A reflective multifunctional multiplexed polarization conversion metasurface

Abstract

This invention belongs to the field of electromagnetic metamaterials technology, specifically relating to a reflective, multifunctional multiplexed polarization conversion metasurface. It comprises multiple square polarization conversion units, which, from top to bottom, include a metal patch layer, a dielectric layer, and a bottom metal substrate layer. The metal patch layer consists of square metal patches with small square grooves cut out at their upper left and lower right corners, and a circular groove at the center. The center of the circular groove has a cross-shaped structure formed by two rectangles joined together. This invention provides a new solution for multifunctional polarization conversion technology, with broad application prospects, suitable for fields such as electronic countermeasures, satellite communication, and wireless communication.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic metasurface technology, specifically relating to a reflective multifunctional multiplexed polarization conversion metasurface. Background Technology

[0002] Polarization is a fundamental characteristic of electromagnetic waves, describing the change of electric field direction over time. With the increasing importance of polarization-sensitive devices in optics, research on electromagnetic wave polarization control has become a hot topic. Traditional polarization manipulation techniques typically rely on complex structures, such as birefringent liquid crystals or crystalline materials. However, these methods often result in large and thick devices, making integration into compact systems difficult and limiting further improvements in conversion efficiency. Metamaterials and metasurfaces, as artificially designed ultrathin structures, exhibit unparalleled advantages over natural materials due to their unique electromagnetic properties and optical responses. In practical applications, besides selecting specific polarized light, altering the polarization state is also crucial. For example, in satellite communication and navigation systems, linearly polarized waves are susceptible to unpredictable rotational interference during propagation, leading to receiver polarization mismatch and affecting system link budget. Circularly polarized waves, on the other hand, are less sensitive to multipath fading and less affected by Faraday rotation and changes in the receiving antenna direction, thus offering significant advantages. This characteristic has driven the development of linear-to-circular polarization switching technology.

[0003] Despite significant progress in polarization converters in recent years, existing technologies still face numerous challenges and functional limitations. For example, most polarization converters are single-function, capable only of converting linear polarization to linear or linear polarization to circular polarization, while research integrating multiple polarization conversion functions into a single device is relatively rare. Furthermore, there is still considerable room for improvement in the operating bandwidth and conversion efficiency of existing devices. Summary of the Invention

[0004] To address the problems of existing polarization conversion metasurfaces, such as complex structures, limited functionality, and narrow operating frequency bands, which make them difficult to meet practical application requirements, this invention provides a reflective, multifunctional, multiplexed polarization conversion metasurface, the specific solution of which is as follows:

[0005] A reflective, multifunctional, multiplexed polarization conversion metasurface is composed of several polarization conversion units, each polarization conversion unit being square. Each polarization conversion unit includes a dielectric layer, and a top metal patch and a bottom metal substrate respectively disposed on both sides of the dielectric layer. The top metal patch is a square metal patch with small square grooves cut out at two opposite corners and a circular groove in the center. A cross-shaped patch is disposed in the circular groove, opposite to the small square groove.

[0006] Furthermore, the incident linearly polarized wave is converted into a linearly polarized wave or a circularly polarized wave orthogonal to it in different frequency bands; the incident circularly polarized wave is converted into a circularly polarized wave or a linearly polarized wave with the opposite rotation direction in different frequency bands.

[0007] Furthermore, the arms of the cross-shaped patch are of equal length, and two of the arms are on the same straight line as the small square groove; the top metal patch has a centrally symmetrical structure.

[0008] Furthermore, the period p of the polarization conversion unit is equal to the length of the dielectric layer and the underlying metal substrate.

[0009] Furthermore, the top metal patch and the small square groove are both square; the side length of the top metal patch is a; the side length of the cut-out small square groove is b; the radius r of the circular groove is ; the lengths of the cross-shaped patch in both directions are equal, both being l; the width of the cross-shaped patch is w; and the thickness of the top metal patch, the cross-shaped patch, and the bottom metal substrate is t.

[0010] Furthermore, l is less than 2r; a > 2b > a - 2r.

[0011] Furthermore, the side length a of the top metal patch is 60 μm; the side length b of the cut-out small square groove is 16 μm; the radius r of the circular groove is 21 μm; the length l of the cross-shaped patch in both directions is equal, both being 25 μm, and the width w of the cross-shaped patch is 15 μm; the thickness t of the top metal patch, the cross-shaped patch, and the bottom metal substrate is 0.2 μm.

