Terahertz vortex phase plate based on dual-band staggered metasurface

Abstract

The invention relates to the technical field of optical devices, in particular to a terahertz vortex phase plate based on a dual-band staggered metasurface. Wherein the metasurface is composed of a plurality of metasurface units which are periodically arranged, and each metasurface unit sequentially comprises a metal structure layer, an intermediate dielectric layer and a metal reflecting layer from top to bottom; wherein the metal structure layer comprises two metal split rings which are concentrically arranged, and vortex wave beams with different topological charges at different frequency points are generated by respectively controlling the rotation angles of the two metal split rings; the phase at different frequency bands is controlled based on single rotation of each metal split ring by regulating and controlling electromagnetic coupling between the two metal split rings. The phase plate is simple in structure, light and thin, integrated installation is facilitated, cost is reduced at the same time, independent regulation and control of two terahertz waves of different frequency bands can be achieved under the condition that a phase change material is not introduced, the generation requirement of a multi-mode vortex beam is met, and the frequency spectrum utilization rate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and more particularly to a terahertz vortex phase plate based on a dual-band misaligned metasurface. Background Art

[0002] As a waveband in the electromagnetic spectrum with a frequency higher than that of microwaves and lower than that of visible light, terahertz waves have superior characteristics such as broadband, high resolution, low energy, high penetration, and transience, and have important application values in both the field of frontier scientific research and the field of industrial technology. In recent years, terahertz wave generation technology has played an increasingly important role in research such as charge carrier dynamics, excitation of the superconducting state of materials, coherent phonon dynamics, all-optical electron beam acceleration, biomolecular structure dynamics, and quantum state regulation.

[0003] A vortex beam is a beam with a spiral optical phase structure, and its phase distribution has potential application values in emerging fields such as high-resolution terahertz imaging, electron acceleration, and quantum state manipulation. Currently, the main methods for generating terahertz vortex waves include holography, spiral phase plates, and metasurfaces. Holography is widely used, but the implementation process is complex, and there is a lack of a mature spatial modulator in the terahertz band; the working frequency band of the spiral phase plate is narrow and the thickness is large, and the quality of the vortex beam generated at different frequencies is inconsistent; a metasurface is a two-dimensional artificial structure composed of sub-wavelength-sized unit periods or non-periods, and has more excellent electromagnetic regulation capabilities compared to materials existing in nature, which is beneficial to the generation of vortex waves.

[0004] However, the existing terahertz vortex phase plates still have the following defects: (1) Most optical band devices cannot be directly used in terahertz systems due to the excessive loss of their materials in the terahertz band, and appropriate materials and processes need to be selected to fabricate terahertz devices; (2) In recent years, devices for generating terahertz vortex beams are mostly limited to topological charges of 1 and 2. It is difficult to improve the topological charge of the terahertz vortex phase plate, and there is little research on terahertz vortex beam control devices with larger topological charges (l≥3); (3) Using a transmissive metasurface to generate terahertz vortex beams has the problem of low transmittance, resulting in low working efficiency; (4) In existing research, most terahertz vortex phase plates can only generate terahertz vortex beams at a single frequency point, and cannot generate multi-band vortex beams without changing the structure or introducing phase change materials. Therefore, how to provide a terahertz vortex phase plate that can efficiently generate high-order topological charge terahertz vortex beams is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The present invention aims to at least improve one of the technical problems existing in the prior art. To this end, the present invention proposes a terahertz vortex phase plate based on a dual-band misaligned metasurface.

[0006] The technical solution of the present invention is as follows: A terahertz vortex phase plate based on a dual-band misaligned metasurface, wherein the metasurface is composed of a plurality of metasurface units arranged periodically, and each metasurface unit includes a metal structure layer, an intermediate dielectric layer, and a metal reflection layer from top to bottom in sequence; wherein, the metal structure layer includes: Two concentrically arranged metal split rings, by respectively controlling the rotation angles of the two metal split rings to generate vortex beams with different topological charge numbers at different frequency points, and by weakening the electromagnetic coupling between the two metal split rings to achieve the control of the phase at different frequency bands based on the single rotation of each metal split ring.

