A visible to mid-infrared ultra-broadband absorber and a preparation method thereof

Abstract

The present application relates to the field of optical technology, more particularly to a visible to mid-infrared super-wideband absorber and a preparation method thereof, the method comprising the following steps: self-assembling polystyrene microspheres on a polyimide substrate to form a monolayer hexagonal close-packed structure substrate, and then forming a nano-cone array substrate through ion etching; placing a copper substrate into a coating chamber and introducing argon, and sputtering to obtain a reflection layer; placing a zirconium substrate into the coating chamber and introducing argon and oxygen, and sputtering to obtain a first metal absorption film layer; continuously introducing argon and oxygen, and sputtering to obtain a second metal absorption film layer; continuously introducing argon and oxygen, and sputtering to obtain a third metal absorption film layer; placing an aluminum oxide substrate into the coating chamber, and then introducing argon, and sputtering to obtain a dielectric antireflection layer, thereby forming the absorber. The present application can have extremely high absorption in the visible light and near-infrared regions, and has good angle tolerance, polarization insensitivity, bending resistance and heat resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, more particularly, to a visible to mid-infrared ultra-wideband absorber and a preparation method thereof. BACKGROUND

[0002] The metamaterial absorber with high-efficiency absorption performance in the visible light and infrared waveband is increasingly concerned by people, which has wide applications in solar energy collection system, heat emitter, infrared imaging, sensor and photoelectric detector, etc. The absorption rate of the absorber is a key parameter, and how to design the structure and improve the absorption rate of the absorber in the required waveband is the focus of the research. The traditional absorption film is divided into four categories according to different absorption principles, which are multilayer optical interference film, metal ceramic film, multilayer gradient film and semiconductor-metal string film, and all of them have high absorption rate in the vertical direction, and the preparation method is relatively simple and easy to industrialize, but there are some problems: such as narrow absorption waveband, poor preparation process repeatability, poor weather resistance, and the absorption waveband of some absorbers depends on the used materials, which is difficult to improve the performance.

[0003] In recent years, with the emergence of new preparation technologies, some micro-nano structure films are produced for realizing the spectral selection absorption in a wide waveband, but the preparation method thereof is mostly dependent on electron beam exposure, focused ion beam processing and other technologies, which has the difficulties of high cost and long time-consuming, making it difficult to be popularized to industrial production, and the existing structures are very sensitive to the tilt angle of incident light, and the conditions for the incident light are relatively harsh, and the applicability is low. SUMMARY

[0004] The present application aims at overcoming the deficiencies of the prior art, and provides a visible to mid-infrared ultra-wideband absorber and a preparation method thereof, which can have extremely high absorption rate in the visible light and near-infrared region, and has good angle tolerance and polarization insensitivity, and also has good bending resistance and heat resistance, and is easy to realize industrial production.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is:

[0006] A preparation method of a visible to mid-infrared ultra-wideband absorber is provided, which comprises the following steps:

[0007] S1. ultrasonic cleaning a polyimide substrate in an ethanol solution;

[0008] S2. self-assembling polystyrene microspheres on the cleaned polyimide substrate to form a single-layer hexagonal close-packed structure substrate, and then forming a nano-cone array substrate on the single-layer hexagonal close-packed structure substrate by ion etching;

[0009] S3. Put copper substrate into the coating chamber, then introduce argon into the coating chamber, and sputter copper target to prepare the reflection layer;

[0010] S4. Put zirconium substrate into the coating chamber, then introduce argon and oxygen into the coating chamber, and sputter zirconium target to prepare the first metal absorption film layer;

[0011] S5. Continue to introduce argon and oxygen into the coating chamber, and sputter zirconium target to prepare the second metal absorption film layer; the sputtering power in step S5 is less than that in step S4; the sputtering time in step S5 is greater than that in step S4;

[0012] S6. Continue to introduce argon and oxygen into the coating chamber, and sputter zirconium target to prepare the third metal absorption film layer; the sputtering power in step S6 is less than that in step S5; the sputtering time in step S6 is less than that in step S4;

[0013] S7. Put aluminum oxide substrate into the coating chamber, then introduce argon into the coating chamber, and sputter aluminum oxide target to prepare the medium antireflection layer, thereby forming the visible to mid-infrared super-wideband absorber.

