Terahertz chiral metasurface

Abstract

The invention provides a terahertz chiral metasurface. The terahertz chiral metasurface comprises at least one first chiral structural unit and at least one second chiral structural unit, each of the first chiral structure unit and the second chiral structure unit comprises a substrate material layer, a dielectric layer and a metal pattern layer, and the dielectric layer is arranged between the substrate material layer and the metal pattern layer; the metal pattern layer comprises a first transverse strip, a second transverse strip, a third transverse strip, a first longitudinal strip and a second longitudinal strip, and the first longitudinal strip is arranged on one side of the upper surface of the dielectric layer; the extension directions of a first transverse strip, a second transverse strip and a third transverse strip in the first chiral structure unit and the second chiral structure unit are opposite; one side of the metal pattern layer serves as input and output ports of terahertz waves. The scheme is suitable for the terahertz wave band, and the structure based on the first chiral structure unit and the second chiral structure unit shows two opposite response characteristics to the terahertz wave band, and is suitable for encrypted transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz devices, and in particular to a terahertz chiral super surface. Background Art

[0002] In recent years, information technology and Internet technology have developed rapidly, and information security issues have received increasing attention. The research on encryption technology with attack immunity and decryption complexity has received widespread attention from scholars. The core of information encryption technology is to use algorithms and keys to encode the original information so that it can only be restored when the correct key is entered. The media that can be used in encryption technology are very wide. Electromagnetic waves, as an indispensable part of our lives, naturally become an important part of encryption technology. Electromagnetic waves have multiple dimensions such as amplitude, phase, polarization, angle, wavelength, etc. They can be used as keys in encryption technology, and can also be combined with multiple keys to increase the difficulty and cost of cracking encryption. Electromagnetic waves in the terahertz band are between microwaves and infrared light bands. Due to their special electromagnetic characteristics, they have also been invested in the research of encryption algorithms in recent years.

[0003] Terahertz (THz) waves refer to electromagnetic waves with a frequency range of 0.1THz to 10THz. They have the characteristics of transient, broadband, strong penetration, and low energy. Due to these characteristics, they have broad application prospects in biomedicine, safety and non-destructive testing, terahertz imaging, wireless communications, etc. At present, the main method for regulating terahertz waves is electromagnetic metamaterials.

[0004] Metamaterial is an artificial material composed of periodic arrangement of sub-wavelength unit structures. The desired electromagnetic effect can be obtained by artificially designing and arranging the unit structures, thereby obtaining many unique physical responses that natural materials do not have, such as negative refraction and perfect wave absorption. Metasurface is the two-dimensional counterpart of metamaterial. Its overall thickness is generally only a few tenths or even tens of tenths of the working wavelength, so that when electromagnetic waves are incident on the metasurface, it is equivalent to being incident on a certain two-dimensional surface, hence the name. Metasurface devices have simple structures, low processing difficulty, and low losses, and are excellent electromagnetic functional devices.

[0005] Currently, image encryption technology based on metasurfaces is mostly concentrated in the optical band, and there is a lack of research in the terahertz band. Summary of the invention

[0006] In view of this, an embodiment of the present invention provides a terahertz chiral metasurface to eliminate or improve one or more defects existing in the prior art.

[0007] One aspect of the present invention provides a terahertz chiral metasurface, the terahertz chiral metasurface comprising at least one first chiral structural unit and at least one second chiral structural unit;

[0008] The first chiral structural unit and the second chiral structural unit both include a base material layer, a dielectric layer and a metal pattern layer, wherein the dielectric layer is disposed between the base material layer and the metal pattern layer;

[0009] The metal pattern layer includes a first transverse bar, a second transverse bar, a third transverse bar, a first longitudinal bar and a second longitudinal bar, wherein the first longitudinal bar is arranged on one side of the upper surface of the dielectric layer, one end of each of the first transverse bar, the second transverse bar and the third transverse bar is connected to the first longitudinal bar and extends in a direction away from the first longitudinal bar, and the second longitudinal bar is perpendicular to the second transverse bar, and one end of the second longitudinal bar is connected to the second transverse bar;

[0010] In a specific implementation process, the first longitudinal strips in the first chiral structure unit and the second chiral structure unit are respectively located on opposite sides of the upper surface of the dielectric layer.

