An electrode for providing driving for a MEMS metasurface based on a grating structure and a preparation method thereof

Abstract

This application discloses an electrode based on a grating structure for driving MEMS metasurfaces and its fabrication method. The MEMS metasurface comprises metasurface units and a silicon dioxide substrate from top to bottom. The metasurface units are made of gold. A driving electrode based on a grating structure is embedded in the middle of the silicon dioxide substrate, and an electrical contact area is provided at one end of the driving electrode. This application uses a grating structure driving electrode to provide electrostatic driving force for the MEMS metasurface. When the grating period is much smaller than the wavelength of light in the working band, the incident light will not be decomposed into multi-order diffracted light by the grating, allowing the incident light to be transmitted along the original propagation direction, resulting in advantages such as high transmittance and a wide tuning range. It can be widely applied in the field of cantilever beam controlled metasurface technology.

Description

Technical Field

[0001] This application relates to the field of cantilever beam-controlled metasurface technology, and in particular to an electrode based on a grating structure that provides a drive for MEMS metasurfaces and its fabrication method. Background Technology

[0002] Currently, mainstream solutions for tunable metasurfaces in MEMS include using driven thin films to induce deformation or changing the height of the structure through electrostatically driven cantilever beams to achieve terahertz wave manipulation. Among these, cantilever beams are widely studied and applied due to their high sensitivity, similar fabrication process to standard integrated circuits, and ease of integration.

[0003] Existing technologies disclose a U-shaped terahertz metasurface using silicon as the cantilever beam driving electrode, achieving resonance at 0.51 THz and 0.55 THz under TE and TM wave incidence, respectively. However, the use of silicon as the driving electrode, with its high refractive index, results in low transmittance. Existing technologies also disclose a MEMS cantilever beam reconfigurable terahertz metamaterial using gold (with a 0.2 μm thick silicon dioxide coating) as the driving electrode, exhibiting a 16.5 dB contrast switching performance at 0.48 THz. However, to avoid short circuits, the silicon dioxide coating results in a narrower tunable range. Summary of the Invention

[0004] To address the aforementioned technical problems, the purpose of this application is to provide an electrode with high transmittance and high tuning range based on a grating structure for driving MEMS metasurfaces, and a method for fabricating the same.

[0005] To achieve the above objectives, one aspect of this application proposes an electrode that provides a drive for a MEMS metasurface based on a grating structure. The MEMS metasurface includes a metasurface unit and a silicon dioxide substrate from top to bottom. The metasurface unit is made of gold. A drive electrode based on a grating structure is embedded in the middle of the silicon dioxide substrate. An electrical contact area is provided at one end of the drive electrode.

[0006] In some embodiments, the metasurface unit includes a plurality of row array metasurfaces, the position of the driving electrode corresponds to the center of each row array metasurface, and the metasurface unit and the driving electrode are independent of each other and do not directly contact each other.

[0007] In some embodiments, the driving electrode comprises, from top to bottom, a titanium thin film, a gold electrode, and another titanium thin film.

[0008] In some embodiments, the thickness of the titanium thin film is 5 nm, and the thickness of the gold electrode is any value between 180 nm and 500 nm.

[0009] In some embodiments, the linewidth of the driving electrode is 4 μm.

[0010] In some embodiments, the thickness of the silicon dioxide substrate is 500 nm.

[0011] In some embodiments, the thickness of the metasurface unit is 200 nm and the linewidth is 3 μm, the crack width in the middle of each row array metasurface is 8 μm, the vertical stripe spacing of each row array metasurface is 51 μm, and the spacing between two adjacent row array metasurfaces is 3 μm.

[0012] To achieve the above objectives, another aspect of this application proposes a method for fabricating an electrode that provides a drive for a MEMS metasurface based on a grating structure, comprising the following steps: Prepare a silicon dioxide substrate; A driving electrode film is deposited on the silicon dioxide substrate, and then the driving electrode film is patterned to obtain a driving electrode based on a grating structure. A silicon dioxide substrate is deposited again on the driving electrode based on the grating structure, and then a metasurface thin film is deposited on the silicon dioxide substrate. The metasurface thin film is patterned to obtain a metasurface unit.

