Triple optical information multiplexing method based on polarization-modulated plasmonic metasurface

Abstract

The application discloses a kind of triple optical information multiplexing methods based on polarization modulation plasmonic super surface, first construct the structural unit with along three different directions arrangement module for forming super surface, the size of module in structural unit is optimized, so that module structure can produce spectral response to the incident linear polarized light along a certain direction, spectral position is located at blue, green and red band respectively, and there is no structural color response to the incident linear polarized light of vertical direction polarization;Based on the optimized super surface, three information channels are constructed along three directions;The binary information of three different color binary patterns is converted into the selection of module design in structural unit, to realize that three channels each display a different color binary pattern;By changing the polarization angle of linear polarized light incident to super surface, the reading of three channels is realized, and three different images are displayed.The application improves the information storage capacity of super surface, and information loading and reading mode is simple.

Description

Technical Field

[0001] This invention relates to the field of micro-nano optics, and in particular to a triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces. Background Technology

[0002] Optical metasurface devices utilize the interaction between micro / nano structures and incident light waves to manipulate light waves. Through structural design, various optical manipulation devices can be realized, such as controlling the intensity and phase of light wave reflection and transmission. Optical metasurface devices are composed of subwavelength structural units and have the advantages of small feature size and high spatial resolution. Among them, metasurface structural color devices have received extensive research due to their advantages such as resistance to fading, high spatial resolution, and environmental friendliness. Metasurface structural color printing can achieve high-density optical information storage, and polarization-dependent metasurface structural color devices can store multiple optical information on the same optical device. Most existing polarization-modulated metasurface structural color devices use mutually perpendicular modules as the structural units of the metasurface, and the two mutually perpendicular modules have different dimensional parameters, or use array structures with different periods in mutually perpendicular directions to achieve differentiated optical responses to light waves. Therefore, metasurface devices can only store two types of optical information, resulting in a limited number of information reuses, a small color gamut, and most metasurface structural color devices can only operate in a single mode of reflection or transmission. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces. By cleverly designing polarization-modulated plasmonic metasurface structured color devices, optical information can be independently stored in three channels, successfully realizing the multiplexing of triple optical information and simultaneously enabling reading in both reflection and transmission modes.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A triple optical information multiplexing method based on polarization-modulated plasmonic metasurface, wherein the polarization-modulated plasmonic metasurface includes a substrate and structural units arranged in a square periodic pattern on the substrate. Each structural unit includes three micro / nano structural modules, and the major axes of the three micro / nano structural modules are placed along 0°, 60° and 120°, respectively.

[0006] The triple optical information multiplexing method includes the following steps:

[0007] Step 1: Use electromagnetic simulation tools to calculate the optical response of the structural unit, set the working wavelength range, and optimize the size parameters of the three micro-nano structural modules in the structural unit so that the spectral response positions of the three micro-nano structural modules are located in the blue, green and red bands respectively, thereby constructing three information channels along three directions;

[0008] Step 2: Design blue, green and red binary patterns, and convert their binary information into selection of all or part of the micro-nano structure modules in the structural unit, so that each of the three information channels displays a binary pattern of a different color, thereby completing the design and construction of the metasurface;

[0009] Step 3: By changing the polarization angle of the incident linearly polarized light, the three information channels based on the polarization-modulated plasmonic metasurface are read, and three different images are displayed.

[0010] Furthermore, step one specifically includes the following sub-steps:

[0011] (1.1) Arrange structural units in a periodic square pattern on the substrate, with the vertex of a structural unit as the origin, and the two directions of the periodic square as the x-axis and y-axis, respectively; the angle with the positive x-axis is defined as the placement direction of the micro / nano structure module;

[0012] (1.2) Arrange a micro / nano structure module with a placement direction of 0° in each structural unit. Linearly polarized light polarized along the 0° direction and linearly polarized light polarized along the 90° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light and obtains the spectral position of the two linearly polarized light beams in the wavelength band. Adjust the size of the micro / nano structure module so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 0° direction is located in the blue, green or red wavelength band; (2) there is no structural color response to the incident linearly polarized light polarized along the 90° direction.

