High-purity structural color device based on metasurface and color developing method

Abstract

The invention provides a high-purity structural color device based on a metasurface and a color developing method, and relates to the technical field of structural color metasurface, the structural color device is a double-layer nanoring array based on an all-dielectric metasurface, adopts an optical design based on Fabry-Perot interference and Mie resonance, and comprises a plurality of structural units, the structure unit comprises a vertical stacking double-layer circular ring structure formed by a tantalum pentoxide Ta2O5 functional layer and a silicon dioxide SiO2 top cover layer, and has sub-wavelength periodic two-dimensional arrangement; through the technical path of the invention, a structural color solution with high purity, wide color gamut and high reflection is provided by utilizing the wide band gap characteristic and high-quality manufacturing capability of Ta2O5. The application scenarios include but are not limited to high-end displays, optical sensors, information encryption and precision optical elements, and brand new possibility is provided for development of the next generation of photonics technology.

Description

Technical Field

[0001] This invention relates to the field of structural color metasurface technology, and in particular to a high-purity structural color device and color development method based on metasurface. Background Technology

[0002] Structural color is a type of color produced through the interference, scattering, or diffraction of light, which is fundamentally different from the mechanism by which traditional dyes or pigments rely on the selective absorption of light by molecules. Due to its unique photophysical mechanism, structural color possesses advantages such as high stability, colorfastness, and environmental friendliness, and has broad application prospects in fields such as anti-counterfeiting, biomedicine, printing, information display, and sensors. The colors exhibited by many organisms in nature (such as blue tits, metallic beetles, and peacock feathers) through micro- and nano-structures are based on this principle of selective spectral modulation. Inspired by this, researchers have developed various artificial structural color technologies, including diffraction grating structures, thin-film interference structures, and all-dielectric structural colors based on Mie resonance.

[0003] In recent years, with the advancement of nanofabrication technology, metasurface technology has provided new solutions for the design and optimization of structural colors. Metasurfaces are composed of subwavelength-scale artificial units, enabling precise control of the phase, amplitude, and polarization state of light. Compared with traditional optical devices, metasurface structural colors not only have higher color saturation but also achieve efficient spectral control at extremely thin device thicknesses. Researchers have developed various all-dielectric structural color schemes using high-refractive-index dielectric materials such as titanium dioxide (TiO2), silicon nitride (Si3N4), and silicon (Si).

[0004] However, existing all-dielectric structural color technologies still have significant limitations. While TiO2 can generate strong Mie resonances, its high refractive index easily excites higher-order modes, leading to reduced color monochromaticity and saturation. Furthermore, the etching process for these materials is complex and requires sophisticated equipment. Si, on the other hand, exhibits high absorption loss in the visible light band, limiting its performance in structural color applications. Structurally, existing technologies typically employ cylindrical nanostructures, but these have limitations in terms of color saturation and color gamut coverage. Summary of the Invention

[0005] In view of this, the present invention provides a high-purity structural color device and color display method based on metasurfaces. The high-purity structural color device of the present invention is a double-layer ring structure with SiO2 as the top layer and Ta2O5 as the main material. Through the double-layer stacked ring structure design, the SiO2 top layer is introduced to enhance the multi-mode matching between the upper and lower layers, and effectively suppresses sideband reflections in the non-resonant band, significantly improving the main peak intensity and color saturation. As a high refractive index medium material, Ta2O5 has a more suitable refractive index (n>2.1) than TiO2, which can suppress the excitation of higher-order modes while maintaining a strong Mie resonance, thereby improving the color purity and monochromaticity of the structural color. In addition, Ta2O5 exhibits extremely low absorption loss in the visible light range, enabling the device to achieve higher reflectivity, while also improving the brightness and saturation of the color. Compared with other common medium materials, Ta2O5 has a wider spectral transparency, with good transmittance in the ultraviolet to visible light range. This characteristic makes it not only suitable for structural color display, but also allows for applications in optical sensing, micro-nano photonics, and imaging technology. Meanwhile, Ta₂O₅ exhibits excellent environmental stability; even under high humidity and high temperature conditions, its optical properties remain stable, which is particularly important for optical components used for extended periods. Based on this, this invention utilizes the superior optical properties of Ta₂O₅, combined with a subwavelength-scale multilayer nanoring array design, to realize an ultrathin, high-color-purity, wide-gamut structural color generation device. By precisely controlling the geometric dimensions and periodic parameters of the nanorings, full color gamut modulation within the visible light range can be achieved. Simultaneously, the special geometric structure of the nanorings effectively suppresses higher-order diffraction effects, improving color stability. Compared to traditional dielectric metasurface structural color schemes, this invention provides a novel structural design approach that further enhances the device's color performance while optimizing manufacturing process feasibility, resulting in better compatibility and scalability in practical applications. This technology can be applied not only to high-resolution microdisplays and optical sensing but also widely to anti-counterfeiting labels, biometric detection, and novel photonic devices, offering new possibilities for future optical display technologies.

