Microwave band loss-type metasurface lens for observing chiral singularities

Abstract

The application relates to the field of super surfaces and relates to a microwave band loss type super surface lens for observing chiral singular points. The application is aimed at solving the problem of difficulty in forming a plasmonic surface in a microwave band and introducing loss. The microwave band loss type super surface lens for observing chiral singular points comprises a plurality of double-resonance loop units arranged in a rectangular array, each double-resonance loop unit comprising a dielectric plate, an open resonant loop and a line structure; the open resonant loop comprises three coaxially nested rectangular loops and a rectangular sheet located at the center of the innermost rectangular loop, and one side of the outermost rectangular loop is provided with an opening; the line structure is in the shape of an I letter; the open resonant loop and the line structure are fixed on the dielectric plate, and a gap is left between the two. The application can realize the observation of X-band singular points by coupling resonance modes in two orthogonal directions and introducing loss without forming a plasmonic surface.

Description

Technical Field

[0001] The present invention belongs to the field of super surfaces. Background Art

[0002] Singularities are a unique phenomenon in non-Hermitian systems, exhibiting not only singular properties in mathematics but also manifesting in physical models as pattern degeneracy and phase abruptness. These properties give singularities broad potential and value in a variety of fields, such as achieving one-way reflection-free communication, exploring singular rings and complex Dirac points, innovating in wireless energy transmission technology, and applying high-order singularities to ultra-sensitive sensing.

[0003] Currently, there are various methods for observing singularities, among which optical resonant cavities, optical on-chip systems, and artificial electromagnetic metasurfaces are three typical methods. In optical resonant cavities, researchers have achieved precise observation of singularities by designing specific cavity structures and utilizing the interference and resonance effects of light. On-chip systems achieve effective manipulation of singularities by integrating micro-nano photonic devices and based on the transmission and coupling mechanisms of optical waveguides. In the field of metasurfaces, researchers have introduced losses by designing plasmon surfaces between metal and dielectric layers, as well as coupling effects between structures, thereby achieving effective control of electromagnetic waves and observation of singularities. For example, a non-Hermitian metasurface in a certain optical band successfully observed singularities through orthogonal coupling of an L-shaped structure and a straight wire structure.

[0004] Most current methods for observing singularities focus on the optical or terahertz bands. This is because the electromagnetic wave frequencies in these bands are relatively high, making it easier to achieve plasmon effects between metals and dielectrics, thereby introducing losses and manipulating electromagnetic waves. In the microwave band, this singular property has great application potential in the design of devices and systems such as high-Q resonant circuits, microwave sensors, and asymmetric transmission control. However, because the frequency of electromagnetic waves in the microwave band is much lower than the resonant frequency of free electrons, metals become almost ideal conductors, and the electric field is only weakly confined in the medium, making it difficult for surface plasmons to propagate in it. Therefore, the gain and loss balance design method in the optical band cannot be directly applied in the microwave band, which limits the exploration and application of the excellent electromagnetic properties and phenomena of singularities in the microwave band. Summary of the Invention

[0005] The present invention aims to solve the problem that it is difficult to form a plasmon surface in the microwave band, which in turn introduces losses. A microwave-band lossy metasurface lens for observing chiral singular points is provided.

[0006] A microwave-band lossy metasurface lens for observing chiral singular points comprises a plurality of dual-resonance ring units arranged in a rectangular array, each of which comprises a dielectric plate, an open resonant ring, and a line structure;

[0007] The split resonant ring comprises three coaxially nested rectangular rings and a rectangular plate located at the center of the innermost rectangular ring, and an opening is provided on one side of the outermost rectangular ring;

[0008] The line structure is in the shape of an "I";

[0009] The split resonant ring and the line structure are both fixed on the dielectric plate, with a gap left between them.

[0010] Furthermore, the dielectric plate is made of polytetrafluoroethylene, the split resonant ring and the line structure are both made of copper, and the upper surface of the split resonant ring is plated with metal nickel.

[0011] Furthermore, the thickness of the dielectric plate is 1.524 mm and the side length is 12 mm;

[0012] The thickness of the copper material is 0.018mm, and the thickness of the nickel material is 0.006mm.

