A broadband reconfigurable metasurface perfect absorber for mid-infrared applications

Abstract

This invention belongs to the field of optical absorber technology, specifically relating to a broadband reconfigurable metasurface perfect absorber for mid-wave infrared applications. The absorber comprises, in the thickness direction, a metal substrate layer, a dielectric layer, a metasurface structure, and a protective layer. The metasurface structure is composed of a periodic array of multiple unit structures, with adjacent unit structures having different outer diameters. Each unit structure is made of indium antimony tellurium compound, and the composition of the indium antimony tellurium compound is In. x Sb y Te z , of which 2.5

Description

Technical Field

[0001] This invention belongs to the field of light absorber technology, specifically relating to a broadband reconfigurable metasurface perfect absorber for mid-wave infrared applications. Background Technology

[0002] Metasurfaces are artificial composite materials composed of subwavelength-sized unit structures, typically consisting of periodically arranged nanostructures. They can effectively control the propagation of light and its interaction with matter, thus enabling free manipulation and effective control of light. Perfect absorbers are materials or structures capable of completely absorbing electromagnetic waves, achieving very high absorption rates while reflecting or transmitting almost no electromagnetic waves. Typical metasurface perfect absorber structures usually employ a metal-dielectric-metal structure, consisting of a metal substrate, a dielectric spacer layer, and periodically arranged metal patterns. Zero reflection at the resonant frequency is achieved through the design of the upper metal layer to match the environmental impedance.

[0003] Mid-wave infrared light typically falls between 3 and 8 μm, in the middle of the infrared spectrum, and has wide applications in industry and medicine, such as infrared sensors, thermal imaging equipment, infrared detectors, and infrared radiation modulation. Therefore, the control and absorption of mid-wave infrared light is of great significance. Mid-wave infrared absorbers utilize the design principle of metasurface structures to achieve efficient absorption of mid-wave infrared light. By controlling the structural parameters, material properties, and optical modes of the metasurface, electromagnetic waves undergo multiple reflections and interferences on the structure, thereby enhancing the interaction between light and material and achieving a high absorption effect.

[0004] While mid-wave infrared perfect absorbers hold great potential in the field of optical materials and devices, current technology still faces several drawbacks and challenges. The design and fabrication of mid-wave infrared perfect absorbers are primarily focused on specific wavelength ranges, resulting in insufficient absorption bandwidth. Researchers utilize plasmon resonance generated on metal surfaces, but this produces narrow absorption bandwidths. Once a traditional perfect absorber is fabricated, its optical properties are fixed. Thermal imaging technology can generate a temperature distribution image by detecting the infrared radiation of an object, reflecting temperature differences in different regions. Infrared thermal imaging cameras can sense the infrared radiation on an object's surface and convert it into a visualized thermal image. Any object above absolute zero emits radiation. According to Kirchhoff's laws, the emissivity of an object's radiation equals its absorptivity; therefore, adjusting the absorbance of an absorber is essentially adjusting its thermal emissivity. Conventional absorbers can only be controlled for imaging based on the shift in the peak wavelength of thermal radiation at different temperatures and the differences in emissivity; imaging at the same temperature cannot be adjusted. Summary of the Invention

[0005] To address the issues of insufficient absorption bandwidth and inability to adjust imaging at the same temperature in current mid-wave infrared perfect absorbers, the present invention aims to provide a reconfigurable metasurface perfect absorber with high absorptivity and a large mid-wave infrared absorption bandwidth in the surface phase.

[0006] This invention aims to utilize a tunable absorber to achieve imaging adjustment at the same temperature. For example, by using a tunable metasurface as the absorption pixel, different absorption patterns can be achieved by switching the crystal state of different pixel units. This invention utilizes the switching between crystalline and amorphous states of an indium antimony tellurium compound to achieve tunable perfect absorption in the mid-infrared range. In the crystalline state, it achieves broadband absorption of over 90% in the 4000-7000 nm band, while in the amorphous state, the absorption rate in this band is 20%-40%. Furthermore, this absorber can be adjusted within the range of room temperature to 270°C, exhibiting a wide operating temperature range.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows.

[0008] This invention provides a broadband reconfigurable metasurface perfect absorber for mid-wave infrared, which includes, in the thickness direction, a metal substrate layer, a dielectric layer, a metasurface structure and a protective layer in sequence.

