A metasurface for humidity detection, preparation method thereof and humidity sensor

Abstract

The present invention provides a metasurface for humidity detection, a preparation method thereof and a humidity sensor, and relates to the field of optical devices. The metasurface for humidity detection provided by the present invention comprises a sensing layer, a transparent aluminum oxide layer and a gold mirror arranged in a stacked manner, the sensing layer comprises a reference module and a detection module, the arrangement of the reference module and the detection module presents a bound state in a continuous domain with symmetrical protection on an optical energy band, and the gold mirror comprises a gold layer and a titanium layer stacked from top to bottom. The bound state in the continuous domain with symmetrical protection supported by the metasurface provided by the present invention has a strong optical enhancement effect, which ensures that it can achieve broadband high-sensitivity humidity measurement, and the use of a smaller structural size ensures that it has a response speed and recovery ability far less than that of an electrical sensor, and has the advantages of simple structure, small size, wide measurement range, high sensitivity, fast response speed, strong environmental adaptability and high stability, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of optical devices, and in particular to a metasurface for humidity detection, a preparation method thereof, and a humidity sensor. Background Art

[0002] At present, humidity sensors mainly use electrical humidity sensors that rely on measuring the physical property changes of humidity-sensitive materials under different ambient humidity. Electrical humidity sensors have been widely used because of their relatively simple structure. When measuring ambient humidity, this type of sensor mainly reflects the ambient humidity by the relative electrical property changes of humidity-sensitive materials under different ambient humidity. Since the electrical properties of humidity-sensitive materials are not obvious under low humidity, the sensing range of electrical humidity sensors is generally narrow and concentrated in the high humidity range. Furthermore, electrical humidity sensors need to monitor the electrical property changes of humidity-sensitive materials through electrodes, and the aging of electrodes exposed to the external environment in the air will cause the sensor accuracy to decrease. In addition, electrical humidity sensors are difficult to use in extreme environments such as acidic and alkaline environments that are prone to corroding metal electrodes. Although conventional optical humidity sensors can avoid the problem of metal electrode aging, it is difficult to achieve high-sensitivity, broadband sensing range humidity sensing because the optical parameters of humidity-sensitive materials themselves change slightly under different humidity. Summary of the invention

[0003] The technical problem to be solved by the present invention is how to improve the environmental adaptability of the humidity sensor and enhance the sensitivity of broadband humidity sensing.

[0004] To solve the above problems, the first aspect of the present invention provides a metasurface for humidity detection, wherein the metasurface includes a stacked sensing layer, a transparent aluminum oxide layer and a gold mirror, the sensing layer includes a reference module and a detection module, the arrangement of the reference module and the detection module presents a symmetrically protected continuous domain bound state on the optical energy band, and the gold mirror includes a gold layer and a titanium layer stacked from top to bottom.

[0005] Preferably, the material of the detection module is a polymer or ceramic. In the technical solution provided by the present invention, the material of the detection module is a material that is sensitive to humidity and can undergo reversible changes in its morphology and spectrum after reacting with water.

[0006] Preferably, the detection module has a form selected from any one of a grating structure, a waveguide structure and a grating-waveguide composite structure.

[0007] Preferably, the control module is any one of glass, ceramics and high molecular polymer. In the technical solution provided by the present invention, the material of the detection module is a material that is insensitive to humidity and whose morphology and spectrum do not change after reacting with water.

[0008] Preferably, the shape of the control module is selected from any one of a grating structure, a square array and a disk array.

[0009] Preferably, the thickness of the transparent aluminum oxide layer is less than or equal to 100 nm, the thickness of the gold layer is greater than or equal to 100 nm, and the thickness of the titanium layer is in the range of 3 to 10 nm. In the technical solution provided by the present invention, the role of the transparent aluminum oxide layer is to enhance the amplified sensing effect, and the role of the gold layer is to serve as a reflective layer to ensure that light energy is fully reflected.

