Three-dimensional reconfigurable vector holographic double-layer cascade super device, design method and equipment

Abstract

Three-dimensional reconfigurable vector holographic double-layer cascade super device, design method and equipment belong to the field of holographic technology, solve the problem that reconfiguration of incident wave front often involves changing light source or polarizer operation, which is not only inconvenient but also cannot realize fast switching. The device includes: a hybrid cascade of radiative super surface and birefringent super surface, the intensity and polarization response of hologram in three-dimensional space is reconfigurable and highly customized. The rotatable radiative super surface can be used as an incident wave front modulator to excite the non-rotatable birefringent super surface. By introducing a gradient descent optimization inverse design method, numerical analysis and experimental verification of three-dimensional reconfigurable vector holography are demonstrated in the microwave region. The present application is suitable for integrated encryption devices and holographic display super devices.

Description

Technical Field

[0001] This application relates to the field of holographic technology, and in particular to three-dimensional reconfigurable vector holographic meta-devices. Background Technology

[0002] Holography, a remarkable technique for reconstructing the three-dimensional light field of objects, has permeated various sectors of society in recent years, finding widespread application in modern scientific research and industrial production. Recently, metasurface-based holography has revolutionized traditional holography. Composed of subwavelength-spaced metacell arrays, it allows for point-by-point manipulation of electromagnetic wave properties. Vectorial metasurface holography (VMH), in particular, can not only control the complex amplitude distribution of holographic images but also arbitrarily customize their polarization distribution.

[0003] On the other hand, reconfigurability is crucial for applications such as optical encryption and dynamic holographic displays. However, in the methods described above, achieving overall device reconfigurability is not easy once the metasurface and excitation are determined. In general, the VMH field distribution on the observation plane can be expressed as...

[0004]

[0005] Among them, U input (x,y) corresponds to the input wavefront of the excitation, U meta (x,y) represents the function of the metasurface, and h(x,y,z) represents the impulse response. According to formula (1), the VMH field distribution U VMH (x,y,z) is mainly composed of U input (x,y) and U meta (x,y) determines the reconfigurable functionality, so these two terms can be adjusted to achieve the desired functionality.

[0006] For U meta The adjustment of (x,y) primarily focuses on the reconfigurable properties of metasurface units. Many dynamic materials, such as active devices, liquid crystals, thermally shrinkable shape memory polymers, phase change materials, and microfluidics, have been used to construct metasurface units. However, these methods typically involve the introduction of additional control devices. Furthermore, since VMHs are usually achieved through the superposition of at least one pair of electromagnetic waves with different complex amplitudes and polarization states, it is difficult to modulate the VMH in reconfigurable metasurface units. Therefore, for U... meta The adjustment of (x,y) is mainly focused on scalar holographic devices.

[0007] U inputThe (x,y) coordinates provide significant freedom for adjusting the phase and polarization state of the incident wavefront. Under different polarization conditions, by introducing noise, 11 independent VMHs can be realized in three-dimensional space using a single metasurface. Orbital angular momentum (OAM) holography, through modulation of the helical incident wavefront, has also been applied to 10-bit OAM-coded holograms for high-security optical encryption. Furthermore, angular momentum holography can fully coordinate the OAM and spin angular momentum (SAM) dimensions to achieve switching between spin-orbit locked holograms and spin superposition holograms. Moreover, by optimizing the phase distribution of spatial light modulators (SLMs) and the metasurface using a genetic algorithm, switching between holographic images of the entire periodic table can be achieved. However, existing reconfigurable incident wavefronts often involve changing the light source or polarizer, which is neither convenient nor allows for rapid switching. Therefore, exploring a convenient and effective reconfigurable VMH mechanism remains a challenge. Summary of the Invention

[0008] The purpose of this invention is to solve the problem that existing incident wavefront reconfigurable devices often involve operations such as changing the light source or polarizer, which is inconvenient and cannot achieve rapid switching. The invention provides a three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device, design method and equipment.

[0009] The present invention is achieved through the following technical solution. In one aspect, the present invention provides a three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure device, the device comprising a radial metasurface RTM and a birefringent metasurface BM, wherein the RTM is rotatable and the BM is non-rotatable.

[0010] RTM and BM are aligned and cascaded.

