Tunable Infrared Selective Thermal Emitter Based on Cylindrical Structure Array

Abstract

The tunable infrared selective thermal emitter based on a cylindrical structure array belongs to the field of micro-nano optoelectronic technology; it is composed of multiple tunable structural units arranged periodically. Sunlight is incident in the form of a plane wave. Each tunable structural unit includes a substrate layer, a buffer layer, and an antenna from bottom to top. The substrate layer and the buffer layer are square in shape, and the antenna is a three-layer cylindrical structure. The structure of the present invention is simple. In the atmospheric windows of 3-5μm and 8-14μm, the average emissivities are about 0.20 and 0.18 respectively, and the average emissivity in the non-atmospheric window of 5-8μm is about 0.80. Moreover, it is not affected by the polarization of the light source and has good emission effects within the incident angle range of 0°-60°. The addition of GST enables the thermal emitter to not only meet the requirements of low emissivity in the atmospheric window and radiative heat dissipation in the non-atmospheric window, but also tune the infrared emissivity spectrum to achieve switching between the infrared "stealth" and "non-stealth" states.

Description

Technical Field

[0001] The tunable infrared selective thermal emitter based on the cylinder structure array of the present invention belongs to the field of micro-nano optoelectronic technology. Background Art

[0002] Metasurface is a structure with a periodically arranged artificial design. Because of its special electromagnetic characteristics, tunable refractive index, asymmetric transmission and other features, it is often used to prepare efficient electromagnetic wave thermal emitters.

[0003] Nowadays, with the progress of infrared detection technology, infrared stealth technology plays an increasingly important role in modern military warfare. Infrared stealth technology is to reduce the detectability of a target by reducing or changing the infrared radiation characteristics of the target. Many researchers have tried to use metamaterial structures composed of periodic or locally periodic arrangements to achieve infrared stealth. Therefore, how to efficiently achieve infrared stealth has become a major research topic.

[0004] For infrared stealth, according to the Stefan-Boltzmann law, the radiant heat energy of a unit thermal surface is proportional to the emissivity ε of the surface and the fourth power of its absolute temperature T. Temperature control is a direct method to achieve infrared stealth, but it also requires additional cooling and heating equipment. Modulating the emissivity is an effective method to achieve thermal stealth. Based on the above principle, reducing the infrared characteristics of the device surface in the dual-band atmospheric window (3 - 5μm and 8 - 14μm) can avoid being detected by infrared detection equipment, which is of great significance for achieving stealth. By covering the surface of an object with a low-emissivity material, the infrared characteristics of the target can be reduced, but it will also prevent the target from radiating heat to the surrounding, resulting in an increase in the surface temperature of the target and ultimately reducing the stealth performance. Therefore, an ideal infrared selective thermal emitter should have a low emissivity in the dual-band atmospheric window and a high emissivity in the wavelength range of the non-atmospheric window (5 - 8μm), so that it can not only reduce the infrared characteristics of the target, but also dissipate heat by radiating energy in a specific band.

[0005] Recently, the application of phase change materials in the optical field has become more and more extensive. Ge2Sb2Te5 (GST) is a phase change material that can achieve the conversion between the amorphous state and the crystalline state under conditions such as heating, laser pulses and applied voltage. The dielectric constants in the amorphous state and the crystalline state are 16 and 34 respectively. Therefore, crystalline GST has the characteristic of high absorption in the mid-infrared band. Based on these advantages, GST is an ideal material that can be used for infrared selective thermal emitters.

[0006] At present, the research on spectral radiation modulation by researchers is becoming increasingly mature, and breakthroughs have been made in fields such as radiative cooling and energy harvesting technologies. However, the application of metamaterials with spectrally tunable selective emission characteristics to infrared stealth technology is still immature. A typical method to achieve low infrared emissivity selectivity is a multi-layer infrared stealth material film, which includes a silicon substrate and high-index and low-index material layers alternately coated on the surface of the silicon substrate. However, this method also has its limitations. This infrared stealth film has a complex structure and a relatively thick thickness, which is not conducive to large-area preparation, and the material layers are prone to peeling off under high-temperature environments, affecting the performance of infrared stealth. Since the metal-insulator-metal structure was proposed in 2008, metamaterials have been used in the development of narrowband or broadband absorbers. In recent years, a variety of infrared selective thermal emitters have been designed by scholars from various countries, but most thermal emitters have some drawbacks, such as low tunability, narrow spectral window, and irreversible control. Summary of the Invention

[0007] In order to achieve infrared stealth efficiently, the present invention designs a tunable infrared selective thermal emitter based on a cylindrical structure array. The structure of the present invention is simple. In the atmospheric windows of 3-5 μm and 8-14 μm, the average emissivities are approximately 0.20 and 0.18 respectively, and the average emissivity in the non-atmospheric window of 5-8 μm is approximately 0.80; it is not affected by the polarization of the light source and has good emission effects within the incident angle range of 0°-60°; in addition, the addition of the phase change material GST enables the thermal emitter to not only meet the requirements of low emissivity and radiative heat dissipation, but also tune the infrared emissivity spectrum to achieve switching between infrared "stealth" and "non-stealth" states, which is of great significance for achieving infrared stealth.

