Metamaterial non-reciprocal absorber based on lying structure

Abstract

The invention discloses a metamaterial non-reciprocal absorber based on a'lying 'structure, a conductive patch is attached to the side surface, a supporting surface is made of polyimide, a layer of substrate is arranged above and below the structure, the absorber comprises a substrate and a'lying' metal unit array periodically arranged on the surface of the substrate, the inclination angles of the metal units are continuously increased in the preset direction, through asymmetric distribution of space angles, forward incident electromagnetic waves and the metal units generate strong coupling absorption, reverse incident electromagnetic waves are high in transmission due to weakening of the coupling effect and air waveguide, and efficient non-reciprocal response can be achieved without an external magnetic field. According to the invention, the structure is in a lying type and has the characteristics of high integration level, nonreciprocity, broadband response and the like, the working bandwidth can reach ten times of frequency, and the device can be applied to scenes of flexible electronics, on-chip optical communication, ultrathin radar stealth coatings and the like.

Description

Technical Field

[0001] The present invention relates to the field of non-reciprocity and electromagnetic regulation, and in particular to a metamaterial non-reciprocal absorber based on a "lying-down" structure. Background Art

[0002] In the field of electromagnetic functional devices, the realization of nonreciprocal absorption properties is of great significance for communication, sensing, and imaging systems in microwave and terahertz frequency bands. Traditional reciprocal devices struggle to meet requirements for one-way information transmission and anti-interference protection. Nonreciprocal absorption devices enable efficient forward absorption of electromagnetic waves and low-loss reverse transmission. In communication systems, they can serve as one-way signal isolators, preventing reflected waves from impacting the transmitter and causing frequency pull. In sensing, directional absorption / transmission properties can enhance the contrast between target signals and background noise, improving detection sensitivity. In stealth technology, they can selectively absorb enemy detection waves (such as radar waves) while transmitting friendly communication waves, achieving the dual functions of "covert communication + active stealth." Therefore, these devices have great application value in core areas such as 5G / 6G millimeter-wave communications, terahertz imaging, and national defense counter-reconnaissance.

[0003] After searching, it was found that the Chinese patent with publication number CN115084813A disclosed a sub-wavelength-sized wide-spectrum non-reciprocal emission / absorption device on March 28, 2023, which selected multiple layers of near-zero magnetic dielectric constant materials as the absorption layer, and selected high-reflection materials of the corresponding band as the base layer; the wavelength position of the multiple layers of near-zero magnetic dielectric constant materials was gradually changed from the bottom layer to the top layer.

[0004] This demonstrates that operating bandwidth is a crucial metric for nonreciprocal absorbers. While conventional nonreciprocal absorbers cannot achieve perfect absorption and transmission, the nonreciprocal absorber in this design achieves both at specific angles and within an ultra-wideband. Furthermore, this absorption and transmission does not require a conventional external magnetic field, making it more suitable for integrated applications. Compared to the aforementioned patent, this structure does not require the assistance of an external magnetic field, achieving an operating bandwidth of up to ten times the frequency. Summary of the Invention

[0005] To overcome the shortcomings of the aforementioned technologies, the present invention provides a metamaterial nonreciprocal absorber based on a "lying-down" structure. This nonreciprocal absorber, leveraging its unique "lying-down" layout, achieves nonreciprocity by manipulating the propagation behavior of electromagnetic waves. Its core principle lies in utilizing metal layers with increasing tilt angles to alter the coupling between the electromagnetic wave and the structure, as well as the energy attenuation process.

[0006] The present invention is achieved through the following technical solutions:

[0007] A metamaterial non-reciprocal absorber based on a "lying down" structure includes a "lying down" metal unit array, wherein the metal unit array is composed of a plurality of metal units periodically arranged by inclined layers, the height and tilt angle of the metal units are in an increasing trend, and through the asymmetric distribution of spatial angles, the forward incident electromagnetic wave and the metal units produce strong coupling absorption, while the reverse incident electromagnetic wave is highly transmitted due to the weakening coupling effect and air waveguide, and an efficient non-reciprocal response can be achieved without an external magnetic field; specifically, there are 15 metal units, and each metal unit is composed of six inclined layers, and the inclined layers are composed of indium tin oxide (Ito)-calcium fluoride (CaF2)-air cavities arranged in sequence, and each metal unit ends with indium tin oxide; each metal unit is arranged with a certain air cavity thickness.