[0006] This invention provides the following technical solutions: On one hand, this invention provides a high-purity structural color device based on a metasurface. The structural color device is a double-layer nanoring array based on an all-dielectric metasurface, employing an optical design based on Fabry-Perot interference and Mie resonance. It includes several structural units, each comprising a vertically stacked double-layer ring structure consisting of a tantalum pentoxide (Ta2O5) functional layer and a silicon dioxide (SiO2) capping layer, exhibiting a subwavelength periodic two-dimensional arrangement. The Ta2O5 nanorings have an inner diameter of 30 nm - 100 nm, an outer diameter of 120 nm - 350 nm, a period range of 260 nm - 420 nm, a Ta2O5 functional layer height of 215 nm - 235 nm, and a SiO2 capping layer height of 80 nm - 120 nm.

[0007] Furthermore, in the double-layer ring structure, the lower layer is a Ta2O5 functional layer and the upper layer is a SiO2 capping layer. The two layers work together to construct a multi-polar resonance mode by adjusting their height and modal matching, so as to enhance the main reflection peak and suppress the side band reflection.

[0008] Furthermore, the full width at half maximum (FWHM) of the main reflection peak is less than 15 nm.

[0009] Furthermore, the total height of the structural unit is 315 nm; the thickness of the SiO2 capping layer is 100 nm.

[0010] In another aspect, the present invention also provides a structural color rendering method using the above-mentioned high-purity structural color device based on metasurface, characterized in that the structural color is continuously adjustable by precisely controlling the geometric parameters of the nanorings.

[0011] Furthermore, precise control of the nanoring geometry parameters enables continuous tunability of the structural color, including: S1. Select a representative combination of inner diameter, outer diameter and array period, and perform two-dimensional parametric scanning of ring height and dielectric layer thickness; the scanning range of ring height is set to 200 nm - 400 nm with a step size of 10 nm, and the scanning range of dielectric layer thickness is set to 10 nm - 200 nm with a step size of 10 nm. S2. For each set of parameters, the reflection spectrum is obtained using full-wave optical simulation, the peak position, peak intensity and FWHM are extracted, and the spectral characteristics of different combinations are compared and analyzed to select the best parameters with high peak and narrow FWHM. S3. After obtaining the initial optimal ring height and dielectric layer thickness, expand the scanning range to include the array period and inner / outer diameter parameters. Start scanning the inner diameter from 30 nm, with a maximum difference of 20 nm from the period and a step size of 10 nm. Initially, the outer diameter is set to the inner diameter plus 10 nm. The array period is set to 200 nm - 500 nm with a step size of 20 nm. During the actual scanning process, first fix the inner diameter and period, and perform a one-dimensional parametric scan of the outer diameter. Then, change the inner diameter and period values ​​and repeat the outer diameter scan multiple times to ensure that all colorimetric combinations are covered. S4. After completing the full-range scan, systematically organize and classify the data, paying attention to situations where the reflectance spectrum shows obvious peak jumps, significant peak increases, or sharp narrowing of bandwidth during parameter changes. S5. After identifying potential high-performance points, further local fine scanning is performed, reducing the step size to 2 nm–5 nm to capture the precise combination of parameters with optimal performance.

[0012] Furthermore, the optimal parameters are: ring height 315 nm, SiO2 dielectric layer thickness 100 nm; the optimal adjustment range is: inner diameter 30 nm - 100 nm, period 260 nm - 420 nm, when the period is 260 nm, the outer diameter can be adjusted in the range of 120 nm - 250 nm, and when the period is 420 nm, the outer diameter can be adjusted in the range of 250 nm - 350 nm.