[0010] The technical principle of the metasurface for humidity detection provided by the present invention: In the metasurface for humidity detection provided by the present invention, the morphology and spectrum of the control module will not change with humidity, and the morphology of the detection module will change reversibly with humidity. The arrangement of the control module and the detection module presents a bound state in a continuous domain protected by symmetry on the optical energy band. Based on this, the control module and the detection module can change the symmetry of the control module-detection module by sensing the change in external humidity. On this basis, when the humidity changes, the refractive index of the detection module changes due to the change in the morphology of the detection module, which breaks the symmetry of the control module-detection module in both the dielectric constant and the geometric directions. At this time, the continuous bound state supported by the symmetrical structure at the energy band Γ point is converted into a bound state in the quasi-continuous domain in the asymmetric structure, so that a pattern of the corresponding wavelength appears on the spectrum. With the change of external humidity, the asymmetry of the system is different, so that the continuous bound state in the structure is converted into a bound state in the quasi-continuous domain to different degrees, and the bound state in the quasi-continuous domain shows different quality factors (Q factors) under different external humidity. In addition, due to the metal loss of gold, the high quality factor mode will suffer greater loss in the structure, making the relative intensity of the mode lower. In addition, due to the change of structure, a certain dispersion will be generated during the transition of bound states in the quasi-continuous domain. Therefore, the external humidity can be defined by the mode Q factor, mode spectral shift and mode intensity in the overall system.

[0011] The second aspect of the present invention provides a method for preparing the metasurface for humidity detection according to the first aspect, comprising the following steps:

[0012] S1: Using magnetron sputtering, electron beam evaporation or atomic layer deposition method, a titanium layer, a gold layer and a transparent aluminum oxide layer are sequentially deposited on a clean silicon wafer;

[0013] S2: Spin coating the detection module material on the surface of the transparent aluminum oxide layer, and preparing the detection module by electron beam exposure or photolithography;

[0014] S3: Using a chemical vapor deposition process, a reference module material is deposited on the surface of the transparent aluminum oxide layer, and then a peeling process is performed to obtain a reference module to obtain a meta-surface for humidity detection.

[0015] In the above-mentioned preparation method provided by the present invention, the stripping process omits the steps such as sputtering chromium in the hard mask etching process, and the process flow is relatively short.

[0016] The third aspect of the present invention provides another method for preparing the metasurface for humidity detection according to the first aspect, comprising the following steps:

[0017] SA: Titanium layer, gold layer, and transparent aluminum oxide layer deposited sequentially on a clean silicon wafer using magnetron sputtering, electron beam evaporation, or atomic layer deposition;

[0018] SB: Using chemical vapor deposition, depositing the reference module material on the surface of the transparent aluminum oxide layer and spin-coating PMMA resist on the surface of the reference module material, exposing, using magnetron sputtering or electron beam evaporation to build a chromium film as a hard mask on the reference module material, and forming the reference module by plasma etching;

[0019] SC: Electron beam exposure is used to directly prepare the detection module on the surface of the transparent aluminum oxide layer using the detection module material to obtain a meta-surface.

[0020] In the above-mentioned preparation method provided by the present invention, a hard mask is used to etch the reference module. Compared with using a stripping process, the morphology of the reference module is more complete and the processing repeatability is higher.

[0021] A third aspect of the present invention provides a humidity sensor, which includes an optical module for converting humidity change information into spectral information, and the optical module includes the above-mentioned metasurface for humidity detection.

[0022] Preferably, the optical module further includes a light source and a spectrometer.

[0023] Preferably, the humidity sensor further comprises a single chip microcomputer and a control circuit for receiving and processing output information of the optical module.

