An electro-reconfigurable reflective metasurface switching device

Abstract

This invention discloses an electro-reconfigurable reflective metasurface switching device, comprising multiple pixel units arranged in a horizontal row and column periodically. The minimum period of a single pixel unit is 2×2, and each period consists of four sub-pixel units (RGGB). Each sub-pixel unit includes a functional layer disposed above a substrate. The functional layer consists of two pairs of cylinders with different radii, and the cylinders have a sandwich structure or a two-layer stacked structure. By adjusting the radii of the cylinders, the thickness of each layer in the cylindrical structure, and the period of the metasurface switching device, stable color display in the visible light band can be achieved. By controlling the phase transition state of the phase change material layer, the reflectivity of the metasurface switching device can be changed, achieving in-situ color brightness adjustment. This invention improves the refresh rate while also effectively enhancing optical performance and refresh lifespan.

Description

Technical Field

[0001] This invention belongs to the field of visible light display and light field modulation technology, and more specifically, relates to an electro-reconfigurable reflective metasurface switching device. Background Technology

[0002] E-ink displays are a type of reflective display that closely resembles the effect of natural paper, reducing reading fatigue and making them popular in eye-care products. The core performance of an e-ink display is directly related to the performance of the ink particles, but currently, e-ink displays fall short of user needs in terms of display quality, speed, refresh rate, and other fundamental aspects of the user experience.

[0003] Current electronic ink systems typically consist of a mixture of black and white particles in an electrophoretic solution, which are then encapsulated to improve reliability. Because the movement mechanism of particles in the electrophoretic solution is highly complex, the refresh rate is affected by factors such as particle size, density, charge, and concentration. Therefore, improving the refresh rate while simultaneously enhancing optical performance and refresh lifespan is a pressing issue that needs to be addressed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an electro-reconfigurable reflective metasurface switching device that can improve the refresh rate while also effectively improving the optical effect and refresh life.

[0005] To achieve the above objectives, the present invention provides an electro-reconfigurable reflective metasurface switching device for displaying stable colors in the visible light band and adjusting color brightness in situ. It includes multiple pixel units arranged in a horizontal row-column periodic pattern, with a minimum period of 2×2 for each pixel unit. Each period consists of four sub-pixel units: RGGB. Each sub-pixel unit includes a functional layer disposed above a substrate. The functional layer consists of two pairs of cylinders with different radii, arranged in a matrix. Two cylinders on the same diagonal of the matrix have the same radius. The cylinders have a sandwich structure or a two-layer stacked structure. The sandwich structure includes upper and lower dielectric layers and an intermediate phase change material layer. The two-layer stacked structure includes an upper dielectric layer and a lower phase change material layer.

[0006] The display of stable colors in the visible light band is achieved by modulating the resonant positions of the electric and magnetic dipoles of the metasurface switching device to achieve a high reflection peak at the resonant wavelength. The resonance occurs when ε = (4-μ) / (2μ+1), where ε and μ correspond to the dielectric constant and relative permeability of the metasurface switching device, respectively. This resonant wavelength is achieved by adjusting the radii of the two pairs of cylinders, the thickness of each layer in the cylindrical structure, and the period of the metasurface switching device. The phase change material layer includes both amorphous and crystalline phases. The adjustment of the in-situ color brightness is achieved by controlling the phase change state of the phase change material layer to change the reflectivity of the metasurface switching device.

[0007] In one embodiment, the phase change material layer is made of antimony sulfide.

[0008] In one embodiment, the metasurface switching device displays colors including red, green, blue, yellow, magenta, and cyan in the visible light band.

[0009] In one embodiment, when the cylindrical structure is a sandwich structure, in a single sub-pixel unit, the thickness of the substrate is 50 nm, the thickness of the phase change material layer in the functional layer is 10–100 nm, the thickness of the dielectric layer in the functional layer is 10–150 nm, the radii of the cylinders on different diagonals are 80–150 nm and 40–70 nm, respectively, and the period of the metasurface switching device is 300–1500 nm.

[0010] In one embodiment, when the cylindrical structure is a two-layer stacked structure, the substrate includes a substrate and a conductive layer disposed on the substrate, and both the conductive layer material and the dielectric layer material are titanium dioxide.

