Graphene-based multiple narrow-band metamaterial absorber

Abstract

The invention discloses a graphene-based multi-narrow-band metamaterial absorber, and aims to solve the problem that the absorption performance of an existing multi-narrow-band metamaterial absorber cannot meet the actual requirements. In the aspect of structural design, the device adopts a six-layer heterogeneous composite structure which comprises a metal pattern layer, a graphene pattern layer, a first dielectric layer, a metal enhancement layer, a second dielectric layer and a metal bottom layer from top to bottom. The narrow-band absorption behavior from double peaks, three peaks to four peaks is realized in the working frequency range of 0.5-1.3 THz, and the absorption intensity of all absorption peaks is improved to more than 90%. A reliable structural scheme is provided for the design of the high-performance multi-narrow-band metamaterial absorber, the absorption efficiency is remarkably improved, and the high-performance multi-narrow-band metamaterial absorber has important application value in the fields of terahertz communication, radar stealth and the like.

Description

Technical Field

[0001] This invention belongs to the field of terahertz electromagnetic wave absorption device design, specifically relating to a graphene-based multiple narrowband metamaterial absorber. Background Technology

[0002] With the rapid development of information technology, the importance of the terahertz spectrum region is becoming increasingly prominent, especially in key fields such as high-speed wireless communication and deep space exploration. The unique properties of terahertz waves, such as high frequency and short wavelength, endow them with significant potential in scientific and engineering applications.

[0003] Currently, breakthroughs have been achieved in high-speed wireless communication and deep space exploration, making the precise control of electromagnetic waves in the 0.5-1.3 THz band increasingly urgent. However, the high-frequency characteristics of this band make it highly susceptible to changes in the internal structure of materials, leading to unexpected energy losses. Existing absorbers generally face two major bottlenecks: First, traditional sandwich structures can only achieve single-peak or double-peak absorption, which cannot meet the complex requirements of multi-band collaborative operation, such as the need to suppress multiple interference frequencies simultaneously in 6G communication systems. Second, parameter coupling effects are significant during structural adjustments; optimizing a certain absorption peak often results in the attenuation of other peak intensities, limiting the practicality of devices in scenarios such as radar stealth. These technical limitations not only reduce the efficiency of electromagnetic environment management but also hinder the in-depth application of terahertz technology in fields such as medical imaging and security sensing.

[0004] In response to the above challenges, it is imperative to develop metamaterial devices with multiple independent narrowband absorption capabilities. Summary of the Invention

[0005] The purpose of this invention is to provide an adjustable broadband terahertz metamaterial absorber to solve the problems of narrow operating frequency band, low absorption efficiency and limited control methods in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On one hand, the present invention provides a graphene-based multiple narrowband metamaterial absorber, comprising a six-layer structure from top to bottom: a metal patterned layer, a graphene patterned layer, a first dielectric layer, a metal reinforcement layer, a second dielectric layer, and a bottom metal layer;

[0008] The metal patterned layer employs a hexagonal configuration composed of six equilateral triangles, with small rectangles embedded at the four corners and thin strips added along the diagonal gaps. The graphene layer is designed as a pair of hexagonal stripes at the corners. The metal reinforcement layer uses large rectangles arranged at the four corners. The first and second dielectric layers are both rectangular structures of the same size. This hierarchical design enables the device to stably generate multiple independent absorption peaks in the 0.5-1.3 THz frequency band.

[0009] The preferred embodiment is that the metal pattern layer is made of gold; the graphene pattern layer is a single layer of graphene; the first dielectric layer and the second dielectric layer are both made of silicon dioxide; the metal reinforcement layer is made of gold; and the bottom metal layer is made of aluminum.

[0010] A preferred embodiment is that the bottom metal layer is an aluminum plate that matches the overall device structure.

[0011] The preferred embodiment is that the side length of the six equilateral triangles of the metal pattern layer is l1=64 μm, the width of the rectangular strip is r / 2=5.5 μm, and the side length of the corner rectangle is r=11 μm.

[0012] The preferred embodiment is that the side length of the regular hexagon in the graphene pattern layer is l2 = 52.8 μm.

[0013] The preferred embodiment is that the side length of the large rectangle of the metal pattern layer is l3=95.5 μm; the side length of the entire absorption device is l4=217 μm; and the thickness of the metal pattern layer is h1=0.8 μm.

[0014] The preferred embodiment is that the thickness of the first dielectric layer and the second dielectric layer is h2=30 μm each; the thickness of the single-layer graphene layer is 0.34 nm; and the thickness of the bottom metal layer is h4=1 μm.

