A long-wave infrared light absorber based on phase change materials and MIM structure

Abstract

This application provides a long-wave infrared light absorber based on phase change materials and MIM structures, belonging to the field of integrated photonic devices. The absorber includes a reflective layer, a double dielectric layer, and a metasurface layer. The metasurface layer allows light waves to enter the double dielectric layer through diffraction. The reflective layer and the metasurface layer form two reflective surfaces, allowing the light waves to undergo multiple reflections and achieve FP-cavity resonance. When the metasurface layer is crystalline and the polarization state of the light wave is not parallel to that of the metasurface layer, both the reflective layer and the metasurface layer possess metallic properties, enabling plasmon resonance when the frequency of the incident light wave matches the collective oscillation frequency of free electrons in the metal. Both FP-cavity resonance and plasmon resonance lead to the localization and enhancement of the electromagnetic field within the double dielectric layer, thereby enhancing the absorption of light waves. This application achieves reversible switching between two light wave absorption states by changing the phase state of the phase change material.

Description

Technical Field

[0001] This application belongs to the field of integrated photonic devices, and more specifically, relates to a long-wave infrared light absorber based on phase change materials and MIM structures. Background Technology

[0002] Thermal radiation is the electromagnetic radiation emitted by an object due to its temperature. All objects emit electromagnetic waves according to their temperature; this radiation includes infrared, visible light, and ultraviolet light. According to Planck's law of blackbody radiation, the thermal radiation of an object is mainly concentrated in the infrared band, especially 8µm-14µm (LWIR, long-wave infrared band). Simultaneously, the Earth's atmosphere has multiple windows, one of which is the long-wave infrared band. Within these transparent windows, electromagnetic waves can propagate over relatively long distances with relatively low loss. Thermal radiation manipulation refers to controlling the emission, absorption, transmission, and reflection of thermal radiation from an object through specific materials, structures, or technologies. This manipulation can be performed at different wavelengths, temperatures, and directions to achieve specific thermal management and energy conversion objectives. Thermal radiation manipulation technology has wide applications in radiation shielding, thermal stealth technology, thermal radiation detection and imaging, and thermal radiation spectral analysis.

[0003] Infrared absorption is a crucial indicator in infrared imaging and detection applications. To achieve efficient infrared absorption, specialized device structures are required. In recent years, with the rapid development of nanophotonics, the optical properties of metamaterials have been designed using structures such as photonic crystals and metasurfaces. Among these, the metasurface-type MIM structure ("metal-insulator-metal" structure, a commonly used multilayer structure in electronics and optoelectronics where two metal layers are separated by an insulating layer (or dielectric layer)) has been extensively studied. However, infrared absorbers fabricated based on traditional MIM structures cannot be modified once fabricated. This results in limited device performance, high sensitivity to structural parameters, low fabrication tolerance, and limited practicality. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application aims to provide a long-wave infrared absorber based on phase change materials and MIM structures, which solves the problems of irreversible manipulation and low fabrication tolerance of existing metasurface absorbers.

[0005] To achieve the above objectives, in a first aspect, this application provides a long-wave infrared light absorber based on phase change materials and MIM structures, comprising: a reflective layer, a dual dielectric layer, and a metasurface layer;

[0006] The dual dielectric layer is a transparent dielectric material in the long-wave infrared band; the metasurface layer material is a phase change material that exhibits metallic properties in the crystalline state and dielectric properties in the amorphous state; the reflective layer is a metallic material that reflects long-wave infrared waves; the metasurface layer has a periodic structure.

[0007] The metasurface layer is used to allow light waves to enter the double dielectric layer through diffraction; the reflective layer and the metasurface layer form two reflective surfaces, which are used to allow light waves to undergo multiple reflections and generate FP cavity resonance; when the metasurface layer is crystalline and the polarization state of the light wave is not parallel to the metasurface layer, the reflective layer and the metasurface layer simultaneously possess metallic properties, which are used to generate plasma resonance when the frequency of the incident light wave matches the collective oscillation frequency of free electrons in the metal; wherein, the period of the metasurface layer is not greater than the wavelength of the light wave;

[0008] Both FP cavity resonance and plasma resonance lead to the localization and enhancement of the electromagnetic field within the double dielectric layer, thereby enhancing the absorption of light waves.