[0011] Furthermore, RTM and BM have the same dimensions.

[0012] Furthermore, the spacing between the RTM and BM is selected to be greater than twice the operating wavelength.

[0013] Furthermore, the overall structure of the RTM consists of metal, dielectric, metal, dielectric, and metal from top to bottom, with the three metal layers being the radiation layer, ground layer, and feed layer, respectively.

[0014] Furthermore, the radiation layer consists of two C-shaped open resonant rings that directly generate circularly polarized wave radiation; the feed layer is arranged at the bottom layer and is connected to the radiation layer through metal vias.

[0015] Furthermore, the overall structure of BM, from top to bottom, consists of metal, dielectric, metal, dielectric, and metal.

[0016] Secondly, the present invention provides a design method for a three-dimensional reconfigurable vector holographic two-layer cascaded metastructure device as described above, the method comprising:

[0017] The spatial evolution process is established based on the vector metasurface holographic VMH field distribution on the observation plane, and vector holographic image reconstruction is performed.

[0018] Each neuron in the input layer is represented as a Jones vector J. 2×1 Furthermore, a reconfigurable operator R(·) is defined to describe the mathematical characteristics of reconfigurable VMH. Its reconfigurability is achieved by performing a matrix transformation on the input matrix represented by the RTM radiation field. The input matrix is:

[0019]

[0020] in, Let U be the Jones vector, N be the number of elements along the x and y directions, and R(·) represent a matrix transformation; input Connect to the next layer through diffraction theory;

[0021] The hidden layer is a 2×2 Jones matrix J 2×2 :

[0022]

[0023] in, and It is the phase difference along the x-axis and y-axis, rotated by an angle θ relative to the reference coordinate system;

[0024] The hidden layer matrix is:

[0025]

[0026] Each neuron in the output layer represents the Jones vector of the VMH in the desired plane, and the output matrix U VMH The expression is:

[0027]

[0028] By using a reverse design method, the matrix elements of the Jones matrix or Jones vector corresponding to each layer of neurons are iteratively trained to execute the VMH function.

[0029] Thirdly, the present invention provides a computer device including a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, it performs the steps of the method described above.

[0030] Fourthly, the present invention provides a computer-readable storage medium storing a plurality of computer instructions for causing a computer to perform the method described above.

[0031] Fifthly, the present invention provides an electronic device, comprising:

[0032] At least one processor; and,

[0033] A memory communicatively connected to the at least one processor; wherein,

[0034] The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method described above.

[0035] The beneficial effects of this invention are:

[0036] This invention proposes a rotationally driven 3D reconfigurable vector holographic dual-layer cascaded meta-device that enables highly customized VMH (Vibrational Virtualization) and rotationally driven dynamic VMH switching in 3D space. The device integrates a rotating RTM (Resonant Polarization Module) and a non-rotating BM (Meta-Polarization Module). The RTM serves not only as a circularly polarized excitation but also as a compact incident wavefront modulator driven by rotation, while the BM acts as a meta-polarization device to reconstruct the VMH image. A gradient descent optimization inverse design method is introduced to establish the Jones vector relationship between the input and output images, thereby achieving high-purity vector holographic image reconstruction.

[0037] This invention is applicable to integrated encryption devices and holographic display meta-devices. Attached Figure Description

[0038] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 Schematic diagram of a rotation-driven 3D reconfigurable vector holographic dual-layer cascaded metastructure device;

[0040] Figure 2 For reverse engineering method architecture;

[0041] Figure 3 Meta-unit design: (a) Geometry of the CSRR; (b) 3D schematic diagram of the CSRR; (c) Simulated radiation amplitude and phase of the CSRR at 10 GHz; (d) Geometry of the birefringent meta-unit; (e) 3D schematic diagram of the birefringent unit; Simulation results of the birefringent unit at 10 GHz. (h)Axx (i)A yy ;

[0042] Figure 4 Simulation demonstration of a rotation-driven three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure at 10GHz;

[0043] Figure 5 The test results are for a rotation-driven three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure at 10 GHz. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0045] Implementation Method 1: A three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure device, the device comprising a radial metasurface RTM and a birefringent metasurface BM, wherein the RTM is rotatable and the BM is non-rotatable;

[0046] RTM and BM are aligned and cascaded.