[0013] Furthermore, by adjusting the range of period parameters, full color gamut coverage is achieved within the visible light range of 380 nm - 720 nm.

[0014] Advantages and positive effects of the present invention: The structural color device of this invention employs an optical design based on Fabry-Perot interference and Mie resonance. By precisely controlling the geometric parameters of the nanoring, the structural color can be continuously tunable. Through synergistic adjustment of the geometric parameter range, full color gamut coverage can be achieved within the visible light range (380 nm - 720 nm). The structural color exhibits high color purity, making it suitable for high-resolution optical displays, anti-counterfeiting labels, and information encryption applications. The device's typical reflectivity reaches 100%, offering higher optical efficiency compared to traditional structural color schemes. With a reflectance spectrum FWHM less than 15 nm, it possesses higher color contrast and monochromaticity compared to diffraction gratings or plasmon resonance structural colors. The ring resonance structure effectively suppresses higher-order mode excitation, improving color performance. Ta₂O₅ has a high refractive index (n>2.1), enhancing the Mie resonance effect and increasing the saturation of the structural color. It exhibits an extremely low extinction coefficient in the visible light band, resulting in higher optical efficiency and brightness. Even under high humidity and high temperature environments, the material maintains stable optical performance, making it suitable for long-term optical devices.

[0015] Meanwhile, the spectral response of the structural unit of this invention can be finely adjusted through independent control of geometric parameters (inner diameter, outer diameter, period, height, etc.), exhibiting high programmability. This feature not only allows users to customize target colors or spectral responses according to application requirements, but also adapts to complex patterns or multi-pixel array layouts, providing flexible configuration capabilities for multiple fields such as optical displays, security encryption, and intelligent sensing. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A comparison of radar images of all dielectric materials in the embodiments of the present invention; Figure 2 The following is a schematic diagram of the structural design evolution process in an embodiment of the present invention: (a) a single-layer Ta2O5 cylindrical structural unit; (b) a single-layer Ta2O5 ring structural unit; (c) a double-layer SiO2-Ta2O5 ring structural unit; (d) a CIE 1931 chromaticity diagram generated by a single-layer Ta2O5 cylindrical structural array; (e) a CIE 1931 chromaticity diagram generated by a single-layer Ta2O5 ring structural array; (f) a CIE 1931 chromaticity diagram generated by a double-layer SiO2-Ta2O5 ring structural array. Figure 3The images show the optical response of a single-layer Ta2O5 ring at different structural heights in the blue, green, and red bands in this embodiment of the invention; (a) blue band reflection image; (b) green band reflection image; (c) red band reflection image. Figure 4 The height of the SiO2 top cap layer in this embodiment of the invention ( h 1) Analysis of the impact of parametric scanning on reflectance spectrum and color performance; (a–c) Based on the optimal geometry of a single-layer circular ring ( h 1 = 0 nm), while keeping the size of the ring unchanged, for h 1. Reflectance spectra obtained by scanning in the range of 60 nm - 140 nm (step size 10 nm); (d–f) corresponding CIE 1931 chromaticity diagrams, showing different... h The trend of color coordinate changes under condition 1; Figure 5 In the embodiments of the present invention, the inner diameter ( d ), outer diameter ( D ) and cycle ( P The effect of ) on the structural reflectance spectrum; Figure 6 The following are the reflection spectra of three different structural units in the embodiments of the present invention; (a–c) are the reflection spectra of Ta2O5 cylindrical structure, single-layer Ta2O5 ring structure and double-layer SiO2-Ta2O5 ring structure under different geometric parameters, respectively. Figure 7 The following is a color performance analysis of three different structural units in the embodiments of the present invention; (a–c) are the color saturation, hue and gamut distribution analysis of the three structures in the visible light range, respectively; Figure 8 This is a comparison of the color gamut coverage in the embodiments of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] In this embodiment, a high-purity structural color device based on a metasurface is disclosed. The structural color device is a bilayer nanoring array based on an all-dielectric metasurface, comprising several structural units. Each structural unit comprises a vertically stacked bilayer ring structure consisting of a tantalum pentoxide (Ta2O5) functional layer and a silicon dioxide (SiO2) capping layer, exhibiting a subwavelength periodic two-dimensional arrangement. The Ta2O5 nanorings have an inner diameter of 30 nm - 100 nm, an outer diameter of 120 nm - 350 nm, a period range of 260 nm - 420 nm, a Ta2O5 functional layer height of 215 nm - 235 nm, and a SiO2 capping layer height of 80 nm - 120 nm.