[0011] The first transverse strip, the second transverse strip and the third transverse strip in the first chiral structural unit and the second chiral structural unit have opposite extension directions;

[0012] One side of the metal pattern layer serves as an input port and an output port of the terahertz wave.

[0013] By adopting the above scheme, the terahertz chiral metasurface of this scheme includes at least one first chiral structural unit and at least one second chiral structural unit. The metal graphic structures of the two chiral structural units correspond to each other, and can output corresponding to each other through the chiral structures. By reflection, one side of the metal graphic layer is used as the input port and output port of the terahertz wave. This scheme can be applicable to the terahertz band, and based on the structure of the first chiral structural unit and the second chiral structural unit, it exhibits two opposite response characteristics to the terahertz band, which is suitable for encrypted transmission.

[0014] In some embodiments of the present invention, in the same first chiral structural unit or the second chiral structural unit, the lengths of the first transverse strip, the second transverse strip and the third transverse strip are all the same.

[0015] In some embodiments of the present invention, the first transverse strip, the second transverse strip and the third transverse strip are all perpendicular to the first longitudinal strip.

[0016] In some embodiments of the present invention, the second transverse bar is disposed between the first transverse bar and the third transverse bar.

[0017] In some embodiments of the present invention, one end of the second longitudinal strip is connected to one end of the second transverse strip and extends in the direction of the third transverse strip.

[0018] In some embodiments of the present invention, the cross-sections of the base material layer and the dielectric layer of the first chiral structural unit and the second chiral structural unit are both squares with the same side lengths.

[0019] In some embodiments of the present invention, the side length of the cross section of the base material layer and the dielectric layer is 145-155 μm.

[0020] In some embodiments of the present invention, the material of the base material layer is metal, the material of the dielectric layer is a high-performance polymer material, and the material of the metal pattern layer is gold.

[0021] In some embodiments of the present invention, the lengths of the first transverse strip, the second transverse strip, and the third transverse strip are in the range of 105 μm to 117 μm.

[0022] In some embodiments of the present invention, the length of the first longitudinal strip is 90 μm, and the length of the second longitudinal strip is in the range of 38 μm to 42 μm.

[0023] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention can be specifically pointed out and obtained in the specification and the accompanying drawings.

[0024] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention.

[0026] Figure 1 It is a schematic diagram of a first chiral structural unit or a second chiral structural unit with an opening direction facing left in the terahertz chiral metasurface of the present invention;

[0027] Figure 2 A schematic diagram of a first chiral structural unit or a second chiral structural unit with an opening direction facing leftward in one embodiment of the present invention;

[0028] Figure 3is the absorptivity of the chiral metasurface composed of the first chiral structural unit or the second chiral structural unit with the opening direction facing left for circularly polarized waves when the length of the first transverse strip in the present invention is 109 μm;

[0029] Figure 4 is a schematic diagram of a first chiral structural unit or a second chiral structural unit with an opening direction facing right when the length of the first transverse strip in the present invention is 109 μm;

[0030] Figure 5 is the absorptivity of the chiral metasurface composed of the first chiral structural unit or the second chiral structural unit with the opening direction facing right for circularly polarized waves when the length of the first transverse strip in the present invention is 109 μm;

[0031] Figure 6 The simulated circular dichroism curves of the chiral metasurface composed of the first chiral structural units or the second chiral structural units with four opening directions to the left and different first transverse strip lengths according to the present invention;

[0032] Figure 7 The test circular dichroism curves of the chiral metasurface composed of the first chiral structural units or the second chiral structural units with four opening directions to the left and different first transverse strip lengths according to the present invention;

[0033] Figure 8 Schematic diagram of the terahertz encrypted chiral metasurface of this scheme;

[0034] Fig. 9 This is a schematic diagram of the terahertz encryption chiral metasurface reflective encryption application in this scheme.

[0035] Description of Reference Numerals

[0036] Through the above-mentioned description of the accompanying drawings, combined with the embodiments of the present invention, the technical solution of the present invention can be more clearly understood and explained.