[0009] More preferably, the metasurface layer is a grating type with a period on a subwavelength scale and an operating wavelength in the long-wave infrared band, with a wavelength range of 8µm-14µm.

[0010] More preferably, the material of the metasurface layer is the phase change material In3SbTe2, and the reversible change of its phase state is achieved by changing its temperature through annealing or laser direct writing;

[0011] When the metasurface material is in a crystalline state, it and the reflective layer are reflective, which is used to generate a resonance mode, confining the energy of the light wave within the double dielectric layer, which is a high absorption state. When the metasurface material is in an amorphous state, it is used to transmit part of the energy of the light wave, which is a low absorption state.

[0012] More preferably, the dual dielectric layer includes a first dielectric layer and a second dielectric layer; the material of the first dielectric layer adjacent to the reflective layer is silicon or germanium; and the material of the second dielectric layer adjacent to the metasurface layer is silicon nitride.

[0013] More preferably, the reflective layer material is gold, silver, or aluminum.

[0014] Secondly, based on the phase change material and MIM structure long-wave infrared light absorber provided in this application, this application provides a corresponding long-wave infrared light absorption modulation method, specifically as follows:

[0015] When it is necessary to enhance the absorption of long-wave infrared light, the metasurface layer can be made crystalline by annealing or laser direct writing, so that the metasurface layer exhibits metallic properties.

[0016] When the polarization state of the light wave is not parallel to that of the metasurface layer, the light wave enters the double dielectric layer through diffraction and undergoes multiple reflections in the reflective layer and the metasurface layer, resulting in FP cavity resonance. At the same time, the frequency of the light wave is matched with the collective oscillation frequency of free electrons in the metasurface layer and the reflective layer, resulting in plasma resonance. Among these, FP cavity resonance and plasma resonance lead to the localization and enhancement of the electromagnetic field in the double dielectric layer, thereby enhancing the absorption of the light wave.

[0017] When it is necessary to reduce the absorption of long-wave infrared light, the metasurface layer is made amorphous by annealing or laser direct writing, which prevents plasma resonance. The metasurface layer is used to partially transmit light waves, reducing the resonance intensity of the FP cavity, thereby reducing the absorption of long-wave infrared light.

[0018] More preferably, the reflection or transmission of light wavelength, the position of the resonance peak, the position of the FP cavity resonance peak, and the absorption bandwidth of light wave are adjusted by adjusting the period and linewidth of the metasurface layer.

[0019] When the period of the grating matches the wavelength of the light wave, Bragg diffraction occurs. The smaller the period of the metasurface layer, the shorter the corresponding Bragg diffraction wavelength. The smaller the period of the grating, the higher the frequency of plasma resonance and FP cavity resonance is supported, which in turn affects the position of the plasma resonance peak and FP cavity resonance peak. The smaller the duty cycle of the grating, the larger the absorption bandwidth of the light wave and the lower the height of the absorption peak. The duty cycle is the ratio of the linewidth of the grating to its period.

[0020] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:

[0021] This application provides a long-wave infrared light absorber based on phase change materials and MIM structures, including a reflective layer, a first dielectric layer, a second dielectric layer, and a metasurface layer; wherein, the reflective layer includes a metallic material with high reflectivity in the infrared band; the first dielectric layer and the second dielectric layer include transparent dielectric materials in the long-wave infrared band; the metasurface layer material includes a phase change material; by designing the MIM structure of the phase change material metasurface layer, the FP cavity resonance mode and the magnetic resonance mode are coupled in the same band, which can achieve polarization broadband absorption in the long-wave infrared band.

[0022] This application provides a method for controlling the absorption of long-wave infrared light. By changing the phase state of the phase change material, the device can reversibly switch between two absorption states. Specifically, when the metasurface material is in a crystalline state, light waves enter the double dielectric layer through diffraction, undergoing multiple reflections at the reflective and metasurface layers, resulting in FP-cavity resonance. Simultaneously, the frequency of the light wave is matched with the collective oscillation frequency of free electrons in the metasurface and reflective layers, resulting in plasmon resonance. The FP-cavity resonance and plasmon resonance lead to the localization and enhancement of the electromagnetic field within the double dielectric layer, thereby enhancing the absorption of light waves, which is a high absorption state. When the metasurface material is in an amorphous state, plasmon resonance cannot occur, and the metasurface layer partially transmits light waves, reducing the FP-cavity resonance intensity and thus weakening the absorption of long-wave infrared light, which is a low absorption state.

