Three-dimensional vector holographic display device and display method based on medium metasurface

Abstract

The invention discloses a three-dimensional vector holographic display device based on a medium metasurface and a display method. The three-dimensional vector holographic display device comprises a substrate and a nano structure unit on the substrate, the nano-structure units are arranged on the substrate according to specific phase distribution to form a nano-structure unit array; when light waves enter the three-dimensional vector holographic display device, the light waves are modulated by the nanostructure units, transmitted light waves are emitted through a plurality of independent space channels, adjustable patterns of different polarization states can be generated on a plurality of planes in a combined mode, and three-dimensional vector display is achieved. According to the invention, longitudinal regulation and control of amplitude, phase and polarization of light waves can be realized in a broadband range, super-surface display is expanded to a three-dimensional vector form from a two-dimensional scalar form, and the method can be applied to the fields of high-capacity optical storage, optical information encryption, quantum optical technology and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanophotonics, and specifically relates to a three-dimensional vector holographic display device and display method based on a dielectric metasurface. Background Technology

[0002] In recent years, with the rapid development of applications such as optical data storage, secure information encryption, augmented / virtual reality optical capture, and volumetric microscopy imaging, the demand for precise manipulation of complex three-dimensional light fields has been increasing. As a fundamental technology for recording and reconstructing beam wavefronts, holography has significant advantages in three-dimensional visualization and volumetric light field control. However, traditional solutions based on digital spatial light modulators (SLMs), digital micromirror devices (DMDs), and bulk holographic media are often limited by system integration, efficiency, and the ability to control the light vector dimension, making it difficult to simultaneously control the intensity and polarization within the volume space, which severely restricts the realization of three-dimensional vector holography.

[0003] Thanks to the continuous development of nanofabrication technology, metasurfaces, as two-dimensional planar array structures composed of subwavelength artificial microstructure units, offer new solutions for the precise control of multiple optical field parameters such as phase, amplitude, polarization, and frequency. Due to their lightweight, miniaturization, high flexibility, and multi-dimensional wavefront tunability, metasurface-based image display devices have significant application value in optical display, storage, and encryption fields, offering advantages such as high performance, miniaturization, low power consumption, and high integration. Some metasurface-based scalar holography techniques, utilizing traditional Fourier and Fresnel holography, can reconstruct images on multiple planes along the axis, but crosstalk between different planes is severe. Other metasurface-based polarization holography research remains limited to two-dimensional vector holographic manipulation on a single projection plane. Therefore, achieving depth-dependent amplitude and polarization joint manipulation within a volumetric space with a certain depth, thereby realizing three-dimensional vector holographic projection, remains a significant challenge that urgently needs to be addressed. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a three-dimensional vector holographic display device and display method based on a dielectric metasurface.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a three-dimensional vector holographic display device based on a dielectric metasurface, the three-dimensional vector holographic display device comprising: a substrate and nanostructure units on the substrate; the nanostructure units are arranged on the substrate according to a specific phase distribution to form a nanostructure unit array; when light waves are incident on the three-dimensional vector holographic display device, after modulation by the nanostructure units, the transmitted light waves are emitted in multiple independent spatial channels, which can be combined on multiple planes to generate tunable patterns with different polarization states, thereby realizing three-dimensional vector display.

[0006] Furthermore, the substrate is made of a low-loss, low-refractive-index dielectric material, and the nanostructure units are made of a low-loss, high-refractive-index dielectric material or a semiconductor material.

[0007] Furthermore, the substrate material is made of transparent glass, calcium fluoride, barium fluoride, aluminum oxide, or infrared chalcogenide glass, and the nanostructure unit is made of titanium dioxide, hafnium dioxide, gallium nitride, silicon nitride, silicon, or germanium.

