A quasi-terahertz wave full-absorption metasurface absorber and a preparation method thereof

Abstract

The application discloses a kind of quasi-terahertz wave full absorption metasurface absorber and preparation method thereof, the structure of absorber includes: the design of silica layer, graphene multilayer structure and metal base;The structural design of top silica four pyramid;The structural design of multilayer graphene electric control simultaneously.The application uses multilayer graphene to enhance terahertz wave absorption, through the control of external bias voltage, can control the absorption intensity of low-frequency absorption band, realize certain degree of tunability.In terahertz wave band, the metasurface absorber proposed in the application can reach 96.33% average absorption in 0.5-10.0THz band.The application can effectively solve the problem that current absorber can only absorb part of terahertz wave band, open a new road for high performance of terahertz wave absorption field device.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorption and modulation, specifically to a quasi-terahertz wave total absorption metasurface absorber and its preparation method. Background Technology

[0002] Highly efficient terahertz absorbers play a crucial role in terahertz detectors, which have applications in various fields, including military stealth, 6G communications, astronomy, security detection, and medical imaging. To meet the demands of modern detector technology, absorbers must exhibit a broad and consistent spectral response while maintaining a relatively small thickness. Metasurfaces, the two-dimensional counterpart of metamaterials, have attracted widespread attention due to their unique optical properties. Composed of artificial materials organized with periodic structures, metasurfaces are renowned for their special electromagnetic properties, tunable refractive index, and asymmetric transmission characteristics. These properties make metasurfaces particularly suitable for electromagnetic absorption. Since Landy et al. first introduced metasurface absorbers, an increasing number of high-performance metasurface-based absorbers have been proposed and demonstrated.

[0003] Traditional research on metasurface absorbers typically focuses on absorption within specific wavelength bands, categorized into narrowband and broadband absorption modes. Compared to narrowband absorption, broadband absorption has a wider range of potential applications. Therefore, researchers have been seeking strategies to further enhance absorption bandwidth, with common approaches involving layering multiple absorbing materials. For example, Yan et al. proposed a bilayer graphene-based metasurface absorber capable of achieving broadband absorption up to 0.65 THz. Amini et al. extended this concept by introducing a trilayer graphene-based pyramidal metasurface absorber, significantly broadening the absorption bandwidth to 4.57 THz. However, achieving ultra-wideband absorption in electromagnetic absorbers remains challenging. Existing graphene structures may not be suitable for broadband absorption in metasurface absorber configurations because they require high-precision patterning, limiting their wider application. Another approach is to introduce different micro / nanostructures on the surface or substrate of the metasurface device to induce different optical responses to electromagnetic waves, thereby enhancing absorption. For example, Cheng et al. proposed adding a metal grating beneath the metasurface, achieving an absorption bandwidth of 2.58 THz using only a single layer of absorbing material. However, it has been difficult to combine these two methods and achieve ultra-wideband terahertz wave absorption.

[0004] To address the aforementioned issues, this invention proposes a quasi-terahertz wave total absorption metasurface absorber and its fabrication method, in order to meet the current demand for such broadband metasurface absorbers in the terahertz wave field. Summary of the Invention

[0005] In order to achieve multifunctional control of terahertz waves, this invention proposes a structural design and fabrication method for a quasi-terahertz wave full-absorption metasurface absorber. The proposed structure can achieve full absorption of quasi-terahertz waves while maintaining a relatively thin thickness, which can effectively solve the problem that current terahertz metasurfaces cannot absorb incident waves across the entire wavelength range.

[0006] The specific technical solution is as follows:

[0007] This invention proposes a structural design for a quasi-terahertz wave total absorption metasurface absorber, comprising, from top to bottom: a silicon dioxide square frustum 1 for terahertz wave absorption; a first graphene layer 2 for regulating terahertz wave absorption; a first silicon dioxide dielectric layer 3 for terahertz wave absorption; a second graphene layer 4 for regulating terahertz wave absorption; a second silicon dioxide dielectric layer 5 for terahertz wave absorption; a third graphene layer 6 for regulating terahertz wave absorption; a third silicon dioxide dielectric layer 7 for terahertz wave absorption; a metal substrate 8 for total reflection of terahertz waves; and an external bias voltage 9 for regulating the chemical potential of the graphene layers.

[0008] The period of the absorber structure unit described in this invention is 44.1 μm.

[0009] The top of the structural unit is a regular square frustum, and the bottom is a cuboid with a square cross-section. The sides of the square cross-section are aligned with the bottom edge of the regular square frustum and are of equal length.

[0010] The first to third dielectric layers are all made of silicon dioxide with a refractive index of 1.5; the metal substrate is made of silver.