[0023] This application provides a long-wave infrared light absorber based on phase change materials and MIM structure. Since the metasurface layer structure is grating type, the absorber has polarization properties in its absorption of light waves. When the polarization state of the incident light wave is perpendicular to the grating, strong plasma resonance will be generated. When the polarization state of the incident light wave is parallel to the grating, plasma resonance cannot be generated. It has a large contrast in the absorption of polarized waves in two different directions and can be used in anti-counterfeiting and encryption systems.

[0024] The long-wave infrared light absorber structure based on phase change materials and MIM structure provided in this application has a simple structure, thin thickness, and small size. The first dielectric layer is made of a material with a large real part of refractive index in the long-wave infrared band, and the second dielectric layer is made of a material with a large imaginary part of refractive index in the long-wave infrared band. The phase change material can undergo phase change quickly, and the fabrication process of the device is reduced.

[0025] This application provides a structure for a long-wave infrared light absorber based on phase change materials and MIM structure. Since the absorption principle of the device is resonant cavity resonance, the thickness of the reflective layer, dielectric layer and metasurface layer are all on the nanometer scale. Any material, including flexible materials, can be used as a substrate, enabling the absorber to have wide applications in wearable devices, curved solar cell surfaces and electronic devices. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the long-wave infrared light absorber based on phase change material and MIM structure provided in Embodiment 1 of this application;

[0027] Figure 2 This is the absorption spectrum of the long-wave infrared light absorber based on phase change material and MIM structure provided in Embodiment 1 of this application;

[0028] Figure 3This is a magnetic field distribution diagram at three absorption peaks of the long-wave infrared light absorber based on phase change material and MIM structure provided in Embodiment 1 of this application;

[0029] Figure 4 This is a schematic diagram of the long-wave infrared light absorber based on phase change material and MIM structure provided in Embodiment 2 of this application;

[0030] Figure 5 This is the absorption spectrum of the long-wave infrared light absorber based on phase change material and MIM structure provided in Embodiment 2 of this application;

[0031] Figure 6 This is a magnetic field distribution diagram at three absorption peaks of a long-wave infrared light absorber based on phase change material and MIM structure provided in Embodiment 2 of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Furthermore, the technical features involved in the various embodiments described below can be combined with each other as long as they do not conflict with each other.

[0033] To achieve the above objectives, firstly, this application provides a long-wave infrared light absorber based on a phase change material and a MIM structure, specifically a vertically structured, reversibly operable phase change metasurface MIM structure, such as... Figure 1 As shown, it includes, from bottom to top: a reflective layer, a dual dielectric layer, and a metasurface layer;

[0034] The reflective layer is a metallic material with high reflectivity in the long-wave infrared band; the first dielectric layer and the second dielectric layer are transparent dielectric materials in the long-wave infrared band; and the metasurface layer material is a phase change material.

[0035] More preferably, the periodic metasurface layer structure allows light waves to enter the dielectric layer through diffraction, simultaneously altering the propagation path and phase of the light waves, thereby affecting the absorption characteristics. The bottom reflective layer and the top metasurface layer form two parallel reflective layers. After the light waves enter the dielectric layer, they undergo multiple reflections between the two reflective layers, resulting in Fabry-Perot (FP cavity) resonance. This resonance leads to strong light absorption at specific wavelengths because the reflected light waves undergo constructive interference within the dielectric layer, thus confining the energy of the light waves within the dielectric layer and enhancing the device's absorption of light waves. Simultaneously, since both the upper and lower reflective layers are metallic, when the frequency of the incident light wave matches the collective oscillation frequency of the free electrons in the metal, plasmon resonance occurs. In this case, the electrons in the metal oscillate at the same frequency, leading to the localization and enhancement of the electromagnetic field, thereby enhancing the absorption of light waves.