[0008] Furthermore, the vector light field distribution for three-dimensional vector display achieved by the nanostructure unit array conforms to equation (1):

[0009] (1)

[0010] in, This represents the distance between the propagation direction and the metasurface. This represents the plane containing the hypersurface in free space. This represents the spatial position vector of any point on the cross-section along the propagation direction, with corresponding coordinates as follows: The spatial channel location coordinates are Each spatial channel consists of left-handed and right-handed circular deflection channels. It is formed by the superposition of Bessel beams with the same frequency and equally spaced longitudinal wave vectors. It is a zero-order Bessel function. and The first and second circular deflection channels are respectively left-handed and right-handed. Complex amplitude coefficients of a Bessel beam To correspond to the longitudinal wave vector of the Bessel beam, To correspond to the radial wave vector of the Bessel beam, satisfying ,in For free space wave vectors.

[0011] Furthermore, the nanostructure unit array is composed of two groups of nanostructure units arranged at intervals to form a checkerboard pattern; the specific matrix response distribution realized by each group of nanostructure units conforms to equation (2):

[0012] (2)

[0013] in, and These are the left and right singular vector matrices obtained by performing singular value decomposition on the Jones matrix distribution at the normalized hypersurface, respectively. Complex values , , and From the singular value matrix diagonal elements ( and The result is obtained through transformation, i.e. and ,in Represents the position in the diagonal matrix ( ).

[0014] Furthermore, the ratio of the dielectric constant of the substrate to that of the nanostructure unit is 1:(1.2 to 3.7).

[0015] Furthermore, the nanostructure units are arranged in a quasi-periodic or periodic manner on the substrate. The side length of each periodic unit is P, where P is 0.5λ to λ. All nanostructure units have the same height H, where H is 0.4λ to λ, and λ is the wavelength of the incident light wave.

[0016] Furthermore, the cross-sectional shape of the nanostructure unit is rectangular, square, elliptical, or circular; when the cross-sectional shape of the nanostructure unit is rectangular, square, or elliptical, the size of its major and minor axes ranges from 0.2P to 0.8P; the angle between the major axis of the nanostructure unit and the x-axis is 0 to 180°; when the cross-sectional shape of the nanostructure unit is circular, the size of its radius ranges from 0.1P to 0.4P, where P is the period of the nanostructure unit.

[0017] A display method for a three-dimensional vector holographic display device based on a dielectric metasurface includes the following steps:

[0018] (1) Construct a three-dimensional vector holographic display device based on a dielectric metasurface as described in any one of claims 1 to 9;

[0019] (2) Decompose the target three-dimensional vector display image along an array composed of multiple spatial channels, and use the target axial response function of each spatial channel to determine the intensity distribution and polarization distribution of the target three-dimensional vector display image. To provide a quantitative mathematical description, where (p, q) is the corresponding spatial channel number, the scalar component of the response function describes the intensity distribution of the target, and the vector component describes the polarization distribution of the target;

[0020] (3) Decompose the target axial response function into mutually orthogonal left-handed and right-handed circular polarization channels to obtain two complex target response functions. and And the Bessel superposition coefficients are calculated using a Fourier-like relation as shown in equation (3):

[0021] (3)

[0022] (4) Calculate the vector light field distribution at the metasurface based on the obtained superposition coefficient. The corresponding normalized matrix is The normalized matrix Transform into the superposition of two unitary matrices To correspond to actual nanostructure units.

[0023] (5) Using electromagnetic simulation tools, the operating wavelength is set to optimize the dimensional parameters of the unit structure and find corresponding... and Nanostructured units.

[0024] (6) The nanostructure units of the two unit groups are arranged at intervals to form a checkerboard pattern, thus completing the construction of the metasurface. After the corresponding polarized incident light is incident on the metasurface, a three-dimensional vector holographic image of the target can be generated.

