An electrically reconfigurable metasurface device within the visible spectrum

Abstract

The application discloses a visible spectrum electro-induced reconfigurable regulation super surface device, comprising a plurality of pixel units arranged in horizontal rows and columns periodically, the pixel unit comprising a substrate part and a functional layer part composed of a plurality of arrayed elliptical cylinders, the elliptical cylinder being made of a phase change material; when the phase change material is in an amorphous state, the super surface device is used for filtering in the visible spectrum, realizing transmission of a corresponding light field color, and the type of the light field color required for transmission is achieved by regulating and adjusting the major and minor radii of the elliptical cylinder in the functional layer part, the horizontal and vertical periods of the functional layer part and the thickness of the functional layer part, and changing the position of the electric dipole and the magnetic dipole of the super surface device to reach the resonant wavelength; after the phase change material is phase changed, the super surface device is used for realizing dynamic tuning of the light field color. The application can realize dynamic tuning of the light field color in the visible spectrum, has the characteristics of non-volatility, high speed, low power consumption and the like, and has rich application scenarios.

Description

Technical Field

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

[0002] Color filters, as optical devices capable of tunable light fields, play a significant role in imaging and other fields. Color filters include reflective and transmissive types, each used in different scenarios. However, the function of traditional dielectric-based color filters is fixed in their design; their ability to control the light field cannot be dynamically tuned after manufacturing. Subsequent developments have yielded some dynamically tunable color filters, but effective control through mechanical or electrochemical means is difficult to achieve, and the controllability is limited.

[0003] Therefore, there is an urgent need for a dynamic tuning color filter that can achieve non-volatile, low power consumption, and high speed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an electro-reconfigurable metasurface device within the visible spectrum, which can achieve dynamic tuning of light field color within the visible spectrum, and has the characteristics of non-volatility, high speed, and low power consumption, with a wide range of applications.

[0005] To achieve the above objectives, the present invention provides an electro-reconfigurable metasurface device in the visible spectrum. The thin film made of the metasurface device is a transmission-type color filter. The metasurface device includes multiple pixel units arranged in a horizontal row and column periodically. Each pixel unit includes a substrate portion and a functional layer portion arranged from bottom to top. The functional layer portion is composed of several arrayed elliptical cylinders, and the elliptical cylinders are made of phase change material.

[0006] When the phase change material in the functional layer is in an amorphous state, the metasurface device is used to filter within the visible spectrum to achieve transmission of the corresponding light field color. The type of light field color required for transmission is achieved by adjusting the radius of the elliptical cylinder in the X and Y directions, the lateral and longitudinal periods of the functional layer, and the thickness of the functional layer. This changes the position of the electric and magnetic dipoles of the metasurface device at the resonant wavelength, resulting in low transmittance at the resonant wavelength and high transmittance at other wavelengths. When the phase change material in the functional layer undergoes a phase change, the complex refractive index of the functional layer changes, causing a change in the resonant wavelength and achieving dynamic tuning of the light field color.

[0007] The present invention provides an electro-reconfigurable metasurface device within the visible spectrum. The functional layer uses a phase change material with dynamically tunable refractive index. When the phase change material undergoes a phase change, the filtering range of the metasurface device changes accordingly, effectively achieving dynamic tuning of the light field color within the visible spectrum. In addition, the use of a phase change material in the functional layer is advantageous because the phase change of the material is very fast and non-volatile. It maintains its current state until the next stimulus arrives, only consuming energy when the light field color needs to be changed. This gives the metasurface device the characteristics of non-volatility, high speed, and low power consumption, making it suitable for a wide range of applications.

[0008] In one embodiment, the elliptical cylinder is made of a phase change material and a dielectric material, the dielectric material being used to adjust the overall complex refractive index of the functional layer portion.

[0009] In one embodiment, the phase change material is antimony sulfide or antimony selenide.

[0010] In one embodiment, the phase change material in the functional layer undergoes a phase change by applying a voltage pulse, laser heating, or annealing.

[0011] In one embodiment, when the phase change material in the functional layer undergoes a phase change by applying a voltage pulse, the substrate portion includes a substrate and a transparent conductive layer disposed on the substrate, the transparent conductive layer being connected to an external voltage source.

