Resonant ring based filled terahertz metamaterial broadband absorber

Abstract

The application discloses a kind of filled terahertz metamaterial broadband absorbers based on resonant ring, belong to the technical field of terahertz wave function device.The absorber includes metal reflection layer, intermediate dielectric layer on the metal reflection layer, super material structure layer on the intermediate dielectric layer, the super material structure layer is composed of multiple array arranged unit structure, unit structure includes first square resonant ring and second square resonant ring in first square resonant ring, first square resonant ring and second square resonant ring are provided with the first opening and the second opening of same size on four edges, unit structure is axisymmetric figure;The material of first square resonant ring and second square resonant ring is copper, gold, aluminum or silver, and first opening and second opening are filled with metal titanium or platinum.The application introduces high-loss metal to fill in the opening of conventional open resonant ring, utilizes the resonance of resonant ring and the high absorption of metal filled in opening, realizes the terahertz absorber with very wide absorption band.

Description

Technical Field

[0001] This invention belongs to the field of terahertz wave functional device technology, specifically relating to a broadband absorber of filled terahertz metamaterial based on a resonant ring. Background Technology

[0002] Terahertz waves refer to electromagnetic waves with frequencies ranging from 0.1 THz to 10 THz, falling between millimeter waves and the infrared spectrum. With the development of modern technology, research on millimeter waves and infrared light has deepened, and their devices and application technologies are relatively mature. However, in the terahertz spectrum region, due to the lack of efficient terahertz radiation sources, detectors, and functional devices, the abundant terahertz spectrum resources have not been fully developed and utilized, becoming a current research hotspot. Currently, terahertz application technologies consist of three components: terahertz sources, terahertz functional devices, and terahertz detectors. Among these, devices that utilize metamaterials to achieve perfect absorption of THz waves are called THz metamaterial absorbers. Absorbers have significant applications in electromagnetic stealth, thermal imaging, and thermal sensing, and are also one of the research hotspots for terahertz functional devices.

[0003] Metamaterials are artificial composite materials with special electromagnetic properties. They are generally composed of periodically arranged and combined subwavelength metal microstructure units. Their electromagnetic properties mainly depend on the structural units that cause the resonance response and their periodic arrangement. By adjusting the shape, size and periodic structure of the structural units, the electromagnetic properties of metamaterials can be flexibly controlled.

[0004] The resonant frequency of metamaterial absorbers is usually related to the length of the metallic material. Therefore, there are currently two main methods to achieve multi-band or broadband absorption of incident waves. The first method involves using metamaterial units of different sizes in a patterned metallic layer to form a multi-sized planar metamaterial structure, thus obtaining a multi-band absorber. When the sizes of the metamaterials used are similar, their resonant frequencies overlap, resulting in multiple overlapping absorption peaks and a broadband absorber. However, due to competition among the resonant frequencies generated in this method, the broadband of such absorbers is generally relatively narrow. The second method involves stacking multiple resonators of different sizes to form a layered absorber. Its absorption mechanism is basically the same as the first method, but this method is complex to fabricate, requiring repeated photolithography and deposition processes, and alignment between layers is also necessary, making it difficult to widely apply.

[0005] Electromagnetic waves propagate through conductors under the skin effect, meaning they can only penetrate a certain depth of the conductor's surface. Taking metals as an example, electromagnetic waves penetrating the metal surface couple with free electrons, inducing a surface current. This current absorbs the electromagnetic waves existing in the thin layer of the metal surface through Joule heating, reflecting the remaining waves back into space. This absorption and reflection mechanism causes electromagnetic waves to exist only in a thin layer on the conductor's surface—the skin effect. When the conductor's thickness exceeds the skin depth, the corresponding electromagnetic wave cannot penetrate the conductor; when the thickness is less than the skin depth, the electromagnetic wave can penetrate the conductor, with smaller thicknesses resulting in higher transmittance. For absorbers, the sum of absorptivity, reflectivity, and transmittance is 1. Reducing transmittance and reflectivity increases absorptivity. Therefore, current absorber devices typically have a three-layer structure. The bottom metal layer acts as a reflector, making the transmittance zero. The key is in the design of the reflectivity, which is currently achieved by adjusting the structural parameters of metamaterials. The most commonly used metamaterial structure is the open-loop resonator. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the background technology by proposing a filled terahertz metamaterial broadband absorber based on a resonant ring. The proposed terahertz metamaterial broadband absorber introduces a high-loss metal to fill the opening of the traditional open resonant ring, increasing the overall loss of the superstructure, resulting in a simple structure and excellent performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A broadband absorber based on a resonant ring-filled terahertz metamaterial includes:

[0009] Metal reflective layer 1 is used as a reflector, making the transmittance zero;

[0010] Intermediate dielectric layer 2, which is located on the metal reflective layer 1;

[0011] Metamaterial structure layer 3, which is located on the intermediate dielectric layer 2;

[0012] The metamaterial structure layer 3 is composed of multiple arrayed unit structures. Each unit structure includes a first square resonant ring and a second square resonant ring located within the first square resonant ring. The first square resonant ring has a first opening of the same size on each of its four sides, and the second square resonant ring has a second opening of the same size on each of its four sides. The unit structure is an axisymmetric figure.