[0025] This application employs a metasurface-based 3D vector holographic display device that decomposes a target's 3D vector image into a structured beam array. These beams possess independently tunable axial intensity and polarization distribution. The longitudinal variation of each beam is quantitatively controlled by its corresponding response function, thereby enabling the construction of a high-capacity beam array with spatially variable vector characteristics. A compact, scalable, and integrable 3D vector holographic framework based on metasurfaces is established, showing broad application prospects in high-capacity optical communication, secure data storage, and quantum information systems.

[0026] This invention provides a three-dimensional vector holographic display method and device based on a dielectric metasurface. It selects a low-loss, high-refractive-index material as the nanostructure unit. Based on the interference effect of the nanostructure unit, by adjusting the arrangement period, geometry, size, and azimuth of the nanostructure units in the metasurface array, the polarization, phase, and amplitude of adjacent nanostructure units can meet specific distribution requirements. This enables multidimensional modulation of light waves, thereby achieving longitudinal control of the amplitude and polarization state of the incident light wave. Multiple independent spatial channels can then combine along the propagation direction in the outgoing three-dimensional space to generate tunable patterns with different polarization states, expanding information capacity and realizing the function of three-dimensional vector display. Therefore, compared with the prior art, this invention has the following beneficial effects:

[0027] 1. The three-dimensional vector display optical device designed in this invention has an ultra-thin thickness (subwavelength nanometer level), which is beneficial for combining the device with nanophotonic systems.

[0028] 2. Since the substrate is a low-loss, low-refractive-index dielectric material and the metasurface nanostructure unit is made of a low-loss, high-refractive-index dielectric material or a semiconductor material, the three-dimensional vector holographic display optical device based on a dielectric metasurface of the present invention has excellent control efficiency and image display effect.

[0029] 3. The three-dimensional vector display optical device of the present invention can achieve longitudinal control of the amplitude and polarization state of the incident light wave within a wide range. Multiple independent spatial channels can be combined in three-dimensional space to form adjustable patterns with different polarization states. Furthermore, there is no crosstalk between different spatial channels and different axial positions, which greatly increases the information capacity. This is of great significance for extending optical display from two-dimensional vector and two-dimensional scalar cascade to three-dimensional vector, and has potential application value in fields such as optical storage and encryption. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a three-dimensional vector holographic display method based on a structured beam array controlled along the z-axis in an embodiment of the present invention. The axial intensity and polarization distribution of the beam in each channel can be controlled independently.

[0031] Figure 2 This is a schematic diagram of the nanostructure unit and metasurface in an embodiment of the present invention, including an amorphous silicon dielectric pillar and a silicon dioxide substrate, H=400 nm, P=250 nm, D x and D y These are the major and minor axes of the rectangular structure. It is the rotation angle of the nanostructure unit.

[0032] Figure 3 In the embodiments of this invention, rectangular nanostructure units of different sizes are used at a wavelength of 633 nm and along the polarization direction. Phase delay diagram and transmittance distribution diagram under linearly polarized light incident along the axis.

[0033] Figure 4 This is a schematic diagram of the spacing between nanostructure units in two unit groups in an embodiment of the present invention. The shape parameters of the nanostructure units in each group are different.

[0034] Figure 5 These are optical microscope images of the metasurface three-dimensional vector display device prepared in the embodiments of the present invention.

[0035] Figure 6 These are magnified images of the metasurface three-dimensional vector display device prepared in the embodiments of the present invention under a scanning electron microscope and electron micrographs with a certain tilt angle.

[0036] Figure 7 The experimental results of the target effect and the prepared metasurface three-dimensional vector display device in the embodiment of the present invention under 633 nm linear polarization irradiation along the x-axis and the intensity distribution curve obtained by scanning along the z-axis are shown.