[0013] Furthermore, the side lengths of the outermost rectangular ring are 4.2 mm and 2.7 mm respectively, the opening is located on the short side of the outermost rectangular ring, and the length of the opening is 0.34 mm;

[0014] The side lengths of the rectangular rings in the middle layer are 3 mm and 1.5 mm respectively;

[0015] The side lengths of the innermost rectangular ring are 2.4 mm and 0.9 mm;

[0016] The side lengths of the rectangular pieces are 1.8 mm and 0.3 mm, respectively.

[0017] Furthermore, the lengths of the main body and two side edges of the wire structure are both 3.7 mm, and the widths of the two side edges are 0.65 mm.

[0018] Furthermore, the microwave band lossy metasurface lens includes 25*25 double resonant ring units arranged in a rectangular array.

[0019] This paper proposes a microwave-band lossy metasurface lens for observing chiral singularities. This metasurface uses metals with different ohmic loss characteristics to construct a dual-resonant ring structure within the microwave band (using the X-band as an example). This structure enables observation of X-band singularities by coupling two orthogonal resonant modes and introducing losses without forming a plasmon surface. This demonstrates the applicability of coupled-mode theory in the microwave band and provides new insights and methods for the study and application of singularities in the microwave band. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the main view of the double resonant ring unit;

[0021] Figure 2 is a side view of the dual resonant ring unit;

[0022] Figure 3 The transmission curve diagram of the split resonant ring and I-shaped cutting line structure in the dual resonant ring unit;

[0023] Figure 4 This is the transmission coefficient curve of circularly polarized light when s=1.9mm;

[0024] Figure 5 Schematic diagram of the amplitude conversion coefficient of circularly polarized light with frequency and distance, where (a) represents the amplitude conversion coefficient of left-handed circularly polarized light incident to right-handed circularly polarized light output, and (b) represents the amplitude conversion coefficient of right-handed circularly polarized light incident to left-handed circularly polarized light output;

[0025] Figure 6 The phase color scale diagram of circularly polarized light conversion with frequency and distance, where (a) represents the phase when left-handed circularly polarized light is incident on the outgoing right-handed circularly polarized light, and (b) represents the phase when right-handed circularly polarized light is incident on the outgoing left-handed circularly polarized light;

[0026] Figure 7 is a diagram of the amplitude coefficient of circularly polarized light conversion in the parameter space, where (a) represents the amplitude conversion coefficient of left-handed circularly polarized light incident to right-handed circularly polarized light output, and (b) represents the amplitude conversion coefficient of right-handed circularly polarized light incident to left-handed circularly polarized light output;

[0027] Figure 8 is the phase diagram of circularly polarized light conversion in parameter space, where (a) represents the phase when left-handed circularly polarized light is incident and right-handed circularly polarized light is emitted, and (b) represents the phase when right-handed circularly polarized light is incident and left-handed circularly polarized light is emitted;

[0028] Figure 9 The intrinsic amplitude and phase curves are shown in Figure 2, where (a), (c) and (e) represent the intrinsic amplitudes when s is 0.5 mm, 1.9 mm and 4 mm, respectively; (b), (d) and (f) represent the intrinsic phases when s is 0.5 mm, 1.9 mm and 4 mm, respectively;

[0029] Figure 10 This is the polarization ellipse angle curve of the intrinsic polarization state when s=1.9mm. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 work are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other in the absence of conflict.

[0031] Traditional non-Hermitian metasurfaces typically observe singularities in the optical or terahertz bands by introducing losses in metallic dielectric plasmon surfaces. In contrast, this implementation utilizes coupled-mode theory in the microwave band, leveraging copper's low ohmic loss and excellent conductivity with nickel's significant ferromagnetic properties to introduce losses. This design utilizes a resonant ring-I-shaped cut-line non-Hermitian metasurface, designed to couple resonances in two orthogonal directions and introduce losses, thereby enabling observation of singularities.

[0032] In order to precisely control the resonances in two orthogonal directions, this embodiment defines a parameter space consisting of two parameters, g and d, which represent the opening size of the nickel resonant ring and the arm length of the I-shaped cut-line copper resonant structure, respectively. By adjusting these two parameters, the resonances in two orthogonal directions can be effectively coupled. The coupling strength can be changed by adjusting the distance s between the two resonant structures, controlling the radiation frequency, and optimizing the metasurface structure. After adjustment, a series of unique phenomena caused by the singularity can be observed, such as the asymmetric transmission of circularly polarized light and the topological protection of the 2π phase accumulation at the singularity. These phenomena enrich the understanding of non-Hermitian physics and provide new ideas for the study and application of singularities in the microwave band.