[0008] Furthermore, by utilizing the characteristic that the overall structure extends in the horizontal direction, the coupling area between the metal layer and the electromagnetic wave is increased, the asymmetry brought by the non-diagonal component of the dielectric tensor is strengthened, and the increasing inclination angle enables the metal layer to selectively couple with electromagnetic waves of different frequencies; for an electromagnetic wave of a certain frequency, the coupling degree between the metal layers with different inclination angles is different, and the increasing arrangement of the inclination angles ensures that within a wide frequency range, there is always a metal layer with a corresponding inclination angle that can achieve a strong coupling state with the electromagnetic wave of a specific frequency.

[0009] Furthermore, when electromagnetic waves are incident obliquely through the air, the spatial asymmetry of the dielectric constant controls the imaginary part of the longitudinal wave vector of the electromagnetic wave, so that the forward incident energy is absorbed due to strong coupling and high loss, and the reverse incident energy is transmitted due to weak coupling and low loss, realizing the non-reciprocal phenomenon; the angle increase covers wide-band matching and expands the absorption bandwidth.

[0010] Furthermore, when the electromagnetic wave is incident at an angle of 55 degrees from the normal, the structure exhibits ultra-wideband non-reciprocity, with an operating bandwidth of 19.27thz to 197thz, a bandwidth of ten times the frequency.

[0011] Furthermore, the structure is effective for x-polarized electromagnetic waves.

[0012] Furthermore, Ito is prepared by magnetron sputtering, CaF2 is prepared by molecular beam epitaxy, Ito is described by the Drude model, and CaF2 is described by the Sellmeier dispersion model.

[0013] Furthermore, 15 metal units are periodically arranged at an inclination angle of 40 to 59 degrees, with the height increasing by 200 nm, wherein the inclination angle increases by 1 degree, and the air cavity thickness between the metal units is maintained at 330 to 3000 nm.

[0014] Furthermore, the thickness of a single layer of indium tin oxide is 5 nm, the thickness of a single layer of calcium fluoride is 5 nm, and the thickness of a single layer of air cavity is 44 nm.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] (1) The present invention utilizes a lying structure to expand the coupling between electromagnetic waves and the structure, superimpose multiple absorption peaks, and widen multiple absorption bandwidths.

[0017] (2) The height and tilt angle of the present invention change incrementally, increasing the asymmetry of the dielectric constant and allowing high-frequency and low-frequency electromagnetic waves to couple simultaneously in the structure.

[0018] (3) The present invention is effective for y-polarized electromagnetic waves.

[0019] (4) The maximum size of the present invention reaches the micron level, which realizes the miniaturization of the device and is suitable for industrial integration

[0020] (5) The present invention does not require an external magnetic field and is suitable for a variety of industrial application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 2 is a structural diagram of a metamaterial non-reciprocal absorber based on a “lying-down” structure according to an embodiment of the present invention.

[0022] Figure 2 Schematic diagram of the metal unit structure in a metamaterial non-reciprocal absorber based on a “lying down” structure according to an embodiment of the present invention.

[0023] Figure 3 2 is a main diagram of a metamaterial non-reciprocal absorber based on a “lying-down” structure according to an embodiment of the present invention.

[0024] Figure 4 Graph showing the non-reciprocal phenomenon of a metamaterial non-reciprocal absorber based on a “lying-down” structure according to an embodiment of the present invention.

[0025] List of reference numerals:

[0026] 1-metal unit, 2-substrate, 3-support plate, 4-conductive patch 1, 5-conductive patch 2. DETAILED DESCRIPTION

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

[0028] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0029] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which this invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such, will not be interpreted in an idealized or overly formal sense.

[0030] The present invention is a metamaterial non-reciprocal absorber based on a "lying down" structure, such as Figure 1 As shown, it includes a main body and a support structure. The main body is a "lying down" metal unit array, composed of multiple metal units 1 arranged periodically in inclined layers. The support structure includes a base plate 2 arranged vertically, an I-shaped plate arranged on the left and right, and a support plate 3 placed on the rear side. All are made of polyimide. The I-shaped plate on the side is affixed with conductive patches (4, 5). In the present invention, electromagnetic waves are obliquely incident from air into this absorber, resulting in perfect absorption and transmission in both the forward and backward directions.