[0024] The working principle of the humidity sensor provided by the present invention is as follows: a light source is irradiated onto a metasurface. Since the metasurface has different absorption properties for light of a specific wavelength at different humidity levels, the light is reflected on the metasurface and collected by a spectrometer. The corresponding ambient humidity data can be obtained by analyzing the obtained spectral information. The ambient humidity data is output by the spectrometer and then received by a single-chip microcomputer. After the spectrometer data is processed and analyzed inside the single-chip microcomputer, the data can be uploaded to a subsequent host or cloud through an onboard antenna.

[0025] The present invention has the following beneficial effects:

[0026] The metasurface and humidity sensor using the metasurface provided by the present invention have a strong optical enhancement effect in the bound state BIC in the continuous domain of symmetry protection supported by the metasurface, which can achieve high-sensitivity humidity measurement, and ensure that the metasurface has a response speed and recovery ability far less than that of electrical sensors while using a smaller structural size. At the same time, since the device adopts all-optical measurement, no external electrodes are required, which ensures the stability of the sensor in complex environments.

[0027] The present invention also provides a method for preparing a metasurface, which is simple to operate. The metasurface and humidity sensor prepared using the preparation method provided by the present invention have the advantages of simple structure, small size, wide measurement range, high sensitivity, fast response speed, strong environmental adaptability, and high stability, and have broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a metasurface provided for a specific embodiment of the present invention;

[0029] Figure 2 A schematic diagram of the technical principle of detecting humidity on a metasurface provided in a specific embodiment of the present invention;

[0030] Figure 3 A diagram showing the field intensity variation of the metasurface provided in Example 1 of the present invention;

[0031] Figure 4 A schematic diagram of a process for preparing a metasurface provided in Example 2 of the present invention;

[0032] Figure 5 A schematic diagram of a process for preparing a metasurface is provided for Example 3 of the present invention;

[0033] Figure 6 A schematic diagram of the structure of a humidity sensor provided in a specific embodiment of the present invention;

[0034] Figure 7 Provides a reflectance spectrum diagram of a metasurface at different humidity levels for Example 4 of the present invention;

[0035] Figure 8 A linear fitting diagram of the sensitivity of the metasurface provided in Example 4 of the present invention defined according to different situations.

[0036] Description of reference numerals:

[0037] 1. Sensing layer; 2. Transparent aluminum oxide layer; 3. Gold mirror; 11. Control module; 12. Detection module; 31. Gold layer; 32. Titanium layer. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0039] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0040] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventionally understood meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments is carried out in accordance with the protocols and parameters given by the manufacturer.

[0041] In the description of the present invention, it should be noted that the terms "left", "right", "inside", "outside", "front", "back", "head", "tail", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0042] In order to solve the problems of slow response speed, narrow detection range, poor recovery and stability of electrical humidity sensors in the prior art, a specific embodiment of the present invention provides a metasurface for humidity detection, such as Figure 1 As shown, the metasurface includes a sensing layer 1, a transparent aluminum oxide layer 2 and a gold mirror 3 which are stacked. The sensing layer 1 includes a control module 11 and a detection module 12. The arrangement of the control module 11 and the detection module 12 presents a symmetrically protected continuous domain bound state BIC on the optical energy band. The gold mirror 3 includes a gold layer 31 and a titanium layer 32 which are stacked from top to bottom.

[0043] In the above embodiment, the control module 11 and the detection module 12 are used to monitor the ambient humidity in real time; the role of the transparent aluminum oxide layer 2 is to enhance the overall sensing performance of the metasurface, and its implementation principle is: as an isolation layer, it separates the high-loss metal from the low-loss photonic structure to improve the mode Q value; the role of the gold layer 31 in the gold mirror 3 is to serve as a reflective layer to improve the overall reflectivity of the structure, and the titanium layer 32 is used as an adhesion layer to fix the metasurface on the substrate in actual production activities.