[0033] The microwave-band lossy metasurface lens for observing chiral singular points described in this embodiment includes: 25*25 double-resonant ring units arranged in a rectangular array.

[0034] like Figure 1 and Figure 2 As shown, each dual resonant ring unit includes: a polytetrafluoroethylene dielectric plate, an open resonant ring with nickel plated on the copper surface, and a copper I-shaped cutting line structure.

[0035] Two nickel closed rings and a rectangular plate are coaxially nested within the split resonant ring. The closed rings and rectangular plate have negligible effects on the resonant frequency, but they effectively increase the resonant loss of the resonant ring. The resonant ring unit has a period of c = 12 mm, a thickness of h = 1.524 mm for the polytetrafluoroethylene dielectric plate, a copper thickness of h1 = 0.018 mm, and a nickel-plated thickness of h2 = 0.006 mm for the resonant ring. The geometric parameters of the nickel resonant ring are L1 = 4.2 mm, L2 = 2.7 mm, w1 = 0.5 mm, g = 0.34 mm, L4 = 3 mm, L5 = 1.5 mm, L6 = 2.4 mm, L7 = 0.9 mm, L8 = 1.8 mm, and L9 = 0.3 mm. The gap between the resonant rings is 0.1 mm. The geometric parameters of the copper I-shaped structure are L3 = 3.7 mm, w2 = 0.65 mm, and d = 3.7 mm. The distance between the two resonant rings, denoted as s, is an adjustable parameter. These parameters are optimized to ensure the desired coupling strength and loss characteristics within the microwave frequency band.

[0036] This implementation exploits the differences in ohmic loss and ferromagnetic properties between copper and nickel in the microwave band, introducing losses through a nickel-plated split ring resonator and a copper I-shaped trimming line structure to effectively simulate a non-Hermitian system. This design enables the metasurface to effectively manipulate electromagnetic waves without relying on surface plasmon effects, and allows observation of singularity phenomena unique to non-Hermitian systems.

[0037] Based on the aforementioned non-Hermitian metasurface model, singularity characteristics such as eigenvalue degeneracy parameters, chiral amplitude, and phase response were observed at specific frequencies in the X-band (10 GHz). These characteristics manifest as degeneracy of the eigenamplitude and eigenphase near the singularity, asymmetric transmission of circularly polarized light, and topological protection of the 2π phase at the singularity. These observations validate the effectiveness and accuracy of the designed non-Hermitian metasurface model in the microwave band.

[0038] In this embodiment, the split resonant ring and the I-shaped cutting line structure resonate in a frequency range close to 10 GHz, and the resonance amplitude is shown in the following figure. Figure 3 As shown. Nickel metal, due to its significant ferromagnetic properties, exhibits resonance characteristics near 10 GHz under TE wave incidence conditions, with a transmittance of approximately 0.65. In contrast, copper metal does not have ferromagnetic properties and has low ohmic losses. When TM waves are incident, it also resonates near 10 GHz, but the transmittance is almost 0, meaning that electromagnetic waves are almost unable to penetrate. The open resonant ring and I-shaped structure can respond to electromagnetic waves irradiated in their respective orthogonal directions, achieving independent resonance effects.

[0039] Figure 4The transmission coefficient of circularly polarized light is shown when the distance between the two resonant rings is set to 1.9 mm. Based on the characteristic equation theory of planar non-Hermitian matrices, the eigenvalues ​​will degenerate at the singular point. When the incident light is pure left-hand circularly polarized light (LCP), the output light also remains pure LCP, which means that the conversion channel from left circularly polarized light to right circularly polarized light (RCP) is completely suppressed. That is, at a frequency of 10 GHz, the transmission coefficient T from LCP to RCP is +- is 0, while the opposite conversion path T -+ This result leads to asymmetry in the transmission of circularly polarized light, and the singular point is successfully observed.

[0040] Figure 5 It was demonstrated that when the distance between the scanning resonant cavity elements changes from 0 mm to 5 mm, a bias zero point is observed in the asymmetric transmission characteristics of circularly polarized light in the three-dimensional space composed of frequency and distance.

