CN211826588U - Infrared broadband wave absorbing structure for radiation refrigeration - Google Patents
Infrared broadband wave absorbing structure for radiation refrigeration Download PDFInfo
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- CN211826588U CN211826588U CN201921713912.8U CN201921713912U CN211826588U CN 211826588 U CN211826588 U CN 211826588U CN 201921713912 U CN201921713912 U CN 201921713912U CN 211826588 U CN211826588 U CN 211826588U
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Abstract
The invention belongs to the field of infrared artificial electromagnetic metamaterials and radiation refrigeration, and particularly relates to an infrared broadband wave-absorbing structure for radiation refrigeration. The invention utilizes the metal film bottom layer structure to block transmission, utilizes impedance matching to reduce reflection, and realizes strong absorption of infrared electromagnetic waves of near infrared wave bands of 3-5 mu m and medium waves of 8-13 mu m in an atmospheric window and high reflection of other wave bands than the atmospheric window through a saw-tooth-shaped multilayer double-medium periodic structure. The basic unit comprises a metal bottom plate and a multilayer zigzag double-medium structure from bottom to top, wherein the metal bottom plate comprises a metal film, an upper medium of the double-medium structure is the metal film, a lower medium of the double-medium structure is a Ge or P semiconductor film, and the basic unit is periodically unfolded on an x-y two-dimensional plane. The invention can improve the wave absorbing capacity of the atmospheric window material and the reflection capacity of the non-atmospheric window material, improve the radiation refrigeration capacity of the material and meet the requirements of energy conservation and environmental protection.
Description
Technical Field
The invention belongs to the field of infrared artificial electromagnetic metamaterials and radiation refrigeration, and relates to an infrared broadband wave-absorbing structure for radiation refrigeration.
Background
The metamaterial is a composite material body with a sub-wavelength structure consisting of artificially constructed basic units, can exceed the limitation of intrinsic parameters of natural materials, realizes physical properties and functions which are not possessed by natural materials, and is collectively called as the metamaterial. The macroscopic material characteristics of the metamaterial are determined by the structure of the metamaterial rather than the intrinsic characteristics of the metamaterial, so the creation of the metamaterial introduces a brand new design concept to the material field, changes the conventional practice of what material is manufactured into what object in the past, creates a reverse design method, namely, the metamaterial with corresponding functions is manufactured according to the application requirements of electromagnetic waves, and has great historical significance in the field of material science.
Kirchhoff's law states that under thermal equilibrium conditions, the ratio of the radiation exitance of any object to its absorption ratio of radiation from a black body is constantly equal to the radiation exitance of a black body at the same temperature, the blackness, i.e., emissivity, of an object is equal to the absorption of that object at the same temperature, and the greater the radiation absorbing power of an object, the greater the radiation emitting power of an object. Thus, a good absorber is also a good emitter.
The infrared absorber can radiate energy to the cold outer space through an infrared transparent window of the atmosphere, so that passive radiation refrigeration is realized. The infrared transparent windows of the atmosphere range from 3 to 5 μm, and 8 to 13 μm infrared absorbers with this spectrally selective absorption can also be used as imaging and detectors, with the advantage of low background noise. Therefore, the selective frequency band of the absorber is widened to cover two main transparent windows of the atmosphere, and the method has important significance for the application of the propulsion absorber in the field of radiation refrigeration.
The existing radiation refrigeration material has the defects of not wide bandwidth, not strong absorption rate, poor radiation refrigeration effect and the like.
Disclosure of Invention
The invention provides a dual-band metamaterial for radiation refrigeration, aiming at the technical problems, and the dual-band metamaterial can enable the wave-absorbing metamaterial to have wide-band strong absorption in a specific wave band and high reflection in other wave bands.
In order to achieve the purpose, a broadband metamaterial absorber is designed, absorption of near-infrared wave bands of 3-5 mu m and medium-wave infrared electromagnetic waves of 8-13 mu m of an atmospheric window is achieved, and high reflection of other wave bands except the atmospheric window is achieved.
