Si / VO2 double-nanorod metasurface dynamic holographic display and optical encryption device and method

Abstract

The invention discloses a Si / VO2 double nanorod metasurface dynamic holographic display and optical encryption device and method, and relates to the technical field of metasurface holography, the device comprises a SiO2 substrate and composite metasurface units arranged on the surface of the SiO2 substrate; and the composite metasurface unit is composed of a Si nanorod and a VO2 nanorod. A'static camouflage + dynamic reality 'dual information hiding strategy and a three-level verification mechanism are innovatively designed, and compared with an existing static encryption technology of a single key (polarization / wavelength), the illegal cracking difficulty is improved by three orders of magnitude; a phase compensation scheme is adopted to encode an encrypted image, dynamic phase compensation is introduced through VO2 phase change, composite phase distribution is formed by the dynamic phase compensation and a Si nanorod static phase, and real-time reconfigurable phase modulation which cannot be achieved by a traditional single-material metasurface is achieved. According to a synergistic effect unit structure of the Si / VO2 double nanorods, by accurately controlling geometric parameters and spatial arrangement of the two nanorods, multifunctional integration which cannot be achieved by a traditional single-material metasurface is achieved.

Description

Technical Field

[0001] This invention relates to the field of metasurface holography technology, specifically to a Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device and method. Background Technology

[0002] Metasurfaces are a class of two-dimensional artificial materials designed based on subwavelength scales. By precisely controlling the geometric parameters, arrangement, and material properties of the unit structure, the propagation direction, polarization state, phase, and other characteristics of electromagnetic waves can be precisely manipulated.

[0003] To achieve dynamic control of metasurfaces, researchers have successively introduced materials such as liquid crystals, microelectromechanical systems (MEMS), and vanadium oxide (VO2). Among them, liquid crystal metasurfaces change the optical response by adjusting the arrangement of liquid crystal molecules through an electric field, but the response speed is only at the millisecond level, which is difficult to meet the requirements of high-frequency real-time control. MEMS metasurfaces adjust the unit structure through mechanical displacement, which has a high degree of freedom of control, but requires complex external control equipment, and the device size and weight are large, which is not conducive to miniaturization and integration. VO2 metasurfaces rely on the metal-insulator transition characteristics of the material at a specific temperature, and the response speed is better than that of liquid crystals and MEMS metasurfaces. However, existing VO2 metasurfaces and other tunable metasurfaces generally suffer from low degree of freedom of control and difficulty in meeting the requirements of multi-state control. They are mostly used for beam deflection or focusing and are not well integrated with optical encryption technology, which cannot achieve high-security dynamic information hiding.

[0004] Optical encryption technology is crucial in fields such as anti-counterfeiting, information security, and military communications. Traditional optical encryption methods (such as holographic encryption and polarization encryption) rely on complex optical systems, which are difficult to miniaturize and dynamically control. Although static metasurface encryption technology has a compact structure, it cannot be dynamically updated after the encrypted information is written, resulting in limited security. Existing dynamic encryption metasurfaces are limited by slow response speed, complex control, or insufficient key dimensions, and cannot simultaneously meet the requirements of high security and real-time reconfigurability.

[0005] Based on this, we now provide a Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device and method, which can eliminate the drawbacks of existing devices. Summary of the Invention

[0006] The purpose of this invention is to provide a Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device and method to solve the problems in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device includes a SiO2 substrate and a composite metasurface unit arranged on the surface of the SiO2 substrate; the composite metasurface unit is composed of Si nanorods and VO2 nanorods.

[0008] Based on the above technical solutions, the present invention also provides the following optional technical solutions: In one alternative: both the Si nanorods and the VO2 nanorods are anisotropic structures.

[0009] In one alternative approach, the phase transition triggering method of the VO2 nanorods includes electrical excitation, thermal excitation, and optical excitation.

[0010] In one alternative, the phase transition response speed of the VO2 nanorods is on the order of nanoseconds.

[0011] An optical encryption method for the aforementioned device is characterized by comprising the following steps: S1: System initialization, pre-calculating and storing a static phase map and a real phase map using the ASM algorithm; S2: Receive encryption command and detect ambient temperature; if temperature < 68℃, enter static encryption mode; if temperature ≥ 68℃, enter dynamic encryption mode. S3: In dynamic encryption mode, start the polarization detection module. If a specific polarized incident light is detected, call the pre-stored real phase map. S4: VO2 nanorods provide dynamic phase φ 2 The static phase φ of the Si nanorod 1 Superposition operations are performed to generate encrypted phase φ, which in turn generates an encrypted hologram.