[0008] The object of the present invention is achieved as follows:

[0009] The tunable infrared selective thermal emitter based on a cylindrical structure array is composed of multiple adjustable structural units periodically arranged in the XOY plane. The sunlight is incident in the form of a plane wave. Each of the adjustable structural units successively includes a base layer made of Au material, a buffer layer made of GST material, and an antenna from bottom to top; the base layer and the buffer layer are square in shape, and the antenna is a cylindrical structure, which successively includes an upper structure made of Al material, a middle structure made of GST material, and a lower structure made of Al material from top to bottom, and the upper structure, the middle structure, and the lower structure form a cylindrical structure.

[0010] The relative positions of the defined base layer, buffer layer, and antenna are as follows: the plane where the base layer is located is the XOY plane, i.e., the horizontal plane. The center position of the base layer coincides with the origin of coordinates. Two pairs of opposite sides of the base layer are respectively parallel to the X-axis and the Y-axis. The buffer layer has the same shape, size, and placement direction as the base layer. In the cylindrical structure of the antenna, the center position coincides with the origin of coordinates.

[0011] For the above-mentioned tunable infrared selective thermal emitter based on a cylindrical structure array, the size of the base layer is 0.7μm×0.7μm×0.165μm; the size of the buffer layer is 0.7μm×0.7μm×0.07μm; the upper structure, middle structure, and lower structure of the upper antenna are all cylindrical structures. The outer diameter of the cylinder is D1 = 0.49μm, and the inner diameter is D2 = 0.32μm. The height of the upper structure is H1 = 0.11μm, the height of the middle structure is H2 = 0.1μm, and the height of the lower structure is H3 = 0.15μm.

[0012] Beneficial effects:

[0013] First, the tunable infrared selective thermal emitter based on a cylindrical structure array of the present invention has only three-layer structures: the base layer, the buffer layer, and the antenna, and the shapes are only square and cylindrical. The structure is simple and easy to process.

[0014] Second, for the tunable infrared selective thermal emitter based on a cylindrical structure array of the present invention, in the atmospheric windows of 3 - 5μm and 8 - 14μm, the average emissivities are about 0.20 and 0.18 respectively, and the average emissivity in the non-atmospheric window of 5 - 8μm is about 0.80. The low emissivity in the atmospheric window can reduce the infrared signature of the target, and the high emissivity in the non-atmospheric window can achieve the purpose of radiative heat dissipation.

[0015] Third, the tunable infrared selective thermal emitter based on a cylindrical structure array of the present invention is not affected by the polarization of the light source and has good emission effects in the incident angle range of 0° - 60°.

[0016] Fourth, for the tunable infrared selective thermal emitter based on a cylindrical structure array of the present invention, the phase change material GST is used, which can not only meet the requirements of low emissivity and radiative heat dissipation, but also tune the infrared emissivity spectrum to achieve the switching between infrared "stealth" and "non-stealth" states. Brief description of the drawings

[0017] Figure 1 It is a three-dimensional structure schematic diagram of the tunable infrared selective thermal emitter based on a cylindrical structure array of the present invention.

[0018] Figure 2 It is a three-dimensional structure schematic diagram of a single adjustable structure unit.

[0019] Figure 3 Schematic diagram of the relative positions of the base layer, buffer layer and antenna.

[0020] Figure 4 This is a screenshot of the simulation software interface of the present invention.

[0021] Figure 5 for Figure 4 The emission effect curve graph in .

[0022] Figure 6 This is the curve showing the influence of the height change of the upper structure and the middle structure on the emissivity.

[0023] Figure 7 This is the curve showing the effect of changes in the outer diameter of the cylindrical structure on the emissivity.

[0024] Figure 8 This is the curve of the effect of changes in sunlight incident angle on emissivity.

[0025] Figure 9 This is the curve of the influence of the change of sunlight polarization angle on emissivity.

[0026] Figure 10 This is the curve showing the effect of GST crystallization rate change on emissivity.

