An optical anti-counterfeiting GaN metasurface and an optical anti-counterfeiting product

Abstract

The present invention belongs to the field of optical anti-counterfeiting technology and relates to an optical anti-counterfeiting GaN metasurface and an optical anti-counterfeiting product. The optical anti-counterfeiting metasurface comprises: a substrate layer and a light-reflecting structure; the light-reflecting structure is disposed on one side surface of the substrate layer and is used to reflect incident light, thereby outputting outgoing light with a wavelength that continuously changes within a set angle range; wherein the light-reflecting structure comprises a plurality of first reflecting columns arranged in an array on one side surface of the substrate layer, with a groove between two adjacent first reflecting columns. By adopting the optical anti-counterfeiting GaN metasurface provided by this solution, it is possible to select a 10 nm narrowband wavelength for the incident light. Under sunlight conditions, highly saturated outgoing light can be observed at any orientation within the plane of the metasurface based on human vision, and the color of the outgoing light changes continuously with the observation angle, thereby achieving an optical anti-counterfeiting function without the use of special optical materials, with low cost and simple structure.

Description

Technical Field

[0001] The present invention relates to the field of optical anti-counterfeiting technology, and in particular to an optical anti-counterfeiting GaN metasurface and an optical anti-counterfeiting product. Background Art

[0002] With the continuous advancement of science and technology and the continuous development of the social economy, anti-counterfeiting technology is also constantly innovating and improving. In recent years, optical anti-counterfeiting technology has been widely used in areas such as currency, commodities, and identity documents, and has gradually developed into a key means of ensuring product authenticity and preventing counterfeiting in modern society. In the currency field, the use of high-resolution optical imaging technology can produce banknotes with tiny text and details, increasing the difficulty of currency counterfeiting. In the commodity field, by adding logos and labels with specific optical effects to pharmaceuticals, luxury goods, and electronic products, consumers can determine the authenticity of the goods through simple optical detection methods. In the field of identity documents, the use of optical imaging technology, optical information storage technology, and optical color change technology can produce highly anti-counterfeiting identity cards, passports, and driver's licenses.

[0003] Existing optical anti-counterfeiting technologies mainly include photovariable anti-counterfeiting, multispectral anti-counterfeiting and fluorescent anti-counterfeiting. Photovariable anti-counterfeiting uses optical principles and the optical properties of special materials to achieve anti-counterfeiting functions. For example, the molecular structure of photovariable materials changes under the irradiation of light of different wavelengths, resulting in changes in the characteristics of absorbing and reflecting light, producing a photovariable effect, so that the authenticity of the product can be verified based on this unique photovariable effect. However, since photovariable materials require special chemical components and complex preparation processes, the application of photovariable material anti-counterfeiting technology to products will lead to increased production costs of the products. Multispectral anti-counterfeiting refers to the fact that multispectral pigments or dyes show special colors under light of a specific wavelength band, so that the authenticity of the product can be verified based on this color characteristic. However, this optical anti-counterfeiting technology relies on specific lighting conditions, and the spectral characteristics of multispectral materials in specific wavelength bands are easily interfered with by other substances. For example, stains or impurities on the surface of the product will absorb or scatter light of a specific wavelength band, thereby affecting the accuracy of the anti-counterfeiting effect. Fluorescent anti-counterfeiting uses the fluorescent property of substances to display special brightness or color under ultraviolet light or light of a specific wavelength to verify the authenticity of products. However, this optical anti-counterfeiting technology also requires specific lighting conditions and the use of professional equipment such as ultraviolet lamps. In addition, after long-term use or multiple exposures to light, the fluorescent brightness of fluorescent materials will gradually decay, resulting in a worse anti-counterfeiting effect.

[0004] In summary, existing optical anti-counterfeiting technologies have the problems of high cost, high requirements for lighting conditions, and poor anti-counterfeiting effect. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of the optical anti-counterfeiting technology in the prior art, such as high cost, high requirements on lighting conditions, and poor anti-counterfeiting effect.

[0006] To solve the above technical problems, the present invention provides an optical anti-counterfeiting GaN metasurface, comprising:

[0007] basal layer;

[0008] a light reflecting structure, disposed on one surface of the substrate layer, for reflecting incident light, thereby outputting outgoing light with a wavelength that continuously changes within a set angle range;

[0009] The light reflecting structure includes a plurality of first reflecting columns, which are arranged in an array on one side surface of the base layer, and a groove is provided between two adjacent first reflecting columns.