[0009] The metasurface structure is composed of a periodic array of multiple unit structures, and the outer diameters of two adjacent unit structures are different.

[0010] Each of the aforementioned unit structures is made of indium antimony tellurium compound, wherein the composition of the indium antimony tellurium compound is In. x Sb y Te z , of which 2.5 <x<3.5,0.5<y<1.5,1.5<z<2.5。

[0011] In a preferred embodiment, each of the unit structures includes a central column and a ring, the ring surrounding the outside of the central column.

[0012] In a preferred embodiment, an annular cavity is formed between the central column and the ring body, and a portion of the protective layer fills the annular cavity.

[0013] In a preferred embodiment, the metasurface structure includes a first unit structure and a second unit structure, which are alternately arranged on the dielectric layer. The outer diameters of the first unit structure and the second unit structure are different. For example, the outer diameter of the first unit structure is larger than that of the second unit structure, or the outer diameter of the first unit structure is smaller than that of the second unit structure.

[0014] In a preferred embodiment, the first unit structure includes a first central pillar and a first ring, and the second unit structure includes a second central pillar and a second ring;

[0015] The inner diameter of the first ring is larger than the outer diameter of the second ring.

[0016] In a preferred embodiment, the outer diameter of the first central column is greater than or equal to the outer diameter of the second central column. Preferably, the outer diameter of the first central column is greater than the outer diameter of the second central column.

[0017] In a preferred embodiment, the ratio of the inner diameter of the first ring to the inner diameter of the second ring is 0.7 to 0.8:0.4.

[0018] In a preferred embodiment, the spacing between two adjacent unit structures is equal.

[0019] In a preferred embodiment, the thickness ratio of the metal layer, the dielectric layer, and the metasurface structure is 300–400: 80–200: 6000–8000.

[0020] In a preferred embodiment, the thickness of the metal layer is 300-400 nm; the thickness of the dielectric layer is 6000-800 nm; and the thickness of the metasurface structure is 6000-8000 nm.

[0021] In a preferred embodiment, the dielectric layer is made of silicon dioxide.

[0022] In a preferred embodiment, the broadband reconfigurable metasurface perfect absorber operates in the temperature range of room temperature to 270°C.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention utilizes the surface plasmon resonance excited by the dielectric layer and the unit structure to enable the absorber to exhibit high absorption performance in the mid-infrared band. Furthermore, since the unit structure is selected from indium antimony telluride compounds with a crystallization temperature of ~270℃, the operating temperature range of the absorber can be adjusted within the range of room temperature to 270℃, thus having a wide operating temperature range. This solves the problems of insufficient absorption bandwidth and inability to adjust imaging at the same temperature in current mid-wave infrared perfect absorbers.

[0025] 2. This invention, by selecting indium antimony tellurium compounds as phase change materials, enables rapid and reversible switching between crystalline and amorphous states on a nanosecond scale, and exhibits non-volatility. Compared to traditional metasurface tuning methods, this invention remains stable without continuous external stimulation. This invention achieves tunable perfect absorption in the mid-infrared range; in the crystalline state, it achieves broadband absorption of over 90% in the 4000-7000 nm band, while in the amorphous state, the absorption rate in this band is ~20%-40%. Attached Figure Description

[0026] Figure 1 This is a cross-sectional schematic diagram along the x-axis of a broadband reconfigurable metasurface perfect absorber provided in one embodiment of the present invention.

[0027] Figure 2 The diagram shows three metasurface unit structures. S1 is a ring structure, S2 is a ring-cylinder structure, and S3 is a cylindrical structure.

[0028] Figure 3 This is a three-dimensional structural schematic diagram of a broadband reconfigurable metasurface perfect absorber provided in one embodiment of the present invention.

[0029] Figure 4 The absorption spectra of the metasurface units with three different unit structures are shown in the mid-infrared range.

[0030] Figure 5 This diagram illustrates metasurface units of three different sizes. S2 is a ring-within-a-cylinder structure with two alternating sizes; S4 and S5 are ring-within-a-cylinder structures of a single size.

[0031] Figure 6 The absorption spectra of metasurface units in the mid-infrared range are given for two alternating sizes of ring-within-cylinder structures (S2) and single-size ring-within-cylinder structures (S4 and S5).

[0032] Figure 7 and Figure 8 The electric and magnetic field distributions at the xz interface at 4.3 μm are shown.

