A frequency-adjustable absorber unit structure, absorber device and preparation method thereof

Abstract

The present invention provides a frequency-adjustable absorber unit structure, an absorber device and a preparation method thereof. The absorber unit structure comprises: a metal structure layer: a groove is provided in the metal structure layer; a liquid crystal structure layer: the liquid crystal structure layer is embedded in the groove; an electrode plate assembly: the electrode plate assembly comprises an upper electrode plate arranged on the top of the metal structure layer and a lower electrode plate arranged on the bottom of the metal structure layer; the upper electrode plate covers the entire top of the metal structure layer and contacts the metal structure layer and the liquid crystal structure layer; the lower electrode plate covers the entire bottom of the metal structure layer and contacts the metal structure layer and the liquid crystal structure layer.

Description

Technical Field

[0001] The present invention relates to the technical field of novel artificial electromagnetic materials, and particularly to a frequency-point adjustable absorber unit structure, an absorbing device and a preparation method thereof. Background Art

[0002] Terahertz waves refer to electromagnetic waves with frequencies in the range of 0.1 - 10 THz and wavelengths in the range of 30 μm - 3 mm. Their frequency range is between the infrared and microwave bands, and they have some properties of both light waves and microwaves. Terahertz waves have the collimation of light waves and good penetration, and have unique advantages in fields such as imaging and detection. Due to the particularity of the terahertz band, there are also various terahertz modulation methods. Commonly used modulation methods can be achieved by controlling the amplitude, phase, pulse length, waveform, spectral and other spatial characteristics of terahertz waves.

[0003] Electromagnetic metamaterials are artificial design of periodic unit structures, whose key dimensions are much smaller than the working wavelength, which is a sub-wavelength structure, so they have extraordinary physical properties that natural materials do not have, and are often used to realize absorbing devices for terahertz waves. However, once the traditional metamaterial absorber is prepared, it can only respond to terahertz waves of a specific wavelength, usually only absorb terahertz waves of a fixed frequency, and can only achieve the absorption of terahertz waves in multiple frequency bands by replacing different absorbing materials, and the application range is limited to a certain extent. Summary of the Invention

[0004] The present invention provides a frequency-point adjustable absorber unit structure, an absorbing device and a preparation method thereof to solve the problem that the traditional metamaterial absorber can only absorb terahertz waves of a fixed frequency.

[0005] According to the first aspect of the present invention, there is provided a frequency-point adjustable absorber unit structure, including:

[0006] A metal structure layer: a groove is provided in the metal structure layer;

[0007] A liquid crystal structure layer: the liquid crystal structure layer is embedded in the groove;

[0008] An electrode plate assembly: the electrode plate assembly includes an upper electrode plate disposed on the top of the metal structure layer and a lower electrode plate disposed on the bottom of the metal structure layer;

[0009] The upper electrode plate covers the entire top of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer;

[0010] The lower electrode plate covers the entire bottom of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer.

[0011] Optionally, the absorber unit structure further includes a top transparent substrate disposed on the upper electrode plate and a bottom transparent substrate disposed at the bottom of the lower electrode plate.

[0012] Optionally, the refractive index n of the liquid crystal structure layer varies in the range of 1.54 - 1.94.

[0013] Optionally, the liquid crystal structure layer is in a cross shape, and the central intersection point of the cross is located at the center of the metal structure layer.

[0014] Optionally, the liquid crystal structure layer includes a first rectangular structure in the horizontal direction and a second rectangular structure in the vertical direction. The first rectangular structure and the second rectangular structure intersect to form a cross shape; and the first rectangular structure and the second rectangular structure are of the same size, and the length of the first rectangular structure and the second rectangular structure is 160 - 180 μm, and the width is 30 - 50 μm.

[0015] Optionally, the shape of the metal structure layer is square, and its side length is 260 - 280 μm.

[0016] Optionally, the liquid crystal structure layer and the metal structure layer have the same thickness, and the thickness is 5 - 25 μm.

[0017] According to a second aspect of the present invention, there is provided a frequency-tunable wave-absorbing device, including an absorber array composed of a plurality of absorber unit structures provided in the first aspect of the present invention.

[0018] Optionally, the absorber array is arranged in an N×N array, where N is a non-zero positive integer.

[0019] According to a third aspect of the present invention, there is provided a method for manufacturing a frequency-tunable absorber unit structure, including:

[0020] Manufacturing a metal structure layer, where a groove is provided in the metal structure layer;

[0021] Embedding a liquid crystal structure layer in the groove;

[0022] Manufacturing an electrode plate assembly, where the electrode plate assembly includes an upper electrode plate disposed on the top of the metal structure layer and a lower electrode plate disposed at the bottom of the metal structure layer; the upper electrode plate covers the entire top of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer; the lower electrode plate covers the entire bottom of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer.

