Infrared flexible absorber based on simple circle structure

Abstract

The invention discloses an infrared flexible absorber based on a simple circle structure, which relates to the technical field of optical devices and comprises a metal layer, a high-loss dielectric layer, a low-loss dielectric layer and a high-loss surface pattern array layer which are integrated on a substrate and are sequentially arranged from bottom to top, the high-loss surface pattern array layer comprises a plurality of circular unit bodies which are uniformly arranged in an array; at least two circular unit bodies are uniformly distributed in the first direction, at least two circular unit bodies are uniformly distributed in the second direction, and the first direction is perpendicular to the second direction; and the distances between the circular unit bodies and the surrounding circular unit bodies are the same. The structure is simple, integration is easy, processing is easy, cost is low, and the optical property of wide-angle absorption is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of optical devices, and in particular to an infrared flexible absorber based on a simple circular structure. Background Art

[0002] Ultra-broadband optical absorbers operating in the visible-infrared band have a wide range of applications. Depending on the specific bands of light they absorb, optical absorbers can be used in many fields, such as communications, sensing, military, environmental monitoring, medical treatment, and basic research.

[0003] However, most traditional optical broadband absorbers adopt the design strategy of composite surface structure. The high cost and complicated process route brought by the complex surface structure limit its application prospects in infrared detection, photovoltaic materials, and elimination of stray light. For example, large optical systems such as lithography machines are playing a vital role and position in the current environment. Reducing the spot size is one of the important strategies to improve the accuracy of lithography. Among them, the ability to eliminate stray light in the optical system greatly affects the accuracy of the system. The traditional way to eliminate stray light is to fill the optical cavity with light-absorbing coatings. Its complicated maintenance process and high maintenance cost limit the development of optical systems.

[0004] Therefore, it is necessary to provide an infrared flexible absorber which has a simple structure, is easy to integrate and can absorb at a wide angle. Summary of the invention

[0005] The purpose of the present invention is to provide an infrared flexible absorber based on a simple circular structure to solve the problems existing in the above-mentioned prior art. The absorber has a simple structure, is easy to integrate, easy to process, has low cost, and has the optical property of being able to absorb at a wide angle.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides an infrared flexible absorber based on a simple circular structure, comprising a metal layer, a high-loss dielectric layer, a low-loss dielectric layer and a high-loss surface pattern array layer which are integrated on a substrate and arranged in sequence from bottom to top; the high-loss surface pattern array layer comprises a plurality of circular unit bodies arranged in a uniform array; at least two of the circular unit bodies are uniformly distributed in a first direction, and at least two of the circular unit bodies are uniformly distributed in a second direction, the first direction being perpendicular to the second direction; each of the circular unit bodies has the same spacing with the surrounding circular unit bodies.

[0008] Preferably, the diameter of the circular unit body is 0.5 μm to 2 μm; and the distance between the centers of two adjacent circular unit bodies is 1 μm to 5 μm.

[0009] Preferably, the thickness of the metal layer is not less than 100 nm; the thickness of the high-loss dielectric layer is 100 nm to 600 nm; the thickness of the low-loss dielectric layer is 200 nm to 700 nm; and the thickness of the high-loss surface pattern array layer is 30 nm to 100 nm.

[0010] Preferably, the substrate is made of polyimide, glass, quartz or silicon wafer.

[0011] Preferably, the metal layer is formed by introducing argon gas into a high vacuum chamber, applying a direct current power supply to generate a magnetic field and bombarding a high-loss target with generated argon ions to cause sputtering.

[0012] Preferably, the high-loss dielectric layer and the low-loss dielectric layer are formed in sequence by sputtering by applying radio frequency power in an argon environment.

[0013] Preferably, on the basis of the low-loss dielectric layer, an ultraviolet positive resist is spread and dried, and the ultraviolet positive resist is laser-written by an MLA maskless photolithography machine according to the drawing to produce a surface graphic template, and after developing with a corresponding developer, a metal film is deposited by magnetron sputtering, and then the resist is removed by a lift-off process.

[0014] Compared with the prior art, the present invention has achieved the following technical effects:

[0015] The infrared flexible absorber based on a simple circular structure provided by the present invention has an electromagnetic environment constructed by a metal layer and upper and lower dielectric layers, and an auxiliary surface graphic layer. When light enters the absorber, it is refracted and reflected multiple times. With the cooperation of each layer, even obliquely incident light has a chance to be fully absorbed, thereby enhancing wide-angle absorption efficiency. The infrared flexible absorber has a good absorption effect on multi-polarization medium-wave infrared light incident at a wide angle, and is polarization-insensitive to the incident infrared light. Its simple surface structure allows it to be integrated on a flexible device. It has the advantages of simple preparation process, low cost, high repeatability, large-scale production, and low maintenance cost.

