Vanadium dioxide-based multiband dynamic adjustable terahertz metasurface

Abstract

The invention relates to a vanadium dioxide-based multiband dynamic adjustable terahertz metasurface, which comprises a cross-like layer, a first dielectric layer, a first thin film layer, a double-opening metal layer, a second dielectric layer and a second thin film layer which are sequentially arranged from top to bottom, the cross-like layer, the first thin film layer and the second thin film layer are made of vanadium dioxide; the double-opening metal layer is annular, and the annular surface of the double-opening metal layer is provided with a first opening part and a second opening part which penetrate through the annular surface. Vanadium dioxide serves as materials of the cross-like layer, the first thin film layer and the second thin film layer, phase change characteristics of vanadium dioxide at different temperatures are utilized, and the first opening part and the second opening part formed in the double-opening metal layer are combined, so that the metasurface can achieve the wave absorbing function and the frequency selection function at the same time. Moreover, the metasurface provided by the invention is simple in structure and easy to process, and the production cost can be effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of supersurfaces, and in particular relates to a multi-band dynamically adjustable terahertz supersurface based on vanadium dioxide. Background Art

[0002] Due to their special electromagnetic properties, metamaterials have gradually become a research hotspot for many scientists and researchers. They are not only widely used in functional devices such as absorbers, filters, and sensors, but also have potential application value in many fields such as stealth technology, metamaterial lenses, and metamaterial antennas.

[0003] Metasurfaces are the two-dimensional counterpart of metamaterials, and are divided into optical metasurfaces, acoustic metasurfaces, mechanical metasurfaces, etc. according to their control methods. Among these types, the most common is the optical metasurface, which uses subwavelength microstructures to control the polarization, phase, amplitude, frequency, etc. of electromagnetic waves. In structural design, the thickness of the metasurface is much smaller than the wavelength of the electromagnetic wave, so the structure designed using the metasurface has the advantages of small size and light weight. In addition, compared with metamaterials, devices designed using metasurfaces are easy to process. At present, there have been many studies in the field of metasurfaces on narrowband perfect absorbers, multi-bandwidth absorbers, polarization converters, frequency selective surfaces, etc., and their performance is relatively excellent.

[0004] However, as the number of combined resonant units increases, not only will the metasurface structure become bloated, but the processing technology will also become more complicated, increasing manufacturing costs. In addition, the existing metasurface structure can only work at the design frequency with a single function. The function of the existing metasurface structure is determined after it is prepared and cannot be changed. If the working frequency or function needs to be changed, it must be redesigned and manufactured. In summary, the structure of the metasurface in the prior art is complex, the processing is difficult, and the function is single and fixed, with poor flexibility. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] The present invention provides a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide, comprising: a cross-like layer, a first dielectric layer, a first film layer, a double-opening metal layer, a second dielectric layer, and a second film layer arranged in sequence from top to bottom, wherein:

[0007] The materials of the cross-like layer, the first thin film layer and the second thin film layer all include vanadium dioxide;

[0008] The double-opening metal layer is in a ring shape, and a first opening portion and a second opening portion penetrating through the ring surface are formed on the ring surface of the double-opening metal layer.

[0009] In one achievable manner, the cross-like layer includes four right-angle fractals;

[0010] The four right-angle fractals are centrally symmetrically arranged on the upper surface of the first dielectric layer, and there is a gap between every two right-angle fractals.

[0011] In one implementable manner, the right-angle fractal includes: a first rectangular portion and a second rectangular portion;

[0012] The second rectangular portion is vertically connected to the end of the first rectangular portion;

[0013] A connection between the second rectangular portion and the first rectangular portion is disposed toward the center of the first dielectric layer.

[0014] In one implementable manner, the second rectangular portion and the first rectangular portion have the same length.

[0015] In one achievable manner, the materials of the first dielectric layer and the second dielectric layer both include polyimide.

[0016] In one achievable manner, the material of the dual-opening metal layer includes gold.

[0017] In one achievable manner, the double-opening metal layer is in the shape of a circular ring.

[0018] In one achievable manner, the shapes of the first opening portion and the second opening portion are both fan rings, and the curvature of the first opening portion and the curvature of the second opening portion are the same.

