition. In the past, to realize multi-OAM superposition usually requires a large structure volume and a complex design, thus resulting in insufficient flexibility of the structure. The present application proposes a simple multi-layer topological charge superposition scheme to obtain multi-vortex field superposition. Due to the multi-layer design scheme of the structure, the topological charges do not interfere with each other in geometry, which is beneficial for flexible control such as rotation and twisting.

[0020] 2. At present, there is almost no research on the wave field characteristics of OAM superposition of acoustic waves. However, acoustic waves are of great significance for underwater communication and medical treatment. The OAM superposition scheme proposed in the present application has a subwavelength size, which is of great significance for the integration and miniaturization required in the actual application process of the device.

[0021] 3. The structure of the present application obtains a plurality of singular points with zero acoustic pressure through simple superposition, and the spatial position of the singular points can be flexibly controlled through the rotation of the topological charge of the structure, which is of great significance for the manipulation and movement of microparticles. BRIEF DESCRIPTION OF DRAWINGS

[0022] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the present application. Moreover, the same reference numerals are used throughout the various drawings to designate identical parts. In the drawings:

[0023] Figure 1 A schematic diagram of an acoustic communication device based on super surface vortex superposition according to an embodiment of the present application is shown.

[0024] Figure 2 A simplified diagram of the phase distribution of a super surface with multiple intrinsic topological charges according to an embodiment of the present application is shown.

[0025] Figure 3 A schematic diagram showing the initial phase twist effect of the structure-inherent topological charge is shown.

[0026] Figure 4 A schematic diagram showing real-time communication based on acoustic vortex superposition according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0027] Exemplary embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be embodied in various forms without being limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood, and so that the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0028] Main points of the present application include: 1. Annular multi-topological charge structure design. 2. Rotatable twist, different layers of topological charges do not interfere, and the structure has high flexibility. 3. Subwavelength structure, small volume, thin thickness. 4. First proposed this multi-layer topological charge superposition scheme. 5. The position of the spatial singularity can be controlled by rotating the topological charge. 6. First use the singularity of the superimposed acoustic field to realize acoustic communication. 7. The design scheme can be used for underwater acoustic communication or extended to optical or elastic wave systems. 8. Multiple particle manipulation can be achieved using singularities.

[0029] Figure 1 A schematic diagram showing the principle of an acoustic communication device based on super surface vortex superposition according to an embodiment of the present application is shown. Figure 1 The meanings of the symbols are as follows: 1: incident acoustic wave; 2: multi-OAM superstructured surface; 3: annular rotatable design; 4: composite OAM wave; 5: composite wave phase section; 6: multi-OAM phase superposition process (taking topological charges 1 and 4 as examples).

[0030] As shown in Figure 1 , an acoustic communication device based on super surface vortex superposition provided by the present application includes a co-planar design multi-topological charge structure integrated into a single plane (2), the structure has a multi-layer annular structure (3), which is flexible and twistable, and when the acoustic wave (1) is incident on the structure, a composite OAM wave field will be obtained at the exit end of the structure (4). out = (l in + q1) & (l in + q2), l in is the incident wave field, lout is the exit wave field, q1 is the number of inner topological charges, and q2 is the number of outer topological charges. Wherein (5) is a section during the wave field propagation process, which can be expressed by the formula The described, p represents the angle of the corresponding phase point, φ represents the phase at the corresponding angle position, z represents the vertical distance from the structure, t represents the time parameter; m represents the number of small holes on each ring, A0 represents the amplitude of the wave, D is the distance from any point in space to the center of the structure, i represents the number of rings, k represents the acoustic wave vector in free space, ω represents the angular frequency, Ptotal represents the total sound field, and is only used for convenient understanding. P(x, y) is the position of the measured singular point, which is placed at different positions in space according to the size of the structure. (6) is a simple schematic diagram for describing the working principle of the vortex superposition superstructure.

[0031] Figure 1 In this application, an acoustic communication device based on super surface vortex superposition is provided, which has a ring-shaped twistable topological charge structure (3). The topological charge structure (3) includes a plurality of concentric rings, each of which can be rotated independently and is not affected by other rings. The topological charge structure (3) can be manually artificial or electronically driven, such as installing a rotor or motor device inside the structure for rotation.

