An ultralens with staggered asymmetric double-opened metasurface unit

Abstract

The application relates to an ultralens with staggered asymmetric double-opening metasurface units, belonging to the technical field of metasurfaces, and comprising an outer first layer, an upper layer medium, a middle layer, a lower layer medium and an outer second layer which are attached in sequence, wherein the outer first layer, the middle layer and the outer second layer are each provided with a plurality of groups of metasurface units which are spaced apart in an elliptical shape, and each metasurface unit is an asymmetric double-opening inner-outer distributed circular ring; the opening directions of the metasurface units in the outer first layer and the outer second layer are the same, and the opening directions of the inner rings of the metasurface units in the middle layer are mirror-symmetrical, so that the application has the advantages of realizing greater freedom of incident electromagnetic wave regulation and control, and significantly enhancing the transmission performance of the designed units.

Description

Technical Field

[0001] This invention relates to the field of metasurface technology, and more particularly to a superlens with staggered asymmetric double-opening metasurface units. Background Technology

[0002] Metasurfaces are quasi-two-dimensional metamaterials or metastructures that arrange artificially designed unit arrays on a subwavelength-scale plane to achieve flexible control over the amplitude, phase, and polarization of electromagnetic waves. In recent years, metasurface technology has experienced unprecedented development. Thanks to its flexible artificial design, various novel metastructures have emerged, providing an effective solution to the challenges of miniaturization, integration, and low-cost design of traditional devices. Metasurface lenses (or metalens) achieve the interconversion between plane electromagnetic waves and spherical waves by designing arrays with gradually varying refractive index gradients. Representing an important direction in the development and application of many metasurface technologies, they have significant application prospects in optical imaging, sensing, communication, and microwave antennas.

[0003] High-performance metalenses, especially those with high-efficiency focusing, are an important direction in the research and development of high-quality metasurface devices. In the optical and infrared bands, high transmittance transmission is mainly achieved through the design of all-dielectric metasurface units with high refractive index. However, in low-frequency bands such as microwaves, most metalens designs employ multi-layer metallic structures. However, current metallic metasurface units also face drawbacks such as low transmittance or limited phase modulation range. Simultaneously achieving 50% transmittance and full-space phase modulation requires at least three transmission units. Four-layer structures offer even higher transmittance and greater freedom in phase modulation, but metalenses designed with three or four units are thicker and heavier, have higher manufacturing costs, and are more complex to assemble and test. Furthermore, array structures achieving 360° transmission phase coverage with fewer than two units experience a significant decrease in transmittance under certain parameters, typically less than 50%.

[0004] Therefore, to address the above shortcomings, it is necessary to provide a superlens with staggered asymmetric double-aperture metasurface units. Summary of the Invention

[0005] (a) Technical problems to be solved The technical problem to be solved by the present invention is to address the issues of low transmittance or small phase modulation range of current superlenses.

[0006] (II) Technical Solution To address the aforementioned technical problems, this invention provides a superlens with staggered asymmetric double-aperture metasurface units, comprising an outer layer, an upper dielectric layer, an intermediate layer, a lower dielectric layer, and an outer second layer attached sequentially. Each of the outer layer, intermediate layer, and outer second layer has several groups of elliptically spaced metasurface units, each of which is an asymmetric double-aperture inner and outer ring. The opening directions of the metasurface units in the outer layer and outer second layer are the same, while the opening direction of the inner ring of the metasurface units in the intermediate layer is mirror-symmetrical.

[0007] As a further explanation of the present invention, preferably, the metasurface unit phases of the outer layer, the middle layer, and the outer second layer are elliptically distributed. The distribution satisfies: in, The operating wavelength; , Coordinates; Let be the eccentricity of the ellipse; The focal length of the lens; This is the compensation value.

[0008] As a further explanation of the present invention, preferably, the compensation value satisfy: in The angle of deflection of the inner ring opening relative to the outer ring opening of the metasurface unit.

[0009] As a further explanation of the present invention, preferably, the outer layer, the middle layer and the outer second layer are all metal layers, the upper medium is made of Teflon and the lower medium is made of glass.

[0010] As a further explanation of the present invention, preferably, the dielectric constant of the upper dielectric is 2.1 and the dielectric constant of the lower dielectric is 4.5.

[0011] As a further explanation of the present invention, preferably, the thickness of both the upper and lower dielectric layers is 0.08 mm. .

