A method of implementing a metasurface hologram
By designing three nano-unit structures on a metasurface and encoding phase information, a color hologram is realized using polarized light incident light. This solves the problems of limited channel number and complex encoding in traditional metasurface holography, and achieves efficient decoupling and efficient information storage between near-field nanoimprinting and far-field color holography.
Patent Information
- Application Number
- CN202411791704.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-10-24
- Estimated Expiration
- 2044-12-06
AI Technical Summary
Traditional metasurface holography suffers from a limited number of channels, low holographic efficiency, and complex encoding, making it difficult to achieve efficient decoupling and crosstalk-free operation of near-field nanoimprinting and far-field color holography simultaneously.
Three nanounit structures are employed, which are periodically arranged in an array on a substrate. The phase information of the target hologram is encoded into the rotation angle of the nanobricks. Color holograms are realized by incident polarized light of different wavelengths. The nanobrick structure of the metal material is combined for modulation to achieve simultaneous decoupling of near-field nanoimprinting and far-field color holography.
This technology enables simultaneous decoupling of near-field nanoimprinting and far-field color holography on the same metasurface, reducing process steps, increasing information storage density, simplifying the encoding process, and avoiding channel crosstalk.
Smart Images
Figure CN119292023B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of micro-nano optical technology, and particularly relates to a method for realizing a metasurface hologram. BACKGROUND
[0002] A metasurface is an artificial two-dimensional material composed of subwavelength unit structures, which has strong control ability on electromagnetic waves. By optimizing the shape, size and arrangement of the unit structure, the amplitude, phase and electric field intensity of the electromagnetic field can be controlled. Traditional optical elements mainly accumulate optical path by making light beams pass through materials with different refractive indices, and then modulate, control and frequency convert the light beams, such as optical lenses, half-wave plates and nonlinear crystals. This control method has great limitations in small and precise optical systems, and optical metasurfaces are expected to be a breakthrough to solve this problem. On the other hand, metasurfaces can effectively control the wavefront of light in the subwavelength scale, which is conducive to the integration of optical systems.
[0003] With the advent of the information age, holographic technology has developed into computational holography. This technology combines computers with holographic technology, does not require an actual interference optical path, and directly uses a computer to calculate the amplitude and phase distribution of a hologram corresponding to a target image, and then uses an encoding device to control the wavefront. Since metasurfaces are relatively simple to prepare and have super strong modulation ability on electromagnetic waves, metasurfaces are widely used as encoding devices in holographic technology.
[0004] However, traditional metasurface holographic technology has the disadvantages of few channels, low holographic efficiency, complex encoding, etc. SUMMARY
[0005] (I) Technical problems to be solved
[0006] In view of the above problems, the main purpose of the present application is to provide a method for realizing a metasurface hologram, which uses a simple encoding method to realize near-field nanoimprinting and far-field color holography at the same time on the same metasurface, and is completely decoupled, without crosstalk between the two channels, thereby reducing the process manufacturing steps and flow.
[0007] (II) Technical solutions
[0008] In order to achieve the above-mentioned purpose, the application provides a method for realizing a metasurface hologram, comprising: presetting three kinds of nano-unit structures, wherein the geometric size and geometric shape of the three kinds of nano-unit structures are different, and each kind of nano-unit structure comprises a nano-brick; arranging the three kinds of nano-unit structures in an array cycle on a preset substrate according to a preset target near-field diagram; encoding the phase information of a processed target far-field hologram into the rotation angle of the nano-brick of each kind of nano-unit structure arranged to complete the construction of the metasurface; and realizing a color hologram in the far-field region of the metasurface by setting a polarized light of different wavelengths to be incident to the metasurface.
[0009] In the above-mentioned scheme, the color hologram in the far-field region of the metasurface is realized by setting a polarized light of different wavelengths to be incident to the metasurface, and further comprising: realizing a color nano-imprint in the near-field region of the metasurface.