[0032] The twist (3) realizes the free control of the spatial singular point, and the control depth is proportional to the twist ring topological charge size. This application first uses the singular point after OAM superposition to realize transmission. In addition, for the design of ring-shaped topological charge, elliptical topological charge design, square topological charge design also belongs to the realizable way of topological charge structure (3). This application is not limited to the acoustic system, and is also applicable to the wave system such as light wave and elastic wave. The structure is not limited to a single layer structure, and is also applicable to a multi-layer structure composed of this type of structure.

[0033] For acoustic communication, when the sound wave is incident on the structure, the topological charge of the inner and outer rings can be twisted to realize different rotation rates of singular points. When the inner or outer ring structure is rotated, the singular points in the wave field passing through the structure will have different rotation rates, which are proportional to the size of the rotated structure topological charge. Based on this, two states "0" and "1" are defined to realize the function of sound wave information transmission. For microparticle manipulation, when the sound wave is incident on the structure, multiple singular points will be formed at the exit end, and there is a gradient acoustic force field corresponding to the singular point, so small particles can be localized or captured. It is used in the fields of underwater communication, medical treatment, etc.

[0034] Working principle: multiple OAM wave fields interfere with each other to form multiple singular points. The singular points are related to the topological charge of the structure, and the relationship between the topological charge and the number of singular points conforms to the formula N = |q i+1 -q i |, N is the number of singular points, q i+1 , q i is the topological charge number of two adjacent layers. The rotation speed of the spatial singular point corresponding to the twist of different topological charges is proportional to the size of the twisted topological charge.

[0035] Figure 2 Simplified plots of phase distribution of super-surfaces with multiple intrinsic topological charges according to embodiments of the present application are shown. (a) q1 = 1 and q2 = 4, simplified plots of phase distribution of super-surfaces with multiple intrinsic topological charges. The phase (A1) and amplitude (A2) distribution of vortex superimposed acoustic waves are simulated with effective medium. The phase (A3) and amplitude (A4) distribution of vortex superimposed acoustics based on super-surface. (b) and (B1)-(B4) are the same as (a) and (A1)-(A4), but when q1 = -1 and q2 = 4. The white circle is the location of phase singularity (and black dot). These plots are calculated at z = 2λ0. z represents the vertical distance from the structure at any point at the transmission end; λ0represents the working wavelength; z = 2λ0represents that the data taken is located at 2 wavelengths away from the structure.

[0036] Figure 3 Schematic diagrams of initial phase twist effect of structure intrinsic topological charge according to embodiments of the present application are shown. (a) State 1-“0”, fixed external intrinsic topological charge, twisted internal topological charge, (b) simulated and measured amplitude evolution at P point. (c) State 2-“1”, fixed internal intrinsic topological charge, twisted external topological charge, (d) simulated and measured amplitude evolution at P point.

[0037] Figure 3 In the structure 3, the structure surface of the structure includes a plurality of holes, the holes along the structure surface are distributed in a ring shape, each ring can support different topological charge numbers, such as q = 1 or 2, 3, etc., the number of rings can be increased according to the number of OAM superposition required, and the present application shows an example of two topological charge superpositions, and q1 = 1 and q2 = 4. If more superpositions are required, the number of ring structures can be increased during design. The small holes penetrating through the structure are the key to realizing the topological charge of the structure, and the small holes distributed along the ring structure have a phase gradient and satisfy the relationship of 2πq / N, where N is the number of small holes per ring, In the structure 3, the structure surface of the structure includes a plurality of holes, the holes along the structure surface are distributed in a ring shape, each ring can support different topological charge numbers, such as q = 1 or 2, 3, etc., the number of rings can be increased according to the number of OAM superposition required, and the present application shows an example of two topological charge superpositions, and q1 = 1 and q2 = 4. If more superpositions are required, the number of ring structures can be increased during design. The small holes penetrating through the structure are the key to realizing the topological charge of the structure, and the small holes distributed along the ring structure have a phase gradient and satisfy the relationship of 2πq / N, where N is the number of small holes per ring, Figure 3 In the structure 3, the structure surface of the structure includes a plurality of holes, the holes along the structure surface are distributed in a ring shape, each ring can support different topological charge numbers, such as q = 1 or 2, 3, etc., the number of rings can be increased according to the number of OAM superposition required, and the present application shows an example of two topological charge superpositions, and q1 = 1 and q2 = 4. If more superpositions are required, the number of ring structures can be increased during design. The small holes penetrating through the structure are the key to realizing the topological charge of the structure, and the small holes distributed along the ring structure have a phase gradient and satisfy the relationship of 2πq / N, where N is the number of small holes per ring,