[0013] Similarly, a micro / nano structure module with a placement direction of 60° is arranged in each structural unit. Linearly polarized light polarized along the 60° direction and linearly polarized light polarized along the 150° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light, and the spectral positions of the two linearly polarized light beams are obtained. The size of the micro / nano structure module is adjusted so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 60° direction is located in one of the two other primary colors that are different from the reflection spectral position of the micro / nano structure module with a placement direction of 0°; (2) there is no structural color response to the incident linearly polarized light polarized along the 150° direction.

[0014] Similarly, a micro / nano structure module with a placement direction of 120° is arranged in each structural unit. Linearly polarized light polarized along the 120° direction and linearly polarized light polarized along the 30° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light and obtains the spectral position band of the two linearly polarized light beams. The size of the micro / nano structure module is adjusted so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 120° direction is located in a different band of the three primary colors than the reflection spectral position of the micro / nano structure modules with placement directions of 0° and 60°; (2) there is no structural color response to the incident linearly polarized light polarized along the 30° direction.

[0015] Furthermore, in step two, binary patterns of blue, green, and red are designed, and their binary information is converted into rules for selecting all or part of the micro / nano structural modules in the structural unit, as follows:

[0016] When a structural unit contains a micro / nano structure module whose major axis is parallel to the angle of the polarizer, the structural unit displays the corresponding structural color, i.e., the corresponding structural color is assigned a value of 1; when a structural unit does not contain a micro / nano structure module whose major axis is parallel to the angle of the polarizer, the structural unit does not display the corresponding structural color, i.e., the corresponding structural color is assigned a value of 0.

[0017] This allows us to establish a correspondence between pixel information in a binary image and whether the structural unit contains the corresponding micro / nano structure module.

[0018] Furthermore, the micro / nano structure module has a three-layer structure, consisting of a metal layer, a dielectric layer, and a metal layer from top to bottom.

[0019] Furthermore, the micro / nano structure module is a cuboid.

[0020] Furthermore, the substrate is made of an optically transparent medium material.

[0021] Furthermore, the material of the metal layer is selected from materials that have good plasmonic response in the visible light band, including aluminum, gold, and silver; the material of the dielectric layer is selected from any one of silicon dioxide, aluminum oxide, and magnesium fluoride.

[0022] Furthermore, the operating mode of the polarization-modulated plasmonic metasurface is either reflective or transmissive.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention presents a triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces. Utilizing module design and polarization modulation principles, the metasurface device is designed, breaking away from the traditional mutually perpendicular module layout. Multiple modules with different orientations are used to construct the metasurface. The module layout within each pixel is designed according to the optical information, and the size of the metasurface device is optimized. Simultaneously, a correspondence is established between pixel information in a binary image and whether the structural unit contains the corresponding micro / nano structure module, thereby achieving triple optical information encoding. This invention multiplexes a large amount of optical information; three-channel information storage and retrieval can be achieved simply by rotating the polarization angle of the incident light. Furthermore, the device can acquire information simultaneously in both reflection and transmission modes, thus expanding the application prospects of this polarization-modulated triple optical information multiplexing metasurface.

[0025] Furthermore, the metasurface structural units of this invention are on the subwavelength scale and can store information through three channels, thus improving the information storage capacity of the metasurface structure. This micro / nano structure can be widely used in the field of micro / nano photonics, such as optical information storage, optical anti-counterfeiting, and information encryption. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the micro / nano structure based on the polarization-modulated plasmonic metasurface of the present invention. The left figure is a front cross-sectional view and the right figure is a top view. In the figure, 1 represents aluminum and 2 represents silicon dioxide.

[0027] Figure 2 This is a schematic diagram of a metasurface structure for QR code reuse.

[0028] Figure 3 This is the test optical path diagram based on the polarization-modulated plasmonic metasurface. Detailed Implementation

[0029] 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. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Any polarization-modulated metasurface structured color device developed by replacing other materials and metasurface structures will infringe upon the patent of this invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concept of the invention.

