Broadband terahertz wave absorber based on multilayer stacking of cross-like structures

Abstract

The application discloses a broadband terahertz wave absorber based on a multi-layer superposition of a cross-like structure, relates to the field of terahertz wave absorbers, and solves the problem of poor absorption effect of the absorber in a wide frequency band.The technical scheme is as follows: from bottom to top, a ground layer, a first dielectric layer, a first cross-like structure layer, a second dielectric layer, a rectangular long strip layer, a third dielectric layer and a second cross-like structure layer are sequentially arranged; wherein, the first cross-like structure layer and the second cross-like structure layer are both composed of two identical ellipses that are 90 DEG superimposed and have a part removed from the superimposed ellipses.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of terahertz wave absorbers, more particularly, it relates to a broadband terahertz wave absorber based on a multi-layer superposition of cross-like structures. BACKGROUND

[0002] The terahertz wave absorber is a kind of passive device with directivity, which plays an important role in various terahertz circuit systems. At present, the materials used in the design of terahertz super surface absorption structure include metal materials, graphene and nanomaterials. Graphene material has the characteristics of high preparation cost, and the preparation technology of nanomaterials for terahertz wave absorbers is not perfect. The selected gold metal material has good absorption characteristics and stable properties, and its cost is relatively low.

[0003] At present, the absorber based on the super material structure mainly works in the microwave band, and the research in the terahertz frequency band is relatively less. Designing a broadband absorber with simple structure, high absorption bandwidth and easy tuning has become a hot spot in the field of terahertz functional device research. Under this condition, the designed terahertz broadband absorber structure is composed of a multi-layer structure superposition, which has the characteristics of high absorption bandwidth in the frequency band, high absorption rate and adjustable absorption frequency band. However, the existing technology has the following disadvantages: in the terahertz frequency band, the designed single-layer absorber structure has high absorption rate, but the high absorption rate is generally good only in a very narrow frequency band, and the absorption effect in the wide frequency band is poor. SUMMARY

[0004] The purpose of the present application is to provide a broadband terahertz wave absorber based on a multi-layer superposition of cross-like structures, which solves the problem of poor absorption effect of the absorber in the wide frequency band.

[0005] The above technical purpose of the present application is realized by the following technical scheme:

[0006] The present application provides a broadband terahertz wave absorber based on a multi-layer superposition of cross-like structures, which comprises, from bottom to top, a ground layer, a first dielectric layer, a first cross-like structure layer, a second dielectric, a rectangular long strip layer, a third dielectric layer and a second cross-like structure layer; wherein the first cross-like structure layer and the second cross-like structure layer are both composed of two identical ellipses superimposed at 90° and the part of the ellipse superimposition is removed.

[0007] In one possible implementation, the first cross-like structure layer, the rectangular long strip layer and the second cross-like structure layer all use gold with electrical conductivity σ = 4.56 x 10 7 S / m.

[0008] In one possible implementation, the thickness of the first cross-like structure layer, the rectangular long strip layer and the second cross-like structure layer is 200 nanometers.

[0009] In a possible implementation, the long axis length of the ellipse constituting the first type of cross-shaped structure layer and the second type of cross-shaped structure layer is 14 microns and 12 microns respectively, and the short axis length is 7 microns and 6 microns respectively.

[0010] In a possible implementation, the width of the rectangular long strip layer along the long axis direction of the ellipse is 12.3 microns, and the size in the z-axis direction is 0.625 microns.

[0011] In a possible implementation, the size of the first dielectric layer in the z-axis direction is 2.3 microns.

[0012] In a possible implementation, the size of the second dielectric layer in the z-axis direction is 2.2 microns.

[0013] In a possible implementation, the size of the third dielectric layer in the z-axis direction is 2.8 microns.

[0014] In a possible implementation, the size of the first dielectric layer, the second dielectric layer and the third dielectric layer in the x-axis direction and the y-axis direction is equal, and is 30 microns.