An infrared broadband wave-absorbing structure for radiation refrigeration is characterized in that a basic unit consisting of a metal bottom plate and a multilayer zigzag double-medium structure is arranged from bottom to top, and the basic unit is periodically unfolded on an x-y two-dimensional plane: the metal bottom plate is composed of a metal film, the thickness of the metal bottom plate is larger than the skin depth of infrared band electromagnetic waves in metal and is at least larger than 50 nm; the upper medium in the double-medium structure is a metal film with the thickness of 10 nm-100 nm, the lower medium is a Ge or P semiconductor film with the thickness of 10-100 nm, the number of layers of the double-medium structure is 13-50, and the width and the length of a basic unit of the double-medium structure are 1 mu m-3 mu m.
The basic unit structure is periodically spread on an x-y plane, and the period is 0.5-5 mu m.
The metal bottom plate is made of a metal film, such as gold, silver, copper and aluminum metal, and the thickness of the metal bottom plate is larger than the skin depth of infrared band electromagnetic waves in the metal and is larger than 50 nm.
The upper medium in the multilayer double-film structure is a metal film with the thickness of 10 nm-100 nm, the lower medium is a Ge or P semiconductor film with the thickness of 10-100 nm, and the number of layers of the double-film structure is 13-30.
The double-medium structure is etched into a pyramid shape, the screenshot of the double-medium structure on an x-z plane is a trapezoid, the width of the uppermost layer of the trapezoid is 0.2-4 mu m, and the width of the lowermost layer of the trapezoid is 0.3-4.5 mu m.
The transmission is blocked by utilizing a metal film bottom layer structure, the reflection is reduced by utilizing impedance matching, the absorption of 3-5 mu m near-infrared wave band and 8-13 mu m medium wave infrared electromagnetic wave of an atmospheric window is realized through a saw-tooth-shaped multilayer double-medium periodic structure, and meanwhile, the high reflection of other wave bands other than the atmospheric window is realized.
According to the absorption A being 1-transmission T-reflection R, in order to reduce the transmission, a metal bottom plate is added on the bottommost layer, the bottom plate is composed of a metal thin film, the thickness of the metal thin film is larger than the penetration depth of an infrared wave band, and the transmission T being 0; in order to reduce the reflection of the atmospheric window, the wave impedance Z of the structure in this wavelength band is matched with the wave impedance Z of the external environment, and the wave impedance Z of the structure in the non-atmospheric window is not matched with the wave impedance of the external environment.
Drawings
Fig. 1 is a schematic diagram of a periodic unit of the wave-absorbing structure.
Fig. 2 is a schematic view of a wave-absorbing structure.
FIG. 3 is a graph of the infrared absorption reflection transmission of example 1.
Fig. 4 is an infrared absorption reflection transmission diagram of example 2.
Detailed Description
The infrared selectable waveband metamaterial absorber is composed of a periodic unit structure, as shown in fig. 1, fig. 1 is a cross-sectional view of one periodic unit of the designed absorber in an x-z plane, each unit is provided with a metal bottom plate 3 and a plurality of layers of double films from bottom to top, and the plurality of layers of double films are formed by alternately stacking a dielectric layer material 1 and a metal film 2.
Fig. 2 is a 3D top view of an absorber designed to resemble a pyramid in the basic cells. The basic unit is periodically spread on an x-y two-dimensional plane.
Example 1, the basic unit is periodically spread on an x-y two-dimensional plane, and the period of the periodic unit on the x-y plane is 2.4 μm.
In fig. 2 the metal bottom plate 3 is gold and has a thickness of 100 nm.
In the double-film structure in fig. 2, the upper-layer medium 2 is gold and has a thickness of 25nm, the lower-layer medium 1 is a Ge film and has a thickness of 55nm, and the number of layers of the multilayer double-film structure is 16.
The designed absorber is trapezoidal in x-z cross section, the width of the bottommost layer of the trapezoid is 1.84 μm, and the width of the topmost layer is 0.8 μm.
FIG. 3 is a reflection and transmission diagram of infrared absorption in example 1, in which the absorption is 50% or more in the mid-wave infrared of 3.3 to 5.1 μm and the far-wave infrared of 6.8 to 15.3 μm.
Example 2, the basic unit is periodically spread on an x-y two-dimensional plane, and the period of the periodic unit on the x-y plane is 3 μm. The metal back plate 3 is silver and has a thickness of 100 nm.