[0012] In one alternative scheme, the encryption process employs a three-level verification mechanism: the first level is physical state verification, verifying whether the ambient temperature has reached the critical temperature of 68°C for the VO2 phase transition; the second level is optical key verification, verifying whether the incident light is in a specific polarization state; and the third level is phase superposition verification, verifying the static phase φ. 1 With dynamic phase φ 2 The system checks whether the stacking logic is correct; if any level of verification fails, the system returns to static encryption mode.

[0013] In one alternative: in step S4, the phase φ 1 φ 2 Each is discrete into a 2-bit coded state, corresponding to phase values ​​of 0°, 90°, 180°, and 270° respectively.

[0014] In one alternative: In step S2, under static encryption mode, the Si nanorod array generates false patterns A and B for x-polarized light and y-polarized light, respectively.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The core innovation of this invention lies in the synergistic unit structure of Si / VO2 dual nanorods. By precisely controlling the geometric parameters and spatial arrangement of the two nanorods, multifunctional integration that cannot be achieved by traditional single-material metasurfaces is realized.

[0016] This invention innovatively designs a dual information hiding strategy of "static camouflage + dynamic authenticity" and a three-level verification mechanism. Compared with the existing static encryption technology with a single key (polarization / wavelength), the difficulty of illegal cracking is increased by three orders of magnitude, and it has hardware-level anti-counterfeiting features.

[0017] This invention employs a phase compensation scheme to encode encrypted images, introducing dynamic phase through the VO2 phase transition to compensate for (φ) 2 ), and the static phase of the Si nanorod (φ 1 ) forms a composite phase distribution (φ_encryption=φ 1 +φ 2 This enables real-time reconfigurable phase modulation, which is unattainable by traditional single-material metasurfaces. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the coded metasurface unit of the present invention.

[0019] Figure 2 This is a metasurface encryption phase compensation diagram of the present invention.

[0020] Figure 3 This is a flowchart of the metasurface encryption process of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] In one embodiment, such as Figures 1-3 As shown, the Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device includes a SiO2 substrate and composite metasurface units arranged on the surface of the SiO2 substrate; the composite metasurface units are composed of Si nanorods and VO2 nanorods. The Si nanorods have dimensions of length L1, width W1, and height H, and are used to provide the static phase φ. 1 The VO2 nanorods have dimensions of length L2, width W2, and height H, and are used to provide dynamic phase φ under temperature triggering. 2When the temperature is below 68℃, VO2 is in an insulating state (conductivity 200 S / m), and only Si nanorods function. When the temperature is ≥68℃, VO2 transforms into a metallic state (conductivity 2 × 10⁵ S / m), and Si nanorods and VO2 nanorods work synergistically to form a composite encryption phase φencryption = φencryption. 1 +φ 2 .

[0023] In one embodiment, both the Si nanorods and the VO2 nanorods are anisotropic structures.

[0024] By adjusting the difference in arm length in the orthogonal directions, the phase of x-polarized and y-polarized electromagnetic waves can be independently controlled, and a phase difference of π / 2 is generated in the x and y polarization directions.

[0025] In one embodiment, the phase transition triggering method for VO2 nanorods includes electrical excitation, thermal excitation, and optical excitation (femtosecond pulse).

[0026] The specific working principle and method are as follows: (I) Metasurface Unit Structure Design: The metasurface uses SiO2 as a substrate, with composite metasurface units periodically arranged on the substrate surface. Each unit contains one Si nanorod and one VO2 nanorod. The specific parameters are designed as follows: Si nanorods: Employing an anisotropic structure with dimensions L1 (length), W1 (width), and H (height), they allow for independent phase control of x-polarized and y-polarized electromagnetic waves by adjusting the differences in arm lengths along their orthogonal directions. This generates a phase difference of π / 2 in the x and y polarization directions, providing a static phase φ. 1 ; VO2 nanorods: Measuring length L2, width W2, and height H, they are identical in height to Si nanorods, ensuring precise phase compensation for Si nanorods in the metallic state, and are used to provide dynamic phase φ. 2 ; Phase discretization: φ 1 φ 2 Each wavefront is discrete into a 2-bit encoded state, corresponding to four phase values: 0°, 90°, 180°, and 270°. Complex wavefront reconstruction is achieved through the spatial arrangement of nanorods.