[0023] The absorber unit structure with adjustable frequency points provided by the present invention includes a liquid crystal structure layer and a metal structure layer. The liquid crystal is embedded in the metal structure layer, and by adjusting the voltage between the upper and lower electrodes of the liquid crystal structure layer, the arrangement of liquid crystal molecules is changed, thereby changing the refractive index of the liquid crystal material. It overcomes the defect that only terahertz waves of a specific wavelength can be responded to in the past, and realizes the adjustable absorption frequency points of the metamaterial absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic cross-sectional structure diagram of the metamaterial absorber unit structure provided in an exemplary embodiment of the present invention;

[0026] Figure 2 It is a schematic cross-sectional structure diagram of the metamaterial absorber unit structure provided in another exemplary embodiment of the present invention;

[0027] Figure 3 It is a schematic top view structure diagram of the metamaterial absorber unit structure provided in an exemplary embodiment of the present invention;

[0028] Figure 4 It is a graph of the amplitude response result of the metamaterial absorber unit structure provided in an exemplary embodiment of the present invention;

[0029] Figure 5 It is a schematic structure diagram of an absorber array composed of 3×3 absorber unit structures provided in an exemplary embodiment of the present invention;

[0030] Figure 6 It is a graph of the amplitude response result of an absorber array composed of 3×3 absorber unit structures provided in an exemplary embodiment of the present invention;

[0031] Figure 7 It is a flowchart of the preparation method of the absorber unit structure provided in an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof 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 those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0034] The technical solutions of the present invention will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

[0035] Figure 1 It is a schematic structural diagram of a cross-section of a metamaterial absorber unit structure provided in an exemplary embodiment of the present invention. The absorber unit structure with adjustable frequency points provided by the present invention includes:

[0036] Metal structure layer 2: There are grooves in the metal structure layer 2;

[0037] Liquid crystal structure layer 1: The liquid crystal structure layer 1 is embedded in the groove;

[0038] Electrode plate assembly: The electrode plate assembly includes an upper electrode plate 3 disposed on the top of the metal structure layer 2 and a lower electrode plate 4 disposed on the bottom of the metal structure layer 2;

[0039] The upper electrode 3 plate covers the entire top of the metal structure layer 2 and is in contact with the metal structure layer 2 and the liquid crystal structure layer 1;

[0040] The lower electrode plate 4 covers the entire bottom of the metal structure layer 2 and is in contact with the metal structure layer 2 and the liquid crystal structure layer 1.

[0041] In an embodiment of the present invention, the electrode plate assembly is used to apply an electric field to the liquid crystal structure layer 1. Two parallel electrode plates are respectively covered above and below the liquid crystal structure layer 1. By changing the electric field strength, the voltage between the upper electrode plate 3 and the lower electrode plate 4 is adjusted to change the arrangement of liquid crystal molecules, thereby changing the refractive index of the liquid crystal material.

[0042] As Figure 2 shown, the absorber unit structure further includes a top transparent substrate 5 disposed on the upper electrode plate 3 and a bottom transparent substrate 6 disposed at the bottom of the lower electrode 4 plate.

[0043] An ideal absorbing material needs to meet two conditions: impedance matching characteristics and attenuation characteristics. The impedance matching characteristics and attenuation characteristics are mainly determined by the dielectric constant and magnetic permeability values of the material. The change of the dielectric constant will change the impedance matching characteristics, thereby affecting the absorption effect.

[0044] The refractive index of the liquid crystal material changes with the frequency. When the liquid crystal refractive index n changes, it means that the dielectric constant ε of the medium also changes Thereby, the absorption frequency point of the electromagnetic wave will be changed.

[0045] In one implementation manner of this embodiment, the change range of the refractive index n of the liquid crystal structure layer 1 is 1.54 - 1.94, and the liquid crystal material is 4-cyano-4'-pentylbiphenyl (5CB). Under the irradiation of linearly polarized waves, the electromagnetic wave is coupled with the liquid crystal molecules. By adjusting the orientation of the liquid crystal molecules through voltage, the liquid crystal molecules generate electromagnetic resonance with the electromagnetic wave, loss and absorb the electromagnetic wave.

[0046] In one implementation manner, as Figure 3 shown, the liquid crystal structure layer 1 is in a cross shape, and the central intersection point of the cross is located at the center of the metal structure layer 2.

[0047] In one implementation manner, the liquid crystal structure layer 1 includes a first rectangular structure in the horizontal direction and a second rectangular structure in the vertical direction. The first rectangular structure intersects with the second rectangular structure to form a cross shape; and the first rectangular structure and the second rectangular structure are of the same size. The length a of the first rectangular structure and the second rectangular structure is 160 - 180 μm, and the width w is 30 - 50 μm.

[0048] In one implementation manner, the shape of the metal structure layer 2 is square, and its side length p is 260 - 280 μm.

[0049] The liquid crystal structure layer 1 and the metal structure layer 2 have the same thickness, and the thickness h is 5 - 25 μm.

[0050] In one of the embodiments, as Figure 2 shown, the side length p of the metal structure layer 2 is 270 μm; the liquid crystal structure layer 1 is in a cross shape, where the lengths a of the first rectangular structure and the second rectangular structure are both 170 μm, and the widths w are both 40 μm; the thicknesses h of the liquid crystal structure layer 1 and the metal structure layer 2 are both 15 μm.