[0016] Furthermore, the circular unit body with a diameter between 0.5μm and 2μm can accurately control the local surface plasma resonance frequency. In the infrared band, this size range is well adapted to the wavelength of infrared light, which can promote the collective oscillation of free electrons around the circular metal structure, thereby producing a strong resonant absorption phenomenon. The smaller diameter is conducive to exciting high-frequency resonance and capturing short-wavelength infrared light; the larger diameter corresponds to low-frequency resonance, which is adapted to long-wavelength infrared light, allowing the absorber to have a wider absorption spectrum in the infrared band; the distance between the centers of adjacent circular unit bodies is set at 1μm to 5μm, which ensures effective coupling between units. The appropriate spacing avoids the weak electromagnetic interaction between units due to excessive spacing, and also prevents negative effects such as strong scattering caused by too small spacing. When light is incident, adjacent units use electromagnetic coupling to synergistically change the local electromagnetic field distribution, strengthen the capture and absorption of incident light, and improve the overall absorption efficiency. The absorption capacity is significantly enhanced compared to isolated circular units.

[0017] Furthermore, the thickness of the metal layer is not less than 100nm, which can ensure that it has good electrical conductivity and electromagnetic properties. At this thickness, the concentration of free electrons in the metal is sufficient to induce a significant surface plasma resonance effect, which is critical for the absorption of infrared light. The thicker metal layer can efficiently capture the electromagnetic energy of the incident infrared light, drive electron oscillations, and convert light energy into other forms of energy, avoiding excessive reflection of light on the metal surface and escaping, creating conditions for the coordinated absorption of subsequent layers, and consolidating the absorption foundation of the absorber. At the same time, the thickness of 100nm and above is easier to accurately control in common preparation processes such as physical vapor deposition, ensuring uniform quality of the metal layer and reducing the accumulation of process errors caused by too thin thickness; the thickness is between 100nm and 600nm, and this range allows it to properly regulate light transmission and absorption. At the thinner end, that is, around 100nm, it can quickly respond to changes in the infrared light field and rely on its own larger absorption coefficient to convert part of the light energy into heat energy loss; at the thicker 600nm, it provides enough propagation distance for light to fully absorb the molecules and atoms inside the medium. The thickness of the dielectric layer can effectively buffer the reflection caused by the difference in refractive index between the metal layer and the high-loss dielectric layer, smooth the "gradient" of light transmission, reduce the interface reflection loss, and allow infrared light to shuttle between the layers more smoothly, prolong the retention time of light in the absorber, and indirectly assist light absorption; when it is thinner at 200nm, it also maintains the basic transition function to avoid excessive increase in the overall thickness and cost of the absorber; the thickness of 30nm to 100nm can highlight the absorption enhancement effect of the surface pattern without compromising flexibility due to excessive thickness. Within this thickness range, the pattern array composed of circular units can efficiently excite local surface plasma resonance and enhance the absorption of infrared light; at the same time, the relatively thin thickness ensures that the absorber can maintain the flexibility of the entire absorber in flexible application scenarios such as bending and folding, and ensure the absorption efficiency of infrared light under different deformation states. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the overall structure of the infrared flexible absorber based on a simple circular structure provided by the present invention;

[0020] Figure 2 Absorption, reflection and transmission spectra of the infrared flexible absorber based on a simple circular structure provided by the present invention;

[0021] Figure 3 The electron microscope scanning image and the physical image of the infrared flexible absorber based on the simple circular structure provided by the present invention integrated on the polyimide substrate;

[0022] Figure 4 The infrared flexible absorber based on the simple circular structure provided by the present invention is integrated on polyimide and then tested under a Fourier infrared spectrometer;

[0023] Figure 5 The infrared flexible absorber based on the simple circular structure provided by the present invention is incident at different polarization angles and the absorption spectra of light sources with different polarization states incident at oblique incident angles ranging from 0 to 60 degrees.