[0014] Further, the step S2 specifically comprises the following steps:

[0015] S21. Mix equal volumes of polystyrene microsphere aqueous solution and equal volumes of ethanol solution, then drop onto the surface of deionized water of sodium dodecyl sulfate solution to form a monolayer hexagonal close-packed structure;

[0016] S22. Transfer the monolayer hexagonal close-packed structure to the cleaned polyimide substrate, and obtain the monolayer hexagonal close-packed structure substrate after drying;

[0017] S23. Put the monolayer hexagonal close-packed structure substrate into the ion etching machine, then introduce oxygen into the ion etching machine and etch to obtain the nano-cone array substrate.

[0018] Further, the metal volume fraction and thickness of the first metal absorption film layer are both greater than those of the second metal absorption film layer, and the metal volume fraction and thickness of the second metal absorption film layer are both greater than those of the third metal absorption film layer.

[0019] Further, it further comprises step S8: detecting the polarization insensitivity, bending resistance and heat resistance of the visible to mid-infrared super-wideband absorber; the step S8 comprises the following steps:

[0020] S81. Polarization insensitivity detection: TM polarized light is vertically incident on the visible to mid-infrared super wideband absorber, and the normalized absorbance is calculated; and TM polarized light is obliquely incident on the visible to mid-infrared super wideband absorber, and the absorption spectrum is measured;

[0021] S82. Bending resistance detection: the visible to mid-infrared super wideband absorber is bent multiple times, and then the absorption spectrum is measured;

[0022] S83. Heat resistance detection: the visible to mid-infrared super wideband absorber is heat annealed, and then the absorption spectrum is measured.

[0023] The application also provides a visible to mid-infrared super wideband absorber, characterized by comprising, from bottom to top, a nano-cone array substrate, a reflection layer, a first metal absorption film layer, a second metal absorption film layer, a third metal absorption film layer, and a dielectric antireflection layer, wherein the metal volume fraction of the first metal absorption film layer is greater than that of the second metal absorption film layer, and the metal volume fraction of the second metal absorption film layer is greater than that of the third metal absorption film layer.

[0024] Preferably, the first metal absorption film layer is a first metal ceramic film layer, the second metal absorption film layer is a second metal ceramic film layer, and the third metal absorption film layer is a third metal ceramic film layer.

[0025] Preferably, the first metal ceramic film layer, the second metal ceramic film layer, and the third metal ceramic film layer are Zr-ZrO2 metal ceramic films.

[0026] Preferably, the thickness of the first metal absorption film layer is greater than that of the second metal absorption film layer, and the thickness of the second metal absorption film layer is greater than that of the third metal absorption film layer; wherein the thickness of the first metal absorption film layer is 90-110 nm, the thickness of the second metal absorption film layer is 50-60 nm, and the thickness of the third metal absorption film layer is 36-44 nm.

[0027] Preferably, the nano-cone array substrate is a polyimide nano-cone array substrate, and the period, height, and bottom diameter of the polyimide nano-cone array substrate are 500-1500 nm, 600-1200 nm, and 600-1000 nm, respectively.

[0028] Preferably, the reflection layer is a metal reflection layer, and the thickness of the metal reflection layer is greater than or equal to 100 nm; the dielectric antireflection layer is an aluminum oxide dielectric antireflection layer, and the thickness of the aluminum oxide dielectric antireflection layer is 63-77 nm.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] The application provides a visible-to-middle infrared super wideband absorber and a preparation method thereof. The visible-to-middle infrared super wideband absorber comprises, from bottom to top, a nano-cone array substrate, a reflection layer, a first metal absorption film layer, a second metal absorption film layer, a third metal absorption film layer and a dielectric antireflection layer, so that the visible-to-middle infrared super wideband absorber has a very high absorption rate in the visible light and near infrared region, and has good angle tolerance and polarization insensitivity, and also has good bending resistance and heat resistance. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A flow chart of the preparation method of the visible-to-middle infrared super wideband absorber of the application;

