A tunable terahertz metamaterial absorber

Abstract

The present invention relates to a tunable terahertz metamaterial absorber, which relates to the fields of metamaterials and liquid crystal technology. The absorber comprises: a plurality of periodically arranged absorbing units; each absorbing unit comprises a first substrate, a metal pattern, liquid crystal, a three-dimensional metal structure, a metal film, and a second substrate; the liquid crystal is disposed between the first and second substrates; the metal pattern is disposed between the first substrate and the liquid crystal and attached to the first substrate; the metal film is disposed between the second substrate and the liquid crystal and attached to the second substrate; and the three-dimensional metal structure is embedded in the liquid crystal. The present invention can achieve high absorption and wide-angle incidence.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterials and liquid crystals, and in particular to a tunable terahertz metamaterial absorber. Background Art

[0002] Metamaterials are a new type of subwavelength artificial composite structure or material that possesses physical properties not found in natural materials, such as negative refractive index and inverse Doppler effect. Over the years, metamaterial research has developed numerous applications. Liquid crystals are an important candidate for the development of actively tunable photonic devices. They exhibit excellent broadband optical anisotropy and electro-optical and magneto-optical modulation properties. Liquid crystals are one of the few materials that exhibit high birefringence, low absorption loss, and a large phase shift tuning range in the terahertz band. Consequently, liquid crystals and metamaterials have garnered widespread attention. Currently, researchers have proposed numerous liquid crystal metamaterial absorbing structures, but these structures still suffer from shortcomings in absorbing wide-angle incident waves. Summary of the Invention

[0003] The purpose of the present invention is to provide a tunable terahertz metamaterial absorber to achieve high absorption and wide-angle incidence.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A tunable terahertz metamaterial absorber comprises: a plurality of periodically arranged absorbing units; each of the absorbing units comprises a first substrate, a metal pattern, liquid crystal, a three-dimensional metal structure, a metal film, and a second substrate;

[0006] The liquid crystal is arranged between the first substrate and the second substrate; the metal pattern is arranged between the first substrate and the liquid crystal and attached to the first substrate; the metal film is arranged between the second substrate and the liquid crystal and attached to the second substrate; and the three-dimensional metal structure is embedded in the liquid crystal.

[0007] Optionally, the three-dimensional metal structure is a centrosymmetrical cross metal structure rotated 45 degrees, and the cross metal structure includes a first side and a second side; the first side and the second side are perpendicular.

[0008] Optionally, the metal pattern is a centrally symmetrical pattern; the metal pattern includes a first square and four second squares; each vertex of the first square is connected to a vertex of the second square; the centers of the two second squares on the diagonal of the first square are on the same straight line as the center of the first square.

[0009] Optionally, the center of the metal pattern coincides with the center of the three-dimensional metal structure.

[0010] Optionally, the metal pattern, the three-dimensional metal structure and the metal film are all made of copper.

[0011] Optionally, the first substrate and the second substrate are both quartz glass substrates.

[0012] Optionally, the first substrate and the second substrate are both cubes.

[0013] Optionally, the dielectric constant of the quartz glass substrate is 3.75, and the loss tangent value of the quartz glass substrate is 0.0004.

[0014] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0015] In the present invention, the liquid crystal is disposed between the first and second substrates; the metal pattern is disposed between the first substrate and the liquid crystal and attached to the first substrate; the metal film is disposed between the second substrate and the liquid crystal and attached to the second substrate; and the three-dimensional metal structure is embedded between the liquid crystals. The present invention utilizes the three-dimensional metal structure embedded in the liquid crystal to form a three-dimensional resonant structure, which produces a strong resonant response to electromagnetic waves at various incident angles. This allows the absorber to maintain an absorption effect even at large incident angles, achieving high absorption and wide-angle incidence. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the three-dimensional structure of a liquid crystal-based tunable terahertz metamaterial absorber according to an embodiment of the present invention;

[0018] Figure 2 is a top view of a metal pattern according to an embodiment of the present invention;

[0019] Figure 3 A top view of a three-dimensional metal structure according to an embodiment of the present invention;

[0020] Figure 4 A side view of an embodiment of the present invention;

[0021] Figure 5 Graph showing the absorption rate simulation results of an embodiment of the present invention when the liquid crystal dielectric constants are 2.8, 3.0, 3.2, 3.4, and 3.6;

[0022] Figure 6 This is a graph showing the absorptivity simulation results of an embodiment of the present invention at an oblique incidence angle of 45° and a liquid crystal dielectric constant of 3.0;

[0023] Figure 7 This is a graph showing the absorptivity simulation results of an embodiment of the present invention at an oblique incidence angle of 70° and a liquid crystal dielectric constant of 3.0;

[0024] Figure 8 1 is a diagram showing the absorption rate simulation results of an embodiment of the present invention under oblique incidence at an incident angle of 80° and a liquid crystal dielectric constant of 3.0.