[0036] The function of the metasurface layer is to allow incident light to enter the resonant cavity through diffraction. To improve diffraction efficiency, the period of the metasurface layer is on a subwavelength scale. In this embodiment, the metasurface layer morphology is a grating type, and the device operates in the long-wave infrared band with wavelengths of 8µm-14µm. Therefore, the grating period is no greater than 7µm. When the grating period matches the wavelength of the incident light, Bragg diffraction occurs, causing light of a specific wavelength to be strongly reflected or transmitted. The smaller the period, the shorter the corresponding Bragg wavelength. The grating period also affects... The positions of the plasma resonance peak and the FP cavity resonance peak are influenced by the fact that gratings with shorter periods tend to support higher frequency resonance modes, thus affecting the position of the absorption peak. The size of the grating period also affects the width of the absorption band; the smaller the duty cycle of the grating, the wider the absorption bandwidth and the lower the height of the absorption peak. The duty cycle is the ratio of the grating linewidth to the period. The combination of linewidth and period affects the electromagnetic response of the grating, including the position, intensity, and bandwidth of the absorption peak. By adjusting the grating period and linewidth, the absorption characteristics of the grating for different wavelengths of light can be optimized.

[0037] More preferably, the material of the metasurface structure in the metasurface layer is a phase change material. By changing the temperature of the phase change material through annealing or laser direct writing, the phase state of the phase change material can be reversibly changed, and this change is non-volatile. Since the phase change material has different optical dielectric constants in different phase states, the device has different optical properties depending on the phase state of the phase change material. In this embodiment, the material of the metasurface layer is the phase change material In3SbTe2 (IST for short), which exhibits strong metallic properties in the crystalline state and dielectric properties in the amorphous state. When IST is in the crystalline state, it has a large imaginary part of dielectric constant and a small real part of dielectric constant, and has strong reflectivity to light waves. At this time, a strong resonance mode will be excited between the metasurface layer and the reflective layer, so that the energy of the light wave is confined in the dielectric layer, and the device is in a high absorption state. When IST is in the amorphous state, the energy of the light wave will partially transmit through the metasurface layer, and the device is in a low absorption state.

[0038] More preferably, both the first and second dielectric layers are made of materials that are transparent in the long-wave infrared band. The purpose of using a double dielectric layer is to reduce the thickness of the device and improve its absorption rate. Since the resonant wavelength is related to the product of the dielectric layer thickness and refractive index, using a material with a large real part of refractive index in the long-wave infrared band can effectively reduce the overall thickness of the device. The first dielectric layer is made of silicon (refractive index 3.47) or germanium (refractive index 4). Meanwhile, the function of the second dielectric layer is to improve the overall absorption rate of the device. Therefore, the second dielectric layer is made of a material with a large imaginary part of refractive index in the long-wave infrared band. In this embodiment, the material used for the second dielectric layer is silicon nitride.

[0039] More preferably, the material of the reflective layer is a metallic material with high reflectivity in the long-wave infrared band, such as gold, silver, and aluminum.

[0040] Secondly, this application utilizes the structural parameters of a long-wave infrared light absorber based on phase change materials and MIM structures to couple the FP cavity resonant mode and the electromagnetic resonant mode into the same wavelength band, thereby achieving wide-band polarization absorption in the long-wave infrared band. Depending on the phase change mechanism of the phase change material and the metasurface fabrication process, this application provides two device structures, with specific embodiments as follows:

[0041] Example 1:

[0042] like Figure 1 The diagram shows a cross-sectional view of the device. When the IST is switched between different crystal phases by annealing phase change, the fabrication process used is photolithography. At this time, the cross-section of the metasurface layer is a rectangular array, while the area outside the phase change material array is all air.

[0043] The long-wave infrared light absorber based on phase change material and MIM structure provided in Example 1 has the following specific parameters: the thickness of the bottom Au layer is 100nm, the intermediate dielectric layer includes 330nm Si3N4 and 300nm Ge, the thickness of the upper IST grating is 100nm, the grating period is 5µm, and the grating linewidth is 1µm.

[0044] The structure was input into the simulation software COMSOL and simulation was performed to obtain the absorption rates of crystalline and amorphous IST as devices under the upper grating array in the 7µm-15µm wavelength range. The absorption spectra are as follows: Figure 2 As shown, the thick lines represent the absorption spectra of crystalline IST absorbers in the 7µm-15µm wavelength range, while the thin lines represent the absorption spectra of amorphous IST absorbers in the same wavelength range. Figure 2 It can be seen that the crystalline IST absorber has three absorption peaks in the entire LWIR band, namely 8.6um, 10.3um and 13.7um, and the device achieves broadband high absorption from 8.3um to 14.5um, with an absorption rate of over 80% and an absorption bandwidth of 6.2um, indicating that the device is in a high absorption state; while the amorphous IST has a lower absorption rate, indicating that the device is in a low absorption state.