[0044] In the metasurface provided in the above-mentioned embodiment, the arrangement of the control module 11 and the detection module 12 presents a bound state in a continuous domain of symmetry protection on the optical energy band, wherein the material of the detection module 12 is a humidity-sensitive material, and the material of the control module 11 is a humidity-insensitive material. On this basis, when the humidity changes, the detection module 12 will expand or contract according to the different humidity, while the control module 11 will not change its shape. Based on this, the sensing layer 1 can change its own symmetry by sensing the external humidity. When the humidity changes, the refractive index of the detection module 12 changes due to the change in its shape, so that the symmetry of the sensing layer 1 is broken in both the dielectric constant and geometric directions. At this time, the symmetrical structure supported by The continuous bound state located at the Γ point of the energy band is converted into a bound state in the quasi-continuous domain in the asymmetric structure, so that a peak of the corresponding wavelength appears on the spectrum. As the external humidity changes, the asymmetry of the system is different, so that the continuous bound state in the structure is converted into a bound state in the quasi-continuous domain to different degrees. The bound state in the quasi-continuous domain shows different Q factors under different external humidity. In addition, due to the metal loss of the reflective layer, the high quality factor mode will suffer greater loss in the structure, making the relative intensity of the mode lower. In addition, due to the change of the structure, a certain dispersion will also be generated during the transformation of the bound state in the quasi-continuous domain. Therefore, the external humidity can be defined by the mode Q factor, mode spectrum displacement, and mode intensity in the overall system. The metasurface provided by the above embodiment is particularly suitable for the detection of humidity of 35~90%.

[0045] In a specific embodiment, the material of the detection module 12 can be selected from materials such as high molecular polymers, ceramics, etc. that are sensitive to humidity and whose morphology and spectrum can undergo reversible changes after reacting with water.

[0046] In a specific embodiment, the form of the detection module 12 can be selected from any one of a grating structure, a waveguide structure, and a grating-waveguide composite structure.

[0047] In a specific embodiment, the material of the control module 11 can be glass, ceramic, high molecular polymer, etc., which are insensitive to humidity and whose morphology and spectrum do not change after reacting with water.

[0048] In a specific embodiment, the shape of the control module 11 is selected from any one of a grating structure, a square array and a disk array.

[0049] In a specific embodiment, the thickness of the transparent aluminum oxide layer 2 is less than or equal to 100 nm, the thickness of the gold layer 31 is greater than or equal to 100 nm, and the thickness of the titanium layer 32 is in the range of 3 to 10 nm.

[0050] A specific embodiment of the present invention further provides a method for preparing the aforementioned metasurface for humidity detection, which specifically comprises the following steps:

[0051] S1: Using magnetron sputtering deposition method, a titanium layer 32, a gold layer 31, and a transparent aluminum oxide layer 2 are sequentially deposited on a clean silicon wafer;

[0052] S2: using an electron beam exposure method to directly prepare a polyvinyl alcohol grating on the surface of the transparent aluminum oxide layer 2;

[0053] S3: Using a chemical vapor deposition method, a silicon dioxide layer is deposited on the surface of the transparent aluminum oxide layer 2, and a silicon dioxide grating is directly prepared by a lift-off process to obtain a metasurface.

[0054] The method omits steps such as sputtering chromium in the hard mask etching process through a stripping process, and the process flow is relatively short.

[0055] In a specific embodiment, the aforementioned metasurface for humidity detection can also be prepared by the following steps:

[0056] SA: A titanium layer 32, a gold layer 31, and a transparent aluminum oxide layer 2 are sequentially deposited on a clean silicon wafer using a magnetron sputtering deposition method;

[0057] SB: A silicon dioxide layer is deposited on the surface of the transparent aluminum oxide layer 2 by chemical vapor deposition, a PMMA resist is spin-coated on the surface of the silicon dioxide layer, exposed, and a chromium film is constructed on the silicon dioxide layer by magnetron sputtering as a hard mask, and a silicon dioxide grating is formed by plasma etching;

[0058] SC: Using the electron beam exposure method, polyvinyl alcohol gratings are directly prepared on the surface of the transparent aluminum oxide layer 2 to obtain a metasurface.