[0012] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention employs a double-aperture resonant ring unit with alternating inner and outer rings, introducing asymmetry to further increase the degrees of freedom for controlling incident electromagnetic waves using traditional double-layer periodic units. Applying the alternating three-layer double-aperture resonant ring unit to the design of planar microwave lenses, by continuously increasing the rotation angle of the alternating inner and outer rings, can simultaneously increase the absolute energy and focusing efficiency of far-field focusing. Therefore, it provides an innovative solution for the design of lower-thickness, high-performance double-layer metasurface units and low-cost, high-efficiency planar miniaturized microwave lenses. Attached Figure Description

[0013] Figure 1 This is a side view of the present invention; Figure 2 This is a front view of the present invention; Figure 3 This is a diagram of the outer layer unit of the present invention; Figure 4 This is a diagram of the middle layer unit of the present invention.

[0014] In the diagram: 1. Outer layer; 11. Outer unit; 2. Upper medium; 3. Middle layer; 31. Middle unit; 4. Lower medium; 5. Outer second layer. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to 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 those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] A superlens with staggered asymmetric double-aperture metasurface units, combined with Figure 1 , Figure 2 The system comprises, in sequence, an outer layer 1, an upper dielectric layer 2, an intermediate layer 3, a lower dielectric layer 4, and an outer second layer 5. Each of the outer layer 1, intermediate layer 3, and outer second layer 5 has several groups of elliptically spaced metasurface units. Each of these layers is a very thin double-layer metal unit; generally, to increase the transmittance of the incident electromagnetic wave, the metal layer thickness is very thin, negligible compared to the wavelength. The thickness and type of the upper dielectric layer 2 and lower dielectric layer 4 are rationally selected according to the designed operating frequency and bandwidth, such as Teflon, glass, or foam. Preferably, the upper dielectric layer 2 is made of Teflon, and the lower dielectric layer 4 is made of glass. The operating frequency decreases as the dielectric constant ε of the filling medium increases. Preferably, the dielectric constant of the upper dielectric layer 2 is 2.1, and the dielectric constant of the lower dielectric layer 4 is 4.5. The thickness of both the upper dielectric layer 2 and the lower dielectric layer 4 is 0.08 mm. ,in This is the operating wavelength.

[0017] Combination Figure 2 , Figure 3 Each metasurface unit on the outer layer 1, middle layer 3, and outer second layer 5 is an asymmetric double-opening inner and outer ring. The opening directions of the metasurface units in outer layer 1 and outer second layer 5 are the same, while the opening direction of the inner ring of the metasurface unit in middle layer 3 is mirror-symmetrical to that of the inner ring in outer layer 1 or outer second layer 5. The opening curvature of the inner and outer rings is the same relative to the center, both being α (α < 90°). Reasonable selection and optimization of the outer and inner ring dimensions can result in a higher transmittance within the operating frequency bandwidth. The symmetrical, non-staggered inner and outer rings with curved slots are arranged symmetrically along the same center. To achieve 360° transmission phase coverage for the double-layer metal metasurface unit, high transmittance transmission is achieved by changing the size of the inner ring. However, the transmittance of the symmetrical double-opening resonant ring unit is very low when the inner ring radius varies greatly, and the focusing energy and focusing efficiency of the designed phase gradient-gradient planar microwave lens are also relatively low.

[0018] Combination Figure 3 , Figure 4 The staggered double-layer double-opening resonant ring unit structure of this invention breaks the original left-right symmetry of the structure by rotating the inner ring. That is, the slotted structure of the left and right outer rings remains unchanged, still symmetrical along the central axis, while the left and right slots of the inner ring rotate simultaneously along the central line at an arc β, resulting in an asymmetrical arrangement of the entire double-opening resonant ring unit along the central line. The upper and lower metal layers of the double-layer metal metasurface structure are identical, both achieving asymmetrical transmission through inner ring rotation. This twisted arrangement of the inner and outer rings further increases the degree of freedom of the double-layer metal metasurface unit in controlling the incident electromagnetic wave. Within the designed frequency band, increasing the resonant electric field transmission of the inner ring unit further increases the transmission transmittance and the interaction bandwidth, while the slope of the transmission phase change with frequency becomes flatter within the period. Therefore, it is also beneficial to further increase the average transmittance of the phase-gradient periodic unit array, and the focusing energy and focusing efficiency of the designed planar microwave lens are also significantly improved.