[0045] The magnetic field distribution within the dielectric layer at the three absorption peaks of a crystalline IST absorber is as follows: Figure 3 As shown, the magnetic field at 8.6 μm is enhanced in the dielectric layer between the non-metasurface layer region and the reflective layer, and this resonance mode is the FP cavity resonance peak; the magnetic field at 13.7 μm is enhanced in the dielectric layer between the phase change material region and the reflective layer, and this resonance mode is the plasmon resonance peak.

[0046] Example 2

[0047] like Figure 4 The diagram shows a cross-sectional view of the device. When the IST is switched between different crystal phases using laser phase change, the process used is laser direct writing. Since the energy of the laser spot is Gaussian distributed in the lateral direction, that is, the energy gradually decreases from the center to the periphery, the laser energy at the edge is insufficient to make the phase change material completely undergo phase change. Therefore, the cross-section of the metasurface layer of the crystalline phase change material is an arc array, and the area outside the metasurface array of the crystalline phase change material is the amorphous phase change material.

[0048] The long-wave infrared light absorber based on phase change material and MIM structure provided in Example 2 has the following specific parameters: the thickness of the bottom Au layer is 100nm, the intermediate dielectric layer includes 300nm Si3N4 and 240nm Ge, the thickness of the upper IST grating is 100nm, the grating period is 5µm, and the grating linewidth is 1µm.

[0049] The structure was input into the simulation software COMSOL and simulations were performed. The absorption rates of crystalline and amorphous IST as devices under the upper grating array in the 7µm-15µm wavelength range were obtained, and the absorption spectra are as follows: Figure 5 As shown, the thick lines represent the absorption spectra of crystalline IST absorbers in the 7µm-15µm wavelength range, while the thin lines represent the absorption spectra of amorphous IST absorbers in the same wavelength range. Figure 5 It can be seen that the crystalline IST absorber has three absorption peaks in the entire LWIR band, namely 8.6um, 10.3um, and 13.6um. The device achieves broadband high absorption from 8.4um to 14.3um, with an absorption rate of over 80% and an absorption bandwidth of 5.9um. The device is in a high absorption state. In contrast, the amorphous IST has a lower absorption rate, and the crystal is in a low absorption state.

[0050] The magnetic field distribution within the dielectric layer at the three absorption peaks of a crystalline IST absorber is as follows: Figure 6 As shown, the magnetic field at 8.6 μm is enhanced in the dielectric layer between the non-metasurface region and the reflective layer, and this resonance mode is the FP cavity resonance peak; the magnetic field at 13.6 μm is enhanced in the dielectric layer between the phase change material region and the reflective layer, and this resonance mode is the plasmon resonance peak.

[0051] In summary, this application has the following advantages compared with the prior art:

[0052] This application provides a long-wave infrared light absorber based on phase change materials and a MIM structure, including a reflective layer, a first dielectric layer, a second dielectric layer, and a metasurface layer. The reflective layer comprises a metallic material with high reflectivity in the infrared band. The first and second dielectric layers comprise transparent dielectric materials in the long-wave infrared band. The metasurface layer material comprises a phase change material. By designing the MIM structure of the phase change material metasurface layer, the FP cavity resonant mode and the magnetic resonant mode are coupled in the same band, achieving wide polarization absorption in the long-wave infrared band. The device can reversibly switch between the two absorption states by changing the phase state of the phase change material.

[0053] This application provides a long-wave infrared light absorber based on phase change material and MIM structure. Since the metasurface layer structure is grating type, the absorber has polarization properties in its absorption of light waves, and has a large contrast in the absorption of two polarized waves with different directions. It can be used in anti-counterfeiting and encryption systems.

[0054] The long-wave infrared light absorber structure based on phase change material and MIM structure provided in this application has the advantages of simple structure, thin thickness and small size. The phase change material can undergo phase change quickly, and the fabrication process of the device is reduced.

[0055] This application provides a structure for a long-wave infrared light absorber based on phase change materials and MIM structure. Since the absorption principle of the device is resonant cavity resonance, the thickness of the reflective layer, dielectric layer and metasurface layer are all on the nanometer scale. Any material, including flexible materials, can be used as a substrate, enabling the absorber to have wide applications in wearable devices, curved solar cell surfaces and electronic devices.