[0037] Figure 8The target effect of the embodiment of the present invention and the z-axis scanning full Stokes parameter measurement results of the prepared metasurface three-dimensional vector display device under linear polarization irradiation along the x-axis at 633 nm, and the evolution path on the corresponding Poincaré sphere. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0039] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0040] Example

[0041] A three-dimensional vector holographic display device based on a dielectric metasurface is proposed. The design incorporates highly symmetric all-dielectric metasurface nanostructure units. The cross-section of each nanostructure unit can be of arbitrary geometry, such as rectangle, square, ellipse, or circle, and can specifically be microstructures such as nanopillars, nanodisks, or nanopores. The substrate is a low-dielectric-constant, low-loss material, such as quartz glass, calcium fluoride, barium fluoride, aluminum oxide, and infrared chalcogenide glass. The nanostructure units are made of high-dielectric-constant, low-loss dielectric materials or semiconductor materials, such as gallium nitride, hafnium dioxide, titanium dioxide, silicon, silicon nitride, and germanium.

[0042] This embodiment uses silicon dioxide as a substrate and amorphous silicon nanopillars with rectangular cross-sections as structural units. The nanostructure units of the designed three-dimensional vector display device are arranged quasi-periodicly or periodically on the substrate, with each period consisting of a microstructure metasurface unit. Figure 2 As shown, the microstructure metasurface unit consists of two parts: an amorphous silicon dielectric pillar and a silicon dioxide substrate. P is the side length of the substrate for each periodic unit, and the height of the nanostructure unit is H, with a feature size of D. x and D y .

[0043] This embodiment uses a dual-matrix holographic method to jointly modulate polarization, phase, and amplitude. With a wavelength λ = 633 nm as the operating wavelength of the device, when linearly polarized incident light with its polarization direction along the x-axis irradiates the metasurface nanostructure unit, a database can be established using the finite element method to obtain a series of nanostructure units with different sizes, representing their phase delay and electric field intensity. In this embodiment, the period of the nanostructure unit is selected as a subwavelength scale, P = 250 nm, and the structural height H = 400 nm. By scanning the characteristic dimensions of the nanopillars, with length and width both ranging from 50 to 200 nm, the calculated phase delay and transmittance are shown below. Figure 3 When selecting nanostructure units, the first priority is to ensure that the phase delay of the structural parameter is as close as possible to the target value. Secondly, structural parameters with high transmittance should be selected to ensure high and uniform transmission efficiency in the device. Based on this, the characteristic dimensions of the selected nanostructure units are given in Table 1.

[0044] Table 1

[0045]

[0046] In this embodiment, the working distance is 3 mm, and the number of spatial channels is 5×5. Different spatial channels generate designed patterns "O", "P", and "J" in three axial regions: z = 0.12-0.68 mm, z = 1.22-1.78 mm, and z = 2.32-2.88 mm, respectively. Each channel uses a binary axial intensity function, allowing the on / off behavior of the encoded symbols to be defined along the beam propagation direction. The longitudinal polarization state of each beam is independently designed to evolve along a custom trajectory on a Poincaré sphere; in this example, a closed trajectory connecting the north (0, 0, 1) and south (0, 0, -1) poles of the Poincaré sphere is used. The distance between adjacent spatial channels is 50 μm. Each spatial channel is formed by the superposition of 81 zero-order Bessel beams with the same frequency and equally spaced longitudinal wave vectors, located in two orthogonal polarization channels (left-handed and right-handed circular polarization). The amplitude coefficient of the corresponding Bessel beam can be calculated using Matlab. Longitudinal wave vector Radial wave vector Furthermore, the complex amplitude modulation required to be achieved by the nanostructure unit can be calculated, and the specific calculation expression is as follows:

[0047] (1)

[0048] Where z represents the distance between the hypersurface and the direction of propagation, and z=0 represents the plane containing the hypersurface in free space. This represents the spatial position vector of any point on the cross-section along the propagation direction. The number of spatial channels is 25, and the corresponding coordinates are... The spatial channel location coordinates are Each spatial channel is formed by the superposition of 81 (N=40) zero-order Bessel beams with the same frequency and equally spaced longitudinal wave vectors, located in two orthogonal polarization channels, namely left-hand circular polarization and right-hand circular polarization.

