A narrow-band and wide-band terahertz wave absorber

Abstract

The application discloses a narrow-band and wide-band terahertz wave absorber and relates to the technical field of terahertz wave absorbers. The structure comprises a ground metal layer, a dielectric layer and a metal patch layer which are sequentially stacked from bottom to top, the metal patch layer has a T-shaped opening which is inwardly contracted, and the remaining part of the metal patch layer after the T-shaped opening is removed is a symmetrical structure. The terahertz wave absorber can simultaneously achieve a high absorption rate of 90% on a narrow-band frequency and a wide-band frequency, breaks through the problem that the prior art can only be used for high-efficiency absorption in one aspect of a narrow band or a wide band, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of terahertz wave absorber technology, and more particularly to a narrowband and broadband terahertz wave absorber. Background Technology

[0002] Terahertz waves refer to the frequency band between electronics and photonics. Terahertz absorbers are devices that utilize the resonant characteristics of metamaterial structures to convert electromagnetic wave energy into heat or other forms of energy dissipation, thereby achieving the purpose of absorbing electromagnetic waves. They play an important role in various terahertz circuit systems. Designing broadband absorbers with simple structure, high absorption bandwidth, and easy tuning has become a hot topic in the research field of terahertz functional devices.

[0003] Currently, absorbing devices based on metamaterial structures mainly operate in the microwave frequency band, while the practical application of metamaterial-based terahertz frequency absorbers still faces certain challenges. In related technologies, common broadband absorbers are typically composed of stacked multi-layer structures or multiple structures laid out in an array, resulting in relatively complex structures. Furthermore, terahertz absorption designs either only achieve high narrowband absorption or only high broadband absorption. Therefore, simplifying absorber structure design and further improving absorption performance across multiple frequency bands are the current breakthrough directions for terahertz wave absorbers. Summary of the Invention

[0004] This invention provides a narrowband and broadband terahertz wave absorber to solve the problem that existing stacked absorbers have complex structures and can only achieve good absorption for narrowband or broadband.

[0005] This invention is achieved through the following technical solution:

[0006] A narrowband and broadband terahertz wave absorber is provided, the absorber comprising a ground metal layer, a dielectric layer and a metal patch layer stacked sequentially from bottom to top;

[0007] The upper surface of the grounding metal layer covers the lower surface of the dielectric layer, and the upper surface of the dielectric layer covers the lower surface of the metal patch layer;

[0008] The metal patch layer has an inwardly tapering T-shaped opening, and the remaining portion of the metal patch layer after removing the T-shaped opening has a symmetrical structure.

[0009] The terahertz wave absorber designed by the application is composed of a "sandwich" sandwich structure of a grounding metal layer, a dielectric layer and a metal patch layer, and is simple in structure and preparation, and due to the T-shaped symmetric opening of the metal patch, the structure coupling on both sides of the opening and the bottom can be easily formed, thereby forming an absorption peak. According to the different distribution of current and electric field on the metal patch in different terahertz frequency bands, different resonance modes are formed, the absorption peak is realized on a narrow band and a wide band at the same time, the terahertz frequency band range of the absorption peak is widened, and high absorption rate is achieved in multiple frequency bands. The verification experiment shows that the terahertz wave absorber of the application can achieve a high absorption rate of 90% in two narrow band frequencies and a wide band frequency, thereby breaking through the problem of the prior art that only one aspect of narrow band or wide band can be efficiently absorbed, and having a wide application prospect.

[0010] Further, the material of the grounding metal layer includes at least one of gold, silver and copper.

[0011] Further, the thickness of the grounding metal layer is 0.4 μm.

[0012] Further, the material of the metal patch layer includes at least one of gold, silver and copper.

[0013] Further, the material of the dielectric layer includes at least one of silicon dioxide, aluminum oxide, polyethylene cycloolefin copolymer and polyimide.

[0014] Further, the real part of the dielectric constant of the dielectric layer is 3, and the loss tangent is 0.06.

[0015] Further, the thickness of the dielectric layer is 6.5 μm.

[0016] Further, the size of the T-shaped opening satisfies: l1>l4, l3>l2; wherein, l1 represents the width of the horizontal block of the T-shaped opening, l2 represents the depth of the horizontal block of the T-shaped opening, l3 represents the depth of the vertical block of the T-shaped opening, and l4 represents the width of the vertical block of the T-shaped opening.

[0017] Further, the cross-sectional shape of the grounding metal layer and the dielectric layer includes one of a polygon, a circle and an ellipse.