[0012] Furthermore, the dielectric layer is square, with a thickness of h and a length of p.

[0013] Furthermore, the thickness h of the dielectric layer is 15 μm and the length p is 70 μm.

[0014] Furthermore, the dielectric layer material is polytetrafluoroethylene; the bottom metal substrate material is gold; and the top metal patch and cross-shaped patch material are gold.

[0015] By adopting the above scheme, the method of the present invention has the following advantages:

[0016] 1. This invention cleverly combines a metal patch, a dielectric layer, and a metal substrate layer. Through a simple structural design, it achieves multiple polarization conversion functions, including linear-to-linear polarization, linear-to-circular polarization, circular-to-linear polarization, and circular-to-circular polarization. It also features wide bandwidth, high conversion efficiency, multifunctionality, and frequency division multiplexing.

[0017] 2. In the range of 1.13-1.97 THz, the metasurface of this invention can convert incident linearly polarized waves into orthogonal linearly polarized waves, and can convert circularly polarized waves into circularly polarized waves with opposite rotation. In the range of 2.03-2.97 THz, the metasurface can provide polarization conversion from linear to circular polarization with an axial ratio of less than 3 dB, and polarization conversion from circular to linear polarization with an axial ratio of more than 20 dB.

[0018] 3. This invention possesses multi-functional multiplexing capabilities and wide-band polarization conversion characteristics, enabling it to meet the diverse needs of modern communication and sensor technologies for electromagnetic wave polarization control. It has broad application prospects in fields such as electronic warfare, satellite communication, and wireless communication, providing a new approach to achieving efficient manipulation of electromagnetic waves. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the polarization conversion unit of the reflective multifunctional multiplexed polarization conversion metasurface of the present invention.

[0020] Figure 2 This is a schematic diagram of the polarization states of the incident and emitted waves of the metasurface of the present invention.

[0021] Figure 3 These are the reflection coefficients (a) of the metasurface of the present invention under polarized incident light, and the phase difference (b) between cross-polarization and co-polarization.

[0022] Figure 4 The diagram shows the polarization conversion efficiency of the metasurface of this invention under polarized wave incident polarization transition from linear polarization to linear polarization and from linear polarization to circular polarization.

[0023] Figure 5 This is the axial ratio diagram of the emitted circularly polarized wave when the metasurface online polarized wave of the present invention is converted into a circularly polarized wave.

[0024] Figure 6 These are the reflection coefficients (a) of the metasurface of the present invention under circularly polarized incident light, and the phase difference (b) between cross-polarization and co-polarization.

[0025] Figure 7 The diagram shows the polarization conversion efficiency of the metasurface of the present invention under incident circularly polarized wave, specifically the polarization conversion efficiency from circular polarization to linear polarization.

[0026] Figure 8 This is the axial ratio diagram of the emitted linearly polarized wave when the circularly polarized wave of the metasurface of the present invention is converted into a linearly polarized wave. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example:

[0029] like Figure 1 As shown, the reflective multifunctional multiplexed polarization conversion metasurface of the present invention is composed of several polarization conversion units spliced ​​together. The polarization conversion unit is square. The polarization conversion unit includes a dielectric layer, and a top metal patch and a bottom metal substrate respectively disposed on both sides of the dielectric layer. The top metal patch is a square metal patch, with small square grooves cut out at two opposite corners and a circular groove in the center. A cross-shaped patch opposite to the small square groove is disposed in the circular groove.

[0030] The arms of the cross-shaped patch are of equal length, and two of the arms are in a straight line with the small square groove; the top metal patch layer has a centrally symmetrical structure.

[0031] The top metal patch and the small square groove are both square; the side length of the top metal patch is *a*; the side length of the cut-out small square groove is *b*; the radius *r* of the circular groove is *r*; the lengths of the cross-shaped patch in both directions are equal, both being *l*; the width of the cross-shaped patch is *w*; the thickness of the top metal patch and the cross-shaped patch is *t*. The dielectric layer is square, and its thickness is *h*, and its length is *p*.

