3-bit light-operated discrete split ring metasurface based on phase change material

Abstract

The invention discloses a 3-bit light-operated discrete split ring metasurface based on a phase-change material, and belongs to the field of metasurface design, the metasurface comprises a C-shaped split ring-shaped metal backboard layer, a substrate and an annular metal patch with uniformly-spaced gaps from bottom to top, the uniformly-spaced gaps of the annular metal patch are filled with the phase-change material, and the phase-change material is arranged between the substrate and the annular metal patch. The crystal phase of the phase change material is changed through laser irradiation, so that the whole split ring unit presents different equivalent forms, and different responses to incident electromagnetic waves are realized. Therefore, by utilizing the characteristics of light control, the signal interference is reduced, the response speed is improved, the integration process is simplified, the superiority is that the reliability of the antenna is improved, the size of the antenna is reduced, and a new electromagnetic wave regulation and control means and a hardware basis are provided for a modern communication system.

Description

Technical Field

[0001] The present invention relates to the technical field of metasurface design, and in particular to a 3-bit light-controlled discrete open-ring metasurface based on phase change material. Background Art

[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 move continuously to high frequency. However, the existing high-frequency reconfigurable metasurfaces often use electronic control methods such as varactor diodes and PIN diodes to control units, which leads to the complexity of circuit design and difficulties in board design, and also causes coupling and interference problems in the transmission of electromagnetic wave signals. Therefore, seeking a simpler and less interfering electromagnetic wave control method has become an urgent issue to be solved. Summary of the invention

[0003] The present invention provides a 3-bit light-controlled discrete open-ring metasurface based on phase change material. By utilizing the characteristics of light control, signal interference is reduced, response speed is increased, and the integration process is simplified. Its superiority is reflected in improving the reliability of the antenna and reducing the size of the antenna, providing a new electromagnetic wave control method and hardware foundation for modern communication systems.

[0004] The embodiment of the present invention provides a 3-bit light-controlled discrete open ring metasurface based on phase change material, which comprises a metal backplane layer, a substrate and an annular metal patch with equally spaced gaps in the shape of a C-shaped open ring from bottom to top;

[0005] Phase change material is filled in the equally spaced gaps of the annular metal patch, and 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 directions. 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, thereby achieving 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 regulated by adjusting the structural parameters of the opening of the C-shaped open ring; by changing the crystal phase of the phase change material in the gap, the phase change material has two different properties of semi-insulating / metal-like, so that the metasurface unit is equivalent to a C-shaped open ring with different opening sizes and orientations, and the reflection response of the metasurface unit is dynamically regulated.

[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 presents different equivalent forms, including:

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

[0010] For general reconfigurable metasurfaces, the control method for units is often to use electrical control methods such as varactor diodes and PIN diodes, which will face problems such as complex design of electrical control signal control circuits, difficult layout design, and certain coupling and interference with electromagnetic wave signals that transmit information. The 3-bit optically controlled discrete open ring metasurface based on phase change materials in the embodiment of the present invention has the following beneficial effects:

[0011] 1. The unit structure adopted by the metasurface proposed in the present invention is simple, and the regulation mechanism of electromagnetic waves is not complicated, which enables designers to design the required metasurface structure according to functional requirements.

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

[0013] 3. The laser control signal used in the present invention will not interfere with the electromagnetic waves that transmit information while dynamically controlling the structure of the unit, and has a fast response speed, thereby realizing a more convenient electromagnetic wave control function.