[0027] In the figure: 1 base layer, 2 buffer layer, 3 antenna, 3-1 upper structure, 3-2 middle structure, 3-3 lower structure. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described in further detail below with reference to the accompanying drawings. Specific implementation method 1

[0030] The tunable infrared selective thermal emitter based on the cylindrical structure array in this specific embodiment is composed of multiple adjustable structural units arranged periodically in the XOY plane. The sunlight is incident in the form of a plane wave, such as Figure 1 As shown, each of the adjustable structural units is composed of a base layer 1 of Au material, a buffer layer 2 of GST material, and an antenna 3 from bottom to top; the base layer 1 and the buffer layer 2 are square in shape, and the antenna 3 is a cylindrical structure, which includes an upper structure 3-1 of Al material, a middle structure 3-2 of GST material, and a lower structure 3-3 of Al material from top to bottom. The upper structure 3-1, the middle structure 3-2, and the lower structure 3-3 form a cylindrical structure, as shown in FIG. Figure 2 shown.

[0031] The relative positions of the base layer 1, the buffer layer 2 and the antenna 3 are defined as follows: Figure 3As shown: the plane where the base layer 1 is located is the XOY plane, that is, the horizontal plane, the center position of the base layer 1 coincides with the coordinate origin, the two sets of opposite sides of the base layer 1 are parallel to the X axis and the Y axis, respectively, the buffer layer 2 has the same shape, size and placement direction as the base layer 1, and in the cylindrical structure of the antenna 3, the center position coincides with the coordinate origin. Specific implementation method 2

[0033] The tunable infrared selective heat emitter based on the cylindrical structure array in this specific embodiment further defines the sizes of the base layer 1, the buffer layer 2 and the antenna 3 on the basis of the specific embodiment 1, such as Figure 3 As shown, the size of the base layer 1 is 0.7μm×0.7μm×0.165μm, and the height of the base layer 1 is H5=0.165μm; the size of the buffer layer 2 is 0.7μm×0.7μm×0.07μm, and the height of the buffer layer 2 is H4=0.07μm; the upper structure 3-1, the middle structure 3-2 and the lower structure 3-3 are all cylindrical structures, the outer diameter of the cylinder is D1=0.49μm, the inner diameter is D2=0.32μm, the height of the upper structure 3-1 is H1=0.11μm, the height of the middle structure 3-2 is H2=0.1μm, and the height of the lower structure 3-3 is H3=0.15μm. Specific implementation method three

[0035] The tunable infrared selective heat emitter based on the cylindrical structure array in this specific embodiment is simulated and tested on the heat emitter using FDTD-Solutions software on the basis of the specific embodiment 2. The simulation interface is as follows: Figure 4 As shown, Figure 4 The emission effect curve in Figure 5 As shown, according to Kirchhoff's law, the absorptivity A is equal to the emissivity ε, and using:

[0036]

[0037] Calculates the average emissivity of a thermal emitter.

[0038] in, is the average emissivity of the thermal emitter, is the average absorptivity of the thermal emitter, A is the absorptivity of the thermal emitter, which is a function of the wavelength λ of the incident light, λ is the wavelength of the incident light, and λ max is the maximum value within the wavelength range of the incident light, λ min It is the minimum value within the wavelength range of the incident light;

[0039] It can be calculated from the above formula that in the atmospheric windows of 3 - 5μm and 8 - 14μm, the average emissivities are approximately 0.20 and 0.18 respectively, and the average emissivity in the non - atmospheric window of 5 - 8μm is approximately 0.80. Specific Embodiment Four

[0041] For the tunable infrared selective thermal emitter based on the cylinder - structure array under this specific embodiment, on the basis of Specific Embodiment Two, the influence of the change in the height H2 of the middle layer structure 3 - 2 in the antenna 3 on the emissivity is simulated and tested. When the height H2 changes from 0μm to 0.2μm, the emissivity curve is as Figure 6 shown. The simulation results show that when the height is less than 0.1μm, there is only one resonance peak. As the height increases, two resonance peaks appear, and the positions of the resonance peaks gradually exhibit a blue shift. When the height is higher than 0.1μm, the emissivity in the 3 - 5μm band increases. By comparing the influence of the change in antenna height on the emissivity, it is found that when the height is equal to 0.1μm, the emissivity spectrum of the thermal emitter better meets the requirements of infrared stealth. This further proves the rationality of the parameters of the tunable infrared selective thermal emitter based on the cylinder - structure array of the present invention. Specific Embodiment Five

