Topological Lamb waveguide device with wide aperture
By arraying phonon crystal cells on a thin film substrate, stacking ram waves using micro-nano cylindrical structures with varying cross-sectional radii, and combining the height difference to reduce the group speed, the problems of back reflection and wave velocity matching in the prior art are solved, and high-precision ram wave operation and broadband matching are achieved.
Patent Information
- Application Number
- CN202510163551.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-14
- Publication Date
- 2025-06-10
AI Technical Summary
The prior art is difficult to effectively suppress the back reflection caused by bending angles and defects on the Lamb wave transmission path, and it is difficult to match the broadband slow waveguide and broadband IDTs without introducing additional interpolation losses.
A wide aperture topological Lamb waveguide device is designed. By arraying phonon crystal cells on a thin film substrate, using a micro-nano cylindrical structure with varying cross-sectional radius, the Lamb wave "semi-metal" and "insulator" are stacked together to achieve reflection-free transmission, and by forming a height difference for the micro-nano cylindrical structure, the group speed is reduced to match the broadband slow waveguide and broadband IDTs.
The suppression of the back reflection of the Lamb wave is achieved, the accuracy of the Lamb wave operation is improved, and the matching of the broadband slow wave guide and broadband IDTs is achieved without introducing additional interpolation losses, thereby retaining the characteristics of defect immunity.
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Figure CN120128121A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a Lamb waveguide device, belonging to the technical field of electroacoustic components. Background Art
[0002] Lamb wave is a special elastic wave coupled by transverse wave and longitudinal wave, which has been widely applied in the fields of signal processing and sensing in wireless communication. In addition, it has also developed vigorously in the fields of acoustic / photonic crystals, biomedicine, and structural damage detection. Increasing the regulation accuracy of Lamb wave will be of great benefit to these researches. Therefore, how to obtain a high-quality Lamb wave waveguide has become a problem worthy of study.
[0003] The prior art has adopted a suspended beam structure, restricted the transmission area through the phonon crystal bandgap, and achieved the focusing of Lamb wave by setting the refractive index gradient to improve the operation accuracy of Lamb wave. However, there are still the following problems: (1) How to suppress the back reflection caused by the bends and defects on the Lamb wave transmission path; (2) How to effectively reduce the wave velocity of Lamb wave and achieve the matching of broadband slow wave waveguide and broadband IDTs without introducing additional insertion loss. Summary of the Invention
[0004] Aiming at the defects of the above-mentioned prior art, the present invention provides a topological Lamb waveguide device with a wide aperture to achieve the suppression of the back reflection of Lamb wave.
[0005] The technical solution of the present invention is as follows: A topological Lamb waveguide device with a wide aperture includes a thin film substrate. The surface of the thin film substrate is provided with a first region, a second region, and a third region arranged in sequence. The first region, the second region, and the third region are all composed of phonon crystal unit cells arranged in an array. The phonon crystal unit cell includes two micro-nano cylinder structures. The two micro-nano cylinder structures in the phonon crystal unit cell of the second region have the same size. The two micro-nano cylinder structures in the phonon crystal unit cell of the first region and the third region have different cross-sectional radii. The arrangement of all the micro-nano cylinder structures in the first region is mirror-symmetrical with respect to the second region to the arrangement of all the micro-nano cylinder structures in the third region.
[0006] Further, the cross-sectional radius of the micro-nano cylinder structure is 0.2a - 0.3a, where a is the lattice period of the phonon crystal unit cell.
[0007] Further, the difference in the cross-sectional radii of the two micro-nano cylinder structures in the phonon crystal unit cell of the first region and the third region is 0.01a - 0.02a.
[0008] Further, in order to reduce the Lamb wave velocity and achieve the matching between the broadband slow-wave waveguide and the broadband IDTs, the height of the micro-nano cylindrical structure with a smaller cross-sectional radius in the phononic crystal unit cells of the first region and the third region is lower than that of the micro-nano cylindrical structure with a larger cross-sectional radius.
[0009] Further, the junctions between the first region and the second region and between the third region and the second region are micro-nano cylindrical structures with a smaller cross-sectional radius.
[0010] Further, the height difference between the two micro-nano cylindrical structures in the phononic crystal unit cells of the first region and the third region is 0.02a or more, preferably 0.04a to 0.16a.
[0011] Further, the phononic crystal unit cells are arranged in an array to form a hexagonal lattice.