[0018] Further, the cross-sectional shape of the grounding metal layer and the dielectric layer is the same.

[0019] Compared with the prior art, the application has the following advantages and beneficial effects:

[0020] The terahertz wave absorber is composed of a "sandwich" sandwich structure of a grounding metal layer, a dielectric layer and a metal patch layer, and is simple in structure and preparation, and does not need a complex stacking structure, and can effectively absorb terahertz waves.

[0021] The T-shaped opening is arranged on the metal patch of the upper layer, the caliber of the T-shaped opening is large at the outside and small at the inside, and the structure of the metal patch is symmetrical, so that the structural coupling is easily formed on both sides of the symmetrical opening and both sides of the bottom of the metal patch, thereby forming a resonance sound absorption peak and improving the absorption rate of the terahertz wave.

[0022] For different terahertz frequency bands, different distributions of the current and the electric field on the metal patch form resonance absorption peaks corresponding to the frequency bands, and verification experiments show that the absorber can achieve a high absorption rate of 90% on two narrowband frequencies and one broadband frequency band, thereby breaking through the problem that the prior art can only absorb in one aspect of narrowband or broadband, realizing the simultaneous absorption of narrowband and broadband, and having a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the example embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0024] Figure 1 is a side view of a basic structure of a narrowband and broadband terahertz wave absorber according to an embodiment of the present application;

[0025] Figure 2 is a top view of a basic structure of a narrowband and broadband terahertz wave absorber according to an embodiment of the present application;

[0026] Figure 3 is an absorption curve simulation diagram of a narrowband and broadband terahertz wave absorber according to an embodiment of the present application;

[0027] Figure 4 is an electric field distribution and current distribution diagram of a narrowband and broadband terahertz wave absorber according to an embodiment of the present application at a corresponding resonance frequency;

[0028] Figure 5 is an absorption curve simulation diagram of a narrowband and broadband terahertz wave absorber according to an embodiment of the present application at different incident angles.

[0029] The reference signs are explained as follows:

[0030] 1-grounded metal layer, 2-dielectric layer, 3-metal patch layer, 4-T-shaped opening, 41-horizontal block, 42-vertical block. DETAILED DESCRIPTION

[0031] In order to make the objects, 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, the schematic embodiments and the description thereof are only used to explain the present application, and do not limit the present application.

[0032] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of the present application and the above drawings are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units does not have to be limited to or inherent to other steps or units.

[0033] The terms used in the various embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the present application belong. The terms (such as those defined in commonly used dictionaries) will be interpreted as having a meaning that is the same as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of the present application.

[0034] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without these specific details. In other embodiments, in order to avoid obscuring the present application, well-known structures, circuits, materials or methods are not specifically described.

[0035] The embodiment of the present application provides a narrow-band and wide-band terahertz wave absorber, which is suitable for various terahertz circuit systems and is beneficial to realizing high absorption rate of terahertz waves in narrow-band and wide-band multi-frequency bands.

[0036] The frequency range of terahertz waves (THz) is 0.1 THz-10 THz, which bridges the microwave and infrared regions of the electromagnetic spectrum, has the characteristics of high penetration, wide spectrum and non-ionizing radiation, and thus has strong application prospects in the fields of security inspection, medical imaging and communication. The terahertz wave absorber is a passive device with directionality, and has strong application value in the fields of terahertz detector, terahertz communication and terahertz imaging.

[0037] The concept of metamaterials arose from humanity's breakthrough in overcoming the limitations of natural materials' response to electromagnetic waves. Periodic structures obtained through subwavelength artificial unit structures possess the ability to manipulate the phase, amplitude, and polarization of electromagnetic waves, enabling phenomena such as negative refractive index, zero refractive index, and electromagnetic invisibility. As an artificial electromagnetic medium, the electromagnetic properties of metamaterials are related to their shape and geometry; therefore, metamaterials can act on visible light, infrared, microwave, and terahertz bands by altering their structure and size. This offers significant electromagnetic manipulation advantages for bands lacking suitable natural materials, such as the terahertz band. Based on the flexible electromagnetic response characteristics of metamaterials, rapid progress has been made in the development of terahertz devices in the past decade. Taking terahertz absorbers as an example, researchers have proposed absorbers with different functions, such as perfect absorbers, multi-band absorbers, and broadband absorbers. However, current terahertz absorbers are either designed for perfect absorption in specific narrow bands or only designed to broaden the absorption bandwidth; devices that can simultaneously achieve narrowband and broadband absorption are lacking.

