3-bit optically controlled discrete open-ring metasurface based on phase change material

Abstract

This invention discloses a 3-bit optically controlled discrete open-ring metasurface based on phase change materials, belonging to the field of metasurface design. From bottom to top, it consists of a C-shaped open-ring metal backplate layer, a substrate, and an annular metal patch with equally spaced slots. The equally spaced slots of the annular metal patch are filled with phase change material. Laser irradiation alters the crystal phase of the phase change material, causing the entire open-ring unit to exhibit different equivalent morphologies, thus achieving different responses to incident electromagnetic waves. Therefore, this invention utilizes the characteristics of optical control to reduce signal interference, improve response speed, and simplify the integration process. Its advantages are reflected in improved antenna reliability and reduced antenna size, providing a new electromagnetic wave control method and hardware foundation for modern communication systems.

Description

Technical Field

[0001] This invention relates to the field of metasurface design technology, and in particular to a 3-bit optically controlled discrete open-ring metasurface based on phase change materials. Background Technology

[0002] With the continuous development of wireless communication technology, in order to achieve higher information capacity and information rate transmission, people require the communication spectrum to continuously shift to higher frequencies. However, existing high-frequency reconfigurable metasurfaces often use electronic control methods such as varactor diodes and PIN diodes to control the cells. This leads to the complexity of circuit design and difficulties in board layout design, and also causes coupling and interference problems in the transmission of electromagnetic wave signals. Therefore, finding a simpler and less interference-prone method for electromagnetic wave control has become an urgent issue to be addressed. Summary of the Invention

[0003] This invention provides a 3-bit optically controlled discrete open-loop metasurface based on phase change materials. By utilizing the characteristics of optical control, it reduces signal interference, improves response speed, and simplifies the integration process. Its advantages are reflected in improving antenna reliability and reducing antenna size, providing a new electromagnetic wave control method and hardware foundation for modern communication systems.

[0004] This invention provides a 3-bit optically controlled discrete open-ring metasurface based on phase change material, consisting of a C-shaped open-ring metal backing layer, a substrate, and an annular metal patch with equally spaced gaps, from bottom to top.

[0005] Phase change material is filled into the equally spaced gaps of the annular metal patch. The crystal phase of the phase change material in different gaps is changed by laser irradiation, so that the entire open ring unit is equivalent to a C-shaped open ring with different opening sizes and orientations. By adjusting the opening direction and size of the C-shaped open ring, the amplitude and phase of the incident wave and the outgoing wave are controlled, so that the phase response of the cross-polarized reflected wave is changed, thus realizing different responses to the incident electromagnetic wave.

[0006] Optionally, in one embodiment of the present invention, the amplitude and phase of the reflected wave are controlled by adjusting the structural parameters of the opening of the C-shaped opening ring; by changing the crystal phase of the phase change material in the gap, the phase change material is made to have two different properties: semi-insulating and metal-like, so that the metasurface unit is equivalent to a C-shaped opening ring with different opening sizes and orientations, and the reflection response of the metasurface unit is dynamically controlled.

[0007] Optionally, in one embodiment of the present invention, the phase change material is GeTe material.

[0008] Optionally, in one embodiment of the present invention, the crystal phase of the phase change material is changed by laser irradiation, so that the entire open-ring unit exhibits different equivalent morphologies, including:

[0009] The crystalline phases of phase change materials include amorphous and crystalline states. In the crystalline state, the phase change material has strong electrical conductivity and metal-like properties, enabling the metal patches on both sides of the gap to connect. In the amorphous state, the phase change material has poor electrical conductivity and cannot enable the metal patches on both sides of the gap to connect.

[0010] For typical reconfigurable metasurfaces, the control of cell elements often employs electronic control methods such as varactor diodes and PIN diodes. This presents challenges such as complex control circuit design, difficult layout design, and coupling and interference to the electromagnetic wave signals transmitting information. The 3-bit optically controlled discrete open-ring metasurface based on phase change materials in this invention offers the following advantages:

[0011] 1. The metasurface proposed in this invention uses a simple unit structure and has a simple electromagnetic wave modulation mechanism, which enables designers to design the required metasurface structure according to functional requirements.

[0012] 2. The structure proposed in this invention has a simple processing flow and a small size, which can be applied to the terahertz frequency band and is easy to integrate.

[0013] 3. The laser control signal used in this invention does not interfere with the electromagnetic waves transmitting information while performing dynamic structural control of the unit, and has a fast response speed, enabling more convenient electromagnetic wave modulation function.