[0012] Further, the thin film substrate is one of a silicon-based thin film and a piezoelectric thin film, such as single-crystalline silicon, SiO 2 , SiC, SiN, LiTaO 3 , AlN, GaN, LiNbO 3 or other piezoelectric 2D materials such as monolayer transition metal dichalcogenides, binary compounds of group III-V elements, and single chalcogenide materials.
[0013] Further, the thickness of the thin film substrate is 100 to 500 nm.
[0014] Compared with the prior art, the advantages of the technical solution provided by the present invention are as follows:
[0015] By using micro-nano cylindrical structures with unequal cross-sectional radii, the present invention stacks the Lamb wave "semi-metal" and "insulator" together, obtaining a transmission state that transmits without reflection within a wide width range, realizing the suppression of back reflection caused by bends and defects, and improving the accuracy of Lamb wave operation.
[0016] Furthermore, by forming a height difference in the micro-nano cylindrical structures with unequal cross-sectional radii, the group velocity of the extended valley-locked state is reduced. At the same time, the defect-immune property is still retained, and the matching between the broadband slow-wave waveguide and the broadband IDTs is achieved. In addition, an excitable energy band symmetric with respect to the waveguide center is obtained. Description of the Drawings
[0017] Figure 1 Schematic diagram of the wide-aperture topological Lamb wave waveguide device of Example 1 and the phononic crystal unit cell structures of the first region, the second region, and the third region.
[0018] Figure 2The phonon crystal unit cell energy band diagram of the second region of the wide-aperture topological Lamb waveguide device of Example 1.
[0019] Figure 3 The phonon crystal unit cell energy band diagrams of the first and third regions of the wide-aperture topological Lamb waveguide device of Example 1.
[0020] Figure 4 The projected energy band along the Kx direction of the wide-aperture topological Lamb waveguide device of Example 1. The green energy band corresponds to EVLS (Lamb wave extended valley locked state) and the Z-direction deformation field distribution of EVLS.
[0021] Figure 5 The schematic diagrams of the phonon crystal unit cell structures of the first, second, and third regions of the wide-aperture topological Lamb waveguide device of Example 2.
[0022] Figure 6 The projected energy band along the Kx direction of the wide-aperture topological Lamb waveguide device of Example 2. The green energy band corresponds to EVLS and the Z-direction deformation field distribution of EVLS.
[0023] Figure 7 The schematic diagrams of the wide-aperture topological Lamb waveguide device of Example 3 and the phonon crystal unit cell structures of the first, second, and third regions.
[0024] Figure 8 The projected energy band along the Kx direction of the wide-aperture topological Lamb waveguide device of Example 3 when dh = 0.02*a and the Z-direction deformation field distribution of EVLS.
[0025] Figure 9 The projected energy band along the Kx direction of the wide-aperture topological Lamb waveguide device of Example 3 when dh = 0.04*a and the Z-direction deformation field distribution of EVLS.
[0026] Figure 10 The schematic diagrams of the wide-aperture topological Lamb waveguide device of Example 4 and the phonon crystal unit cell structures of the first, second, and third regions.
[0027] Figure 11 The projected energy bands along the Kx direction of the wide-aperture topological Lamb waveguide device of Example 4 at different dhs and the Z-direction deformation field distribution of EVLS.
[0028] Figure 12 The wave speed calculation result diagram of the wide-aperture topological Lamb waveguide device of Example 4 at different dhs.
[0029] Figure 13 The Z-direction deformation field (before introducing defects) of the wide-aperture topological Lamb waveguide device of Example 4 at 1.7012 GHz.
[0030] Figure 14 Z-direction deformation field of the wide-aperture topological Lamb waveguide device in Example 4 at 1.7012 GHz (after introducing defects).
[0031] Figure 15 Transmission spectrum diagram of the wide-aperture topological Lamb waveguide device in Example 4. Detailed implementation manners
[0032] The present invention will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading this description, various equivalent forms of modification of this description by those skilled in the art all fall within the scope defined by the appended claims of this application.