[0038] This invention addresses the shortcomings of existing terahertz wave absorbers by designing a narrow-band and broadband perfect terahertz absorber based on a U-shaped metal patch, which has the advantages of simple structure, high absorption bandwidth and easy tuning.

[0039] See Figures 1-2 As shown, Figure 1 This is a side view of the basic structure of the narrowband and broadband terahertz wave absorber. Figure 2 This is a top view of the basic structure of the narrowband and broadband terahertz wave absorber. The basic structure of the terahertz wave absorber includes: a ground metal layer 1, a dielectric layer 2, and a metal patch layer 3. The absorber as a whole has a "sandwich" structure.

[0040] With ground as a reference, from bottom to top, the layers are a grounding metal layer 1, a dielectric layer 2, and a metal patch layer 3. The grounding metal layer 1 serves as the substrate of the absorber, its function being to ground the light and prevent incident light waves from being transmitted through this layer, thus making the absorber's transmittance infinitely close to zero. The grounding metal layer 1 can be made of at least one of gold, silver, and copper, giving it good conductivity.

[0041] The intermediate layer is dielectric layer 2. The thickness and material of the dielectric layer have a significant impact on the absorption rate of the absorption layer. The dielectric layer can be made of a single material, including silica, alumina, polyethylene cyclic olefin copolymer, polyimide, etc.; or it can be made of a composite material, such as a composite of at least two of silica, alumina, polyethylene cyclic olefin copolymer, and polyimide, or a composite of at least one of these materials with other materials. The upper surface of the grounding metal layer 1 covers the lower surface of the dielectric layer 2.

[0042] The ground metal layer and the dielectric layer are plate-shaped structures, and their specific shapes are not limited, and can be polygonal shapes such as triangle, quadrilateral, pentagon, hexagon, and plate-shaped structures such as circle and ellipse.

[0043] The uppermost layer is a metal patch layer 3 of metamaterial. In this embodiment, the metal patch adopts a U-shaped structure design, that is, a T-shaped opening 4 is arranged on the metal patch, as shown in the figure. Figure 2 The T-shaped opening 4 can be divided into two parts: a horizontal block 41 and a vertical block 42. The horizontal block of the T-shaped opening is outward, and the vertical block is inward. Therefore, the metal patch presents a shape with the opening inwardly shrinking, and the remaining part after removing the T-shaped opening is a symmetrical structure. It can also be understood that the metal patch is to dig out a smaller U-shaped structure from the U-shaped structure. This structure utilizes the asymmetry in the x direction (electric field direction) to induce the excitation of multiple high-order resonance modes with similar frequencies on the basis of the basic resonance mode, thereby realizing a metamaterial device with narrowband and broadband absorption functions integrated in one, and the structure is simple and easy to manufacture.

[0044] The upper surface of the dielectric layer 2 covers the lower surface of the metal patch layer 3, that is, the surface areas of the two can be the same, and the edge of the upper surface of the dielectric layer 2 can also exceed the metal patch layer 3, as shown in the figure. Figure 2 It is found through simulation comparison that the absorption effect is better when the cross-sectional area of the metal patch layer is smaller than that of the dielectric layer. The terahertz wave incident on the absorber resonates with the U-shaped metal patch, and the energy of the electromagnetic wave is effectively transferred and stored in the wave-absorbing structure, thereby forming an absorption peak, and the coupling between the structures forms a broadband absorption.

[0045] The material of the metal patch layer can be at least one of gold, silver, and copper, so that it has good electrical conductivity.

[0046] In some embodiments, the cross-sectional shapes of the ground metal layer 1 and the dielectric layer 2 are the same, for example, both are circular or polygonal. It can be understood that the shapes of the two can also be different.

[0047] Preferably, the ground metal layer 1 and the dielectric layer 2 are both rectangular plate-shaped structures, and the area of the upper surface of the ground metal layer 1 is the same as the area of the lower surface of the dielectric layer 2. The rectangular plate is easy to cut and manufacture, and has good symmetry. More preferably, it is a square plate-shaped structure, that is, the cross-section of the ground metal layer and the dielectric layer is a square.

[0048] In some embodiments, the ground metal layer 1 and the metal patch layer 3 are both composed of gold, and the dielectric layer 2 is a lossy polymer. The real part of the dielectric constant of the dielectric layer is 3, and the loss tangent is 0.06.

[0049] In some embodiments, since the absorber of the present application is a metamaterial structure, the resonant frequency can be adjusted by adjusting the thickness of the ground metal layer, the dielectric layer, the metal patch layer, the size of the T-shaped opening, so as to realize the absorption peak in the required working frequency band. Within a certain size range, both narrowband and broadband absorption can be realized, and the frequency of the terahertz wave absorber can be adjusted.

