Graphene 2-bit metasurface coding structure and coding method

Abstract

The application relates to a graphene 2-bit metasurface coding structure and a coding method, and belongs to the technical field of tunable metamaterials. The metasurface coding structure is composed of a substrate layer and a graphene layer unit structure array arranged in sequence, wherein the graphene layer is arranged on the upper surface of the substrate layer; the application is suitable for the field of terahertz communication and has important application value in the direction of encoders, multi-frequency switches and slow light devices.

Description

Technical Field

[0001] This invention relates to the field of terahertz communication technology, specifically to a graphene 2-bit metasurface coding structure and coding method. Background Technology

[0002] Terahertz waves refer to electromagnetic waves with frequencies ranging from 0.1 THz to 10 THz, positioned between infrared and microwaves in the electromagnetic spectrum. With the rapid development of terahertz technology, its applications in communication, imaging, and detection are becoming increasingly widespread. As a communication method, terahertz waves offer advantages over microwave communication in terms of transmission bandwidth and communication speed. Furthermore, their strong penetrating power and high security make terahertz communication technology a very promising field.

[0003] Most existing terahertz wave manipulation methods employ multi-layer structures, with each layer selecting a specific frequency terahertz wave. These multi-layer structures require sophisticated manufacturing processes, leading to high production costs. Another method utilizes programmable gate arrays (PGAs) for terahertz wave manipulation, but this requires the terahertz wave to illuminate a specific area for encoding, thus placing stringent demands on optical path conditions and hindering the large-scale application of terahertz wave communication technology.

[0004] Terahertz communication technology requires a terahertz encoding device that is not demanding in terms of manufacturing process, has a simple structure, and is easy to control. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a graphene 2-bit metasurface coding structure and coding method.

[0006] This invention is achieved through the following technical solution:

[0007] A graphene 2-bit metasurface coding structure is periodically composed of a substrate layer and a graphene layer array unit disposed on the upper surface of the substrate layer; the center of the graphene layer coincides exactly with the center of the substrate layer and is axially symmetric about the horizontal and vertical directions; the graphene layer includes a first graphene unit and a second graphene unit; the center of the first graphene unit coincides exactly with the center of the substrate layer and is axially symmetric about the horizontal and vertical directions; the first graphene unit includes a first graphene elliptical subunit and a second graphene elliptical subunit, and the centers of the first graphene elliptical subunit and the second graphene elliptical subunit coincide exactly and coincide exactly with the center position of the substrate layer; the relationship between the second graphene elliptical subunit and the second graphene elliptical subunit is a relationship of clockwise rotation of 90 degrees; the second graphene unit contains four L-shaped unit structures, and the relationship between any two of the four L-shaped unit structures is a relationship of clockwise rotation of 90 degrees, 180 degrees, and 270 degrees; the L-shaped unit structure includes a first L-shaped subunit and a second L-shaped subunit; the boundaries of the first L-shaped subunit and the second L-shaped subunit coincide exactly with the boundary of the substrate layer; the first L-shaped subunit and the second L-shaped subunit are axially symmetric about the diagonal of the substrate layer.

[0008] In the above solution, the length and width of the substrate layer are equal; the material of the substrate layer is silicon material; the thickness of the substrate layer is 0.1 - 1 μm; the material of the graphene layer is graphene material; the thickness of the graphene layer is less than or equal to the thickness of the substrate layer. <0000​​​​​​​The method implemented by the above-mentioned graphene 2-bit metasurface coding structure involves a terahertz wave emitted by a terahertz transmitter being transmitted through the graphene 2-bit metasurface coding structure and then received by a terahertz receiver. The Fermi levels of the first and second graphene units are controlled by an externally applied motor to control the terahertz wave of the graphene 2-bit metasurface coding structure to exhibit different digital state codes. Its characteristics are:

[0012] When the bias voltage applied to the first graphene unit and the second graphene unit is low, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "00".

[0013] When the bias voltage applied to the first graphene unit is high and the bias voltage applied to the second graphene unit is low, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "01".

