Dual-polarization modulation optical transparent metasurface based on graphene ionic gel

Abstract

The invention discloses a dual-polarization modulation optical transparent metasurface based on graphene ionic gel, and belongs to the technical field of metamaterials and electromagnetic metasurfaces. The invention discloses a dual-polarization modulation optical transparent metasurface based on graphene ionic gel. The metasurface comprises a graphene ionic gel interlayer (GIG interlayer, Graphene-Ionogs-Graphene), a PET (polyethylene terephthalate) dielectric layer, an ITO (indium tin oxide) patch and an ITO film, wherein the ITO patch and the ITO film are arranged in sequence, and the ITO patch and the ITO film are etched and printed on the PET dielectric layer. The metasurface prepared by the invention can independently and dynamically control the reflection amplitude of x polarization and the resonant frequency of y polarization, and meets the requirements of the communication multiplexing field. Due to the GIG interlayer structure of the graphene ionic gel interlayer and the preferable ionic gel electrolyte material, the external voltage required for tuning the graphene is effectively reduced, and the tuning efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterials and electromagnetic metasurfaces, and in particular to a dual-polarization modulated optically transparent metasurface based on graphene ion gel. Background Art

[0002] Polarization multiplexing technology has become a research hotspot in the field of communications because it can effectively improve communication capacity and spectrum efficiency. Based on the polarization characteristics of electromagnetic waves, electromagnetic waves with different polarization directions can be regarded as mutually orthogonal transmission channels in free space. The orthogonality ensures the independence of signal transmission, thereby supporting the parallel transmission of multiple signals in the same frequency band. This feature is of great significance for breaking through the bandwidth bottleneck of traditional communication systems and improving data transmission rates. In recent years, metasurface materials with polarization-sensitive response characteristics have provided a new technical path for the development of polarization multiplexing technology due to their unique electromagnetic control capabilities, making them show key application potential in the fields of multiplexed communications, high-density integrated photonics, etc. However, the core challenge facing the current polarization multiplexing metasurface technology is how to independently control the amplitude and frequency under different polarization waves.

[0003] At the same time, with the exponential development of wireless communication technology, electromagnetic spectrum resources are becoming increasingly crowded. As a key means to cope with complex electromagnetic environments, the research value of electromagnetic stealth technology has become increasingly prominent. Metamaterials and metasurfaces, with their artificially designed subwavelength structural units, have demonstrated excellent performance in the field of electromagnetic wave control and have become the core technology carriers for realizing electromagnetic stealth functions. Among them, graphene, as a two-dimensional carbon material with atomic-level thickness, has high optical transparency and tunable electronic properties, making it an ideal material for constructing dynamically tunable metasurfaces. However, traditional graphene sandwich structure devices mostly use ionic liquids as the gate dielectric layer. The leakage problem caused by its liquid properties not only affects the long-term stability and reliability of the device, but also restricts its engineering application in harsh environments and dynamic scenarios. Further improvement is still needed. Summary of the Invention

[0004] The present invention aims to provide a dual-polarization modulated optically transparent metasurface based on graphene ion gel to address the aforementioned problems in the background art. The metasurface prepared by the present invention can independently and dynamically control the reflection amplitude of x-polarization and the resonant frequency of y-polarization, meeting the needs of the communication multiplexing field. The GIG sandwich structure of the graphene ion gel interlayer and the preferred ion gel electrolyte material in the present invention effectively reduce the external voltage required to tune the graphene, thereby improving the tuning efficiency.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a dual-polarization modulated optically transparent metasurface based on graphene ion gel, which includes: a graphene ion gel interlayer (GIG interlayer, Graphene-Ionogels-Graphene), a PET (polyethylene terephthalate) dielectric layer, an ITO (indium tin oxide) patch etched on the PET dielectric layer, and an ITO film.

[0007] The metasurface prepared by the present invention can independently and dynamically control the reflection amplitude of x-polarization and the resonance frequency of y-polarization.

[0008] The ITO patch etched on the PET dielectric layer is used to increase the resonance.

[0009] Numerical simulations show that by varying the resistance of the patterned graphene sheet within the graphene ion gel sandwich, the present invention can vary the amplitude of the x-polarized wave from -3.9 dB to -40 dB, and the resonant frequency of the absorption spectrum of the y-polarized wave from 13.8 GHz to 8.27 GHz. This metasurface, combining ion gel with graphene, addresses the ionic liquid leakage issue of traditional graphene sandwich structures, effectively reducing the bias voltage required for graphene tuning and improving the practicality and adaptability of tunable graphene-based metasurfaces.