[0033] Example 1, as Figure 1As shown in the figure, the single-crystalline silicon thin-film substrate 100 of the wide-aperture topological Lamb waveguide device in this embodiment, the thickness of the single-crystalline silicon thin-film substrate 100 can be 100 - 500 nm, and in this embodiment it is 300 nm. The top surface of the single-crystalline silicon thin-film substrate 100 is arranged with phononic crystal unit cells in an array to form a hexagonal lattice with a lattice period a of 1 μm. Each phononic crystal unit cell is composed of two micro-nano cylinder structures 200, and the cross-sectional radius of the micro-nano cylinder structure 200 is 0.2a - 0.3a. According to the different sizes of the two micro-nano cylinder structures 200 in the phononic crystal unit cell, the top surface of the single-crystalline silicon thin-film substrate 100 is divided into a first region A, a second region B, and a third region C arranged in sequence, where the second region B is in the middle. The two micro-nano cylinder structures 201, 202 in the phononic crystal unit cell of the second region B have the same size. In this embodiment, the heights h1 = h2 = 0.27a of the two micro-nano cylinder structures 201, 202, and the radii r1 = r2 = 0.24a. The heights of the two micro-nano cylinder structures 203, 204 in the phononic crystal unit cell of the first region A are the same and are the same as the heights of the micro-nano cylinder structures 201, 202 in the phononic crystal unit cell of the second region B, h3 = h4 = 0.27a. The cross-sectional radii of the two micro-nano cylinder structures 203, 204 in the phononic crystal unit cell of the first region A are different, and the difference in cross-sectional radii is 0.01a - 0.02a. In this embodiment, r3 = 0.93 * r4, r4 = 0.24a, where the number 3 represents the micro-nano cylinder structure 203 farther from the second region B in the phononic crystal unit cell, and the number 4 represents the micro-nano cylinder structure 204 closer to the second region B in the phononic crystal unit cell. The heights of the two micro-nano cylinder structures 205, 206 in the phononic crystal unit cell of the third region C are the same and are the same as the heights of the micro-nano cylinder structures 201, 202 in the phononic crystal unit cell of the second region B, h5 = h6 = 0.27a. The radii of the two micro-nano cylinder structures 205, 206 in the phononic crystal unit cell of the third region C are different, r5 = 0.24a, r6 = 0.93 * r1, where the number 5 represents the micro-nano cylinder structure 205 closer to the second region B in the phononic crystal unit cell, and the number 6 represents the micro-nano cylinder structure 206 farther from the second region B in the phononic crystal unit cell. At the junction of the first region A and the second region B is the micro-nano cylinder structure 204 with a larger cross-sectional radius. At the junction of the third region C and the second region B is the micro-nano cylinder structure 205 with a larger cross-sectional radius. The arrangement of all the micro-nano cylinder structures 203, 204 in the first region A and the arrangement of all the micro-nano cylinder structures 205, 206 in the third region C are mirror-symmetrical about the second region B.
[0034] As Figure 2 shown, the two micro-nano cylinder structures 201, 202 in the phononic crystal unit cell of the second region B have the same size, and the difference in cross-sectional radius is 0. The phononic crystal exhibits semi-metallic properties: there are two energy bands intersecting, and these two energy bands only intersect at the K / K' point in the first Brillouin zone, and this point is called the Dirac point; As Figure 3As shown in the figure, the cross-sectional radius difference between the two micro-nano cylinder structures 200 in the phonon crystal unit cells of the first region A and the third region C is not zero, breaking the spatial inversion symmetry of the phonon crystal and thus breaking the Dirac points. A complete bandgap appears near the original Dirac points, and flux vortices of Lamb waves can be observed at the K / K' points, which are the characteristic features of the emergence of valley states. The projected energy bands along the Kx direction and the Z-direction deformation field distribution calculated using COMSOL Multiphysics are as Figure 4 shown. It can be seen that: a band passing through the K and K' points appears near the bandgap frequency range corresponding to the first region A and the third region C ( Figure 4 the green band in the figure), and the propagation mode corresponding to this band has the characteristic of momentum-valley locking (i.e., at the K valley, the group velocity is negative, and at the K' valley, the group velocity is positive), and the propagated energy is mainly localized in the second region B. This mode is the extended valley-locked state (EVLS) of Lamb waves.
