A temperature-tunable all-dielectric frequency-selective wave-transparent metamaterial

Abstract

This invention discloses a temperature-tunable all-dielectric frequency-selective transparent metamaterial, belonging to the field of artificial electromagnetic materials technology. The main body of this temperature-tunable all-dielectric frequency-selective transparent metamaterial is an all-dielectric metamaterial, which is a dielectric plate with a periodically arranged array of holes. This invention combines a dielectric material with a high dielectric constant temperature coefficient with a metamaterial to construct an all-dielectric metamaterial with frequency-selective transmission capability. Furthermore, as the temperature changes, the dielectric constant of the dielectric material changes accordingly, driving the shift of the transmission band frequency, exhibiting excellent temperature tunability.

Description

Technical Field

[0001] This invention relates to the field of artificial electromagnetic materials technology, specifically to a temperature-tunable, all-dielectric frequency-selective transparent metamaterial. Background Technology

[0002] In recent years, with the rapid development of radar and communication technologies, antenna systems, as strong scattering sources, have significant strategic importance in reducing their radar cross-section. This has spurred a series of demands, including broadband transmission, frequency-selective transmission, and electromagnetic stealth. Based on this, frequency-selective surfaces, which can achieve in-band transmission and out-of-band reflection, have been widely used. Currently, most frequency-selective surfaces are periodic array structures composed of metallic structural units. Their structure allows for adjustable passbands or stopbands, enabling the transmission of friendly signals within their band and the reflection of opposing signals outside their band, thereby achieving the goals of anti-jamming and reducing the radar cross-section. However, the deterministic structure of frequency-selective surfaces and the difficulty in tuning the electromagnetic parameters of metals result in a fixed operating frequency. Adjusting the operating frequency of such frequency-selective surfaces requires redesigning the structure and re-fabricating the corresponding physical prototype, which limits their further application.

[0003] Metamaterials are artificially constructed geometric materials with extraordinary physical properties. The unique properties of these materials primarily stem from their artificial geometry. Dielectric materials possess a rich variety of dielectric properties, and the physical properties of dielectric metamaterials constructed from these materials are determined by both their artificial geometry and the inherent characteristics of the material itself. The electromagnetic parameters of some dielectric materials are highly sensitive to external fields such as thermal, electric, and magnetic fields. Using these dielectric materials to construct metamaterials allows for real-time dynamic control of their electromagnetic properties, offering broader application prospects. Temperature-tunable properties can be achieved by understanding the temperature dependence of the material's dielectric constant. Temperature-tunable metamaterials based on vanadium dioxide and indium antimonide have attracted considerable attention; however, due to material properties, the former is difficult to tune for resonant frequencies, while the latter has low efficiency and often contains metallic components, leading to high losses and difficulty in withstanding high temperatures. Therefore, further research is needed on temperature-tunable, fully dielectric frequency-selective transparent metamaterials. Summary of the Invention

[0004] This invention provides a temperature-tunable all-dielectric frequency-selective transparent metamaterial. Based on electromagnetic resonance theory, an artificial geometric structure is designed to realize the frequency-selective transparent all-dielectric metamaterial. By selecting a dielectric material with appropriate temperature characteristics, the temperature control of the metamaterial's wave transmission frequency is achieved.

[0005] This invention first provides a temperature-tunable all-dielectric frequency-selective transparent metamaterial, the main body of which is an all-dielectric metamaterial, which is a dielectric plate with a periodically arranged array of holes.

[0006] In the aforementioned temperature-adjustable, all-dielectric frequency-selective transmissive metamaterial, the dielectric plate is made of titanium oxide, calcium titanate, strontium titanate, or calcium strontium titanate.

[0007] The temperature-adjustable all-dielectric frequency-selective transparent metamaterial is obtained by processing a periodically arranged array of holes on a whole all-dielectric material through laser processing, ceramic engraving, or high-pressure water jet cutting.

[0008] In the aforementioned temperature-tunable all-dielectric frequency-selective transparent metamaterial, the shape of the aperture is circular, square, or other polygonal.

[0009] The hole array is obtained by arranging holes as basic units in a two-dimensional dot matrix in the form of simple rhombuses, simple rectangles, central rectangles, simple squares, or simple hexagons.

[0010] The hole is a through hole that penetrates the thickness of the dielectric substrate.

[0011] The aforementioned temperature-tunable all-dielectric frequency-selective transparent metamaterial achieves frequency-selective wave transmission by controlling the coupling mode of electromagnetic resonant modes at the connection between holes through the adjustment of the hole size and the periodic parameters of the hole array.