[0010] Preferably, the graphene ion gel interlayer includes: a top layer of PET film with patterned graphene etched on the bottom, an ion gel middle layer serving as an electrolyte, and a bottom layer of PET film with patterned graphene etched on the top; the bottom layer of PET film with patterned graphene etched on the top is in contact with the PET dielectric layer.

[0011] More preferably, the method for preparing the graphene ion gel interlayer comprises the following steps: transferring the ion gel to the surface of the bottom layer of the PET film with patterned graphene etched on the top by brushing, and then covering the top layer of the PET film with patterned graphene etched on the bottom to obtain the graphene ion gel interlayer.

[0012] Preferably, the positions of the patterned graphene on the top layer of the PET film with the patterned graphene etched on the bottom and the patterned graphene on the bottom layer of the PET film with the patterned graphene etched on the top completely correspond to and overlap with each other.

[0013] Compared with the conventional solution of using ionic liquid as the gate dielectric layer, the metasurface selection of the present invention can realize anisotropic square graphene patches and achieve dynamic modulation under different polarization waves.

[0014] Preferably, the type of ion gel in the graphene ion gel interlayer is: PolyTA ion gel.

[0015] More preferably, the preparation method of the Poly TA ion gel is: mixing lipoic acid and [EMIM][EtSO4] in a mass ratio of 1:0.8 in 1 mL of ethanol to obtain the Poly TA ion gel.

[0016] Preferably, the unit size D of the metasurface is 900 μm.

[0017] Preferably, the patterned graphene in the metasurface has the same shape, and the thickness of the metasurface is 310 μm.

[0018] Preferably, the length of the graphene ion gel interlayer is Lg=700 μm, and the width of the graphene is Wg=500 μm.

[0019] Preferably, the thickness of the PET medium layer is t=2300 μm.

[0020] Preferably, the thickness of the PET film of the ITO patch etched on the PET film is 0.125 mm, the dimensions of the ITO patch on the dielectric layer are length Li=400 μm, width Wi=300 μm, and resistance is 150Ω.

[0021] Preferably, the ITO sheet resistance of the ITO film is 5Ω.

[0022] Preferably, the ITO film is grounded instead of the metal plane.

[0023] The second technical solution of the present invention: provides a method for preparing the above-mentioned dual-polarization modulated optically transparent metasurface based on graphene ion gel, comprising the following steps: assembling together the graphene ion gel interlayer, a 2.3 mm thick PET dielectric layer, an ITO patch etched on a PET film, and an ITO film in sequence.

[0024] The present invention provides a method for controlling a dual-polarization modulated optically transparent metasurface based on graphene ion gel, comprising the following steps: using the patterned graphene in the graphene ion gel interlayer as an electrode and the ion gel as an electrolyte, applying a bias voltage to the graphene electrode, and adjusting the resistance of the graphene sheet, thereby achieving continuous control of the absorption amplitude and resonant frequency under different polarizations.

[0025] The beneficial technical effects of the present invention are as follows:

[0026] The dual-polarization modulated optically transparent metasurface based on graphene ion gel prepared by the present invention can independently and dynamically control the reflection amplitude of x-polarization and the resonance frequency of y-polarization, meeting the needs of the communication multiplexing field.

[0027] By introducing ion gel and combining it with graphene, the problem of easy leakage of ionic liquid in traditional graphene sandwich structure is effectively solved, and the stability and practicality of the metasurface are improved.

[0028] The GIG sandwich structure of graphene ion gel sandwich and the preferred ion gel electrolyte material effectively reduce the external voltage required to tune graphene and improve the tuning efficiency.

[0029] The patterned graphene (with a thickness of 50 nm) used in the present invention is a highly transparent material, which can ensure that the metasurface has good optical transparency while maintaining high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 3D schematic diagram of the dual-polarization modulated optically transparent metasurface based on graphene ion gel of the present invention;

[0032] Figure 2 This is a physical picture of the product of Example 1;

[0033] Figure 3 Schematic diagram of the preparation process of the GIG interlayer of the present invention;

[0034] Figure 4 Schematic diagram of the preparation process of the ion gel of the present invention;

[0035] Figure 5 Graph showing the tuning range of the ionic liquid-based GIG interlayer of Comparative Example 1 of the present invention at a voltage of 0.5V-4.5V;

[0036] Figure 6 Graph showing the tuning range of the GIG interlayer of Example 1 of the present invention at a voltage of 0.5V-4.5V;

[0037] Figure 7 Schematic diagram of the reflection curve of the product of Example 1 of the present invention under x-polarization;

[0038] Figure 8 Schematic diagram of the reflection curve of the product of Example 1 of the present invention under y-polarization. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0040] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. It should be noted that any details not described herein are conventional procedures in the art and are not the focus of the present invention.

