A polarization-modulated metasurface bidirectional color filtering device

Abstract

The application discloses a polarization-modulated super surface bidirectional color filter device, which can work in reflection and transmission modes simultaneously. The super surface bidirectional color filter device comprises a substrate and a super surface array structure on the substrate, the super surface array structure comprises structural units arranged periodically, and the structural units are composed of a plurality of micro-nano structure modules arranged in different directions. The substrate is a transparent dielectric substrate. The application increases the color modulation range of the existing polarization modulation device, can realize full-color color filtering effect, has the advantages of large color gamut modulation range, and the device can realize full-color modulation in the reflection mode and the transmission mode simultaneously, realizes red, green and blue three primary colors in the reflection direction, and realizes blue-green, magenta and yellow three primary colors in the transmission direction, so that the application prospect of the polarization-modulated super surface bidirectional color filter device is expanded.

Description

A polarization-modulated metasurface bidirectional color filter device Technical Field

[0001] This invention relates to the field of micro-nano optics, and in particular to a polarization-modulated metasurface bidirectional color filter device. 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 modulation effects can be achieved, such as controlling light wave reflection, transmission intensity, and phase. Among these, polarization-modulated metasurface structured color devices operate by utilizing the differentiated response characteristics of the modules constituting the metasurface structural unit to the polarization angle of light waves. By changing the polarization angle of the incident linearly polarized light, the optical response is modulated, thereby producing modulation of color response and filtering effects.

[0003] Most existing polarization modulation metasurface devices utilize mutually perpendicular modules as the structural units of the metasurface, with the two mutually perpendicular modules having different dimensional parameters, or employing array structures with different periods in mutually perpendicular directions to achieve differentiated responses to mutually perpendicular linearly polarized light, as shown in Figure 1. Therefore, metasurface devices can only achieve variations between two modulation properties, corresponding to light wave polarization along two characteristic dimensional directions. For color filtering devices, such devices can modulate two colors and their mixtures, but cannot achieve full-color modulation.

[0004] In summary, existing polarization-modulated metasurface structure color devices cannot simultaneously realize the three primary colors of RGB (red, green, and blue) or CMY (cyan, magenta, and yellow), thus having the disadvantage of a small color gamut modulation range. In general, they can only work in reflection mode or transmission mode alone, and cannot generate wide color gamut modulation in both reflection and transmission directions at the same time, which limits their possibilities in practical applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a polarization-modulated metasurface bidirectional color filter device. This device can increase the color gamut modulation range of existing polarization-modulated metasurface color filters and simultaneously achieve full-color modulation in both reflection and transmission modes.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A polarization-modulated metasurface bidirectional color filter device, the metasurface bidirectional color filter device being able to operate simultaneously in reflection and transmission modes;

[0008] The metasurface bidirectional color filter device includes a substrate and a metasurface array structure located on the substrate. The metasurface array structure comprises structural units arranged periodically. Each structural unit includes multiple micro / nano structure modules placed along three different directions. The included angle between adjacent directions is not less than 45°. The substrate is a transparent dielectric substrate.

[0009] To achieve a full-color polarization modulation device, the metasurface needs to generate three primary colors. These can be the RGB primary colors (red, green, and blue) or the CMY primary colors (blue-green, magenta, and yellow), corresponding to three cases where the incident light polarization angles differ by 60°. Because a single module can only generate one color in one direction, multiple micro / nanostructure modules need to be placed along three different directions to generate three colors, with the angle between adjacent directions not less than 45° to reduce interference between adjacent modules.

[0010] Furthermore, to achieve strong interaction between light and the micro / nano structure, 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, with the dielectric layer located between the two metal layers.

[0011] Furthermore, the metasurface array structure is a square periodic arrangement. Other array structures, such as triangular periodic arrangements, can also be selected.

[0012] Furthermore, the structural unit consists of three micro / nano structure modules placed in different directions. The number of micro / nano structure modules is not limited to three; it can be more than three. When there are more than three, multiple modules can be placed in the same direction.

[0013] Furthermore, the metal layer is made of a material that has a plasmonic response in the visible light band, such as aluminum, gold, or silver; the dielectric layer is made of any one of the transparent dielectric materials silicon dioxide, aluminum oxide, or magnesium fluoride.

[0014] Furthermore, the metal layer is made of aluminum, and the dielectric layer is made of silicon dioxide, a transparent dielectric material.

[0015] Furthermore, in order to enable the module to have a polarization-dependent structural color response, the micro / nano structure module has a shape with different characteristic dimensions in mutually perpendicular directions, such as a cuboid or an ellipse stretched along a direction perpendicular to the substrate.