[0037] 1. Base material layer; 2. Dielectric layer; 31. First transverse strip; 32. Second transverse strip; 33. Third transverse strip; 34. First longitudinal strip; 35. Second longitudinal strip. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0039] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0040] Chiral metasurfaces are a special type of metasurfaces that have chiral characteristics or can produce chiral responses. Chiral metasurfaces have important application value in the fields of chiral sensing, chiral particle separation, and chiral regulation. The structure of a general chiral metamaterial can achieve the opposite effect of electromagnetic response between the original structure and the chiral structure. For example, the original structure has a high absorption rate for left-circular polarization (LCP) electromagnetic waves and a low absorption rate for right-circular polarization (RCP) waves, while its chiral structure has a low absorption rate for left-circular polarization waves and a high absorption rate for right-circular polarization waves. This feature can be regarded as a design method in encryption technology to encode the original information.

[0041] Metasurface imaging is a method of designing a metasurface to control electromagnetic waves to present a target pattern in the target area. In the design of encryption algorithms, metasurfaces can be used to encode encrypted information, and the corresponding key can be obtained through the response characteristics of the metasurface to electromagnetic waves to obtain a complete encryption system. There are currently two main imaging technologies for metasurfaces, and their design ideas are different. Holographic imaging encryption is a typical image encryption method, and its essence is to encode the information of the plaintext image through processes similar to optical transformations, such as interference and diffraction. Terahertz holographic image encryption can be achieved by designing a phase-controlled metasurface. Direct near-field imaging only uses the intensity distribution of electromagnetic waves to express information, and terahertz near-field image imaging and encryption can be achieved by designing an amplitude-controlled metasurface. In the encryption process, the parameters usually involved include wavelength, phase, diffraction distance, etc., which can be used together as multidimensional keys for the encryption system. Therefore, chiral metasurfaces can be used to encrypt image information in the terahertz band.

[0042] like Figure 1 , 2 , 4 and 8, the present invention provides a terahertz chiral metasurface, wherein the terahertz chiral metasurface includes at least one first chiral structural unit and at least one second chiral structural unit;

[0043] The first chiral structural unit and the second chiral structural unit both include a base material layer 1, a dielectric layer 2 and a metal pattern layer, wherein the dielectric layer 2 is disposed between the base material layer 1 and the metal pattern layer;

[0044] In the specific implementation process, the base material layer 1 is made of metal, and the metal material is preferably gold, with an electrical conductivity of 4.56×10 7S / m.

[0045] The metal pattern layer includes a plurality of metal strips of the same width. The metal strips are preferably made of gold. The metal strips include a first transverse strip 31 , a second transverse strip 32 , a third transverse strip 33 , a first longitudinal strip 34 and a second longitudinal strip 35 .

[0046] In a specific implementation process, the width of the metal strip is 15 μm.

[0047] In a specific implementation process, the thickness of the base material layer 1 is 0.2 μm; the thickness of the dielectric layer 2 is 50 μm; and the thickness of the metal pattern layer is 0.2 μm.

[0048] The metal pattern layer includes a first transverse bar 31, a second transverse bar 32, a third transverse bar 33, a first longitudinal bar 34 and a second longitudinal bar 35, wherein the first longitudinal bar 34 is arranged on one side of the upper surface of the dielectric layer 2, one end of each of the first transverse bar 31, the second transverse bar 32 and the third transverse bar 33 is connected to the first longitudinal bar 34 and extends in a direction away from the first longitudinal bar 34, and the second longitudinal bar 35 is perpendicular to the second transverse bar 32, and one end of the second longitudinal bar 35 is connected to the second transverse bar 32;

[0049] In a specific implementation process, the metal pattern layer is arranged on one side of the dielectric layer 2 , and the base material layer 1 is arranged on the other side of the dielectric layer 2 .

[0050] The first transverse strip 31, the second transverse strip 32 and the third transverse strip 33 in the first chiral structural unit and the second chiral structural unit have opposite extension directions;

[0051] By adopting the above scheme, the opening directions of the metal pattern layers of the first chiral structure unit and the second chiral structure unit are opposite. This scheme realizes the chiral absorption characteristics of circularly polarized terahertz waves through the metal pattern layer, as well as the different amplitude response characteristics of metal patterns with different structures to terahertz waves, and can realize image imaging encryption in the terahertz band.