[0010] In the above-mentioned scheme, the presetting of the three kinds of nano-unit structures further comprises: scanning each kind of nano-unit structure, and determining the geometric size and geometric shape of the nano-brick in each kind of nano-unit structure according to the polarization conversion rate of the nano-unit structure to incident light.
[0011] In the above-mentioned scheme, when three colors of light are incident, each kind of nano-unit structure of the three kinds of nano-unit structures only produces high reflectivity reflection to a single color of light, and does not produce reflection to the other two colors of incident light.
[0012] In the above-mentioned scheme, the encoding of the phase information of the processed target far-field hologram into the rotation angle of the nano-brick in each kind of nano-unit structure to complete the construction of the metasurface comprises: extracting the phase information of the preset target far-field hologram, and performing region division and sampling processing on the phase information; and encoding the phase information of the processed target far-field hologram into the rotation angle of the nano-brick in each kind of nano-unit structure to construct the metasurface.
[0013] In the above-mentioned scheme, the color hologram in the far-field region of the metasurface is realized by setting a polarized light of different wavelengths to be incident to the metasurface, wherein: the polarization type of the incident light is left-handed circularly polarized light; and the working region of the metasurface is a reflection region.
[0014] In the above-mentioned scheme, the color hologram in the far-field region of the metasurface is realized by setting a polarized light of different wavelengths to be incident to the metasurface, comprising: modulating the amplitude of the incident light by anisotropic nano-bricks to realize a color nano-imprint; and modulating the phase of the incident light to realize a color hologram.
[0015] In the above-mentioned scheme, the metasurface comprises a substrate and three kinds of nano-unit structures distributed on the substrate in a periodic arrangement.
[0016] The substrate of the super surface comprises an Al film bottom layer and a SiO2 top layer; and the nano bricks comprise Al and Ag.
[0017] In the above scheme, the nano bricks of different sizes have different reflection spectra; and when white light is used for incidence, the nano bricks of different sizes display different colors.
[0018] (Three) beneficial effects
[0019] The technical scheme of the embodiment of the application has at least the following beneficial effects:
[0020] (1) The method uses metal materials to form three kinds of nano unit structures, and uses the geometric size, shape and metal material of the unit structure as the amplitude factor of modulating the near field, and uses the rotation angle of the unit structure as the phase factor of modulating the far field, so that the same super surface can realize near-field nano imprinting and far-field color holography at the same time, and is completely decoupled, and there is no crosstalk between the two channels.
[0021] (2) The method can realize color holography in a simple encoding manner, increase the information storage density, and the nano brick structure is simple, and a large array is easy to manufacture, thereby greatly reducing the process manufacturing steps and processes. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 A flowchart of a method for realizing a super surface hologram according to an embodiment of the application is schematically shown;
[0023] Figure 2 A target pattern of color nano printing and color holography according to an embodiment of the application is schematically shown;
[0024] Figure 3 A structural diagram of a super surface according to an embodiment of the application is schematically shown;
[0025] Figure 4a A diagram showing the change of cross-polarized light reflectivity of three kinds of unit cell structures at different rotation angles according to an embodiment of the application is schematically shown;
[0026] Figure 4b A diagram showing the change of phase mutation of three kinds of unit cell structures at different rotation angles according to an embodiment of the application is schematically shown;
[0027] Figure 5 A process diagram of realizing color nano imprinting and color hologram according to an embodiment of the application is shown;
[0028] Figure 6 A far-field result diagram and a near-field result diagram according to an embodiment of the application are schematically shown. DETAILED DESCRIPTION
[0029] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific embodiments and drawings.
[0030] Figure 1 A flow chart of a method for implementing a metasurface hologram according to an embodiment of the present application is schematically shown.
[0031] As shown in Figure 1 , in an embodiment of the present application, the method for implementing a metasurface hologram further comprises operations S1-S4.
[0032] In operation S1, three kinds of nano-unit structures are preset, wherein the three kinds of nano-unit structures are different in geometric size and geometric shape, and each kind of nano-unit structure comprises a nano-brick.