[0021] To verify the performance of the structured color device in the above embodiments, the following analysis and explanation will focus on the material, structure, and dimensions of the structured color device: (1) Materials: Taking into account optical control capabilities, loss management, material stability, and process feasibility, Ta2O5 was ultimately selected as the core material for the all-dielectric metasurface structural color design in this embodiment. This material exhibits balanced performance across multiple dimensions and is particularly suitable for constructing high-saturation, low-loss, UV-Vis compatible all-dielectric structural color devices.

[0022] In all-dielectric metasurface design, the optical properties of the materials largely determine the device's color performance, loss control, and fabrication feasibility. To achieve high saturation, low loss, and wide color gamut structural color modulation, the performance of typical dielectric materials such as Ta2O5, TiO2, Si, Al2O3, SiO2, and Si3N4 was compared and analyzed across multiple performance dimensions. The results are as follows: Figure 1 The radar chart shown is shown below.

[0023] First, from the refractive index ( n From this perspective, Si has the highest... nValues ​​(3.5 - 4.0) are favorable for exciting strong Mie resonances, but their absorption loss in the visible light range is significant. k The non-zero refractive index often results in impure colors and insufficient brightness in structural color design. In contrast, both Ta2O5 and TiO2 have higher refractive indices (2.1 - 2.7) and lower extinction coefficients. k With a loss of approximately zero, it possesses both strong optical control capabilities and low loss characteristics, thus becoming the mainstream material in current all-dielectric structural color research.

[0024] In terms of bandgap width, Ta₂O₅, Al₂O₃, and SiO₂ all exhibit good ultraviolet transparency, with bandgaps of approximately 4.0 eV, 5.0 eV, and 9.0 eV, respectively, which are superior to TiO₂ and Si. This is beneficial for the application of devices in a wider wavelength range, especially from ultraviolet to visible light. In particular, Ta₂O₅ combines high refractive index with wide bandgap characteristics, and has also been practically applied in low thermal noise optical systems such as LIGO mirrors, verifying its low absorption and high stability characteristics.

[0025] In terms of fabrication processes and CMOS compatibility, materials such as Si, Al2O3, and SiO2 are widely used in existing micro-nano processes, demonstrating high process maturity. While TiO2 possesses excellent optical properties, its etching is challenging and requires sophisticated processing equipment. In contrast, Ta2O5 exhibits good sputtering deposition compatibility and can be used to fabricate high aspect ratio structures via plasma etching, balancing processability and performance.

[0026] In this embodiment, the Ta2O5 and SiO2 materials used are highly compatible with current mainstream micro-nano fabrication technologies (such as magnetron sputtering, plasma etching, electron beam lithography, etc.). The processes are mature and the equipment is widely available, enabling low-cost and reproducible manufacturing of structural color devices on large-area planar substrates. This has good engineering prospects and industrial transformation value.

[0027] (2) Structural aspects: For a single-layer Ta₂O₅ cylindrical structure, although color modulation was achieved by adjusting the cylinder height and diameter, but... Figure 2 (a) shows that the color saturation in the blue region is clearly insufficient.

[0028] In this embodiment, the cylinder is modified into a single-layer Ta2O5 nanoring structure. Figure 2 (b) The ring structure, due to the additional degrees of freedom provided by its adjustable inner diameter, can effectively suppress non-ideal higher-order modes and improve monochromaticity and color purity. The results show that the nanorings can significantly expand the blue color gamut ( Figure 2 (e) validates the potential of toroidal geometry in the field of high-saturation structural colors.

[0029] However, single-layer rings still have limitations under the requirements of high saturation and wide color gamut. To further improve the purity and brightness of structural colors, this embodiment proposes a double-layer stacked nanoring design: a SiO2 capping layer is introduced above the Ta2O5 main functional layer to form a double-layer ring metasurface. Figure 2 (c)). This design utilizes multi-mode matching between upper and lower layers to achieve effective mode suppression in the non-resonant band, thereby significantly improving color purity and brightness, and ultimately obtaining higher quality structural colors in the visible light range. Figure 2 (f)).