[0007] In a possible technical solution, further, the metal split ring includes: A first metal split ring, disposed on the intermediate dielectric layer; A second metal split ring, disposed outside the first metal split ring and having the same center as the first metal split ring.

[0008] In a possible technical solution, further, by respectively controlling the rotation angles of the two metal split rings to generate vortex beams with different topological charge numbers at different frequency points, specifically: When rotating the first metal split ring, a vortex beam with a topological charge of -1 is generated at the 1.35 THz frequency band; When rotating the second metal split ring, a vortex beam with a topological charge of 3 is generated at the 0.47 THz frequency band.

[0009] In a possible technical solution, further, the opening angle range of the first metal split ring is 30° to 60°, the outer diameter is 21 μm to 25 μm, and the inner diameter is 16 μm to 20 μm.

[0010] In a possible technical solution, further, the opening angle range of the second metal split ring is 30° to 60°, the outer diameter is 46 μm to 50 μm, and the inner diameter is 41 μm to 45 μm.

[0011] In a possible technical solution, further, the arrangement period of the metasurface unit is p = 110 μm to 120 μm, wherein, The thicknesses of both the metal structure layer and the metal reflection layer are not less than 0.2 μm; The thickness range of the intermediate dielectric layer is 75 to 125 μm.

[0012] In a possible technical solution, further, in each metasurface unit, the centers of the two metal split rings, the geometric center of the middle dielectric layer, and the geometric center of the metal reflection layer are all located on the same vertical line.

[0013] In a possible technical solution, further, the middle dielectric layer is polyimide, with a relative dielectric constant of 3.5 and a tangent loss in the range of 0.001 to 0.005.

[0014] In a possible technical solution, further, the metal structure layer and the metal reflection layer are made of the same material.

[0015] In a possible technical solution, further, the material is any one of gold, silver, copper, and aluminum.

[0016] The terahertz vortex phase plate based on the dual-band misaligned metasurface according to the present invention is formed by periodically arranging metasurface units in the same plane. Utilizing the modulation ability of the metasurface device on terahertz waves, by respectively rotating the metal split rings, the generation of vortex beams can be achieved within two different terahertz frequency ranges. While generating terahertz vortex beams with larger topological charge numbers (l≥3), it also lays a foundation for the subsequent research on the application of terahertz vortex beams.

[0017] Compared with the prior art, the terahertz vortex phase plate based on the dual-band misaligned metasurface provided by the present invention has the following advantages: (1) Small volume, light weight, and high integration: This phase plate adopts metasurface technology, with a simple, thin, and light structure, which is convenient to be integrated into complex optical or communication systems, and at the same time reduces the manufacturing and usage costs.

[0018] (2) Dual-band regulation and strong flexible regulation ability: Without introducing phase change materials, through the structural design of dual-ring misalignment, this phase plate can independently regulate terahertz waves in two different frequency bands, meet the generation requirements of multi-modal vortex beams, and improve the spectral utilization rate.

[0019] (3) Potential for multi-scenario applications: This phase plate is not only applicable to the communication field, but also can be used in scenarios such as radar, high-resolution imaging, and energy transmission, demonstrating broad application potential in the field of electromagnetic regulation.