[0031] The metal unit of the absorber, such as Figure 2 As shown, the thickness of a single layer of indium tin oxide is 5.1 nm, the thickness of a single layer of calcium fluoride is 5 nm, and the thickness of a single layer of air cavity is 44 nm, forming a basic tilted layer structure. Six tilted layers form a metal unit, and each metal unit ends with indium tin oxide.

[0032] The absorber base structure, such as Figure 3 As shown, the 15 units are arranged in a height increment of 200 nm, and the tilt angles increase successively.

[0033] Non-reciprocal phenomena, such as Figure 4 As shown, when electromagnetic waves are incident at an oblique angle in the TM mode, electromagnetic waves with frequencies of 19.27thz to 197thz will exhibit obvious non-reciprocal phenomena, with both the forward absorptivity and the backward transmittance reaching above 0.9.

[0034] After a specific design (based on a "lying-down" structure), the present invention can realize the function of non-reciprocal transmission. The present invention has higher absorptivity, higher transmittance and wider working bandwidth.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A metamaterial non-reciprocal absorber based on a "lying down" structure, characterized in that: The invention comprises a "lying down" metal unit array, which is composed of a plurality of metal units periodically arranged by inclined layers. The height and inclination angle of the metal units are in an increasing trend. Through the asymmetric distribution of spatial angles, the forward incident electromagnetic wave and the metal unit produce strong coupling absorption, and the reverse incident electromagnetic wave is highly transmitted due to the weakening of the coupling effect and the air waveguide, so that efficient non-reciprocal response can be achieved without an external magnetic field. Specifically, there are 15 metal units, and each metal unit is composed of six inclined layers. The inclined layers are composed of indium tin oxide-calcium fluoride-air cavities arranged in sequence, and each metal unit ends with indium tin oxide. Each metal unit is arranged with a certain air cavity thickness.

2. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: By utilizing the characteristic that the overall structure extends in the horizontal direction, the coupling area between the metal layer and the electromagnetic wave is increased, the asymmetry brought by the non-diagonal component of the dielectric tensor is strengthened, and the increasing inclination angle enables the metal layer to selectively couple with electromagnetic waves of different frequencies; for an electromagnetic wave of a certain frequency, the coupling degree between the metal layers with different inclination angles is different, and the increasing arrangement of the inclination angles ensures that within a wide frequency range, there is always a metal layer with the corresponding inclination angle that can achieve a strong coupling state with the electromagnetic wave of a specific frequency.

3. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: When electromagnetic waves are incident obliquely through the air, the spatial asymmetry of the dielectric constant controls the imaginary part of the longitudinal wave vector of the electromagnetic wave, so that the forward incident energy is absorbed due to strong coupling and high loss, and the reverse incident energy is transmitted due to weak coupling and low loss, realizing the non-reciprocal phenomenon; the angle increase covers wide-band matching and expands the absorption bandwidth.

4. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: When the electromagnetic wave is incident at an angle of 55 degrees from the normal, the structure exhibits ultra-wideband non-reciprocity phenomenon, with an operating bandwidth of 19.27thz to 197thz, a bandwidth of ten times the frequency.

5. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: The absorber is effective for x-polarized electromagnetic waves.

6. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: Indium tin oxide is prepared by magnetron sputtering, calcium fluoride is prepared by molecular beam epitaxy, indium tin oxide is described by the Drude model, and calcium fluoride is described by the Sellmeier dispersion model.

7. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: The 15 metal units are periodically arranged at an inclination angle of 40 to 59 degrees, with their height increasing by 200 nm and the inclination angle increasing by 1 degree. The air cavity thickness between the metal units is maintained at 330 to 3000 nm.

8. The metamaterial non-reciprocal absorber based on a "lying-down" structure according to claim 1, characterized in that: The thickness of a single layer of indium tin oxide is 5nm, the thickness of a single layer of calcium fluoride is 5nm, and the thickness of a single layer of air cavity is 44nm.

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