[0011] In one embodiment, in a single sub-pixel unit, when the thickness of the substrate is 50 nm, the thickness of the phase change material layer is 60 nm, the thickness of the two layers of titanium dioxide material is 30 nm, and the radii of the two pairs of cylinders are 100 nm and 50 nm respectively, color control from green to yellow and then to red can be achieved by gradually increasing the period of the metasurface switching device from 520 nm to 680 nm.

[0012] In one embodiment, when the cylindrical structure is a sandwich structure, the substrate is made of silica or indium tin oxide.

[0013] In one embodiment, when the cylindrical structure is a sandwich structure, the fabrication method of the metasurface switching device includes the following steps:

[0014] The pattern of the functional layer is transferred onto the substrate using photolithography or nanoimprint lithography.

[0015] A first dielectric layer is grown on a substrate using a thin film deposition method;

[0016] A phase change material layer is grown on a substrate using thin film deposition.

[0017] A second dielectric layer is grown on a substrate using thin film deposition.

[0018] The photoresist is removed using a stripping process, leaving a cylindrical functional layer.

[0019] By connecting an external voltage source to a heating plate on the substrate, a metasurface switching device is obtained.

[0020] In one embodiment, when the cylindrical structure is a two-layer stacked structure, the fabrication method of the metasurface switching device includes the following steps:

[0021] A conductive layer is grown on a substrate using thin film deposition.

[0022] The pattern of the functional layer is transferred onto the substrate using photolithography or nanoimprint lithography.

[0023] A phase change material layer is grown on a substrate using thin film deposition.

[0024] A dielectric layer is grown on a substrate using thin film deposition.

[0025] The photoresist is removed using a stripping process, leaving a cylindrical functional layer.

[0026] By connecting an external voltage source to a conductive layer on a substrate, a metasurface switching device is obtained.

[0027] The electro-reconfigurable reflective metasurface switching device provided by the present invention has the following effects: (1) The functional layer in the sub-pixel unit is composed of two pairs of cylinders with different radii, arranged in a centrally symmetrical manner, and is not sensitive to polarization. The positions of the electric dipole and the magnetic dipole can be controlled relatively independently and precisely using the cylinders of different sizes, so that the distance between the two resonances is closer, thereby making the half-width at half-maximum of the reflection peak smaller, the color saturation higher, the reflectivity greater, and the color gamut wider. Moreover, the cylindrical structure uses phase change material. When the phase change material becomes crystalline, it can destroy the magnetic dipole resonance of the metasurface, thereby making the reflection peak of the off state disappear and the reflectivity extremely low, thus greatly improving the reflectivity, on / off ratio, saturation and color gamut of the device, thereby effectively improving the optical effect of the reflective display; (2) The functional layer uses phase change material. Since the phase change material switches between the amorphous and crystalline states very quickly, the minimum time interval of the amorphization process is about 200 ns, and the crystallization process is 500 ns. Moreover, the phase change material can switch between the amorphous and crystalline states in electrical devices up to 10 9 This effectively improves the refresh rate and lifespan of the metasurface. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the electro-reconfigurable reflective metasurface switching device provided by the present invention;

[0029] Figure 2 This is another structural schematic diagram of the electro-reconfigurable reflective metasurface switching device provided by the present invention;

[0030] Figure 3 The curves of refractive index and extinction coefficient of the phase change material Sb2S3 provided by this invention in the visible light band are shown.

[0031] Figure 4 These are the reflectivity curves of the reflective metasurface switching device in the on and off states provided in Embodiment 1 of the present invention;

[0032] Figure 5 This refers to the positions of the on-state and off-state colors of the reflective metasurface switching device provided in Embodiment 1 of the present invention in the chromaticity diagram;

[0033] Figure 6 These are the reflectivity curves of the reflective metasurface switching device in the on and off states provided in Embodiment 2 of the present invention;

[0034] Figure 7 This refers to the positions of the on-state and off-state colors of the reflective metasurface switching device provided in Embodiment 2 of the present invention in the chromaticity diagram;

[0035] Figure 8 These are the reflectivity curves of the reflective metasurface switching device in the on and off states provided in Embodiment 3 of the present invention;

[0036] Figure 9 This refers to the positions of the on-state and off-state colors of the reflective metasurface switching device provided in Embodiment 3 of the present invention in the chromaticity diagram;

[0037] Figure 10 The position of the color of the reflective metasurface switching device provided in Embodiment 4 of the present invention under periodic variation in the chromaticity diagram;