[0033] Figure 9 and Figure 10 The electric and magnetic field distributions at the xz interface at 5.7 μm are shown.

[0034] Figure 11 and Figure 12 The electric and magnetic field distributions at the xz interface at 7.2 μm are shown.

[0035] Figure 13 The images show the metasurface absorption spectra of Examples 2 and 3.

[0036] In the figure, 1 is the protective layer; 2 is the unit structure; 21 is the first unit structure; 211 is the first central pillar; 212 is the first ring; 22 is the second unit structure; 221 is the second central pillar; 222 is the second ring; 3 is the dielectric layer; 4 is the metal layer; and 5 is the substrate. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] 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.

[0039] The present invention aims to utilize a tunable absorber to adjust the imaging at the same temperature. For example, by using a tunable metasurface as an absorption pixel, different absorption can be achieved by switching the crystallization state of different pixel units, thereby realizing the imaging of different patterns.

[0040] Compared to other metasurface tuning methods, such as electrical bias adjustment of charge carriers and heating-induced vanadium dioxide, these methods require continuous external stimulation to remain stable. The phase change material selected in this invention is non-volatile, and compared to other phase change materials, the phase change material selected in this invention is an indium antimony tellurium crystal compound, which not only exhibits metallic properties in the infrared range, but also has a crystallization temperature of 270°C. This means that the absorber obtained thereby can be tuned within the range of room temperature to 270°C, and has a wide operating temperature range.

[0041] This invention provides a broadband reconfigurable metasurface perfect absorber for mid-wave infrared, which includes, in the thickness direction, a metal substrate layer, a dielectric layer 3, a metasurface structure and a protective layer 1.

[0042] The metasurface structure is composed of a periodic array of multiple unit structures 2, with adjacent unit structures 2 having different outer diameters; each unit structure 2 is made of indium antimony tellurium compound, and the composition of the indium antimony tellurium compound is In. x Sb y Te z , of which 2.5 <x<3.5,0.5<y<1.5,1.5<z<2.5。

[0043] The present invention utilizes a metal-based bottom layer to play the role of specularly reflecting electromagnetic waves, while avoiding the transmission of incident electromagnetic waves; by utilizing the surface plasmon resonance excited by the dielectric layer 3 and the unit structure 2, the absorber exhibits high absorption performance in the mid-infrared band. In addition, compared with other phase change materials, the unit structure 2 of the present invention selects indium antimonide telluride crystal compound, which not only exhibits metallicity in the infrared range, but also has a crystallization temperature of 270 °C, which means that the obtained absorber can be adjusted within the range from room temperature to 270 °C, having a relatively wide working temperature range.

[0044] The indium antimonide telluride compound described in the present invention has a composition of In x Sb y Te z , where 2.5 < x < 3.5, 0.5 < y < 1.5, 1.5 < z < 2.5. For example, In3Sb 0.6 Te2, In3SbTe2, In3Sb 1.2 Te2, In3Sb 1.4 Te2, In3SbTe 2.4 , In3SbTe 1.6 , In 3.4 SbTe2, In 2.6 SbTe 1.6 , In 2.6 Sb 0.6 Te 1.6 etc. The indium antimonide telluride compound of the present invention uses high-purity argon as the sputtering gas and is prepared by single-target sputtering using a magnetron sputtering method to obtain an indium antimonide telluride compound thin film. The preparation method of the indium antimonide telluride compound is an existing method. The target materials for preparing the indium antimonide telluride compound are all purchased from Zhongnuo New Materials (Beijing) Co., Ltd., with a purity ≥ 99.99%.

[0045] In a preferred embodiment, the metal-based bottom layer includes a substrate 5 and a metal layer 4. The metal layer 4 is stacked on the upper side of the substrate 5 in the thickness direction, and the metal layer 4 is disposed on one side of the dielectric layer 3.

[0046] In a preferred embodiment, each unit structure 2 includes a central cylinder and an annular body, and the annular body surrounds the outside of the central cylinder.

[0047] In a preferred embodiment, an annular cavity is formed between the central cylinder and the annular body, and a part of the protective layer is filled in the annular cavity.

[0048] Such as Figure 1 and Figure 3The broadband reconfigurable metasurface perfect absorber provided in one embodiment of the present invention includes, from bottom to top, a substrate 5, a metal layer 4, a dielectric layer 3, a metasurface structure and a protective layer 1. The metasurface structure is composed of a periodic array of metasurface units; the metasurface unit is a tetragonal lattice unit formed by four unit structures 2; and the outer diameters of two adjacent unit structures 2 are different.