[0033] In an embodiment of the present application, three kinds of nano-unit structures are first preset, for example, three kinds of nano-unit structures with different geometric size and geometric shape can be designed by using MIM (metal-dielectric-metal) structure.
[0034] Further, each kind of nano-unit structure is scanned, and the geometric size and geometric shape of the nano-brick in each kind of nano-unit structure are determined according to the polarization conversion rate of the nano-unit structure to incident light. For example, when a simulation method is used, a target metasurface simulation unit structure, i.e. a nano-unit structure, is first determined, and then the geometric size of the nano-brick is scanned, and the appropriate geometric shape and geometric size of the nano-brick are selected according to the polarization conversion rate of the nano-brick to incident light.
[0035] In an embodiment of the present application, for the three kinds of different nano-unit structures, when three colors of light are incident, each kind of nano-unit structure among the three kinds of nano-unit structures only produces high reflectivity reflection to a single color of light, and does not produce reflection to the other two colors of incident light.
[0036] In an embodiment of the present application, nano-bricks of different sizes have different reflection spectra; and when white light is used for incidence, nano-bricks of different sizes display different colors.
[0037] Specifically, nano-bricks of different sizes have different reflection spectra, and when white light is used for incidence, the wavelengths at which the reflection spectra of nano-bricks of different sizes are strongest are different, resulting in that the nano-bricks display different colors.
[0038] In operation S2, according to the preset target near-field pattern, the three kinds of nano-unit structures are periodically arranged in an array on a preset substrate.
[0039] In operation S3, the phase information of the processed target far-field hologram is encoded into the rotation angle of the nano-brick of each kind of nano-unit structure after arrangement, so as to complete the construction of the metasurface.
[0040] Exemplarily, a periodic arrangement of a large array of three kinds of nano-brick unit structures on a substrate is determined according to a preset target near-field pattern.
[0041] Specifically, first, phase information of a preset target far-field hologram is extracted, and the phase information is regionally divided and sampled, and then the processed phase information of the target far-field hologram is encoded into a rotation angle of a nano brick in each kind of nano unit structure to complete construction of the metasurface.
[0042] Figure 2 Schematically show a color nano printing and color holographic target pattern according to an embodiment of the present application.
[0043] As shown in Figure 2 , based on the preset color nano printing and color holographic target pattern, the metasurface is constructed. As shown in Figure 2 , the color nano printing and color holographic target pattern are both composed of RGB three primary colors. The pattern as shown in Figure 2 a is divided into three pictures according to the three primary colors, so that each picture is composed of only one color of the three primary colors, and the picture pixel size is adjusted to 100x100. The pixels of the picture with the pattern are filled with a corresponding color of nano bricks, so the size of the nano brick array is also 100x100.
[0044] Further, the phase information contained in the target hologram (as shown in Figure 2 b) is extracted, and the phase information of the metasurface is obtained by using Fourier transform and inverse Fourier transform. Half of the phase information is the included angle between the metasurface unit and the z-axis.
[0045] In an embodiment of the present application, the metasurface includes a substrate and three kinds of nano unit structures distributed on the substrate in a periodic arrangement. The substrate of the metasurface includes an Al film bottom layer and a SiO2 top layer; the nano bricks include Al and Ag, for example, the nano bricks are composed of Al or Ag.
[0046] Figure 3 Schematically show a structure diagram of the metasurface according to an embodiment of the present application.
[0047] As shown in Figure 3 , Figure 3 including 3 metasurfaces containing different nano unit structures, respectively, metasurface 31, metasurface 32 and metasurface 33.
[0048] Please continue to refer to Figure 3The metasurface 31 is composed of a substrate 311 and nanobricks 312 stacked from bottom to top. The substrate 311 is composed of an Al layer and a SiO2 layer, a transparent optical material. The operating wavelength of the metasurface 31 is 632 nm. The nanobricks 312 are parallelogram-shaped columns with angles of 45° or 135° between adjacent sides. Made of Al, the nanobricks 312 are embedded within the SiO2 layer, with their top surfaces flush with the top surface of the SiO2 layer.