[0038] Figure 11 This is a process flow for the reflective metasurface switching device provided by the present invention;

[0039] Figure 12 This is another process flow for the reflective metasurface switching device provided by the present invention;

[0040] Figure 13 This is the arrangement of pixels and RGGB color system in Embodiment 5 of the present invention;

[0041] Figure 14 This is a color gamut diagram of the RGGB color system in Embodiment 5 of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] To address the problems of low refresh rate, poor optical effect, and short refresh life in traditional displays, this invention provides an electro-reconfigurable reflective metasurface switching device. This reflective metasurface switching device includes multiple pixel units arranged in horizontal rows and columns periodically. The minimum period of a single pixel unit is 2×2. This period consists of four sub-pixel units: RGGB. Full-color display can be achieved by controlling the brightness combination of individual sub-pixel units, thereby improving the display color gamut.

[0044] Each sub-pixel unit includes a substrate and a functional layer arranged from bottom to top. The functional layer consists of two pairs of cylinders with different radii, such as... Figure 1 and Figure 2 As shown, the four cylinders are arranged in a matrix. The two cylinders on the same diagonal of the matrix have the same radius, while the cylinders on different diagonals of the matrix have different radii.

[0045] Specifically, the cylindrical structure provided in this embodiment can be a sandwich structure or a two-layer stacked structure. When it is a sandwich structure, it includes upper and lower dielectric layers and an intermediate phase change material layer, with the substrate material being quartz silicon dioxide or indium tin oxide. When it is a two-layer stacked structure, it includes an upper dielectric layer and a lower phase change material layer, with the substrate including a substrate and a conductive layer disposed on the substrate. Specifically, the cylindrical structure provided in this embodiment can be selected according to the application method of voltage pulse regulation of the phase change material. That is, when using a sandwich structure, an external voltage source can be connected to a heating plate on the substrate; when using a two-layer stacked structure, an external voltage source can be connected to the conductive layer on the substrate.

[0046] In this embodiment, the functional layer includes a phase change material layer. The phase change material layer can undergo a phase transition by applying voltage pulses, and the phase transition state includes both amorphous and crystalline states. When the phase change material in the functional layer undergoes a phase transition, the reflectivity of the metasurface switching device changes accordingly, enabling in-situ adjustment of color brightness and ultimately achieving color grayscale adjustment. That is to say, when the phase change material in the functional layer is in an amorphous state, the metasurface switching device provided in this embodiment can reflect colors in the visible light band, displaying different colors, thus achieving the on state; when the phase change material in the functional layer undergoes a phase transition from amorphous to crystalline, the reflectivity of the device changes, and the overall reflectivity becomes very low, thus achieving the off state.

[0047] Because phase change materials undergo phase transitions very quickly, switching can be achieved within microseconds, enabling the color refresh rate of the metasurface switching device provided in this embodiment to be above several kilohertz, or even close to megahertz, which can greatly improve the device's refresh rate. Furthermore, the phase transition of phase change materials is non-volatile, maintaining the current state until the next stimulus arrives, and consuming no energy in steady state, thus giving the device the characteristics of non-volatility and low power consumption.

[0048] Furthermore, research has revealed that when the dielectric constant ε and relative permeability μ of a metasurface switching device are equal, its backscattering is zero, making it suitable for manufacturing anti-reflective coatings and absorbing coatings. When the dielectric constant ε and relative permeability μ of a metasurface switching device satisfy ε = (4-μ) / (2μ+1), the contributions of the electric dipole and magnetic dipole (i.e., a state generated by the metasurface switching device under electromagnetic wave incidence) to the metasurface scattering cancel each other out, resulting in minimal forward scattering, which can be used to manufacture reflective coatings.

[0049] Based on the above research and analysis, the metasurface switching device provided in this embodiment can achieve the following by adjusting the radius of the large and small cylinders, the thickness of each layer in the cylindrical structure, and the period of the metasurface switching device: the dielectric constant ε and relative permeability μ of the device can satisfy ε=(4-μ) / (2μ+1). This allows the electric dipole and magnetic dipole resonance of the device to occur at the designed position, resulting in a high reflection peak on the metasurface at a specific wavelength. Consequently, the wavelength of the electric dipole and magnetic dipole resonance of the device appears at the high reflection peak, thus displaying a stable color.