[0010] In the present application, a highly symmetric periodic structure is provided over the entire area of the substrate layer to form a bound states in the continuous (BIC) pattern capable of filtering incident light. When light beams of various wavelengths in sunlight (i.e., parallel white light) are incident on the light-reflecting structure, they are diffracted under the periodic modulation of the first reflective column. Due to the different diffraction angles of light beams of different wavelengths, the light beams of each diffraction order interfere with each other and destructively. Light beams of some wavelengths are trapped in the light-reflecting structure, while light beams of specific wavelengths are reflected by the light-reflecting structure and emitted at specific angles. Simultaneously, due to the combined effects of the quasi-BIC pattern and the dispersion of the light-reflecting structure itself, the intensity of the emitted light of different wavelengths reflected by the light-reflecting structure increases or decreases to varying degrees within a set angle range. As a result, the emitted light with continuously changing wavelengths can be observed within a set angle range, and thus the emitted light with continuously changing colors can be observed by the human eye, thus achieving an optical anti-counterfeiting function.

[0011] Preferably, the light reflecting structure further includes a second reflecting column, which is arranged between adjacent first reflecting columns, and the top of the second reflecting column contacts the bottom of the groove;

[0012] The height of the second reflective column is smaller than the height of the first reflective column.

[0013] In the present application, by setting a second reflective column with a height smaller than that of the first reflective column at the groove, the light reflection structure can still form a quasi-BIC mode, thereby selecting the wavelength of the incident light, so that the wavelength of the outgoing light continuously changes within the set angle range, thereby realizing the optical anti-counterfeiting function.

[0014] Preferably, it also includes:

[0015] The matching layer is arranged on the surface of the light reflecting structure away from the base layer. The matching layer is provided with a protrusion matching the groove on the side close to the light reflecting structure, and the top of the protrusion contacts the top of the groove.

[0016] In this application, covering the surface of the light-reflecting layer with a matching layer can increase the upper and lower symmetry of the optical anti-counterfeiting metasurface, thereby extending the bandwidth of the quasi-BIC mode to more than 100nm, that is, broadening the range of wavelength variation of the outgoing light, so that the human eye can more clearly observe the color changes of the outgoing light at different output angles, thereby improving the anti-counterfeiting effect.

[0017] Preferably, the material of the base layer is aluminum oxide or silicon dioxide; and / or

[0018] The material of the light reflection structure is gallium nitride.

[0019] In the present application, the base layer and the light-reflecting structure may also be made of other materials. Preferably, aluminum oxide has strong corrosion resistance and chemical stability, can maintain structural integrity under various environments, provide stable support for the light-reflecting structure, and ensure the long-term reliability of the entire optical anti-counterfeiting metasurface. In addition, aluminum oxide also has good optical transparency, and relatively low absorption and scattering of light; gallium nitride has a high refractive index, and can achieve a strong light reflection effect during the light reflection process, enhance the optical linearity such as diffraction and interference of light in the light-reflecting structure, thereby better realizing the quasi-BIC mode; in addition, aluminum oxide and gallium nitride have a high degree of adaptability in the lattice structure, so that the light-reflecting structure can be better grown on the base layer, forming a high-quality interface, reducing lattice defects and stress, and improving the optical performance and stability of the optical anti-counterfeiting metasurface.

[0020] Preferably, the size ratio of the first reflective column to the groove is 4:1; and / or

[0021] The diameter or side length of the first reflective column is 160 nm to 200 nm; and / or

[0022] The height of the first reflective column is 160 nm to 200 nm.

[0023] In the present application, the change in the size of the light-reflecting structure will directly affect the diffraction and interference of light therein, producing different quasi-BIC modes, so that the wavelength range that can be reflected by the light-reflecting structure changes, achieving different wavelength screening effects, and thus causing the emitted light to produce different color changes within different set angle ranges.

[0024] Preferably, the setting angle range is 5°~25°; and / or

[0025] The wavelength range is 430nm~540nm.

[0026] In the present application, by changing the size of the light reflecting structure, the color of the emitted light can change within the range of 5°~25°, and the wavelength change range of the emitted light within the set angle range can reach 430nm~540nm, so that the change of the emitted light from blue-purple to bright green can be observed.