[0019] The staggered double-layer double-opening metal resonant ring unit structure of this invention significantly improves the transmission performance of its periodic units by breaking the original left-right symmetry through inner ring rotation. Counterclockwise rotation of the inner ring increases the average transmittance of the upper sideband within the passband, while the transmission performance of the lower sideband remains essentially unchanged. Therefore, the 1dB transmission bandwidth of the double-layer unit structure can be further increased by the inner ring rotation angle. Simultaneously, the inner ring rotation increases the resonant frequency point of the unit and further enhances the resonant transmission electric field. The asymmetry increases the control range of the transmission phase, and the slope of the periodic phase with frequency becomes increasingly flat with the rotation angle, resulting in better phase smoothness of the unit. This also contributes to further improving the performance of planar microwave ultrathin lenses based on phase gradient-varying periodic arrays.

[0020] Based on the above metasurface unit structure, such as Figure 2 As shown, this invention combines them into an elliptical phase gradient array, where the major axis is along the x-axis and the minor axis is along the y-axis. This is to adapt to focusing requirements in different dimensions, such as beamforming in microwave communication and multi-angle detection in radar. The outer layer 1, the middle layer 3, and the outer second layer 5 contain elliptical distributed metasurface units for phase distribution. The distribution satisfies: in, The operating wavelength; , Coordinates; Let be the eccentricity of the ellipse; The focal length of the lens; The compensation value is as follows:

[0021] in The deflection angle of the inner ring opening relative to the outer ring opening of the metasurface unit is given. A phase correction term is added to compensate for the phase deviation of the three-layer electric field coupling.

[0022] This invention designs an elliptical array that achieves asymmetric beam output by independently optimizing the phase gradient and element density along the major and minor axes. Furthermore, by aligning the "energy concentration direction" of the phase gradient with the major axis, more energy is confined to the target direction (major or minor axis), reducing energy scattering losses in non-target directions. Adjusting the major / minor axis ratio also achieves a dual "form-performance" match with the asymmetric system. Moreover, it can "directionally narrow the beam in interference-prone directions," reducing the reception of interference signals. Independent optimization of the phase gradient along the major and minor axes makes the impact of local element errors on overall performance more controllable and provides stronger fault tolerance.

[0023] In summary, this invention, through the design of a three-layer symmetrical staggered corner unit and an elliptical phase gradient array, not only has the advantages of being ultra-thin and low-cost, but also significantly improves transmittance, bandwidth, focusing efficiency, and adaptability to multiple scenarios. It solves the limitations of wideband phase drift and single focusing direction, and provides a higher-performance metasurface lens solution for microwave imaging, communication, radar and other fields.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A superlens with staggered asymmetric double-aperture metasurface units, characterized in that: The system includes an outer layer (1), an upper medium (2), an intermediate layer (3), a lower medium (4), and an outer second layer (5) attached sequentially. Each of the outer layer (1), the intermediate layer (3), and the outer second layer (5) has several sets of elliptically spaced metasurface units. Each metasurface unit is an asymmetric double-opening inner and outer ring. The opening directions of the metasurface units in the outer layer (1) and the outer second layer (5) are the same, while the opening direction of the inner ring of the metasurface unit in the intermediate layer (3) is mirror symmetrical. The phase of the elliptically distributed metasurface units in the outer layer (1), the intermediate layer (3), and the outer second layer (5) is... The distribution satisfies: in, The operating wavelength; , Coordinates; Let be the eccentricity of the ellipse; The focal length of the lens; This is the compensation value.

2. A superlens with staggered asymmetric double-aperture metasurface units according to claim 1, characterized in that: Compensation value satisfy: in The angle of deflection of the inner ring opening relative to the outer ring opening of the metasurface unit.

3. A superlens with staggered asymmetric double-aperture metasurface units according to claim 2, characterized in that: The outer layer (1), the middle layer (3) and the outer second layer (5) are all metal layers. The upper medium (2) is made of Teflon and the lower medium (4) is made of glass.

4. A superlens with staggered asymmetric double-aperture metasurface units according to claim 3, characterized in that: The dielectric constant of the upper dielectric (2) is 2.1, and the dielectric constant of the lower dielectric (4) is 4.

5.

5. A superlens with staggered asymmetric double-aperture metasurface units according to claim 4, characterized in that: The thickness of both the upper dielectric (2) and the lower dielectric (4) is 0.08 mm. .

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