[0050] In some embodiments, the width (x direction) of the transverse block 41 of the T-shaped opening is represented by l1, the depth (-y direction) is represented by l2, the width (x direction) of the vertical block 42 is represented by l4, and the depth (-y direction) is represented by l3. The size of the T-shaped opening satisfies: l1>l4, l3>l2.

[0051] In some embodiments, the size of the metal patch is lx×ly, lx represents the width of the metal patch, and ly represents the length of the metal patch. lx<ly, and the T-shaped opening is located on the longer side of the metal patch.

[0052] In some embodiments, the size of the metal patch is: lx=ly=40μm, the size of the T-shaped opening is: l1=16μm, l2=12μm, l3=14μm, and l4=3μm. Under this size, the absorber has high absorption rate and wide band.

[0053] In some embodiments, the thickness of the ground metal layer is t1=0.4μm. The thickness of the metal layer should be greater than the thickness of the skin effect, so as to realize the total reflection of the incident electromagnetic wave.

[0054] In some embodiments, the thickness of the dielectric layer is t2=6.5μm. The thickness and material of the dielectric layer also have a great influence on the absorption rate of the absorber. This size can form a good cooperation with the above-mentioned U-shaped metal patch, so as to maximize the comprehensive performance of the absorber, that is, the absorption rate is the highest and the wideband absorption bandwidth is the largest.

[0055] In addition, simulation tests were conducted on the terahertz wave absorber of the present application, as shown in Figure 3 The absorption curve simulation diagram of the narrowband and broadband terahertz wave absorber of the present application is shown in the figure. The structure of the terahertz wave absorber used in the simulation test is shown in Figures 1-2 The ground metal layer and the metal patch layer are both composed of gold, the material of the dielectric layer is polyimide, the cross section of the ground metal layer and the dielectric layer is square, the side length is 60μm, the thickness of the ground metal layer is t1=0.4μm, the thickness of the dielectric layer is t2=6.5μm, the size of the metal patch of the metal patch layer is lx=ly=40μm, the thickness of the metal patch layer is 0.4μm, and the size of the T-shaped opening on the metal patch layer is: l1=16μm, l2=12μm, l3=14μm, and l4=3μm.

[0056] As shown in Figure 3As shown, the resonance frequency reaches more than 90% of the absorption rate at f1=1.36THz and f2=2.64THz, and the absorption rate reaches more than 90% in the wide band formed by f3=4.1THz, f4=4.4THz and f5=4.7THz, achieving perfect absorption. As can be seen, the terahertz sound absorber of the present application realizes high absorption rate in narrow band (resonance frequency f1, f2) and wide band (resonance frequency f3-f5) at the same time, expands the absorption bandwidth, and has greater application prospect compared with the terahertz sound absorber with only high absorption rate for narrow band and only high absorption rate for wide band.

[0057] Referring to Figure 4 As shown, Figure 4 The narrow-band and wide-band terahertz wave absorber of the present application is the electric field distribution and current distribution diagram at the corresponding resonance frequency (f1=1.36THz, f2=2.64THz, f3=4.1THz, f4=4.4THz, f5=4.7THz), in which (a)-(e) show the electric field distribution, and (f)-(j) show the current distribution.

[0058] According to (a) and (f), it is shown that at the resonance frequency f1, the electric field is mainly concentrated on the left and right sides of the opening of the U-shaped metal patch, and the current is mainly concentrated on the T-shaped opening (deepened part), and the current flows in the clockwise direction, and the absorption peak is formed by LC resonance. According to (b) and (g), it is shown that at the resonance frequency f2, the electric field is concentrated on the left and right sides of the opening of the U-shaped metal patch, and the left and right lower corners of the metal patch (deepened part), and the four concentrated positions represent typical four dipoles, and the current is mainly concentrated on the upper rectangular block of the T-shaped opening, and the current flows in the counterclockwise direction, and the absorption peak is formed by four-pole resonance. According to (c) and (h), it is shown that at the resonance frequency f3, the electric field is mainly distributed on the four corners of the U-shaped metal patch and the left and right sides of the lower rectangle of the T-shaped opening (deepened part), and the current in the upper rectangle of the T-shaped opening and the current in the lower rectangle of the T-shaped opening are opposite, the current in the upper rectangle flows in the clockwise direction, and the current in the lower rectangle flows in the counterclockwise direction, so the resonance frequency f3 is caused by the radiation of six dipoles. According to (d) and (i), it is shown that at the resonance frequency f4, the electric field is mainly distributed on the two side edges of the U-shaped metal patch and near the T-shaped opening, and the left and right lower corners of the metal patch (deepened part), and the current is mainly distributed on the four corners of the U-shaped metal patch and the lower rectangle of the T-shaped opening, and the current flowing directions in the upper left corner and the upper right corner of the U-shaped metal patch are the same, while the current flowing directions in the lower left corner and the lower right corner of the U-shaped metal sheet are opposite. According to (e) and (j), it is shown that at the resonance frequency f5, the electric field distribution is similar to that of the resonance mode f4, and the current is mainly distributed on the left and right lower corners of the U-shaped metal patch and the lower rectangle of the T-shaped opening, and the current flowing directions in the lower left corner and the lower right corner of the U-shaped metal patch are opposite to those in the resonance frequency f4, and the resonance frequency f5 is the result of the superposition of the dipole resonance mode caused by the lower rectangle and the dipole radiation mode caused by the parallel metal.