[0030] (3) Size: To optimize the bilayer structure, the total height of the nanounits was first determined, followed by the heights of the SiO2 capping layer and the Ta2O5 ring main functional layer. Based on parametric scanning of the single-layer Ta2O5 ring, structural combinations capable of producing red, green, and blue colors were selected. Considering the possibility of structural collapse or height deviation during actual fabrication, a parametric scan was performed on the structure with a height range of 240 nm to 340 nm and a step size of 5 nm. The results are as follows. Figure 3 As shown, Figure 3 (a) In the blue light band image, the reflection intensity at around 315 nm exhibits the advantages of narrow FWHM and high reflectivity. Figure 3 The green and red light bands in (b) and (c) show high reflection peaks with height, but these peaks are wider than those in the blue light band. The results indicate that at a height of 315 nm, the structure exhibits excellent optical response across all three primary color bands, demonstrating that this height achieves an optimal balance in color control. Therefore, in this embodiment, 315 nm was ultimately determined as the height constraint for all subsequent structural designs to ensure compatibility with multicolor responses and the feasibility of the manufacturing process.

[0031] Next, a parametric scan was performed on the SiO2 capping layer to select the optimal height. The widest color gamut was achieved using a single-layer Ta2O5 ring. Figure 4 middle h Based on the optimal geometric parameters (1 = 0 nm), keeping the annular size constant, the annular size was adjusted in 10 nm steps within the range of 60 nm - 140 nm. h 1. Perform a scan, and the results are as follows: Figure 4 As shown. Figure 4 The reflectance spectra of (a), (b), and (c) indicate that, with h As 1 increases, background reflection outside the main peak first decreases and then increases again. h When 1 = 100 nm, background reflection drops to almost zero, corresponding to the CIE 1931 color coordinates. Figure 4 (e) and (f) are closest to the color gamut boundary without sacrificing peak intensity. Although Figure 4 (d)h 1 = 140nm is closest to the boundary, but compared to Figure 4 The reflection spectrum in (a) exhibits strong background reflection at short wavelengths, which may lead to a decrease in color quality during subsequent scans. Considering peak intensity, background suppression, and color gamut coverage, the final SiO2 capping layer thickness was selected. h 1 = 100 nm, as the optimal design parameter, laid the foundation for subsequent multi-polar coupling and color quality improvement.

[0032] In another embodiment, a structural color rendering method using the above-mentioned high-purity structural color device based on metasurfaces achieves continuous and adjustable structural color by precisely controlling the geometric parameters of nanorings.

[0033] The geometric parameters include ring height, dielectric layer thickness, ring outer diameter, ring inner diameter, and array period. By jointly controlling these geometric parameters, the brightness, saturation, and bandwidth of the structural color are comprehensively optimized, achieving full color gamut coverage within the visible light range of 380nm-720nm.

[0034] Among them, the three key geometric parameters of the nanoring—inner diameter, outer diameter, and period—all have a certain influence on the structural color. By adjusting these parameters one by one using the controlled variable method and calculating the spectral reflectance, the influence of different parameters on the structural color was analyzed in depth. The focus was on examining the FWHM of the main reflection peak and its energy distribution throughout the entire reflection spectrum to determine the modulating effect of different geometric parameters on the resonance mode.

[0035] The influence of the three key geometric parameters of the nanoring—inner diameter, outer diameter, and period—on the structural color is as follows: (A) Influence of inner diameter on structural color. Through multiple simulation analyses, it was found that nanorings with the same outer diameter and period exhibit a consistent trend under different inner diameter parameters. Therefore, taking an outer diameter of 250 nm and a period of 300 nm as an example, under the condition of fixing the outer diameter and period, the inner diameter was adjusted within the range of 30 nm - 100 nm, and simulation was performed with a step size of 5 nm. Figure 5 The results shown in (a) indicate that as the inner diameter increases, the center wavelength of the main reflection peak gradually blue-shifts, meaning the resonant wavelength shifts towards shorter wavelengths. Simultaneously, the FWHM remains below 15 nm and gradually decreases with increasing inner diameter. d At 100 nm, it has high reflectivity and a relatively narrow FWHM, which suggests that a larger inner diameter helps to improve color purity and color contrast.