[0027] Preferably, when the diameter or side length of the first reflective column is 160 nm, the height of the first reflective column is 160 nm, and the size of the groove is 40 nm, the set angle range is 5°~25°, and the wavelength variation range is 430 nm~530 nm.

[0028] In the present application, by limiting the size of the first reflective cylinders and the size of the grooves between adjacent first reflective cylinders, the change of the emitted light from blue-violet to bright green can be observed within the range of 5° to 25°.

[0029] Preferably, when the diameter or side length of the first reflective column is 200 nm, the height of the first reflective column is 200 nm, and the size of the groove is 50 nm, the set angle range is 5°~15°, and the wavelength variation range is 500 nm~540 nm.

[0030] In the present application, by limiting the size of the first reflective cylinders and the size of the grooves between adjacent first reflective cylinders, a change in the emitted light from blue-green to yellow-green can be observed within a range of 5° to 15°.

[0031] Preferably, the first reflective column is a circular column, a square column or a polygonal column; and / or

[0032] The second reflective column is a circular column, a square column or a polygonal column.

[0033] The present invention also provides an optical anti-counterfeiting product, which includes the above-mentioned optical anti-counterfeiting GaN metasurface.

[0034] The optical anti-counterfeiting GaN supersurface provided by the present invention includes a base layer and a light-reflecting structure arranged on one side surface of the base layer. The light-reflecting structure is used to reflect incident light so that the wavelength of the emitted light continuously changes within a set emission angle range; the light-reflecting structure includes a plurality of first reflective columns, which are arranged in an array on one side surface of the base layer, and a groove is provided between two adjacent first reflective columns. By providing a highly symmetric periodic structure across the entire substrate, a bound states in the continuous (BIC) pattern is formed, capable of filtering incident light. When sunlight (i.e., parallel white light) of various wavelengths enters the reflective structure and is periodically modulated by the first reflective column, it diffracts. Due to the different diffraction angles of beams of different wavelengths, the beams of each diffraction order interfere with and destructively deflect each other. Light beams of some wavelengths are trapped in the reflective structure, while light beams of specific wavelengths are reflected by the structure and emitted at specific angles. Simultaneously, due to the combined effects of the quasi-BIC pattern and the dispersion of the reflective structure itself, the intensity of the emitted light of different wavelengths reflected by the reflective structure increases or decreases to varying degrees. Consequently, a continuously and slowly changing wavelength of emitted light can be observed within a set angle range, enabling the human eye to observe slowly changing colors of the emitted light. This application designs a light-reflecting structure with quasi-BIC characteristics to select the wavelength of incident light and output outgoing light of a specific wavelength. At the same time, the dispersion effect of the light-reflecting structure is combined to enhance or weaken the outgoing light of different wavelengths. The optical anti-counterfeiting function can be achieved under sunlight conditions, and the outgoing light band observed by the human eye at any angle is less than or equal to 10nm, with extremely high saturation. No special optical materials are required, the cost is low and the structure is simple. It can realize the light field control function in a quasi-two-dimensional plane at the sub-wavelength level, and has broad application prospects in the field of optical anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0036] Figure 1 This is a schematic diagram of the first structure of the optical anti-counterfeiting GaN metasurface provided in this application;

[0037] Figure 2 This is a schematic diagram of the second structure of the optical anti-counterfeiting GaN metasurface provided in this application;

[0038] Figure 3 A schematic diagram of the third structure of the optical anti-counterfeiting GaN metasurface provided in this application;

[0039] Figure 4Schematic diagram of the three-dimensional structure of the optical anti-counterfeiting GaN metasurface provided in this application;

[0040] Figure 5 Schematic diagram of the unit structure of the optical anti-counterfeiting GaN metasurface provided in this application;

[0041] Figure 6 Schematic diagram of the optical anti-counterfeiting GaN metasurface function provided in this application;

[0042] Figure 7 This is a flow chart of the preparation process of the optical anti-counterfeiting GaN metasurface provided in this application; wherein, Figure 7 (a) is a schematic diagram of the basal layer. Figure 7 (b) in the Figure 7 Schematic diagram of preparing a reflective layer on the structure shown in (a). Figure 7 (c) in the Figure 7 Schematic diagram of preparing a photoresist layer on the structure shown in (b). Figure 7 (d) in the Figure 7 Schematic diagram of preparing the first reflective column on the structure shown in (c). Figure 7 (e) in the Figure 7 Schematic diagram of preparing a matching layer on the structure shown in (d);