[0012] The dielectric constant of the dielectric substrate changes with temperature. When the dielectric constant changes, the resonant frequency shifts, and consequently the transmission frequency band shifts, exhibiting temperature adjustability.

[0013] The aforementioned temperature-tunable, all-dielectric frequency-selective transparent metamaterial's structural design gives it self-supporting characteristics, allowing it to be used alone or in combination with a substrate. The substrate is made of a low-loss material; specifically, the substrate is made of silicon oxide, silicon nitride, aluminum oxide, or polymers such as PI, FR4, etc.

[0014] This invention also provides a method for preparing the above-mentioned temperature-tunable all-dielectric frequency-selective transparent metamaterial, comprising the following steps:

[0015] The all-dielectric material block is cut into sheets, and then a periodically arranged array of holes is processed on the sheets by laser processing, ceramic engraving or high-pressure water jet cutting to obtain the temperature-tunable all-dielectric frequency-selective transparent metamaterial.

[0016] The preparation method further includes laminating a substrate onto a temperature-tunable, all-dielectric frequency-selective transparent metamaterial. Specifically, the two are bonded together using a high-temperature resistant adhesive or ordinary double-sided adhesive.

[0017] In the temperature-adjustable, all-dielectric frequency-selective transparent metamaterial structure, the inter-hole connections undergo electromagnetic resonance under the action of incident electromagnetic waves. The frequency of resonance is mainly related to the size parameters and the dielectric constant: for a single dielectric component, the dielectric constant is relatively fixed, so the frequency of resonance is mainly related to the size parameters; for a given structure, the frequency of resonance can be adjusted by changing the dielectric constant.

[0018] When resonance occurs at the inter-hole connection in the temperature-adjustable all-dielectric frequency-selective transparent metamaterial structure, the resonant frequency is adjusted by designing the size parameters of the metamaterial structure. This allows different modes with the same intensity at the same frequency to superimpose on each other, resulting in enhanced transmittance at that frequency and suppressed transmittance at other nearby frequencies, i.e., frequency-selective transmission.

[0019] The frequency of electromagnetic resonance occurring in the temperature-adjustable all-dielectric frequency-selective transmissive metamaterial exhibits a negative correlation with the dielectric constant of the dielectric material constituting the metamaterial. When the dielectric constant changes, the resonant frequency shifts accordingly, and consequently, the transmissive frequency band shifts, demonstrating temperature adjustability.

[0020] The temperature tunability of the temperature-tunable, all-dielectric frequency-selective transmissive metamaterial is mainly related to the selection of the dielectric material. Different dielectric materials exhibit different changes in their dielectric constant with temperature variations, which can be characterized by the temperature drift coefficient (hereinafter referred to as the temperature drift coefficient). A large absolute value of the temperature drift coefficient means a large change in the dielectric constant with temperature; a small absolute value means a small change in the dielectric constant with temperature. In other words, by selecting dielectric materials with different temperature drift coefficients, the temperature sensitivity of the metamaterial's transmission frequency can be controlled to adapt to different working environments. When the composition is ceramics with large absolute values ​​of temperature drift coefficient, such as strontium titanate, calcium titanate, or calcium strontium titanate, the metamaterial fabricated based on these materials has a strong temperature sensitivity in its transmission frequency, requiring only a small temperature range to achieve a large frequency tuning bandwidth. Conversely, when the composition is ceramics with small absolute values ​​of temperature drift coefficient, such as titanium oxide, the transmission frequency of the metamaterial fabricated based on these materials is less sensitive to temperature, requiring a larger temperature range to achieve the same frequency tuning bandwidth.

[0021] The structural design of the temperature-tunable, all-dielectric frequency-selective transparent metamaterial gives it a self-supporting characteristic, allowing it to be used alone or in combination with a substrate.

[0022] The temperature-tunable, all-dielectric frequency-selective transparent metamaterial utilizes a temperature variation source that can be adjusted appropriately based on the operating environment. When the ambient temperature is stable, an active temperature variation source can be set to actively adjust the temperature, thereby achieving the desired frequency-selective transmission function. When the ambient temperature is fluctuating, its trend can be utilized. By understanding the variation pattern, this condition can be incorporated into the metamaterial's design process, thus enabling it to exhibit corresponding frequency-selective transmission performance under different environmental conditions. Furthermore, both approaches can be combined to achieve precise temperature control, ensuring the metamaterial operates in an ideal state.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The metamaterial of the present invention is composed entirely of dielectric materials. Compared with similar functional metamaterials containing metals, it has a simpler structure, better high-temperature resistance and chemical corrosion resistance, and lower loss.