[0049] The substrate 5 has no significant impact on device performance and can be selected from different types of smooth substrates according to actual needs. For example, smooth silicon dioxide and silicon wafers can be used as substrates. The substrate of this invention includes, but is not limited to, silicon dioxide and silicon wafers. The metal layer 4 serves to reflect electromagnetic waves in a mirror manner and prevent the transmission of incident electromagnetic waves. The metal layer material can be selected according to actual needs. For example, the metal layer 4 can be selected from metals including but not limited to Au, W, and Ti.

[0050] The dielectric layer 3 is silicon dioxide, and the metasurface unit is indium antimony telluride compound (IUCN). Since IUCN is a semiconductor in its amorphous state and exhibits metallic properties with a negative permittivity across the entire infrared range in its crystalline state, it is chosen as the unit structure material for the reconfigurable super-perfect absorber. Crystalline IUCN exhibits an extinction coefficient k of 9–16 in the mid-infrared band (3–8 μm), while amorphous IUCN has an extinction coefficient k of 0.1 in the same band, thus demonstrating higher absorption performance in the crystalline IUCN. This invention utilizes surface plasmon resonance (SPR) jointly excited by the unit structure 2 composed of dielectric silicon dioxide and IUCN to achieve high absorption performance in the mid-infrared band. The phase change material of this invention can achieve phase transition through optical pulses or heating, enabling applications in fields such as thermal imaging and thermal radiation modulation.

[0051] In a preferred embodiment, the metasurface structure includes a first unit structure 21 and a second unit structure 22 arranged adjacent to each other. The first unit structure 21 includes a first central pillar 211 and a first ring 212, and the second unit structure 22 includes a second central pillar 221 and a second ring 222. The inner diameter of the first ring 212 is larger than the outer diameter of the second ring 222.

[0052] In a preferred embodiment, the outer diameter of the first central column 211 is greater than or equal to the outer diameter of the second central column 221. Preferably, the outer diameter of the first central column 211 is greater than the outer diameter of the second central column 221.

[0053] In a preferred embodiment, the ratio of the inner diameter of the first ring 212 to the inner diameter of the second ring 222 is 0.7 to 0.8:0.4.

[0054] In a preferred embodiment, the first unit structure 21 and the second unit structure 22 are alternately arranged on the dielectric layer 3.

[0055] In a preferred embodiment, the metasurface structure is composed of a periodic array of multiple metasurface units; four adjacent unit structures 2 constitute a tetragonal lattice unit, forming a metasurface unit. Figure 3The metasurface unit comprises two first unit structures 21 and two second unit structures 22, arranged alternately to form a tetragonal lattice unit. The first unit structure includes a first central pillar 211 and a first ring 212. The radius of the first central pillar 211 is denoted as r, and the outer and inner diameters of the first ring 212 are denoted as R1 and R2, respectively. The second unit structure 22 includes a second central pillar 221 and a second ring 222. The radius of the second central pillar 221 is denoted as d, and the outer and inner diameters of the second ring 222 are denoted as D1 and D2, respectively. The period is P. Specific parameters are as follows: R1 = 900–1000 nm, R2 = 700–800 nm, r = 200–500 nm; D1 = 500–600 nm, D2 = 300–400 nm, d = 150–200 nm, P = 2200–2600 nm. The first unit structure 21 and the two second unit structures 22 have the same thickness. R1 = 900–1000 nm, for example, R1 = 900 nm, 910 nm, 920 nm, 930 nm, 940 nm, 950 nm, 960 nm, 970 nm, 980 nm, 990 nm, 1000 nm, etc. R2 = 700–800 nm, for example, R2 = 700 nm, 710 nm, 720 nm, 730 nm, 740 nm, 750 nm, 760 nm, 770 nm, 780 nm, 790 nm, 800 nm, etc. r = 200–500 nm, for example, r = 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc. D1 = 500–600 nm, for example, D1 = 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, etc. D2 = 300–400 nm, for example, D2 = 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 570 nm, 580 nm, 590 nm, 600 nm, etc. d = 150–200 nm, for example, d = 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, etc. P = 2200–2600 nm. For example, P = 2200nm, 2250nm, 2300nm, 2350nm, 2400nm, 2450nm, 2500nm, 2550nm, 2600nm, etc.