[0059] The above method uses a hard mask to etch the reference material. Compared with using a stripping process, the morphology of the reference module is more complete and the processing repeatability is higher.

[0060] Based on the aforementioned metasurface for humidity detection, a specific embodiment of the present invention further provides a humidity sensor, which includes a digital network module and an optical module. For specific principles, see Figure 6 .

[0061] In a specific embodiment, the optical module specifically includes a light source, the aforementioned metasurface, a spectrometer and a control circuit, and the digital network module includes a single-chip microcomputer and a host or a cloud.

[0062] In a specific embodiment, the light source can emit incident light, which is irradiated onto the metasurface after being microscopically focused, collimated and polarized. At this time, the sensing layer 1 of the metasurface will change its shape due to the change in environmental humidity. On this basis, the reflection spectrum of the reflected light in the spectrometer will also change. The relevant data is received by the microcontroller after being output through the spectrometer. After the spectrometer data is processed and analyzed inside the microcontroller, the data can be uploaded to the subsequent host or cloud through the on-board antenna.

[0063] The technical solution of the present invention is further illustrated by specific embodiments below.

[0064] Example 1

[0065] In this embodiment, the material used for the detection module 12 of the metasurface is polyvinyl alcohol, and the shape of the detection module 12 is a grating structure; the material of the control module 11 is silicon dioxide, and the shape of the control module 11 is a grating structure. In this embodiment, at 90% humidity, the grating pitch of the silicon dioxide grating is 710nm, and the grating pitch of the polyvinyl alcohol grating is 710nm. A 710nm period includes silicon dioxide grating strips and polyvinyl alcohol grating strips with a spacing of 46nm. In this embodiment, the height of the grating strips of the silicon dioxide grating is h1, h1=800nm, and the width is w1, w1=250nm. The height of the grating strips of the polyvinyl alcohol grating is h2, h2=h1×β, and the width of the grating strips of the polyvinyl alcohol grating is w2=w1×β, where β is the relative shrinkage coefficient of polyvinyl alcohol relative to 90% humidity at the corresponding humidity. This parameter increases with the increase of the external humidity. When the external humidity is 90%, the β value is 1, and when the external humidity is 35%, the β value is 0.88864. In this embodiment, the thickness of the transparent aluminum oxide layer 2 is 20nm, the thickness of the gold layer 31 is 150nm, and the thickness of the titanium layer 32 is 3nm.

[0066] See also Figure 2 The metasurface provided in this embodiment can change its topological symmetry by sensing the external humidity, and open its optical energy band by adjusting the symmetry. For details, see Figure 2 a in the figure, the continuous bound state with the band gap used for sensing is marked as 2 . See Figure 2 b, as the humidity changes from 35% to 90%, its band gap is opened, and the continuous bound state it supports is transformed into a bound state in the quasi-continuous domain. The spectrum shows a high Q peak, and strong field enhancement appears in the spectrum. For specific field intensity diagrams, see Figure 3As the band gap opens, the BIC (continuous bound state) supported by the structure is transformed into Quasi-BIC (bound state in the quasi-continuous domain). The reason why the structural band gap can change is that: on this basis, when the humidity changes, the polyvinyl alcohol grating will expand or contract according to different humidity, while the silica grating will not change its morphology. Based on this, the polyvinyl alcohol grating and the silica grating can change their own symmetry by sensing the external humidity. When the humidity changes, the refractive index of the polyvinyl alcohol changes due to the morphological change, which breaks the symmetry of the silica grating and the polyvinyl alcohol grating in terms of dielectric constant and geometry. At this time, the continuous bound state supported by the symmetrical structure at the Γ point of the energy band is transformed into the quasi-continuous domain bound state in the asymmetric structure. The peak of the corresponding wavelength appears on the spectrum. As the external humidity changes, the asymmetry of the system is different, so that the continuous bound state in the structure is transformed into the bound state in the quasi-continuous domain to different degrees. The bound state in the quasi-continuous domain shows different Q factors under different external humidity. In addition, due to the metal loss of the reflection layer, the high quality factor mode will suffer greater loss in the structure, making the relative intensity of the mode lower. In addition, due to the change of the structure, a certain dispersion will be generated during the transformation of the bound state in the quasi-continuous domain. Therefore, the external humidity can be defined by the mode Q factor, mode spectrum displacement, and mode intensity in the overall system. Figure 2 It can be seen that the metasurface provided by the present invention is particularly suitable for humidity detection in the range of 35% to 90%, and has the advantages of fast response speed and strong recovery. In addition, due to the use of all-optical measurement, the metasurface provided by the present invention also has the advantage of strong environmental adaptability.