[0025] (2) The metamaterial structure of the present invention is self-supporting and can be used alone or in combination with a substrate to achieve higher mechanical properties to adapt to different working environments.

[0026] (3) The sensitivity of the metamaterial frequency tuning bandwidth of the present invention to temperature can be flexibly controlled by changing the composition of the dielectric material;

[0027] (4) The transmission band of the metamaterial of the present invention can be adjusted within a wide range by adjusting the size parameters of the structure. Compared with ordinary dielectric plates with fixed transmission peaks, it can better meet the requirements of different environments for transmission frequency bands.

[0028] (5) The temperature change source used to achieve temperature adjustability in this invention can be appropriately adjusted according to the working environment, mainly in three ways: active, passive, and a combination of active and passive.

[0029] (6) The metamaterial of the present invention has a simple structure, low processing difficulty, and is easy to prepare. It can be obtained by various processing methods such as laser processing, ceramic carving, and high-pressure water jet cutting. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the three-dimensional structure of the metamaterial in Example 1.

[0031] Figure 2 This is a schematic diagram of the structure of one unit of the metamaterial in Example 1.

[0032] Figure 3 The image shows the wave transmission curves of the metamaterial in Example 1 at different temperatures.

[0033] Figure 4 This is a schematic diagram of the three-dimensional structure of the metamaterial in Example 2.

[0034] Figure 5 This is a side view of the structure of one unit of the metamaterial in Example 2.

[0035] Figure 6 This is a schematic diagram of the structure of one unit of the metamaterial in Example 2.

[0036] Figure 7 The image shows the wave transmission curves of the metamaterial in Example 2 at different temperatures.

[0037] Figure 8 The image shows the wave transmission curves of the metamaterial in Example 3 at different temperatures. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0039] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0040] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0041] The data in the following embodiments were obtained by electromagnetic simulation using software in the art.

[0042] Example 1

[0043] Figure 1 and Figure 2 These are schematic diagrams of the metamaterial of the present invention and a schematic diagram of a single structure, respectively. Figure 2 In this diagram, d is the diameter of the circular hole, p is the period of the circular hole array, and h is the thickness of the sheet.

[0044] The method for preparing the metamaterial in this embodiment includes the following steps:

[0045] S1. Cut the strontium titanate ceramic block into 1.3mm thick sheets using an internal circular cutter.

[0046] S2. Take the above-mentioned sheet material with a thickness of 1.3mm (strontium titanate, real part of dielectric constant is 295, loss tangent is about 0.0027), and process a circular hole array on it by means of laser processing, ceramic engraving, high-pressure water jet cutting, etc. (in this embodiment, ceramic engraving is specifically used). The period of the circular hole array is 4.8mm, and the diameter of the circular hole is 4mm.

[0047] The metamaterial prepared above exhibits electromagnetic resonance at room temperature when the incident electromagnetic wave frequency is around 8.07 GHz, leading to enhanced transmission. As the temperature gradually increases, the dielectric constant of strontium titanate gradually decreases, and the frequency of electromagnetic resonance shifts accordingly.

[0048] Figure 3 Electromagnetic parameter curves of the metamaterial prepared for this embodiment at different temperatures. Figure 3 It can be seen that at room temperature, the frequency band with transmittance above 0.8 is 7.97–8.13 GHz, with a peak value of 0.992; at 50°C, the frequency band with transmittance above 0.8 is 8.19–8.34 GHz, with a peak value of 0.990; at 100°C, the frequency band with transmittance above 0.8 is 8.53–8.68 GHz, with a peak value of 0.982; at 150°C, the frequency band with transmittance above 0.8 is 8.94–9.10 GHz, with a peak value of 0.963; and at 200°C, the frequency band with transmittance above 0.8 is 9.36–9.53 GHz, with a peak value of 0.945. It can be observed that the bandwidth maintaining transmittance above 0.8 is consistently greater than 130 MHz, and the tunable bandwidth reaches 1.4 GHz from room temperature to 200°C.