[0016] Furthermore, the micro-nano structure module is a cuboid, and the major axes of the three micro-nano structure modules are placed along the directions of 0°, 75°, and 120°, respectively.

[0017] In selecting the module dimensions, the optical response along the long axis must be in the visible light band, while the optical response along the short axis must be outside the visible light band, thus enabling polarization-dependent structural color modulation. In one feasible embodiment, after optimization, the thicknesses of the silicon dioxide layer and the metal layer are equal, both 50 nm; the lengths of the three micro / nano structure modules are 210 nm, 125 nm, and 100 nm, respectively, and the widths are 60 nm, 70 nm, and 60 nm, respectively. Using these dimensions allows the structure to produce full-color filtering effects in both the reflection and transmission directions.

[0018] Furthermore, the material of the substrate is selected from any one of the transparent dielectric materials glass, magnesium fluoride, and aluminum oxide.

[0019] The beneficial effects of this invention are as follows:

[0020] The polarization-modulated metasurface bidirectional color filter device of this invention utilizes modular design and the principle of polarization modulation to design the metasurface device, breaking through the traditional mutually perpendicular module layout. By using multiple modules with different orientations to form a metasurface, the color modulation range of existing polarization modulation devices can be increased, achieving full-color color filtering effect. It has the advantage of a large color gamut modulation range, and the device can simultaneously achieve full-color modulation in both reflection and transmission modes. It achieves the three primary colors of red, green, and blue in the reflection direction and the three primary colors of blue-green, magenta, and yellow in the transmission direction, thus expanding the application prospects of polarization-modulated metasurface bidirectional color filter devices. Attached Figure Description

[0021] Figure 1 shows two typical array structures of polarization-modulated metasurface devices in the background technology. The left figure shows arrays with the same period but different sizes of structural units in two perpendicular directions, while the right figure shows arrays with different periods in mutually perpendicular directions.

[0022] Figure 2 is a schematic diagram of a metasurface array design according to one embodiment of the present invention.

[0023] Figure 3 is a schematic diagram of the structure of a polarization-modulated metasurface bidirectional color filter device according to one embodiment of the present invention, wherein 1 represents aluminum and 2 represents silicon dioxide.

[0024] Figure 4 is a device test optical path diagram of one embodiment of the present invention.

[0025] Figure 5 shows the reflection spectrum of the polarization-modulated metasurface structured color device under different incident light polarization angles.

[0026] Figure 6 shows the CIE1931 chromatogram (reflection) of polarization-modulated metasurface structured color devices under different incident light polarization angles.

[0027] Figure 7 shows the transmission spectra of polarization-modulated metasurface structured color devices under different incident light polarization angles.

[0028] Figure 8 shows the CIE1931 chromatogram (transmission) of polarization-modulated metasurface structured color devices under different incident light polarization angles. Detailed Implementation

[0029] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0030] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0031] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0032] The following two embodiments of polarization-modulated metasurface bidirectional color filter devices include a substrate and a metasurface array structure located on the substrate. The metasurface array structure contains structural units arranged in a square periodic pattern. Each structural unit is composed of three micro / nano structure modules placed in different directions. It can operate in both reflection and transmission modes simultaneously.

[0033] In this embodiment, the materials used to fabricate the metasurface micro / nanostructure are aluminum and silicon dioxide, and the substrate is glass. The design uses cuboid modules arranged in three different directions to form the metasurface structural unit, with the structural units arranged in a square periodic pattern to form the metasurface. This design utilizes the characteristic that the resonance mode of the anisotropic modules is related to the polarization angle of the incident light wave. By placing modules in three directions, differentiated responses to linearly polarized light at three polarization angles are achieved, thus generating the three primary colors of light. The structural unit and array structure of the designed metasurface structural color device are shown in Figure 2. The structural unit consists of three modules with different orientations, and the array structure is a square periodic structure. When the polarization angle of the incident linearly polarized light is rotated, the metasurface achieves different optical responses in the orientation directions of the three modules, exhibiting three different colors and their mixtures. Therefore, full-color modulation can be obtained by optimizing the metasurface micro / nanostructure. The specific implementation steps of this device are as follows:

[0034] First, the ITO glass substrate was ultrasonically cleaned for 10 minutes sequentially using acetone, ethanol, and deionized water. Then, aluminum was deposited on the substrate to a thickness of 50 nm. Following this, SiO2 was deposited to a thickness of 50 nm. Next, photoresist was spin-coated and exposed using an electron beam lithography system to transfer the designed structural pattern onto the photoresist. Next, the photoresist was etched, followed by etching of the aluminum to a depth of 50 nm. Then, SiO2 was etched to a depth of 50 nm. Finally, residual photoresist was removed. The resulting optical metasurface micro / nano structure, fabricated through this series of micro / nano fabrication processes, is shown in Figure 3.