[0014] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0016] Figure 1 This is a schematic diagram of the design of a 3-bit optically controlled discrete open ring metasurface according to an embodiment of the present invention;

[0017] Figure 2 This is an equivalent diagram of a 3-bit optically controlled discrete open-ring metasurface according to an embodiment of the present invention;

[0018] Figure 3 The equivalent open-loop structure corresponding to the eight unit states in this embodiment of the invention;

[0019] Figure 4 The cross-polarization wave S of the optically controlled 3-bit unit in this embodiment of the invention. 11 Amplitude response simulation results;

[0020] Figure 5The cross-polarization wave S of the optically controlled 3-bit unit in this embodiment of the invention. 11 Phase response simulation results;

[0021] Figure 6 The reflection pattern of a 30×30 metasurface array is shown in this embodiment of the invention when the pointing angle is set to 30°. (a), (b), and (c) are simulation results for 0.52 THz, 0.53 THz, and 0.54 THz, respectively.

[0022] Figure 7 The present invention provides a reflection pattern of a 30×30 metasurface array when the pointing angle is set to 50°, wherein (a), (b), and (c) are simulation results for 0.52THz, 0.53THz, and 0.54THz, respectively. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] like Figure 1 and Figure 2 As shown, the 3-bit optically controlled discrete open-ring metasurface based on phase change material consists of a C-shaped open-ring metal backing layer, a substrate, and an annular metal patch with equally spaced gaps, from bottom to top.

[0025] The annular metal patch is filled with a phase change material in its equally spaced gaps. By irradiating it with a laser, the crystal phase of the phase change material in different gaps is changed, so that the entire open ring unit presents different equivalent shapes as C-shaped open rings with different opening sizes and orientations, thus achieving different responses to incident electromagnetic waves.

[0026] Understandably, the C-shaped open-loop is a resonant structure commonly used in the microwave and terahertz frequency bands. By adjusting the opening direction and size of the open loop, the amplitude and phase of the incident and emitted waves can be controlled, thereby changing the phase response of the cross-polarized reflected wave and thus altering the energy distribution of the reflected wave between x-polarization and y-polarization. Therefore, the C-shaped open-loop unit is an amplitude- and phase-independently tunable metasurface unit with a high degree of modulation freedom.

[0027] like Figure 2 As shown, the technical solution of this invention includes a reflective light-controlled metasurface unit based on a C-shaped open-ring structure. The design incorporates elements such as a C-shaped open-ring structure, an annular metal patch with equally spaced gaps, a GeTe material layer filling the gaps, a sapphire substrate, and a metal backplate layer.

[0028] Metasurface elements utilize the principle of C-shaped open rings to control electromagnetic waves. By creating openings within a complete circular ring, the symmetry of the shape is broken, thus altering the equivalent impedance along the two orthogonal components of the electric field. This creates a relative difference, resulting in different amplitude and phase responses for the two orthogonal components of the incident electromagnetic wave. By adjusting the structural parameters of the openings, the amplitude and phase of the reflected wave can be effectively controlled. Furthermore, by altering the crystal phase of the phase change material within the structural gaps, giving it both semi-insulating and metallic properties, the element can be equivalent to C-shaped open rings with different opening sizes and orientations, thereby dynamically controlling the element's reflection response.

[0029] The amplitude of electromagnetic waves can be controlled by adjusting the opening direction of the C-shaped open ring. Changing the opening size can yield different phase responses, and the phase change can cover 360°. To enable the open ring unit to have reconfigurable characteristics, this invention utilizes the bistable phase transition properties of the phase change material GeTe to design a programmable discrete open ring unit.

[0030] like Figure 1 and Figure 2 As shown, a metallic ground reflective layer is deposited on the bottom of a silicon dioxide substrate, and the main structure of the unit cell is a metal ring with gaps. Sixteen points are selected at equal intervals on the ring, with an angle of 22.5° between them. A gap of a certain width is constructed with each point as the center, serving as the "switch" for the discrete open ring, and numbered sequentially as #1-16. The gaps are filled with the phase change material GeTe. By changing the crystal phase of the GeTe material, the entire open ring unit cell exhibits different equivalent morphologies, thereby achieving different responses to incident electromagnetic waves.

[0031] For example, Figure 1 The GeTe material in gaps numbered 1, 2, and 16 is depicted as amorphous, while the GeTe in the remaining gaps is depicted as crystalline. Crystalline GeTe exhibits strong electrical conductivity and metallic-like properties, thus it can conduct electricity with the metal rings on either side of the gap and can be simplified as a metal in the model. Amorphous GeTe, on the other hand, has poor electrical conductivity and cannot effectively connect the two sides of the gap, preventing isolated metallic regions from connecting with adjacent metal rings. Therefore, it can be simplified as air. The simplified equivalent model is shown below. Figure 2 As shown, this model can be equivalent to a simple C-shaped open ring. By adjusting the crystal phase of GeTe at each gap, we can obtain open ring units with different opening sizes or different opening directions, and the amplitude and phase of the reflected electromagnetic waves will change accordingly.

[0032] Considering the number of phase-changing switches and the characteristics of the phase response of the open-loop unit, we implemented a 3-bit phase-encoded metasurface using this discrete open-loop unit. 3-bit encoding requires 2... 3= 8 reflection amplitudes are basically the same, and the reflection phases are equally divided into 360°, that is, the phase difference between adjacent states is 45°.