[0024] In the figure: 1-metal layer; 2-high loss dielectric layer; 3-low loss dielectric layer; 4-high loss surface pattern array layer. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The purpose of the present invention is to provide an infrared flexible absorber based on a simple circular structure to solve the problems existing in the prior art. The absorber has a simple structure, is easy to integrate, easy to process, has low cost, and has the optical property of being able to absorb at a wide angle.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Embodiment 1

[0029] This embodiment provides an infrared flexible absorber based on a simple circular structure, such as Figure 1 to Figure 5 As shown, it includes a metal layer 1, a high-loss dielectric layer 2, a low-loss dielectric layer 3 and a high-loss surface pattern array layer 4 which are used for integration on a substrate and are arranged in sequence from bottom to top; the high-loss surface pattern array layer 4 includes a plurality of circular unit bodies arranged in a uniform array; at least two circular unit bodies are uniformly distributed in a first direction, and at least two circular unit bodies are uniformly distributed in a second direction, and the first direction is perpendicular to the second direction; each circular unit body has the same spacing with the surrounding circular unit bodies.

[0030] Through the electromagnetic environment constructed by the metal layer 1 and the upper and lower dielectric layers, and the auxiliary surface graphic layer, light enters the absorber and undergoes multiple refractions and reflections. With the cooperation of each layer, even obliquely incident light has the opportunity to be fully absorbed, thereby enhancing the wide-angle absorption efficiency. It has a good absorption effect on multi-polarization medium-wave infrared light incident at a wide angle, and is polarization-insensitive to the incident infrared light. Its simple surface structure allows it to be integrated on flexible devices. It has the advantages of simple preparation process, low cost, high repeatability, large-scale production, and low maintenance cost.

[0031] Among them, the relevant settings for metal layer 1 are as follows:

[0032] In the optional scheme of this embodiment, it is more preferred that the metal layer 1 is formed by introducing argon gas into a high vacuum chamber, applying a direct current power supply to generate a magnetic field and bombarding a high-loss target with generated argon ions to cause sputtering.

[0033] Specifically, the metal may be tungsten, titanium, gold, silver, or the like;

[0034] The relevant setting descriptions of the high-loss dielectric layer 2 and the low-loss dielectric layer 3 are as follows:

[0035] In the optional scheme of this embodiment, it is more preferred to apply radio frequency power to sputter in an argon environment to sequentially form the high-loss dielectric layer 2 and the low-loss dielectric layer 3 .

[0036] Specifically, the high-loss dielectric layer 2 may be made of materials such as silicon nitride and iron oxide, and the low-loss dielectric layer 3 may be made of materials such as silicon, germanium, and aluminum oxide.

[0037] Among them, the relevant setting description of the high-loss surface pattern array layer 4 is as follows:

[0038] In the optional scheme of this embodiment, it is more preferred that on the basis of the low-loss dielectric layer 3, the ultraviolet positive resist is evenly coated and dried, and the surface graphic template is produced by laser direct writing of the ultraviolet positive resist according to the drawing using an MLA maskless photolithography machine, and after developing with a corresponding developer, a layer of metal film is deposited by magnetron sputtering, and then the resist is removed by a lift-off process.

[0039] In the optional scheme of this embodiment, it is more preferred that the diameter of the circular unit body is 0.5μm to 2μm; and the distance between the centers of two adjacent circular unit bodies is 1μm to 5μm. The circular unit body with a diameter between 0.5μm and 2μm can accurately control the local surface plasma resonance frequency. In the infrared band, this size range is well adapted to the wavelength of infrared light, which can promote free electrons to collectively oscillate around the circular metal structure, thereby generating a strong resonance absorption phenomenon. The smaller diameter is conducive to exciting high-frequency resonance and capturing short-wavelength infrared light; the larger diameter corresponds to low-frequency resonance, which is adapted to long-wavelength infrared light, so that the absorber has a wider absorption spectrum in the infrared band; the distance between the centers of adjacent circular unit bodies is set at 1μm to 5μm, which ensures effective coupling between units. The appropriate spacing avoids the weak electromagnetic interaction between units caused by too large spacing, and also prevents the negative effects such as strong scattering caused by too small spacing. When light is incident, the adjacent units change the local electromagnetic field distribution through electromagnetic coupling, strengthen the capture and absorption of incident light, and improve the overall absorption efficiency. The absorption capacity is significantly enhanced compared with the isolated circular unit.

[0040] Among them, about other related settings description:

[0041] In the optional scheme of this embodiment, it is more preferred that the thickness of the metal layer 1 is not less than 100nm; the thickness of the high-loss dielectric layer 2 is 100nm~600nm; the thickness of the low-loss dielectric layer 3 is 200nm~700nm; the thickness of the high-loss surface pattern array layer 4 is 30nm~100nm.