[0025] Explanation of symbols:

[0026] 1-first substrate, 2-second substrate, 3-metal pattern, 4-three-dimensional metal structure, 5-liquid crystal, 6-metal film. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] The purpose of the present invention is to provide a tunable terahertz metamaterial absorber to achieve high absorption and wide-angle incidence.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 and Figure 4 As shown, the present invention provides a tunable terahertz metamaterial absorber, comprising: a plurality of periodically arranged absorbing units, specifically absorbing units arranged in a continuous period; each of the absorbing units comprises a first substrate 1, a metal pattern 3, a liquid crystal 5, a three-dimensional metal structure 4, a metal film 6 and a second substrate 2.

[0031] The liquid crystal 5 is disposed between the first substrate 1 and the second substrate 2; the metal pattern 3 is disposed between the first substrate 1 and the liquid crystal 5 and attached to the first substrate 1; the metal film 6 is disposed between the second substrate 2 and the liquid crystal 5 and attached to the second substrate 2. Specifically, the metal pattern 3 is attached to the lower surface of the first substrate 1, and the three-dimensional metal structure 4 and the metal film 6 are attached to the upper surface of the second substrate 2. The three-dimensional metal structure 4 is embedded in the liquid crystal 5. Since the liquid crystal 5 is filled between the first substrate 1 and the second substrate 2, the three-dimensional metal structure 4 appears to be embedded in the liquid crystal 5.

[0032] As an optional embodiment, the three-dimensional metal structure 4 is a centrosymmetric cross metal structure rotated 45 degrees, and the cross metal structure includes a first side and a second side; the first side and the second side are perpendicular. The three-dimensional metal structure 4 is an oblique cross symmetrical structure. The length, width and height of each oblique cross in the three-dimensional metal structure 4 are the same and are rotated 45 degrees. The liquid crystal 5 is a cube as a whole, with a side length of x and a thickness of h2. The three-dimensional metal structure 4 is obtained by rotating the centrosymmetric right cross 45 degrees, as shown in FIG. Figure 3 As shown, the cross width is w7, the cross length is w8, and the thickness is h3.

[0033] As an optional embodiment, the metal pattern 3 is a centrally symmetrical pattern; the metal pattern 3 includes a first square and four second squares; each vertex of the first square is connected to a vertex of the second square; the centers of the two second squares on the diagonal of the first square are on the same straight line as the center of the first square. The metal pattern 3 is obtained by the centrally symmetrical squares, such as Figure 2 As shown, the distance between the two large squares in the middle is w1, the side length of the large square is w3, and the distance between the large square and the edge is w5. The distance between the small square and the edge is w6. The distance between two small squares in the same pattern is w4, and the distance between small squares in different patterns is w2.

[0034] As an optional implementation, the center of the metal pattern 3 coincides with the center of the three-dimensional metal structure 4 .

[0035] As an optional implementation, the metal pattern 3 , the three-dimensional metal structure 4 and the metal film 6 are all made of copper.

[0036] As an optional embodiment, the first substrate 1 and the second substrate 2 are both quartz glass substrates. Both the first substrate 1 and the second substrate 2 are cubic. The two substrates are a cube with a side length of x and a thickness of h1. The dielectric constant of the quartz glass substrate is 3.75, and the loss tangent of the quartz glass substrate is 0.0004.

[0037] In practical applications, the metal film 6, the liquid crystal 5 and the quartz glass substrate have the same size. The metal film 6 and the metal pattern 3 are a square film with a side length of x.

[0038] In actual application, the metal film 6 and the three-dimensional metal structure 4 are integrally printed by micro-jet printing technology; the metal pattern 3 is produced by coating, photolithography and chemical etching; and the liquid crystal 5 is injected into the gap between the metal film 6 and the metal pattern 3 by a filling machine.