[0033] Based on the principle of open-ring units, the unit state coding table shown in Table 1 is obtained. GeTe in the gaps mentioned in the table is defined as amorphous, while GeTe in other locations is defined as crystalline. The equivalent schematic diagram of each state unit is shown below. Figure 3 As shown, each equivalent structure corresponds to states 1-8.

[0034] Table 1 Discrete Open-Loop Element State Encoding

[0035] Status coding Amorphous GeTe corresponding gap number State 1 1、2、3、4、5、13、14、15、16 State 2 1、2、3、4、14、15、16 State 3 1、2、3、15、16 State 4 1、2、16 State 5 1、9、10、11、12、13、14、15、16 State 6 10、11、12、13、14、15、16 State 7 11、12、13、14、15 State 8 12、13、14

[0036] The structural parameters of the cell were scanned and optimized using CST full-wave simulation, and the final cell values ​​are shown in Table 2. A 200µm thick silica glass substrate was used, with a cell period of 120µm, an outer ring radius of 51.4µm, an inner ring radius of 42.9µm, and a metal ring width of 8.5µm. Both the metal layer and the GeTe layer were 0.5µm thick, and the gap angle in the metal ring was 2°.

[0037] Table 2. Structural parameters of discrete open-loop element (unit: μm)

[0038]

[0039] The simulation results of the cross-polarized wave reflection coefficients for the eight states of this unit are as follows: Figure 4 and Figure 5 As shown, within the frequency range of 0.51THz-0.56THz, the amplitude response of each state of the unit is above -2dB and the difference is not significant; the difference in phase response between adjacent states is about 45°, which can meet the design requirements of 3-bit reflective metasurface units.

[0040] The aforementioned metasurface elements were arranged into an array, and the CST full-wave simulation results were observed. Within the operating frequency band of the elements, three frequency points—0.52 THz, 0.53 THz, and 0.54 THz—were selected. A 30×30 array was illuminated with a normally incident plane wave, with reflection angles set to 30° and 50° respectively. The state of each array element was set according to the calculated coding matrix. The CST full-wave simulation pattern is shown below. Figure 6 and Figure 7 As shown in the image, due to the use of 3-bit encoding, the reflected wave has only one main beam. Figure 5As shown, at a frequency of 0.52 THz, the reflected beam can accurately point to the set 30° direction, while at 0.53 THz and 0.54 THz, the pointing angle is 29°, which deviates from the preset angle by 1°. This may be caused by errors due to inaccurate phase stepping between different states of the unit. From... Figure 6 As can be seen from the radiation pattern, when the pointing angle is set to 50°, the sidelobe level differs from the main beam by about -10dB at each operating frequency, demonstrating the performance advantage of this 3-bit metasurface.

[0041] The 3-bit optically controlled discrete open-loop metasurface based on phase change material proposed in this embodiment of the invention utilizes the characteristics of optical control to reduce signal interference, improve response speed, and simplify the integration process. Its advantages are reflected in improving antenna reliability and reducing antenna size, providing a new electromagnetic wave control method and hardware foundation for modern communication systems.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] Furthermore, 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0044] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

Claims

1. A 3-bit optically controlled discrete open-ring metasurface based on phase change materials, characterized in that, From bottom to top, the structure consists of a C-shaped open ring metal backing layer, a substrate, and an annular metal patch with equally spaced gaps. Phase change material is filled into the equally spaced gaps of the annular metal patch. The crystal phase of the phase change material in different gaps is changed by laser irradiation, so that the entire open ring unit is equivalent to a C-shaped open ring with different opening size and orientation. By adjusting the opening direction and size of the C-shaped open ring, the amplitude and phase of the incident wave and the outgoing wave are controlled, so that the phase response of the cross-polarized reflected wave is changed, and different responses to the incident electromagnetic wave are achieved. The amplitude and phase of the reflected wave can be controlled by adjusting the structural parameters of the C-shaped opening ring. By changing the crystal phase of the phase change material in the gap, the phase change material can be made to have two different properties: semi-insulating and metal-like. This makes the metasurface unit equivalent to a C-shaped opening ring with different opening sizes and orientations, and dynamically controls the reflection response of the metasurface unit.

2. The 3-bit optically controlled discrete open-ring metasurface based on phase change material according to claim 1, characterized in that, The phase change material is GeTe.

3. The 3-bit optically controlled discrete open-ring metasurface based on phase change material according to claim 1, characterized in that, By altering the crystal phase of a phase change material through laser irradiation, the entire open-ring unit cell can exhibit different equivalent morphologies, including: The crystalline phases of phase change materials include amorphous and crystalline states. In the crystalline state, the phase change material has strong electrical conductivity and metal-like properties, enabling the metal patches on both sides of the gap to connect. In the amorphous state, the phase change material has poor electrical conductivity and cannot enable the metal patches on both sides of the gap to connect.

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