[0030] In the triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces of the present invention, the polarization-modulated plasmonic metasurface includes a substrate and structural units arranged in a periodic square pattern on the substrate. Each structural unit includes three micro / nano structural modules, and the major axes of the three micro / nano structural modules are placed along 0°, 60°, and 120°, respectively. Figure 1As shown, the micro / nano structure module preferably has a three-layer structure, consisting of a metal layer, a dielectric layer, and another metal layer from top to bottom. The micro / nano structure module has shapes with different characteristic dimensions in mutually perpendicular directions, such as a cuboid or a shape obtained by vertically stretching an ellipse. Furthermore, in terms of material selection, the substrate is made of an optically transparent dielectric material, including materials such as silicon dioxide, alumina, and magnesium fluoride; the metallic materials in the micro / nano structure module include materials such as aluminum, gold, and silver, which have good plasmon response in the visible light band. The dielectric layer in the micro / nano structure module is made of an optically transparent dielectric, including materials such as silicon dioxide, alumina, and magnesium fluoride.

[0031] The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces of the present invention specifically includes the following steps:

[0032] Step 1: Calculate the optical response of the structural unit using electromagnetic simulation tools, set the working wavelength range, and optimize the size parameters of the three micro / nano structural modules in the structural unit. The optimization goal is to find three size parameters such that when incident light is polarized along the long axis of the module, the metasurface formed by the corresponding modules produces spectral responses in the blue, green, and red bands, respectively. That is, the spectral response positions of the three micro / nano structural modules are located in the blue, green, and red bands, respectively. However, when incident light is polarized along the short axis of the module, the corresponding modules have no structural color response, thereby constructing three information channels along three directions.

[0033] (1.1) Arrange structural units in a periodic square pattern on the substrate, with the vertex of a structural unit as the origin, and the two directions of the periodic square as the x-axis and y-axis, respectively; the angle with the positive x-axis is defined as the placement direction of the micro / nano structure module;

[0034] (1.2) Arrange a micro / nano structure module with a placement direction of 0° in each structural unit. Linearly polarized light polarized along the 0° direction and linearly polarized light polarized along the 90° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light and obtains the spectral position of the two linearly polarized light beams in the wavelength band. Adjust the size of the micro / nano structure module so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 0° direction is located in the blue, green or red wavelength band; (2) there is no structural color response to the incident linearly polarized light polarized along the 90° direction.

[0035] Similarly, a micro / nano structure module with a placement direction of 60° is arranged in each structural unit. Linearly polarized light polarized along the 60° direction and linearly polarized light polarized along the 150° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light, and the spectral positions of the two linearly polarized light beams are obtained. The size of the micro / nano structure module is adjusted so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 60° direction is located in one of the two other primary colors that are different from the reflection spectral position of the micro / nano structure module with a placement direction of 0°; (2) there is no structural color response to the incident linearly polarized light polarized along the 150° direction.

[0036] Similarly, a micro / nano structure module with a placement direction of 120° is arranged in each structural unit. Linearly polarized light polarized along the 120° direction and linearly polarized light polarized along the 30° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light and obtains the spectral position band of the two linearly polarized light beams. The size of the micro / nano structure module is adjusted so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 120° direction is located in a different band of the three primary colors than the reflection spectral position of the micro / nano structure modules with placement directions of 0° and 60°; (2) there is no structural color response to the incident linearly polarized light polarized along the 30° direction.

[0037] Step 2: Design blue, green and red binary patterns, and convert their binary information into selection of all or part of the micro-nano structure modules in the structural unit, so that each of the three information channels displays a binary pattern of a different color, thereby completing the design and construction of the metasurface;

[0038] When a structural unit contains micro / nano structure modules whose major axis is parallel to the polarizer angle, the structural unit displays the corresponding structural color, i.e., the corresponding structural color is assigned a value of 1; when a structural unit does not contain micro / nano structure modules whose major axis is parallel to the polarizer angle, the structural unit does not display the corresponding structural color, i.e., the corresponding structural color is assigned a value of 0. Based on this differentiated response of the metasurface micro / nano structure to the polarization of incident light, a correspondence between pixel information in the binary image and whether the structural unit contains the corresponding micro / nano structure module is constructed, as shown in Table 1. The "Unit Structure" column displays top views of different unit structures, with dashed boxes representing the boundaries of a unit structure, and gray rectangles representing different modules. Furthermore, through information encoding, the corresponding micro / nano structures are selected to construct a triple optical multiplexing metasurface.