[0052] Since the direction of the metal pattern can be changed, the opening direction of the metal pattern layer composed of metal strips is horizontally left or right. When the opening direction of the metal pattern is horizontally left, the absorption rate of the metamaterial for left-handed circularly polarized electromagnetic waves is much greater than the absorption rate for right-handed circularly polarized electromagnetic waves; when the opening direction of the metal pattern is horizontally right, the absorption rate of the metamaterial for left-handed circularly polarized electromagnetic waves is much less than the absorption rate for right-handed circularly polarized electromagnetic waves.

[0053] One side of the metal pattern layer serves as an input port and an output port of the terahertz wave.

[0054] By adopting the above scheme, the terahertz chiral metasurface of this scheme includes at least one first chiral structural unit and at least one second chiral structural unit. The structures of the two chiral structural units correspond to each other, and opposite outputs can be obtained through the chiral structures. By reflection, one side of the metal graphic layer is used as the input port and output port of the terahertz wave. This scheme can be applicable to the terahertz band, and based on the structure of the first chiral structural unit and the second chiral structural unit, it exhibits two opposite response characteristics to the terahertz band, which is suitable for encrypted transmission.

[0055] In some embodiments of the present invention, in the same first chiral structural unit or the second chiral structural unit, the lengths of the first transverse strip 31, the second transverse strip 32 and the third transverse strip 33 are all the same.

[0056] In some embodiments of the present invention, the first transverse strip 31 , the second transverse strip 32 , and the third transverse strip 33 are all perpendicular to the first longitudinal strip 34 .

[0057] In a specific implementation process, the first transverse strip 31 , the second transverse strip 32 and the third transverse strip 33 are parallel to each other, and the interval between the first transverse strip 31 and the second transverse strip 32 is 15 μm.

[0058] In a specific implementation, the length of the first longitudinal strip 34 is 90 μm.

[0059] In some embodiments of the present invention, the second transverse bar 32 is disposed between the first transverse bar 31 and the third transverse bar 33 .

[0060] In some embodiments of the present invention, one end of the second longitudinal strip 35 is connected to one end of the second transverse strip 32 and extends toward the third transverse strip 33 .

[0061] In a specific implementation process, the length of the second longitudinal strip 35 is 40 μm.

[0062] In some embodiments of the present invention, the cross-sections of the base material layer 1 and the dielectric layer 2 of the first chiral structural unit and the second chiral structural unit are both squares with the same side length.

[0063] In some embodiments of the present invention, the side length of the cross section of the base material layer 1 and the dielectric layer 2 is 145-155 μm.

[0064] In some embodiments of the present invention, the side length of the cross section of the base material layer 1 and the dielectric layer 2 is 150 μm.

[0065] In some embodiments of the present invention, the material of the base material layer 1 is metal, the material of the dielectric layer 2 is a high-performance polymer material, and the material of the metal pattern layer is gold, with an electrical conductivity of 4.56×10 7 S / m.

[0066] In a specific implementation process, the high-performance polymer material is polyimide, which has a dielectric constant of 3 and a loss tangent of 0.02.

[0067] In some embodiments of the present invention, the lengths of the first transverse strips 31 , the second transverse strips 32 , and the third transverse strips 33 range from 105 μm to 117 μm.

[0068] In some embodiments of the present invention, the length of the first transverse strip 31 , the second transverse strip 32 , and the third transverse strip 33 is 109 μm.

[0069] In a specific implementation process, in one terahertz chiral metasurface, there are multiple lengths of the first transverse strip 31 , the second transverse strip 32 and the third transverse strip 33 of different first chiral structural units or second chiral structural units.

[0070] In some embodiments of the present invention, the length of the second longitudinal strip 35 is in the range of 38 μm to 42 μm.

[0071] In some embodiments of the present invention, the length of the second longitudinal strip 35 is 40 μm.