[0050] In this embodiment, a cylindrical metasurface made of dielectric material generates electric and magnetic dipole resonances. The wavelength of this resonance is related to the cylinder's thickness, radius, period, and the material's refractive index. Once manufactured, the metasurface's optical properties are fixed. In this embodiment, a phase change material with dynamically tunable refractive index is inserted into the dielectric during the cylindrical structure design. By changing the state of the phase change material, the dynamic tuning of the metasurface's optical properties can be achieved. Furthermore, during the optical design phase, changing the radius of a cylinder with a uniform radius simultaneously affects both the magnetic and electric dipoles. This embodiment designs the cylinder with two different radii, allowing for relatively independent control of the resonant wavelengths of the electric and magnetic dipoles to achieve specific color reflections.

[0051] In this embodiment, the radii of the large and small cylinders have a significant impact on the position of the reflection peaks. Increasing the radius shifts the reflection peaks towards longer wavelengths, while decreasing the radius shifts them towards shorter wavelengths. Increasing the device period smoothly shifts the reflection peaks towards longer wavelengths, while decreasing the period smoothly shifts them towards shorter wavelengths. The thickness of each layer in the cylindrical structure affects the intensity of the magnetic and electric dipole resonances and the spacing between the reflection peaks generated by these resonances. The thickness of the phase change material affects the device's controllability; greater thickness results in stronger controllability, while smaller thickness results in weaker controllability. The structure of the large and small cylinders enhances the metasurface's controllability over magnetic and electric dipoles. When the phase change material changes from an amorphous state to a crystalline state, the increased refractive index and extinction coefficient increase the absorptivity and disrupt the electric and magnetic dipole resonances, effectively shutting off the reflection peaks and achieving a switching function.

[0052] The electro-reconfigurable reflective metasurface switching device provided in this embodiment has the following effects: (1) The functional layer in the sub-pixel unit is composed of two pairs of cylinders with different radii, arranged in a centrally symmetrical manner, and is not sensitive to polarization. The positions of the electric dipole and magnetic dipole can be controlled relatively independently and precisely using the cylinders of different sizes, so that the distance between the two resonances is closer, thereby making the half-width at half-maximum of the reflection peak smaller, the color saturation higher, the reflectivity greater, and the color gamut wider. Moreover, the cylindrical structure uses phase change material. When the phase change material becomes crystalline, it can destroy the magnetic dipole resonance of the metasurface, thereby making the reflection peak of the off state disappear and the reflectivity extremely low. This can greatly improve the reflectivity, on / off ratio, saturation and color gamut of the device, thereby effectively improving the optical effect of the reflective display; (2) The functional layer uses phase change material. Since the phase change material switches between the amorphous and crystalline states very quickly, the minimum time interval of the amorphization process is about 200 ns, and the crystallization process is 500 ns. Moreover, the phase change material can switch between the amorphous and crystalline states in electrical devices up to 10 9 This effectively improves the refresh rate and lifespan of the metasurface.

[0053] In one embodiment, when the cylindrical structure is a sandwich structure, in a single sub-pixel unit, the substrate thickness can be set to 50 nm, the phase change material layer thickness in the functional layer can be set to 10–100 nm, the dielectric layer thickness in the functional layer can be set to 10–150 nm, the radius of the large cylinder can be set to 80–150 nm, the radius of the small cylinder can be set to 40–70 nm, and the period of the metasurface switching device can be set to 300–1500 nm. The above-mentioned structural parameter design of the single sub-pixel unit enables the metasurface switching device provided by this invention to display colors such as red, green, blue, yellow, magenta, and cyan in the visible light band (400–700 nm).

[0054] Preferably, the dielectric layer material used in the functional layer provided in this embodiment can be titanium dioxide. Titanium dioxide has an extinction coefficient of almost zero in the visible light band, its loss is negligible, and its refractive index is relatively stable. The phase change material layer material can be antimony sulfide. The refractive index of antimony sulfide is very close to that of titanium dioxide, and compared with other phase change materials, antimony sulfide has a smaller extinction coefficient in the visible light band, making it a low-loss phase change material.