[0013] In some embodiments, depositing a driving electrode film on the silicon dioxide substrate and then patterning the driving electrode film to obtain a driving electrode based on a grating structure specifically includes: The driving electrode film is prepared by depositing a titanium thin film-gold electrode-titanium thin film on the silicon dioxide substrate by magnetron sputtering. The driving electrode film is photolithographically etched using a hard contact method, and then etched using a dry or wet method to obtain the driving electrode based on the grating structure.

[0014] In some embodiments, the process of depositing the driving electrode film on the silicon dioxide substrate by magnetron sputtering a titanium thin film-gold electrode-titanium thin film specifically includes: Obtain titanium and gold sputtering targets; The silicon dioxide substrate is connected to a positive potential, and the titanium target is connected to a negative potential; Pump the chamber down to below 2×10 3 A high vacuum environment of Pa is created, and then argon gas of 0.5 Pa is introduced into the chamber; A titanium thin film was deposited on the silicon dioxide substrate by applying a 300W DC sputtering source. Replace the titanium target with the gold target and repeat the magnetron sputtering process to deposit a gold electrode on the titanium film. The gold target is replaced with the titanium target, and the magnetron sputtering process is repeated to deposit a titanium thin film on the gold electrode, thereby obtaining the driving electrode thin film.

[0015] The beneficial effects of this application are as follows: This application discloses an electrode based on a grating structure for driving MEMS metasurfaces and its fabrication method. The MEMS metasurface comprises metasurface units and a silicon dioxide substrate from top to bottom. The metasurface units are made of gold, and a driving electrode based on a grating structure is embedded in the middle of the silicon dioxide substrate. An electrical contact area is provided at one end of the driving electrode. This application uses a grating structure driving electrode to provide electrostatic driving force for the MEMS metasurface. When the grating period is much smaller than the wavelength of light in the working band, the incident light will not be decomposed into multi-order diffracted light by the grating, allowing the incident light to be transmitted along the original propagation direction, resulting in the advantages of high transmittance and high tuning range. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments of this application are described below. It should be understood that the drawings described below are only for the purpose of clearly illustrating some embodiments of the technical solutions in this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a MEMS metasurface based on a grating structure as a driving electrode, provided in one embodiment of this application. Figure 2 This is a top view of a driving electrode provided in one embodiment of this application; Figure 3 A top view of the functional unit of a MEMS metasurface with a grating structure as the driving electrode in the disconnected state, provided in one embodiment of this application; Figure 4 A top view of the functional unit of a MEMS metasurface in the closed state, based on a grating structure as the driving electrode, according to an embodiment of this application; Figure 5 A side view of a functional unit in the disconnected state of a MEMS metasurface based on a grating structure as a driving electrode, according to an embodiment of this application; Figure 6 A comparison graph showing the changes in transmittance of MEMS metasurfaces with frequency and switching state between electrodes with and without grating structures, provided in one embodiment of this application. Figure 7 This is a flowchart illustrating the steps of a method for fabricating an electrode based on a grating structure to drive a MEMS metasurface, according to one embodiment of this application.

[0018] Reference numerals: 1. Metasurface unit; 2. Driving electrode; 3. Silicon dioxide substrate; 4. Electrical contact area. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0020] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various concepts, but unless otherwise stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words “if,” “when,” or “in response to a determination” as used herein may be interpreted as “when…” or “when…” or “in response to a determination.”

[0021] As used in this application, the terms "at least one", "multiple", "each", "any", etc., "at least one" includes one, two or more, "multiple" includes two or more, "each" refers to each of the corresponding multiples, and "any" refers to any one of the multiples.

[0022] Currently, mainstream solutions for tunable metasurfaces in MEMS include using driven thin films to induce deformation or changing the height of the structure through electrostatically driven cantilever beams to achieve terahertz wave manipulation. Among these, cantilever beams are widely studied and applied due to their high sensitivity, similar fabrication process to standard integrated circuits, and ease of integration.

[0023] Existing technologies disclose a U-shaped terahertz metasurface using silicon as the cantilever beam driving electrode, achieving resonance at 0.51 THz and 0.55 THz under TE and TM wave incidence, respectively. However, the use of silicon as the driving electrode, with its high refractive index, results in low transmittance. Existing technologies also disclose a MEMS cantilever beam reconfigurable terahertz metamaterial using gold (with a 0.2 μm thick silicon dioxide coating) as the driving electrode, exhibiting a 16.5 dB contrast switching performance at 0.48 THz. However, to avoid short circuits, the silicon dioxide coating results in a narrower tunable range.