[0035] Optical testing was performed on the device in this embodiment. The required optical path diagram for the device test, based on its designed function, is shown in Figure 4. A white light source with a color temperature of 6000K is imaged by a convex lens, then passes through a micro-aperture to form a high-energy point light source. 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 passing through the polarization-modulated metasurface optical device, the light wave passes through the lens before entering the detector.

[0036] In the reflection mode test, firstly, the polarization modulation metasurface prepared in this embodiment was placed in an optical testing system. The polarization angle of the light wave was changed by rotating a linear polarizer, and the reflection spectrum was tested under different incident light polarization angles, as shown in Figure 5. When the light wave polarization angle was deflected counterclockwise from 0° to 180°, the corresponding reflection peak in the reflection spectrum changed, with three different reflection peaks appearing in succession, as shown in Figure 5. Then, the detector was replaced with a CCD, and the reflected color image of the device under different incident light polarization angles was measured. As the incident light polarization angle changed, the trajectory of the reflected color on the CIE 1931 chromaticity diagram is shown in Figure 6. It first appears as red, then green, and then gradually changes to blue. All three primary colors (red, green, and blue) can be achieved by adjusting the incident light polarization angle. On the CIE 1931 chromaticity diagram, the colors corresponding to different light wave polarization angles change counterclockwise along a circular trajectory around the white point, indicating that the device can achieve full-color modulation in reflection mode.

[0037] In the transmission mode test, the polarization-modulated metasurface was first placed in the optical testing system. The polarization angle of the light wave was changed by rotating a linear polarizer, and the reflection spectrum was measured under different incident light polarization angles, as shown in Figure 5. When the light wave polarization angle was deflected counterclockwise from 0° to 180°, the corresponding transmission valley in the transmission spectrum changed, with three different transmission valley regions appearing, as shown in Figure 7. Then, the detector was replaced with a CCD, and the transmission color image of the device under different incident light polarization angles was measured. As the incident light polarization angle changed, the observed trajectory of the device's transmission color on the CIE 1931 chromaticity diagram is shown in Figure 8. It first appears as cyan, then magenta, and then gradually changes to yellow. All three primary colors in CMY can be achieved by adjusting the incident light polarization angle. On the CIE 1931 chromaticity diagram, the colors corresponding to different light wave polarization angles change counterclockwise along a circular trajectory around the white point, indicating that the device can achieve full-color modulation in transmission mode.

[0038] 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 polarization-modulated metasurface bidirectional color filter device, characterized in that, The metasurface bidirectional color filter device can simultaneously achieve full-color modulation in both reflection and transmission modes, realizing the three primary colors of red, green, and blue in the reflection direction, and the three primary colors of blue-green, magenta, and yellow in the transmission direction. The metasurface bidirectional color filter device includes a substrate and a metasurface array structure located on the substrate. The metasurface array structure comprises periodically arranged structural units, each structural unit including multiple micro / nano structure modules placed along three different directions, with the included angle between adjacent directions not less than 45°. The substrate is a transparent dielectric substrate. The micro / nano structure module has a three-layer structure, consisting of a metal layer, a dielectric layer, and another metal layer from top to bottom, with the dielectric layer located between the two metal layers. The micro / nano structure module is a cuboid, with its major axes positioned at 0°, 75°, and 120°, respectively. The module has shapes with different characteristic dimensions in mutually perpendicular directions. The dielectric and metal layers have equal thicknesses of 50 nm. The lengths of the three micro / nano structure modules are 210 nm, 125 nm, and 100 nm, respectively, and their widths are 60 nm, 70 nm, and 60 nm, respectively.

2. The polarization-modulated metasurface bidirectional color filter device according to claim 1, characterized in that, The metasurface array structure is a square periodic arrangement structure.

3. The polarization-modulated metasurface bidirectional color filter device according to claim 1, characterized in that, The metal layer is made of a material that has a plasmonic response in the visible light band, and the dielectric layer is made of any one of silicon dioxide, aluminum oxide, and magnesium fluoride.

4. The polarization-modulated metasurface bidirectional color filter device according to claim 1, characterized in that, The metal layer is made of aluminum, and the dielectric layer is made of silicon dioxide.

5. The polarization-modulated metasurface bidirectional color filter device according to claim 1, characterized in that, The substrate material is selected from any one of glass, magnesium fluoride, and aluminum oxide.

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