[0055] The following detailed description, in conjunction with specific embodiments, illustrates the present invention of an adjustable reflective metasurface switching device for the visible light band:

[0056] In all the following specific embodiments, the cylindrical structure in the device adopts a sandwich structure, wherein the intermediate phase change material layer is Sb₂S₃, and the extinction coefficient of Sb₂S₃ is relatively small in the visible light range, such as... Figure 3 Therefore, the loss is relatively low, making it suitable for display materials in the visible light range; the upper and lower dielectric layers are made of rutile TiO2, which is stable and conductive, and is beneficial for electro-tuning the bottom of the phase change material; the substrate is made of transparent SiO2 crystal, which has a small change in refractive index and a negligible extinction coefficient, so the light absorption is close to zero, making it very suitable for display in the visible light band.

[0057] In optical design, the positions of the electric and magnetic dipoles are adjusted by modifying the radii of the large and small cylinders in the metasurface, the thickness of the phase change material layer and dielectric layer in the functional layer sandwich structure, and the period of the metasurface, thereby achieving the effect of adjusting the reflection peak position.

[0058] Example 1:

[0059] The electro-reconfigurable reflective metasurface switch device provided in this embodiment 1 can display red in the on state and black in the off state. The SiO2 thickness is 50nm, the period is 650nm, the radius of the small cylinder is 60nm, the radius of the large cylinder is 120nm, the thickness of Sb2S3 is 50nm, and the thickness of the two TiO2 layers is 50nm.

[0060] Based on the above structural parameters, simulation software was used to verify its reflectivity, and it was found that, as Figure 4 As shown in the figure, curve a represents the reflectivity of the device at various wavelengths when the phase change material is in the amorphous state, i.e., the on state; curve c represents the reflectivity of the device at various wavelengths when the phase change material is in the crystalline state, i.e., the off state. Figure 5 It represents the positions of the device in the on and off states in the chromaticity diagram.

[0061] Simulation results show that the red reflective metasurface switching device provided in this embodiment is feasible. The peak position is at 620nm, which can achieve a reflectivity of nearly 100%. The reflectivity at other wavelengths is almost all below 10%. The full width at half maximum (FWHM) is 40nm. The device displays black when off. The reflectivity in the visible light band is almost all below 10%. The on / off ratio is greater than 95%.

[0062] Example 2:

[0063] The electroreconfigurable reflective metasurface switching device provided in this embodiment 2 can display green in the on state and black in the off state. The SiO2 thickness is 50nm, the period is 560nm, the radius of the small cylinder is 50nm, the radius of the large cylinder is 100nm, the thickness of Sb2S3 is 60nm, and the thickness of the two TiO2 layers is 30nm.

[0064] Based on the above structural parameters, simulation software was used to verify its reflectivity, and it was found that, as Figure 6As shown in the figure, curve a represents the reflectivity of the device at various wavelengths when the phase change material is in the amorphous state, i.e., the on state; curve c represents the reflectivity of the device at various wavelengths when the phase change material is in the crystalline state, i.e., the off state. Figure 7 It represents the positions of the device in the on and off states in the chromaticity diagram.

[0065] Simulation results show that the green reflective metasurface switching device provided in this embodiment is feasible. The peak position is at 550nm, which can achieve 50% reflectivity. The reflectivity at other wavelengths is almost 0%. The full width at half maximum (FWHM) is 30nm. The device displays black when off. The reflectivity in the visible light band is all below 10%, and the on / off ratio is about 45%.

[0066] Example 3:

[0067] The electro-reconfigurable reflective metasurface switching device provided in this embodiment 3 can display blue in the on state and black in the off state. The SiO2 thickness is 50nm, the period is 500nm, the radius of the small cylinder is 50nm, the radius of the large cylinder is 100nm, the thickness of Sb2S3 is 10nm, and the thickness of the two TiO2 layers is 30nm.

[0068] Based on the above structural parameters, simulation software was used to verify its reflectivity, and it was found that, as Figure 8 As shown in the figure, curve a represents the reflectivity of the device at various wavelengths when the phase change material is in the amorphous state, i.e., the on state; curve c represents the reflectivity of the device at various wavelengths when the phase change material is in the crystalline state, i.e., the off state. Figure 9 It represents the positions of the device in the on and off states in the chromaticity diagram.

[0069] Simulation results show that the blue reflective metasurface switching device provided in this embodiment is feasible. The peak position is at 470nm, which can achieve a reflectivity of 45%. The reflectivity at other wavelengths is almost all below 10%. The full width at half maximum (FWHM) is 25nm. The device displays black in the off state. The reflectivity in the visible light band is below 18%, and the on / off ratio is about 27%.