[0015] The beneficial effects of this invention are:

[0016] (1) Through the synergistic effect of the six-layer heterogeneous composite structure, two to four high-intensity independent absorption peaks can be accurately generated in the 0.5-1.3 THz frequency band.

[0017] (2) By optimizing the equipment structure parameters, the absorption intensity is significantly improved to reach 90% or even more than 90%, which meets the actual application requirements.

[0018] (3) It adopts a multi-layer composite structure, which is simple and easy to manufacture, effectively reducing manufacturing costs and improving product competitiveness.

[0019] (4) It can be applied to fields such as communication, radar, and remote sensing to achieve efficient absorption of multiple narrowband electromagnetic waves, such as multi-band wireless communication systems, stealth technology, and target imaging, and has broad application prospects. Attached Figure Description

[0020] Figure 1 Two key challenges in the design and optimization of multiple narrowband metamaterial absorbers: performance tuning and comprehensive optimization.

[0021] Figure 2 Structural design for graphene-based multiple narrowband metamaterial absorbers;

[0022] Figure 3 For the machine learning and data analysis process and the detailed steps for implementing machine learning;

[0023] Figure 4 A detailed flowchart illustrating how machine learning guides device size parameters to enhance device absorption characteristics;

[0024] Figure 5 To compare the absorption characteristics of the four-layer basic structures in Examples 1 and 2 before and after structural and parameter optimization in the range of 0.5-1.3 THz, and the electric field loss distribution of the two structural devices at 1.23 THz;

[0025] Figure 6 To comprehensively optimize the number of absorption peaks and the absorption rate of graphene-based multiple narrowband metamaterial absorbers with three and four absorption peaks;

[0026] Figure 7 The fabrication process of each layer of the device includes operations such as graphene transfer, laser ablation, and magnetron sputtering of metal materials combined with a mask;

[0027] Figure 8 A comparison of the absorption characteristics and electric field loss distribution of six-layer devices with and without graphene layers.

[0028] Figure 9 This is a weighted radar plot showing the impact of different size parameters on the absorption performance of a device within a specific operating frequency band. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] like Figure 1 This invention discloses a graphene-based multiple narrowband metamaterial absorber for the 0.5-1.3 THz frequency band, with the specific steps as follows:

[0032] The first step is to design a four-layer structure device from top to bottom: a metal pattern layer, a graphene pattern layer, a silicon dioxide dielectric layer, and a bottom metal layer.

[0033] The second step is to perform a parameter scan on the dimensions of this four-layer device to obtain a preliminary correspondence between its parameters and absorption characteristic curves.

[0034] The third step is to design a six-layer structure device from top to bottom: a metal pattern layer, a graphene pattern layer, a first dielectric layer, a metal reinforcement layer, a second dielectric layer, and a bottom metal layer.

[0035] The fourth step is to save the results obtained from the parameter scan and provide them to the XGBoost machine learning algorithm. After learning, the fitting model will predict the relevant parameters of the target curve.

[0036] Figure 1 This paper clearly outlines two key challenges in the design and optimization of multiple narrowband absorbers. While achieving a fixed number of absorption peaks within a specific frequency band is not difficult for metamaterial absorbers with multiple narrowband absorbers, the precise tuning of two, three, or even four absorption peaks within a specific frequency band is challenging due to the significant influence of interactions between sublayers on their absorption performance and behavior. This lack of flexibility in absorption behavior tuning has become one of the main challenges in device optimization. Another challenge is how to comprehensively optimize and control the absorption behavior of multiple narrowband absorbers within a specific frequency band. This is because the internal structural parameters of the device have a comprehensive impact on its performance. When adjusting structural parameters to optimize the performance of one absorption peak, the intensity of other absorption peaks may decrease, resulting in a trade-off.

[0037] Figure 2 Various structural designs of graphene-based multi-narrowband metamaterial absorbers are shown. (a) is a four-layer basic structure with one rectangular strip in Comparative Example 1; (b) is a four-layer basic structure with three intersecting rectangular strips in Comparative Example 2; (c) is a top view of the designed six-layer structure absorber; (d) is a four-layer basic structure in Comparative Examples 1 and 2, consisting of a metal pattern layer, a graphene pattern layer, a dielectric layer, and a bottom metal layer from top to bottom; (e) is the arrangement of the six-layer structure from top to bottom; (f) is the graphene layer pattern common to both the four-layer and six-layer structures; (g) is the pattern of the metal reinforcement layer in the six-layer structure device.