[0042] The terms “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0043] The present invention provides a dual-polarization modulated optically transparent metasurface based on graphene ion gel. The metasurface comprises: a graphene ion gel interlayer (GIG interlayer, Graphene-Ionogels-Graphene), a PET (polyethylene terephthalate) dielectric layer, an ITO (indium tin oxide) patch etched on the PET dielectric layer, and an ITO film, which are arranged in sequence.

[0044] Furthermore, the graphene ion gel interlayer includes: a top layer of a PET film with patterned graphene etched on the bottom, an ion gel middle layer serving as an electrolyte, and a bottom layer of a PET film with patterned graphene etched on the top, which are arranged in sequence.

[0045] Furthermore, the type of ion gel in the graphene ion gel interlayer is: PolyTA ion gel.

[0046] Furthermore, the preparation method of the Poly TA ion gel is: mixing lipoic acid and [EMIM][EtSO4] in a mass ratio of 1:0.8 in 1 mL of ethanol to obtain the Poly TA ion gel.

[0047] Furthermore, the unit size D of the metasurface is 900 μm.

[0048] Furthermore, the patterned graphene in the metasurface has the same shape, and the thickness of the metasurface is 310 μm.

[0049] Furthermore, the length of the graphene ion gel interlayer is Lg=700 μm, and the width of the graphene is Wg=500 μm.

[0050] Furthermore, the thickness of the PET medium layer is t=2300 μm.

[0051] Furthermore, the thickness of the PET film of the ITO patch etched on the PET film is 0.125 mm, the dimensions of the ITO patch on the dielectric layer are length Li=400 μm, width Wi=300 μm, and resistance is 150Ω.

[0052] Furthermore, the ITO sheet resistance of the ITO film is 5Ω.

[0053] Furthermore, the ITO film is grounded, replacing the metal plane.

[0054] Furthermore, the thickness of the PET film used to prepare the top layer of the PET film with patterned graphene etched on the bottom is 125 μm; the thickness of the PET film used to prepare the bottom layer of the PET film with patterned graphene etched on the top is 125 μm; and the ITO film is etched on the 125 μm thick PET film.

[0055] Furthermore, the patterned graphene in the metasurface has the same shape, and the thickness of the metasurface is 310 μm.

[0056] Figure 1 This is a three-dimensional schematic diagram of the dual-polarization modulated optically transparent metasurface based on graphene ion gel of the present invention.

[0057] like Figure 1 As shown in the figure, the super surface structure unit of the present invention is composed of GIG interlayer 1, PET dielectric layer 2, ITO patch 3 etched on PET film and bottom layer non-patterned ITO film 4. The size D of the super surface unit structure is 900 μm; the length of the graphene ion gel interlayer is L g =700μm, width is W g =500μm; the thickness of the PET dielectric layer is t = 2300μm, the dielectric constant is 3.21, and the tangent loss angle is 0.002; the length of the ITO patch etched on the PET film is L i =400μm, width is W i =300μm, resistance is 150Ω; ITO film, grounded, replaces the metal plane, ITO sheet resistance is 5Ω.

[0058] The graphene samples used in the present invention were purchased from Ningbo Routan Technology Co., Ltd., PET was purchased from CITIC Insulation Plastics, and ITO was purchased from South China Xiangcheng Technology.

[0059] The raw materials used in the following examples and comparative examples of the present invention are all commercially available products.

[0060] The preparation steps not described in detail in the present invention can be carried out according to conventional processing methods in the art.

[0061] Example 1

[0062] A dual-polarization modulated optically transparent metasurface based on graphene ion gel, which consists of, from top to bottom: a GIG interlayer (graphene ion gel interlayer), a PET dielectric layer, an ITO patch etched on the PET film, and an ITO film.

