Intracavity vortex wave generation device and control method

Abstract

The invention discloses an intra-cavity vortex wave generation device and a control method, and relates to the technical field of acoustic engineering, the intra-cavity vortex wave generation device comprises a resonant cavity system and a nonlinear regulation and control assembly integrated in the resonant cavity system; the resonant cavity system forms a closed loop through a coupling structure by a plurality of resonant units and is used for supporting resonance of a fluctuation mode; the non-linear regulation and control assembly is used for realizing adjustable non-reciprocal coupling between the at least two resonance units; and the resonant cavity system is also used for generating vortex waves carrying orbital angular momentum by adjusting the coupling parameters of the non-reciprocal coupling. The complexity and loss that require additional beamforming elements or multiple active transducer arrays in conventional approaches are avoided. The topological charges of the generated vortex waves are controlled by adjusting the coupling parameters of the non-reciprocal coupling, so that the vortex waves with different topological charges are generated, and wider applicability is provided for various applications.

Description

Technical Field

[0001] The present invention relates to the field of acoustic engineering technology, and in particular to an intracavity vortex wave generating device and a control method. Background Art

[0002] Vortex waves carry orbital angular momentum, and their spiral wavefronts rotate azimuthally about their propagation axis. They have been extensively studied in acoustics, microwaves, and optics. Due to their unique orbital angular momentum properties, vortex beams hold promise for widespread applications in particle manipulation, object rotation, high-speed communications, and quantum information. To date, various methods for generating acoustic vortex beams have been developed, which can be categorized as passive or active based on the generation method. In passive methods, a standard Gaussian beam is converted into a vortex beam by passing it through discrete elements such as spiral phase plates, spiral diffraction gratings, q-plates, or metasurfaces. Alternatively, acoustic vortex beams can be generated using active transducer arrays, typically utilizing phased array technology (i.e., regularly varying phase or time delay) and multiple active transducers to generate specific acoustic vortices. Another method for generating vortex beams in optical systems is intracavity vortex wave generation, also known as vortex wave lasing. This method generates a beam directly from the cavity without the need for additional beam-shaping elements. The intracavity vortex wave generation method can produce high-power, high-beam-quality vortex wave beams with significant efficiency and compact structure.

[0003] Although the existing acoustic vortex beam generation methods have made some progress, many problems still exist. Among the passive methods, although they are universal, they often have problems such as complex structure, high loss, low conversion efficiency, and difficulty in expansion. Active methods require the use of multiple active components, which have problems such as difficult integration, high loss, and high precision requirements. In addition, although the intracavity vortex wave generation method has performed well in the field of optics, it is very challenging because it usually involves delicate engineering such as characteristic states, gain media, and nonlinearities. To date, the intracavity vortex wave generation method in acoustics has not been explored. Summary of the Invention

[0004] The primary objective of the present invention is to provide an intracavity vortex wave generating device and control method. By integrating a nonlinear control component into a resonant cavity system and utilizing the properties of nonreciprocal coupling, vortex waves carrying orbital angular momentum are generated directly within the cavity, avoiding the complexity and energy loss associated with the use of additional beamforming elements or multiple active transducer arrays in traditional methods. By adjusting the coupling parameters of the nonreciprocal coupling, the topological charge of the generated vortex waves can be flexibly controlled, thereby enabling the generation of vortex waves with different topological charges and providing broader applicability for a variety of applications.

[0005] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions: According to a first aspect of an embodiment of the present application, there is provided an intracavity vortex wave generating device, comprising: a resonant cavity system, and a nonlinear control component integrated in the resonant cavity system; The resonant cavity system is composed of a plurality of resonant units forming a closed loop through a coupling structure, which is used to support the resonance of the wave mode; The nonlinear control component is used to achieve adjustable non-reciprocal coupling between at least two of the resonant units; and is also used to enable the resonant cavity system to generate vortex waves carrying orbital angular momentum by adjusting the coupling parameters of the non-reciprocal coupling.

[0006] Optionally, the resonant cavity system is an acoustic resonant cavity system, the resonant unit is an acoustic resonant cavity, and the coupling structure includes an acoustic pipe connecting adjacent acoustic resonant cavities.