[0038] Figure 3 (a) describes the workflow for applying machine learning techniques to the design and optimization of graphene-based composite materials. This process includes scanning device model parameters, isometric sampling of wave absorption characteristic curves, and constructing a regression model of the relationship between these parameters and absorption performance. (b) outlines the implementation steps of the machine learning process. Initially, the model building phase involves reading and processing the training and test datasets, including feature extraction and label assignment. The regression model is trained using the training dataset, and then validated using the test dataset, calculating the mean squared error (MSE) to evaluate the model's accuracy. Based on this, positive predictions are made regarding the impact of different size parameters on wave absorption performance at different operating frequencies. Finally, backpropagation is performed to determine the optimal configuration of device size parameters to meet the desired target performance.

[0039] Figure 4 This is a detailed flowchart of machine learning guiding the learning of device size parameters and enhancing device wave absorption characteristics. It includes: selection of test and training sets, training of the decision tree, model validity testing, prediction of device size parameters, and secondary optimization of feature columns.

[0040] Figure 5 (a) shows the absorption characteristics before and after optimization of the four-layer basic structure pattern in the comparative example. The orange curve represents the absorption characteristics obtained from the simulation of the four-layer basic structure with one rectangular strip in Comparative Example 1. This curve has two absorption peaks in the range of 0.4-1.3 THz, with a maximum absorption rate of 40%. The blue curve represents the absorption characteristics of the basic structure with three intersecting rectangular strips in Comparative Example 2 after a sweep scan, showing good performance. The number of absorption peaks remains unchanged, but the absorption rate of the optimized basic structure is significantly improved. The absorption rate reaches 70% near 0.68 THz and exceeds 90% near 1.23 THz. Figure 5 (b) It can be seen that the electric field loss of the four-layer basic structure with a rectangular strip is mainly concentrated on the periphery of the metal notch hexagonal pattern and the gaps between the metal triangles. Figure 5 (c) reflects the electric field loss distribution of the basic structure with three intersecting rectangular strips. In addition to the high electric field loss intensity around the metal region, the left and right sides of the device also show a high electric field loss intensity.

[0041] Figure 6 The study details the characteristics of the designed six-layer metamaterial absorber, which generates multiple narrowband absorption peaks. By using machine learning to predict and guide various parameters of the device, the study achieved optimal absorption rates of over 90% for both the three and four absorption peaks.

[0042] Figure 7 This demonstrates our fabrication method for a designed six-layer metamaterial device. First, using a silicon dioxide substrate, a graphene layer is transferred via wet processing and patterned using laser etching. Then, a metal pattern is deposited on the surface using magnetron sputtering with a metal mask. Next, another silicon dioxide wafer undergoes a similar process, with an aluminum layer sputtered on one side and a metal reinforcement layer deposited on the other. Finally, the two substrates are precisely coupled to form the target six-layer structure device.

[0043] Figure 8 (a) shows the absorption characteristics of a six-layer structure device with four good absorption peaks without a graphene layer. The distribution of absorption peaks is disordered, the intensity of each absorption peak is uneven, and the overall peak intensity is low. Figure 8 (b) The electric field loss distribution of this structure at the highest absorption rate, with high electric field loss mainly occurring at the metal gaps. Figure 8 (c) The absorption characteristics of the original six-layer structure with graphene layer are depicted. The number and morphology of the absorption peaks are significantly improved, and the absorption rate of the absorption peaks all exceed 90%. Figure 8 (d) This is the electric field loss distribution of the structure at the highest absorption rate, and the electric field loss area is significantly expanded.

[0044] Figure 9 This is a weighted radar chart showing the impact of different size parameters on the absorption performance of a device within a specific operating frequency band. The weighting of various size parameters across different frequency ranges is crucial for clarifying their relative importance. By selectively adjusting parameters with higher weightings within a specific frequency band, the absorption performance of the device can be optimized relatively easily.

[0045] Comparative Example 1

[0046] This comparative example uses a metamaterial absorber with a single rectangular strip structure as an example. This four-layer structure is based on a six-layer structure, with one metal reinforcement layer and one dielectric layer removed, and the small rectangles at the four corners of the outermost gold layer pattern deleted. At this point, both the outermost and graphene layers contain only a single horizontal rectangular strip, which is the structure of the four-layer absorber. This structure can produce two absorption peaks within the operating frequency range, but these peaks are not sharp, and the absorption rate is not high, with the maximum value barely reaching 40%.