[0043] For the tunable infrared selective thermal emitter based on the cylinder - structure array under this specific embodiment, on the basis of Specific Embodiment Two, the influence of the change in the outer diameter D1 of the cylinder structure in the antenna 3 on the emissivity is simulated and tested. When the length changes from 0.45μm to 0.53μm, the emissivity curve is as Figure 7 shown. The simulation results show that as the outer diameter increases, the position of the resonance peak gradually exhibits a blue shift. When the outer diameter is 0.49μm, the resonance peaks of the thermal emitter are concentrated in the non - atmospheric window, and the emissivity in the atmospheric window remains low. By comparing the influence of the size of the outer diameter of the antenna cylinder on the emissivity, it is found that when the outer diameter is 0.49μm, the emissivity spectrum of the thermal emitter better meets the requirements of infrared stealth. This proves the rationality of the parameters of the tunable infrared selective thermal emitter based on the cylinder - structure array of the present invention. Specific Embodiment Six

[0045] For the tunable infrared selective thermal emitter based on the cylinder - structure array under this specific embodiment, on the basis of Specific Embodiment Two, the influence of the change in the incident angle of sunlight on the emissivity is simulated and tested at incident angles of 0°, 10°, 20°, 30°, 40°, 50° and 60° respectively. As Figure 8As shown, the simulation results indicate that when the incident angle is less than 50°, the emissivity curve of the non-atmospheric window does not change significantly, and the emissivity of the atmospheric window increases slightly; when the incident angle is greater than 50°, the emissivity of the atmospheric window increases, which shows that the tunable infrared selective thermal emitter based on the cylindrical structure array of the present invention has good wide-angle performance. Specific Embodiment VII

[0047] Based on the tunable infrared selective thermal emitter of the cylindrical structure array in this specific embodiment, on the basis of Specific Embodiment II, the influence of the change of the solar polarization angle on the emissivity is simulated and tested at the polarization angles of 0°, 15°, 30°, 45°, 60°, 75° and 90° respectively, as Figure 9 shown. The simulation results show that when the polarization angle of the light source is changed, the emissivity curve of the thermal emitter does not change, and the overall performance is polarization-insensitive. Specific Embodiment VIII

[0049] Based on the tunable infrared selective thermal emitter of the cylindrical structure array in this specific embodiment, on the basis of Specific Embodiment II, the influence of the change of the GST crystallization rate on the emissivity is simulated and tested at the crystallization rates of 0%, 20%, 40%, 60%, 80% and 100% respectively, as Figure 10 shown. The results show that as the crystallization rate increases continuously, the position of the resonance peak gradually redshifts. When in the crystalline state, the resonance peaks are mainly concentrated in the non-atmospheric window, and the atmospheric window has a low emissivity, meeting the requirements of the emissivity spectrum for infrared stealth. The simulation results show that the tunable infrared selective thermal emitter based on the cylindrical structure array of the present invention realizes the switching between the infrared "stealth" and "non-stealth" states.

Claims

1. Tunable infrared selective thermal emitter based on a cylinder structure array, characterized in that It is composed of multiple adjustable structural units arranged periodically in the XOY plane. Sunlight is incident in the form of a plane wave. Each of the adjustable structural units includes, from bottom to top, a base layer (1) made of Au material, a buffer layer (2) made of GST material, and an antenna (3). The base layer (1) and the buffer layer (2) are square in shape, and the antenna (3) is a cylindrical structure, which includes, from top to bottom, an upper structure (3-1) made of Al material, a middle structure (3-2) made of GST material, and a lower structure (3-3) made of Al material. The upper structure (3-1), the middle structure (3-2), and the lower structure (3-3) form a cylindrical structure. Define the relative positions of the base layer (1), the buffer layer (2), and the antenna (3) as follows: The plane where the base layer (1) is located is the XOY plane, that is, the horizontal plane. The center position of the base layer (1) coincides with the coordinate origin. Two pairs of opposite sides of the base layer (1) are respectively parallel to the X-axis and the Y-axis. The buffer layer (2) has the same shape, size, and placement direction as the base layer (1). In the cylindrical structure of the antenna (3), the center position coincides with the coordinate origin.

2. The tunable infrared selective thermal emitter based on the cylinder structure array according to claim 1, wherein The size of the base layer (1) is 0.7μm×0.7μm×0.165μm; the size of the buffer layer (2) is 0.7μm×0.7μm×0.07μm; the upper structure (3-1), the middle structure (3-2), and the lower structure (3-3) of the upper antenna (3) are all cylindrical structures. The outer diameter of the cylinder is D1 = 0.49μm, and the inner diameter is D2 = 0.32μm. The height of the upper structure (3-1) is H1 = 0.11μm, the height of the middle structure (3-2) is H2 = 0.1μm, and the height of the lower structure (3-3) is H3 = 0.15μm.

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