[0035] Example 2, as Figure 5 shown. The wide-aperture topological Lamb waveguide device of this example is based on Example 1, and the positions of the two micro-nano cylinder structures 200 in the phonon crystal unit cells of the first region A and the third region C are interchanged, that is, the cross-sectional radius of the micro-nano cylinder structure 203 farther from the second region B in the phonon crystal unit cell of the first region A is larger, and the cross-sectional radius of the micro-nano cylinder structure 204 closer to the second region B is smaller. Similarly, the cross-sectional radius of the micro-nano cylinder structure 206 farther from the second region B in the phonon crystal unit cell of the third region C is larger, and the cross-sectional radius of the micro-nano cylinder structure 205 closer to the second region B is smaller. At the junction of the first region A and the second region B is the micro-nano cylinder structure 204 with a smaller cross-sectional radius, and at the junction of the third region C and the second region B is the micro-nano cylinder structure 205 with a smaller cross-sectional radius. The arrangement of all the micro-nano cylinder structures 203, 204 in the first region A and the arrangement of all the micro-nano cylinder structures 205, 206 in the third region C are mirror-symmetric about the second region B. The remaining features are the same as those in Example 1.
[0036] The projected energy bands along the Kx direction and the Z-direction deformation field distribution calculated using COMSOL Multiphysics are as Figure 6 shown, and it can be seen that the results are consistent with those in Example 1.
[0037] Example 3, as Figure 7As shown, the wide-aperture topological Lamb waveguide device of this embodiment is based on Embodiment 1. In the phononic crystal unit cells of the first region A and the third region C, the heights of the two micro-nano cylinder structures 200 are different. In the phononic crystal unit cell of the first region A, the height of the micro-nano cylinder structure 203 farther from the second region B is lower, and the height of the micro-nano cylinder structure 204 closer to the second region B is higher. The height difference between the two is dh = 0.02a. Similarly, in the phononic crystal unit cell of the third region C, the height of the micro-nano cylinder structure 206 farther from the second region B is lower, and the height of the micro-nano cylinder structure 205 closer to the second region B is higher. The height difference between the two is dh = 0.02a. The remaining features are the same as those in Embodiment 1.
[0038] The projected energy bands along the Kx direction and the Z-direction deformation field distribution calculated by COMSOL Multiphysics are as Figure 8 shown. The green energy bands correspond to symmetric modes, and the purple energy bands correspond to antisymmetric modes (symmetric / antisymmetric modes are relative to the waveguide center). Although one green energy band has a low group velocity near 1.675 GHz, the slopes of other symmetric modes in this frequency range are different and are not suitable for actual engineering designs.
[0039] Further adjust the height difference dh = 0.04a between the two micro-nano cylinder structures 200 in the phononic crystal unit cells of the first region A and the third region C. The projected energy bands along the Kx direction and the Z-direction deformation field distribution calculated by COMSOL Multiphysics are as Figure 9 shown. The projected energy bands can still be classified into two groups: the green energy bands correspond to symmetric modes, and the purple energy bands correspond to antisymmetric modes. At this time, one purple energy band has a low slope near 1.68 GHz, and there is only one mode in the same frequency range. However, the dominant mode of the waveguide is the antisymmetric mode, which is also not suitable for actual engineering designs.
[0040] Embodiment 4, as Figure 10 shown, the wide-aperture topological Lamb waveguide device of this embodiment is based on Embodiment 2. In the phononic crystal unit cells of the first region A and the third region C, the heights of the two micro-nano cylinder structures 200 are different. In the phononic crystal unit cell of the first region A, the height of the micro-nano cylinder structure 201 farther from the second region B is higher, and the height of the micro-nano cylinder structure 202 closer to the second region B is lower. The height difference between the two is dh = 0.02a. Similarly, in the phononic crystal unit cell of the third region C, the height of the micro-nano cylinder structure 206 farther from the second region B is higher, and the height of the micro-nano cylinder structure 205 closer to the second region B is lower. The height difference between the two is dh = 0.02a. The remaining features are the same as those in Embodiment 2.
[0041] Further adjust the height difference dh = 0.04a, 0.08a, 0.12a, 0.16a of the two micro-nano cylinder structures 200 in the phononic crystal unit cells of the first region A and the third region C. The projected energy bands along the Kx direction and the Z-direction deformation field distribution calculated by COMSOL Multiphysics are as Figure 11 shown. The frequency range corresponding to EVLS continues to decrease, and the energy bands are continuously "flattened". In addition, within the frequency range corresponding to EVLS, there is only one symmetric mode. As Figure 12 shown, as dh continues to increase, the wave velocity of EVLS continuously decreases. When dh = 0.16a, the wave velocity can be reduced to about 450 m / s. And the change of the wave velocity with frequency is very small. When dh = 0.12a, the wave velocity hardly changes with the change of frequency. And in actual engineering design, it is exactly hoped that the wave velocity remains consistent within the required frequency range, because this is beneficial to broadening the working bandwidth of the slow wave waveguide.