[0007] Optionally, the properties of the coupling structure include a reciprocal coupling channel and a non-reciprocal coupling channel, wherein the reciprocal coupling channel connects all adjacent resonant units for bidirectional coupling between adjacent resonant units; and the non-reciprocal coupling channel selectively connects at least one pair of resonant units for introducing unidirectional coupling to break the time reversal symmetry.

[0008] Optionally, the nonlinear control component includes an active electroacoustic element, which includes an amplifier and a transducer; the amplifier is used to adjust the gain and phase of the electrical signal; the transducer includes a speaker and a microphone, which are used to inject sound waves into the resonant cavity and collect feedback signals, respectively; the amplifier controls the amplitude of the non-reciprocal coupling by gain adjustment, and controls the phase of the non-reciprocal coupling by adjusting the phase, thereby controlling the topological charge of the vortex wave.

[0009] Optionally, the phase of the non-reciprocal coupling and the topological charge of the vortex wave satisfy a preset mapping relationship, and the preset mapping relationship includes: when the phase of the non-reciprocal coupling is -0.38π, the number of spiral rotations of the topological charge rotates 1 circle counterclockwise in the phase field; when the phase of the non-reciprocal coupling is 0.38π, the number of spiral rotations of the topological charge rotates 4 circles counterclockwise in the phase field. Optionally, when the phase of the non-reciprocal coupling is fixed, the gain of the amplifier is adjusted so that the resonant cavity system exhibits a bistable characteristic; and a set difference exists between a generation threshold gain and an extinction threshold gain of the vortex wave.

[0010] Optionally, the resonant cavity system is a microwave resonant cavity, and the resonant units are coupled through passive devices; the nonlinear control component includes active devices for achieving non-reciprocal coupling and adjusting coupling amplitude and phase.

[0011] According to a second aspect of an embodiment of the present application, a control method for the intracavity vortex wave generating device according to the first aspect is provided, comprising: Adjust the gain of the nonlinear control component to make the resonant cavity system enter the nonlinear working range; Adjust the phase of the non-reciprocal coupling to the target value and determine the topological charge in the corresponding vortex wave mode; Exciting self-oscillation through a non-reciprocal coupling channel, and outputting a vortex wave carrying orbital angular momentum from the resonant cavity system; By adjusting the coupling parameters of the non-reciprocal coupling, topological charge switching or bistable switch control is achieved.

[0012] According to a third aspect of an embodiment of the present application, an acoustic particle manipulation device is provided, which adopts the intracavity vortex wave generating device described in the first aspect and uses vortex waves with different topological charge numbers to apply controllable angular momentum to the particles.

[0013] In summary, the embodiments of the present application provide an intracavity vortex wave generating device and control method. The intracavity vortex wave generating device includes a resonant cavity system and a nonlinear control component integrated in the resonant cavity system; the resonant cavity system is composed of a plurality of resonant units forming a closed loop through a coupling structure to support the resonance of the wave mode; the nonlinear control component is used to achieve adjustable non-reciprocal coupling between at least two of the resonant units; and is also used to enable the resonant cavity system to generate vortex waves carrying orbital angular momentum by adjusting the coupling parameters of the non-reciprocal coupling. By integrating the nonlinear control component in the resonant cavity system and utilizing the characteristics of the non-reciprocal coupling, vortex waves carrying orbital angular momentum are directly generated in the cavity, thereby avoiding the complexity and loss of additional beamforming elements or complex active transducer arrays required in traditional methods. By adjusting the coupling parameters of the non-reciprocal coupling, the topological charge of the generated vortex wave can be flexibly controlled, thereby achieving the generation of vortex waves with different topological charges, providing wider applicability for a variety of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0015] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, without affecting the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0016] Figure 1 A schematic diagram of an intracavity vortex wave generating device provided in an embodiment of the present application; Figure 2a A schematic diagram of a ring resonator system provided in an embodiment of the present application; Figure 2b A schematic diagram of parameter settings for the ring resonator system provided in an embodiment of the present application; Figure 3a Schematic diagram of an equivalent tight-binding model of a ring resonator system provided in an embodiment of the present application; Figure 3b A schematic diagram of a steady-state solution under nonlinear phase conditions for a ring resonator system provided in an embodiment of the present application; Figure 3c A schematic diagram of the phase distribution of the radiation field of the ring resonator system provided in an embodiment of the present application; Figure 4a and Figure 4b A schematic diagram of a vortex wave provided in an embodiment of the present application; Figure 5a and Figure 5b A schematic diagram of another vortex wave provided in an embodiment of the present application; Figure 6 A schematic diagram of the bistable characteristics test results provided in an embodiment of the present application; Figure 7 A flow chart of a control method for an intracavity vortex wave generating device provided in an embodiment of the present application; The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0018] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0019] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0020] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0021] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] Figure 1 An intracavity vortex wave generating device provided in an embodiment of the present application is shown, comprising: a resonant cavity system and a nonlinear control component integrated in the resonant cavity system; the resonant cavity system is composed of several resonant units forming a closed loop through a coupling structure to support the resonance of the wave mode; the nonlinear control component is used to achieve adjustable non-reciprocal coupling between at least two of the resonant units; and is also used to enable the resonant cavity system to generate vortex waves carrying orbital angular momentum by adjusting the coupling parameters of the non-reciprocal coupling.