[0032] Preferably, l is less than 2r, and the cross-shaped patch does not connect with the edge of the circular groove; since the top metal patch and the small square groove are both square, a>2b>a-2r, and the top metal patch is divided into two non-connected parts by the small square groove.

[0033] Furthermore, the side length a of the top metal patch is 60 μm; the side length b of the cut-out small square groove is 16 μm; the radius r of the circular groove is 21 μm; the length l of the cross-shaped patch in both directions is equal, both being 25 μm, and the width w of the cross-shaped patch is 15 μm; the thickness t of the top metal patch, the cross-shaped patch, and the bottom metal substrate is 0.2 μm.

[0034] Preferably, the thickness h of the dielectric layer is 15 μm, and the length p of the dielectric layer is 70 μm.

[0035] The dielectric layer is made of polytetrafluoroethylene (PTFE) with a dielectric constant of 2.34 and a thickness of 15 μm. Both the top metal patch and the bottom metal substrate are made of gold, with a conductivity of 4.56 × 10^7 S / m and a thickness of 0.2 μm. The unit cell has a period of 70 μm. The overall design achieves a tight integration of function and structure, providing an efficient and wide-bandwidth solution for polarization conversion.

[0036] Example Sample Testing:

[0037] like Figure 2 As shown, this invention demonstrates the polarization states of incident and emitted waves under different electromagnetic wave incidence conditions. It can be seen that when a linearly polarized wave is incident at 1.69 THz, the emitted wave remains linearly polarized, and the incident and emitted waves are symmetrical about y = x. However, at 2.24 THz, the emitted wave is elliptically polarized, and the incident x-polarized and y-polarized waves are converted into left-handed and right-handed circularly polarized waves, respectively. For circularly polarized wave incidence, the left-handed and right-handed circularly polarized waves interconvert at 1.69 THz, while at 2.24 THz they transform into linearly polarized waves.

[0038] like Figure 3 Figure a shows the reflection coefficient diagram of the present invention when the incident wave is linearly polarized. It can be seen that in the range of 1.13-1.97 THz, the reflection coefficient of the cross-polarized wave is larger, while that of the common-polarized wave is smaller. This indicates that the incident electromagnetic wave is effectively converted into an electromagnetic wave in its orthogonal direction. In the range of 2.03-2.97 THz, the amplitudes of the emitted common-polarized wave and the cross-polarized wave are approximately the same.

[0039] like Figure 3 As shown in Figure b, this invention presents a phase difference diagram when the incident wave is linearly polarized. Regardless of whether an x-polarized wave or a y-polarized wave is incident, the phase difference between the outgoing cross-polarized wave and the common-polarized wave is ±π / 2.

[0040] like Figure 4 The diagram illustrates the polarization conversion efficiency of the metasurface. It can be seen that, in the frequency range of 1.13–1.97 THz, the linear-to-linear polarization conversion efficiency is above 0.7 across the entire band, indicating that the metasurface exhibits good conversion performance within this frequency range. Meanwhile, in the frequency range of 2.03–2.97 THz, the linear-to-circular polarization conversion efficiency is very high.

[0041] like Figure 5 The figure shows the axial ratio of the emitted polarized wave when a linearly polarized wave is incident on the metasurface. Generally, polarized waves with an axial ratio below 3 dB can be considered circularly polarized waves. It can be seen that in the range of 2.03–2.97 THz, the axial ratio of the emitted polarized wave is below 3 dB, indicating that the metasurface can effectively convert incident linearly polarized waves into circularly polarized waves in this frequency band.

[0042] like Figure 6 Figure a shows the reflection coefficient diagram of the present invention when the incident wave is a circularly polarized wave. It can be seen that in the range of 1.13-1.97 THz, the reflection coefficient of the cross-polarized wave is larger, while the reflection coefficient of the common-polarized wave is smaller, indicating that the incident circularly polarized wave is converted into a circularly polarized wave with the opposite rotation direction. In the range of 2.03-2.97 THz, the amplitudes of the emitted common-polarized wave and the cross-polarized wave are close.

[0043] like Figure 6 As shown in Figure b, this invention presents a phase difference diagram when the incident wave is a circularly polarized wave. Regardless of whether a left-handed or right-handed circularly polarized wave is incident, the phase difference between the outgoing cross-polarized wave and the common-polarized wave is ±π.