[0024] In view of this, this application proposes an electrode based on a grating structure to provide driving force for a MEMS metasurface. The MEMS metasurface includes metasurface units and a silicon dioxide substrate from top to bottom. The metasurface units are made of gold, and a driving electrode based on a grating structure is embedded in the middle of the silicon dioxide substrate. An electrical contact area is provided at one end of the driving electrode. This application uses a grating structure driving electrode to provide electrostatic driving force for the MEMS metasurface. When the grating period is much smaller than the wavelength of light in the working band, the incident light will not be decomposed into multi-order diffracted light by the grating, so that the incident light is transmitted along the original propagation direction, resulting in the advantages of high transmittance and high tuning range.

[0025] Reference Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of a MEMS metasurface based on a grating structure as a driving electrode, provided in one embodiment of this application. Figure 2 This is a top view of a driving electrode provided in one embodiment of this application. This embodiment of the application proposes an electrode that provides driving for a MEMS metasurface based on a grating structure. The MEMS metasurface includes a metasurface unit 1 and a silicon dioxide substrate 3 from top to bottom. The metasurface unit 1 is made of gold. A driving electrode 2 based on a grating structure is embedded in the middle of the silicon dioxide substrate 3. An electrical contact area 4 is provided at one end of the driving electrode 2.

[0026] Specifically, the driving electrode 2 is made of a material with high electrical conductivity, and the substrate is made of a material that is transparent to terahertz waves.

[0027] It should be noted that the embodiments of this application use a grating structure driving electrode to provide electrostatic driving force for the MEMS metasurface. When the grating period is much smaller than the wavelength of the light in the working band, the incident light will not be decomposed into multi-order diffracted light by the grating, allowing the incident light to be transmitted along the original propagation direction, resulting in the advantages of high transmittance and high tuning range. Furthermore, the grating structure can be scaled and adjusted for the required band to achieve full-band coverage.

[0028] Reference Figure 1 , Figure 3 , Figure 4 as well as Figure 5 , Figure 3 This is a top view of the functional unit of a MEMS metasurface with a grating structure as the driving electrode in the disconnected state, according to one embodiment of this application. Figure 4 This is a top view of the functional unit of a MEMS metasurface with a grating structure as the driving electrode in the closed state, according to one embodiment of this application. Figure 5This is a side view of the functional unit of a MEMS metasurface with a grating structure as the driving electrode in the disconnected state according to one embodiment of this application. Further, as an optional implementation, the metasurface unit 1 includes multiple row array metasurfaces, and the position of the driving electrode 2 corresponds to the middle of each row array metasurface. The metasurface unit 1 and the driving electrode 2 are independent of each other and do not directly contact each other.

[0029] It should be noted that the embodiments of this application adopt a structure in which the electrodes and metasurfaces are independent of each other, which will not cause adverse effects of thermal expansion coefficient mismatch.

[0030] As an optional implementation, the driving electrode 2 includes, from top to bottom, a titanium thin film, a gold electrode, and another titanium thin film.

[0031] It should be noted that gold was chosen as the electrode material in this application because of its good electrical conductivity and its near-perfect conductor properties in the terahertz band. However, a single layer of gold has poor adhesion to silicon dioxide and is easy to peel off. Therefore, titanium was added as an adhesion layer between gold and silicon dioxide in this application. Titanium was chosen because it can form a bond with silicon dioxide and can also diffuse with gold to form a strong adhesion.

[0032] Furthermore, while titanium or chromium can be used as the adhesion layer, chromium is easily etched, thus increasing the etching rate. If both the adhesion layer and the subsequent sacrificial layer are made of chromium, the original electrode may be etched during the sacrificial layer etching process, causing damage. Therefore, in this embodiment, titanium is selected as the adhesion layer for manufacturing the electrode, while chromium is used as the sacrificial layer in subsequent MEMS processes.

[0033] It is understood that the embodiments of this application use metal as the electrode material, which brings the advantage of high conductivity.