[0015] In a possible implementation, the size of the ground layer in the x-axis direction and the y-axis direction is equal, and is 30 microns.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] The wideband terahertz wave absorber based on the multi-layer superposition of cross-shaped structure provided by the present application comprises, from bottom to top, a ground layer, a first dielectric layer, a first type of cross-shaped structure layer, a second dielectric, a rectangular long strip layer, a third dielectric layer and a second type of cross-shaped structure layer; wherein the first type of cross-shaped structure layer and the second type of cross-shaped structure layer are both composed of two identical ellipses that are superimposed at an angle of 90 degrees and the superimposed part of the ellipses is removed. The multi-layer wave absorbing structure of the present application widens the frequency band by vertically stacking single-layer structures, continuously scanning the structure parameters and optimizing the structure to obtain a wideband absorber. Each single-layer structure resonates longitudinally and influences each other, thereby improving the absorption effect of the absorber in a wide frequency band. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings described herein are used to provide further understanding of the embodiments of the present application, constitute a part of the present application, and do not constitute a limitation on the embodiments of the present application. In the drawings:

[0019] Figure 1 The structure schematic diagram of the wideband terahertz wave absorber based on the multi-layer superposition of cross-shaped structure provided by the embodiments of the present application is shown.

[0020] Figure 2 Fig. 6 shows an absorption curve of the wave absorber provided by the embodiment of the present application when the incidence angle theta of the terahertz wave is 30°;

[0021] Figure 3a Fig. 7 shows the electric field distribution and the current distribution of the wave absorber provided by the embodiment of the present application when the corresponding resonance frequency f1 = 4.88 THz;

[0022] Figure 3b Fig. 8 shows the electric field distribution and the current distribution of the wave absorber provided by the embodiment of the present application when the corresponding resonance frequency f2 = 5.62 THz;

[0023] Figure 3c Fig. 9 shows the electric field distribution and the current distribution of the wave absorber provided by the embodiment of the present application when the corresponding resonance frequency f3 = 6.26 THz;

[0024] Figure 4 Fig. 10 shows an absorption curve of the wave absorber provided by the embodiment of the present application under different incidence angles theta;

[0025] Figure 5 Fig. 11 shows an absorption curve of each layer structure alone and an absorption curve of the overall structure. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be made to the present application in combination with embodiments and drawings, and the schematic embodiments of the present application and the description thereof are only used to explain the present application, and not as a limitation to the present application.

[0027] It should be noted that the term “include” or “may include” used in various embodiments of the present application indicates the existence of the claimed function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present application, the terms “include”, “have” and their homonyms are only intended to represent a specific feature, number, step, operation, element, component or combination of the foregoing, and should not be understood as first excluding the existence or addition of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing.

[0028] In various embodiments of the present application, the expression “or” or “at least one of B or / and C” includes any combination or all combinations of the listed terms. For example, the expression “B or C” or “at least one of B or / and C” can include B, can include C, or can include both B and C.

[0029] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0030] In addition, terms such as "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can be explicitly or implicitly included one or more of the features.

[0031] First, the technical terms of the present application are described.

[0032] Terahertz wave: refers to the frequency between electronics and photonics;

[0033] Terahertz wave absorber: using the resonance characteristics of metamaterial structure, electromagnetic wave energy is converted into heat energy or other forms of energy dissipation, so as to achieve the purpose of absorbing electromagnetic wave.

[0034] Metamaterial: electromagnetic metamaterial is a new concept of emerging discipline proposed in the new century, which runs through the fields of material science, physics, electromagnetism, optics and thermodynamics. It has super-normal physical properties and electromagnetic properties that natural materials do not have.

[0035] Please refer to Figure 1 , Figure 1 A three-dimensional model structure schematic diagram of a wideband terahertz wave absorber based on a multi-layer superposition of a cross-like structure provided by the embodiment of the present application is shown, as Figure 1 The wideband terahertz wave absorber based on the multi-layer superposition of the cross-like structure provided by the embodiment of the present application includes, from bottom to top, a ground layer, a first dielectric layer, a first cross-like structure layer, a second dielectric, a rectangular long strip layer, a third dielectric layer and a second cross-like structure layer; wherein the first cross-like structure layer and the second cross-like structure layer are both composed of two identical ellipses that are 90° superimposed and have a part removed from the superimposed ellipses.