[0047] Comparative Example 2

[0048] This comparative example uses a metamaterial absorber with three intersecting rectangular stripes as an example. Except for variations in the number of rectangular stripes in the outermost and graphene layers, the device structure is identical to Comparative Example 1. After parameter scanning, two absorption peaks with higher sharpness and absorption rate were obtained. Therefore, it can be preliminarily inferred that a device with a four-layer basic structure can have a maximum of two absorption peaks in the operating range of 0.5–1.3 THz.

[0049] Comparative Example 3

[0050] This comparative example uses a terahertz broadband absorber based on a bilayer hexagonal graphene structure designed recently by Maixia Fu et al., whose simulation results show excellent absorption characteristics. The bilayer hexagonal graphene structure is indeed placed on top of two dielectric layers, and finally on top of a metal substrate, forming a compact stacked structure. Simulation results show that under normal incident light, this absorber exhibits an absorption rate exceeding 99% in the 2.31-3.92 THz range, with an absorption bandwidth as high as 2.54 THz (1.91-4.45 THz), and a relative bandwidth of 80%. Although both this device and the device of this invention are composite device structures with graphene layers, their absorption performance characteristics differ. The former achieves broadband absorption due to the plasmon resonance coupling of the bilayer graphene, which reduces the imaginary part of the equivalent impedance. The latter, however, achieves ultra-high intensity absorption in multiple narrow bands within the operating frequency range.

[0051] Comparative Example 4

[0052] This comparative example is based on a narrowband terahertz absorber design using miniaturized units, recently designed by Amir Ebrahimi et al. [3] In contrast, the five-layer structure of the metal device in this article features a four-rectangular structure in the middle layer, forming a square patch array that plays a crucial role in increasing the capacitive load. Although both this device and the device in this invention have a similar structure with four large rectangles as the middle layer, their absorption performance characteristics differ. Simulation results show that the former absorber has an absorption rate exceeding 90% near the 0.5 THz center frequency, with only one absorption peak. The latter, however, successfully generates three and four absorption peaks through this structure, thus achieving multiple narrowband absorption characteristics.

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

Claims

1. A graphene-based multiple narrowband metamaterial absorber, characterized in that, It consists of a six-layer structure from top to bottom: a metal patterned layer, a graphene patterned layer, a first dielectric layer, a metal reinforcement layer, a second dielectric layer, and a bottom metal layer; The metal pattern layer uses a hexagonal structure composed of six equilateral triangles, with small rectangles embedded at the four corners and thin strips added to the diagonal gaps; the graphene layer is designed as a regular hexagon with paired corner strips; the metal reinforcement layer uses large rectangles arranged at the four corners; the first dielectric layer and the second dielectric layer are both rectangular structures of the same size.

2. The graphene-based multiple narrowband metamaterial absorber as described in claim 1, characterized in that, The metal pattern layer is made of gold; the graphene pattern layer is a single layer of graphene; the first dielectric layer and the second dielectric layer are both made of silicon dioxide; the metal reinforcement layer is made of gold; and the bottom metal layer is made of aluminum.

3. The graphene-based multiple narrowband metamaterial absorber as described in claim 2, characterized in that, The bottom metal layer is an aluminum plate that matches the overall device structure.

4. The graphene-based multiple narrowband metamaterial absorber as described in claim 1, characterized in that, The six equilateral triangles of the metal pattern layer have a side length of l1=64 μm, the width of the rectangular strips is r / 2=5.5 μm, and the side length of the corner rectangles is r=11 μm.

5. The graphene-based multiple narrowband metamaterial absorber as described in claim 4, characterized in that, The side length of the regular hexagon in the graphene patterned layer is l2 = 52.8 μm.

6. The graphene-based multiple narrowband metamaterial absorber as described in claim 5, characterized in that, The side length of the large rectangle of the metal patterned layer is l3 = 95.5 μm; the side length of the entire absorption device is l4 = 217 μm; and the thickness of the metal patterned layer is h1 = 0.8 μm.

7. The graphene-based multiple narrowband metamaterial absorber as described in claim 6, characterized in that, The thickness of the first dielectric layer and the second dielectric layer is h2=30 μm; the thickness of the single-layer graphene layer is 0.34 nm; and the thickness of the bottom metal layer is h4=1 μm.

8. The application of the graphene-based multiple narrowband metamaterial absorber as described in any one of claims 1-7 in the fields of communication, radar, and remote sensing.

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