[0023] At the fundamental physics level, the device achieves precise control of wave modes through the synergistic effect of the closed-loop structure of the resonant cavity system and nonlinear control components. This avoids the complex beamforming elements or multiple active transducer arrays required in traditional methods, generating vortex waves directly within the cavity, improving system efficiency and performance.

[0024] In a possible implementation, the resonant cavity system is an acoustic resonant cavity system, the resonant unit is an acoustic resonant cavity, and the coupling structure includes an acoustic pipe connecting adjacent acoustic resonant cavities.

[0025] In one possible embodiment, the properties of the coupling structure include a reciprocal coupling channel and a non-reciprocal coupling channel, wherein the reciprocal coupling channel connects all adjacent resonant units for bidirectional coupling between adjacent resonant units; and the non-reciprocal coupling channel selectively connects at least one pair of resonant units for introducing unidirectional coupling to break time reversal symmetry.

[0026] The coupling structure between the resonant units (including reciprocal and non-reciprocal coupling channels) provides a stable resonant environment, breaking the time reversal symmetry of the system through non-reciprocal coupling. Adjustable non-reciprocal coupling between the resonant units is achieved through nonlinear control components, and vortex waves carrying orbital angular momentum are generated by adjusting the coupling parameters.

[0027] In one possible embodiment, the nonlinear control component includes an active electroacoustic element, which includes an amplifier and a transducer; the amplifier is used to adjust the gain and phase of the electrical signal; the transducer includes a speaker and a microphone, which are used to inject sound waves into the resonant cavity and collect feedback signals, respectively; the amplifier controls the amplitude of the non-reciprocal coupling by gain adjustment, and controls the phase of the non-reciprocal coupling by adjusting the phase, thereby controlling the topological charge of the vortex wave.

[0028] The nonlinear control component includes an active electroacoustic element. Using an amplifier to adjust the gain and phase of the electrical signal, the amplifier controls the amplitude and phase of the nonreciprocal coupling, ultimately controlling the topological charge of the vortex wave. This efficient generation and flexible control of vortex waves achieved through active electroacoustic elements avoids the complex mechanical structures or multiple active components required in traditional methods, improving system efficiency and performance.

[0029] In one possible embodiment, the phase of the non-reciprocal coupling and the topological charge of the vortex wave satisfy a preset mapping relationship, and the preset mapping relationship includes: when the phase of the non-reciprocal coupling is -0.38π, the number of spiral rotations of the topological charge rotates 1 circle counterclockwise in the phase field; when the phase of the non-reciprocal coupling is 0.38π, the number of spiral rotations of the topological charge rotates 4 circles counterclockwise in the phase field.

[0030] By adjusting the phase of the amplifier, precise control of the vortex wave topological charge can be achieved to meet the topological charge requirements of different application scenarios.

[0031] In a possible implementation, when the phase of the non-reciprocal coupling is fixed, the gain of the amplifier is adjusted so that the resonant cavity system exhibits a bistable characteristic; and a set difference exists between a generation threshold gain and an extinction threshold gain of the vortex wave.

[0032] The bistable characteristics are used to realize history-dependent vortex wave state switching, which is suitable for new devices such as vortex switches and vortex memories, and provides a basis for realizing complex signal processing and storage functions.