[0039] Settings in specific applications:

[0040] The periodic dimension of the absorbing element is x = 400 μm. The distance between each large square in the center of metal pattern 3 is w1 = 140 μm. The side length of each large square is w3 = 60 μm, and the distance from each large square to the edge is w5 = 70 μm. The distance between each small square to the edge is w6 = 40 μm. The distance between two small squares in the same pattern is w4 = 50 μm, while the distance between small squares in different patterns is w2 = 80 μm. The cross in the three-dimensional metal structure 4 has a width of w7 = 50 μm, a length of w8 = 150 μm, and a height of h3 = 35 μm.

[0041] The thickness of the first substrate 1 and the second substrate 2 is h1 = 400 μm, the dielectric constant is 3.75, and the loss tangent value is 0.0004; the thickness of the metal film 6 and the metal pattern 3 is 0.05 μm and is made of copper; the dielectric constant of the liquid crystal 5 is 2.8-3.6.

[0042] Figure 5 The following figure shows the absorption rate of an absorber simulated by software under normal electromagnetic wave incidence. When the dielectric constant of the liquid crystal changes from 2.8 to 3.6, the absorption peak shifts leftward from 412.32 GHz to 376.6 GHz.

[0043] Figure 6 、 Figure 7 、 Figure 8 The following are the absorption rate simulation structures of electromagnetic waves at incident angles of 45°, 70°, and 80° respectively. Figure 6-Figure 8 It can be seen from the figure that the present invention still has a very high absorption effect under these incident angles. Even when the incident angle is 80°, the absorption rate can still reach 85%.

[0044] The present invention uses a resonant structure formed by a three-dimensional metal structure embedded in liquid crystal. When the dielectric constant of the liquid crystal changes from 2.8 to 3.6, the absorption peak shifts left from 412.32 GHz to 376.6 GHz. The three-dimensional resonant structure can produce a strong resonant response to electromagnetic waves at different incident angles, so the absorber still has an absorption effect when incident at large angles. The tunable terahertz metamaterial absorber provided by the present invention is a symmetrical structure that can absorb electromagnetic waves of any polarization angle and electromagnetic waves of different polarization types. The absorber provided by the present invention is designed based on the characteristics of liquid crystal and has the characteristics of high absorption, wide-angle incidence, and polarization insensitivity. The absorber structure provided by the present invention is obtained through parameter optimization and can produce better resonance. Changes in size will weaken or even eliminate the resonance.

[0045] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0046] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the device and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A tunable terahertz metamaterial absorber, characterized in that: include: A plurality of periodically arranged absorbing units; each of the absorbing units comprises a first substrate, a metal pattern, a liquid crystal, a three-dimensional metal structure, a metal film, and a second substrate; The liquid crystal is disposed between the first substrate and the second substrate; the metal pattern is disposed between the first substrate and the liquid crystal and attached to the first substrate; the metal film is disposed between the second substrate and the liquid crystal and attached to the second substrate; the three-dimensional metal structure is embedded in the liquid crystal; The three-dimensional metal structure is a centrally symmetrical cross metal structure rotated 45 degrees, and the cross metal structure includes a first side and a second side; the first side and the second side are perpendicular; The metal pattern is a centrally symmetrical pattern; the metal pattern includes a first square and four second squares; each vertex of the first square is connected to a vertex of the second square; the centers of the two second squares on the diagonal of the first square are located on the same straight line as the center of the first square.

2. The tunable terahertz metamaterial absorber according to claim 1, characterized in that: The center of the metal pattern coincides with the center of the three-dimensional metal structure.

3. The tunable terahertz metamaterial absorber according to claim 1, characterized in that: The metal pattern, the three-dimensional metal structure and the metal film are all made of copper.

4. The tunable terahertz metamaterial absorber according to claim 1, characterized in that: The first substrate and the second substrate are both quartz glass substrates.

5. The tunable terahertz metamaterial absorber according to claim 1, characterized in that: The first substrate and the second substrate are both in the shape of cubes.

6. The tunable terahertz metamaterial absorber according to claim 4, characterized in that: The dielectric constant of the quartz glass substrate is 3.75, and the loss tangent value of the quartz glass substrate is 0.0004.

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