[0014] When the bias voltage applied to the first graphene unit is low and the bias voltage applied to the second graphene unit is high, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "10".

[0015] When the bias voltage applied to the first graphene unit and the second graphene unit is high, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "11".

[0016] As described above, the graphene 2-bit metasurface coding structure of the present invention has the following effects:

[0017] This invention proposes a metasurface coding structure using terahertz communication technology, which can meet the 2-bit coding requirement. Because the coding is controlled by an externally applied bias voltage, the coding of the metasurface coding structure can be fully electrically controlled, thus meeting the requirement of high coding speed. This invention features simple manufacturing process, simple structure, and high coding speed. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a unit structure of the graphene 2-bit metasurface coding structure of the present invention;

[0020] Figure 2 This is a schematic diagram of the 3×3 unit structure of the graphene 2-bit metasurface coding structure of the present invention;

[0021] Figure 3 This is a top view of a unit structure of the graphene 2-bit metasurface coding structure of the present invention;

[0022] Figure 4 This is the terahertz transmission spectrum of the graphene 2-bit metasurface encoded structure of the present invention; Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. It should be noted that the directional terms mentioned in the examples, such as "up," "down," "middle," "left," "right," "front," and "rear," are only for reference to the directions in the accompanying drawings. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0024] An embodiment of a graphene 2-bit metasurface coding structure, for example Figure 1 and 2 As shown, it consists of an N×M array of periodic graphene layer square unit structures disposed on the upper surface of the substrate. In this example, N=3, M=3, and the side length of the square graphene layer unit structure is 10μm.

[0025] like Figure 3 As shown, the graphene layer unit structure includes a first graphene unit and a second graphene unit; the center of the first graphene unit is located at the center of the substrate layer and is symmetrical about the lateral and longitudinal axes; the center of the graphene layer unit structure is completely coincident with the center of the substrate layer and is symmetrical about the lateral and longitudinal axes.

[0026] The first graphene unit includes a first graphene elliptical subunit and a second graphene elliptical subunit. The center of the first graphene elliptical subunit and the center of the second graphene elliptical subunit completely coincide with the center of the substrate layer. The relationship between the second graphene elliptical subunit and the second graphene elliptical subunit is a 90-degree clockwise rotation.

[0027] The second graphene unit comprises four L-shaped unit structures, and the relationship between any two L-shaped unit structures is that any L-shaped unit is rotated clockwise by 90 degrees, 180 degrees, and 270 degrees; the L-shaped unit structure includes a first L-shaped sub-unit and a second L-shaped sub-unit; the boundaries of the first L-shaped sub-unit and the second L-shaped sub-unit completely coincide with the boundary of the substrate layer; the first L-shaped sub-unit and the second L-shaped sub-unit are symmetrical about the diagonal axis of the substrate layer.

[0028] The substrate layer has equal length and width; the substrate layer is made of silicon; in this example, the substrate layer thickness is 0.2 μm; the graphene layer unit structure is made of graphene; the thickness of the graphene layer unit structure is less than or equal to the thickness of the substrate layer; in this example, the thickness of the graphene layer unit structure is 1 nm.

[0029] The major axes of the first graphene elliptical subunit and the second graphene elliptical subunit are smaller than the major axes of the first L-shaped subunit and the second L-shaped subunit; the minor axes of the first graphene elliptical subunit and the second graphene elliptical subunit are larger than the minor axes of the first L-shaped subunit and the second L-shaped subunit.

[0030] In this example, the major axis r1 of the first and second graphene elliptical subunits is 3 μm, and the minor axis r11 is 0.7 μm; the first L-shaped subunit in this example is a quarter of an ellipse with a major axis r2 of 3.5 μm and a minor axis r22 of 0.5 μm; the second L-shaped subunit in this example is a quarter of an ellipse with a major axis r2 of 3.5 μm and a minor axis r22 of 0.5 μm.