[0072] Figure 3 The absorption rate of circularly polarized waves by the chiral metasurface composed of the first chiral structural unit or the second chiral structural unit with the opening direction to the left is shown when the length of the first transverse strip is 109μm. This result is the absorption response characteristic of the periodic chiral metasurface. The simulation was performed using CST Studio Suite software. When the terahertz wave is incident, a metasurface unit structure is established, periodic boundary conditions are set in the x and y directions, and the z direction facing the metal pattern upward is set as an open boundary condition. This is also used as the incident port and exit port of the terahertz wave. Further simulation can be used to obtain the reflection and transmission coefficient curves of the terahertz wave. According to Formula 1, the absorption rate is calculated.

[0073]

[0074] Among them, T RCP represents the transmission coefficient of right-hand circularly polarized wave, T LCP represents the transmission coefficient of left-hand circularly polarized wave, T x represents the transmission coefficient of x-ray polarized wave, T y represents the transmission coefficient of the y-polarized wave, R RCPrepresents the reflection coefficient of right-hand circularly polarized wave, R LCP represents the reflection coefficient of left-hand circularly polarized wave, R x represents the reflection coefficient of the x-ray polarized wave, R y A is the reflection coefficient of the y-polarized wave. RCP represents the absorptivity of right-hand circularly polarized waves, A LCP represents the absorption rate of left-hand circularly polarized waves, A x A represents the absorption rate of x-ray polarized waves. y Represents the absorption rate of y-polarized wave.

[0075] Figure 4 A schematic diagram of the structure of a chiral metasurface composed of a first chiral structural unit or a second chiral structural unit with an opening direction facing right is shown when the length of the first transverse strip is 109 μm.

[0076] Figure 5 The absorption rate of circularly polarized waves by the chiral metasurface composed of the first chiral structural unit or the second chiral structural unit with the opening direction facing right is shown. At this time, the absorption rate of the metasurface for left-handed circularly polarized waves and right-handed circularly polarized waves is exactly opposite to that of the original structure, which reflects the chirality of the metasurface.

[0077] In order to more conveniently compare the chiral response characteristics of the metasurface under different metal strip lengths, circular dichroism (CD) is defined as the difference between the absorptivity of the metasurface to left-handed circularly polarized electromagnetic waves and the absorptivity of right-handed circularly polarized electromagnetic waves. According to formula 2, it is calculated to be Figure 6 When the length of the metal strip is 109 μm, the chiral metasurface reaches the maximum circular dichroism value (CD value).

[0078] CD=A LCP -A RCP ; (2)

[0079] In order to verify the reliability and feasibility of the examples of the present invention, we physically processed the metasurface and conducted experiments in a terahertz time-domain spectroscopy system (THz-TDS). Figure 7 The test circular dichroism curves of four chiral metasurfaces with opening directions to the left and different lengths of the first transverse strip are shown, and the results correspond to the simulation results, verifying the reliability of the present invention.

[0080] According to the characteristics of an example of the present invention, an encryption method is provided, comprising: a chiral metasurface as described in the above embodiment.

[0081] By changing the length of the metal strip and the direction of the metal pattern opening, a variety of chiral metasurfaces with different electromagnetic responses are obtained. Under different incident conditions, the same metasurface responds differently. Combining the above two situations, multiple metasurface unit structures are selected to form an array to obtain different near-field imaging effects under different incident wave conditions.

[0082] Figure 8 This is an embodiment of the encryption method proposed by the present invention. Figure 8 As shown, the metasurface array is composed of metasurface units of different chirality. The material of the base material layer 1 is metal gold, with a thickness of 0.2μm and a period length of 175μm; the material of the dielectric layer 2 is polyimide, with a dielectric constant of 3.0, a loss tangent of 0.02, and a thickness of 50μm; the material of the metal pattern layer is gold, with a thickness of 0.2μm. The length of the metal strip ranges from 105μm to 117μm, and the opening direction of the metal pattern is horizontally left or horizontally right. In the case of terahertz wave incidence, open boundary conditions are set in the x, y, and z directions, and the upward z direction of the metal pattern is used as the incident port and the exit port of the terahertz wave. The surface electric field distribution of the metasurface array is further obtained through simulation to achieve near-field imaging encryption.