[0067] Example 2

[0068] See also Figure 4 This embodiment provides a method for preparing a metasurface for humidity detection, comprising the following steps:

[0069] a: After magnetron sputtering deposition of 3nm titanium as an adhesion layer, 150nm gold was deposited as a reflective layer;

[0070] b: A 20 nm thick transparent aluminum oxide layer 2 is magnetron sputtered on the surface of the gold layer 31 to enhance reflection;

[0071] c: Spin-coat 710nm thick polyvinyl alcohol on the transparent alumina surface;

[0072] d: After exposing polyvinyl alcohol using electron beam exposure, the PVA grating was prepared using deionized water development under heating conditions;

[0073] e: a layer of polymethyl methacrylate (PMMA) is spin-coated on the surface of the transparent aluminum oxide layer 2, and the thickness of PMMA is greater than the height of the polyvinyl alcohol grating strips;

[0074] f: Use electron beam exposure to overlay PMMA on the original basis, and use MIBK to develop PMMA;

[0075] g: 800nm ​​thick silicon dioxide was deposited using chemical vapor deposition;

[0076] h: Use acetone to remove residual PMMA and prepare SiO 2 Grating and obtain the metasurface.

[0077] Example 3

[0078] See also Figure 5 This embodiment provides another method for preparing a metasurface for humidity detection, comprising the following steps:

[0079] a: After magnetron sputtering deposition of 3nm titanium as an adhesion layer, 150nm gold was deposited as a reflective layer;

[0080] b: Transparent aluminum oxide with a thickness of 20 nm is magnetron sputtered on the surface of the gold layer 31 to enhance reflection;

[0081] c: 800 nm thick silicon dioxide is deposited on the surface of the transparent aluminum oxide layer 2 using chemical vapor deposition;

[0082] d: Spin-coat a layer of PMMA on the surface of silicon dioxide;

[0083] e: PMMA was exposed using electron beam exposure and developed using methyl isobutyl ketone (MIBK);

[0084] f: Deposit a thin chromium film using magnetron sputtering as a mask;

[0085] g: Use acetone to remove residual PMMA;

[0086] h: SiO2 grating fabricated using plasma etching;

[0087] i: Pickling to remove the metal on the top of the silicon dioxide grating;

[0088] j: Spin-coat 800 nm thick polyvinyl alcohol on the surface of the transparent aluminum oxide layer 2 under high humidity conditions;

[0089] k: After exposing polyvinyl alcohol using electron beam exposure, the polyvinyl alcohol grating was prepared by developing it with deionized water under heating conditions;

[0090] l: Heat is used to remove water molecules from the polyvinyl alcohol grating, breaking the structural symmetry and thus obtaining a metasurface.