[0033] At the technical level, complex multi-channel control is simplified to a single-point control. By adjusting two key parameters, the phase and gain of the nonreciprocal coupling, the topological charge of the vortex wave can be precisely controlled. This simplified control method brings significant advantages. First, the deterministic relationship between the geometric parameters of the acoustic duct (such as the 3.4mm diameter) and the coupling coefficient (κ = -60Hz) makes the system repeatable. Second, the introduction of bistability (manifested by the threshold hysteresis effect during gain adjustment) gives the device a memory function.

[0034] In a possible implementation, the resonant cavity system is a microwave resonant cavity, the resonant units are coupled through passive devices, and the nonlinear control component is composed of active devices for achieving non-reciprocal coupling and adjusting coupling amplitude and phase.

[0035] In the microwave field, the resonant cavity system is a microwave resonant cavity, where the resonant units achieve reciprocal coupling through passive coupling devices (including microstrip lines and capacitors), forming a closed loop structure. The nonlinear control component includes active devices (including microwave amplifiers) that are used to achieve nonreciprocal coupling and adjust the coupling amplitude and phase, thereby controlling the topological charge and frequency of the vortex wave. This achieves efficient vortex wave generation in the microwave frequency band and is suitable for fields such as microwave communications, radar systems, and microwave imaging.

[0036] In one possible implementation, while the phase of the nonreciprocal coupling is fixed, the amplifier gain is adjusted to enable the system to exhibit a bistable behavior between the generation and extinction of vortex waves. Specifically, when the gain reaches a certain threshold, the system begins to generate vortex waves. When the gain decreases to another threshold, the system ceases to generate vortex waves. This bistable behavior enables history-dependent vortex wave state switching, which is applicable to novel devices such as microwave switches and microwave memories, providing a foundation for implementing complex signal processing and storage functions.

[0037] The traditional generation of acoustic vortex waves (similar to "acoustic spiral waves") requires complex external equipment (such as phase plates or multi-transducer arrays), and the present application proposes a solution: 1. Generate vortex waves directly inside the acoustic resonant cavity without the need for external shaping elements. 2. Only one actively controlled electroacoustic element (speaker + microphone + amplifier) ​​is required, and by adjusting its parameters (such as phase, amplification factor), the topological charge of the vortex wave (that is, the "number of turns" of the spiral, such as -1, -4, etc.) can be changed. 3. Dynamically switchable: The "bistable" characteristics can also be used to realize the "switching" and "memory" functions of the vortex wave. The following, in conjunction with the accompanying drawings, provides a detailed example of the device and method for generating acoustic vortex waves in the cavity through a single non-reciprocal nonlinear active electroacoustic element proposed in the embodiment of the present application.

[0038] The working process of the embodiment of the present application is illustrated by an example of an acoustic vortex wave generating device operating in the frequency range of 850-1250 Hz: the vortex wave generator includes an acoustic ring resonator and an active electroacoustic element.

[0039] Part I: Acoustic Ring Resonator.

[0040] An acoustic ring resonator consists of multiple resonant units and connecting pipes, generating acoustic resonance. The specific parameters of the resonator (such as size and shape) are designed based on actual requirements. Nonreciprocal nonlinear active electroacoustic components include directional amplifiers, speakers, and microphones. These components provide nonreciprocal coupling, adjustable phase and amplification, and operate in the nonlinear range.

[0041] In an embodiment of the present application, the acoustic ring resonator is made of 3D printing of a photosensitive resin with a thickness of 6 mm, including 10 rectangular resonant cavities and connecting pipes, and a hole is drilled on the top of each rectangular resonant cavity. Figure 2a This is a schematic diagram of a ring resonator system in an embodiment of the present application; 10 rectangular resonators are connected in series through a pipe to form a ring, forming a closed acoustic loop. The top opening is used to radiate acoustic vortex waves into free space. Figure 2b This is a schematic diagram of the parameter settings for the ring resonator system in an embodiment of the present application. Specific parameters are: height h = 19.2 cm, width w = 3.4 cm, length l = 5.2 cm, ring radius r = 7.8 cm, connecting pipe spacing d = 3.4 cm, d2 = 4 cm, and radiation aperture radius (opening at the top of each cavity) r = 5 mm.

[0042] Part II: Active electroacoustic components.