[0039] Table 1. Comparison Table of Information Encoding and Unit Structure

[0040]

[0041] Step 3: By changing the polarization angle of the incident linearly polarized light, the three information channels based on the polarization-modulated plasmonic metasurface are read, and three different images are displayed.

[0042] The following is a specific embodiment to verify the effectiveness of the triple optical information multiplexing method of the present invention.

[0043] First, metasurface optical devices were fabricated based on the optimized size parameters of the three micro / nano structure modules. The ITO glass substrate was ultrasonically cleaned for 10 min sequentially using acetone, ethanol, and deionized water. Then, aluminum was deposited on the substrate to a thickness of 50 nm; followed by SiO2 deposition to a thickness of 50 nm; then aluminum deposition again to a thickness of 50 nm; finally, photoresist was spin-coated, and the designed metasurface pattern (e.g., ...) was created using an electron beam lithography system. Figure 2 The process involves several steps: first, exposure to transfer the designed structural pattern onto photoresist; then, etching of the photoresist; followed by etching of aluminum to a depth of 50 nm; then etching of SiO2 to a depth of 50 nm; and finally, etching of aluminum to a depth of 50 nm. The remaining photoresist is then removed. Ultimately, through this series of micro-nano fabrication processes, a metasurface optical device with triple QR code multiplexing is fabricated.

[0044] Next, the metasurface optical testing optical path is constructed. Based on the device's designed function, the required device testing optical path diagram is as follows: Figure 3 As shown, a white light source with a color temperature of 6000K is imaged by a convex lens, then becomes a high-energy point light source through a micro-aperture. The beam is then collimated by another convex lens, and the spot size is reduced by an aperture. Next, the light passes through a semi-transparent mirror, and the reflected light wave is incident directly onto the polarization-modulated metasurface optical device. In reflection mode, after reflection by the polarization-modulated metasurface optical device, the light wave passes sequentially through the semi-transparent mirror and a lens before entering the detector. In transmission mode, after transmission by the polarization-modulated metasurface optical device, the light wave passes through the lens before entering the detector.

[0045] Finally, the metasurface was tested. First, the polarization-modulated metasurface was placed in an optical testing system. By rotating a linear polarizer to change the polarization angle of the light wave, the transmitted QR code images were tested under different incident light polarization angles. When the light wave polarization angles were 0°, 60°, and 120°, the corresponding QR code patterns displayed different colors. The R component of the transmitted color QR code under 0° polarization, the G component under 60° polarization, and the B component under 120° polarization were taken, and the QR code was successfully scanned using a mobile phone, revealing the information contained within the QR code.

[0046] Similarly, a polarization-modulated metasurface was placed in an optical testing system. By rotating a linear polarizer to change the polarization angle of the light wave, the reflected QR code images under different incident light polarization angles were tested. When the light wave polarization angles were 0°, 60°, and 120°, the corresponding QR code patterns displayed different colors. The R component of the reflected color QR code under 0° polarization, the G component of the reflected color QR code under 60° polarization, and the B component of the reflected color QR code under 120° polarization were taken, and the QR code was successfully scanned using a mobile phone, revealing the information contained in the QR code.