[0011] The upper base of the silicon dioxide regular square truncated pyramid at the top of the structural unit has a side length of 10.9 μm, the lower base has a side length of 44.1 μm, the height of the silicon dioxide regular square truncated pyramid is 49.1 μm, the thickness of the first silicon dioxide dielectric layer is 11.5 μm, the thickness of the second silicon dioxide dielectric layer is 13.5 μm, the thickness of the third silicon dioxide dielectric layer is 8.0 μm, and the thickness of the metallic silver is 1.0 μm.

[0012] The thickness of the first to third graphene layers is very thin, approximately 0.33 nm.

[0013] All graphene layers are connected to an external bias voltage 9. By controlling the external bias voltage, the absorption intensity of the low-frequency band of the absorber can be adjusted. The voltage adjustment range is 0-15V.

[0014] The beneficial effects of this invention are:

[0015] 1. The absorber described in this invention solves the problem that the absorption bandwidth of terahertz metasurfaces is still relatively small. It achieves full absorption of quasi-terahertz waves when the structure has a relatively thin thickness.

[0016] 2. The absorber described in this invention solves the current problem of unadjustable absorption intensity of terahertz metasurfaces, and achieves adjustable absorption intensity in the low-frequency band. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a quasi-terahertz wave total absorption metasurface absorber proposed in this invention.

[0018] Figure 2 This is a schematic diagram of a structural unit of a quasi-terahertz wave total absorption metasurface absorber proposed in this invention.

[0019] 1. A regular square frustum of silicon dioxide; 2. A first graphene layer; 3. A first silicon dioxide dielectric layer; 4. A second graphene layer; 5. A second silicon dioxide dielectric layer; 6. A third graphene layer; 7. A third silicon dioxide dielectric layer; 8. A metal substrate; 9. An applied bias voltage.

[0020] Figure 3 This is a schematic diagram of the structural parameters of a single structural unit of a multifunctional terahertz metasurface that integrates absorption, transmission, and reflection proposed in this invention. The upper base of the silicon dioxide square frustum is d1 = 10.9 μm, the lower base is d2 = 44.1 μm, the period of the structural unit is d3 = 44.1 μm, the height of the silicon dioxide square frustum is h1 = 49.1 μm, the height of the first silicon dioxide dielectric layer is h2 = 11.5 μm, the height of the second silicon dioxide dielectric layer is h3 = 13.5 μm, the height of the third silicon dioxide dielectric layer is h4 = 8.0 μm, and the thickness of the silver layer is h5 = 1.0 μm.

[0021] Figure 4 This is a graph showing the absorptivity versus frequency of the quasi-terahertz wave fully absorbing metasurface absorber proposed in this invention.

[0022] Figure 5 The graph shows the absorption rate of the quasi-terahertz wave fully absorbing metasurface absorber proposed in this invention as a function of frequency at different voltages on graphene. Detailed Implementation

[0023] The invention will now be further described with reference to the accompanying drawings.

[0024] Figure 1 The diagram shown is a schematic of a quasi-terahertz wave total absorption metasurface absorber. Figure 2This is a schematic diagram of a structural unit of a quasi-terahertz wave total absorption metasurface absorber proposed in this invention. It includes a silicon dioxide square frustum 1; a first graphene layer 2; a first silicon dioxide dielectric layer 3; a second graphene layer 4; a second silicon dioxide dielectric layer 5; a third graphene layer 6; a third silicon dioxide dielectric layer 7; a metal substrate 8; and an applied bias voltage 9. The dielectric layer material is silicon dioxide; 9 represents the external bias voltage, which enables simultaneous modulation of the graphene chemical potential.

[0025] like Figure 3 The diagram shows the structural parameters of a structural unit, where the upper base of the silicon dioxide square frustum is d1 = 10.9 μm, the lower base of the silicon dioxide square frustum is d2 = 44.1 μm, the period of the structural unit is d3 = 44.1 μm, the height of the silicon dioxide square frustum is h1 = 49.1 μm, the height of the first silicon dioxide dielectric layer is h2 = 11.5 μm, the height of the second silicon dioxide dielectric layer is h3 = 13.5 μm, the height of the third silicon dioxide dielectric layer is h4 = 8.0 μm, and the thickness of the silver layer is h5 = 1.0 μm.

[0026] like Figure 4 , Figure 5 As shown, at a voltage of 15V, when a terahertz wave is incident, due to the combined effect of the top silicon dioxide square truncated pyramid and the middle multilayer graphene, the absorber can achieve full-band absorption in the 0.5 to 10THz range, with an average absorption rate of 96.33%. When the external bias voltage is changed to 0V, corresponding to the 0eV voltage of the graphene, the absorption rate at low frequencies drops sharply to 30%, with a tuning range approaching 70%, demonstrating excellent adjustable performance.