[0051] Please refer to Figure 4 , under the irradiation of a linearly polarized wave, when the refractive index n of the liquid crystal structure layer 1 is 1.94, the absorber unit structure realizes efficient absorption of electromagnetic waves at the 0.62 THz frequency point, and the absorbed energy can reach more than 14 dB.

[0052] A wave absorber device with adjustable frequency points provided by this embodiment includes an absorber array composed of several of the above-mentioned absorber unit structures. The absorber array is arranged in an N×N array, where N is a non-zero positive integer.

[0053] In one of the embodiments, please refer to Figure 5 , the absorber array is arranged in a 3×3 array.

[0054] By applying different voltages to the liquid crystal structure layer 1, different refractive indexes are obtained. Please refer to Figure 6 , when the refractive indexes n of the liquid crystal structure layer 1 are 1.52, 1.69, 1.6, 1.55, and 1.94 respectively, the absorber array composed of 3×3 absorber unit structures realizes efficient absorption near the five frequency points of 0.63 THz, 0.67 THz, 0.69 THz, 0.702 THz, and 0.706 THz respectively, and the absorbed energy can reach more than 16 dB.

[0055] It can be seen that in this embodiment, since the liquid crystal material exhibits the property of anisotropy of dielectric constant with respect to the applied electric field, the orientation of liquid crystal molecules can be adjusted by different voltage magnitudes to obtain the refractive index of the liquid crystal molecules, thereby obtaining different resonant frequencies, enabling the liquid crystal molecules to undergo electromagnetic resonance with electromagnetic waves in different frequency bands, and thus realizing adjustable absorption frequency points in the 0.6 - 0.8 THz band range.

[0056] As Figure 7 shown, this embodiment provides a preparation method for an absorber unit structure with adjustable frequency points, including:

[0057] S1: Prepare a metal structure layer, and a groove is provided in the metal structure layer;

[0058] S2: Embed a liquid crystal structure layer in the groove;

[0059] S3: Prepare an electrode plate assembly, where the electrode plate assembly includes an upper electrode plate disposed on the top of the metal structure layer and a lower electrode plate disposed on the bottom of the metal structure layer; the upper electrode plate covers the entire top of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer; the lower electrode plate covers the entire bottom of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency-adjustable absorber unit structure, characterized in that: include: Metal structure layer: the metal structure layer is provided with grooves; Liquid crystal structure layer: the liquid crystal structure layer is embedded in the groove; The refractive index n of the liquid crystal structure layer varies in the range of 1.54-1.94; the liquid crystal structure layer is in a cross shape, and the central intersection of the cross is located at the center of the metal structure layer; Electrode plate assembly: the electrode plate assembly comprises an upper electrode plate disposed on the top of the metal structure layer and a lower electrode plate disposed on the bottom of the metal structure layer; The upper electrode plate covers the entire top of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer; The lower electrode plate covers the entire bottom of the metal structure layer and is in contact with the metal structure layer and the liquid crystal structure layer.

2. The frequency-adjustable absorber unit structure according to claim 1, characterized in that: The absorber unit structure also includes a top transparent substrate arranged on the upper electrode plate and a bottom transparent substrate arranged at the bottom of the lower electrode plate.

3. The frequency-adjustable absorber unit structure according to claim 1, characterized in that: The liquid crystal structure layer includes a first rectangular structure in the horizontal direction and a second rectangular structure in the vertical direction, the first rectangular structure and the second rectangular structure intersect to form a cross shape; and the first rectangular structure and the second rectangular structure are the same size, the length of the first rectangular structure and the second rectangular structure is 160-180μm, and the width is 30-50μm.

4. The frequency-adjustable absorber unit structure according to claim 1, characterized in that: The metal structure layer is in the shape of a square, and the side length thereof is 260-280 μm.

5. The frequency-adjustable absorber unit structure according to claim 1 or 4, characterized in that: The liquid crystal structure layer and the metal structure layer have the same thickness, which is 5-25 μm.

6. A frequency-adjustable wave absorbing device, characterized in that: The invention relates to a wave absorber array comprising a plurality of wave absorber unit structures as claimed in any one of claims 1 to 3.

7. The frequency-adjustable absorbing device according to claim 6, characterized in that: The absorber array is arranged in an N×N array, wherein N is a non-zero positive integer.

8. A method for preparing a frequency-adjustable absorber unit structure, characterized in that: Used to prepare the frequency-adjustable absorber unit structure as claimed in any one of claims 1 to 5, the preparation method comprising: preparing a metal structural layer, wherein the metal structural layer is provided with a groove; embedding a liquid crystal structure layer in the groove; An electrode plate assembly is prepared, wherein the electrode plate assembly includes an upper electrode plate arranged on the top of the metal structure layer and a lower electrode plate arranged on the bottom of the metal structure layer; the upper electrode plate covers the entire top of the metal structure layer and contacts the metal structure layer and the liquid crystal structure layer; the lower electrode plate covers the entire bottom of the metal structure layer and contacts the metal structure layer and the liquid crystal structure layer.

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