[0056] In a preferred embodiment, the spacing between two adjacent unit structures 2 is equal.

[0057] In a preferred embodiment, the thickness ratio of the metal layer 4, the dielectric layer 3, and the metasurface structure is 300–400: 80–200: 6000–8000. Preferably, the thickness of the metal layer 4 is 300–400 nm; the thickness of the dielectric layer 3 is 6000–800 nm; and the thickness of the metasurface structure is 6000–8000 nm.

[0058] In a preferred embodiment, the dielectric layer 3 is made of silicon dioxide.

[0059] In a preferred embodiment, the broadband reconfigurable metasurface perfect absorber operates in the temperature range of room temperature to 270°C. Specific Implementation

[0061] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0062] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0063] Unless otherwise specified, the methods described in the following embodiments are conventional methods; the reagents and materials mentioned are commercially available unless otherwise specified.

[0064] The present invention will now be described in further detail with reference to the accompanying drawings.

[0065] like Figure 3 This invention relates to a broadband reconfigurable metasurface perfect absorber for mid-infrared applications. The optical response characteristics of this broadband reconfigurable metasurface perfect absorber were simulated using the commercial finite element software Lμmerical FDTD. The model was set under the following conditions: a plane wave is incident on the broadband reconfigurable metasurface perfect absorber in the -z direction; periodic boundary conditions are applied in the x and y directions of the metasurface elements; and a perfectly matched layer boundary condition is applied in the z direction. A monitor was placed above the light source to detect the structure's reflectivity.

[0066] The normalized absorptivity (A) can be calculated using the formula A(ω) = 1 - R(ω) - T(ω), where R(ω) and T(ω) represent the reflectivity and transmittance of the absorber at the corresponding frequencies of the incident electromagnetic waves, respectively. In this invention, the thickness of the metal substrate 5 is much greater than the skin depth of infrared electromagnetic waves, making it almost impossible for the incident electromagnetic waves to pass through. Therefore, the formula for the absorptivity is simplified to A(ω) = 1 - R(ω).

[0067] To illustrate the effects of three different metasurface unit structures, this invention provides schematic diagrams of the three metasurface unit structures, as follows: Figure 2 As shown, S1 is a ring structure, S2 is a ring-cylinder structure, and S3 is a cylindrical structure. Figure 4 The absorption spectra of the metasurface units with three different unit structures are shown in the mid-infrared range.

[0068] Due to the high symmetry of the unit structure, TE-polarized incident electromagnetic waves are chosen as the research object here, such as... Figure 4 The results show that the absorption spectrum curves corresponding to these three structures have three relatively obvious resonance absorption peaks. Among them, the S2 ring-cylinder structure has an absorption rate of more than 90% in the range of 4500-7500nm, and has a large absorption bandwidth.

[0069] To illustrate the effects of metasurface units with three different unit cell sizes, this invention provides schematic diagrams of metasurface units with three different unit cell sizes, as follows: Figure 5 As shown, S2 is a ring-within-a-cylinder structure with two alternating sizes; S4 and S5 are ring-within-a-cylinder structures with a single size. Figure 6 The absorption spectra of metasurface units in the mid-infrared range are given for two alternating sizes of ring-within-cylinder structures (S2) and single-size ring-within-cylinder structures (S4 and S5).

[0070] like Figure 6 The absorption spectrum is displayed as three types of metasurface unit arrays arranged in alternating patterns of two single-size and two-size configurations. Figure 6 The results show that different sizes of ring-within-a-cylinder structures correspond to different resonant wavelengths. The resonant wavelength corresponding to the small-sized ring-within-a-cylinder structure is 4000nm, while the resonant wavelengths corresponding to the large-sized ring-within-a-cylinder structure are 4700nm and 7500nm. By arranging the two sizes of structures alternately, the coupling of the resonant cavity can be achieved, thereby realizing broadband absorption in the range of 4500-7500nm.

[0071] We selected one of the large and small circular ring unit structures and plotted the electric and magnetic field distributions of the xz cross section at three resonant wavelengths of 4.3 μm, 5.7 μm, and 7.2 μm.

[0072] Figure 7and Figure 8 The electric and magnetic field distributions at the xz interface at 4.3 μm are shown. It can be seen that the electric field is mainly confined to both sides of the inner cylinder of the large ring, and electromagnetic wave resonance is generated by the inner cylinder of the large ring.

