Terahertz single-pixel encryption metasurface and encryption method thereof

Abstract

The present application relates to a kind of terahertz single-pixel encryption super surface and its encryption method, the super surface is formed by n×n units, with random order, each time using one of the units to perform encryption operation on light field;When the terahertz wave carrying image information passes through one unit of the super surface, its light field phase will be modulated as the spatial distribution of 0 or π, terahertz wave is sequentially modulated by each unit of super surface and is collected by a single-pixel detector, and a single-pixel time sequence is obtained, the sequence is associated with the key of the phase distribution of each unit of super surface and the modulation order to carry out correlation calculation, reconstructs image information.The present application obtains terahertz single-pixel encryption super surface, using the characteristics of single-pixel imaging makes terahertz super surface encryption scheme have 10 90 The security of key space, the robustness that 97% still can be reconstructed when shielding light path, 30% fault tolerance, and avoid complex terahertz array detector.

Description

Technical Field

[0001] This invention belongs to the field of terahertz metasurface technology, specifically relating to a terahertz single-pixel encrypted metasurface and its encryption method. Background Technology

[0002] With the development of information technology, information security issues are becoming increasingly prominent. Terahertz metasurfaces can encrypt images or signals by controlling electromagnetic waves, effectively preventing unauthorized access or tampering and ensuring the security of data transmission and storage.

[0003] Existing terahertz metasurface encryption schemes have the following drawbacks and shortcomings: 1) The image information needs to be hidden in a specific channel, and the information can only be displayed when a specific range of temperature, light, or mechanical force is applied; 2) The key space is small, resulting in poor fault tolerance; 3) Lack of protection for wireless transmission. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a terahertz single-pixel encrypted metasurface and its encryption method. By utilizing single-pixel imaging technology and metasurface structure, a single-pixel encryption scheme based on a terahertz metasurface is achieved, which features a large key space, ultra-robust transmission, and key fault tolerance. In the future, it can realize an actively adjustable integrated encryption device.

[0005] The technical problem solved by this invention is achieved through the following technical solution: A terahertz single-pixel encryption metasurface is characterized in that: the metasurface is composed of n×n units, and the light field is encrypted by using one unit at a time in a random order; each unit has a side length of 24mm and a substrate thickness of 1mm; each unit is composed of several square pillars, each square pillar has a side length of 3mm and a thickness of 0.83mm; the operating wavelength of the metasurface is 0.3THz, which is in the terahertz band.

[0006] Furthermore, the prismatic distribution of the metasurface is a row-wise reconstruction of an n×n order Hadamard matrix, where n 2 The expression for an order-1 Hadamard matrix is: ; in: ; n is spatially distributed as 1 or -1 2 Each row of a Hadamard matrix can be reconstructed into an n×n unit matrix to obtain n. 2 Units.

[0007] A terahertz single-pixel encrypted metasurface encryption method, based on the aforementioned terahertz single-pixel encrypted metasurface, comprises the following steps: When a terahertz wave carrying image information passes through one unit of the metasurface, its optical field phase is modulated to a spatial distribution of 0 or π. The terahertz wave is modulated sequentially by each unit of the metasurface and collected by a single-pixel detector to obtain a single-pixel time series. This series is correlated with a key carrying the phase distribution and modulation order of each unit of the metasurface to reconstruct the image information. S1. The sender transmits the key to the receiver through a private channel, and the receiver can then obtain the phase distribution of the sequential encryption unit corresponding to the key. S2. The sender incident a terahertz wave carrying image information onto the metasurface, moves the metasurface according to the key sequence to encode the image, and then propagates it through a public channel. S3. The receiver focuses the terahertz wave passing through the metasurface in the public channel and collects it with a single-pixel detector. After each movement, a single-pixel complex amplitude is recorded, and finally a time-domain sequence is obtained. S4. The receiver uses an association calculation algorithm to reconstruct the image information by combining the key of the private channel and the single-pixel sequence of the public channel.