[0047] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for triple optical information multiplexing based on polarization-modulated plasmonic metasurfaces, characterized in that, The polarization-modulated plasmonic metasurface includes a substrate and structural units arranged in a square periodic pattern on the substrate. Each structural unit includes three micro / nano structural modules, and the major axes of the three micro / nano structural modules are placed along 0°, 60° and 120°, respectively. The triple optical information multiplexing method includes the following steps: Step 1: Use electromagnetic simulation tools to calculate the optical response of the structural unit, set the working wavelength range, and optimize the size parameters of the three micro-nano structural modules in the structural unit so that the spectral response positions of the three micro-nano structural modules are located in the blue, green and red bands respectively, thereby constructing three information channels along three directions; Step 2: Design blue, green and red binary patterns, and convert their binary information into selection of all or part of the micro-nano structure modules in the structural unit, so that each of the three information channels displays a binary pattern of a different color, thereby completing the design and construction of the metasurface; Step 3: By changing the polarization angle of the incident linearly polarized light, the three information channels based on the polarization-modulated plasmonic metasurface are read, and three different images are displayed.

2. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 1, characterized in that, Step one specifically includes the following sub-steps: (1.1) Arrange structural units in a periodic square pattern on the substrate, with the vertex of one structural unit as the origin. The two directions of the periodic square are the x-axis and y-axis, respectively. The angle between the square and the positive x-axis is defined as the placement direction of the micro / nano structure module. (1.2) Arrange a micro / nano structure module with a placement direction of 0° in each structural unit. Linearly polarized light polarized along the 0° direction and linearly polarized light polarized along the 90° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light and obtains the spectral position of the two linearly polarized light beams in the wavelength band. Adjust the size of the micro / nano structure module so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 0° direction is located in the blue, green or red wavelength band; (2) there is no structural color response to the incident linearly polarized light polarized along the 90° direction. Similarly, a micro / nano structure module with a placement direction of 60° is arranged in each structural unit. Linearly polarized light polarized along the 60° direction and linearly polarized light polarized along the 150° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light, and the spectral positions of the two linearly polarized light beams are obtained. The size of the micro / nano structure module is adjusted so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 60° direction is located in one of the two other primary colors that are different from the reflection spectral position of the micro / nano structure module with a placement direction of 0°; (2) there is no structural color response to the incident linearly polarized light polarized along the 150° direction. Similarly, a micro / nano structure module with a placement direction of 120° is arranged in each structural unit. Linearly polarized light polarized along the 120° direction and linearly polarized light polarized along the 30° direction are incident from above the micro / nano structure module, respectively, so that the micro / nano structure module generates a spectral response to the linearly polarized light, and the spectral positions of the two linearly polarized light beams are obtained. The size of the micro / nano structure module is adjusted so that it simultaneously satisfies: (1) the reflection spectral position of the linearly polarized light polarized along the 120° direction is located in a different band of the three primary colors than the reflection spectral positions of the micro / nano structure modules with placement directions of 0° and 60°; (2) there is no structural color response to the incident linearly polarized light polarized along the 30° direction.

3. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 1, characterized in that, In step two, binary patterns of blue, green, and red are designed, and their binary information is converted into rules for selecting all or part of the micro / nano structural modules in the structural unit, as follows: When a structural unit contains a micro / nano structure module whose major axis is parallel to the angle of the polarizer, the structural unit displays the corresponding structural color, i.e., the corresponding structural color is assigned a value of 1; when a structural unit does not contain a micro / nano structure module whose major axis is parallel to the angle of the polarizer, the structural unit does not display the corresponding structural color, i.e., the corresponding structural color is assigned a value of 0. This allows us to establish a correspondence between pixel information in a binary image and whether the structural unit contains the corresponding micro / nano structure module.

4. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 1, characterized in that, The micro / nano structure module has a three-layer structure, consisting of a metal layer, a dielectric layer, and a metal layer from top to bottom.

5. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 1, characterized in that, The micro / nano structure module is a cuboid.

6. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 1, characterized in that, The substrate is made of an optically transparent medium material.

7. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 4, characterized in that, The material of the metal layer is selected from materials that have good plasmon response in the visible light band, including aluminum, gold, and silver; the material of the dielectric layer is selected from any one of silicon dioxide, aluminum oxide, and magnesium fluoride.

8. The triple optical information multiplexing method based on polarization-modulated plasmonic metasurfaces according to claim 1, characterized in that, The operating mode of the polarization-modulated plasmonic metasurface is either reflective or transmissive.

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