[0047] In this embodiment, a rotationally driven three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure is proposed, in which a radial metasurface and a birefringent metasurface are hybridly cascaded. Therefore, the intensity and polarization response of the hologram in three-dimensional space are reconfigurable and highly customizable. The rotatable radiation-type metasurface (RTM) can be used as an incident wavefront modulator to excite the non-rotatable birefringent metasurface (BM).

[0048] Highly customized VMH and rotationally driven dynamic VMH switching can be achieved in three-dimensional space. The device integrates a rotating RTM and a non-rotating BM. The RTM serves not only as a circularly polarized excitation but also as a compact incident wavefront modulator driven by rotation, while the BM is used as a metapolarization device to reconstruct the VMH image. High-purity vector holographic image reconstruction can be achieved by introducing a gradient descent optimization inverse design method to establish the Jones vector relationship between the input and output images.

[0049] Implementation Method Two: This implementation method further defines the three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device described in Implementation Method One. In this implementation method, RTM and BM are further defined, specifically including:

[0050] RTM and BM have the same dimensions.

[0051] In this embodiment, the reason for using the same size is to ensure that the RTM irradiates the BM uniformly and to facilitate cascading.

[0052] Implementation method three is a further definition of the three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device described in implementation method one. In this implementation method, the spacing between the RTM and BM is further defined, specifically including:

[0053] The spacing between the RTM and BM should be greater than twice the operating wavelength.

[0054] In this embodiment, the reason for selecting a wavelength greater than twice the operating wavelength is to ensure that the electromagnetic wave propagation between the RTM and BM satisfies the scalar diffraction theory.

[0055] Implementation Method Four: This implementation method further defines the three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure device described in Implementation Method One. In this implementation method, the overall structure of the RTM is further defined, specifically including:

[0056] The overall structure of the RTM consists of metal, dielectric, metal, dielectric, and metal from top to bottom. The three metal layers are the radiation layer, the ground layer, and the feed layer, respectively.

[0057] In this embodiment, the RTM integrates the feeding structure and the radiation structure, which not only avoids additional spatial feed sources and improves the overall system compactness, but also enables phase modulation of the radiated wave.

[0058] Implementation method five is a further definition of the three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device described in implementation method four. In this implementation method, the radiating layer and the feeding layer are further defined, specifically including:

[0059] The radiation layer consists of two C-shaped open resonant rings that directly generate circularly polarized wave radiation; the feed layer (feed microstrip line) is arranged on the bottom layer and connected to the radiation layer through metal vias.

[0060] In this embodiment, the specific structures of the radiation layer and the feed layer are given. The advantage of using two C-shaped split-ring resonators (CSRR) is to improve the circular polarization purity of the radiation wave, thereby enhancing the system's compactness and enabling phase modulation of the radiation wave.

[0061] Implementation method six is ​​a further definition of the three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device described in implementation method one. In this implementation method, the overall structure of BM is further defined, specifically including:

[0062] The overall structure of BM, from top to bottom, consists of metal, dielectric, metal, dielectric, and metal.

[0063] In this embodiment, the BM may include three metal layers and two Rogers RT5880 dielectric substrates with a thickness of 2 mm. Each metal layer may include a circular groove and an elliptical patch. By adjusting the parameters of the elliptical patch, the amplitude and phase of the orthogonal polarization components of the transmitted wave can be independently controlled.

[0064] BM is an array of birefringent metaunits, which are physical structures that satisfy the birefringence phenomenon.

[0065] Implementation method seven, this implementation method is Example 1 of a three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device as described above, specifically including:

[0066] A schematic diagram of a rotation-driven 3D reconfigurable vector holographic dual-layer cascaded hyperstructure device is shown below. Figure 1 As shown, the RTM and BM constitute a bilayer hybrid metasurface device. The RTM and BM have the same size and are aligned and cascaded in space. The spacing between the RTM and BM is typically chosen to be greater than twice the operating wavelength (e.g., at 10 GHz, the distance is typically greater than 60 mm). When both the RTM and BM are fixed, the VMH changes in three-dimensional space, resulting in different polarization states of VMH on each propagation plane (e.g., the character "1" has a 0° linear polarization, the character "9" has a 90° linear polarization, the character "2" has a 45° linear polarization, and the character "0" has a 135° linear polarization). The VMH switching between two states in three-dimensional space is achieved through in-plane rotation of RTM (for example, the character "1" with 0° linear polarization and the character "9" with 90° linear polarization switch to the character "H" with 120° linear polarization at z1, the character "2" with 45° linear polarization switch to the character "I" with 60° linear polarization at z2, and the character "0" with 135° linear polarization switch to the character "T" with 0° linear polarization at z3).