[0027] (II) VO2 phase transition regulation mechanism: VO2 material has a phase transition critical temperature of 68℃. The physical properties and optical functions at different temperatures are as follows: Insulating state (temperature < 68℃): VO2 has a monoclinic crystal structure with an electrical conductivity of only 200 S / m and weak optical response. At this time, the metasurface only relies on Si nanorods to work and generate static camouflage information. Metallic state (temperature ≥ 68℃): VO2 transforms into a tetragonal crystal structure, with its electrical conductivity increasing sharply to 2 × 10⁵ S / m. This results in a synergistic effect with Si nanorods, through dynamic phase φ... 2 Compensation static phase φ 1 This forms a composite encryption phase φ encryption = φ 1 +φ 2 ; Phase transition triggering: VO2 phase transition can be triggered by electrical excitation, thermal excitation (such as heating by finger touch) or optical excitation (femtosecond pulse), with a response speed reaching the nanosecond level, far exceeding that of traditional liquid crystal materials.

[0028] (III) Dynamic Encryption Workflow: Combined with appendix Figure 3 The dynamic encryption workflow of this invention is as follows: System initialization: The static phase map of Si nanorods and the phase map required for actual encryption are pre-calculated using the angle spectral method (ASM algorithm) and stored in the encryption controller; Encryption command input: Upon receiving an external encryption command, the system activates the ambient temperature detection module to determine whether the current temperature has reached the critical temperature for the VO2 phase transition; Static encryption mode (temperature < 68℃): If the temperature does not reach the critical value, only the Si nanorod array on the metasurface works. According to the preset pseudo-information encoding rules, a false pattern A is generated for x-polarized incident light and a false pattern B is generated for y-polarized incident light to achieve information camouflage. Dynamic encryption mode (temperature ≥ 68℃): If the temperature reaches the critical value, the system automatically switches to dynamic encryption mode and simultaneously activates the polarization detection module; if incident light with a specific polarization state is detected, the encryption controller calls the pre-stored real phase map, and the VO2 nanorod provides the dynamic phase φ in real time. 2 The static phase φ of the Si nanorod 1 Superposition operations are performed to generate an encrypted phase φ, and finally the encrypted hologram is reconstructed. Verification Mechanism: The decryption process must strictly follow the three-level verification sequence of "temperature triggering → polarization selection → phase superposition". If any step fails (such as insufficient temperature, polarization error, or abnormal phase superposition logic), the system will immediately return to static encryption mode to ensure information security.

[0029] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device, characterized in that, It includes a SiO2 substrate and composite metasurface units arranged on the surface of the SiO2 substrate; the composite metasurface units are composed of Si nanorods and VO2 nanorods.

2. The Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device according to claim 1, characterized in that, Both the Si nanorods and VO2 nanorods are anisotropic structures.

3. The Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device according to claim 2, characterized in that, The phase transition triggering methods for the VO2 nanorods include electrical excitation, thermal excitation, and optical excitation.

4. The Si / VO2 dual nanorod metasurface dynamic holographic display and optical encryption device according to claim 3, characterized in that, The phase transition response speed of the VO2 nanorods is on the order of nanoseconds.

5. An optical encryption method based on the device according to any one of claims 1-4, characterized in that, Includes the following steps: S1: System initialization, pre-calculating and storing the static phase map and the actual phase map using the ASM algorithm; S2: Receives encrypted commands and detects ambient temperature; If the temperature is <68℃, enter static encryption mode; if the temperature is ≥68℃, enter dynamic encryption mode. S3: In dynamic encryption mode, start the polarization detection module. If a specific polarized incident light is detected, call the pre-stored real phase map. S4: VO2 nanorods provide dynamic phase φ 2 The static phase φ of the Si nanorod 1 Superposition operations are performed to generate encrypted phase φ, which in turn generates an encrypted hologram.

6. The method according to claim 5, characterized in that, The encryption process employs a three-level verification mechanism: the first level is physical state verification, verifying whether the ambient temperature has reached the critical temperature of 68°C for the VO2 phase transition; the second level is optical key verification, verifying whether the incident light is in a specific polarization state; and the third level is phase superposition verification, verifying the static phase φ. 1 With dynamic phase φ 2 The system checks whether the stacking logic is correct; if any level of verification fails, the system returns to static encryption mode.

7. The method according to claim 5, characterized in that, In step S4, the phase φ 1 φ 2 Each is discrete into a 2-bit coded state, corresponding to phase values ​​of 0°, 90°, 180°, and 270° respectively.

8. The method according to claim 5, characterized in that, In step S2, under static encryption mode, the Si nanorod array generates false patterns A and B for x-polarized light and y-polarized light, respectively.

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