[0027] This invention provides a method for fabricating a quasi-terahertz wave total absorption metasurface absorber, which is completed according to the following steps:

[0028] (1) A 1 μm thick layer of silver was deposited using electron beam evaporation to form the metal substrate;

[0029] (2) Silicon dioxide is spin-coated onto the surface of the silver layer and baked to form the third dielectric layer;

[0030] (3) Transfer the graphene layer over the third dielectric layer to form the third graphene layer;

[0031] (4) Silicon dioxide is spin-coated onto the surface of the third graphene layer and baked to form the second dielectric layer;

[0032] (5) Transfer the graphene layer over the second dielectric layer to form the second graphene layer;

[0033] (6) Silicon dioxide is spin-coated onto the surface of the second graphene layer and baked to form the first dielectric layer;

[0034] (7) Transfer the graphene layer over the first dielectric layer to form the first graphene layer;

[0035] (8) A square frustum silicon dioxide layer is fabricated on the surface of the first graphene layer using magnetron sputtering. This completes the fabrication of the broadband terahertz absorber.

[0036] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent methods or modifications that do not depart from the technology of the present invention should be included within the scope of protection of the present invention.

Claims

1. A quasi-terahertz wave total absorption metasurface absorber, characterized in that, Composed of several structural units arranged in sequence, each structural unit includes, from top to bottom: a silicon dioxide square frustum (1) for terahertz wave absorption; a first graphene layer (2) for regulating terahertz wave absorption; a first silicon dioxide dielectric layer (3) for terahertz wave absorption; a second graphene layer (4) for regulating terahertz wave absorption; a second silicon dioxide dielectric layer (5) for terahertz wave absorption; a third graphene layer (6) for regulating terahertz wave absorption; a third silicon dioxide dielectric layer (7) for terahertz wave absorption; a metal substrate (8) for total reflection of terahertz waves; and an external bias voltage (9) for regulating the chemical potential of the graphene layer. The top of the structural unit is a regular square frustum, and the bottom is a cuboid with a square cross-section. The sides of the square cross-section are aligned with the bottom edge of the regular square frustum and are of equal length. The first silicon dioxide dielectric layer (3) to the third silicon dioxide dielectric layer (7) are all made of silicon dioxide with a refractive index of 1.5; the metal substrate is made of silver. The upper base of the silicon dioxide regular square truncated pyramid has a side length of 10.9 μm, the lower base of the silicon dioxide regular square truncated pyramid has a side length of 44.1 μm, the height of the silicon dioxide regular square truncated pyramid is 49.1 μm, the thickness of the first silicon dioxide dielectric layer (3) is 11.5 μm, the thickness of the second silicon dioxide dielectric layer (5) is 13.5 μm, the thickness of the third silicon dioxide dielectric layer (7) is 8.0 μm, and the thickness of the metallic silver is 1.0 μm; All graphene layers are connected to an external bias voltage (9). At the same time, the electronic control system controls the absorption intensity of the low-frequency band of the absorber by controlling the external bias voltage. The voltage adjustment range is 0-15V.

2. The quasi-terahertz wave total absorption metasurface absorber according to claim 1, characterized in that, When the external bias voltage is 15V, the absorber can achieve full-band absorption in the 0.5 to 10THz band when terahertz waves are incident.

3. The quasi-terahertz wave total absorption metasurface absorber according to claim 2, characterized in that, When the external bias voltage is set to 0V, which corresponds to 0eV for graphene, the absorption rate decreases by 30% at low frequencies.

4. A quasi-terahertz wave total absorption metasurface absorber according to any one of claims 1-3, characterized in that, The structural units are arranged closely together.

5. The method for preparing a quasi-terahertz wave total absorption metasurface absorber as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) A 1.0 μm thick layer of silver was deposited using electron beam evaporation to form the metal substrate; (2) Silicon dioxide is spin-coated onto the surface of the silver layer and baked to form the third silicon dioxide dielectric layer (7) with a thickness of 8.0 μm; (3) Transfer the graphene layer over the third silicon dioxide dielectric layer (7) to form the third graphene layer; (4) Silicon dioxide is spin-coated onto the surface of the third graphene layer and baked to form the second silicon dioxide dielectric layer (5) with a thickness of 13.5 μm; (5) Transfer the graphene layer over the second silicon dioxide dielectric layer (5) to form the second graphene layer; (6) Silicon dioxide is spin-coated onto the surface of the second graphene layer and baked to form the first silicon dioxide dielectric layer (3) with a thickness of 11.5 μm; (7) Transfer the graphene layer over the first silicon dioxide dielectric layer (3) to form the first graphene layer; (8) A square frustum silicon dioxide layer is fabricated on the surface of the first graphene layer using magnetron sputtering.

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