[0067] for Figure 1 The rotation-driven three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure shown employs a reverse design method, establishing a spatial evolution process according to formula (1) to achieve high-purity vector holographic image reconstruction, such as... Figure 2 As shown. Since RTM directly radiates electromagnetic waves, each neuron in the input layer can be represented as a Jones vector J. 2×1 A reconfigurable operator R(·) is defined to describe the mathematical characteristics of reconfigurable VMHs. Its reconfigurability can be achieved by performing a matrix transformation on the input matrix represented by the RTM radiation field. Therefore, the input matrix can be represented as...

[0068]

[0069] Where N is the number of units along the x and y directions, and R(·) represents a matrix transformation. input Connect to the next layer through diffraction theory.

[0070] The hidden layer is a 2×2 Jones matrix J 2×2 :

[0071]

[0072] in, and It is the phase difference along the x-axis and y-axis, rotated by an angle θ relative to the reference coordinate system.

[0073] The hidden layer matrix can be represented as:

[0074]

[0075] Each neuron in the output layer represents the Jones vector of the VMH in the desired plane, and the output matrix U VMH with U input The form is the same, as shown in formula (2). By using the reverse design method, the matrix elements of the Jones matrix or Jones vector corresponding to each layer of neurons are iteratively trained to perform specific VMH functions.

[0076] The parameters optimized by this method mainly consist of two parts: the parameters in the input Jones vector. And the parameters of the Jones matrix in the hidden layer. Their value ranges are respectively And θ∈[0,π].

[0077] The reverse design process for rotation-driven 3D reconfigurable vector holographic two-layer cascaded metastructures is as follows: First, the parameters of the input layer and hidden layer are randomly generated.

[0078] Subsequently, the electric field distribution of the output layer was calculated using Rayleigh-Sommerfeld diffraction theory.

[0079] Then, the calculated electric field distribution is compared with the pre-set target field distribution, and the mean squared error (MSE) between the two is calculated as the loss function. Here, gradient descent and backpropagation algorithms are used to implement the pre-set target field distribution.

[0080] Implementation method seven, this implementation method is embodiment 2 of the three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device as described above, specifically including:

[0081] This embodiment employs two types of metaunits to construct a rotationally driven, three-dimensional reconfigurable vector holographic dual-layer cascaded metastructure, such as... Figure 3 As shown, where, These four symbols represent four parameters of the transmission field of the birefringent unit, which can be expressed as:

[0082]

[0083] like Figure 3 As shown in Figure b, the overall structure of the RTM, from top to bottom, is metal-dielectric-metal-dielectric-metal, with three metal layers: a radiating layer, a ground layer, and a feed layer. The radiating layer consists of two C-shaped split-ring resonators (CSRRs), which can directly generate circularly polarized wave radiation. The feed microstrip line is arranged on the bottom layer and connected to the radiating layer through metal vias. The copper thickness is 0.035 mm, and the thicknesses of the F4BM-2 dielectric substrate are h1 = 3 mm and h2 = 1.27 mm, respectively. φ is defined as the rotation angle of the CSRR structure around its geometric center. When the CSRR rotates with φ, the path of the surface current also rotates, thus introducing an additional phase that is only related to the geometric path. Therefore, 2π phase modulation of the radiated wave can be achieved. The RTM integrates the feed structure and the radiating structure, which avoids additional spatial feed sources, improves the compactness of the overall system, and enables phase modulation of the radiated wave.

[0084] Figure 3 c presents the simulated radiation amplitude and phase of CSRR at 10 GHz, with the rotation angle φ ranging from 0 to 360°. As the rotation angle φ changes, the radiation amplitude remains around 0.9, while the radiation phase achieves 2π phase coverage.