[0014] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0018] Figure 3 The equivalent open ring structures corresponding to the eight unit states of the embodiment of the present invention;

[0019] Figure 4 is the cross-polarized wave S of the optically controlled 3-bit unit of the embodiment of the present invention. 11 Amplitude response simulation results;

[0020] Figure 5is the cross-polarized wave S of the optically controlled 3-bit unit of the embodiment of the present invention. 11 Phase response simulation results;

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

[0022] Figure 7 This is the reflection pattern of the 30×30 metasurface array when the pointing angle is set to 50° according to an embodiment of the present invention, where (a), (b), and (c) are simulation results of 0.52THz, 0.53THz, and 0.54THz, respectively. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used 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 light-controlled discrete open ring metasurface based on phase change material consists of a metal backplane layer in the shape of a C-shaped open ring, a substrate, and an annular metal patch with equally spaced gaps from bottom to top;

[0025] Phase change material is filled in the equally spaced gaps of the annular metal patch, and the crystal phase of the phase change material in different gaps is changed by laser irradiation, so that the entire open ring unit presents different equivalent forms, namely C-shaped open rings with different opening sizes and directions, achieving different responses to the incident electromagnetic waves.

[0026] It is understandable that the C-shaped split ring is a resonant structure commonly used in microwave and terahertz frequency bands. By adjusting the opening direction and size of the split ring, the amplitude and phase of the incident wave and the outgoing wave can be controlled, so that the phase response of the cross-polarized reflected wave changes, thereby changing the distribution of the reflected wave energy between x-polarization and y-polarization. Therefore, the C-shaped split ring unit is an amplitude-phase independently adjustable metasurface unit with a high degree of modulation freedom.

[0027] like Figure 2 As shown, the technical solution of the present invention includes a reflective light-control metasurface unit based on a C-shaped open ring structure. The design introduces 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 backplane layer.

[0028] The metasurface unit uses the principle of electromagnetic wave regulation by a C-shaped open ring, and opens on a complete circular ring, breaking the symmetry of the shape, thereby changing the equivalent impedance along the two orthogonal components of the electric field, producing a relative difference, and then causing the two orthogonal components of the incident electromagnetic wave to produce different amplitude and phase responses. By adjusting the structural parameters of the opening, the amplitude and phase of the reflected wave can be effectively regulated. By changing the crystal phase of the phase change material in the structural gap so that it has two different properties of semi-insulating / metal-like, the unit can be made equivalent to a C-shaped open ring with different opening sizes and directions, thereby dynamically regulating the reflection response of the unit.

[0029] By adjusting the opening direction of the C-shaped open ring, the amplitude of the electromagnetic wave can be controlled. By changing the opening size, different phase responses can be obtained, and the phase change can cover 360°. In order to make the open ring unit reconfigurable, the present invention uses the bistable phase change characteristics of the phase change material GeTe to design an editable discrete open ring unit.

[0030] like Figure 1 and Figure 2 As shown in the figure, a metal reflective layer is covered on the bottom of the silicon dioxide substrate, and the main structure of the unit is a metal ring with a gap. 16 points are selected at equal intervals on the ring, with an angle of 22.5° between each other. A gap with a certain width is constructed with each point as the center, as the "switch" of the discrete open ring, numbered #1-16 in sequence. The gap is filled with phase change material GeTe. By changing the crystal phase of the GeTe material, the entire open ring unit presents different equivalent forms, thereby achieving different responses to the incident electromagnetic wave.

[0031] For example, Figure 1 The GeTe materials in the three gaps numbered 1, 2, and 16 are set to amorphous state, and the GeTe in the remaining gaps are set to crystalline state. Crystalline GeTe has strong conductivity and metal-like properties, so it can be connected to the metal rings on both sides of the gap and can be simplified as metal in the model; while amorphous GeTe has poor conductivity and cannot effectively connect the two sides of the gap, resulting in the isolated metal area being unable to connect to the adjacent metal rings, so it can be simplified to air. The simplified equivalent model is as follows Figure 2 As shown in the figure, it can be seen that the model is equivalent to a simple C-shaped split ring. By adjusting the crystal phase of GeTe at each gap, we can obtain split ring units with different opening sizes or different opening directions, and the amplitude and phase of the reflected electromagnetic wave will also change accordingly.