[0032] Figure 2 A normalized absorbance curve schematic diagram of the preparation method of the application by simulation calculation when performing the vertical incidence of step S81;

[0033] Figure 3 A normalized absorption spectrum curve schematic diagram of the preparation method of the application by simulation calculation when performing the vertical incidence of step S81;

[0034] Figure 4 A normalized absorption spectrum curve schematic diagram of the preparation method of the application by simulation calculation when performing the oblique incidence of step S82;

[0035] Figure 5 A comparison schematic diagram of the absorption spectrum of the preparation method of the application by experimental measurement and simulation calculation when performing the vertical incidence of step S81;

[0036] Figure 6 An experimental measurement absorption spectrum curve schematic diagram of the preparation method of the application when performing the oblique incidence of step S81;

[0037] Figure 7 A comparison schematic diagram of the absorption spectrum of the preparation method of the application before and after performing step S82;

[0038] Figure 8 A comparison schematic diagram of the absorption spectrum of the preparation method of the application before and after performing step S83;

[0039] Figure 9 A structure schematic diagram of the visible-to-middle infrared super wideband absorber of the application;

[0040] Figure 10 A size schematic diagram of the visible-to-middle infrared super wideband absorber of the application;

[0041] Figure 11 A comparison schematic diagram of the absorption spectrum of the visible-to-middle infrared super wideband absorber of the application under different cone bottom diameters L;

[0042] Figure 12 Figure 1 is a schematic diagram of the absorption spectrum of a visible to mid-infrared super-wideband absorber according to the present application at different conical heights h1.

[0043] The illustration labels are explained as follows:

[0044] 1 - nanocone array substrate, 2 - reflective layer, 3 - first metal absorption film layer, 4 - second metal absorption film layer, 5 - third metal absorption film layer, 6 - dielectric antireflection layer. DETAILED DESCRIPTION

[0045] The present application will be further described below in conjunction with specific embodiments. The accompanying drawings are merely illustrative and represent only schematic views, and should not be understood as limiting the present patent; in order to better illustrate the embodiments of the present application, some components in the drawings can be omitted, enlarged or reduced, and do not represent the actual size of the product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings can be omitted.

[0046] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "left", "right" and the like is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the position relationship in the drawings are only used for illustrative purposes, and should not be understood as limiting the present patent, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0047] Embodiment 1

[0048] As Figures 1 to 8 shown is a first embodiment of a preparation method of a visible to mid-infrared super-wideband absorber according to the present application, comprising the following steps:

[0049] S1. ultrasonic cleaning of the polyimide substrate in ethanol solution; in this embodiment, the polyimide substrate is cleaned in ethanol solution for 15-25 min to enhance its hydrophilicity.

[0050] S2. self-assembling polystyrene microspheres on the cleaned polyimide substrate to form a single-layer hexagonal close-packed structure substrate, and then forming a nanocone array substrate 1 on the single-layer hexagonal close-packed structure substrate by ion etching; the step S2 in this embodiment specifically comprises the following steps:

[0051] S21. Take equal volumes of polystyrene microsphere aqueous solution and ethanol solution, and then drop them on the surface of a sodium dodecyl sulfate (SDS) solution in deionized water, and the microspheres form a monolayer hexagonal close-packed structure at the interface between air and solution through self-assembly; specifically, the sodium dodecyl sulfate solution is a sodium dodecyl sulfate solution with a solid content of 2.5% w / v;

[0052] S22. The monolayer hexagonal close-packed structure is transferred to a cleaned polyimide substrate, and after drying, a monolayer hexagonal close-packed structure substrate is obtained; specifically, drying can be performed by natural air drying, low-temperature drying, or the like;

[0053] S23. The monolayer hexagonal close-packed structure substrate is placed in an ion etching machine, and 20 SCCM of oxygen is introduced into the ion etching machine for etching, to obtain a nanocone array substrate 1; it should be noted that during the entire etching process, the etching is performed under the condition of maintaining a working pressure of 2 Pa for 1500 s, to obtain a nanocone array substrate 1 with a period of 500≤P≤1500 nm, a height of 600≤h1≤1200 nm, and a bottom diameter of 600≤L≤1000 nm; as a preferred embodiment, P=1000 nm, L=800 nm, and h1=1000 nm.