[0034] As an optional further implementation, the thickness of the titanium film is 5 nm, and the thickness of the gold electrode is any value between 180 nm and 500 nm.

[0035] Reference Figure 3 As an optional implementation, the linewidth of the driving electrode 2 is 4 μm.

[0036] Reference Figure 1 and Figure 3 As an optional implementation, the thickness of the silicon dioxide substrate 3 is 500 nm.

[0037] Reference Figure 3 As an optional implementation, the thickness of the metasurface unit 1 is 200 nm, the linewidth is 3 μm, the crack width in the middle of each row array metasurface is 8 μm, the upper and lower stripe spacing of each row array metasurface is 51 μm, and the spacing between two adjacent row array metasurfaces is 3 μm.

[0038] In some optional embodiments, the thickness of the gold electrode can be 230 nm. For example, as shown... Figure 1 and Figure 3 As shown, in this embodiment, silicon dioxide with a thickness of 500 nm is used as the substrate material; the linewidth W1 of the driving electrode 2 is 4 μm, wherein the thickness of the upper and lower titanium thin films is 5 nm, and the thickness of the middle gold electrode is 230 nm; the thickness of the metasurface unit 1 is 200 nm, the linewidth W2 is 3 μm, the crack width D in the middle of each row array metasurface is 8 μm, the spacing L between the upper and lower stripes is 51 μm, the edge spacing G between the upper edge of the top row array metasurface and the edge of the entire unit is 1.5 μm, the edge spacing G between the lower edge of the bottom row array metasurface and the edge of the entire unit is also 1.5 μm, and the spacing between adjacent row arrays is 2G, i.e., 3 μm.

[0039] It is understandable that the size parameters of the aforementioned metasurface unit 1, driving electrode 2, and silicon dioxide substrate 3 can be set according to actual needs.

[0040] The structure of the electrode providing a drive for the MEMS metasurface based on the grating structure in the embodiments of this application has been described above. It can be recognized that, compared with the prior art, the embodiments of this application have the following advantages: I. The driving electrodes using a grating structure provide electrostatic driving force for the MEMS metasurface. When the grating period is much smaller than the wavelength of the light in the working band, the incident light will not be decomposed into multi-order diffracted light by the grating, allowing the incident light to be transmitted along the original propagation direction, resulting in the advantages of high transmittance and high tuning range. Furthermore, the grating structure can be scaled and adjusted for the required band to achieve full-band coverage.

[0041] Second, using metal as the electrode material brings the advantage of high conductivity.

[0042] Third, the use of an independent structure for electrodes and metasurfaces avoids the adverse effects of thermal expansion coefficient mismatch.

[0043] To further illustrate the effectiveness of the embodiments of this application, a Y-polarized terahertz wave was incident on a metasurface based on a grating structure as the driving electrode, with the gold metasurface as the incident surface and the substrate as the exit surface. The transmittance was tested as a function of frequency and switching state. Figure 6 The figure shows a comparison of the transmittance of MEMS metasurfaces with and without grating-structured electrodes as a function of frequency and switching state. Figure 6 As can be seen, the metasurface based on a grating structure as the driving electrode proposed in this application achieves almost 100% transparency, and its transmittance is almost the same as that of a metasurface without a grating structure electrode.

[0044] Reference Figure 7 ,Figure 7 The present application provides a flowchart of a method for fabricating an electrode that provides a drive for a MEMS metasurface based on a grating structure. The present application also provides a method for fabricating an electrode that provides a drive for a MEMS metasurface based on a grating structure, including the following steps S101 to S103: Step S101: Prepare a silicon dioxide substrate; Step S102: Deposit a driving electrode thin film on a silicon dioxide substrate, and then pattern the driving electrode thin film to obtain a driving electrode based on a grating structure. Step S103: Deposit a silicon dioxide substrate again on the driving electrode based on the grating structure, and then deposit a metasurface thin film on the silicon dioxide substrate. Pattern the metasurface thin film to obtain a metasurface unit.