[0043] Figure 8 Schematic diagram of the color change of the output light of the optical anti-counterfeiting GaN metasurface provided in Example 1;

[0044] Figure 9 Schematic diagram of the transmittance of the optical anti-counterfeiting GaN metasurface provided in Example 1;

[0045] Figure 10 Schematic diagram of the energy band of the optical anti-counterfeiting GaN metasurface provided in Example 1; wherein, Figure 10 (a) is a schematic diagram showing the variation of the wavelength of the outgoing light with the wave vector. Figure 10 (b) is a schematic diagram of the change of quality factor with wave vector;

[0046] Figure 11 Schematic diagram of the transmittance of the optical anti-counterfeiting GaN metasurface provided in Example 2;

[0047] Figure 12 Schematic diagram of the energy band of the optical anti-counterfeiting GaN metasurface provided in Example 2; wherein, Figure 12 (a) is a schematic diagram showing the variation of the wavelength of the outgoing light with the wave vector. Figure 12 (b) is a schematic diagram of the change of quality factor with wave vector;

[0048] Explanation of the reference numerals in the specification: 1. base layer; 2. light reflecting structure; 21. first reflecting column; 22. groove; 23. second reflecting column; 3. matching layer; 31. protrusion; 200. reflecting layer; 300. photoresist layer. DETAILED DESCRIPTION

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0050] Bound States in the Continuum (BIC) modes are a unique optical phenomenon. In traditional optical systems, light typically propagates or scatters in a medium. BIC modes refer to the presence of special eigenstates in an optical system. Although these eigenstates are in a continuous scattering state spectrum, they can be completely bound within the optical system without radiation loss. This is because factors such as the optical structure and boundary conditions cause light to form stable standing wave modes under specific conditions, thereby being confined to a specific area.

[0051] BIC modes are categorized as perfect BIC and quasi-BIC. The perfect BIC mode involves completely confining the incident light within the optical structure. At this point, the interaction between light and matter reaches its peak, allowing the light field to be stored and enhanced for extended periods within the optical structure, resulting in greater optical nonlinear effects and higher light absorption. The quasi-BIC mode, on the other hand, is less effective at confining light than the perfect BIC mode, confining only a portion of the incident light. Consequently, both the light field localization and the intensity of the light-matter interaction are weaker. Because the quasi-BIC mode's light confinement and storage effects cannot meet the requirements of applications requiring strong optical effects, existing BIC mode applications and research have largely focused on the perfect BIC mode.

[0052] This application extends the partial confinement effect of the quasi-BIC mode on light to its filtering and screening function, and for the first time applies this characteristic of the quasi-BIC mode to the field of optical anti-counterfeiting. By designing a light-reflecting structure that can produce a quasi-BIC mode, the incident light is filtered and screened, thereby outputting reflected light of a specific wavelength. At the same time, under the dispersion effect of the light-reflecting structure itself, the intensity of reflected light of different wavelengths will be enhanced or weakened to varying degrees, thereby emitting outgoing light with a continuous and slowly changing wavelength within a specific angle range, thereby achieving optical anti-counterfeiting.

[0053] See also Figure 1 , Figure 1 This is a schematic diagram of the first structure of the optical anti-counterfeiting GaN supersurface provided in this application, which includes a base layer 1 and a light reflection structure 2.

[0054] The light-reflecting structure 2 is disposed on one side of the substrate layer 1. The light-reflecting structure 2 is used to reflect incident light, thereby outputting outgoing light with a wavelength that continuously changes within a set angle range. Specifically, the set angle range is 5° to 25°, and the wavelength range is 430nm to 540nm.

[0055] It is worth noting that based on human vision, the outgoing light with continuously changing color can be observed at any angle of this metasurface, and the outgoing light band observed at any angle is less than or equal to 10nm, with extremely high saturation.

[0056] The light reflective structure 2 includes a plurality of first reflective columns 21 , which are arranged in an array on one side of the base layer 1 , with a groove 22 between two adjacent first reflective columns 21 .