[0049] Please continue reading Figure 3 The metasurface 32 is composed of a substrate 321 and nanobricks 322 stacked from bottom to top. The substrate 321 is composed of an Al layer and a SiO2 layer, a transparent optical material. The metasurface 32 operates at a wavelength of 576 nm. The nanobricks 322 are rectangular columns made of Al and embedded within the SiO2 layer. The top surface of the nanobricks 322 is flush with the top surface of the SiO2 layer.
[0050] Please continue reading Figure 3 The metasurface 33 is composed of a substrate 331 and nanobricks 332 stacked from bottom to top. The substrate 331 is composed of an Al layer and a SiO2 layer, a transparent optical material. The operating wavelength of the metasurface 33 is 476 nm. The nanobricks 332 are parallelogram-shaped columns with angles of 45° or 135° between adjacent sides. The nanobricks 332 are made of Al and are embedded within and located on the SiO2 layer.
[0051] Figure 4a The diagram schematically shows the change in cross-polarized light reflectivity of three unit cell structures at different rotation angles according to an embodiment of the present invention. Figure 4b Schematically illustrating the changes in phase mutations of three unit cell structures at different rotation angles according to an embodiment of the present invention.
[0052] As shown in FIG4 , FIG4 is a graph showing the changes in the cross-polarized light reflectivity and phase mutation of the three unit cell structures used in the examples of the present invention at different rotation angles. Figure 4a As shown, in order to select a suitable nanobrick unit cell structure (a metasurface unit structure containing only a single nanobrick), the thickness of the substrate layer is fixed, for example, the thickness of the Al layer is determined to be 40nm, and the thickness of the silicon dioxide layer is determined to be 200nm. By scanning the length and width of the nanobrick, the values with the highest reflectivity of the incident light and the cross-polarization conversion efficiency are selected as the nanobrick unit cell structure, and finally the unit cell size is determined.
[0053] Furthermore, by changing the angle between the long axis of the nanobrick and the z-axis, the phase mutation value of the nanobrick to polarized light passing through the metasurface is calculated, such as Figure 4bAs shown, the phase mutation value and the rotation angle of the nano brick are linearly changed, and the PB phase modulation requirement is met, wherein each nano brick pattern corresponds to one of the three primary colors.
[0054] In operation S4, by setting the polarized light of different wavelengths to be incident to the metasurface, a color hologram is realized in the far-field region of the metasurface.
[0055] It should be noted that by setting the polarized light of different wavelengths to be incident to the metasurface, a color hologram is realized in the far-field region of the metasurface, and the color nanoimprint is realized in the near-field region of the metasurface.
[0056] Figure 5 A process diagram for realizing the color nanoimprint and the color hologram according to an embodiment of the present application is shown.
[0057] As shown in the embodiment of the present application, the polarization type of the incident light is left-handed circularly polarized light; and the working region of the metasurface is a reflection region. Figure 5
[0058] For example, the metasurface is irradiated with three kinds of left-handed circularly polarized light of different wavelengths, the metasurface model is simulated, the reflected light will appear a color nanoimprint pattern on the metasurface, and a color hologram image is displayed on the design distance plane.
[0059] Specifically, by adjusting the rotation angle of the nano unit structure, the amplitude of the three kinds of left-handed circularly polarized light of different wavelengths is modulated by the anisotropic nano brick, the color nanoimprint is realized in the near-field region, and the two channels are independent and have no crosstalk; and by modulating the phase of the incident light, the color hologram is realized in the far-field region of the metasurface.
[0060] Figure 6 The far-field result and the near-field result according to an embodiment of the present application are schematically shown.
[0061] As shown in the embodiment of the present application, the metasurface constructed through the above steps contains information of the far-field and near-field target patterns, and the metasurface is irradiated with laser of working wavelength, so that the far-field and near-field light fields can be reconstructed. Figure 6 Figure 6 As shown, the far field is a simulation result at a distance of 0.3 mm from the metasurface, and the near field is a simulation result at a distance of one wavelength from the metasurface.