[0045] Specifically, a thin adhesion layer is first deposited on a silicon dioxide substrate by magnetron sputtering, followed by the deposition of the conductive metal material for the electrode. Then, another thin adhesion layer is deposited. The purpose of this adhesion layer is to improve the adhesion of the electrode metal material and prevent peeling during subsequent processes. The shape of the driving electrode is then obtained using photolithography and etching techniques. After obtaining the embedded electrode, a substrate material layer is deposited, followed by a metasurface material layer. The corresponding pattern is then obtained using photolithography.

[0046] As an optional implementation, the step of depositing a driving electrode film on a silicon dioxide substrate and then patterning the driving electrode film to obtain a driving electrode based on a grating structure can be further divided into the following steps S1021 to S1022: Step S1021: On a silicon dioxide substrate, a driving electrode film is prepared by depositing a titanium thin film-gold electrode-titanium thin film by magnetron sputtering. Step S1022: Photolithography is performed on the driving electrode film by hard contact, and then the driving electrode film is etched by dry or wet method to obtain the driving electrode based on the grating structure.

[0047] In some optional embodiments, a 500 μm thick silicon dioxide layer is used as the substrate material because silicon dioxide has good transmittance in the terahertz band, ensuring that the design efficiency of the metasurface unit structure is not compromised by substrate loss. Before sputtering, the substrate needs to be cleaned, first with Piranha solution for 15 minutes, then with deionized water, and finally dried at 145°C for 30 minutes to obtain a clean substrate. After obtaining the clean substrate, titanium-gold-titanium is deposited as the electrode material by magnetron sputtering; wherein, the titanium thin film, with a thickness of 5 nm, serves as the adhesion layer between gold and silicon dioxide. Then, hard contact is used with a pattern resolution of 1 μm and an exposure dose of 175 mJ / cm².2 Photolithography was used to obtain the corresponding patterned grating structure driving electrode; the linewidth of the driving electrode was 4 μm, and the thickness of the gold electrode was 230 nm. After obtaining the driving electrode, a 180 nm thick silicon dioxide layer was first deposited on it, followed by a 5 nm titanium adhesion layer, and finally a 200 nm gold metamaterial was deposited. Finally, a metasurface with a linewidth W2 of 3 μm, a gap width D of 8 μm, a vertical stripe spacing L of 51 μm, and an adjacent row array spacing 2G of 3 μm was obtained through photolithography.

[0048] As a further optional implementation, the step of depositing a titanium thin film-gold electrode-titanium thin film on a silicon dioxide substrate by magnetron sputtering to obtain a driving electrode film can be further divided into the following steps S1031 and S1032: Step S10211: Obtain titanium and gold target materials; Step S10212: Connect the silicon dioxide substrate to a positive potential and the titanium target to a negative potential; Step S10213: Pump the chamber down to below 2×10 3 A high vacuum environment of Pa was created, and then argon gas at 0.5 Pa was introduced into the chamber. Step S10214: Apply a 300W DC sputtering source to deposit a titanium thin film on a silicon dioxide substrate; Step S10215: Replace the titanium target with a gold target and repeat the magnetron sputtering process to deposit a gold electrode on the titanium film. Step S10216: Replace the gold target with a titanium target and repeat the magnetron sputtering process to deposit a titanium thin film on the gold electrode to obtain the driving electrode thin film.

[0049] In some alternative embodiments, the substrate is first connected to a positive potential, the titanium target is connected to a negative potential, and then the chamber floor vacuum is reduced to better than 2 × 10⁻⁶. 3 In an environment of Pa, argon gas at 0.5 Pa is introduced to ionize the target material into argon ions and electrons, followed by a 300W DC sputtering source. Under the influence of the 300W DC sputtering source, the high-energy charged argon ions move at high speed towards the cathode region under the influence of the electric field, irradiating the target surface and sputtering uncharged particles. These electrically neutral particles, not bound by the electric and magnetic fields, gain kinetic energy and move at high speed to the substrate surface, gradually growing into a titanium thin film. Based on the same steps, the titanium target is replaced with a gold target, and a gold electrode layer is deposited on the titanium thin film. Finally, the gold target is replaced with a titanium target, and a titanium thin film is deposited on the gold electrode to obtain the driving electrode thin film.

[0050] It should be noted that the embodiments of this application adopt a CMOS-compatible manufacturing process, which brings the advantages of easy processing and convenient mass production.

