Multi-beam-splitting metasurface beam splitter and application thereof

Abstract

The invention provides a multi-beam-splitting metasurface beam splitter and application thereof, the beam splitter comprises a plurality of array units arranged in a plurality of rows and columns, each array unit comprises 16 metasurface unit structures arranged in a 4 * 4 square array, each metasurface unit structure comprises a bottom-layer metal plate, a middle dielectric layer and a top-layer metal pattern which are sequentially stacked from bottom to top, and the top-layer patterns of the four metasurface unit structures in any row / column cover the 0-degree phase, the 45-degree phase, the 90-degree phase and the 135-degree phase of the reference pattern; the reference pattern has C2 symmetry about the Z axis and comprises a first extending part, a linear main body part and a second extending part which are connected in sequence, and the first extending part extends from the two ends of the linear main body part in the-X direction and the X direction respectively. The beam splitter provided by the invention can realize smaller structural volume, is easy to process and integrate, is flexible in design method, can realize high beam splitting uniformity, multi-beam splitting and variable propagation direction, and can realize larger bandwidth.

Description

Technical Field

[0001] The invention belongs to the field of optical technology and relates to a multi-beam splitting metasurface beam splitter and applications thereof. Background Art

[0002] With the rapid development of mobile communications and the increasing complexity of the communication environment, antennas need to have wide beam and multi-beam capabilities. Metasurfaces composed of periodic or non-periodic units on a subwavelength scale can achieve control of electromagnetic wave beams by adjusting the amplitude and phase of the incident electromagnetic wave. Terahertz waves have attracted much attention from researchers at home and abroad in many aspects such as high-speed communications, radar and imaging. Among them, the effective control of terahertz wave beam splitting is one of the research hotspots in terahertz science and technology. Traditionally, terahertz waves are mainly controlled by the phase accumulation method, but this method is relatively complicated to operate. In recent years, a large number of scholars have used metamaterials to construct optical devices, making the control of terahertz waves simpler and more efficient. Generally, traditional electromagnetic materials are mainly studied from the perspective of atomic or molecular composition, and their electromagnetic properties are characterized by intrinsic parameters such as dielectric constant and magnetic permeability. However, by artificially designing the periodic unit structure of metamaterials, extraordinary electromagnetic properties that have not yet been found to be difficult to achieve with traditional electromagnetic materials can be achieved. Metamaterials are artificial structures composed of subwavelength-sized units arranged and combined in a periodic or non-periodic manner. Its electromagnetic properties are determined not only by the properties of the material itself, but also by its unit structure. Therefore, electromagnetic parameters or electromagnetic properties that do not exist in nature can be achieved by designing different metamaterial unit structures. In the design, it is usually required that the size of the metamaterial unit structure is much smaller than the wavelength of the incident wave, and the metamaterial can be regarded as a uniform medium. The electromagnetic parameters derived using the uniform method can be used to guide the design of artificial metamaterial structures.

[0003] The metasurface-based beam splitter introduces a suitable phase gradient at the interface to obtain reflected beams at different angles, that is, the beam deflection can be achieved through the generalized reflection law. Traditional beam splitters are composed of a variety of anisotropic materials, and have disadvantages such as large size, narrow working bandwidth, and low efficiency. In addition, traditional beam splitters mainly use the phase accumulation method to control terahertz waves, but the operation of the control method is relatively complicated. Furthermore, the current metamaterial beam splitters at home and abroad are not enough to change the wave number and direction of the outgoing wave, which limits the application of beam splitters, and there are relatively few beam splitters with multiple beams.

[0004] Therefore, how to provide a high-performance metasurface beam splitter with simple structure, small size, low cost and easy processing has become an important technical problem that needs to be urgently solved by technical personnel in this field.