[0062] By the embodiments of the present disclosure, a double-layer metasurface hologram based on PB phase is realized to realize color holography and nanoimprinting, three kinds of nano unit structures are formed by metal materials, the geometric size, shape and metal material constituting the nano brick of the unit structure are taken as the amplitude factors of the near field modulation, and the rotation angle of the unit structure is taken as the phase factor of the far field modulation, so that the same metasurface can realize near field nanoimprinting and far field color holography at the same time, and is completely decoupled, and there is no crosstalk between the two channels. The method can realize color holography and increase the information storage density in a simple encoding manner; the nano brick structure is simple, and a large array is easy to manufacture, thereby greatly reducing the process manufacturing steps and processes.
[0063] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above are only specific embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method of implementing a metasurface hologram, characterized by, The method comprises: three kinds of preset nano-unit structures, wherein the three kinds of nano-unit structures are different in geometric size and geometric shape, and each of the nano-unit structures comprises a nano-brick; arranging the three kinds of nano-unit structures in an array periodically on a preset substrate according to a preset target near-field pattern; encoding phase information of a processed target far-field hologram into a rotation angle of the nano-brick of each of the nano-unit structures to complete construction of the metasurface; realizing a color hologram in a far-field region of the metasurface by setting polarized light of different wavelengths to be incident to the metasurface.
2. The method of implementing a metasurface hologram of claim 1, wherein, The realizing of the color hologram in the far-field region of the metasurface by setting polarized light of different wavelengths to be incident to the metasurface further comprises: realizing a color nano-imprint in a near-field region of the metasurface.
3. The method of implementing a metasurface hologram of claim 1, wherein, The three kinds of preset nano-unit structures further comprise: scanning each of the nano-unit structures and determining the geometric size and geometric shape of the nano-brick in each of the nano-unit structures according to a polarization conversion rate of the nano-unit structure to incident light.
4. The method of implementing a metasurface hologram according to claim 1 or 3, wherein, When light of three colors is incident, each of the three kinds of nano-unit structures only produces high reflectivity reflection to monochromatic light of a certain color and does not produce reflection to incident light of the other two colors.
5. The method of implementing a metasurface hologram according to claim 1 or 3, wherein, The encoding of the phase information of the processed target far-field hologram into the rotation angle of the nano-brick in each of the nano-unit structures to complete construction of the metasurface comprises: extracting phase information of a preset target far-field hologram and performing region division and sampling processing on the phase information; encoding the phase information of the processed target far-field hologram into the rotation angle of the nano-brick in each of the nano-unit structures to construct the metasurface.
6. The method of implementing a metasurface hologram of claim 1, wherein, The realizing of the color hologram in the far-field region of the metasurface by setting polarized light of different wavelengths to be incident to the metasurface, wherein: the polarization type of the incident light is left-handed circularly polarized light; and the working region of the metasurface is a reflection region.
7. The method of implementing a metasurface hologram of claim 2 or 6, wherein, The realizing of the color hologram in the far-field region of the metasurface by setting polarized light of different wavelengths to be incident to the metasurface comprises: realizing a color nano-imprint by modulating the amplitude of the incident light by the anisotropic nano-brick; and realizing a color hologram by modulating the phase of the incident light.
8. The method of implementing a metasurface hologram of claim 5, wherein, The metasurface comprises a substrate and three kinds of nano-unit structures distributed on the substrate in a periodic arrangement.
9. The method of implementing a metasurface hologram of claim 8, wherein, The substrate of the metasurface comprises an Al thin film bottom layer and a SiO2 top layer; and the nano-brick comprises Al and Ag.
10. The method of implementing a metasurface hologram of claim 3, wherein, Nano-bricks of different sizes have different reflection spectra; and when white light is used for incidence, the nano-bricks of different sizes display different colors.