[0038] Figure 4A schematic diagram of real-time communication based on acoustic vortex superposition according to the embodiment of the present application is shown. The received time-domain signal twists (a) the internal intrinsic topological charge and (b) the external intrinsic topological charge in each cycle. (c) Target data of different data streams and received output. (d) The measured results carried by the vortex superposition beam channel reconstruct the image.

[0039] The advantages of the present application are as follows: simple and flexible design, small volume, thin thickness, low cost, and easy integration. The present application theoretically proposes and experimentally proves a clever scheme to generate vortex superposition using a multi-intrinsic topological charge design of coplanar engineering. The scheme model is flexible and simple, and the number of vortex superpositions can be modified by adding engineered intrinsic topological charges to the metasurface, and the number of phase singular points complies with the conservation law, where qi is the intrinsic topological charge of structure i layer. Due to the flexible design, the present application can twist the initial phase of the intrinsic topological charge in the model, and the phase singular point will also rotate to different degrees, which is related to the intrinsic topological charge. On this basis, by twisting the intrinsic topological charge of different layers, acoustic image transmission based on vortex superposition is realized, which provides the possibility for further improving the communication efficiency.

[0040] The above describes only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An acoustic communication device based on metasurface vortex stacks, characterized in that, The communication device includes a multi-topological charge structure with a superimposed metasurface of multiple orbital angular momentum (OAM), wherein the multi-topological charge structure is a multi-layered ring structure with the same center; the surface of the multi-topological charge structure includes a plurality of holes penetrating the multi-topological charge structure, and the holes are uniformly distributed on each ring structure. When sound waves are incident on the multi-layered annular structure, a composite OAM wave field is obtained at the exit end of the structure: l out = (l in + q1) & (l in + q2), l in For the incident wave field, l out For the outgoing wave field, q1 is the inner topological charge number and q2 is the outer topological charge number; The cross-sectional expression of the emitted wave field is: ； in, This represents the angle of the corresponding phase point. This indicates the phase at the corresponding angular position. Indicates the vertical distance from the structure. The time parameter is represented by m, the number of holes on each ring is represented by A0, the wave amplitude is represented by D, the distance from any point in space to the center of the structure is represented by i, the number of rings is represented by k, and the wave vector of the sound wave in free space is represented by k. Represents angular frequency. This indicates the total sound field.

2. The acoustic communication device based on metasurface vortex stacking according to claim 1, characterized in that, Each layer of the multi-topology load structure can be rotated independently relative to other layers, either manually or by a drive device.

3. The acoustic communication device based on metasurface vortex stacking according to claim 2, characterized in that, The spatial singularity is freely controlled by twisting the multi-topological load structure, and the depth of control is proportional to the size of the topological load of the twisting ring.

4. The acoustic communication device based on metasurface vortex stacking according to claim 3, characterized in that, The relationship between the topological load and the number of singularities conforms to the formula... N is the number of singularities, q i+1、 q i The topological load number of two adjacent layers.

5. An acoustic communication device based on metasurface vortex stacking according to claim 1, characterized in that, There is a phase gradient between the holes on each ring structure, and the relationship is 2πq / B, where B is the number of holes on each ring structure, and the number of B is in the range of [3, 25].

6. An acoustic communication device based on metasurface vortex stacking according to claim 1, characterized in that, There is no contact between adjacent holes, and each hole contains microstructures that support the phase.

7. An acoustic communication device based on metasurface vortex stacking according to claim 1, characterized in that, The acoustic communication device is made of one of the following materials: photosensitive resin, steel, or iron.

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