[0063] The specific preparation method of the metasurface is as follows:

[0064] (1) Preparation of GIG interlayer: First, accurately weigh 1 g of natural small molecule α-lipoic acid ((±)-α-Lipoic acid, TA) and dissolve it in 1 mL of ethanol. Continuously stir to fully dissolve TA and finally obtain a uniform yellow transparent solution. Subsequently, accurately weigh 0.8 g of [EMIM][EtSO4] (1-ethyl-3-methylimidazole ethyl sulfate) and slowly drip it into the above-mentioned TA ethanol solution. Keep stirring during the addition process to promote mixing of the two. After the addition is completed, continue stirring for 5 minutes to ensure that the solution is fully mixed and forms a uniform and transparent liquid ion gel solution to obtain PolyTA ion gel.

[0065] The prepared Poly TA ion gel was evenly transferred by brushing onto a pre-cut 125 μm thick, 1800 μm wide, and 1800 μm long graphene-PET film (the graphene thickness of the graphene-PET film was 50 nm, and the preparation method was as follows: large-area graphene was synthesized on copper foil by chemical vapor deposition, and then transferred to a 125 μm PET film by thermal lamination and copper etching. The single-layer graphene was transferred twice and doped to improve the uniformity of the graphene and reduce its sheet resistance. The graphene was then patterned by laser etching. After etching, it was separated from the air and sealed with a film for storage. Conductive tape was used to stick to the upper and lower sides of the graphene for applying an external voltage) (the surface of the graphene-PET film in contact with the ion gel was the surface etched with patterned graphene). During the coating process, special care must be taken to avoid direct contact between the ion gel and the electrode surface, ensuring that the ion gel only covers the non-electrode area of the graphene-PET film (specifically, use a scraper to scrape off the ion gel that has been spin-coated on the electrode surface), thereby preventing the ion gel from potentially affecting electrode performance. After the coating is completed, another piece of graphene-PET film of the same size is placed on top of the graphene-PET film coated with the ion gel. During the coating process, the two graphene patterns must be carefully aligned to ensure that they completely overlap in space and avoid any misalignment, resulting in a GIG sandwich with an ion gel interlayer thickness of 50 μm.

[0066] (2) The PET dielectric layer, the ITO patch etched on the PET film, and the ITO film are placed under the GIG sandwich structure in sequence to assemble the metasurface. The size D of the metasurface unit structure is 900 μm; the length of the patterned graphene is L g =700μm, width is W g =500μm; the thickness of the PET dielectric layer is t = 2300μm, the dielectric constant is 3.21, and the tangent loss angle is 0.002; the length of the ITO patch etched on the PET film is L i =400μm, width is W i =300μm, resistance is 150Ω; ITO film, grounded, replaces the metal plane, ITO sheet resistance is 5Ω.

[0067] Figure 2 This is a physical picture of the product of Example 1.

[0068] Figure 3 Schematic diagram of the preparation process of the GIG interlayer of the present invention.

[0069] like Figure 3As shown, the GIG interlayer 1 in this embodiment consists of two sheets of patterned graphene etched onto 125μm-thick PET film and an ion gel serving as an electrolyte. The ion gel is applied by brushing between the two sheets of patterned graphene, forming a supercapacitor. This structure uses patterned graphene as an electrode and the ion gel as an electrolyte. Combining the high conductivity and two-dimensional properties of graphene with the mobile ions of the ion gel, it spontaneously forms a double-layer structure. The graphene electrodes adsorb counterions from the ion gel, forming an inner adsorption layer and an outer diffusion layer. An applied electric field drives the counterions to the graphene surface for orderly arrangement, while thermal motion causes some ions to diffuse outward. These two factors together regulate the double-layer thickness and interface potential. By adjusting the electric field strength or the ion gel composition, the charge transfer efficiency can be optimized, synergistically achieving high energy density and fast response under low-voltage drive. When a bias voltage is applied, the high-concentration ion region at the interface changes the graphene Fermi level, thereby regulating its conductivity.

[0070] Figure 4 Schematic diagram of the preparation process of the ion gel of the present invention.

[0071] Comparative Example 1

[0072] The only difference from step (1) of Example 1 is that the PolyTA ion gel is replaced with an equal mass of [EMIM][EtSO4] to obtain a GIG interlayer based on ionic liquid.

[0073] Figure 5 This is a diagram showing the tuning range of the ionic liquid-based GIG interlayer of Comparative Example 1 of the present invention at a voltage of 0.5V-4.5V.

[0074] like Figure 5 As shown, with the increase of voltage, S 11 As the parameters gradually increase, the reflection is enhanced, and a channel is gradually formed that allows the signal to pass relatively smoothly; when the applied bias voltage reaches 4.5V, the maximum tuning range at 9.3GHz is 5.79dB (-12.04 to -6.25dB).