[0012] In one embodiment, the metasurface device switches between light field colors of red, green, blue, yellow, magenta, and cyan within the visible spectrum.

[0013] In one embodiment, the thickness of the transparent conductive layer is 50 nm, the thickness of the functional layer portion is 50–300 nm, the radius of the elliptical cylinder in the functional layer portion in the X and Y directions is 100–200 nm and 20–90 nm respectively, and the lateral and longitudinal period range of the functional layer portion is 350–500 nm.

[0014] In one embodiment, the substrate is made of silicon dioxide, and the transparent conductive layer is made of indium tin oxide or aluminum-doped zinc oxide.

[0015] In one embodiment, the functional layer portion consists of elliptical cylinders arranged in a 2×2 array. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an electro-reconfigurable metasurface device in the visible spectrum provided in an embodiment of the present invention;

[0017] Figure 2 This is a dispersion curve of the refractive index n and extinction coefficient k of the phase change material Sb2S3 provided in an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the structure of a pixel unit provided in an embodiment of the present invention;

[0019] Figure 4 This is the transmission spectrum of the color filter obtained by simulation in Embodiment 1 of the present invention;

[0020] Figure 5 This is the chromaticity diagram of the color filter obtained by simulation in Embodiment 1 of the present invention;

[0021] Figure 6 This is the transmission spectrum of the color filter obtained by simulation in Embodiment 2 of the present invention;

[0022] Figure 7 This is the chromaticity diagram of the color filter obtained by simulation in Embodiment 2 of the present invention;

[0023] Figure 8 This invention provides a driving method for pixel units and an example arrangement of pixelation. Detailed Implementation

[0024] 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.

[0025] Research has revealed that phase change materials (PCMs) undergo phase transitions under external stimuli such as photoelectric and thermal stresses, and their physical properties change accordingly during this process, specifically in terms of refractive index and extinction coefficient. Based on this, this invention provides an electro-reconfigurable metasurface device within the visible spectrum. By utilizing the changes in refractive index and extinction coefficient resulting from the phase transition of the PCM, the resonant wavelengths of the electric and magnetic dipoles in the metasurface device are altered. This results in low transmittance at the resonant location and high transmittance elsewhere, thereby achieving dynamic tuning of the light field color within the visible spectrum.

[0026] Figure 1 This is a schematic diagram of the structure of an electrically reconfigurable metasurface device in the visible spectrum provided by an embodiment of the present invention, as shown below. Figure 1 As shown, the metasurface device includes multiple pixel units arranged in a horizontal row and column periodically. Each pixel unit includes a substrate portion and a functional layer portion arranged from bottom to top. The functional layer portion is composed of several elliptical cylinders arranged in an array, and the elliptical cylinders are made of phase change material.

[0027] In this embodiment, when the phase change material of the functional layer is in an amorphous state, the metasurface device is used for filtering within the visible spectrum to achieve transmission of the corresponding light field color. The type of light field color required for transmission is achieved by adjusting the radii of the elliptical cylinders in the X and Y directions, the transverse and longitudinal periods of the functional layer, and the thickness of the functional layer, thereby changing the wavelength at which the electric and magnetic dipoles of the metasurface device resonate. To further improve the transmittance of the metasurface device, the substrate provided in this embodiment can be made of a high-transmittance material.

[0028] When the phase change material in the functional layer undergoes a phase transition, the complex refractive index of the functional layer changes, causing a change in the resonant wavelength, which in turn alters the filtering range, thereby achieving dynamic tuning of the light field color. Specifically, the phase change material provided in this embodiment can be a low-loss material in the visible light band, including but not limited to antimony sulfide or antimony selenide. The phase transition of the phase change material can be controlled by applying voltage pulses, laser heating, or annealing.