[0057] Specifically, the optical anti-counterfeiting metasurface provided by the present application forms a symmetrically protected quasi-BIC mode, and uses the symmetrically protected quasi-BIC mode to screen the incident light. The specific principle is: when the normal (z-axis) around the photonic crystal plate is When the structure is rotated by an angle, the parallel wave vector of a type of electromagnetic mode always remains unchanged. In order to ensure this feature, the parallel wave vector of this type of electromagnetic mode is usually located in the wave vector space. point (vertical incidence), at this time, the wave vectors of these modes have no horizontal component, that is, .exist Point, the even symmetric electromagnetic mode is completely decoupled from the odd symmetric electromagnetic mode. Due to the C2 symmetry of the structure, the even symmetric electromagnetic mode will be completely confined in the structure, while the odd symmetric electromagnetic mode will radiate out of the structure. When the radiation frequency is lower than the diffraction limit (diffraction limit definition ,in, represents the speed of light in vacuum, represents the refractive index of the ambient medium, represents the periodic constant), the radiation direction is only in the normal direction of the plate, leaving After the point, at least one of the horizontal wave vector components kx and ky of the electromagnetic mode is no longer zero. The rotation operation no longer ensures the invariance of the horizontal wave vector. Therefore, the wave vector space is deviated by oblique incidence. The point destroys the wave vector symmetry. Due to the loss of symmetry protection, the BIC will couple with the radiation mode to form a leaky quasi-BIC, causing energy to leak out.

[0058] Optionally, the first reflective column 21 may be a circular column, a square column or other polygonal column. The material of the base layer 1 may be one of aluminum oxide (Al2O3) and silicon dioxide (SiO2); the material of the light reflective structure 2 may be gallium nitride (GaN).

[0059] Preferably, in one embodiment of the present application, the material of the base layer 1 is aluminum oxide, and the material of the light reflecting structure 2 is gallium nitride. This is because aluminum oxide has good chemical stability and optical transparency, which can not only provide stable support for the light reflecting structure 2, but also will not affect the propagation and reflection of light in the light reflecting structure 2, which is beneficial to ensuring the intensity and quality of the optical signal; gallium nitride material has a high refractive index and can achieve a strong light reflection effect during the light reflection process, which is beneficial to modulating and manipulating light; at the same time, aluminum oxide and gallium nitride materials have a high degree of adaptability in the lattice structure, which also enables the light reflecting structure 2 to grow more stably on the surface of the base layer 1, thereby improving the optical performance and stability of the optical anti-counterfeiting metasurface.

[0060] like Figure 2 As shown, in some embodiments of the present application, the light reflective structure 2 further includes a second reflective column 23, which is disposed between adjacent first reflective columns 21, with the top of the second reflective column 23 in contact with the bottom of the groove 22. The height of the second reflective column 23 is less than the height of the first reflective column 21.

[0061] Optionally, the second reflective column 23 may be a circular column, a square column or other polygonal column.

[0062] like Figure 3 and Figure 4 As shown, in some embodiments of the present application, the optical anti-counterfeiting GaN metasurface also includes a matching layer 3.

[0063] The matching layer 3 is provided on the surface of the light reflecting structure 2 away from the base layer 1 . The matching layer 3 is provided with a protrusion 31 matching the groove 22 on the side close to the light reflecting structure 2 . The top of the protrusion 31 contacts the top of the groove 22 .

[0064] By embedding the light-reflecting structure 2 into the matching layer 3, the upper and lower symmetry of the optical anti-counterfeiting metasurface can be increased, thereby broadening the bandwidth of the quasi-BIC mode and extending the wavelength variation range of the outgoing light to 100nm, making it easier for the human eye to distinguish the color changes of the outgoing light and improving the anti-counterfeiting effect.

[0065] Optionally, the material of the matching layer may be SiO 2 , Al 2 O 3 , or an organic material, such as photoresist, PMMA, or protective glue.

[0066] like Figure 5 As shown, a reflective unit is composed of a single first reflective column 21 and a base layer 1 in the optical anti-counterfeiting GaN metasurface. In the figure, p represents the size of the reflective unit, r represents the radius of the first reflective column 21, and h represents the height of the first reflective column 21.

[0067] By changing the size of the light-reflecting structure 2, the diffraction and interference of light therein can be changed, thereby generating different quasi-BIC modes, so that the wavelength range that can be reflected by the light-reflecting structure 2 is changed, achieving different wavelength screening effects, and thus causing the emitted light to produce different color changes within different set angle ranges.

[0068] Furthermore, the size of the reflective unit is 200 nm to 250 nm. For example, the size of the reflective unit may be 200 nm, 220 nm, or 240 nm.

[0069] Furthermore, the size ratio of the first reflective column 21 to the groove 22 is 4:1.