[0036] (B) The effect of outer diameter on structural color. Scanning the inner diameter reveals that... dAt an inner diameter of 100 nm, high reflectivity and a narrow field-wide reflection peak (FWHM) are observed. Therefore, with a fixed inner diameter of 100 nm and a period of 300 nm, simulations were performed with the outer diameter adjusted between 240 nm and 255 nm in 5 nm increments. The results are shown in Figure 5(b). As the outer diameter increases, the center wavelength of the main reflection peak undergoes a slight redshift, meaning the resonant wavelength shifts towards longer wavelengths. Simultaneously, the FWHM remains below 15 nm. This phenomenon indicates that changes in the outer diameter not only affect the position of the resonant wavelength but also influence the spectral width of the reflection peak, potentially affecting color saturation and contrast.

[0037] (C) The effect of periodicity on structural color. Figure 5 The results shown in (c) indicate that as the period increases, the resonant wavelength gradually redshifts, meaning the main reflection peak shifts towards longer wavelengths, while the hue shifts towards warmer regions. This trend suggests that a larger period parameter can effectively control the spectral distribution of the structural color, causing the color to evolve from cool to warm tones. Simultaneously, the reflectance spectrum shows that the FWHM remains within a narrow range throughout the entire period control range, indicating that the resonant mode possesses a high quality factor. This relatively narrow FWHM is beneficial for improving color purity and can be further compressed in subsequent designs to achieve highly saturated structural colors.

[0038] This embodiment verifies the influence of various parameters on the structural color representation. However, it also shows... Figure 5 The reflectance spectrum shows slight brightness jumps or breaks in the middle of the main reflection band, which may affect the coupling degree between different modes within the structure, and thus affect the shape, contrast, and color saturation of the reflection peak. Therefore, although adjusting a single parameter can achieve color changes within a certain range, its control capability is limited, making it difficult to achieve high-quality colors. Based on this, this invention proposes a multi-parameter synergistic optimization strategy. By jointly controlling geometric parameters such as ring height, dielectric layer thickness, ring outer diameter, ring inner diameter, and array period in combination with the material refractive index, the brightness, saturation, and bandwidth of the structural color are comprehensively optimized.

[0039] In specific implementation, the multi-parameter collaborative optimization strategy includes: S1. Select a representative combination of inner diameter, outer diameter and array period, and perform a two-dimensional parametric scan of the ring height and dielectric layer thickness. The scanning range for ring height was set to 200 nm - 400 nm with a step size of 10 nm, and the scanning range for dielectric layer thickness was set to 10 nm - 200 nm with a step size of 10 nm.

[0040] S2. For each set of parameters, the reflection spectrum is obtained using full-wave optical simulation. The peak position, peak intensity and FWHM are extracted, and the spectral characteristics of different combinations are compared and analyzed to select the best parameters with high peak and narrow FWHM.

[0041] The optimal parameters are a ring height of 315 nm and a SiO2 dielectric layer thickness of 100 nm.

[0042] S3. After obtaining the initial optimal ring height and dielectric layer thickness, expand the scanning range to include array period and inner and outer diameter parameters; The inner diameter is scanned starting from 30 nm, with a maximum difference of 20 nm from the period, and a step size of 10 nm. The outer diameter is initially set to the inner diameter plus 10 nm, and the array period is set to 200 nm - 500 nm with a step size of 20 nm.

[0043] In the specific scanning process, the inner diameter and period are fixed first, and a one-dimensional parametric scan of the outer diameter is performed; then the inner diameter and period values ​​are changed, and the outer diameter scan is repeated multiple times to ensure that all possible color combinations are covered.

[0044] S4. After completing the full-range scan, systematically organize and classify the data, paying particular attention to situations where the reflectance spectrum shows obvious peak jumps, significant peak increases, or sharp narrowing of bandwidth during parameter changes. These usually correspond to changes in structural resonance modes or optimization of coupling states.