[0043] The active electroacoustic component consists of a directional amplifier equipped with a DC power supply, a speaker (output), and a microphone (input). Two holes with radii of 4 mm and 6.1 mm are drilled into the side of the acoustic resonator to accommodate the speaker (small hole) and microphone (large hole) of the active component. Both the phase and amplification factor of this active electroacoustic component are adjustable. This single component implements a closed excitation-feedback loop, forming a nonlinear feedback loop, allowing the vortex wave characteristics to be controlled by adjusting the phase and gain.

[0044] Physically, the resonant frequency of each rectangular resonant cavity is 1050Hz, and the radiation loss and thermoviscous loss introduced by the top opening total 4Hz. The connecting pipes between the 2nd to 9th rectangular resonant cavities provide reciprocal coupling with a coupling coefficient of κ=-60Hz. The connecting pipes between the 1st and 10th rectangular resonant cavities provide another reciprocal coupling with a coupling coefficient of κ b =-70Hz.

[0045] Active electroacoustic components provide non-reciprocal coupling κ a , the coupling coefficient of the non-reciprocal coupling |κ a | and phase φ κa The element is adjustable, and can be controlled to operate in either a linear or nonlinear range based on factors such as amplification factor and intracavity energy. In one possible embodiment, the active electroacoustic element operates in the nonlinear range. By utilizing mode locking induced by nonlinear coupling and a structural design that breaks time reversal symmetry, the ring resonator generates self-oscillating single-mode vortex wave radiation. The topological charge of the vortex wave can be controlled by adjusting boundary parameters (such as phase and amplitude).

[0046] The following demonstrates how nonlinear coupling causes the system to lock into a specific vortex mode (l=-1 or l=-4) through a tight-binding model plus Hamiltonian calculations.

[0047] Part 1: Convert the physical device into a mathematical model and abstract the 10 actual cavities into a ring consisting of 10 coupling points.

[0048] The ring resonator system can be equivalent to Figure 3a The tight-binding model is shown, with each cavity labeled 1 to 10. Figure 3a Schematic diagram of the equivalent tight-binding model of the ring resonator system in the embodiment of the present application; 10 resonant cavities are equivalent to coupled resonant rings, Hamiltonian H describes the system state, non-reciprocal coupling (κ a ) exists between cavity 1 and cavity 10, breaking the time reversal symmetry.

[0049] Part 2: How nonlinear coupling generates vortex waves: By adjusting the phase to change the steady-state solution of the system, the mode proportion of a certain rotation direction (clockwise / counterclockwise) is calculated, so that the radiation field exhibits a corresponding stable spiral phase.

[0050] First, according to its kinetic equation Solve the steady state and obtain the nonlinear amplitude and eigenfrequency steady-state solutions of the ring resonator system at different nonlinear coupling phases, where is the eigenstate of the system (or the complex amplitude of the classical acoustic field), which describes the modal distribution of the acoustic wave in the resonant cavity. H is the Hamiltonian of the system, which includes all energy terms and coupling terms. is the time evolution operator, which represents the change of system state over time. Figure 3b Schematic diagram of the steady-state solution of the nonlinear phase of the ring resonator system in the embodiment of the present application; the x-axis is the nonlinear coupling phase φ κa , the y-axis is the nonlinear coupling amplitude, the z-axis is the frequency, and the thick line represents the self-oscillation threshold.

[0051] The Hamiltonian of the system is calculated according to the following formula:

[0052] Resonant cavity eigenterm middle, is the eigenfrequency of a single resonant cavity (e.g. 1050 Hz), which is determined by the cavity geometry and material. is the loss coefficient (imaginary part), corresponding to radiation and thermoviscous loss (such as 4Hz), and a positive value indicates energy dissipation. n ( ) are the creation and annihilation operators. Reciprocal coupling between adjacent resonant cavities middle, is the reciprocal coupling coefficient (e.g. -60Hz), which indicates the energy exchange intensity between adjacent resonant cavities (the negative sign indicates phase reversal). In, κ b is a fixed reciprocal coupling coefficient (e.g., κ between the 1st and 10th cavities) b =−60Hz). κ a (·) is a nonlinear nonreciprocal coupling introduced by active electroacoustic elements, and its amplitude |κ a | and phase φ κa Adjustable (such as φ κa =−0.38π).

[0053] exist Figure 3b The bold part in the middle mark is the minimum nonlinear amplitude threshold. When the nonlinear coupling strength exceeds the threshold, the system locks into a single mode (such as l = −1, -2, -3 and -4). That is, the nonlinear coupling phase, amplitude and eigenfrequency of the final lasing state. When φ κa =-0.38π when the l=-1 mode is locked, φ κa =0.38π when the l=-4 mode is locked.