[0049] Example 2

[0050] Based on Example 1, a substrate is added so that the metamaterial can be used in conjunction with the substrate. Figures 4-6 These are schematic diagrams of metamaterials used in conjunction with substrates, and side views and schematic diagrams of individual structures. Figure 5 In the diagram, 1 represents the metamaterial, and 2 represents the substrate. Figure 6 In this diagram, d is the diameter of the circular hole, p is the period of the circular hole array, h is the thickness of the sheet, and t is the thickness of the substrate.

[0051] The method for preparing the metamaterial in this embodiment includes the following steps:

[0052] S1. Take a 9mm thick quartz glass (real part of dielectric constant is 4, loss tangent is about 0.0004) as the substrate.

[0053] S2. Take a 1.3mm thick strontium titanate sheet (prepared in the same way as in Example 1, with a real part of dielectric constant of 295 and a loss tangent of about 0.001), and process a circular hole array on it by means of laser processing, ceramic engraving, high-pressure water jet cutting, etc. (in this example, ceramic engraving is specifically used). The period of the circular hole array is 4.8mm, and the diameter of the circular hole is 4mm.

[0054] S3. Combine the substrate in S1 with the metamaterial in S2 using methods such as bonding with high-temperature resistant adhesive.

[0055] Specifically, a high-temperature resistant adhesive is applied to the substrate, the metamaterial and the substrate are bonded together, cured at room temperature for 2 hours, then heated to 100°C for 2 hours, and then slowly cooled.

[0056] The metamaterial prepared above exhibits electromagnetic resonance at room temperature when the incident electromagnetic wave frequency is around 8.07 GHz, leading to enhanced transmission. As the temperature gradually increases, the dielectric constant of strontium titanate gradually decreases, and the frequency of electromagnetic resonance shifts accordingly.

[0057] Figure 7 The figures show the electromagnetic parameter curves of the metamaterial in this embodiment at different temperatures. Figure 7 It can be seen that at room temperature, the frequency band with transmittance above 0.8 is 7.98–8.12 GHz, with a peak value of 0.983; at 50℃, the frequency band with transmittance above 0.8 is 8.18–8.33 GHz, with a peak value of 0.989; at 100℃, the frequency band with transmittance above 0.8 is 8.51–8.67 GHz, with a peak value of 0.992; at 150℃, the frequency band with transmittance above 0.8 is 8.88–9.07 GHz, with a peak value of 0.976; and at 200℃, the frequency band with transmittance above 0.8 is 9.29–9.48 GHz, with a peak value of 0.925. It can be observed that the bandwidth maintaining transmittance above 0.8 is consistently greater than 120 MHz, and the tunable bandwidth reaches 1.3 GHz from room temperature to 200℃.

[0058] Compared to Example 1, after adding a substrate, the transmission peak width only narrowed slightly, while the peak intensity and position remained very stable and essentially unchanged. Furthermore, the tunable bandwidth decreased by only 0.1 GHz, approximately 7%, from room temperature to 200°C. This comparison demonstrates that adding a substrate does not affect the wave transmission performance of the metamaterial.

[0059] Example 3

[0060] Based on Example 2, the material of the metamaterial was changed and the dimensional parameters were adjusted.

[0061] The schematic diagram and fabrication process of the metamaterial structure in this embodiment are similar to those in Embodiment 2, but the dimensional parameters are different. The specific fabrication steps are as follows:

[0062] S1. Take a 9mm thick quartz glass (real part of dielectric constant is 4, loss tangent is about 0.0004) as the substrate.

[0063] S2. Take a titanium oxide with a thickness of 2.2mm (real part of dielectric constant is 100, loss tangent is about 0.001), and process a circular hole array on it by means of laser processing, ceramic engraving, high-pressure water jet cutting, etc. (in this embodiment, ceramic engraving is specifically used). The period of the circular hole array is 9.4mm, and the diameter of the circular hole is 6.8mm.

[0064] S3. Combine the substrate in S1 with the metamaterial in S2 using methods such as bonding with high-temperature resistant adhesive.

[0065] Specifically, a high-temperature resistant adhesive is applied to the substrate, the metamaterial and the substrate are bonded together, cured at room temperature for 2 hours, then heated to 100°C for 2 hours, and then slowly cooled.

[0066] The metamaterial prepared above exhibits electromagnetic resonance at room temperature when the incident electromagnetic wave frequency is around 8.19 GHz, leading to enhanced transmission. As the temperature gradually increases, the dielectric constant of titanium oxide gradually decreases, and the frequency of electromagnetic resonance shifts accordingly.