[0045] The optimal adjustment range for the three parameters was finally determined to be an inner diameter of 30 nm - 100 nm and a period of 260 nm - 420 nm. Since the three parameters need to be matched, the size of the inner diameter and the period determines the adjustment range of the outer diameter. Therefore, when the period is the smallest at 260 nm, the outer diameter is 120 nm - 250 nm, and when the period is the largest at 420 nm, the adjustment range of the outer diameter is 250 nm - 350 nm.

[0046] S5. After identifying potential high-performance points, further local fine scanning is performed, reducing the step size to 2 nm-5 nm to capture the precise parameter combination with optimal performance.

[0047] At the same time, the variation patterns of different geometric parameters and reflectance spectral performance are summarized and generalized to form empirical rules that can guide subsequent designs.

[0048] This strategy enables efficient screening and determination of optimal geometric parameters within a large parameter space, achieving comprehensive optimization of structural colors in terms of brightness, saturation, and bandwidth.

[0049] like Figure 6As shown, it illustrates the performance of three all-dielectric nanostructure units (single-layer Ta2O5 cylinder, single-layer Ta2O5 ring, and double-layer SiO2-Ta2O5 ring structure) in terms of color saturation and color gamut coverage.

[0050] Reflectance spectrum ( Figure 6 (a-c) reveals the spectral basis of structural color variations. The cylindrical structure exhibits significant high-order multimode interference, resulting in a large bandwidth of the reflection peak and weakening color purity. The ring structure, through modal volume modulation and asymmetry enhancement, significantly suppresses background reflection and achieves narrowband resonance. The double-layer ring structure, through mode matching between the upper and lower layers and non-resonant mode suppression, further weakens the sidebands while increasing the intensity of the main peak, ultimately forming a full-spectrum structural color with higher monochromaticity and stronger brightness, with a reflection peak intensity reaching 100% and an FWHM below 15 nm.

[0051] like Figure 7 As shown, it illustrates the color performance analysis results (color saturation, hue, and gamut distribution in the visible light range) for three different structural units.

[0052] CIE 1931 chromaticity diagram projection ( Figure 7 (a - c) visually demonstrates the significant color gamut expansion trend resulting from the evolution of the structural design. The initial cylindrical structure's color points were mainly concentrated in the central region of the CIE 1931 chromaticity diagram, exhibiting low color saturation. After optimization into a ring structure, the introduction of the inner diameter increased geometric freedom, causing the structural color points to move closer to the chromaticity diagram boundary, especially expanding significantly in the blue-green region. Further introduction of a double-layer stacked design resulted in a more uniform distribution of color points across the entire visible light range, achieving a color gamut coverage of 178% of sRGB and 132% of Adobe RGB. Figure 8 As shown, both saturation and brightness were improved from 80% to over 90%, verifying the effectiveness of the multilayer structure in enhancing structural color performance.

[0053] The present invention is compared with various nanostructures in the prior art, and the results are shown in Table 1. The analysis results show that the structural color device proposed in this invention exhibits superiority in several key optical performance indicators: In terms of reflectivity, this invention achieves 100% high reflectivity, which is far superior to designs such as the 76% reflectivity of a cylindrical structure made of Si material or the approximately 64% reflectivity of a trapezoidal structure made of TiO2.

[0054] In terms of FWHM (Frequency-Wide-Hyper-Meaning), this invention exhibits an extremely narrow bandwidth, less than 15 nm, significantly better than the typical 30 nm-50 nm range, such as 43 nm for Si conical structures and only less than 30 nm for TiO2-TiN-TiO2 structures. This extremely narrow bandwidth not only helps improve color purity but also has significant implications for the application of high-resolution optical filters.

[0055] In terms of color performance, the structural color device of the present invention achieves an ultra-wide color gamut coverage of 178% sRGB and 132% AdobeRGB in the visible light range, which is significantly better than the Si-SiO2 scheme with the same nanoring structure (115% sRGB) and also better than various designs including traditional columnar structures.

[0056] It should also be noted that in existing designs using Si-SiO2 nanorings as metasurface structural units, the SiO2 layer in the middle has no significant effect on the reflection spectrum. However, in the structural color device of this invention, SiO2 serves as a capping layer and a refractive index matching layer, which suppresses sideband reflections at non-resonant locations, while concentrating energy more in the main reflection region, resulting in higher structural color saturation.

[0057] As can be seen from the above indicators, the structural color device of the present invention achieves a good balance between high reflectivity, narrow bandwidth and wide color gamut, fully demonstrating its great potential in application fields such as high-performance display devices and color selective filters.