[0020] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0022] Figure 1 It is a schematic diagram of the overall structure of the terahertz vortex phase plate based on the dual-band misaligned metasurface of the present invention; Figure 2 It is a schematic diagram of the structure of the metasurface unit; Figure 3 It is a schematic diagram of the structural design of the metal structure layer of the metasurface unit; Figure 4 It is a schematic diagram of the amplitude and phase when a circularly polarized wave is incident while simultaneously rotating the metal layer structure in the embodiment of the present invention; Figure 5 It is a schematic diagram of the amplitude and phase when a circularly polarized wave is incident while the outer open ring of the metal structure layer rotates in the embodiment of the present invention; Figure 6 It is a schematic diagram of the amplitude and phase when a circularly polarized wave is incident while the inner open ring of the metal structure layer rotates in the embodiment of the present invention; Figure 7 It is a schematic diagram of the far-field distribution of the vortex wave generated by the rotation of the outer ring in the embodiment of the present invention; Figure 8 It is a schematic diagram of the far-field distribution of the vortex wave generated by the rotation of the inner ring in the embodiment of the present invention; Figure 9 It is a schematic diagram of the far-field beam generated by the rotation of the inner and outer rings in the embodiment of the present invention; Figure 10 It is a schematic diagram of the influence of different materials of the metal structure layer on the performance in the embodiment of the present invention; Figure 11 It is a schematic diagram of the influence of the thickness of the dielectric layer on the performance in the embodiment of the present invention; Figure 12 It is a schematic diagram of the influence of the inner diameter and outer diameter of the first metal open ring on the performance in the embodiment of the present invention; Figure 13 It is a schematic diagram of the influence of the inner diameter and outer diameter of the second metal open ring on the performance in the embodiment of the present invention.

[0023] Reference numerals: 10. Metasurface unit; 100. Metal structure layer; 110. First metal open ring; 120. Second metal open ring; 200. Intermediate dielectric layer; 300. Metal reflection layer. Detailed implementation manners

[0024] Embodiments of the present invention will be described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0027] In the specification and claims of the present application and the above-mentioned drawings, the terms "first", "second", "third", etc. are used to distinguish different objects and are not used to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a series of steps or units are included, or optionally, steps or units not listed are also included, or optionally, other steps or units inherent to these processes, methods, products or devices are also included.

[0028] Embodiment 1 As Figures 1 to 9 shown, this embodiment provides a terahertz vortex phase plate based on a dual-band misaligned metasurface. Among them, the metasurface is composed of a number of metasurface units 10 arranged in a periodic manner. Each metasurface unit 10 includes a metal structure layer 100, an intermediate dielectric layer 200, and a metal reflection layer 300 from top to bottom in sequence, and there is no gap between adjacent structure layers; among them, the metal structure layer includes: The first metal split ring 110 and the second metal split ring 120 have the same center of the circle in terms of their positions. The first metal split ring 110 is disposed on the intermediate dielectric layer 200; the second metal split ring 120 is disposed outside the first metal split ring 110 and has the same center of the circle as the first metal split ring 110. By separately controlling the rotation angles of the two metal split rings, vortex beams with different topological charge numbers at different frequency points are generated. Specifically, when the first metal split ring 110 is rotated, a vortex beam with a topological charge of -1 is generated in the 1.35 THz frequency band; when the second metal split ring 120 is rotated, a vortex beam with a topological charge of 3 is generated in the 0.47 THz frequency band. By weakening the electromagnetic coupling between the two metal split rings, the phase at each different frequency band can be controlled based on the single rotation of each metal split ring. Specifically, by rotating one of the metal split rings alone while the other metal split ring remains stationary, the phase at a specific frequency point can be accurately regulated independently.

[0029] It should be noted that the opening angle β of the first metal split ring 110 ranges from 30° to 60°, the outer diameter r2 is from 21 μm to 25 μm, and the inner diameter r1 is from 16 μm to 20 μm. The opening angle range of the second metal split ring 120 is from 30° to 60°, the outer diameter r4 is from 46 μm to 50 μm, and the inner diameter r3 is from 41 μm to 45 μm. Preferably, in this embodiment, the outer diameter r2 of the first metal split ring 110 is 23 μm, the inner diameter r1 is 18 μm, the opening angle of the first metal split ring 110 is 30°, the outer diameter r4 of the second metal split ring 120 is 48 μm, the inner diameter r3 is 43 μm, and the opening angle of the second metal split ring 120 is 30°, as Figure 3 shown.

[0030] It should be noted that the arrangement period of the metasurface unit 10 is p = 110 μm to 120 μm, where the thicknesses of the metal structure layer 100 and the metal reflection layer 300 are both not less than 0.2 μm; the thickness range of the intermediate dielectric layer 200 is from 75 to 125 μm. In this embodiment, the thicknesses of the metal structure layer 100 and the metal reflection layer 300 are both 0.2 μm; the arrangement period of the metasurface unit 10 is p = 110 μm, and the thickness t1 of the intermediate dielectric layer 200 is 100 μm.