[0070] Furthermore, the diameter or side length of the first reflective column 21 is 160 nm to 200 nm. For example, the diameter or side length of the first reflective column 21 may be 160 nm, 170 nm, 180 nm, 190 nm, or 200 nm.

[0071] Furthermore, the height of the first reflective column 21 is 160 nm to 200 nm. For example, the height of the first reflective column 21 may be 160 nm, 170 nm, 180 nm, 190 nm, or 200 nm.

[0072] This embodiment does not limit the shape of the groove 22. For example, the shape of the groove 22 can be a cylinder or a cubic column. When the shape of the groove 22 is a cylinder, the size of the groove 22 is the diameter of the cylinder; when the shape of the groove 22 is a cubic column, the size of the groove 22 is the side length of the cross section of the cubic column.

[0073] In one embodiment, when the diameter or side length of the first reflective column 21 is 160 nm, the height of the first reflective column 21 is 160 nm, and the size of the groove 22 is 40 nm, the angle range is set to 5°~25°, and the wavelength variation range is 430 nm~530 nm.

[0074] In another embodiment, when the diameter or side length of the first reflective column 21 is 200 nm, the height of the first reflective column 21 is 200 nm, and the size of the groove 22 is 50 nm, the angle range is set to 5°~15°, and the wavelength variation range is 500 nm~540 nm.

[0075] like Figure 6Shown is a functional schematic diagram of the optical anti-counterfeiting GaN metasurface. The light emitted by the sun includes various angles and wavelengths. When the sunlight is incident on the optical anti-counterfeiting metasurface, the angle at which the human eye is located represents the angle of incidence of the sunlight seen by the human eye. The optical anti-counterfeiting metasurface reflects light of different wavelengths at different output angles. As the observation angle of the human eye in any direction of the metasurface gradually expands from 0°, it can be clearly seen that the color of the output light changes continuously from blue to green.

[0076] Based on the optical anti-counterfeiting GaN metasurface provided in the above embodiment, the embodiment of the present application further provides an optical anti-counterfeiting product, which includes the above optical anti-counterfeiting GaN metasurface.

[0077] like Figure 7 FIG. 1 is a flow chart of a process for preparing an optical anti-counterfeiting GaN metasurface provided in this embodiment. The method for preparing the optical anti-counterfeiting GaN metasurface includes:

[0078] S10: Provide a base layer 1, such as Figure 7 As shown in (a) in .

[0079] S20: forming a reflective layer 200 on one side of the base layer 1, such as Figure 7 As shown in (b) in .

[0080] S30: Spin-coat a photoresist layer 300 on the side of the reflective layer 200 away from the base layer 1, and expose the photoresist layer 300 using a double-beam holographic exposure method to form a two-dimensional columnar structure, such as Figure 7 As shown in (c) in the figure.

[0081] S40: etching the photoresist layer 300 and the reflective layer 200 to form a light reflective structure including a plurality of first reflective columns 21, such as Figure 7 As shown in (d) in the figure.

[0082] S50: Depositing a matching layer 3 between adjacent first reflective columns 21 and on top of the first reflective columns 21, such as Figure 7 As shown in (e) in .

[0083] The technical solution of the present application is described in more detail below in combination with a plurality of embodiments and comparative examples. However, it should be understood that the following embodiments and comparative examples are only intended to explain and illustrate the technical solution and do not limit the scope of the present application. Example 1

[0084] This embodiment provides an optical anti-counterfeiting GaN metasurface, which includes a base layer, a light-reflecting structure and a photoresist layer. The light-reflecting structure includes a plurality of first reflective columns arranged in an array on one side surface of the base layer, and a groove is provided between two adjacent first reflective columns.

[0085] The material of the base layer is Al2O3, and the material of the light reflection structure is GaN.

[0086] The first reflective column is a cylinder.

[0087] The size of the reflective unit is 200 nm, the size ratio of the first reflective column to the groove is 4:1, the diameter of the first reflective column is 160 nm, and the height of the first reflective column is 160 nm.

[0088] like Figure 8 The figure shows a schematic diagram of the color change of the output light of the optical anti-counterfeiting GaN metasurface provided in this embodiment. It can be seen from the figure that this embodiment limits the size of the light reflection structure so that after the sunlight is incident on the optical anti-counterfeiting GaN metasurface, the output light can be observed to change from blue to green within the range of 5°~25°.