[0041] Figure 6 A color-scale plot of the phase of circularly polarized light propagated in the three-dimensional space defined by frequency and distance is shown when the distance between resonant cavity elements is scanned from 0 mm to 5 mm. A single loop around a non-Hermitian metasurface singularity exhibits a robust 2π phase accumulation. This means that no matter which closed path is chosen around the singularity, a 2π phase accumulation effect is achieved.

[0042] Figure 7 The variation of the circularly polarized light transmission coefficient at 10 GHz is presented by sweeping the parameter space R (composed of L1 and d). The results show that asymmetric transmission of cross-polarized light can be observed within the parameter space, and a bias zero point appears in the transmission of circularly polarized light.

[0043] Figure 8 The variation of the phase of circularly polarized light transmission in the parameter space R (composed of L1 and d) at a frequency of 10 GHz is demonstrated, showing topological protection of the 2π phase around the singular point.

[0044] Figure 9 The physical nature of the singularity is revealed: two or more eigenvalues ​​and their corresponding eigenstates simultaneously degenerate, and the corresponding eigenstates merge into a single quantum state. As the distance s changes, the non-Hermitian system transitions from an unbroken state to a broken state, with the eigenamplitude and eigenphase degenerating to a single point at s = 1.8 mm and 10 GHz, further confirming the existence of the singularity.

[0045] Figure 10The polarization ellipse angle of the eigenpolarization state, i.e., the exchange phenomenon of the eigenpolarization state, is demonstrated when s = 1.9 mm. At the singular point, the eigenstate is approximately circularly polarized. As the distance changes, the path around the singular point will exchange the two eigenstates, from linear polarization to elliptical polarization, then degenerate to circular polarization, then convert to elliptical polarization, and finally return to linear polarization.

[0046] In summary, based on coupled-mode theory and the characteristic equations of planar non-Hermitian matrices, this paper proposes a novel non-Hermitian metasurface. By leveraging the unique ohmic losses of copper and nickel and the ferromagnetic properties of nickel to introduce a loss mechanism, this allows the design of a non-Hermitian metasurface for observing singularities in the X-band. This paper breaks away from the conventional approach of using metal-dielectric plasmonic surfaces to introduce losses in the optical or terahertz bands, demonstrating the feasibility of designing a non-Hermitian metasurface for observing singularities in the microwave band.

[0047] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A microwave-band lossy metasurface lens for observing chiral singular points, characterized in that: The invention comprises a plurality of double resonant ring units arranged in a rectangular array, each of which comprises: a dielectric plate, an open resonant ring and a line structure; The split resonant ring comprises three coaxially nested rectangular rings and a rectangular plate located at the center of the innermost rectangular ring, and an opening is provided on one side of the outermost rectangular ring; The line structure is in the shape of "I"; The split resonant ring and the line structure are both fixed on the dielectric plate, with a gap left between them; The dielectric plate is made of polytetrafluoroethylene, the open resonant ring and the line structure are both made of copper, and the upper surface of the open resonant ring is plated with metal nickel.

2. The microwave band lossy metasurface lens for observing chiral singular points according to claim 1, characterized in that: The dielectric plate has a thickness of 1.524 mm and a side length of 12 mm; The thickness of the copper material is 0.018mm, and the thickness of the nickel material is 0.006mm.

3. The microwave-band lossy metasurface lens for observing chiral singular points according to claim 2, characterized in that: The side lengths of the outermost rectangular ring are 4.2 mm and 2.7 mm respectively, the opening is located at the short side of the outermost rectangular ring, and the opening length is 0.34 mm; The side lengths of the rectangular rings in the middle layer are 3 mm and 1.5 mm respectively; The side lengths of the innermost rectangular ring are 2.4 mm and 0.9 mm; The side lengths of the rectangular pieces are 1.8 mm and 0.3 mm, respectively.

4. The microwave-band lossy metasurface lens for observing chiral singular points according to claim 2, characterized in that: The length of the main body and two side edges of the wire structure are both 3.7 mm, and the width of the two side edges is 0.65 mm.

5. The microwave band lossy metasurface lens for observing chiral singular points according to claim 1, 2, 3 or 4, characterized in that: The microwave band lossy metasurface lens consists of 25*25 double resonant ring units arranged in a rectangular array.

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