[0031] It should be noted that in each metasurface unit 10, the centers of the two metal split rings, the geometric centers of the intermediate dielectric layer 200 and the metal reflection layer 300 are all located on the same vertical line.

[0032] It should be noted that the intermediate dielectric layer 200 is made of polyimide, with a relative dielectric constant of 3.5 and a tangent loss ranging from 0.001 to 0.005.

[0033] It should be noted that the metal structure layer 100 and the metal reflection layer 300 are made of the same material. The material is any one of gold, silver, copper, and aluminum. In this embodiment, the materials of the metal structure layer 100 and the metal reflection layer 300 are both selected as copper, with a thickness of 0.2 μm and a conductivity of 5.8×10 7 S / m. Different material selections will have corresponding effects on the device performance, which is also within the scope of protection required by the present invention.

[0034] The terahertz vortex phase plate of this embodiment is subjected to simulation tests: As Figures 4 to 6 shown, according to the geometric phase (PB phase) principle, for the incident circularly polarized wave, when the rotation angle of the metal structure layer 100 is , the metasurface unit will obtain a phase increment twice the rotation angle, that is . By rotating the overall metasurface unit, in the frequency range of 0.2 THz to 1.5 THz, the metasurface unit exhibits excellent PB phase characteristics. When the circularly polarized wave is incident, the amplitude of the cross-polarized wave remains almost unchanged, and the phase distribution shows a linear relationship with the rotation angle. As Figure 4 shown, where Figure 4 the (a) in it is the amplitude distribution when the double rings rotate simultaneously, Figure 4 and the (b) in it is the phase distribution.

[0035] By effectively regulating the electromagnetic coupling between the two inner rings, it is possible to rotate the inner ring or the outer ring independently and precisely regulate the PB phase at a specific frequency point. Specifically, when the first metal split ring 110 (i.e., the inner ring) remains stationary and the second metal split ring 120 (the outer ring) rotates at intervals of 22.5°, at the frequency point of 0.47 THz, the amplitudes can all remain stable and unchanged, while the phase shows a characteristic of uniform distribution with a double-angle relationship, and this phenomenon is visually demonstrated in Figure 5 , where Figure 5 the (a) in it is the corresponding amplitude distribution, Figure 5 and the (b) in it is the phase distribution. Similarly, when the second metal split ring 120 (the outer ring) is fixed and the first metal split ring 110 (i.e., the inner ring) rotates at intervals of 22.5°, at the frequency point of 1.35 THz, the phase also follows the uniform distribution with a double-angle relationship and the amplitude remains constant, as Figure 6 shown, where Figure 6 the (a) in it is the corresponding amplitude distribution, Figure 6In (b) is the phase distribution. The independent regulation mechanism of this embodiment not only significantly improves the control ability of the phase of a specific frequency point, but also provides a strong guarantee for the flexibility and accuracy of the metasurface structure in multi-band applications, expanding its application potential in related fields As Figures 7 to 8 shown, to generate a vortex beam carrying orbital angular momentum (OAM), the metasurface units 10 need to be arranged according to a certain periodic pattern. The metasurface unit structures at different positions must satisfy the phase distribution condition of the formula , where is the topological charge number for generating OAM, is the given spatial coordinate. By separately rotating and arranging the inner ring and the outer ring, the regulation of different topological charges at two different frequency points can be achieved simultaneously. Specifically, Figure 7 shows the rotating outer ring structure, and a vortex beam with a topological charge of 3 is successfully formed at the 0.47 THz frequency band, where Figure 7 in (a) is the amplitude distribution diagram, Figure 7 in (b) is the phase distribution diagram. According to Figure 7 , it can be seen that the amplitude and phase distribution effects of rotating this outer ring structure are significant, while Figure 8 presents the rotating inner ring structure, and a vortex beam with a topological charge of -1 is generated at the 1.35 THz frequency band. Its amplitude is almost zero at the center, forming a typical doughnut-shaped beam pattern, where Figure 8 in (a) is the amplitude distribution diagram, Figure 8 in (b) is the phase distribution diagram. In this embodiment, the terahertz vortex phase plate based on the dual-band misaligned metasurface is composed of 30×30 metasurface units, and the size is 3300μm×3300μm. Therefore, the terahertz vortex phase plate based on the dual-band misaligned metasurface of the present invention can generate vortex beams with different topological charge numbers at different frequency points by separately controlling the rotation angles of the two metal split rings. In addition, it should be noted that according to the above formula, by changing the array arrangement method, vortex beams with topological charge numbers of 1, 2, 3 or -1, -2, -3 can be generated, which are also within the protection scope of this application.