[0089] like Figure 9 The figure shows the transmittance of the optical anti-counterfeiting GaN metasurface provided in this embodiment. It can be clearly observed from the figure that when the incident light is incident vertically at 0°, the optical anti-counterfeiting GaN metasurface maintains low reflectivity for a beam with a wavelength of 410nm. As the incident angle gradually increases, a high-reflectivity slit appears and moves to higher wavelengths with dispersion. As can be seen from the figure, as the incident angle changes from 5° to 25°, the wavelength of the outgoing light gradually changes from 430nm to 530nm. Based on human vision, the outgoing light can be seen to continuously change from blue to green, indicating that the optical anti-counterfeiting GaN metasurface provided in this embodiment can use BIC and dispersion characteristics to achieve wavelength screening function.

[0090] like Figure 10 FIG. 1 is a schematic diagram of the energy bands of the optical anti-counterfeiting GaN metasurface provided in this embodiment; wherein, Figure 10 (a) is a schematic diagram showing the variation of the wavelength of the outgoing light with the wave vector. Figure 10 (b) in the figure is a schematic diagram showing the change of quality factor with wave vector. Figure 10 As can be seen from (a) in the figure, at a wavelength of about 410nm (the curve corresponding to solution = 2 in the figure), the optical anti-counterfeiting GaN metasurface appears a quasi-BIC mode, and Figure 10 As can be seen from (b) in the figure, the quality factor of the quasi-BIC mode reaches , which is much higher than the other curves, indicating that the optical anti-counterfeiting GaN metasurface provided in this embodiment can select and filter light of a specific wavelength with high precision. Example 2

[0091] This embodiment provides an optical anti-counterfeiting GaN metasurface, which includes a base layer, a light-reflecting structure and a photoresist layer. The light-reflecting structure includes a plurality of first reflective columns arranged in an array on one side surface of the base layer, and a groove is provided between two adjacent first reflective columns.

[0092] The material of the base layer is Al2O3, and the material of the light reflection structure is GaN.

[0093] The first reflective column is a cylinder.

[0094] The size of the reflective unit is 250 nm, the size ratio of the first reflective column to the groove is 4:1, the diameter of the first reflective column is 200 nm, and the height of the first reflective column is 200 nm.

[0095] like Figure 11 The figure shows the transmittance of the optical anti-counterfeiting GaN metasurface provided in this embodiment. It can be clearly observed from the figure that when the incident light is incident vertically at 0°, the optical anti-counterfeiting GaN metasurface maintains low reflectivity for a beam with a wavelength of 490nm. As the incident angle gradually increases, a high-reflectivity slit appears and moves to higher wavelengths with dispersion. As can be seen from the figure, as the incident angle changes from 5° to 15°, the wavelength of the outgoing light gradually changes from 500nm to 530nm. Based on human vision, the outgoing light can be seen to continuously change from blue-green to yellow-green, indicating that the optical anti-counterfeiting GaN metasurface provided in this embodiment can use BIC and dispersion characteristics to achieve wavelength screening function.

[0096] like Figure 12 FIG. 1 is a schematic diagram of the energy bands of the optical anti-counterfeiting GaN metasurface provided in this embodiment; wherein, Figure 12 (a) is a schematic diagram showing the variation of the wavelength of the outgoing light with the wave vector. Figure 12 (b) in the figure is a schematic diagram showing the change of quality factor with wave vector. Figure 12 As can be seen from (a) in the figure, at a wavelength of about 500nm (the curve corresponding to solution = 1 in the figure), the optical anti-counterfeiting GaN metasurface appears a quasi-BIC mode, and Figure 12 As can be seen from (b) in the figure, the quality factor of the quasi-BIC mode reaches , which is much higher than the other curves, indicating that the optical anti-counterfeiting GaN metasurface provided in this embodiment can select and filter light of specific wavelengths with high precision. Example 3

[0097] This embodiment provides an optical anti-counterfeiting GaN metasurface, which includes a base layer and a light-reflecting structure, wherein the light-reflecting structure includes a plurality of first reflective columns arranged in an array on one side surface of the base layer, and a groove is provided between two adjacent first reflective columns.

[0098] The material of the base layer is Al2O3, and the material of the light reflection structure is GaN.

[0099] The first reflective column is a cylinder.

[0100] The size of the reflective unit is 250 nm, the size ratio of the first reflective column to the groove is 4:1, the diameter of the first reflective column is 200 nm, and the height of the first reflective column is 200 nm.