[0019] In one achievable manner, an angle between a center line of the first opening and a center line of the second opening is 90°.

[0020] In one achievable manner, the arc angles of the first opening and the second opening are both 10°.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide of the present invention uses vanadium dioxide as the material of the cross-like layer, the first thin film layer and the second thin film layer, utilizes the phase change characteristics of vanadium dioxide at different temperatures, and combines the first opening and the second opening opened on the double-opening metal layer, so that the metasurface provided by the present invention can simultaneously realize the wave absorption function and the frequency selection function. In addition, the structure of the metasurface provided by the present invention is simple, the processing is easy, and the production cost can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided by an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of the structure of a cross-like layer provided in an embodiment of the present invention;

[0025] Figure 3 is a schematic structural diagram of a double-opening metal layer provided by an embodiment of the present invention;

[0026] Figure 4 is a graph showing the relationship between the transmission coefficient and frequency of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in an embodiment of the present invention;

[0027] Figure 5 is a graph showing the relationship between frequency and absorptivity of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in an embodiment of the present invention;

[0028] Figure 6 is a graph showing the relationship between the absorptivity of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide and the polarization angle of an incident wave provided by an embodiment of the present invention;

[0029] Figure 7 This is a relationship diagram between the absorptivity and incident angle of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in an embodiment of the present invention.

[0030] Reference numerals:

[0031] 1: a cross-like layer; 11: a right-angle fractal; 111: a first rectangular portion; 112: a second rectangular portion; 2: a first dielectric layer; 3: a first thin film layer; 4: a double-opening metal layer; 41: a first opening portion; 42: a second opening portion; 5: a second dielectric layer; 6: a second thin film layer. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0033] Embodiment 1

[0034] See also Figure 1 , Figure 1 It is a structural schematic diagram of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in an embodiment of the present invention.

[0035] The present embodiment provides a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide, comprising: a cross-like layer 1, a first dielectric layer 2, a first thin film layer 3, a double-opening metal layer 4, a second dielectric layer 5 and a second thin film layer 6 arranged in sequence from top to bottom, wherein the materials of the cross-like layer 1, the first thin film layer 3 and the second thin film layer 6 all include vanadium dioxide, the double-opening metal layer 4 is annular in shape, and the annular surface of the double-opening metal layer 4 is provided with a first opening portion 41 and a second opening portion 42 that penetrates the annular surface.

[0036] Specifically, the centers of the cross-like layer 1, the first dielectric layer 2, the first film layer 3, the double-opening metal layer 4, the second dielectric layer 5, and the second film layer 6 are located on the same axis, and the first dielectric layer 2, the first film layer 3, the second dielectric layer 5, and the second film layer 6 are all squares with a side length of P, that is, the side length of the metasurface provided in this embodiment is P. The cross-like layer 1, the first dielectric layer 2, and the first film layer 3 constitute the broadband absorption part of the metasurface, and the first opening part 41 and the second opening part 42 opened on the double-opening metal layer 4 are used to realize the frequency selection function of the metasurface. Exemplarily, the side length P of the metasurface is 150 μm.

[0037] See also Figure 2 , Figure 2 1 is a schematic diagram of the structure of a cross-like layer provided in an embodiment of the present invention. In this embodiment, the cross-like layer 1 includes four right-angle fractals 11. The four right-angle fractals 11 are centrally symmetrically arranged on the upper surface of the first dielectric layer 2, and there is a gap between every two right-angle fractals 11.

[0038] Furthermore, the right-angle fractal 11 includes: a first rectangular portion 111 and a second rectangular portion 112. The second rectangular portion 112 is vertically connected to the end of the first rectangular portion 111. The connection between the second rectangular portion 112 and the first rectangular portion 111 is arranged toward the center of the first dielectric layer 2. The second rectangular portion 112 and the first rectangular portion 111 are equal in length.