[0005] It should be noted that the above introduction of the technical background is only for the convenience of clearly and completely explaining the technical solution of the present application and facilitating the understanding of those skilled in the art. It cannot be considered that the above technical solutions are well-known to those skilled in the art merely because these solutions are described in the background art part of the present application. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a multi-beam splitter metasurface and its application, which is used to solve the problems that the existing beam splitters are composed of a combination of various anisotropic materials and have many disadvantages such as large volume, narrow operating bandwidth, and low efficiency.

[0007] To achieve the above object and other related objects, the present invention provides a multi-beam splitter metasurface, which includes a plurality of array units arranged in multiple rows and multiple columns. The array units include 16 metasurface unit structures arranged in a 4×4 square array. The metasurface unit structure includes a bottom metal plate, an intermediate dielectric layer, and a top metal pattern stacked in sequence from bottom to top. Among them, the top patterns of the four metasurface unit structures arranged in the X direction in any row cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. The top patterns of the four metasurface unit structures arranged in the Y direction in any column cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. The reference pattern has C2 symmetry about the Z axis and includes a first extension part, a linear main body part, and a second extension part connected in sequence. The first extension part extends from one end of the linear main body part in the -X direction, and the second extension part extends from the other end of the linear main body part in the X direction, where the X direction is perpendicular to the Y direction, and the Z axis is perpendicular to the X-Y plane.

[0008] Optionally, the phase difference between the top patterns of any two adjacent metasurface unit structures is 45°.

[0009] Optionally, the linear main body part extends in the Y direction.

[0010] Optionally, the included angle between the linear main body part and the first extension part is an acute angle, and the included angle between the linear main body part and the second extension part is an acute angle.

[0011] Optionally, the material of the bottom metal plate includes one or more of Au and Cu, and the material of the top metal pattern includes one or more of Au and Cu.

[0012] Optionally, the material of the intermediate dielectric layer includes polyimide.

[0013] The present invention also provides an application of a multi-beam split metasurface beam splitter, and the application includes splitting a linearly polarized wave by using the multi-beam split metasurface beam splitter described in any one of the above.

[0014] Optionally, the application includes terahertz stealth and / or terahertz imaging.

[0015] Optionally, when an electromagnetic wave is vertically incident on the metasurface of the multi-beam split metasurface beam splitter, the incident wave is reflected by the metasurface into four waves with different propagation directions.

[0016] Optionally, in the working bandwidth of 0.20 THz - 0.34 THz, the reflection angle range of the reflected wave is 20.4° - 36.7°.

[0017] As described above, the multi-beam split metasurface beam splitter of the present invention includes a plurality of array units arranged in multiple rows and multiple columns. Each array unit includes 16 metasurface unit structures arranged in a 4×4 square array. The metasurface unit structure includes a bottom metal plate, an intermediate dielectric layer, and a top metal pattern stacked in sequence from bottom to top. Among them, the top patterns of the four metasurface unit structures arranged in the X direction in any row cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern, and the top patterns of the four metasurface unit structures arranged in the Y direction in any column cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. The reference pattern has C2 symmetry about the Z axis and includes a first extension part, a linear main body part, and a second extension part connected in sequence. The first extension part extends in the -X direction from one end of the linear main body part, and the second extension part extends in the X direction from the other end of the main body part. The design method of the multi-beam split metasurface beam splitter of the present invention is flexible, and it can achieve high beam splitting uniformity, splitting of multiple beams with variable propagation directions, and can achieve a relatively large bandwidth. In addition, the multi-beam split metasurface beam splitter of the present invention can achieve a smaller structural volume and is easy to process and integrate. Description of the Drawings

[0018] Figure 1 It shows a plan layout diagram of the multi-beam split metasurface beam splitter of the present invention in an embodiment.

[0019] Figure 2 It shows a plan layout diagram of an array unit of the multi-beam split metasurface beam splitter of the present invention in an embodiment.

[0020] Figure 3 It shows a three-dimensional structural schematic diagram of a metasurface unit structure of the multi-beam split metasurface beam splitter of the present invention in an embodiment.

[0021] Figure 4 It shows a schematic diagram of beam separation by a reflective beam splitter constructed by the present invention.