[0029] It should be noted that metasurface devices with cylindrical structures made of traditional dielectric materials will generate electric and magnetic dipole resonances. The wavelength of the resonance is related to the thickness, radius, period of the cylinder, and the refractive index of the material. However, the optical performance of such metasurface devices is fixed once they are manufactured. In this embodiment, the dielectric material in traditional metasurface devices is replaced with a phase change material with a dynamically tunable refractive index. By changing the state of the phase change material, the dynamic tuning of the metasurface's optical performance can be achieved.

[0030] Furthermore, in the optical design stage, changing the radius of a conventional cylinder with a uniform radius simultaneously affects both the magnetic and electric dipoles. This embodiment designs the cylinder as an ellipse, allowing for relatively independent control of the resonance wavelengths of the electric and magnetic dipoles to achieve specific color transmission. Multiple resonances can be achieved under incident light illumination. The resonance wavelength is influenced by multiple factors, including the thickness of the substrate and functional layer, and the radius of the elliptical cylinder. In multiple resonances, the directions for magnetic and electric dipole resonance are perpendicular. Therefore, by adjusting the radii of the elliptical cylinder in the X and Y directions (hereinafter referred to as the major and minor radii), the resonance wavelength can be adjusted, resulting in low transmittance at the resonance wavelength and high transmittance at other wavelengths. When the phase change material in the functional layer undergoes a phase transition, its complex refractive index changes, and correspondingly, the resonance wavelength also changes. The phase change material in its crystalline state has a higher refractive index, resulting in a longer resonance wavelength.

[0031] The electro-reconfigurable metasurface device provided in this embodiment uses a phase change material with dynamically tunable refractive index in the functional layer. When the phase change material undergoes a phase change, the filtering range of the metasurface device changes accordingly, effectively achieving dynamic tuning of the light field color within the visible spectrum. In addition, the phase change material in the functional layer is very fast, and the phase change is non-volatile. It will maintain its current state until the next stimulus arrives, and only consume energy when the light field color needs to be changed. This makes the metasurface device non-volatile, high-speed, and low-power, with a wide range of applications.

[0032] In one embodiment, in addition to being made of a phase change material, the elliptical cylinder may also incorporate other thin film materials to adjust the overall complex refractive index of the functional layer portion. Specifically, the thin film material may be a dielectric material commonly used in the art.

[0033] In one embodiment, when the phase change material in the functional layer undergoes a phase change by applying a voltage pulse, the substrate portion may employ a structure of a substrate and a transparent conductive layer disposed on the substrate, the transparent conductive layer being connected to an external voltage source. The substrate may be made of silicon dioxide, and the transparent conductive layer may be made of indium tin oxide or aluminum-doped zinc oxide.

[0034] The working principle of this embodiment for regulating the phase change state of a phase change material using a voltage source is as follows: applying currents of different amplitudes and durations to both ends of the transparent conductive layer in the substrate will generate heat in the conductive layer, which will act as a heating plate; when the temperature reaches close to the melting point of the phase change material, it will be slowly cooled, which will cause the phase change material to change from an amorphous state to a crystalline state; when the temperature exceeds the melting point of the phase change material, it will be rapidly cooled, which will cause the phase change material to change from a crystalline state to an amorphous state.

[0035] Furthermore, in this embodiment, the thickness of the transparent conductive layer is 50 nm, the thickness of the functional layer is 50–300 nm, the major and minor radii of the elliptical cylinders in the functional layer are 100–200 nm and 20–90 nm, respectively, and the lateral and longitudinal periodic ranges of the functional layer are both 350–500 nm. In this embodiment, the metasurface device constructed with the above structural parameters can switch between red, green, blue, yellow, magenta, and cyan light field colors within the visible spectrum (400–760 nm).

[0036] The following detailed description, in conjunction with specific embodiments, illustrates the electro-reconfigurable metasurface device within the visible spectrum provided by this invention:

[0037] In the metasurface devices provided in Examples 1 and 2 below, the functional layer is composed of a single elliptical cylinder. The phase change material in the functional layer is Sb₂S₃, which has a relatively small extinction coefficient in the visible spectrum. Figure 2 As shown, the resulting loss is relatively low, making it suitable for transmission-through displays in the visible spectrum. The substrate portion adopts a structure of a base and a transparent conductive layer disposed on the base. The transparent conductive layer is made of indium tin oxide (ITO) and serves as the bottom electrode. A phase change material undergoes a phase change by resistive heating.