[0044] like Figure 7 The diagram illustrates the polarization conversion efficiency of the metasurface. It can be seen that, in the frequency range of 1.13–1.97 THz, the polarization conversion efficiency from circular to linear polarization is above 0.7 across the entire band, indicating that the metasurface exhibits good circular polarization conversion performance in this frequency range. Furthermore, the conversion efficiency from circular to linear polarization is also very high in the frequency range of 2.03–2.97 THz.

[0045] like Figure 8 The figure shows the axial ratio of the emitted polarized wave when a circularly polarized wave is incident on the metasurface. Generally, polarized waves with an axial ratio higher than 20 dB can be considered linearly polarized waves. It can be seen that in the range of 2.16–2.93 THz, the axial ratio of the emitted polarized wave is higher than 20 dB, indicating that the metasurface can efficiently convert incident circularly polarized waves into linearly polarized waves in this frequency band.

[0046] In summary, the reflective multifunctional multiplexed polarization conversion metasurface of this invention achieves multifunctionality through a simple structural design by cleverly combining a metal patch, a dielectric layer, and a metal substrate. This metasurface can not only change the polarization direction of incident electromagnetic waves but also effectively adjust their polarization state. Specifically, the metasurface can convert incident linearly polarized waves into orthogonal linearly polarized waves in the 1.13-1.97 THz frequency band, and convert incident electromagnetic waves into circularly polarized waves in the 2.03-2.97 THz frequency band. Furthermore, for circularly polarized waves, the metasurface can convert them into circularly polarized waves with the opposite rotation direction in the 1.13-1.97 THz frequency band, and achieve the conversion from circularly polarized waves to linearly polarized waves in the 2.16-2.93 THz frequency band. These conversion effects across different frequency bands highlight the multifunctionality and multiplexing capability of this metasurface, providing new technical solutions for fields such as electronic warfare, wireless communication, and satellite communication, especially demonstrating great potential in the control of polarized wave transmission.

[0047] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this invention.

Claims

1. A reflective, multifunctional, multiplexed polarization conversion metasurface, composed of several polarization conversion units, characterized in that, The polarization conversion unit is square; the polarization conversion unit includes a dielectric layer, and a top metal patch and a bottom metal substrate respectively disposed on both sides of the dielectric layer; the top metal patch is a square metal patch, with small square grooves cut out at two opposite corners and a circular groove in the center; a cross-shaped patch opposite to the small square groove is disposed in the circular groove.

2. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 1, characterized in that, The incident linearly polarized wave is converted into a linearly polarized wave or a circularly polarized wave orthogonal to it in different frequency bands; the incident circularly polarized wave is converted into a circularly polarized wave or a linearly polarized wave with the opposite rotation direction in different frequency bands.

3. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 1, characterized in that, The cross-shaped patch has arms of equal length, and two of the arms are in line with the small square groove; the top metal patch has a centrally symmetrical structure.

4. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 1, characterized in that, The period p of the polarization conversion unit is equal to the length of the dielectric layer and the underlying metal substrate.

5. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 1, characterized in that, The top metal patch and the small square groove are both square; the side length of the top metal patch is a; the side length of the cut-out small square groove is b; the radius of the circular groove is r; the lengths of the cross-shaped patch in both directions are equal, both being l; the width of the cross-shaped patch is w; the thickness of the top metal patch, the cross-shaped patch, and the bottom metal substrate is t.

6. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 5, characterized in that, The value of l is less than 2r; a > 2b > a - 2r.

7. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 5, characterized in that, The side length a of the top metal patch is 60 μm; the side length b of the cut-out small square groove is 16 μm; the radius r of the circular groove is 21 μm; the length l of the cross-shaped patch in both directions is equal, both being 25 μm, and the width w of the cross-shaped patch is 15 μm; the thickness t of the top metal patch, the cross-shaped patch, and the bottom metal substrate is 0.2 μm.

8. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 1, characterized in that, The dielectric layer is square, with a thickness of h and a length of p.

9. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 8 or 4, characterized in that, The thickness h of the dielectric layer is 15 μm and the length p is 70 μm.

10. The reflective multifunctional multiplexed polarization conversion metasurface according to claim 1, characterized in that, The dielectric layer material is polytetrafluoroethylene; the bottom metal substrate material is gold; and the top metal patch and cross-shaped patch material are gold.

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