[0022] Figure 5 It shows the three-dimensional far-field diagram of the reflected wave with vertical incidence obtained by simulation of the multi-beam splitter based on the metasurface of the present invention in an embodiment.

[0023] Figure 6 It shows the reflectivity curve obtained by simulation of the multi-beam splitter based on the metasurface of the present invention in an embodiment.

[0024] Description of component numbers

[0025] 1 Multi-beam splitter based on the metasurface

[0026] 11 Array unit

[0027] 111 Metasurface unit structure

[0028] 101 Bottom metal plate

[0029] 102 Intermediate dielectric layer

[0030] 103 Top metal pattern

[0031] 1031 First extension

[0032] 1032 Linear main body

[0033] 1033 Second extension Detailed implementation manners

[0034] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] Please refer to Figures 1 to 6 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and ratios of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0036] The present invention provides a multi-beam splitter based on the metasurface. The multi-beam splitter based on the metasurface includes a plurality of array units arranged in multiple rows and multiple columns. For example, please refer to Figure 1, which shows a schematic diagram of the multi-beam splitting metasurface beam splitter 1 including 9 array units 11, and these 9 array units 11 are arranged in 3 rows and 3 columns. It should be noted that in other embodiments, the number of array units included in the multi-beam splitting metasurface beam splitter can be adjusted according to actual needs.

[0037] Specifically, the array unit 11 includes 16 metasurface unit structures 111 arranged in a 4×4 square array. For example, please refer to Figure 2 and Figure 3 , where Figure 2 shows a planar layout diagram of the array unit 11, Figure 3 shows a three-dimensional structure schematic diagram of the metasurface unit structure 111.

[0038] Specifically, the metasurface unit structure 111 includes a bottom metal plate 101, an intermediate dielectric layer 102, and a top metal pattern 103 stacked in sequence from bottom to top. The material of the bottom metal plate 101 can be selected from Au (gold), Cu (copper), or other suitable metal materials. The material of the top metal pattern 103 can be selected from Au (gold), Cu (copper), or other suitable metal materials. The material of the intermediate dielectric layer 102 can be selected from polyimide or other dielectric materials with lower losses.

[0039] Specifically, in the metasurface unit structure 111, the top patterns of the four metasurface unit structures 111 arranged in any row in the X direction cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. The top patterns of the four metasurface unit structures 111 arranged in any column in the Y direction cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. That is to say, in the array unit 11, any horizontal sub-array and any vertical sub-array both satisfy 2π phase coverage, and reflected beams at different angles can be obtained, that is, beam deflection can be achieved through the generalized reflection law.

[0040] As an example, the phase change of the top patterns of the four metasurface unit structures 111 arranged in any row in the X direction is gradient. The phase difference between the top patterns of any two adjacent metasurface unit structures 111 is 45°. For example, in Figure 2 the shown array unit 11, the four metasurface unit structures 111 arranged in any row in the X direction are rotated counterclockwise by 45° in sequence from left to right, and the four metasurface unit structures 111 arranged in any column in the Y direction are rotated clockwise and counterclockwise by 45° in sequence from top to bottom.

[0041] Specifically, the reference pattern has C2 symmetry about the Z axis, where C2 symmetry refers to the property of coinciding with itself after a 180° rotation.

[0042] Specifically, as Figure 3 shown, the reference pattern includes a first extension portion 1031, a linear main body portion 1032, and a second extension portion 1033 that are sequentially connected. The first extension portion 1031 extends in the -X direction from one end of the linear main body portion 1032, and the second extension portion 1033 extends in the X direction from the other end of the linear main body portion 1032. Here, the X direction is perpendicular to the Y direction, and the Z axis is perpendicular to the X-Y plane.

[0043] Specifically, in Figure 3 the metasurface unit structure 111 shown, the linear main body portion 1032 extends in the Y direction. That is to say, the angle between the linear main body portion 1032 and the first extension portion 1031 is a right angle, and the angle between the linear main body portion 1032 and the second extension portion 1033 is a right angle.