[0054] S3. A copper substrate is placed in a coating chamber, and then 100 SCCM of argon is introduced into the coating chamber, and a copper target is sputtered to prepare a reflective layer 2; specifically, during the sputtering process of step S3, the sputtering power is DC 150 W, the time is 100 s, and a copper metal reflective layer with a thickness h2≥100 nm is prepared; as a preferred embodiment, a copper metal reflective layer with a thickness h2=100 nm is prepared.

[0055] S4. A zirconium substrate is placed in a coating chamber, and then 100 SCCM of argon and 9 SCCM of oxygen are simultaneously introduced into the coating chamber, and a zirconium target is sputtered to prepare a first metal absorption film layer 3; specifically, during the sputtering process of step S4, the sputtering power is RF 610 W, the time is 107 s, and a Zr-ZrO2 cermet film with a high metal volume fraction (HMVF) and a thickness of 90≤h3≤110 nm is prepared; as a preferred embodiment, a Zr-ZrO2 cermet film with a high metal volume fraction (HMVF) and a thickness h3=100 nm is prepared.

[0056] S5. Continue to introduce 100 SCCM of argon and 10 SCCM of oxygen into the coating chamber, and sputter the zirconium target to prepare a second metal absorption film layer 4; specifically, during the sputtering process of step S5, the sputtering power is RF 600 W, the time is 170 s, and a Zr-ZrO2 cermet film with a medium metal volume fraction (MMVF) and a thickness of 50≤h4≤60 nm is prepared; as a preferred embodiment, a Zr-ZrO2 cermet film with a medium metal volume fraction (MMVF) and a thickness h4=55 nm is prepared.

[0057] S6. Again, the film chamber is connected with 100 SCCM of argon and 10 SCCM of oxygen, and a zirconium target is sputtered to prepare a third metal absorption film layer 5; specifically, during the sputtering process of step S6, the sputtering power is RF 575 W, the time is 85 s, the thickness of the prepared third metal absorption film layer 5 is 36≤h5≤44 nm, and preferably, the thickness h5=40 nm, so that a Zr-ZrO2 cermet film with low metal volume fraction (LMVF) is obtained;

[0058] S7. An alumina (Al2O3) substrate is placed in the film chamber, and then the film chamber is connected with 100 SCCM of argon, and an alumina (Al2O3) target is sputtered to prepare a medium antireflection layer 6, thereby forming a visible to mid-infrared super-wideband absorber; specifically, during the sputtering process of step S7, the sputtering power is RF 400 W, the time is 800 s, the thickness of the prepared medium antireflection layer 6 is 63≤h6≤77 nm, and preferably, the thickness h6=70 nm, so that an Al2O3 medium antireflection layer is obtained.

[0059] It should be noted that steps S3 to S7 are completed by using a full-automatic magnetron sputtering film coating machine, and during the sputtering process of steps S3 to S7, the base vacuum air pressure is controlled at 5×10 -4 Pa, and the air pressure is maintained at 0.5 Pa.

[0060] The visible to mid-infrared super-wideband absorber prepared by the preparation method of the embodiment comprises, from bottom to top, a nano-cone array substrate 1, a reflection layer 2, a first metal absorption film layer 3, a second metal absorption film layer 4, a third metal absorption film layer 5, and a medium antireflection layer 6, and the metal volume fraction and thickness of the first metal absorption film layer 3 are both greater than those of the second metal absorption film layer 4, and the metal volume fraction and thickness of the second metal absorption film layer 4 are both greater than those of the third metal absorption film layer 5; this arrangement makes the absorber have extremely high absorption in the visible and near-infrared regions, and have good angle tolerance and polarization insensitivity, and at the same time, the use of a flexible nano-cone array substrate 1 makes the absorber also have good bending resistance and heat resistance. In addition, the absorber prepared by the preparation method of the embodiment utilizes surface plasmon resonance and light interference effects to improve the absorption of the absorber.