[0036] Specifically, for the components constituting the absorber described in the above embodiment, the material parameters, size and size parameters are as follows: in some embodiments, the first cross-like structure layer, the rectangular long strip layer and the second cross-like structure layer all adopt electric conductivity σ = 4.56 × 10 7Gold with a conductivity of 4.56*10 S / m. The thickness of the first cross-shaped structure layer, the rectangular strip layer and the second cross-shaped structure layer is 200 nm. The length of the major axis of the ellipse constituting the first cross-shaped structure layer and the second cross-shaped structure layer is 14 μm and 12 μm respectively, and the length of the minor axis is 7 μm and 6 μm respectively. The width of the rectangular strip layer along the direction of the major axis of the ellipse is 12.3 μm, and the size in the z-axis direction is 0.625 μm. The size of the first dielectric layer in the z-axis direction is 2.3 μm. The size of the second dielectric layer in the z-axis direction is 2.2 μm. The size of the third dielectric layer in the z-axis direction is 2.8 μm. The size of the first dielectric layer, the second dielectric layer and the third dielectric layer in the x-axis direction and the y-axis direction is equal, and is 30 μm. The size of the ground layer in the x-axis direction and the y-axis direction is equal, and is 30 μm.

[0037] As shown in Figure 1 , the basic structure of the broadband terahertz wave absorber is a sandwich-like layered structure composed of a metamaterial metal layer, a dielectric layer and a ground metal layer. The dielectric layer and the ground metal layer are both conventional technical means in the art, and the present application does not make redundant description. As shown in the lower right part of Figure 1 , the core of the absorber of the present disclosure is the metamaterial metal layer composed of the first cross-shaped structure layer, the rectangular strip layer and the second cross-shaped structure layer. The first cross-shaped structure layer, the rectangular strip layer and the second cross-shaped structure layer are stacked together, and are separated by a dielectric layer with appropriate thickness, so that the resonant absorption frequency corresponding to each single-band metamaterial is close to each other, and is expanded by mutual superposition, thereby achieving the purpose of broadband absorption. The ground layer and the first cross-shaped structure layer, the rectangular strip layer and the second cross-shaped structure layer all adopt gold with a conductivity of 4.56*10 7 S / m, and the thickness is 200 nm; some of the intermediate dielectric layers adopt polyimide with a relative dielectric constant εr=3.5 and a loss tangent tanδ=0.057, for example, the first dielectric layer, the second dielectric layer and the third dielectric layer, and the thicknesses are h, h1 and h2 respectively.

[0038] As shown in Figure 1 ①-③, they are the structure schematic diagrams of the first cross-shaped structure layer, the rectangular strip layer and the second cross-shaped structure layer respectively. The first layer of the metamaterial metal layer is the first cross-shaped structure layer, which is composed of two identical ellipses with a 90° overlap and a part of the ellipse overlap removed, and the major axis is d1 and the minor axis is d1 / 2. The second layer is the rectangular strip layer, and the height is g and the width is k. The third layer is the second cross-shaped structure layer, which is not consistent with the first cross-shaped structure layer in size, and the major axis is d2 and the minor axis is d2 / 2, i.e. d2

[0039] Therefore, the current structural parameters are as follows: the dimensions of the dielectric layers (first dielectric layer, second dielectric layer and third dielectric layer) and the ground layer are Px×Py, Px=Py=30μm, d1=14μm, d2=12μm, g=12.3μm, k=0.625μm, h=2.3μm, h1=2.2μm, h2=2.8μm.

[0040] As those skilled in the art will understand, the specific dimensional parameters of the first type of cross-shaped structural layer, the first dielectric layer, the rectangular strip layer, the second dielectric layer, the second type of cross-shaped structural layer, the third dielectric layer, and the ground layer described in the above embodiments are the optimal parameters obtained from multiple simulation experiments, which ensure the best absorption effect of the absorber over a wide frequency band. Therefore, those skilled in the art can adjust the dimensional parameters according to simulation experiments in addition to the settings described above.

[0041] In the embodiments of this disclosure, simulation results are also provided for the broadband terahertz absorber provided according to the embodiments of this application.

[0042] like Figure 2 As shown, from Figure 2 The simulation results show that the absorption rate reaches over 90% in the resonant frequency range of 4.72-6.38THz.