[0067] Figure 8 The figures show the electromagnetic parameter curves of the metamaterial in this embodiment at different temperatures. Figure 8 It can be seen that at room temperature, the frequency band with transmittance above 0.8 is 8.09–8.25 GHz, with a peak value of 0.929; at 100℃, the frequency band with transmittance above 0.8 is 8.37–8.55 GHz, with a peak value of 0.937; at 200℃, the frequency band with transmittance above 0.8 is 8.76–8.96 GHz, with a peak value of 0.900; and at 300℃, the frequency band with transmittance above 0.8 is 9.18–9.37 GHz, with a peak value of 0.860. It can be observed that the bandwidth maintaining transmittance above 0.8 is consistently greater than 160 MHz, and the tunable bandwidth reaches 1.1 GHz from room temperature to 300℃.

[0068] Compared to Example 2, the transmission peak width is slightly broadened after using materials with relatively smaller absolute values ​​of dielectric constant and dielectric constant temperature drift coefficient. Simultaneously, the temperature span required to achieve the corresponding tunable bandwidth increases. In Example 2, a tunable bandwidth of 1.3 GHz requires a temperature span of 180°C, while in Example 3, a tunable bandwidth of only 1.1 GHz requires a temperature span of 280°C. This comparison shows that the temperature tunability of the metamaterial of this invention is related to the selection of the dielectric material. By selecting dielectric materials with different temperature drift coefficients, the temperature sensitivity of the metamaterial's transmission frequency can be controlled to adapt to different application requirements.

[0069] The structure of the wave-transparent metamaterial in this invention is not limited to this; it can also be designed as a square hole, triangular hole, or other structure. The substrate is made of a low-loss material, such as silicon oxide, silicon nitride, aluminum oxide, or polymers such as PI and FR4.

Claims

1. A temperature-tunable, all-dielectric frequency-selective transparent metamaterial, characterized in that: Its main body is a metamaterial that is entirely dielectric, which is a dielectric plate with a periodically arranged array of holes processed on a whole piece of dielectric material; wherein the metamaterial that is entirely dielectric means that the metamaterial is composed entirely of dielectric material, and the holes are through holes that penetrate the thickness of the dielectric plate. The dielectric plate is made of titanium oxide, calcium titanate, strontium titanate, or calcium strontium titanate, wherein the temperature-adjustable all-dielectric frequency-selective transmissive metamaterial has self-supporting characteristics. By adjusting the size of the holes and the periodic parameters of the hole array, the coupling mode of the electromagnetic resonant mode at the connection between the holes can be controlled, thereby achieving frequency-selective wave transmission function. The dielectric constant of the dielectric substrate changes with temperature. When the dielectric constant changes, the resonant frequency shifts accordingly, and the transmission frequency band shifts, exhibiting temperature adjustability.

2. The temperature-tunable, all-dielectric frequency-selective transparent metamaterial according to claim 1, characterized in that: The temperature-adjustable all-dielectric frequency-selective transparent metamaterial is obtained by processing a periodically arranged array of holes on a whole all-dielectric material through laser processing, ceramic engraving, or high-pressure water jet cutting.

3. The temperature-tunable, all-dielectric frequency-selective transparent metamaterial according to claim 1 or 2, characterized in that: The shape of the hole is circular, square, or other polygonal; The hole array is obtained by arranging holes as basic units in a simple rhombus, simple rectangle, central rectangle, simple square or simple hexagonal pattern in a two-dimensional dot matrix.

4. The temperature-tunable, all-dielectric frequency-selective transparent metamaterial according to claim 1 or 2, characterized in that: The temperature-tunable, all-dielectric frequency-selective transmissive metamaterial can be used alone or in combination with a substrate. The substrate is made of a low-loss material.

5. The temperature-tunable, all-dielectric frequency-selective transparent metamaterial according to claim 4, characterized in that: The substrate is made of silicon oxide, silicon nitride, aluminum oxide, or a polymer.

6. A method for preparing the temperature-tunable, all-dielectric frequency-selective transparent metamaterial according to any one of claims 1-3, comprising the following steps: The all-dielectric material block is cut into sheets, and then a periodically arranged array of holes is processed on the sheets by laser processing, ceramic engraving or high-pressure water jet cutting to obtain the temperature-tunable all-dielectric frequency-selective transparent metamaterial.

7. The preparation method according to claim 6, characterized in that: The preparation method also includes composited with a substrate on a temperature-tunable, all-dielectric frequency-selective transparent metamaterial.

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