[0031] This example uses binary codes 00, 01, 10, and 11 as the four digital states of this encoding structure. The first and second digits in the encoding represent the digital states of terahertz transmittance at frequency A and frequency B, respectively. This example uses 50% terahertz wave transmittance as the threshold. Transmittance below 50% is considered low transmittance, and the digital state code is "0". Transmittance above 50% is considered high transmittance, and the digital state code is "1".

[0032] In the initial stage, terahertz waves are incident on the graphene 2-bit metasurface coding structure, and an external bias voltage is used to individually control the Fermi levels of the first and second graphene units in the graphene layer unit structure. When the terahertz waves emitted by the terahertz wave transmitter are perpendicularly incident on this invention, the first graphene unit resonates at frequency band B, and the second graphene unit resonates at frequency band A. Frequency A is the frequency at which the lowest transmittance occurs in frequency band A, and frequency B is the frequency at which the lowest transmittance occurs in frequency band B. When the Fermi levels of the graphene layer unit structure change, the resonant frequencies generated by the first and second graphene units shift, resulting in differences in transmittance at frequencies A and B, specifically high and low transmittance.

[0033] In the initial stage, the bias voltage applied to the first and second graphene units is low, and the Fermi levels of the first and second graphene units are also low. The graphene 2-bit metasurface coding structure has low transmittance at both frequencies A and B, and the corresponding digital state code is "00".

[0034] By changing the externally applied bias voltage and increasing the Fermi level of the first graphene unit alone, the frequency band in which the first graphene unit undergoes plasmon resonance shifts, causing the surface plasmon resonance corresponding to frequency band B to disappear, and high transmittance only appears in frequency band B; the graphene 2-bit metasurface coding structure has low transmittance at frequency A and high transmittance at frequency B, and the corresponding digital state coding is "01".

[0035] By changing the externally applied bias voltage and increasing the Fermi level of the second graphene unit alone, the frequency band in which the second graphene unit undergoes plasmon resonance shifts, causing the surface plasmon resonance corresponding to frequency band A to disappear, and high transmittance only appears in frequency band A; the graphene 2-bit metasurface encoded structure has high transmittance at frequency A and low transmittance at frequency B, and the corresponding digital state encoding is "10".

[0036] By changing the externally applied bias voltage, the Fermi levels of the first and second graphene units are increased. At this time, the frequency bands where the first and second graphene units undergo plasmon resonance shift, causing the surface plasmon resonances corresponding to frequency bands B and A to disappear, resulting in high transmittance in both frequency bands B and A. The graphene 2-bit metasurface coding structure has high transmittance in both frequency A and frequency band B, and the corresponding digital state code is "11".

[0037] Figure 4The obtained terahertz transmission spectrum is shown in the figure. The vertical axis represents transmittance, and the horizontal axis represents frequency, in THz. The two vertical dashed lines indicate the transmittance at 3.773 THz for frequency A and 4.842 THz for frequency B, which determines the digital state encoding.

[0038] The transmission spectrum with digital state encoding "00" shows minimum transmittance values ​​at both frequency A and frequency B, with a transmittance of 4.91% at frequency A and 3.55% at frequency B, both of which are low transmittance.

[0039] The transmission spectrum with digital state encoding "01" shows a minimum transmittance at frequency A and a maximum transmittance at frequency B. The transmittance at frequency A is 4.90%, which is low transmittance, and the transmittance at frequency B is 98.46%, which is high transmittance.

[0040] The transmission spectrum with digital state encoding "10" shows a maximum transmittance at frequency A and a minimum transmittance at frequency B. The transmittance at frequency A is 92.91%, which is high transmittance, while the transmittance at frequency B is 4.20%, which is low transmittance.

[0041] The transmission spectrum with digital state encoding "11" shows maximum transmittance at both frequency A and frequency B, with a transmittance of 94.21% at frequency A and 95.77% at frequency B, both of which are high transmittance.

[0042] In summary, this invention modulates the Fermi levels of the first and second graphene units by adjusting the externally applied bias voltage, thereby changing the transmittance of frequencies A and B, and ultimately achieving 2-bit encoding functionality.