[0101] The optical anti-counterfeiting super-GaN metasurface provided in this embodiment can also select and filter light of specific wavelengths, but the color of its output light can only change from blue to light blue, which is difficult for the human eye to distinguish. By comparing Example 2 and Example 3, it can be seen that by covering the light-reflecting structure with a photoresist layer, the vertical symmetry of the optical anti-counterfeiting GaN metasurface can be increased, thereby effectively expanding the bandwidth of the quasi-BIC mode, making the color change of the output light more obvious, and thus improving the anti-counterfeiting effect.

[0102] The optical anti-counterfeiting GaN metasurface provided by the present application selects the wavelength of the incident light by designing a light reflection structure with quasi-BIC characteristics to output outgoing light of a specific wavelength, and at the same time enhances or weakens the outgoing light of different wavelengths in combination with the dispersion effect of the light reflection structure. The anti-counterfeiting function can be achieved under sunlight without the need for specific lighting conditions and special optical materials, nor does it require the customization of specific patterns. The structure is simple, and the weight and volume of the structure are greatly reduced by realizing the light field control function in a quasi-two-dimensional plane at the sub-wavelength level. It has the advantages of extremely high customization, flexibility, ultra-thinness, lightness, high integration and efficient optical performance. At the same time, since the present application adopts a two-dimensional cylinder to design the light reflection structure, the human eye can observe the outgoing light whose color changes slowly with the outgoing angle in any direction. In addition, since the quality factor value of the quasi-BIC mode of the light reflection structure designed in the present application is high, the color saturation of the outgoing light is high, which is easier to observe with the naked eye, and has broad application prospects in the field of optical anti-counterfeiting.

[0103] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. An optical anti-counterfeiting GaN metasurface, characterized in that: include: basal layer; A light-reflecting structure, disposed on one surface of the substrate layer, is configured to generate a quasi-BIC mode to filter and screen incident light to output reflected light, and to disperse the reflected light, thereby outputting outgoing light with a wavelength that continuously changes within a set angle range; the set angle range is 5° to 25°, the wavelength range is 430nm to 540nm, and the outgoing light wavelength band is less than or equal to 10nm; In which, the light reflecting structure includes a plurality of first reflecting columns and a second reflecting column, the plurality of first reflecting columns are arranged in an array on one surface of the base layer, a groove is provided between two adjacent first reflecting columns, and the size ratio of the first reflecting column to the groove is 4:1; the second reflecting column is arranged between adjacent first reflecting columns, and the top of the second reflecting column contacts the bottom of the groove; the height of the first reflecting column is 160nm~200nm, and the height of the second reflecting column is less than the height of the first reflecting column.

2. The optical anti-counterfeiting GaN metasurface according to claim 1, characterized in that: Also includes: The matching layer is arranged on the surface of the light reflecting structure away from the base layer. The matching layer is provided with a protrusion matching the groove on the side close to the light reflecting structure, and the top of the protrusion contacts the top of the groove.

3. The optical anti-counterfeiting GaN metasurface according to claim 1, characterized in that: The material of the base layer is aluminum oxide or silicon dioxide; and / or The material of the light reflection structure is gallium nitride.

4. The optical anti-counterfeiting GaN metasurface according to claim 1, characterized in that: The diameter or side length of the first reflective column is 160 nm to 200 nm.

5. The optical anti-counterfeiting GaN metasurface according to claim 1, characterized in that: When the diameter or side length of the first reflective column is 160 nm, the height of the first reflective column is 160 nm, and the size of the groove is 40 nm, the set angle range is 5°~25°, and the wavelength variation range is 430 nm~530 nm.

6. The optical anti-counterfeiting GaN metasurface according to claim 1, characterized in that: When the diameter or side length of the first reflective column is 200 nm, the height of the first reflective column is 200 nm, and the size of the groove is 50 nm, the set angle range is 5°~15°, and the wavelength variation range is 500 nm~540 nm.

7. The optical anti-counterfeiting GaN metasurface according to claim 1, characterized in that: The first reflective column is a circular column, a square column or a regular polygonal column; and / or The second reflective column is a circular column, a square column or a regular polygonal column.

8. An optical anti-counterfeiting product, characterized in that: The optical anti-counterfeiting product comprises the optical anti-counterfeiting GaN metasurface according to any one of claims 1 to 7.

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