[0038] In optical design, the position of resonance is mainly adjusted by modifying the major and minor radii of the elliptical cylinder in the functional layer, the transverse and longitudinal periods of the functional layer, and the thickness of the functional layer.

[0039] Example 1

[0040] This embodiment 1 provides a PCM transmission metasurface color filter that can switch from yellow to magenta, such as... Figure 3 As shown, from bottom to top, the layers are silicon dioxide (SiO2), indium tin oxide (ITO), and antimony sulfide (Sb2S3). The elliptical cylinder in the functional layer has a short radius of 75nm, a long radius of 160nm, a thickness of 160nm, and a period of 390nm in both the horizontal and vertical directions.

[0041] When a low-intensity, long-duration electric pulse is applied to indium tin oxide (ITO), the generated heat causes the phase change material to change from an amorphous state to a crystalline state, and the refractive index and extinction coefficient increase accordingly. When a high-intensity, short-duration electric pulse is applied to the bottom ITO, the generated heat causes the phase change material to change from a crystalline state to an amorphous state, and the refractive index and extinction coefficient decrease accordingly. Therefore, the positions of the electric dipole and magnetic dipole resonance will change. Specifically, the higher the refractive index, the longer the wavelength of resonance.

[0042] Based on the above structure and parameters, software simulation was used to verify its transmittance, and it was found that, as Figure 4 and 5 As shown in the figure, a and c represent the transmittance of the color filter at various wavelengths when the phase change material is in the amorphous and crystalline states, respectively, and its position in the chromaticity diagram within the visible light range.

[0043] Simulation results show that when the phase change material is in an amorphous state, the metasurface device exhibits low transmittance in the 400–500 nm wavelength range and high transmittance in other wavelength ranges, appearing as yellow on the chromaticity diagram. When the phase change material is in a crystalline state, the metasurface device exhibits low transmittance in the 500–600 nm wavelength range and high transmittance in other wavelength ranges, appearing as magenta on the chromaticity diagram. Therefore, the design method for the yellow-and-magenta switching PCM transmission metasurface filter provided in this embodiment is reliable and can achieve high transmittance and a wide controllable range.

[0044] Example 2

[0045] The PCM transmission metasurface color filter provided in this embodiment 2 can switch from magenta to cyan, such as Figure 3 As shown, from bottom to top, the layers are silicon dioxide (SiO2), indium tin oxide (ITO), and antimony sulfide (Sb2S3). The short radius of the functional layer is 25nm, the long radius is 160nm, the thickness is 270nm, and the horizontal and vertical periods are 430nm and 450nm, respectively.

[0046] When a low-intensity, long-duration electric pulse is applied to indium tin oxide (ITO), the generated heat causes the phase change material to change from an amorphous state to a crystalline state, and the refractive index and extinction coefficient increase accordingly. When a high-intensity, short-duration electric pulse is applied to the bottom ITO, the generated heat causes the phase change material to change from a crystalline state to an amorphous state, and the refractive index and extinction coefficient decrease accordingly. Therefore, the positions of the electric dipole and magnetic dipole resonance will change. Specifically, the higher the refractive index, the longer the wavelength of resonance.

[0047] Based on the above structure and parameters, software simulation was used to verify its transmittance, and it was found that, as Figure 6 and 7 As shown in the figure, a and c represent the transmittance of the color filter at various wavelengths when the phase change material is in the amorphous and crystalline states, respectively, and its position in the chromaticity diagram within the visible light range.

[0048] Simulation results show that when the phase change material is in an amorphous state, the metasurface device exhibits low transmittance in the 500–600 nm wavelength range and high transmittance in other wavelength ranges, appearing as magenta on the chromaticity diagram. When the phase change material is in a crystalline state, the metasurface device exhibits low transmittance in the 550–700 nm wavelength range and high transmittance in other wavelength ranges, appearing as cyan on the chromaticity diagram. Therefore, the design method for the magenta and cyan switching PCM transmission metasurface filter provided in this embodiment is reliable and can achieve high transmittance and a wide controllable range.