[0091] Example 4

[0092] The metasurface provided in Example 1 was used to measure the reflectance spectrum of the metasurface under 35% to 90% humidity conditions. The results are shown in Figure 7 As the external humidity increases, the peak position of the metasurface spectrum in the humidity sensor gradually redshifts, and its relative intensity gradually decreases; see Figure 8 At low humidity, the linear fit of the metasurface defined by relative intensity is (S1=0.45 / RH), at high humidity, the linear fit of the metasurface defined by relative intensity is (S2=2.63 / RH), and the linear fit of the metasurface defined by spectral shift is S=0.22 (nm / RH).

[0093] The metasurface and humidity sensor provided in the specific embodiments of the present invention are essentially based on optical principles, and have the advantages of fast response speed, humidity sensitivity, fast recovery, and high stability. At the same time, since the metasurface provided by the present invention is based on optical principles, it is not affected by the environmental pH and has the advantage of high stability. In addition, the metasurface provided by the present invention can be integrated into a humidity sensor system for large-area industrial systems through network bridging. The humidity sensor system has a simple structure, does not require the use of a large number of external components, and has the advantage of high integration.

[0094] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A metasurface for humidity detection, characterized in that: The invention comprises a sensing layer (1), a transparent aluminum oxide layer (2) and a gold mirror (3) which are stacked in layers. The sensing layer (1) comprises a reference module (11) and a detection module (12). The detection module (12) has a morphology selected from any one of a grating structure, a waveguide structure and a grating-waveguide composite structure. The reference module (11) has a morphology selected from any one of a grating structure, a square array and a disk array. The arrangement of the reference module (11) and the detection module (12) presents a bound state in a continuous domain with symmetrical protection in an optical energy band. The gold mirror (3) comprises a gold layer (31) and a titanium layer (32) which are stacked in layers from top to bottom.

2. The metasurface for humidity detection according to claim 1, characterized in that: The material of the detection module (12) is a high molecular polymer or ceramic.

3. The metasurface for humidity detection according to claim 1, characterized in that: The material of the control module (11) is selected from any one of glass, ceramic and high molecular polymer.

4. The metasurface for humidity detection according to claim 1, characterized in that: The thickness of the transparent aluminum oxide layer (2) is less than or equal to 100 nm, the thickness of the gold layer (31) is greater than or equal to 100 nm, and the thickness of the titanium layer (32) is in the range of 3 to 10 nm.

5. A method for preparing a metasurface for humidity detection according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: using magnetron sputtering, electron beam evaporation or atomic layer deposition, sequentially depositing a titanium layer (32), a gold layer (31), and a transparent aluminum oxide layer (2) on a clean silicon wafer; S2: Spin coating a detection module material on the surface of the transparent aluminum oxide layer (2), and preparing a detection module (12) by electron beam exposure or photolithography; S3: Using a chemical vapor deposition process, a reference module material is deposited on the surface of the transparent aluminum oxide layer (2), and then a peeling process is performed to obtain a reference module (11) to obtain a meta-structured surface.

6. A method for preparing a metasurface for humidity detection according to any one of claims 1 to 4, characterized in that: The following steps are involved: SA: a titanium layer (32), a gold layer (31), and a transparent aluminum oxide layer (2) deposited in sequence on a clean silicon wafer using magnetron sputtering, electron beam evaporation, or atomic layer deposition; SB: using a chemical vapor deposition process, depositing a reference module material on the surface of the transparent aluminum oxide layer (2) and spin-coating a PMMA resist on the surface of the reference module material, exposing the material, using magnetron sputtering or electron beam evaporation to form a chromium film as a hard mask on the reference module material, and forming a reference module (11) by plasma etching; SC: Using an electron beam exposure method, a detection module (12) is directly prepared on the surface of a transparent aluminum oxide layer (2) using a detection module material to obtain a meta-structured surface.

7. A humidity sensor, characterized in that: It comprises an optical module for converting humidity change information into spectral information, and the optical module comprises a metasurface for humidity detection as described in any one of claims 1 to 4.

8. The humidity sensor according to claim 7, characterized in that: The optical module also includes a light source and a spectrometer.

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