[0044] In other embodiments, the angle between the linear main body portion 1032 and the first extension portion 1031, and the angle between the linear main body portion 1032 and the second extension portion 1033 can also be acute angles. That is to say, the extension direction of the linear main body portion 1032 deviates from the Y direction.

[0045] It should be noted that, compared with the solution where the angle between the linear main body portion 1032 and the first extension portion 1031 / the second extension portion 1033 is an acute angle, the solution where the angle between the linear main body portion 1032 and the first extension portion 1031 / the second extension portion 1033 is a right angle has a better beam splitting effect. When the solution where the angle between the linear main body portion 1032 and the first extension portion 1031 / the second extension portion 1033 is an acute angle is adopted, the specific angle can be adjusted according to actual needs.

[0046] Specifically, in order to achieve high-efficiency beam splitting, as much energy as possible needs to be reflected, that is, the transmittance of the incident electromagnetic wave tends to zero and the reflectance is as large as possible. In practical applications, the specific thickness and size of the metasurface unit structure 111 can be determined through simulation results. For example, the lengths and widths of the linear main body portion 1032 and the first extension portion 1031 / the second extension portion 1033 can be obtained by simulating different length and width structure parameters and selecting the one with the best reflectance effect.

[0047] Specifically, the multi-beam splitter metasurface of the present invention can be applied to split linearly polarized waves. Among them, a linearly polarized wave can be regarded as circularly polarized beams with opposite circular polarizations propagating in the same direction. To eliminate the influence of non-converted beams, an off-axis configuration is adopted. Generally, a linear polarization topology can be generated by the coherent superposition of two planes. The key point here is to generate a phase profile, which can simultaneously generate a pair of off-axis beams with centrosymmetric distribution under circularly polarized light illumination. At the same time, the latest progress of the reflective plasma surface is utilized, and a dielectric layer is sandwiched between a metal structure layer and a grounded metal layer.

[0048] As an example, please refer to Figure 4 , which shows a schematic diagram of beam separation by a reflective beam splitter constructed according to the present invention.

[0049] In simulation, to simulate an infinite gradient array, periodic boundary conditions need to be set in the X-Y plane, and a free space environment needs to be set in the direction opposite to the Z-axis. As an example, please refer to Figure 5 , which shows a three-dimensional far-field diagram of the reflected wave of a vertically incident multi-beam splitter metasurface of the present invention obtained by simulation in an embodiment. The simulation results show that when an electromagnetic wave is vertically incident on the metasurface of the multi-beam splitter metasurface, the incident wave will be reflected into four waves with approximately equal energy but different propagation directions.

[0050] As an example, please refer to Figure 6 , which shows the reflectivity curve obtained by simulation of the multi-beam splitter metasurface of the present invention in an embodiment. It is found that compared with a strip type (without the first extension part 1031 and the second extension part 1033) and an "I"-type structure beam splitter (similar to an "I" shape), the beam splitter of the present invention using a "Z"-type top metal pattern can realize the reflection and beam splitting of terahertz waves in a larger working bandwidth. At the same time, compared with the beam splitter using a strip type top metal pattern, the beam splitter of the present invention using a "Z"-type top metal pattern has a higher reflectivity while increasing the bandwidth.

[0051] In an embodiment, for the beam splitter of the present invention using a "Z"-type top metal pattern, in the working bandwidth of 0.20 THz - 0.34 THz, the reflection angle range of the reflected wave is 20.4° - 36.7°, realizing a beam splitter with adjustable reflection angle designed by the geometric metasurface theory.

[0052] The multi-beam splitter metasurface of the present invention has multi-beam splitting performance and the ability to adjust the outgoing wave, and has many advantages such as simple structure, thin thickness, convenient implementation, ingenious and flexible design, etc. It can provide a higher reflectivity while increasing the working bandwidth, is suitable for large-scale popularization and application, and has great application prospects in terahertz stealth and terahertz imaging, etc.