[0061] The absorber prepared by the preparation method of the embodiment satisfies an absorption rate greater than 90% in a wavelength range of 300 nm-3000 nm, and in a preferred scheme, i.e., when P=1000 nm, L=800 nm, h 1＝ 1000 nm, h 2＝ 100 nm, h 3＝ 100 nm, h 4＝ 55 nm, h 5＝40 nm, h 6＝ When L = 70 nm, the absorber satisfies that the absorption rate is greater than 98% in the wavelength range of 300 nm-3000 nm.

[0062] Embodiment 2

[0063] This embodiment is similar to Embodiment 1, except that this embodiment further includes step S8: detecting the polarization insensitivity, bending resistance and heat resistance of the visible-to-mid-infrared ultra-wideband absorber; in this embodiment, P = 1000 nm, L = 800 nm, h 1＝ 1000 nm, h 2＝ 100 nm, h 3＝ 100 nm, h 4＝ 55 nm, h 5＝ 40 nm, h 6＝ 70 nm as a sample; step S8 includes the following steps:

[0064] S81. The polarization insensitivity detection specifically includes the following steps:

[0065] S811. The visible-to-mid-infrared ultra-wideband absorber is vertically incident to TM polarized light, and the normalized absorbance is calculated; in Figure 2 , the three curves correspond to the transmission spectrum, the reflection spectrum and the absorption spectrum respectively; as Figure 3 shown is the normalized absorption spectrum calculated by simulation;

[0066] S812. The visible-to-mid-infrared ultra-wideband absorber is obliquely incident to TM polarized light, and the absorption spectrum is measured; specifically, the light is incident at an incident angle of 0-60° with an interval of 10°, and simulation calculation and experimental measurement are performed, respectively obtaining the absorption spectra as Figure 4 and Figure 6 ; from Figure 4 , it can be seen that when the incident angle is 60°, the average absorption rate of the absorber in the wavelength range of 300-2900 nm is still greater than 90%; as Figure 6 shown is the experimental measurement absorption spectrum, and the experimental result is better than the simulation result, because the surface plasmon resonance effect caused by the metal nanoparticles brought by magnetron sputtering.

[0067] S82. Bending resistance detection: the visible-to-mid-infrared ultra-wideband absorber is bent for multiple times, and then the absorption spectrum is measured; specifically, the absorber sample is bent for at least 100 times, and the absorption spectrum is basically unchanged, as Figure 7 shown;

[0068] S83. Heat resistance detection: heat annealing is performed on the visible to mid-infrared ultra-wideband absorber, and then the absorption spectrum is measured; specifically, the heat annealing experiment at at least 150℃ is performed on the absorber sample, and the absorption spectrum basically does not change within 6h, as shown in Figure 8 .

[0069] It should be noted that in step S8, the spectrophotometer (lambda950) is used to measure the spectrum, and the experimental results show that the absorber maintains a very high absorption rate in the measured waveband. As shown in Figure 5 , the absorption spectrum in the wavelength range of 300-3000nm is measured, the incident light angle is 8°, the absorption rate is calculated, and the comparison between the experimental measurement and the simulation calculation is obtained, and the experimental measurement is basically consistent with the simulation results.

[0070] Embodiment 3

[0071] As shown in Figures 9 to 12 , an embodiment of a visible to mid-infrared ultra-wideband absorber of the present application includes, from bottom to top, a nano-cone array substrate 1, a reflection layer 2, a first metal absorption film layer 3, a second metal absorption film layer 4, a third metal absorption film layer 5, and a dielectric antireflection layer 6. The metal volume fraction of the first metal absorption film layer 3 is greater than that of the second metal absorption film layer 4, and the metal volume fraction of the second metal absorption film layer 4 is greater than that of the third metal absorption film layer 5.