[0054] The proportion of clockwise and counterclockwise modes in the wave function in each steady state is calculated by non-Bloch mode theory. It can be expressed as and The superposition of ,here and .

[0055] l is an integer and is related to the wave function k, that is, l≈Re(k)N / 2π, β 1,2 =e±ik is the generalized Brillouin zone. The coefficients α1 and α2 can be solved by the following eigenvalue equations:

[0056] Through this equation, we can get each eigenstate The corresponding coefficients α1 and α2. It can be found that by adjusting the boundary, the mode ratio can be adjusted so that the clockwise or counterclockwise mode is dominant (can be higher than 95%). Because the ring resonator system has openings, its wave function can be radiated into the air, from which its radiation field can be calculated. The phase of the radiation field is as follows Figure 3c As shown, Figure 3c This is a schematic diagram of the radiation field phase distribution of a ring resonator system in an embodiment of the present application. The radiation field phase exhibits a spiral variation, and the topological charge l is determined by the number and direction of phase rotation (e.g., -2π corresponds to l = -1). It can be seen that at different phases, the wave function of the lasing state is different, that is, the topological charge of the emitted radiation field is different.

[0057] Part III: Physical mechanism of bistability: When the phase amplitude modulation value is fixed, the system will exhibit a hysteresis effect: vortex waves will only be generated when the amplitude is increased to threshold A; the vortex waves will disappear only when the amplitude is reduced to threshold B; (A≠B, similar to a hysteresis loop).

[0058] Furthermore, due to the feedback mechanism of the nonlinear active element, the system exhibits a bistable characteristic: when the phase of the active electroacoustic element is fixed, increasing or decreasing the amplifier amplitude produces different phase transition points. Thus, the system supports history-dependent vortex wave state switching.

[0059] In order to verify the proposed properties, two vortex wave generation experiments were carried out in practical applications. The active electroacoustic element was tested in the nonlinear range with phases of -0.38π and 0.38π, respectively. The self-oscillating single-mode vortex wave radiation of the adjustable topological charge was demonstrated.

[0060] The frequencies and topological charges of vortex waves generated by active electroacoustic elements operating at different phases in the nonlinear range were measured. Figure 4a and Figure 4bThis is a schematic diagram of a vortex wave with a topological charge of -1 and a frequency of 950 Hz generated when the nonlinear coupling phase is -0.38π in the embodiment of the present application. When the phase of the active electroacoustic element is -0.38π, the upper surface of the ring resonator radiates a 950 Hz vortex wave, and its sound pressure curve is as follows: Figure 4a shown. Figure 4b The phase field distribution of this vortex wave is shown, and it can be found that the frequency changes by -2π, which means that the topological charge of this vortex wave is -1. In other words, at a frequency of 950Hz, the phase field rotates by -2π → the topological charge l=-1.

[0061] Figure 5a and Figure 5b The diagram of the vortex wave with a topological charge of -4 and a frequency of 1150 Hz generated when the nonlinear coupling phase is 0.38π in the embodiment of the present application is shown in FIG. When the phase of the active electroacoustic element is 0.38π, the upper surface of the ring resonator radiates a vortex wave of 1150 Hz, and its sound pressure curve is shown in FIG. Figure 5a shown. Figure 5b The phase field distribution of this vortex wave is shown, and it can be found that the frequency changes by -8π, which means that the topological charge of this vortex wave is -4. In other words, at a frequency of 1150Hz, the phase field rotates by -8π → the topological charge l=-4.

[0062] When the phase is -0.38π, a vortex wave with a frequency of 950 Hz and a topological charge of -1 is generated. When the phase is 0.38π, a vortex wave with a frequency of 1150 Hz and a topological charge of -4 is generated. These experimental results are consistent with theoretical calculations, demonstrating the effectiveness of the device. By adjusting the nonlinear coupling to other phases, vortex waves with different frequencies and topological charges can be generated.