[0039] Specifically, the ends of the first rectangular portion 111 and the second rectangular portion 112 are vertically connected to form a right-angled right-angled fractal 11, the first rectangular portion 111 and the second rectangular portion 112 are respectively parallel to the two mutually perpendicular sides of the first dielectric layer 2, and the connection portion of the first rectangular portion 111 and the second rectangular portion 112 is arranged toward the center. Four right-angled fractals 11 form a cross-shaped quasi-cross layer 1, and the intervals between the four right-angled fractals 11 form a cross-shaped gap. It should be understood that the width d of the cross-shaped gap is the width of the interval between every two right-angled fractals 11, the length L1 of the quasi-cross layer 1 is the length of the cross-shaped gap, and the width w of the quasi-cross layer 1 is the sum of the width d of the cross-shaped gap and the width of the two second rectangular portions 112. The axis of the cross-shaped gap coincides with the axis of the first dielectric layer 2. Exemplarily, the length L1 of the quasi-cross layer 1 is 140 μm, the width d of the cross-shaped gap is 4 μm, and the width w of the quasi-cross layer 1 is 24 μm.

[0040] In this embodiment, the materials of the first dielectric layer 2 and the second dielectric layer 5 both include polyimide. The thickness of the first dielectric layer 2 and the second dielectric layer 5 are both 40 μm, and the thickness of the cross-like layer 1, the first thin film layer 3, and the second thin film layer 6 are all 0.5 μm. The material of the double-opening metal layer 4 includes gold, and the thickness of the double-opening metal layer 4 is 0.2 μm. The shape of the double-opening metal layer 4 is a circular ring. The shape of the first opening portion 41 and the shape of the second opening portion 42 are both fan rings, and the curvature of the first opening portion 41 and the curvature of the second opening portion 42 are the same, and the angle between the center line of the first opening portion 41 and the center line of the second opening portion 42 is 90°.

[0041] Specifically, see Figure 3 , Figure 3 The first opening 41 and the second opening 42 are hollowed-out fan rings with the same curvature, and the first opening 41 and the second opening 42 on the double-opening metal layer 4 divide the annular double-opening metal layer 4 into two fan rings.

[0042] In this embodiment, the arc angle θ of the first opening 41 and the second opening 42 is 10°. The center line of the first opening 41 and the center line of the second opening 42 are respectively on two diagonal lines of the second dielectric layer 5. Exemplarily, the annular width r of the double-opening metal layer 4 is 10 μm, the outer diameter γ1 of the double-opening metal layer 4 is 130 μm, and the inner diameter γ2 of the double-opening metal layer 4 is 120 μm.

[0043] Specifically, the vanadium dioxide material has adjustable properties, which is in an insulating state at room temperature and in a metallic state at high temperature. The metasurface provided in this embodiment achieves functional switching by changing the phase state of the vanadium dioxide material. When the vanadium dioxide material is in an insulating state, the metasurface provided in this embodiment has a wave absorbing function, and when the vanadium dioxide material is in an insulating state, the metasurface provided in this embodiment has a frequency selection function. The dielectric constant of vanadium dioxide in the terahertz band is usually described by the Drude model: where ω is the frequency of the incident angle, ε ∞ =12 is the dielectric constant when the frequency is infinite, ω p is the plasma frequency that depends on the conductivity σ, γ=5.75*10 13 rad / s is the collision frequency. The plasma frequency can be expressed as Expression, where σ0=3*10 5 S / m, Different electrical conductivities represent different phases of vanadium dioxide. When vanadium dioxide is in a metallic state, its electrical conductivity is 2*10 5 S / m, when vanadium dioxide is in an insulating state, its conductivity is 10S / m.

[0044] A simulation experiment was conducted on the multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in this embodiment. Figure 4 When the temperature is at room temperature, the vanadium dioxide is in an insulating state, and the conductivity is 10S / m. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in this embodiment is a multi-band frequency selective surface, and its frequency selection is achieved by the first opening 41 and the second opening 42. See Figure 4 , Figure 4 This is a relationship diagram between the transmission coefficient and frequency of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided in an embodiment of the present invention. The metasurface provided in this embodiment has a 3db dual-band bandwidth of 1.92~1.97Thz and 2.0~2.06Thz, and has good dual-band characteristics.