[0072] Among them, the first metal absorption film layer 3 is a first metal ceramic film layer, the second metal absorption film layer 4 is a second metal ceramic film layer, and the third metal absorption film layer 5 is a third metal ceramic film layer. Specifically, the first metal ceramic film layer, the second metal ceramic film layer, and the third metal ceramic film layer are all Zr-ZrO2 metal ceramic film layers. In this embodiment, the multilayer metal ceramic absorption film system has a gradually changing refractive index distribution from the substrate to the air, which can achieve high absorption effect based on impedance matching.

[0073] As shown in Figure 9 and Figure 10 , the nano-cone array substrate 1 is a polyimide nano-cone array substrate, the period of the polyimide nano-cone array substrate is 500≤P≤1500nm, the height is 600≤h1≤1200nm, and the bottom diameter is 600≤L≤1000nm; as preferred, P=1000nm, L=800nm, and h1=1000nm. It should be noted that from Figure 11 , it can be seen that under the condition that other parameters are unchanged, the larger L is, the higher the absorption rate is, but after L is greater than 800nm, the absorption rate changes little, therefore, considering the preparation efficiency, material saving, and cost, 800nm is taken as the preferred value. From Figure 12It can be seen that, when other parameters are unchanged, the greater h1 is, the higher the absorption rate is, but when h1 is greater than 1000 nm, the absorption rate changes little, therefore, 1000 nm is preferred in terms of preparation efficiency, saving material and cost.

[0074] In addition, the reflective layer 2 is a metal reflective layer, the thickness h2 of the metal reflective layer is greater than or equal to 100 nm, and the thickness h2 of the metal reflective layer is preferably 100 nm; in the embodiment, the metal reflective layer is a copper metal reflective layer.

[0075] In addition, the thickness of the first metal absorption film layer 3 is greater than the thickness of the second metal absorption film layer 4, and the thickness of the second metal absorption film layer 4 is greater than the thickness of the third metal absorption film layer 5. The thickness of the first metal absorption film layer 3 is 90≤h3≤110 nm, and the thickness h3 of the first metal absorption film layer 3 is preferably 100 nm; the thickness of the second metal absorption film layer 4 is 50≤h4≤60 nm, and the thickness h4 of the second metal absorption film layer 4 is preferably 55 nm; the thickness of the third metal absorption film layer 5 is 36≤h5≤44 nm, and the thickness h5 of the third metal absorption film layer 5 is preferably 40 nm.

[0076] In addition, the dielectric antireflection layer 6 is an aluminum oxide dielectric antireflection layer, which not only serves as an antireflection film layer, but also plays a role of impedance matching; in the embodiment, the thickness of the aluminum oxide dielectric antireflection layer is 63≤h6≤77 nm, and the thickness h6 of the aluminum oxide dielectric antireflection layer is preferably 70 nm.

[0077] The visible-to-mid-infrared super-wideband absorber of the embodiment can be prepared by the preparation method of the embodiment 1 or 2.

[0078] Obviously, the above embodiments of the present application are merely exemplary and are not intended to limit the embodiments of the present application. Based on the above description, those skilled in the art can make other different forms of changes or modifications. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for preparing a visible to mid-infrared ultra-broadband absorber, characterized by, Comprising the following steps: S1. ultrasonic cleaning of the polyimide substrate in ethanol solution; S2. self-assembly of polystyrene microspheres on the cleaned polyimide substrate to form a monolayer hexagonal close-packed structure substrate, and then ion etching on the monolayer hexagonal close-packed structure substrate to form a nanocone array substrate (1); wherein, comprising the following steps: S21. mixing equal volumes of polystyrene microsphere aqueous solution and equal volumes of ethanol solution, then dropping on the surface of deionized water of sodium dodecyl sulfate solution to form a monolayer hexagonal close-packed structure; S22. transferring the monolayer hexagonal close-packed structure to the cleaned polyimide substrate, and obtaining a monolayer hexagonal close-packed structure substrate after drying; S23. placing the monolayer hexagonal close-packed structure substrate into an ion etching machine, then introducing oxygen into the ion etching machine and etching to obtain the nanocone array substrate (1); S3. placing copper substrate into the coating chamber, then introducing argon into the coating chamber, sputtering copper target to prepare a reflective layer (2); S4. placing zirconium substrate into the coating chamber, then introducing argon and oxygen into the coating chamber simultaneously, sputtering zirconium target to prepare a first metal absorption film layer (3); S5. continuing to introduce argon and oxygen into the coating chamber simultaneously, sputtering zirconium target to prepare a second metal absorption film layer (4); the sputtering power in step S5 is less than that in step S4; the sputtering time in step S5 is greater than that in step S4; S6. introducing argon and oxygen into the coating chamber again, sputtering zirconium target to prepare a third metal absorption film layer (5); the sputtering power in step S6 is less than that in step S5; the sputtering time in step S6 is less than that in step S4; S7. placing aluminum oxide substrate into the coating chamber, then introducing argon into the coating chamber, sputtering aluminum oxide target to prepare a dielectric antireflection layer (6), forming a visible to mid-infrared super-wideband absorber.