[0043] like Figure 3a , Figure 3b and Figure 3c The figures show the electric field and current distributions of the absorber at the corresponding resonant frequencies f1 = 4.88 THz, f2 = 5.77 THz, and f3 = 6.26 THz, respectively. Observing the electric field and current distribution at f1, it is clear that the electric field energy is mainly concentrated on the outer frame of the first layer structure and the bottom metal plate. Figure 3a From the electric field profile between the two layers in the left figure and the overall current distribution in the right figure, it can be seen that the two layers form a circulating current and resonate with each other, which forms the f1 absorption peak; as shown in the figure. Figure 3b Observing the electric field and current distribution at point f2, it is clear that the electric energy is mainly concentrated at both ends of the first layer and on the second layer. Current circulates on these two structures, and the two layers resonate with each other, thus forming the absorption peak at f2. Figure 3c Observing the electric field and current distribution at point f3, it is clear that the electric field energy is mainly concentrated at the outer end of the third layer and the two ends of the second layer. The current forms a circulation in these two structures, and the two layers resonate with each other, which forms the f3 absorption peak. Since the frequencies of the three absorption peaks are close to each other, the absorption bands overlap to form broadband absorption.

[0044] like Figure 4 As shown, from Figure 4It can be seen that with the change of the incident angle θ, the absorption curve of the absorption structure is better within 30° in the azimuth angle. In the absorption frequency band, the structure of the wave absorber of the present application can maintain an absorption rate of more than 80%. Because the wave absorber structure of the present application is a spatially symmetric structure, the wave absorber structure of the present application also has the partial characteristic of polarization insensitivity.

[0045] As shown in Figure 5 , from Figure 5 It can be seen that the absorption rate of the single-layer wave absorption structure is only good in a very small frequency band, i.e., reaches an absorption rate of 90% or more. The multi-layer wave absorption structure widens the frequency band by longitudinally stacking single-layer structures and optimizing the structure by continuously scanning the structure parameters. Each single-layer structure influences each other through longitudinal mutual resonance to achieve the purpose of wideband wave absorption.

[0046] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A broadband terahertz absorber based on a multi-layered, cross-shaped structure, characterized in that, From bottom to top, it includes a ground layer, a first dielectric layer, a first type of cross-shaped structure layer, a second dielectric layer, a rectangular strip layer, a third dielectric layer, and a second type of cross-shaped structure layer. Both the first and second type of cross-shaped structure layers are formed by overlapping two identical ellipses at a 90° angle, with the overlapping portion removed. The major axis of the ellipse constituting the first type of cross-shaped structure layer is greater than the major axis of the ellipse constituting the second type of cross-shaped structure layer, and the minor axis of the ellipse constituting the first type of cross-shaped structure layer is greater than the minor axis of the ellipse constituting the second type of cross-shaped structure layer.

2. The broadband terahertz absorber based on a multi-layered, cross-shaped structure as described in claim 1, characterized in that, The first type of cross-shaped structural layer, the rectangular strip layer, and the second type of cross-shaped structural layer all use an electrical conductivity σ=4.56×10 7 S / m of gold.

3. The broadband terahertz absorber based on a multi-layered, cross-shaped structure as described in claim 2, characterized in that, The thickness of the first type of cross-shaped structure layer, the rectangular strip layer, and the second type of cross-shaped structure layer is 200 nanometers.

4. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The major axis lengths of the ellipses constituting the first type of cross-shaped structural layer and the second type of cross-shaped structural layer are 14 micrometers and 12 micrometers, respectively, and the minor axis lengths are 7 micrometers and 6 micrometers, respectively.

5. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The rectangular strip layer has a width of 12.3 micrometers along the major axis of the ellipse and a dimension of 0.625 micrometers along the z-axis.

6. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The first dielectric layer has a dimension of 2.3 micrometers along the z-axis.

7. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The second dielectric layer has a dimension of 2.2 micrometers along the z-axis.

8. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The third dielectric layer has a dimension of 2.8 micrometers along the z-axis.

9. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The first dielectric layer, the second dielectric layer, and the third dielectric layer have the same dimensions in both the x-axis and y-axis directions, which are all 30 micrometers.

10. The broadband terahertz absorber based on a multi-layered, cross-shaped structure according to claim 1, characterized in that, The grounding layer has the same size in both the x-axis and y-axis directions, which is 30 micrometers.

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