[0051] The contents of the above-described electrode embodiments that provide actuation for MEMS metasurfaces based on grating structures are all applicable to the embodiments of this fabrication method. The specific functions implemented by the embodiments of this fabrication method are the same as those of the above-described electrode embodiments that provide actuation for MEMS metasurfaces based on grating structures, and the beneficial effects achieved are also the same as those achieved by the above-described electrode embodiments that provide actuation for MEMS metasurfaces based on grating structures.

[0052] In the foregoing description of this specification, the references to terms such as "one embodiment," "another embodiment," or "some embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. 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.

[0053] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

[0054] The above is a detailed description of the preferred embodiments of this application, but this application is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. An electrode for driving a MEMS metasurface based on a grating structure, wherein the MEMS metasurface comprises, from top to bottom, metasurface units and a silicon dioxide substrate, the metasurface units being made of gold, characterized in that, The silicon dioxide substrate has a driving electrode based on a grating structure embedded in its middle, and one end of the driving electrode is provided with an electrical contact area.

2. The electrode for driving MEMS metasurfaces based on grating structure according to claim 1, characterized in that, The metasurface unit includes multiple row array metasurfaces, and the position of the driving electrode corresponds to the middle of each row array metasurface. The metasurface unit and the driving electrode are independent of each other and do not directly contact each other.

3. The electrode for providing actuation to a MEMS metasurface based on a grating structure according to claim 1, characterized in that, The driving electrode comprises, from top to bottom, a titanium thin film, a gold electrode, and another titanium thin film.

4. The electrode for driving MEMS metasurfaces based on grating structure according to claim 3, characterized in that, The titanium thin film has a thickness of 5 nm, and the gold electrode has a thickness of any value between 180 nm and 500 nm.

5. The electrode for providing actuation to a MEMS metasurface based on a grating structure according to claim 1, characterized in that, The linewidth of the driving electrode is 4 μm.

6. The electrode for providing actuation to a MEMS metasurface based on a grating structure according to claim 1, characterized in that, The thickness of the silicon dioxide substrate is 500 nm.

7. The electrode for driving MEMS metasurfaces based on grating structure according to claim 2, characterized in that, The metasurface unit has a thickness of 200 nm and a linewidth of 3 μm. The crack width in the middle of each row array metasurface is 8 μm. The vertical spacing between the upper and lower stripes of each row array metasurface is 51 μm, and the spacing between two adjacent row array metasurfaces is 3 μm.

8. A method for fabricating an electrode based on a grating structure to provide actuation for a MEMS metasurface, as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Prepare a silicon dioxide substrate; A driving electrode film is deposited on the silicon dioxide substrate, and then the driving electrode film is patterned to obtain a driving electrode based on a grating structure. A silicon dioxide substrate is deposited again on the driving electrode based on the grating structure, and then a metasurface thin film is deposited on the silicon dioxide substrate. The metasurface thin film is patterned to obtain a metasurface unit.

9. The preparation method according to claim 8, characterized in that, The step of depositing a driving electrode thin film on the silicon dioxide substrate, and then patterning the driving electrode thin film to obtain a driving electrode based on a grating structure, specifically includes: The driving electrode film is prepared by depositing a titanium thin film-gold electrode-titanium thin film on the silicon dioxide substrate by magnetron sputtering. The driving electrode film is photolithographically etched using a hard contact method, and then etched using a dry or wet method to obtain the driving electrode based on the grating structure.

10. The preparation method according to claim 9, characterized in that, The process of depositing the driving electrode film on the silicon dioxide substrate by magnetron sputtering a titanium thin film-gold electrode-titanium thin film specifically includes: Obtain titanium and gold sputtering targets; The silicon dioxide substrate is connected to a positive potential, and the titanium target is connected to a negative potential; Pump the chamber down to below 2×10 3 A high vacuum environment of Pa is created, and then argon gas of 0.5 Pa is introduced into the chamber; A titanium thin film was deposited on the silicon dioxide substrate by applying a 300W DC sputtering source. Replace the titanium target with the gold target and repeat the magnetron sputtering process to deposit a gold electrode on the titanium film. The gold target is replaced with the titanium target, and the magnetron sputtering process is repeated to deposit a titanium thin film on the gold electrode, thereby obtaining the driving electrode thin film.

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