2. The method of claim 1, wherein the visible to mid-infrared ultra-broadband absorber is prepared by the steps of: The metal volume fraction and thickness of the first metal absorption film layer (3) are both greater than those of the second metal absorption film layer (4), and the metal volume fraction and thickness of the second metal absorption film layer (4) are both greater than those of the third metal absorption film layer (5).

3. The method of claim 1, wherein the visible to mid-infrared ultra-broadband absorber is prepared by the steps of: Further comprising step S8: detecting the polarization insensitivity, bending resistance and heat resistance of the visible to mid-infrared super-wideband absorber; the step S8 comprises the following steps: S81. polarization insensitivity detection: vertically incident TM polarized light on the visible to mid-infrared super-wideband absorber, and calculate the normalized absorbance; and obliquely incident TM polarized light on the visible to mid-infrared super-wideband absorber, and measure the absorption spectrum; S82. bending resistance detection: bending the visible to mid-infrared super-wideband absorber multiple times, and then measuring the absorption spectrum; S83. heat resistance detection: heat annealing the visible to mid-infrared super-wideband absorber, and then measuring the absorption spectrum.

4. A visible to mid-infrared super-wideband absorber prepared by the method for preparing a visible to mid-infrared super-wideband absorber according to any one of claims 1 to 3, characterized by, The application relates to a nano-taper array substrate, which comprises, from bottom to top, a nano-taper array substrate (1), a reflecting layer (2), a first metal absorption film layer (3), a second metal absorption film layer (4), a third metal absorption film layer (5) and a dielectric antireflection layer (6).

5. The visible to mid-infrared ultra-broadband absorber of claim 4, wherein, The first metal absorption film layer (3) is a first metal ceramic film layer, the second metal absorption film layer (4) is a second metal ceramic film layer, and the third metal absorption film layer (5) is a third metal ceramic film layer.

6. The visible to mid-infrared ultra-broadband absorber of claim 5, wherein, The first metal ceramic film layer, the second metal ceramic film layer and the third metal ceramic film layer are Zr-ZrO2 metal ceramic film layers.

7. The visible to mid-infrared ultra-broadband absorber according to any one of claims 4 to 6, wherein, The thickness of the first metal absorption film layer (3) is greater than that of the second metal absorption film layer (4), and the thickness of the second metal absorption film layer (4) is greater than that of the third metal absorption film layer (5); wherein the thickness of the first metal absorption film layer (3) is 90-110 nm, the thickness of the second metal absorption film layer (4) is 50-60 nm, and the thickness of the third metal absorption film layer (5) is 36-44 nm.

8. The visible to mid-infrared ultra-broadband absorber of claim 4, wherein, The nano-taper array substrate (1) is a polyimide nano-taper array substrate, the period of the polyimide nano-taper array substrate is 500-1500 nm, the height is 600-1200 nm, and the bottom diameter is 600-1000 nm.

9. The visible to mid-infrared ultra-broadband absorber of claim 4, wherein, The reflecting layer (2) is a metal reflecting layer, the thickness of the metal reflecting layer is greater than or equal to 100 nm, the dielectric antireflection layer (6) is an alumina dielectric antireflection layer, and the thickness of the alumina dielectric antireflection layer is 63-77 nm.

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