[0058] Table 1

[0059] This invention, utilizing the wide bandgap characteristics and high-quality manufacturing capabilities of Ta2O5, provides a structural color solution that combines high purity, wide color gamut, and high reflectivity. Its applications include, but are not limited to, high-end displays, optical sensors, information encryption, and precision optical components, offering entirely new possibilities for the development of next-generation photonics technologies.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-purity structural color device based on a metasurface, characterized in that, The structured color device is a bilayer nanoring array based on an all-dielectric metasurface. It adopts an optical design based on Fabry-Perot interference and Mie resonance, and includes several structural units. Each structural unit consists of a vertically stacked bilayer ring structure composed of a tantalum pentoxide (Ta2O5) functional layer and a silicon dioxide (SiO2) capping layer, with a subwavelength periodic two-dimensional arrangement. The Ta2O5 nanorings have an inner diameter of 30 nm - 100 nm, an outer diameter of 120 nm - 350 nm, a period of 260 nm - 420 nm, a Ta2O5 functional layer height of 215 nm - 235 nm, and a SiO2 capping layer height of 80 nm - 120 nm.

2. The high-purity structural color device based on a metasurface according to claim 1, characterized in that, In the double-layer ring structure, the lower layer is a Ta2O5 functional layer and the upper layer is a SiO2 capping layer. The two layers work together to construct a multipolar resonance mode by adjusting their height and modal matching, so as to enhance the main reflection peak and suppress the sideband reflection.

3. A high-purity structural color device based on a metasurface according to claim 2, characterized in that, The total height of the structural unit is 315 nm; the thickness of the SiO2 capping layer is 100 nm.

4. A structural color development method using a high-purity structural color device based on a metasurface as described in any one of claims 1-3, characterized in that, By precisely controlling the geometric parameters of the nanorings, the structural color can be continuously adjusted.

5. The structural color rendering method according to claim 4, characterized in that, Precisely controlling the geometric parameters of nanorings to achieve continuously tunable structural colors includes: S1. Select a representative combination of inner diameter, outer diameter and array period, and perform two-dimensional parametric scanning of ring height and dielectric layer thickness; the scanning range of ring height is set to 200 nm - 400 nm with a step size of 10 nm, and the scanning range of dielectric layer thickness is set to 10 nm - 200 nm with a step size of 10 nm. S2. For each set of parameters, the reflection spectrum is obtained using full-wave optical simulation. The peak position, peak intensity and half-width are extracted, and the spectral characteristics of different combinations are compared and analyzed to select the best parameters with high peak and narrow half-width. S3. After obtaining the initial optimal ring height and dielectric layer thickness, expand the scanning range to include the array period and inner and outer diameter parameters; start scanning the inner diameter from 30 nm, with a maximum difference of 20 nm from the period and a step size of 10 nm; initially set the outer diameter to the inner diameter plus 10 nm; set the array period to 200 nm - 500 nm with a step size of 20 nm; during the actual scanning process, first fix the inner diameter and period, and perform a one-dimensional parametric scan of the outer diameter; then change the inner diameter and period values, and repeat the outer diameter scan multiple times to ensure that all colorimetric combinations are covered; S4. After completing the full-range scan, systematically organize and classify the data, paying attention to situations where the reflectance spectrum shows obvious peak jumps, significant peak increases, or sharp narrowing of bandwidth during parameter changes. S5. After identifying potential high-performance points, further local fine-tuning scanning is performed, reducing the step size to 2 nm - 5 nm to capture the precise parameter combination with optimal performance.

6. The structural color rendering method according to claim 5, characterized in that, The optimal parameters are: ring height 315 nm, SiO2 dielectric layer thickness 100 nm; the optimal adjustment range is: inner diameter 30 nm - 100 nm, period 260 nm - 420 nm, when the period is 260 nm, the outer diameter can be adjusted in the range of 120 nm - 250 nm, and when the period is 420 nm, the outer diameter can be adjusted in the range of 250 nm - 350 nm.

7. The structural color rendering method according to claim 5, characterized in that, By adjusting the range of period parameters, full color gamut coverage can be achieved within the visible light range of 380 nm - 720 nm.

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