[0073] Figure 9 and Figure 10 The electric and magnetic field distributions at the xz interface at 5.7 μm are shown. It can be seen that the electric field is mainly confined to the outside of the small ring, and the resonance in this band is generated by the small ring.

[0074] Figure 11 and Figure 12 The electric and magnetic field distributions at the xz interface at 7.2 μm are shown. It can be seen that the resonance in this band is generated by the large and small circular rings, and judging from the corresponding magnetic field distribution, the two resonant cavities have a coupling effect.

[0075] In summary, this invention increases the location where electromagnetic waves resonate by using a ring-within-a-cylinder unit structure, and achieves coupling of the resonant cavity by using two different sizes of ring-within-a-cylinder structures. The electromagnetic field is significantly enhanced and locally confined at different locations in the metamaterial unit structure, thereby achieving absorption of more than 90% over a wide frequency spectrum.

[0076] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0077] Example 1

[0078] The broadband reconfigurable metasurface perfect absorber provided in this embodiment includes, from bottom to top, a substrate 5, a metal layer 4, a dielectric layer 3, a metasurface structure, and a protective layer 1. In this embodiment, the metal layer 4 is made of tungsten, the dielectric layer 3 is made of silicon dioxide, and the thickness of the dielectric layer 3 is 800 nm.

[0079] The metasurface structure is composed of a periodic array of metasurface units; each metasurface unit is a tetragonal lattice unit formed by four unit structures 2; and the outer diameters of two adjacent unit structures 2 are different.

[0080] The unit structures 2 are respectively referred to as the first unit structure 21 and the second unit structure 22; the first unit structure 21 includes a first central column 211 and a first ring 212 surrounding the first central column 211; the second unit structure 22 includes a second central column 221 and a second ring 222 surrounding the second central column 221; the inner diameter of the first ring 212 is larger than the outer diameter of the second ring 222.

[0081] In the first unit structure 21, the outer diameter, inner diameter of the first ring 212, and the radius of the first central pillar 211 inside are 1 μm, 0.8 μm, and 0.3 μm, respectively; in the second unit structure 22, the outer diameter, inner diameter of the second ring 222, and the radius of the second central pillar 221 inside are 0.6 μm, 0.4 μm, and 0.2 μm, respectively. The material of unit structure 2 is indium antimony tellurium compound, and the thickness of unit structure 2 is 200 nm.

[0082] The metasurface structure is composed of a periodic array of metasurface units, with a period of P = 2.4 μm.

[0083] The absorption spectrum of the broadband reconfigurable metasurface perfect absorber in this embodiment can be found in [link to example]. Figure 4 The S2 sample. (From) Figure 4 As can be seen, the broadband reconfigurable metasurface perfect absorber of this embodiment has an absorption rate of more than 90% in the entire wavelength range of 4.5μm-7.5μm.

[0084] Example 2

[0085] The broadband reconfigurable metasurface perfect absorber provided in this embodiment includes, from bottom to top, a substrate 5, a metal layer 4, a dielectric layer 3, a metasurface structure, and a protective layer 1. In this embodiment, the metal layer 4 is made of gold, the dielectric layer 3 is made of silicon dioxide, and the thickness of the dielectric layer 3 is 800 nm.

[0086] The metasurface structure is composed of a periodic array of metasurface units; each metasurface unit is a tetragonal lattice unit formed by four unit structures 2; and the outer diameters of two adjacent unit structures 2 are different.

[0087] The unit structures 2 are respectively referred to as the first unit structure 21 and the second unit structure 22; the first unit structure 21 includes a first central column 211 and a first ring 212 surrounding the first central column 211; the second unit structure 22 includes a second central column 221 and a second ring 222 surrounding the second central column 221; the inner diameter of the first ring 212 is larger than the outer diameter of the second ring 222.

[0088] In the first unit structure 21, the outer diameter, inner diameter of the first ring 212, and the radius of the first central pillar 211 inside are 1 μm, 0.7 μm, and 0.4 μm, respectively; in the second unit structure 22, the outer diameter, inner diameter of the second ring 222, and the radius of the second central pillar 221 inside are 0.6 μm, 0.4 μm, and 0.2 μm, respectively. The material of unit structure 2 is indium antimony tellurium compound, and the thickness of unit structure 2 is 100 nm.