[0036] Embodiment 2 As Figure 9 shown, based on the above embodiment, in this embodiment, by simultaneously rotating the inner ring and the outer ring, the channel beams at two frequency points can be independently regulated simultaneously. Specifically, the size of the metasurface unit array is 30×30. When the inner ring arrangement of the metasurface unit is all 0, that is, when the phase responses of all inner rings are the same, a single beam is formed at 1.37 THz, as shown in Figure 9 in (a); and when the outer ring arrangement of the metasurface unit is 0 / 1, a double beam is formed at 0.48 THz, as shown inFigure 9 As shown in (b) of []. This result fully demonstrates the independent phase regulation ability of the dual-band misaligned metasurface at two different frequency points. This method is expected to be applied to 6G multi-band compatible communication. By utilizing the electromagnetic coupling between the two metal split rings to achieve the separate rotation of the two metal split rings to control the phase at two different frequency bands.

[0037] Example 3 As Figure 10 shown, on the basis of the above example, this example analyzes the influence of different materials of the metal structure layer on the performance. When the materials of the two split rings of the metal layer are metals such as gold, silver, copper, and aluminum, the amplitude of polarization conversion remains almost unchanged, and different materials have little influence on its performance. The main source of influence on performance is that the structure design is different from the thickness of the dielectric layer.

[0038] Example 4 As Figures 11 to 13 shown, this example verifies that the change in the radius of the ring of the metal structure layer and the thickness of the dielectric layer have a certain influence on the overall performance. As Figure 11 shown, when the thickness of the dielectric layer increases from 75 μm to 125 μm, the second peak near 0.3 THz gradually weakens, and the peak value near 1.3 THz gradually increases and moves towards the low frequency. Considering comprehensively, when the thickness of the dielectric layer is 100 μm, the amplitude values at 0.47 THz and 1.37 THz are greater than 0.8. When the inner diameter of the first metal split ring increases from 16 μm to 20 μm, as Figure 12 shown in (a) of [], the amplitude change is almost negligible throughout the frequency band, and the influence of the radius of the first metal split ring on it is relatively weak. When the outer diameter increases from 21 μm to 25 μm, as Figure 12 shown in (b) of [], the distance between the two rings decreases, the coupling increases, the peak and valley rise, but the amplitude at 1.37 THz remains unchanged. When the inner diameter of the second metal split ring increases from 41 μm to 45 μm, as Figure 13 shown in (a) of [], the amplitude change is almost negligible throughout the frequency band, and only a weak change in amplitude occurs near 0.3 THz. When the outer diameter increases from 46 μm to 50 μm, as Figure 13 shown in (b) of [], the amplitude values at 0.47 THz and 1.37 THz almost remain unchanged, and only the amplitude at 1.1 THz decreases. The main reason for the formation is the splitting caused by the strong coupling of the double rings.

[0039] The terahertz vortex phase plate based on a dual-band misaligned metasurface according to the present invention is formed by periodically arranging metasurface units in the same plane. Utilizing the modulation ability of metasurface devices for terahertz waves, by respectively rotating metal split rings, the generation of vortex beams can be achieved within two different terahertz frequency ranges. While generating terahertz vortex beams with larger topological charge numbers (l≥3), it also lays a foundation for the subsequent research on the application of terahertz vortex beams.