[0070] Example 4:

[0071] The electroreconfigurable reflective metasurface switching device provided in Example 4 changes its on-state color from green to yellow and then to red as the period increases from 520 nm to 680 nm. Specific structural parameters are: SiO2 thickness of 50 nm, small cylinder radius of 50 nm, large cylinder radius of 100 nm, Sb2S3 thickness of 60 nm, and the two TiO2 layers thickness of 30 nm each.

[0072] Based on the above structural parameters, the reflectivity was simulated using simulation software to obtain the results. Figure 10As shown, the on-state color of the device smoothly transitions from green through yellow to red in the chromaticity diagram. Simulation results demonstrate that the metasurface proposed in this invention possesses significant controllability and can display multiple colors in the visible light band.

[0073] Example 5:

[0074] This embodiment 5 provides a 12x12 square pixel array, which allows for individual addressing and control of each pixel unit to achieve electrical switching. For example... Figure 13 As shown, the period of a pixel unit is 2x2. Applying a long pulse with a lower value can change the phase change material from an amorphous state to a crystalline state, while applying a short pulse with a higher value can change it from a crystalline state to an amorphous state. Different combinations of pixels in different states can display specific content, thus achieving full-color display. The RGGB color system's display color gamut is as follows: Figure 14 As shown, the color gamut can reach 37% NTSC.

[0075] This invention also provides a method for fabricating an electro-reconfigurable reflective metasurface switching device, such as... Figure 11 As shown, when a cylindrical structure uses a sandwich structure, the specific steps are as follows:

[0076] Step 1: Transfer the pattern of the functional layer onto the substrate using photolithography or nanoimprint lithography.

[0077] Step 2: Grow the first dielectric layer on the substrate using thin film deposition.

[0078] Step 3: Grow a phase change material layer on the substrate using thin film deposition.

[0079] Step 4: Grow a second dielectric layer on the substrate using thin film deposition.

[0080] Step 5: Use a stripping process to remove the photoresist and leave a cylindrical functional layer.

[0081] Step 6: Connect the voltage source to the heating plate on the substrate to obtain an electro-reconfigurable metasurface.

[0082] When a cylindrical structure employs a two-layer stacked structure, such as Figure 12 As shown, the specific steps are as follows:

[0083] Step 1: Grow a conductive layer on the substrate using thin film deposition.

[0084] Step 2: Transfer the pattern of the functional layer onto the substrate using photolithography or nanoimprint lithography.

[0085] Step 3: Grow a phase change material layer on the substrate using thin film deposition.

[0086] Step 4: Grow a dielectric layer on the substrate using thin film deposition.

[0087] Step 5: Use a stripping process to remove the photoresist and leave a cylindrical functional layer.

[0088] Step 6: Connect the voltage source to the conductive layer on the substrate to obtain an electro-reconfigurable metasurface.

[0089] The reflective metasurface switching device prepared by the above steps can be used as a pixel unit. If the above steps are repeated with different structural parameters, different metasurface pixel units can be manufactured, and various functions can be designed and implemented according to requirements.

[0090] The reflective metasurface switching device of the present invention achieves a minimum pixelation period of 2x2. The pixel unit can be individually addressed and driven by the thermal effect generated by the current. When the temperature reaches close to the melting point of the phase change material, it is slowly cooled, which can change the phase change material from an amorphous state to a crystalline state. When the temperature exceeds the melting point of the phase change material, it is rapidly cooled, which can change the phase change material from a crystalline state to an amorphous state.

[0091] The specific arrangement of pixels for full-color display in this invention is a horizontally arranged, periodically segmented array. Each period consists of four pixels: red, green, blue, and cyan. Full-color display is achieved by controlling the brightness of individual pixels. Furthermore, the red, green, and blue reflective metasurface switching devices of this invention, when combined, can achieve the RGGB color system, reaching a color gamut of 37% NTSC. Brightness can be adjusted using intermediate states of phase-change materials, ultimately realizing switching. This adjustment is non-volatile, consuming energy only during switching, significantly saving energy consumption at low refresh rates.