[0042] The wide-aperture topological Lamb waveguide device of Example 4 still retains the property of defect immunity. Using a line source to simulate the plane wave in actual engineering, the Z-direction deformation field at 1.7012 GHz when dh = 0.12a is as Figure 13 、 14 shown: Before introducing the defect ( Figure 13 ), the line source can only excite the symmetric mode in the transmission region of EVLS. After introducing the defect ( Figure 14 ), the line source still excites the symmetric mode, and the field distribution in the region near the defect hardly changes due to the presence of the defect ( Figure 14 the attached figures in the black dotted box). Respectively perform energy integration on the regions corresponding to the green and purple boxes in Figure 14 , and define the ratio of the two as the transmittance (Integration2 / Integration1). At different frequencies, the calculated transmittance spectrum is as Figure 15 shown: Within the bandwidth range shown in the gray area, the transmittance basically fluctuates around 1. It should be noted that at the upper boundary of the gray area, the transmittance suddenly drops, which is because the slope of this boundary in the energy band diagram is very flat and the wave velocity is extremely low, resulting in the energy being localized and unable to be transmitted.
[0043] Finally, it should be pointed out that in the above embodiments, a single-crystalline silicon thin film substrate is used as the device substrate, and the device substrate can also be, for example, SiO 2 , SiC, SiN, LiTaO 3 , AlN, GaN, LiNbO 3 or other piezoelectric 2D materials such as monolayer transition metal dichalcogenides, binary compounds of group III-V elements, and single chalcogenide materials.
Claims
1. A wide aperture topological Lamb waveguide device, comprising a thin film substrate, characterized in that: The surface of the thin film substrate is provided with a first zone, a second zone and a third zone arranged in sequence, the first zone, the second zone and the third zone are all composed of phononic crystal cells arranged in an array, the phononic crystal cell includes two micro-nano cylindrical structures, the two micro-nano cylindrical structures in the phononic crystal cell in the second zone have the same size, the two micro-nano cylindrical structures in the phononic crystal cell in the first zone and the third zone have different cross-sectional radii, and the arrangement of all the micro-nano cylindrical structures in the first zone and the arrangement of all the micro-nano cylindrical structures in the third zone are mirror-symmetrical about the second zone.
2. The wide aperture topological Lamb waveguide device according to claim 1, characterized in that: The cross-sectional radius of the micro-nano cylindrical structure is 0.2a-0.3a, where a is the lattice period of the phononic crystal unit cell.
3. The wide aperture topological Lamb waveguide device according to claim 2, characterized in that: The difference in cross-sectional radius between the two micro-nano cylindrical structures in the phononic crystal unit cell of the first zone and the third zone is 0.01a-0.02a.
4. The wide aperture topological Lamb waveguide device according to claim 1, characterized in that: The height of the micro-nano cylindrical structure with a small cross-sectional radius in the phononic crystal unit cell of the first zone and the third zone is lower than the height of the micro-nano cylindrical structure with a large cross-sectional radius.
5. The wide aperture topological Lamb waveguide device according to claim 4, characterized in that: The junction between the first area and the second area and the junction between the third area and the second area are micro-nano cylindrical structures with small cross-sectional radius.
6. The wide aperture topological Lamb waveguide device according to claim 4, characterized in that: The height difference between the two micro-nano cylindrical structures in the phononic crystal unit cell of the first zone and the third zone is greater than 0.02a.
7. The wide aperture topological Lamb waveguide device according to claim 4, characterized in that: The height difference between the two micro-nano cylindrical structures in the phononic crystal unit cell of the first zone and the third zone is 0.04a-0.16a.
8. The wide aperture topological Lamb waveguide device according to any one of claims 1 to 7, characterized in that: The phononic crystal unit cell array is arranged to form a regular hexagonal lattice.
9. The wide aperture topological Lamb waveguide device according to any one of claims 1 to 7, characterized in that: The film substrate is one of a silicon-based film and a piezoelectric film.
10. The wide aperture topological Lamb waveguide device according to any one of claims 1 to 7, characterized in that: The thickness of the thin film substrate is 100-500nm.