[0032] Considering the number of phase change switches and the characteristics of the phase response of the split ring unit, we use the discrete split ring unit to realize a 3-bit phase-encoded metasurface. 3-bit encoding requires 2 3=8 reflection amplitudes are basically consistent, and the reflection phase is equally divided into 360°, that is, the unit state in which the phase difference between adjacent states is 45°.

[0033] Combining the principle of the open ring unit, the unit state coding table shown in Table 1 is obtained. The GeTe in the gap mentioned in the table is set to an amorphous state, and the GeTe in the remaining positions is set to a crystalline state. The equivalent schematic diagram of each state unit is shown in Figure 3 As shown, each equivalent structure corresponds to states 1-8 respectively.

[0034] Table 1 Discrete open ring unit state coding

[0035] Status Code The corresponding gap number of amorphous GeTe 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 unit were scanned and optimized using CST full-wave simulation, and the final unit values ​​are shown in Table 2. A 200um thick silica glass substrate was used, the unit period was 120um, the outer radius of the open ring was 51.4um, the inner radius was 42.9um, and the width of the metal ring was 8.5um. The thickness of the metal layer and the GeTe layer was 0.5um, and the gap angle in the metal ring was 2°.

[0037] Table 2 Discrete open ring unit structural parameters (unit: um)

[0038]

[0039] The simulation results of the cross-polarization wave reflection coefficients of the eight states of the unit are as follows: Figure 4 and Figure 5 In 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 large; 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 above metasurface units are arrayed and the CST full-wave simulation results are observed. Three frequencies of 0.52THz, 0.53THz, and 0.54THz are selected within the unit's operating frequency band. A normal incident plane wave is used to illuminate the 30×30 array, and the reflection angles are set to point to 30° and 50°, respectively. The state of each array element is set according to the calculated coding matrix. The CST full-wave simulation directional diagram is shown in the figure. Figure 6 and Figure 7 As shown in Figure 1. It can be seen that due to the use of 3-bit encoding, the reflected wave has only one main beam. Figure 5As shown in the figure, at 0.52THz, the reflected beam can accurately point to the set 30° direction, while at 0.53THz and 0.54THz, the pointing angle is 29°, which is 1° different from the preset. This may be caused by the error caused by the inaccurate phase step between the states of the unit. Figure 6 It can be seen from the radiation pattern that when the pointing angle is set to 50°, the sidelobe level has a difference of about -10dB compared to the main beam at each operating frequency, which reflects the performance advantage of the 3-bit metasurface.

[0041] The 3-bit light-controlled discrete open-ring metasurface based on phase change material proposed in an embodiment of the present invention utilizes the characteristics of light control to reduce signal interference, improve response speed and simplify the integration process. Its superiority is reflected in improving the reliability of the antenna and reducing the size of the antenna, providing new electromagnetic wave control means and hardware foundation for modern communication systems.

[0042] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0044] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

Claims

1. A 3-bit light-controlled discrete open-ring metasurface based on phase change material, characterized in that: From bottom to top, it is a metal backplane layer in the shape of a C-shaped open ring, a substrate, and an annular metal patch with equally spaced gaps; Phase change material is filled in the equally spaced gaps of the annular metal patch, and 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 directions. 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, thereby achieving different responses to the incident electromagnetic wave.

2. The 3-bit light-controlled discrete open-ring metasurface based on phase change material according to claim 1, characterized in that: By adjusting the structural parameters of the C-shaped opening ring, the amplitude and phase of the reflected wave can be controlled; By changing the crystal phase of the phase change material in the gap, the phase change material can 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.

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

4. The 3-bit light-controlled discrete open-ring metasurface based on phase change material according to claim 1, characterized in that: By changing the crystal phase of the phase change material through laser irradiation, the entire open ring unit presents different equivalent morphologies, including: The crystal phases of phase change materials include amorphous and crystalline states. In the crystalline state, the phase change material has strong conductivity and metal-like properties, which connects the metal patches on both sides of the gap. The amorphous phase change material has poor conductivity and cannot connect the metal patches on both sides of the gap.

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