[0049] Example 3

[0050] This embodiment 3 provides a 7x7 square pixel array, which allows for individual addressing and control of each pixel unit to achieve electrical switching. For example... Figure 8 As shown, the pixel unit is a 2x2 cylindrical structure. Applying a long pulse with a low amplitude can change the phase change material from an amorphous state to a crystalline state, while applying a short pulse with a high amplitude can change the phase change material from a crystalline state to an amorphous state. Different combinations of pixels in different states can display specific content.

[0051] The metasurface device provided by this invention achieves pixelation with a minimum period of 2x2. Each pixel unit can be individually addressed and driven by the thermal effect of current. Currents of different amplitudes and durations are applied to both ends of a conductive layer in the substrate, generating heat and acting as a heating plate. When the temperature reaches near the melting point of the phase change material, slow cooling transforms the phase change material from an amorphous to a crystalline state. Conversely, rapid cooling transforms the phase change material from a crystalline to an amorphous state when the temperature exceeds its melting point. The pixels are arranged in a rectangular array with periodic horizontal rows and columns. By controlling the state of devices at different positions, different content can be displayed.

[0052] 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 metasurface device in the visible spectrum, characterized in that, The thin film made of metasurface device is a transmissive color filter. The metasurface device includes multiple pixel units arranged in a horizontal row and column periodically. Each pixel unit includes a substrate portion and a functional layer portion arranged from bottom to top. The functional layer portion is composed of several arrayed elliptical cylinders, which are made of phase change material. When the phase change material in the functional layer is in an amorphous state, the metasurface device is used for filtering within the visible spectrum to achieve transmission of the corresponding light field color. The type of light field color required for transmission is achieved by adjusting the radii of the elliptical cylinder in the X and Y directions, the lateral and longitudinal periods of the functional layer, and the thickness of the functional layer. This changes the position of the electric and magnetic dipoles of the metasurface device at the resonant wavelength, resulting in low transmittance at the resonant wavelength and high transmittance at other wavelengths. When the phase change material in the functional layer undergoes a phase change, the complex refractive index of the functional layer changes, causing a change in the resonant wavelength and achieving dynamic tuning of the light field color. The elliptical cylinder in the functional layer has radii ranging from 100 to 200 nm in the X direction and from 20 to 90 nm in the Y direction, the lateral and longitudinal period of the functional layer ranges from 350 to 500 nm, and the thickness of the functional layer ranges from 50 to 300 nm.

2. The electroreconfigurable metasurface device in the visible spectrum according to claim 1, characterized in that, The elliptical cylinder is made of phase change material and dielectric material, and the dielectric material is used to adjust the overall complex refractive index of the functional layer portion.

3. The electroreconfigurable metasurface device in the visible spectrum according to claim 1, characterized in that, The phase change material is either antimony sulfide or antimony selenide.

4. The electroreconfigurable metasurface device in the visible spectrum according to claim 1, characterized in that, The phase change material in the functional layer undergoes a phase change by applying a voltage pulse, laser heating, or annealing.

5. The electroreconfigurable metasurface device in the visible spectrum according to claim 4, characterized in that, When the phase change material in the functional layer undergoes a phase change by applying a voltage pulse, the substrate includes a substrate and a transparent conductive layer disposed on the substrate, the transparent conductive layer being connected to an external voltage source.

6. The electroreconfigurable metasurface device in the visible spectrum according to claim 5, characterized in that, The metasurface device switches between red, green, blue, yellow, magenta, and cyan light field colors within the visible spectrum.

7. The electroreconfigurable metasurface device in the visible spectrum according to claim 6, characterized in that, The thickness of the transparent conductive layer is 50 nm.

8. The electro-reconfigurable metasurface device in the visible spectrum according to claim 7, characterized in that, The substrate is made of silicon dioxide, and the transparent conductive layer is made of indium tin oxide or aluminum-doped zinc oxide.

9. The electroreconfigurable metasurface device in the visible spectrum according to claim 1, characterized in that, The functional layer consists of elliptical cylinders arranged in a 2×2 array.

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