[0013] The first and second square resonant rings are made of copper, gold, aluminum or silver, denoted as metal A; the first and second openings are filled with titanium or platinum, denoted as metal B.

[0014] Furthermore, the side length of the unit structure is 74–100 μm; the side length L1 of the first square resonant ring is 54–78 μm, the ring width W1 is 4–10 μm, and the thickness is greater than the skin depth of the metal material of the first square resonant ring; the side length L2 of the second square resonant ring is 28–50 μm, the ring width T2 is 5–13 μm, and the thickness is greater than the skin depth of the metal material of the second square resonant ring; the length T1 of the first opening is 4–12 μm, and the length W2 of the second opening is 4–12 μm.

[0015] Preferably, the side length of the unit structure is 84 μm; the side length L1 of the first square resonant ring is 64 μm, the ring width W1 is 5 μm, the thickness is 0.3 μm, the length T1 of the first opening is 7 μm, and the width W1 is 5 μm; the side length L2 of the second square resonant ring is 34 μm, the ring width T2 is 10 μm, the thickness is 0.3 μm, and the length W2 of the second opening is 10 μm, and the width T2 is 10 μm.

[0016] Furthermore, the metal material filled in the first and second openings is titanium or platinum, with a filling thickness of 3nm to 7nm, preferably 5nm, which is much lower than the skin depth of the metal used, so that the incident terahertz wave can penetrate the opening of the resonant ring and be absorbed and lost.

[0017] Furthermore, the metal reflective layer 1 is made of copper, gold, aluminum, or silver, and its thickness is greater than the skin depth of the reflective metal material. Specifically, the metal reflective layer 1 is made of gold, and its thickness is 0.15–0.3 μm. This thickness of metal can completely reflect terahertz waves, thus acting as a reflector in the absorber, reducing the transmittance of the device, and thereby enhancing the absorption rate.

[0018] Furthermore, the intermediate medium layer 2 is polyimide with a thickness of 12–31 μm, preferably 25 μm.

[0019] Furthermore, the side length of the unit structure is ≤ one-tenth of the operating wavelength.

[0020] Furthermore, the broadband absorber operates in the terahertz band.

[0021] This invention provides a broadband terahertz metamaterial based on a resonant ring. Its working principle is as follows: In this broadband absorber, a high-loss metal is introduced to fill the opening of a traditional open resonant ring. The resonant ring is composed of metal A, with a thickness greater than the skin depth of the corresponding operating frequency band. The opening is filled with a high-loss metal B with a deep sub-skin depth and a thickness much smaller than the skin depth of its corresponding operating frequency band. In this case, the metal B filling the opening is not a reflective structure for terahertz waves, but rather acts as a dielectric material. The terahertz waves at the filling point can pass through the metal material to reach the absorber's interior. Simultaneously, metal B, being a high-loss material, can quickly dissipate the waves entering the absorber, thus obtaining a broadband absorber.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The present invention provides a broadband terahertz metamaterial based on a resonant ring. A high-loss metal is introduced to fill the opening of a traditional open resonant ring. By utilizing the resonance of the resonant ring and the high absorption of the metal at the opening, a terahertz absorber with a wide absorption bandwidth is realized.

[0024] 2. The present invention provides a broadband absorber based on a resonant ring and a filled terahertz metamaterial. It adopts a resonant structure with four open sides of a square ring, which has high symmetry, making the broadband absorber insensitive to the angular polarization of the incident wave.

[0025] 3. The present invention provides a broadband absorber based on a resonant ring filled terahertz metamaterial. The bottom reflective layer is made of metal and its thickness is greater than the skin depth of the metal material at the working frequency. It can reflect all terahertz waves and act as a mirror in the absorber, reflecting the incident waves back so that they are absorbed by the dielectric layer or the top metamaterial along the way, thereby enhancing the absorption rate.

[0026] 4. Compared with traditional absorbers, the present invention provides a broadband absorber based on a resonant ring and filled terahertz metamaterial, which has a wide absorption frequency range, with more than 90% of the absorption frequency range being 0.82THz to 2.18THz, corresponding to a relative absorption bandwidth of 90.7%, and has a simpler structure. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the unit structure in a filled terahertz metamaterial broadband absorber based on a resonant ring, according to an embodiment of the present invention.

[0028] Figure 2 This is a top view of a unit structure in a filled terahertz metamaterial broadband absorber based on a resonant ring, according to an embodiment of the present invention.