[0056] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0057] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0058] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A long-wave infrared light absorber based on phase change materials and MIM structures, characterized in that, include: Reflective layer, dual dielectric layer and metasurface layer; The dual dielectric layer is a transparent dielectric material in the long-wave infrared band, used to reduce thickness and improve absorption rate; the metasurface layer material is a phase change material, exhibiting metallic properties in the crystalline state and dielectric properties in the amorphous state; the reflective layer is a metallic material that reflects long-wave infrared waves; the structure of the metasurface layer is a periodic structure. The metasurface layer allows light waves to enter the double dielectric layer via diffraction; the reflective layer and the metasurface layer form two reflective surfaces, allowing light waves to undergo multiple reflections and generate FP-cavity resonance; when the metasurface layer is crystalline and the polarization state of the light wave is not parallel to the metasurface layer, both the reflective layer and the metasurface layer possess metallic properties, enabling plasma resonance when the frequency of the incident light wave matches the collective oscillation frequency of free electrons in the metal; wherein, the period of the metasurface layer is not greater than the wavelength of the light wave; The material of the metasurface layer is the phase change material In3SbTe2, and its reversible phase change is achieved by changing its temperature through annealing or laser direct writing. When the metasurface material is in a crystalline state, it and the reflective layer are reflective, which generates a resonance mode, confining the energy of light waves within the dual dielectric layer, resulting in a high absorption state. When the metasurface material is in an amorphous state, it transmits some of the energy of light waves, resulting in a low absorption state. Both the FP cavity resonance and the plasma resonance lead to the localization and enhancement of the electromagnetic field within the double dielectric layer, thereby enhancing the absorption of light waves.

2. The long-wave infrared light absorber according to claim 1, characterized in that, The metasurface layer is grating type, with a period on a subwavelength scale and an operating wavelength in the long-wave infrared band, ranging from 8 μm to 14 μm.

3. The long-wave infrared light absorber according to claim 1 or 2, characterized in that, The dual dielectric layer includes a first dielectric layer and a second dielectric layer; the first dielectric layer adjacent to the reflective layer is made of silicon or germanium; and the second dielectric layer adjacent to the metasurface layer is made of silicon nitride.

4. The long-wave infrared light absorber according to claim 1, characterized in that, The reflective layer material is gold, silver, or aluminum.

5. A method for controlling the long-wave infrared light absorption of a long-wave infrared light absorber based on any one of claims 1 to 4, characterized in that, Specifically: When it is necessary to enhance the absorption of long-wave infrared light, the metasurface layer can be made crystalline by annealing or laser direct writing, so that the metasurface layer exhibits metallic properties. When the polarization state of the light wave is not parallel to that of the metasurface layer, the light wave enters the double dielectric layer through diffraction and undergoes multiple reflections in the reflective layer and the metasurface layer, resulting in FP cavity resonance. At the same time, the frequency of the light wave is matched with the collective oscillation frequency of free electrons in the metasurface layer and the reflective layer, resulting in plasma resonance. Among these, FP cavity resonance and plasma resonance lead to the localization and enhancement of the electromagnetic field in the double dielectric layer, thereby enhancing the absorption of the light wave. When it is necessary to reduce the absorption of long-wave infrared light, the metasurface layer is made amorphous by annealing or laser direct writing, which prevents plasma resonance. The metasurface layer is used to partially transmit light waves, reducing the resonance intensity of the FP cavity, thereby reducing the absorption of long-wave infrared light.

6. The long-wave infrared light absorption modulation method according to claim 5, characterized in that, The reflection or transmission of light wavelength, the position of the resonance peak, the position of the FP cavity resonance peak, and the absorption bandwidth of light waves can be adjusted by adjusting the period and linewidth of the metasurface layer. When the period of the grating is matched with the wavelength of the light wave, Bragg diffraction occurs. The smaller the period of the metasurface layer, the shorter the corresponding Bragg diffraction wavelength. The smaller the period of the grating, the higher the frequency of plasma resonance and FP cavity resonance is supported, which in turn affects the position of the plasma resonance peak and FP cavity resonance peak. When the duty cycle of the grating is smaller, the absorption bandwidth of the light wave is larger and the height of the absorption peak is lower. The duty cycle is the ratio of the linewidth of the grating to its period.

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