[0089] The metasurface structure is composed of a periodic array of metasurface units, with a period of P = 2.4 μm.

[0090] The absorption spectrum of the broadband reconfigurable metasurface perfect absorber in this embodiment can be found in [link to example]. Figure 13 .Depend on Figure 13 As can be seen, the broadband reconfigurable metasurface perfect absorber of this embodiment has an absorption rate of more than 90% in the entire wavelength range of 3.5μm-3.8μm and 4.5μm-7.1μm.

[0091] Example 3

[0092] The broadband reconfigurable metasurface perfect absorber provided in this embodiment includes, from bottom to top, a substrate 5, a metal layer 4, a dielectric layer 3, a metasurface structure, and a protective layer 1. In this embodiment, the metal layer 4 is made of aluminum, the dielectric layer 3 is made of silicon dioxide, and the thickness of the dielectric layer 3 is 800 nm.

[0093] The metasurface structure is composed of a periodic array of metasurface units; each metasurface unit is a tetragonal lattice unit formed by four unit structures 2; and the outer diameters of two adjacent unit structures 2 are different.

[0094] The unit structures 2 are respectively referred to as the first unit structure 21 and the second unit structure 22; the first unit structure 21 includes a first central column 211 and a first ring 212 surrounding the first central column 211; the second unit structure 22 includes a second central column 221 and a second ring 222 surrounding the second central column 221; the inner diameter of the first ring 212 is larger than the outer diameter of the second ring 222.

[0095] In the first unit structure 21, the outer diameter, inner diameter of the first ring 212, and the radius of the first central pillar 211 inside are 1 μm, 0.8 μm, and 0.3 μm, respectively; in the second unit structure 22, the outer diameter, inner diameter of the second ring 222, and the radius of the second central pillar 221 inside are 0.6 μm, 0.4 μm, and 0.2 μm, respectively. The material of unit structure 2 is indium antimony tellurium compound, and the thickness of unit structure 2 is 80 nm.

[0096] The metasurface structure is composed of a periodic array of metasurface units, with a period of P = 2.4 μm.

[0097] The absorption spectrum of the broadband reconfigurable metasurface perfect absorber in this embodiment can be found in [link to example]. Figure 13 .Depend on Figure 13 As can be seen, the broadband reconfigurable metasurface perfect absorber of this embodiment has an absorption rate of more than 90% in the entire wavelength range of 4μm-7μm.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A broadband reconfigurable metasurface perfect absorber for mid-infrared radiation, characterized in that, In the thickness direction, it consists of a metal substrate layer, a dielectric layer, a metasurface structure, and a protective layer in sequence. The metasurface structure is composed of a periodic array of multiple unit structures, and the outer diameters of two adjacent unit structures are different. Each of the aforementioned unit structures is made of indium antimony tellurium compound, wherein the composition of the indium antimony tellurium compound is In. x Sb y Te z , of which 2.5 <x<3.5,0.5<y<1.5,1.5<z<2.5。 2. The broadband reconfigurable metasurface perfect absorber for mid-infrared radiation according to claim 1, characterized in that, Each of the aforementioned unit structures includes a central column and a ring, the ring surrounding the outside of the central column.

3. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 2, characterized in that, An annular cavity is formed between the central column and the ring body, and a portion of the protective layer fills the annular cavity.

4. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 2, characterized in that, The metasurface structure includes a first unit structure and a second unit structure, and the first unit structure and the second unit structure are alternately arranged on the dielectric layer.

5. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 4, characterized in that, The first unit structure includes a first central column and a first ring, and the second unit structure includes a second central column and a second ring; The inner diameter of the first ring is larger than the outer diameter of the second ring.

6. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 5, characterized in that, The outer diameter of the first central column is greater than or equal to the outer diameter of the second central column.

7. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 5, characterized in that, The ratio of the inner diameter of the first ring to the inner diameter of the second ring is 0.7 to 0.8:0.

4.

8. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 1, characterized in that, The thickness ratio of the metal substrate, the dielectric layer, and the metasurface structure is 300-400: 80-200: 6000-8000.

9. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 1 or 8, characterized in that, The dielectric layer is made of silicon dioxide.

10. The broadband reconfigurable metasurface perfect absorber for mid-infrared wavelengths according to claim 1, characterized in that, The broadband reconfigurable metasurface perfect absorber operates in the temperature range of room temperature to 270°C.

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