[0049] This embodiment employs a dual-matrix holographic design method, such as... Figure 4 As shown, the nanostructure unit array is composed of two groups of nanostructure units arranged at intervals, forming a checkerboard-like pattern. The shape parameters of each group of nanostructure units are different, and the specific matrix response distributions achieved by the two groups of nanostructure units conform to equation (2):

[0050] (2)

[0051] in, and These are the left and right singular vector matrices obtained by performing singular value decomposition on the Jones matrix distribution at the normalized hypersurface, respectively. Complex values , , and From the singular value matrix diagonal elements ( and The result is obtained through transformation, i.e. and ,in Represents the position in the diagonal matrix ( ).

[0052] Based on the distribution of the obtained unitary matrix The structural parameters on the metasurface can be calculated through the following eigenvalue decomposition. With rotation angle Distribution:

[0053] (4)

[0054] The fabrication method for the metasurface sample is as follows: First, a 400 nm thick amorphous silicon (α-Si) layer was deposited on a 500 μm thick molten silicon substrate using plasma-enhanced chemical vapor deposition (PECVD). The α-Si surface was then cleaned with oxygen plasma to enhance adhesion, followed by spin-coating a 200 nm thick electron beam photoresist onto the α-Si film at 4000 rpm. The sample was then baked on a hot plate at 180 °C for 3 minutes. To mitigate the charging effect during electron beam lithography, an anti-charging conductive polymer was spin-coated onto the photoresist at 4000 rpm and baked at 90 °C for 90 seconds. Then, the designed pattern was defined in the photoresist using an electron beam lithography system at an accelerating voltage of 30 keV and developed in hexyl acetate. Next, a 30 nm thick Al layer was deposited on the photoresist using an electron beam evaporation device and immediately stripped in n-methylpyrrolidone at 80 °C. Finally, the pattern was transferred from the Al layer to the α-Si layer using chemical reactive ion etching (CRI). Finally, the residual aluminum mask was removed with an aluminum etchant to obtain the desired sample. Figure 5 An optical microscope image of the processed sample (1.2 mm × 1.2 mm) is shown. Figure 6 The scanning electron micrographs of the metasurface three-dimensional display device are presented, showing high precision and low surface roughness, and that adjacent nanostructure units have the same size but different rotation angles.

[0055] Next, the sample was tested. When linearly polarized light with polarization along the x-axis passed through the metasurface, the 5×5 spatial channel produced the designed patterns in three planes, as shown in the results. Figure 7 As shown. Further z-axis scanning was used to capture patterns on multiple planes, and the transverse intensity variation of a specific beam was measured. Linear and circular polarizers were added for polarization analysis, and z-axis scanning was performed again to obtain the axial intensity distribution under different polarization states. The normalized Stokes parameters S1, S2, and S3 were further calculated, allowing the measured and target polarization states to be mapped onto a Poincaré sphere, as shown in the figure. Figure 8 As shown, the experimental results and simulation results are very close, proving that the metasurface has excellent three-dimensional vector holographic display effects.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-dimensional vector holographic display device based on a dielectric metasurface, characterized in that: The three-dimensional vector holographic display device includes: a substrate and nanostructure units on the substrate; the nanostructure units are arranged on the substrate according to a specific phase distribution to form a nanostructure unit array; when light waves are incident on the three-dimensional vector holographic display device, after being modulated by the nanostructure units, the transmitted light waves are emitted in multiple independent spatial channels, which can be combined in the emitted three-dimensional space to generate adjustable patterns with different polarization states, thereby realizing three-dimensional vector display.

2. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The substrate is made of a low-loss, low-refractive-index dielectric material, and the nanostructure unit is made of a low-loss, high-refractive-index dielectric material or a semiconductor material.

3. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The substrate material is made of transparent glass, calcium fluoride, barium fluoride, aluminum oxide, or infrared chalcogenide glass, and the nanostructure unit is made of titanium dioxide, hafnium dioxide, gallium nitride, silicon nitride, silicon, or germanium.

4. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The vector light field distribution of the nanostructure unit array for three-dimensional vector display conforms to equation (1): (1) in, This represents the distance between the propagation direction and the metasurface. This represents the plane containing the hypersurface in free space. This represents the spatial position vector of any point on the cross-section along the propagation direction, with corresponding coordinates as follows: The spatial channel location coordinates are Each spatial channel consists of left-handed and right-handed circular deflection channels. It is formed by the superposition of Bessel beams with the same frequency and equally spaced longitudinal wave vectors. It is a zero-order Bessel function. and The first and second circular deflection channels are respectively left-handed and right-handed. Complex amplitude coefficients of a Bessel beam To correspond to the longitudinal wave vector of the Bessel beam, To correspond to the radial wave vector of the Bessel beam, satisfying ,in For free space wave vectors.

5. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The nanostructure unit array is composed of two groups of nanostructure units arranged at intervals to form a checkerboard pattern; the specific matrix response distribution realized by each group of nanostructure units is ( and Conformation (2): (2) in, and These are the left and right singular vector matrices obtained by performing singular value decomposition on the Jones matrix distribution at the normalized hypersurface, respectively. Complex values , , and From the singular value matrix diagonal elements ( and The result is obtained through transformation, i.e. and ,in Represents the position in the diagonal matrix ( ).

6. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The ratio of the dielectric constant of the substrate to that of the nanostructure unit is 1:(1.2 to 3.7).

7. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The nanostructure units are arranged in a quasi-periodic or periodic manner on the substrate. The side length of each periodic unit is P, where P is 0.5λ to λ. All nanostructure units have the same height H, where H is 0.4λ to λ, and λ is the wavelength of the incident light wave.

8. The three-dimensional vector holographic display device based on a dielectric metasurface according to claim 1, characterized in that: The cross-sectional shape of the nanostructure unit is rectangular, square, elliptical, or circular; when the cross-sectional shape of the nanostructure unit is rectangular, square, or elliptical, the size of its major and minor axes ranges from 0.2P to 0.8P; the angle between the major axis of the nanostructure unit and the x-axis is 0 to 180°; when the cross-sectional shape of the nanostructure unit is circular, the size of its radius ranges from 0.1P to 0.4P, where P is the period of the nanostructure unit.

9. A display method for a three-dimensional vector holographic display device based on a dielectric metasurface, characterized in that... Includes the following steps: (1) Construct a three-dimensional vector holographic display device based on a dielectric metasurface as described in any one of claims 1 to 9; (2) Decompose the target three-dimensional vector display image along an array composed of multiple spatial channels, and use the target axial response function of each spatial channel to determine the intensity distribution and polarization distribution of the target three-dimensional vector display image. To provide a quantitative mathematical description, where (p, q) is the corresponding spatial channel number, the scalar component of the response function describes the intensity distribution of the target, and the vector component describes the polarization distribution of the target; (3) Decompose the target axial response function into mutually orthogonal left-handed and right-handed circular polarization channels to obtain two complex target response functions. and And the Bessel superposition coefficients are calculated using a Fourier-like relation as shown in equation (3): （3） (4) Calculate the vector light field distribution at the metasurface based on the obtained superposition coefficient. The corresponding normalized matrix is The normalized matrix Transform into the superposition of two unitary matrices To correspond to actual nanostructure units; (5) Using electromagnetic simulation tools, the operating wavelength is set to optimize the dimensional parameters of the unit structure and find corresponding... and Nanostructured units; (6) The nanostructure units of the two unit groups are arranged at intervals to form a checkerboard pattern, and the metasurface is finally constructed. After the corresponding polarized incident light is incident on the metasurface, a three-dimensional vector holographic image of the target can be generated.

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