[0059] The terahertz wave absorber of the present application can realize multiple modes of resonance, thereby realizing multiple absorption peaks and achieving multi-band absorption.

[0060] Referring to Figure 5 as shown, Figure 5 The absorption curve simulation diagram of the narrowband and broadband terahertz wave absorber of the present application under different incident angles (0°, 5°, 10°, 15°, 20°, 25°) can be seen that with the change of the incident angle θ, the absorption curve of the absorber is good within the incident angle of 25°. The narrowband absorption rate at the resonance frequencies f1 and f2 remains above 90%, and within the broadband absorption frequency band formed by f3-f5, the absorption rate can be maintained above 80%. And between the resonance frequencies f2 and f3, new absorption peaks will gradually form as the incident angle increases.

[0061] The simulation test shows that the U-shaped metal patch based narrow-band and wide-band terahertz perfect absorbers have a wide absorption band and a high absorption rate narrow-band absorption peak.

[0062] The above detailed description of the embodiments of the present application is further detailed to explain the purposes, technical solutions and beneficial effects of the present application. It should be understood that the above detailed 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. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A terahertz wave absorber of narrowband and broadband, characterized by, The ground metal layer, the dielectric layer and the metal patch layer are sequentially stacked from bottom to top; An upper surface of the ground metal layer covers a lower surface of the dielectric layer, and an upper surface of the dielectric layer covers a lower surface of the metal patch layer; the ground metal layer and the dielectric layer have the same cross-sectional shape; The metal patch layer is designed by using a U-shaped structure metal patch, the metal patch has a T-shaped opening that is inwardly retracted, the size of the metal patch is lxly, lx represents the width of the metal patch, and ly represents the length of the metal patch, the T-shaped opening is located on the longer side of the metal patch, the T-shaped opening is divided into a horizontal block and a vertical block, the horizontal block is outward, the vertical block is inward, and the remaining part of the metal patch layer after the T-shaped opening is removed is a symmetrical structure, thereby inducing excitation of multiple high-order resonance modes with similar frequencies on the basis of a basic resonance mode, and narrowband and broadband absorption functions are realized; The size of the T-shaped opening satisfies: , ; wherein, represents the width of the lateral block of the T-shaped opening, represents the depth of the lateral block of the T-shaped opening, represents the depth of the vertical block of the T-shaped opening, represents the width of the vertical block of the T-shaped opening.

2. The narrowband and broadband terahertz wave absorber according to claim 1, characterized by, The material of the ground metal layer includes at least one of gold, silver and copper.

3. The narrowband and broadband terahertz wave absorber according to claim 2, characterized by The thickness of the ground metal layer is 0.4 µm, so as to realize total reflection of incident electromagnetic waves.

4. The narrowband and broadband terahertz wave absorber according to claim 1, wherein The material of the metal patch layer includes at least one of gold, silver and copper.

5. The narrowband and broadband terahertz wave absorber according to claim 1, wherein The material of the dielectric layer includes at least one of silicon dioxide, aluminum oxide, polyethylene cycloolefin copolymer and polyimide.

6. The narrowband and broadband terahertz wave absorber according to claim 5, characterized by The real part of the dielectric constant of the dielectric layer is 3, and the loss tangent is 0.

06.

7. The narrowband and broadband terahertz wave absorber according to claim 5, characterized by The thickness of the dielectric layer is 6.5 µm.

8. The narrowband and broadband terahertz wave absorber according to claim 1, wherein The cross-sectional shape of the ground metal layer and the dielectric layer includes one of a polygon, a circle and an ellipse.

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