[0053] In summary, the multi-beam splitting metasurface beam splitter of the present invention includes a plurality of array units arranged in multiple rows and columns. Each array unit includes 16 metasurface unit structures arranged in a 4×4 square array. The metasurface unit structure includes a bottom metal plate, an intermediate dielectric layer, and a top metal pattern stacked in sequence from bottom to top. Among them, the top patterns of the four metasurface unit structures arranged in the X direction in any row cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. The top patterns of the four metasurface unit structures arranged in the Y direction in any column cover the 0° phase, 45° phase, 90° phase, and 135° phases of the reference pattern. The reference pattern has C2 symmetry about the Z axis and includes a first extension portion, a linear main body portion, and a second extension portion connected in sequence. The first extension portion extends from one end of the linear main body portion in the -X direction, and the second extension portion extends from the other end of the main body portion in the X direction. The design method of the multi-beam splitting metasurface beam splitter of the present invention is flexible, can achieve high beam splitting uniformity, splitting of multiple beams with variable propagation directions, and can achieve a large bandwidth. In addition, the multi-beam splitting metasurface beam splitter of the present invention can achieve a small structural volume and is easy to process and integrate. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0054] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A multi-beam splitting metasurface beam splitter, characterized in that: The multi-beam splitter metasurface beam splitter includes a plurality of array units arranged in multiple rows and columns. The array units include 16 metasurface unit structures arranged in a 4×4 square array. The metasurface unit structure includes a bottom metal plate, an intermediate dielectric layer, and a top metal pattern stacked in sequence from bottom to top. Among them, the top patterns of the four metasurface unit structures arranged in the X direction in any row cover the 0° phase, 45° phase, 90° phase, and 135° phase of the reference pattern. The top patterns of the four metasurface unit structures arranged in the Y direction in any column cover the 0° phase, 45° phase, 90° phase, and 135° phase of the reference pattern. The reference pattern has C2 symmetry about the Z axis and includes a first extension, a linear main body, and a second extension connected in sequence. The first extension extends in the -X direction from one end of the linear main body, and the second extension extends in the X direction from the other end of the linear main body. Among them, the X direction is perpendicular to the Y direction, and the Z axis is perpendicular to the X-Y plane.

2. The multi-beam splitter metasurface beam splitter according to claim 1, characterized in that: The phase difference between the top patterns of any two adjacent metasurface unit structures is 45°.

3. The multi-beam splitter metasurface beam splitter according to claim 1, characterized in that: The linear main body extends in the Y direction.

4. The multi-beam splitter metasurface beam splitter according to claim 1, wherein: The angle between the linear main body and the first extension is an acute angle, and the angle between the linear main body and the second extension is an acute angle.

5. The multi-beam splitter metasurface beam splitter according to claim 1, characterized in that: The material of the bottom metal plate includes one or more of Au and Cu, and the material of the top metal pattern includes one or more of Au and Cu.

6. The multi-beam splitter metasurface beam splitter according to claim 1, wherein: The material of the intermediate dielectric layer includes polyimide.

7. Application of a multi-beam splitting metasurface beam splitter, characterized in that: The application includes splitting a linearly polarized wave using the multi-beam splitter metasurface beam splitter according to any one of claims 1-6.

8. The application of the multi-beam splitter metasurface beam splitter according to claim 7, wherein: The application includes terahertz stealth and / or terahertz imaging.

9. The application of the multi-beam splitting metasurface beam splitter according to claim 7, characterized in that: When an electromagnetic wave is vertically incident on the metasurface of the multi-beam splitter metasurface beam splitter, the incident wave is reflected by the metasurface into four waves with different propagation directions.

10. The application of the multi-beam splitting metasurface beam splitter according to claim 7, characterized in that: In the working bandwidth of 0.20 THz - 0.34 THz, the reflection angle range of the reflected wave is 20.4° - 36.7°.

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