[0092] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electro-reconfigurable reflective metasurface switching device, used to display stable colors in the visible light band and achieve in-situ adjustment of color brightness, characterized in that, It includes multiple pixel units arranged in a horizontal row and column periodically. The minimum period of a single pixel unit is 2×2. The period is composed of four sub-pixel units: RGGB. Each sub-pixel unit includes a functional layer disposed above the substrate. The functional layer consists of two pairs of cylinders with different radii. The four cylinders are arranged in a matrix. The two cylinders located on the same diagonal of the matrix have the same radius. The structure of the cylinders is a sandwich structure or a two-layer stacked structure. The sandwich structure includes upper and lower dielectric layers and an intermediate phase change material layer. The two-layer stacked structure includes an upper dielectric layer and a lower phase change material layer. The stable color display in the visible light band is achieved by modulating the resonant positions of the electric and magnetic dipoles of the metasurface switching device, resulting in a high reflection peak at the resonant wavelength. This resonance satisfies... ε =(4 -μ ) / (2) μ+ 1) appears at the time, ε and μ Corresponding to the dielectric constant and relative permeability of the metasurface switching device, the resonant wavelength is achieved by adjusting the radii of the two pairs of cylinders, the thickness of each layer in the cylindrical structure, and the period of the metasurface switching device; the phase change material layer includes two phase states, amorphous and crystalline, and the in-situ color brightness is adjusted by changing the reflectivity of the metasurface switching device by controlling the phase change state of the phase change material layer.

2. The electro-reconfigurable reflective metasurface switching device according to claim 1, characterized in that, The phase change material layer is made of antimony sulfide.

3. The electro-reconfigurable reflective metasurface switching device according to claim 1 or 2, characterized in that, The metasurface switching device displays colors including red, green, blue, yellow, magenta, and cyan in the visible light band.

4. The electro-reconfigurable reflective metasurface switching device according to claim 3, characterized in that, When the cylindrical structure is a sandwich structure, in a single sub-pixel unit, the thickness of the substrate is 50 nm, the thickness of the phase change material layer in the functional layer is 10–100 nm, the thickness of the dielectric layer in the functional layer is 10–150 nm, the radii of the cylinders on different diagonals are 80–150 nm and 40–70 nm, respectively, and the period of the metasurface switching device is 300–1500 nm.

5. The electro-reconfigurable reflective metasurface switching device according to claim 1, characterized in that, When the cylindrical structure is a two-layer stacked structure, the substrate includes a substrate and a conductive layer disposed on the substrate, and both the conductive layer material and the dielectric layer material are titanium dioxide.

6. The electro-reconfigurable reflective metasurface switching device according to claim 5, characterized in that, In a single sub-pixel unit, when the thickness of the substrate is 50nm, the thickness of the phase change material layer is 60nm, the thickness of the two layers of titanium dioxide material is 30nm, and the radii of the two pairs of cylinders are 100nm and 50nm respectively, by adjusting the period of the metasurface switching device from 520nm to 680nm, color control can be achieved by moving the color from green to yellow and then to red.

7. The electro-reconfigurable reflective metasurface switching device according to claim 1, characterized in that, When the cylindrical structure is a sandwich structure, the substrate is made of silica or indium tin oxide.

8. The electro-reconfigurable reflective metasurface switching device according to claim 1, characterized in that, When the cylindrical structure is a sandwich structure, the fabrication method of the metasurface switching device includes the following steps: The pattern of the functional layer is transferred onto the substrate using photolithography or nanoimprint lithography. A first dielectric layer is grown on a substrate using a thin film deposition method; A phase change material layer is grown on a substrate using thin film deposition. A second dielectric layer is grown on a substrate using thin film deposition. The photoresist is removed using a stripping process, leaving a cylindrical functional layer. By connecting an external voltage source to a heating plate on the substrate, a metasurface switching device is obtained.

9. The electro-reconfigurable reflective metasurface switching device according to claim 1, characterized in that, When the cylindrical structure is a two-layer stacked structure, the fabrication method of the metasurface switching device includes the following steps: A conductive layer is grown on a substrate using thin film deposition. The pattern of the functional layer is transferred onto the substrate using photolithography or nanoimprint lithography. A phase change material layer is grown on a substrate using thin film deposition. A dielectric layer is grown on a substrate using thin film deposition. The photoresist is removed using a stripping process, leaving a cylindrical functional layer. By connecting an external voltage source to a conductive layer on a substrate, a metasurface switching device is obtained.

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