[0042] The thickness of the metal layer 1 is not less than 100nm, which can ensure that it has good electrical conductivity and electromagnetic properties. At this thickness, the free electron concentration in the metal is sufficient to induce a significant surface plasma resonance effect, which is very critical for the absorption of infrared light. The thicker metal layer 1 can efficiently capture the electromagnetic energy of the incident infrared light, drive electron oscillations, and convert light energy into other forms of energy, avoiding excessive reflection of light on the metal surface and escaping, creating conditions for the coordinated absorption of subsequent layers, and consolidating the absorption foundation of the absorber. At the same time, the thickness of 100nm and above is easier to accurately control in common preparation processes such as physical vapor deposition, ensuring the uniform quality of the metal layer 1 and reducing the accumulation of process errors caused by too thin thickness; the thickness is between 100nm and 600nm, and this range enables it to properly regulate light transmission and absorption. At the thinner end, that is, at about 100nm, it can quickly respond to changes in the infrared light field and rely on its own larger absorption coefficient to convert part of the light energy into heat energy loss; at the thicker 600nm, it provides enough propagation distance for light to fully interact with the molecules and atoms inside the medium. The absorption characteristics of the medium are used to capture more light energy, adapt to the absorption needs of infrared light of different frequencies, and improve the overall absorption bandwidth; the thickness range of 200nm to 700nm allows the low-loss dielectric layer 3 to play an excellent role in transition and optimization of the optical path. The thicker low-loss layer can effectively buffer the reflection caused by the difference in refractive index between the metal layer 1 and the high-loss dielectric layer 2, smooth the light transmission "gradient", reduce interface reflection loss, and allow infrared light to shuttle more smoothly between the layers, prolonging the retention time of light in the absorber, indirectly assisting light absorption; the thinner 200nm to 700nm thickness range allows the low-loss dielectric layer 3 to play an excellent role in transition and optimization of the optical path. The thicker low-loss layer can effectively buffer the reflection caused by the difference in refractive index between the metal layer 1 and the high-loss dielectric layer 2, smooth the light transmission "gradient", reduce interface reflection loss, and allow infrared light to shuttle more smoothly between the layers, prolonging the retention time of light in the absorber, and indirectly assisting light absorption; the thinner 200nm to 700nm thickness range allows the low-loss dielectric layer 3 to play an excellent role in transition and optimization of the optical path, and the thicker low-loss layer can effectively buffer the reflection caused by the difference in refractive index between the metal layer 1 and the high-loss dielectric layer 2, smoothing the light transmission "gradient", reducing interface reflection loss, and indirectly assisting light absorption. When the thickness is less than 30nm, the basic transition function is maintained to avoid excessively increasing the overall thickness and cost of the absorber; the thickness of 30nm to 100nm can not only highlight the absorption enhancement effect of the surface pattern, but also will not cause flexibility to be damaged due to excessive thickness. Within this thickness range, the graphic array composed of circular unit cells can efficiently excite local surface plasma resonance and enhance the absorption of infrared light; at the same time, the relatively thin thickness ensures that the absorber can maintain the flexibility of the entire absorber in flexible application scenarios such as bending and folding, thereby ensuring the absorption efficiency of infrared light under different deformation states.

[0043] In the optional solutions of this embodiment, it is more preferred that the material of the substrate is polyimide, glass, quartz or silicon wafer.

[0044] Specifically, in practical applications, especially in situations such as eliminating stray light in large optical systems such as lithography machines to improve lithography accuracy, the infrared flexible absorber based on a simple circular structure of this embodiment has great application prospects. It has great application prospects in the fields of geological remote sensing, meteorological light measurement, environmental monitoring, and eliminating stray light in optical systems.

[0045] Specific examples:

[0046] See also Figure 1 As shown, it comprises: a metal layer 1, a high-loss dielectric layer 2, a low-loss dielectric layer 3 and a high-loss surface pattern array layer 4;

[0047] ① Metal layer 1: Using magnetron sputtering, argon gas is introduced into a high vacuum chamber, and a DC power supply is applied to generate a magnetic field to bombard the high-loss target with the generated argon ions to sputter to form a uniform and dense 100-nanometer-thick metal high-loss film layer.