[0075] Figure 6 This is a diagram showing the tuning range of the GIG interlayer of Example 1 of the present invention at a voltage of 0.5V-4.5V.

[0076] like Figure 6 As shown in the figure, with the increase of voltage, the S 11 The parameters are gradually increased, and a passband that allows the signal to pass relatively smoothly is gradually formed; when the bias voltage reaches 2V, the maximum tuning range at 9.3GHz is 7.53dB (-15.06 to -7.53dB); continue to apply the bias voltage, S 11The parameters gradually decrease, forming a stop band. When the bias voltage reaches 4.5V, the S 11 The parameter is -12.06dB.

[0077] Figure 7 Schematic diagram of the reflection curve of the product of Example 1 of the present invention under x-polarization.

[0078] Figure 8 Schematic diagram of the reflection curve of the product of Example 1 of the present invention under y-polarization.

[0079] Figure 7 、 Figure 8 This demonstrates the dynamic regulation of the absorption amplitude and resonance frequency of the metasurface of Example 1 under different polarizations. A DC voltage source is used as the power supply for graphene. By adjusting the output voltage of the DC voltage source, the bias voltage applied to the graphene is changed, thereby achieving a change in the graphene sheet group from 100Ω to 1200Ω. Figure 7 It can be seen that with the change of graphene sheet resistance, under x-polarization conditions, when a bias voltage is applied to the patterned graphene, as its sheet resistance gradually decreases, the absorption amplitude of the metasurface at a frequency of 14.2GHz gradually increases. This trend reaches a peak when the resistance drops to 900Ω (when a 1.5V bias voltage is applied), and the absorption amplitude reaches a significant depth of -40dB. This result shows that at this resistance value, the metasurface's ability to absorb electromagnetic waves of a specific frequency is greatly enhanced. However, when the sheet resistance of graphene is further reduced, the absorption amplitude begins to decrease. When a 4.5V bias voltage is applied, the absorption amplitude reaches a minimum value of -3.9dB. Under y-polarization conditions, as the resistance gradually decreases, the reflection peak of the metasurface moves from 13.8GHz to the low-frequency direction. When a bias voltage of 3.5V is applied, the reflection peak further moves to 8.27GHz. This phenomenon is Figure 8 It is clearly reflected in.

[0080] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A dual-polarization modulated optically transparent metasurface based on graphene ion gel, characterized in that: The super surface comprises: a graphene ion gel interlayer, a PET medium layer, an ITO patch etched on a PET film, and an ITO film, which are arranged in sequence.

2. The graphene ion gel-based dual-polarization modulated optically transparent metasurface according to claim 1, characterized in that: The graphene ion gel interlayer sequentially comprises: a top layer of PET film with patterned graphene etched on the bottom, an ion gel middle layer serving as an electrolyte, and a bottom layer of PET film with patterned graphene etched on the top; the bottom layer of PET film with patterned graphene etched on the top is in contact with the PET dielectric layer.

3. The graphene ion gel-based dual-polarization modulated optically transparent metasurface according to claim 2, characterized in that: The preparation method of the graphene ion gel interlayer comprises the following steps: transferring the ion gel to the surface of the bottom layer of the PET film with patterned graphene etched on the top by brushing, and then covering the top layer of the PET film with patterned graphene etched on the bottom to obtain the graphene ion gel interlayer.

4. The graphene ion gel-based dual-polarization modulated optically transparent metasurface according to claim 1, characterized in that: The type of ion gel in the graphene ion gel interlayer is Poly TA ion gel.

5. The graphene ion gel-based dual-polarization modulated optically transparent metasurface according to claim 1, characterized in that: The unit size D of the metasurface is 900 μm.

6. The graphene ion gel-based dual-polarization modulated optically transparent metasurface according to claim 1, characterized in that: The length L of the graphene ion gel interlayer g =700μm, width W g =500μm.

7. The graphene ion gel-based dual-polarization modulated optically transparent metasurface according to claim 1, characterized in that: The thickness of the PET dielectric layer is t=2300 μm; and / or the thickness of the PET film of the ITO patch printed on the PET film is 0.125 mm, and the length L of the ITO patch is i =400μm, width W i =300 μm, resistance is 150Ω; and / or, the ITO sheet resistance of the ITO film is 5Ω.

8. A method for preparing a dual-polarization modulated optically transparent metasurface based on graphene ion gel according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: sequentially assembling the graphene ion gel interlayer, a 2.3 mm thick PET medium layer, an ITO patch etched on a PET film, and an ITO film.

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