[0045] When the temperature rises to 68°C, vanadium dioxide is in a metallic state, and the conductivity of vanadium dioxide is 3*10 5 S / m. At this time, the metasurface provided in this embodiment is a broadband absorber. The absorptivity is an important parameter of the absorber. The absorptivity of the absorber can be expressed as: A = 1-|s 11 | 2 -|s 21 | 2 To represent, where s 11 and 21represents the reflection coefficient and the transmission coefficient, which are generated by the incident wave incident on the absorber. Since the thickness of the vanadium dioxide film is much greater than its skin depth, almost no transmission wave is generated. The absorption rate can be simplified to A = 1-|s 11 | 2 . See Figure 5 , Figure 5 This is a graph showing the relationship between frequency and absorptivity of a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide provided by an embodiment of the present invention. The absorptivity of the metasurface provided by this embodiment is over 90% at 0.55-1.27 Thz. The metasurface provided by this embodiment is polarization-insensitive. The broadband absorption performance of the metasurface provided by this embodiment is insensitive to oblique incident angles and polarization. The tolerances of different incident angles and polarization angles represent the spatial absorption range of the metamaterial absorber. Please refer to Figure 6 and Figure 7 , Figure 6 and Figure 7 The effect of oblique incidence and polarization angle on the absorber performance is shown. At an incident angle of 0° to 35°, the broadband absorption of the metasurface provided in this embodiment is basically maintained at more than 80%, and its stability is good. As the incident angle further increases, the two main absorption peaks of the metasurface provided in this embodiment gradually narrow, and the absorption rate begins to decrease significantly.

[0046] This embodiment provides a multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide. By using vanadium dioxide as the material of the cross-like layer 1, the first thin film layer 3 and the second thin film layer 6, utilizing the phase change characteristics of vanadium dioxide at different temperatures, and combining the first opening 41 and the second opening 42 opened on the double-opening metal layer 4, the metasurface provided by this embodiment can realize two functions at the same time, and by changing the structural parameters of the cross-like layer 1, the metasurface provided by this embodiment has a wider working bandwidth. The metasurface provided by this embodiment can realize the wave absorption function and the frequency selection function at the same time, has a simple structure, is easy to process, and can effectively reduce the production cost.

[0047] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A multi-band dynamically tunable terahertz metasurface based on vanadium dioxide, characterized in that: include: A cross-like layer (1), a first dielectric layer (2), a first thin film layer (3), a double-opening metal layer (4), a second dielectric layer (5) and a second thin film layer (6) are sequentially arranged from top to bottom, wherein: The materials of the cross-like layer (1), the first thin film layer (3) and the second thin film layer (6) all include vanadium dioxide; The double-opening metal layer (4) is annular in shape, and the annular surface of the double-opening metal layer (4) is provided with a first opening portion (41) and a second opening portion (42) penetrating the annular surface.

2. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 1, characterized in that: The cross-like layer (1) includes four right-angle fractals (11); The four right-angle fractals (11) are centrally symmetrically arranged on the upper surface of the first dielectric layer (2), and there is a gap between every two right-angle fractals (11).

3. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 2, characterized in that: The right-angle fractal (11) comprises: a first rectangular portion (111) and a second rectangular portion (112); The second rectangular portion (112) is vertically connected to the end of the first rectangular portion (111); The connection point between the second rectangular portion (112) and the first rectangular portion (111) is arranged towards the center of the first dielectric layer (2).

4. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 3, characterized in that: The second rectangular portion (112) and the first rectangular portion (111) are equal in length.

5. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 1, characterized in that: The materials of the first dielectric layer (2) and the second dielectric layer (5) both include polyimide.

6. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 1, characterized in that: The material of the double-opening metal layer (4) includes gold.

7. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 6, characterized in that: The double-opening metal layer (4) is in the shape of a circular ring.

8. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 7, characterized in that: The shape of the first opening portion (41) and the shape of the second opening portion (42) are both fan rings, and the curvature of the first opening portion (41) and the curvature of the second opening portion (42) are the same.

9. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 7, characterized in that: The included angle between the center line of the first opening (41) and the center line of the second opening (42) is 90°.

10. The multi-band dynamically adjustable terahertz metasurface based on vanadium dioxide according to claim 9, characterized in that: The arc angles of the first opening (41) and the second opening (42) are both 10°.

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