[0063] The system exhibits a bistable characteristic, that is, when the phase is fixed, by adjusting the amplitude of the amplifier, the system can switch between the state of generating vortex waves and the state of not generating waves, and exhibits a hysteresis characteristic. Figure 6 The figure is a schematic diagram of the test results of the bistable characteristics in the embodiment of the present application. When the phase of the active electroacoustic element is -0.38π, the amplitude of the active electroacoustic element is continuously increased. At the beginning, the annular resonator does not radiate any signal. As the amplitude increases, after reaching a threshold, the upper surface of the annular resonator radiates a 950Hz vortex wave. Continuing to increase the amplitude, the vortex wave mode and frequency do not change, and the detected radiation intensity gradually stabilizes. However, when the amplitude is gradually reduced, the annular resonator generates vortex waves at the beginning, and suddenly stops radiating signals at a certain threshold. The two threshold points are not equal, showing a bistable characteristic. It can be used for acoustic memory (the "on" state stores 1, and the "off" state stores 0).

[0064] The embodiments of this application overcome the symmetry limitations of traditional acoustic vortex generation technologies by innovatively employing a single nonreciprocal, nonlinear active electroacoustic element. This single element, through a nonlinear feedback mechanism, breaks the system's linearity, reciprocity, Hermitian, and time-reversal symmetry, achieving a revolutionary approach to generating intracavity acoustic vortex waves. Compared to traditional methods that rely on external sound sources and passive elements, this approach utilizes an intracavity self-oscillation mechanism, exploiting boundary nonlinearities within the nonlinear operating range to induce mode competition. This approach achieves self-oscillation and locks onto a single, single-frequency vortex wave without the need for an additional sound source. Its operating principle is similar to that of an "acoustic vortex laser."

[0065] The advantages of this device are also reflected in the following aspects: first, it achieves real-time dynamic switching of topological charges through phase regulation, providing a new dimension for acoustic information encoding; second, the system's bistable characteristics make it applicable to vortex switches and memory devices; third, the scheme's universal design concept can be extended to generate high-order mode vortices and is applicable to multiple physical fields such as circuits, microwaves, terahertz, and optics, showing broad application prospects. Experimental verification shows that this scheme based on single-element nonlinear control is not only theoretically innovative but also has practical engineering value, opening up new avenues for the development of acoustic vortex technology.

[0066] Its principle is not only applicable to acoustic systems, but can also be extended to fields such as optics, microwaves, and terahertz, and has broad application prospects. In the field of acoustics, the device can be used for acoustic communications, and by regulating the topological charge of the vortex wave, information encoding and transmission can be achieved, thereby improving the confidentiality and capacity of communications. It can be used for particle manipulation, using the orbital angular momentum of the vortex wave to capture and rotate tiny particles, and has applications in fields such as biomedicine and materials science. In the field of optics, this principle can be applied to the generation of optical vortex waves for use in quantum information processing, optical communications, and optical imaging. By regulating the topological charge of the optical vortex wave, high-capacity optical communications and high-precision optical imaging can be achieved. In the microwave and terahertz fields, the device can be used for high-power, high-efficiency vortex wave generation for use in radar, communications, and imaging systems. By regulating the frequency and topological charge of the vortex wave, multimodal signal transmission and high-resolution imaging can be achieved.

[0067] Based on the same technical concept, the embodiment of the present application also provides a control method based on the intracavity vortex wave generating device, such as Figure 7 As shown, the method includes: Step S701: adjusting the gain of the nonlinear control component to make the resonant cavity system enter the nonlinear working range; Step S701: adjusting the phase of the non-reciprocal coupling to a target value, and determining the topological charge under the corresponding vortex wave mode; Step S702: Exciting self-oscillation through a non-reciprocal coupling channel, and outputting a vortex wave carrying orbital angular momentum from the resonant cavity system; Step S703: topological charge switching or bistable switch control is achieved by adjusting the coupling parameters of the non-reciprocal coupling.

[0068] In summary, the embodiments of the present application provide an intracavity vortex wave generating device and control method. The intracavity vortex wave generating device includes a resonant cavity system and a nonlinear control component integrated in the resonant cavity system; the resonant cavity system is composed of a plurality of resonant units forming a closed loop through a coupling structure to support the resonance of the wave mode; the nonlinear control component is used to achieve adjustable non-reciprocal coupling between at least two of the resonant units; and is also used to enable the resonant cavity system to generate vortex waves carrying orbital angular momentum by adjusting the coupling parameters of the non-reciprocal coupling. By integrating the nonlinear control component in the resonant cavity system and utilizing the characteristics of the non-reciprocal coupling, vortex waves carrying orbital angular momentum are directly generated in the cavity, thereby avoiding the complexity and loss of additional beamforming elements or multiple active transducer arrays required in traditional methods. By adjusting the coupling parameters of the non-reciprocal coupling, the topological charge of the generated vortex wave can be flexibly controlled, thereby achieving the generation of vortex waves with different topological charges, providing wider applicability for various applications.