[0048] ② High-loss dielectric layer 2 and low-loss dielectric layer 3: Similarly, by using magnetron sputtering, RF power is applied in an argon environment to sequentially form a 300-nanometer-thick high-loss dielectric film layer and a 400-nanometer-thick low-loss dielectric film layer.

[0049] ③ High-loss surface pattern array layer 4: On the basis of the above, ultraviolet positive resist is used for coating and drying, and the thickness of the resist is controlled between 300 nanometers and 2 microns.

[0050] Use the MLA maskless lithography machine to perform laser direct writing on the UV positive resist evenly coated in the previous step according to the drawing to produce a template for the surface pattern.

[0051] After developing with a corresponding developer, a metal film with a thickness of 30 nanometers is deposited again by magnetron sputtering.

[0052] Finally, the lift-off process is used to remove the adhesive, thereby obtaining a high-loss surface pattern array layer 4 with a perfect circular structure and a thickness of 30 nanometers.

[0053] The absorption, reflection and transmission spectra of the infrared flexible absorber based on a simple circular structure in this embodiment are as follows: Figure 2 As shown, the average absorption rate in the infrared band from 2.1 microns to 6.8 microns can reach 95.7%, and the highest absorption peaks appear at 2.7 microns and 6.0 microns, with absorption rates of 97.8% and 98.4% respectively.

[0054] The electron microscope scanning image and the actual image of the infrared flexible absorber based on a simple circular structure integrated on a polyimide substrate of this embodiment are shown in the figure. Figure 3 shown.

[0055] The infrared flexible absorber based on a simple circular structure of this embodiment is integrated on a polyimide substrate and then tested by a Fourier infrared spectrometer. Figure 4 As shown, the average absorption rate in the mid-wave infrared atmospheric window band from 3 microns to 5 microns can reach 97.1%.

[0056] The absorption spectra of the infrared flexible absorber based on a simple circular structure of this embodiment at different polarization angles and different polarization state light sources at oblique incident angles ranging from 0 to 60 degrees are shown in FIG. Figure 5 As shown, mid-infrared light incident at different polarization angles has no effect on the absorptivity of the device. When the incident angle of infrared light in different polarization states changes from 0 to 60, the absorptivity of the absorber can still be maintained above 70%, so as to fully play its role in complex stray light elimination scenarios.

[0057] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An infrared flexible absorber based on a simple circular structure, characterized in that: It includes a metal layer, a high-loss dielectric layer, a low-loss dielectric layer and a high-loss surface pattern array layer which are used for integration on a substrate and are arranged in sequence from bottom to top; The high-loss surface graphic array layer includes a plurality of circular unit bodies arranged in a uniform array; at least two of the circular unit bodies are uniformly distributed in a first direction, and at least two of the circular unit bodies are uniformly distributed in a second direction, and the first direction is perpendicular to the second direction; each of the circular unit bodies has the same spacing with the surrounding circular unit bodies.

2. The infrared flexible absorber based on a simple circular structure according to claim 1, characterized in that: The diameter of the circular unit body is 0.5 μm to 2 μm; and the distance between the centers of two adjacent circular unit bodies is 1 μm to 5 μm.

3. The infrared flexible absorber based on a simple circular structure according to claim 1, characterized in that: The thickness of the metal layer is not less than 100 nm; The thickness of the high-loss dielectric layer is 100nm to 600nm; The thickness of the low-loss dielectric layer is 200nm to 700nm; The thickness of the high-loss surface pattern array layer is 30nm-100nm.

4. The infrared flexible absorber based on a simple circular structure according to claim 1, characterized in that: The substrate is made of polyimide, glass, quartz or silicon wafer.

5. The infrared flexible absorber based on a simple circular structure according to claim 1, characterized in that: The metal layer is formed by introducing argon gas into a high vacuum chamber, applying a direct current power supply to generate a magnetic field and bombarding a high-loss target with generated argon ions to cause sputtering.

6. The infrared flexible absorber based on a simple circular structure according to claim 1, characterized in that: The high-loss dielectric layer and the low-loss dielectric layer are sequentially formed by sputtering with radio frequency power applied in an argon environment.

7. The infrared flexible absorber based on a simple circular structure according to claim 6, characterized in that: On the basis of the low-loss dielectric layer, an ultraviolet positive resist is spread and dried, and the ultraviolet positive resist is laser-written by an MLA maskless photolithography machine according to the drawing to produce a surface graphic template, and after developing with a corresponding developer, a metal film is deposited by magnetron sputtering, and then the resist is removed by a lift-off process.

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