[0029] Figure 3This is the absorption spectrum of a broadband terahertz metamaterial based on a resonant ring, according to an embodiment of the present invention.

[0030] Figure 4 The absorption spectrum of a resonant ring-based filled terahertz metamaterial broadband absorber at different polarization angles is shown in this embodiment of the invention.

[0031] Figure 5 This invention relates to an embodiment of a resonant ring-based filled terahertz metamaterial broadband absorber, which addresses the energy loss of various materials. Detailed Implementation

[0032] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments.

[0033] Example

[0034] A broadband absorber based on a resonant ring-filled terahertz metamaterial, such as Figure 1 and 2 As shown, it includes:

[0035] Metal reflective layer 1, made of gold and 300nm thick, is used as a reflector to make the transmittance zero.

[0036] Intermediate dielectric layer 2, made of polyimide, with a thickness of 25 μm, is located above the metal reflective layer 1;

[0037] Metamaterial structure layer 3 is located above intermediate dielectric layer 2;

[0038] The metamaterial structure layer 3 is composed of multiple arrayed unit structures. Each unit structure includes a first square resonant ring and a second square resonant ring located within the first square resonant ring. The first square resonant ring has a first opening of the same size on each of its four sides, and the second square resonant ring has a second opening of the same size on each of its four sides. The unit structure is an axisymmetric figure.

[0039] The first and second square resonant rings are made of gold with a thickness of 300 nm; the first and second openings are filled with platinum with a thickness of 5 nm.

[0040] The dimensions of the unit structure are as follows:

[0041] The side length of the unit structure is 84 μm;

[0042] First square resonant ring: side length L1 = 64 μm, ring width W1 = 5 μm, first opening length T1 = 7 μm;

[0043] The second square resonant ring has a side length L2 = 34 μm, a ring width T2 = 10 μm, and a second opening length W2 = 10 μm.

[0044] Figure 3 The absorption spectrum of a broadband terahertz metamaterial absorber based on a resonant ring, as shown in the embodiment; by Figure 3 It can be seen that the absorber in the embodiment has an absorption frequency band of 0.82THz to 2.18THz of more than 90%, corresponding to a relative absorption bandwidth of 90.7%.

[0045] Figure 4 The absorption spectrum of a resonant ring-based filled terahertz metamaterial broadband absorber at different polarization angles is shown in the embodiment. Figure 4 It can be seen that the absorption peak of the absorber in the embodiment does not change with the change of polarization angle.

[0046] Figure 5 This embodiment illustrates the energy loss of various materials in a filled terahertz metamaterial broadband absorber based on a resonant ring; [The remaining text appears to be a fragmented and incomplete sentence, possibly due to OCR errors. A more accurate translation would require the full context.] Figure 5 It can be seen that the energy of the absorber in the embodiment is mainly lost in the metal B that fills the opening of the resonant ring.

[0047] The above description is only a preferred embodiment of the present invention, and not all embodiments. The scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A broadband absorber based on a resonant ring and filled terahertz metamaterial, characterized in that, include: Metal reflective layer (1); Intermediate dielectric layer (2), the intermediate dielectric layer being located above the metal reflective layer; Metamaterial structure layer (3), the metamaterial structure layer is located above the intermediate medium layer; The metamaterial structure layer is composed of multiple arrayed unit structures. Each unit structure includes a first square resonant ring and a second square resonant ring located within the first square resonant ring. The first square resonant ring has a first opening of the same size on each of its four sides, and the second square resonant ring has a second opening of the same size on each of its four sides. The unit structure is an axisymmetric figure. The first square resonant ring and the second square resonant ring are made of copper, gold, aluminum or silver. The thickness of the first square resonant ring is greater than the skin depth of the material of the first square resonant ring, and the thickness of the second square resonant ring is greater than the skin depth of the material of the second square resonant ring. The first and second openings are filled with titanium or platinum with a thickness of 3nm to 7nm. The thickness of the metal reflective layer is greater than the skin depth of the metal reflective layer material.

2. The broadband absorber based on a resonant ring and filled terahertz metamaterial according to claim 1, characterized in that, The side length of the unit structure is 74~100 μm; the side length of the first square resonant ring is 54~78 μm and the ring width is 4~10 μm; the side length of the second square resonant ring is 28~50 μm and the ring width is 5~13 μm; the length of the first opening is 4~12 μm and the length of the second opening is 4~12 μm.

3. The broadband absorber based on a resonant ring and filled terahertz metamaterial according to claim 1, characterized in that, The material of the metal reflective layer is copper, gold, aluminum or silver.

4. The broadband absorber based on a resonant ring and filled terahertz metamaterial according to claim 1, characterized in that, The intermediate medium layer is polyimide with a thickness of 12~31μm.

5. The broadband absorber based on a resonant ring and filled terahertz metamaterial according to claim 1, characterized in that, The side length of the unit structure is less than or equal to one-tenth of the operating wavelength.

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