[0043] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0044] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0045] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A graphene 2-bit metasurface coding structure, characterized in that: It consists of a substrate layer and N×M arrays of periodic graphene layer square unit structures arranged on the upper surface of the substrate layer; M is an integer greater than or equal to 2, and N is an integer greater than or equal to 2; The center of the graphene layer unit structure coincides completely with the center of the substrate layer and is axially symmetric about the horizontal and vertical directions; The graphene layer unit structure includes a first graphene unit and a second graphene unit; the center of the first graphene unit coincides completely with the center of the substrate layer and is axially symmetric about the horizontal and vertical directions; The first graphene unit includes a first graphene elliptical sub-unit and a second graphene elliptical sub-unit, and the centers of the first graphene elliptical sub-unit and the second graphene elliptical sub-unit coincide completely and also coincide completely with the center position of the substrate layer; the relationship between the second graphene elliptical sub-unit and the second graphene elliptical sub-unit is a 90-degree clockwise rotation relationship; The second graphene unit contains four L-shaped unit structures, and the relationship between any two of the four L-shaped unit structures is a 90-degree, 180-degree, or 270-degree clockwise rotation relationship of any one L-shaped unit; the L-shaped unit structure includes a first L-shaped sub-unit and a second L-shaped sub-unit; the boundaries of the first L-shaped sub-unit and the second L-shaped sub-unit coincide completely with the boundary of the substrate layer; the first L-shaped sub-unit and the second L-shaped sub-unit are axially symmetric about the diagonal of the substrate layer.

2. The graphene 2-bit metasurface coding structure according to claim 1, characterized in that: The length and width of the substrate layer are equal; the material of the substrate layer is silicon material; the thickness of the substrate layer is 0.1 - 1 μm; The material of the graphene layer unit structure is graphene material; the thickness of the graphene layer unit structure is less than or equal to the thickness of the substrate layer; the length and width of the graphene layer unit structure are equal.

3. The graphene 2-bit metasurface coding structure according to claim 1, characterized in that: The long axis r1 of the first graphene elliptical sub-unit and the second graphene elliptical sub-unit satisfies 2.5 μm < r1 < 4.4 μm, and the short axis r11 satisfies 0.2 μm < r11 < 1.5 μm; The first L-shaped sub-unit is a quarter of an ellipse with a long axis r2 satisfying 2.6 μm < r2 < 4.5 μm and a short axis r22 satisfying 0.1 μm < r22 < 1.4 μm; The second L-shaped sub-unit is a quarter of an ellipse with a long axis r2 satisfying 2.6 μm < r2 < 4.5 μm and a short axis r22 satisfying 0.1 μm < r22 < 1.4 μm; The long axis of the first graphene elliptical sub-unit and the second graphene elliptical sub-unit is less than the long axis of the first L-shaped sub-unit and the second L-shaped sub-unit; the short axis of the first graphene elliptical sub-unit and the second graphene elliptical sub-unit is greater than the short axis of the first L-shaped sub-unit and the second L-shaped sub-unit.

4. The graphene 2-bit metasurface coding structure according to claim 1, characterized in that: The resonant frequency generated by the first graphene unit is located in frequency band B, and the resonant frequency generated by the second graphene unit is located in frequency band A, and frequency band A and frequency band B are different frequency bands.

5. An encoding method using a graphene 2-bit metasurface encoding structure as described in claim 1, wherein terahertz waves emitted by a terahertz transmitter are received by a terahertz receiver after being transmitted through the graphene 2-bit metasurface encoding structure; the Fermi levels of the first and second graphene units are controlled by externally applied electrodes to control the terahertz waves of the graphene 2-bit metasurface encoding structure to exhibit different digital state encodings; characterized in that: When the bias voltage applied to the first graphene unit and the second graphene unit is low, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "00". When the bias voltage applied to the first graphene unit is high and the bias voltage applied to the second graphene unit is low, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "01". When the bias voltage applied to the first graphene unit is low and the bias voltage applied to the second graphene unit is high, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "10". When the bias voltage applied to the first graphene unit and the second graphene unit is high, the digital state code corresponding to the graphene 2-bit metasurface coding structure is "11".

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