In the double-film structure, the upper medium is a metal film gold 2 with the thickness of 25nm, the lower medium 1 is a P film with the thickness of 45nm, and the number of layers of the multilayer double-medium structure is 20.
The designed absorber is trapezoidal in x-z cross section, the width of the bottommost layer of the trapezoid is 1.84 μm, and the width of the topmost layer is 0.7 μm.
FIG. 4 is a reflection and transmission diagram of infrared absorption in example 2, in which the absorption is 50% or more in the mid-wave infrared of 3.8 to 6 μm and the far-wave infrared of 7.1 to 18 μm.
Claims (4)
1. An infrared broadband wave-absorbing structure for radiation refrigeration is characterized in that a basic unit consisting of a metal bottom plate and a multilayer zigzag double-medium structure is arranged from bottom to top, and the basic unit is periodically unfolded on an x-y two-dimensional plane: the metal bottom plate is composed of a metal film, the thickness of the metal bottom plate is larger than the skin depth of infrared band electromagnetic waves in metal and is at least larger than 50 nm; the upper medium in the double-medium structure is a metal film with the thickness of 10 nm-100 nm, the lower medium is a Ge or P semiconductor film with the thickness of 10-100 nm, the number of layers of the double-medium structure is 13-50, and the width and the length of a basic unit of the double-medium structure are 1 mu m-3 mu m.
2. The infrared broadband wave-absorbing structure for radiation refrigeration of claim 1, wherein: the metal bottom plate material is any one of metal gold, silver, copper and aluminum.
3. The infrared broadband wave-absorbing structure for radiation refrigeration of claim 1, wherein: the basic unit structure is periodically unfolded on an x-y plane, the period is 0.5-5 mu m, the double-medium structure is etched into a pyramid shape, the screenshot on the x-z plane is a trapezoid, the width of the uppermost layer of the trapezoid is 0.2-4 mu m, and the width of the lowermost layer of the trapezoid is 0.3-4.5 mu m.
4. The infrared broadband wave-absorbing structure for radiation refrigeration of claim 1, wherein: the transmission is blocked by utilizing a metal film bottom layer structure, the reflection is reduced by utilizing impedance matching, the absorption of 3-5 mu m near-infrared wave band and 8-13 mu m medium wave infrared electromagnetic wave of an atmospheric window is realized through a saw-tooth-shaped multilayer double-medium periodic structure, and meanwhile, the high reflection of other wave bands other than the atmospheric window is realized.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110737034A (en) * | 2019-10-14 | 2020-01-31 | 上海海事大学 | infrared broadband wave-absorbing structure for radiation refrigeration and design method thereof |
| CN112563759A (en) * | 2020-11-30 | 2021-03-26 | 合肥工业大学 | Dual-frequency ultra-wideband metamaterial wave-absorbing unit and wave-absorbing body |
| CN113314849A (en) * | 2021-04-20 | 2021-08-27 | 上海海事大学 | Periodic unit of metamaterial broadband wave absorber and metamaterial broadband wave absorber |
| CN113437528A (en) * | 2021-07-07 | 2021-09-24 | 东莞理工学院 | Broadband wave-absorbing metamaterial with adjustable narrow-band reflection window |
-
2019
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110737034A (en) * | 2019-10-14 | 2020-01-31 | 上海海事大学 | infrared broadband wave-absorbing structure for radiation refrigeration and design method thereof |
| CN112563759A (en) * | 2020-11-30 | 2021-03-26 | 合肥工业大学 | Dual-frequency ultra-wideband metamaterial wave-absorbing unit and wave-absorbing body |
| CN112563759B (en) * | 2020-11-30 | 2022-06-10 | 合肥工业大学 | Dual-frequency ultra-wideband metamaterial wave-absorbing unit and wave-absorbing body |
| CN113314849A (en) * | 2021-04-20 | 2021-08-27 | 上海海事大学 | Periodic unit of metamaterial broadband wave absorber and metamaterial broadband wave absorber |
| CN113437528A (en) * | 2021-07-07 | 2021-09-24 | 东莞理工学院 | Broadband wave-absorbing metamaterial with adjustable narrow-band reflection window |
| CN113437528B (en) * | 2021-07-07 | 2022-11-11 | 东莞理工学院 | Broadband wave-absorbing metamaterial with adjustable narrow-band reflection window |
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