[0083] Fig. 9 The surface electric field distribution of a metasurface array of a specific embodiment of the present invention under the incidence of terahertz waves in different polarization states, and the image after uniform distribution processing are shown. The steps of encryption using a terahertz chiral metasurface are as follows: 1. Encode the two sets of information to be encrypted into two two-dimensional codes respectively, and obtain two two-dimensional code images composed of black pixel blocks and white pixel blocks; 2. Arrange the metasurface array using the reflection response characteristics of chiral metasurfaces with different structures, aiming to achieve a surface electric field distribution corresponding to the two-dimensional code image under different polarization state incident waves; 3. Use electromagnetic simulation software or physical testing methods to obtain the surface electric field distribution of the chiral metasurface array, and obtain the decoded image after binarization and uniformization. It can be seen that under the incidence of LCP and y-line polarized waves, the electric field distribution on the array surface presents two different two-dimensional code images. Fig. 9 The QR code image encoding information corresponding to LCP incidence is "testa", which can be scanned for verification; the QR code image corresponding to y-line polarization wave incidence is an invalid QR code image that cannot be recognized and can be used as interference. In the case of RCP incidence, the reflection result shows a missing QR code image; in the case of x-line polarization wave incidence, the reflection result has no image. It can be verified that chiral metasurfaces can be used in terahertz image encryption methods and obtain good practical results. And its implementation method is simple and can be widely used.

[0084] It should be understood by those skilled in the art that the exemplary components, systems and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software or a combination of the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier.

[0085] It should be clear that the present invention is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present invention.

[0086] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or replace features of other embodiments.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A terahertz chiral metasurface, characterized in that: The terahertz chiral metasurface includes at least one first chiral structural unit and at least one second chiral structural unit; The first chiral structural unit and the second chiral structural unit both include a base material layer, a dielectric layer and a metal pattern layer, wherein the dielectric layer is disposed between the base material layer and the metal pattern layer; The metal pattern layer includes a first transverse bar, a second transverse bar, a third transverse bar, a first longitudinal bar and a second longitudinal bar, wherein the first longitudinal bar is arranged on one side of the upper surface of the dielectric layer, one end of each of the first transverse bar, the second transverse bar and the third transverse bar is connected to the first longitudinal bar and extends in a direction away from the first longitudinal bar, and the second longitudinal bar is perpendicular to the second transverse bar, and one end of the second longitudinal bar is connected to the second transverse bar; The first transverse strip, the second transverse strip and the third transverse strip in the first chiral structural unit and the second chiral structural unit have opposite extension directions; One side of the metal pattern layer serves as an input port and an output port of the terahertz wave.

2. The terahertz chiral metasurface according to claim 1, characterized in that: In the same first chiral structural unit or the second chiral structural unit, the lengths of the first transverse strip, the second transverse strip and the third transverse strip are all the same.

3. The terahertz chiral metasurface according to claim 1, characterized in that: The first transverse strip, the second transverse strip and the third transverse strip are all perpendicular to the first longitudinal strip.

4. The terahertz chiral metasurface according to claim 1, characterized in that: The second transverse strip is disposed between the first transverse strip and the third transverse strip.

5. The terahertz chiral metasurface according to claim 1, characterized in that: One end of the second longitudinal strip is connected to one end of the second transverse strip and extends toward the third transverse strip.

6. The terahertz chiral metasurface according to claim 1, characterized in that: The cross sections of the base material layer and the dielectric layer of the first chiral structural unit and the second chiral structural unit are both squares with the same side length.

7. The terahertz chiral metasurface according to claim 6, characterized in that: The side lengths of the cross sections of the base material layer and the dielectric layer are 145-155 μm.

8. The terahertz chiral metasurface according to claim 1, characterized in that: The material of the base material layer is metal, the material of the dielectric layer is high-performance polymer material, and the material of the metal pattern layer is gold.

9. The terahertz chiral metasurface according to claim 1, characterized in that: The lengths of the first transverse strip, the second transverse strip, and the third transverse strip are in the range of 105 μm to 117 μm.

10. The terahertz chiral metasurface according to claim 1, characterized in that: The length of the first longitudinal strip is 90 μm, and the length of the second longitudinal strip is in the range of 38 μm to 42 μm.

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