[0069] Based on the same technical concept, an embodiment of the present application also provides an acoustic particle manipulation device, which adopts the intracavity vortex wave generating device and uses vortex waves with different topological charge numbers to apply controllable angular momentum to the particles.

[0070] It should be noted that the above embodiments illustrate rather than limit the present application, and that a person skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbols placed between brackets should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present application may be implemented by means of hardware comprising several different elements and by means of appropriately programmed computers. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0071] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0072] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An intracavity vortex wave generating device, characterized in that: include: A resonant cavity system and a nonlinear control component integrated in the resonant cavity system; The resonant cavity system is composed of a plurality of resonant units forming a closed loop through a coupling structure, which is used to support the resonance of the wave mode; The nonlinear control component is used to achieve adjustable non-reciprocal coupling between at least two of the resonant units; and is also used to enable the resonant cavity system to generate vortex waves carrying orbital angular momentum by adjusting the coupling parameters of the non-reciprocal coupling.

2. The device according to claim 1, wherein The resonant cavity system is an acoustic resonant cavity system, the resonant unit is an acoustic resonant cavity, and the coupling structure includes an acoustic pipe connecting adjacent acoustic resonant cavities.

3. The device according to claim 2, wherein The properties of the coupling structure include a reciprocal coupling channel and a non-reciprocal coupling channel, wherein the reciprocal coupling channel connects all adjacent resonant units for bidirectional coupling between adjacent resonant units; The non-reciprocal coupling channel selectively connects at least one pair of resonant units, and is used to introduce unidirectional coupling to break the time reversal symmetry.

4. The device according to claim 1, wherein The nonlinear control component includes an active electroacoustic element, which includes an amplifier and a transducer; the amplifier is used to adjust the gain and phase of the electrical signal; the transducer includes a speaker and a microphone, which are used to inject sound waves into the resonant cavity and collect feedback signals respectively; The amplifier controls the amplitude of the non-reciprocal coupling by gain adjustment, and controls the phase of the non-reciprocal coupling by phase adjustment, thereby controlling the topological charge of the vortex wave.

5. The device according to claim 4, characterized in that The phase of the non-reciprocal coupling and the topological charge of the vortex wave satisfy a preset mapping relationship, and the preset mapping relationship includes: when the phase of the non-reciprocal coupling is -0.38π, the number of spiral rotations of the topological charge rotates 1 circle counterclockwise in the phase field; when the phase of the non-reciprocal coupling is 0.38π, the number of spiral rotations of the topological charge rotates 4 circles counterclockwise in the phase field.

6. The device according to claim 4, characterized in that When the phase of the non-reciprocal coupling is fixed, the gain of the amplifier is adjusted so that the resonant cavity system exhibits a bistable characteristic; and a set difference exists between the generation threshold gain and the disappearance threshold gain of the vortex wave.

7. The device according to claim 1, wherein The resonant cavity system is a microwave resonant cavity, and the resonant units are coupled through passive devices; the nonlinear control component includes active devices for realizing non-reciprocal coupling and adjusting coupling amplitude and phase.

8. A control method for the intracavity vortex wave generating device according to any one of claims 1 to 7, characterized in that: include: Adjust the gain of the nonlinear control component to make the resonant cavity system enter the nonlinear working range; Adjust the phase of the non-reciprocal coupling to the target value and determine the topological charge under the corresponding vortex wave mode; Exciting self-oscillation through a non-reciprocal coupling channel, and outputting a vortex wave carrying orbital angular momentum from the resonant cavity system; By adjusting the coupling parameters of the non-reciprocal coupling, topological charge switching or bistable switch control is achieved.

9. An acoustic particle manipulation device, characterized in that: The intracavity vortex wave generating device according to any one of claims 1 to 7 is used to apply controllable angular momentum to the particles using vortex waves with different topological charge numbers.

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