[0085] Meanwhile, the overall structure of the birefringent metaunit, from top to bottom, is metal-dielectric-metal-dielectric-metal, comprising three metal layers and two 2mm thick Rogers RT5880 dielectric substrates. Each metal layer includes a circular groove and an elliptical patch. By adjusting the parameters of the elliptical patch, the amplitude and phase of the orthogonal polarization components of the transmitted wave can be independently controlled.

[0086] Below is a demonstration of the rotation-driven three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device of this application:

[0087] The RTM consists of a 32×32 CSRR array (radiating layer) and a power divider feed network (feeding layer). The aperture size is 320mm×320mm, the overall thickness is 4.375mm, and the spacing between the RTM and BM is 150mm.

[0088] Eight characters, "1", "9", "2", "0", "2", "0", "2", "3", "H", "I", and "T", with polarization states of 0°, 90°, 45°, 135°, RCP, LCP, 0°, 90°, 0°, 60°, and 120°, are set at three positions (z1 = 100mm, z2 = 160mm, and z3 = 230mm). These three states correspond to the vector hologram switching from "1", "9", "2", "0" to "2", "0", "2", "3" and then to "H", "I", "T". The simulation results are as follows: Figure 4 As shown. Next, the simulation model was physically fabricated and tested, and the test results are as follows. Figure 5 As shown in the figure, the simulation results and test results are in good agreement with the preset images, demonstrating the excellent performance of the rotation-driven three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure proposed in this application.

[0089] Metasurface-based vector holography is an advanced platform for high-capacity information storage, holographic display, and cryptography. However, a convenient and efficient mechanism for generating reconfigurable vector holograms remains a challenge. This application proposes a rotation-driven, three-dimensional reconfigurable vector holographic dual-layer cascaded metasurface, in which a radial metasurface and a birefringent metasurface are hybrid cascaded. Therefore, the intensity and polarization response of the hologram in three-dimensional space are reconfigurable and highly customizable. The rotatable radiation-type metasurface (RTM) can be used as an incident wavefront modulator to excite the non-rotatable birefringent metasurface (BM). Numerical analysis and experimental verification of three-dimensional reconfigurable vector holography are demonstrated in the microwave region by introducing a gradient descent optimization inverse design method.

Claims

1. A three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device, characterized in that, The device includes a radial metasurface RTM and a birefringent metasurface BM. The RTM is rotatable, while the BM is not rotatable. RTM and BM are aligned and cascaded in parallel; The spatial evolution process is established based on the vector metasurface holographic VMH field distribution on the observation plane, and vector holographic image reconstruction is performed. Each neuron in the input layer is represented as a Jones vector J. 2×1 Furthermore, a reconfigurable operator R(·) is defined to describe the mathematical characteristics of reconfigurable VMH. Its reconfigurability is achieved by performing a matrix transformation on the input matrix represented by the RTM radiation field. The input matrix is: in, For Jones vector, N It is along x and y The number of elements in the direction, R(·) represents a certain matrix transformation; U input Connect to the next layer through diffraction theory; The hidden layer is a 2×2 Jones matrix J 2×2 : in, φ x and φ y It is along x shaft and y The phase difference of the axes is due to a rotation of an angle relative to the reference coordinate system. θ ; The hidden layer matrix is: ； Each neuron in the output layer represents the Jones vector of the VMH in the desired plane, and the output matrix U VMH The expression is: By using a reverse design method, the matrix elements of the Jones matrix or Jones vector corresponding to each layer of neurons are iteratively trained to execute the VMH function.

2. The three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device according to claim 1, characterized in that, RTM and BM have the same dimensions.

3. The three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device according to claim 1, characterized in that, The spacing between the RTM and BM should be greater than twice the operating wavelength.

4. The three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device according to claim 1, characterized in that, The overall structure of the RTM consists of metal, dielectric, metal, dielectric, and metal from top to bottom. The three metal layers are the radiation layer, the ground layer, and the feed layer, respectively.

5. A three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device according to claim 4, characterized in that, The radiation layer consists of two C-shaped open resonant rings that directly generate circularly polarized wave radiation; the feed layer is arranged at the bottom layer and is connected to the radiation layer through metal vias.

6. The three-dimensional reconfigurable vector holographic dual-layer cascaded hyperstructure device according to claim 1, characterized in that, The overall structure of BM, from top to bottom, consists of metal, dielectric, metal, dielectric, and metal.

Images