[0040] Compared with the prior art, the terahertz vortex phase plate based on a dual-band misaligned metasurface provided by the present invention has the following advantages: (1) Small volume, light weight, and high integration: This phase plate adopts metasurface technology, with a simple, thin, and light structure, facilitating integration into complex optical or communication systems, while reducing manufacturing and usage costs.

[0041] (2) Dual-frequency regulation and strong flexible regulation ability: Without introducing phase change materials, through the structural design of dual-ring misalignment, this phase plate can independently regulate terahertz waves in two different frequency bands, meeting the generation requirements of multi-modal vortex beams and improving the spectral utilization rate.

[0042] (3) Potential for multi-scenario applications: This phase plate is not only applicable to the communication field but also can be used in scenarios such as radar, high-resolution imaging, and energy transmission, demonstrating broad application potential in the field of electromagnetic regulation.

[0043] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the invention.

[0044] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0045] Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of them. The mention of "embodiments" in this context means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase may not necessarily refer to the same embodiment at various places in the specification, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0046] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A terahertz vortex phase plate based on a dual-band misaligned metasurface, characterized in that The metasurface is composed of a number of periodically arranged metasurface units (10). Each metasurface unit (10) includes a metal structure layer (100), an intermediate dielectric layer (200), and a metal reflection layer (300) from top to bottom in sequence. Among them, the metal structure layer (100) includes: Two concentrically arranged metal split rings. By respectively controlling the rotation angles of the two metal split rings, vortex beams with different topological charge numbers at different frequency points are generated. By regulating the electromagnetic coupling between the two metal split rings, the phase at different frequency bands can be controlled based on the single rotation of each metal split ring.

2. The terahertz vortex phase plate based on the dual-band misaligned metasurface according to claim 1, wherein The metal split ring includes: A first metal split ring (110) disposed on the intermediate dielectric layer (200); A second metal split ring (120) disposed outside the first metal split ring (110) and having the same center as the first metal split ring (110).

3. The terahertz vortex phase plate based on a dual-band misaligned metasurface according to claim 1, wherein: By respectively controlling the rotation angles of the two metal split rings to generate vortex beams with different topological charge numbers at different frequency points, specifically: When rotating the first metal split ring (110), a vortex beam with a topological charge of -1 is generated in the 1.35 THz frequency band; When rotating the second metal split ring (120), a vortex beam with a topological charge of 3 is generated in the 0.47 THz frequency band.

4. The terahertz vortex phase plate based on the dual-band misaligned metasurface according to claim 3, characterized in that The opening angle range of the first metal split ring (110) is 30° to 60°, the outer diameter is 21 μm to 25 μm, and the inner diameter is 16 μm to 20 μm.

5. The terahertz vortex phase plate based on the dual-band misaligned metasurface according to claim 3, wherein The opening angle range of the second metal split ring (120) is 30° to 60°, the outer diameter is 46 μm to 50 μm, and the inner diameter is 41 μm to 45 μm.

6. The terahertz vortex phase plate based on the dual-band misaligned metasurface according to claim 1, wherein The arrangement period of the metasurface unit (10) is p = 110 μm to 120 μm, where The thicknesses of both the metal structure layer (100) and the metal reflection layer (300) are not less than 0.2 μm; The thickness range of the intermediate dielectric layer (200) is 75 μm to 125 μm.

7. The terahertz vortex phase plate based on a dual-band misaligned metasurface according to claim 1, characterized in that In each metasurface unit (10), the centers of the two metal split rings, the geometric center of the intermediate dielectric layer (200), and the geometric center of the metal reflection layer (300) are all located on the same vertical line.

8. The terahertz vortex phase plate based on a dual-band misaligned metasurface according to claim 7, wherein The intermediate dielectric layer (200) is polyimide, with a relative dielectric constant of 3.5 and a tangent loss range of 0.001 to 0.

005.

9. The terahertz vortex phase plate based on a dual-band misaligned metasurface according to claim 1, wherein The metal structure layer (100) and the metal reflection layer (300) are made of the same material.

10. The terahertz vortex phase plate based on the dual-band misaligned metasurface according to claim 9, wherein The material is any one of gold, silver, copper, and aluminum.

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