[0008] The advantages and beneficial effects of this invention are as follows: 1. This invention provides a terahertz single-pixel encrypted metasurface, utilizing the characteristics of single-pixel imaging to enable the terahertz metasurface encryption scheme to achieve 10 90 It offers security of the key space, robustness to reconstruct even when the optical path is blocked by 97%, and 30% fault tolerance, while avoiding the need for complex terahertz array detectors. Attached Figure Description

[0009] Figure 1 a) is a schematic diagram of the terahertz single-pixel encryption metasurface of the present invention; b) is a schematic diagram of the unit; c) is a schematic diagram of the phase distribution and encoding; Figure 2 This is a flowchart illustrating the encryption process of the present invention; Figure 3 This is a schematic diagram of the metasurface sample prepared by 3D printing according to the present invention; Figure 4 a) to d) are the image decoding results under the experimental conditions of no occlusion, 50% occlusion, 88% occlusion and 97% occlusion, respectively; Figure 5 a) to c) are the decoding results when the key is 90% correct, 70% correct, and 50% correct, respectively. Detailed Implementation

[0010] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0011] like Figure 1 As shown in (a), a terahertz single-pixel encryption metasurface is innovative in that: the metasurface is composed of n×n units, and the light field is encrypted using one unit at a time in a random order; each unit has a side length of 24mm and a substrate thickness of 1mm; each unit is composed of several square pillars, each square pillar having a side length of 3mm and a thickness of 0.83mm, as shown in (a). Figure 1 As shown in (b), the operating wavelength of the metasurface is 0.3 THz, which is in the terahertz band.

[0012] Furthermore, the prismatic distribution of the metasurface is a row-wise reconstruction of an n×n order Hadamard matrix, where n 2 The expression for an order-1 Hadamard matrix is: ; in: ; n is spatially distributed as 1 or -1 2 Each row of a Hadamard matrix can be reconstructed into an n×n unit matrix to obtain n. 2 Units.

[0013] right Figure 1 (c) illustrates the prismatic distribution of all units of the metasurface in the n=8 instance, derived from a row-wise reconstruction of a 64th-order Hadamard matrix. Encoding the 64 metasurface units allows for the creation of a 64-bit random key, such as "B8 E5 F3A1 D4...", with 10... 90 The key space.

[0014] like Figure 1 As shown in (c), the white squares represent 1, corresponding to the phase modulation of 0; the black squares represent -1, corresponding to the phase modulation of π.

[0015] like Figure 2 As shown, a terahertz single-pixel encrypted metasurface encryption method is proposed. Based on the aforementioned terahertz single-pixel encrypted metasurface, its innovation lies in the following steps: When a terahertz wave carrying image information passes through one unit of the metasurface, its optical field phase is modulated to a spatial distribution of 0 or π. The terahertz wave is modulated sequentially by each unit of the metasurface and collected by a single-pixel detector to obtain a single-pixel time series. This series is correlated with a key carrying the phase distribution and modulation order of each unit of the metasurface to reconstruct the image information. S1. The sender transmits the key to the receiver through a private channel, and the receiver can then obtain the phase distribution of the sequential encryption unit corresponding to the key. S2. The sender incident a terahertz wave carrying image information onto the metasurface, moves the metasurface according to the key sequence to encode the image, and then propagates it through a public channel. S3. The receiver focuses the terahertz wave passing through the metasurface in the public channel and collects it with a single-pixel detector. After each movement, a single-pixel complex amplitude is recorded, and finally a time-domain sequence is obtained. S4. The receiver uses an association calculation algorithm to reconstruct the image information by combining the key of the private channel and the single-pixel sequence of the public channel.

[0016] The sender encrypts plaintext (image information) into ciphertext (a time series of a terahertz field) using a random cell on the metasurface each time, transmitting it via terahertz waves in a public channel while simultaneously transmitting the key in a private channel. In the public channel, eavesdroppers and saboteurs may attempt to intercept or disrupt the information. Due to the security and robustness of single-pixel encryption, eavesdroppers lacking the key cannot decipher the information, and interference from saboteurs is unlikely to affect reception. The receiver reconstructs the image information by correlating the complex amplitude sequence of the terahertz field obtained from the single-pixel detector with the key.

[0017] This invention utilizes 3D printing technology to create, for example... Figure 3 The metasurface sample shown was subjected to terahertz single-pixel imaging experiments. Tests were conducted in optical paths with varying degrees of occlusion, such as... Figure 4 (a)~(d) show that the image information of the letters “N”, “K” and “U” can be reconstructed under the conditions of no occlusion, 50% occlusion, 88% occlusion and 97% occlusion, respectively, which verifies the robustness of the encryption scheme.

[0018] In addition, decoding is performed using keys with different accuracy rates, such as... Figure 5 As shown in (a)-(c), the image can still be reconstructed when the key accuracy is 90% and 70%, but the image cannot be reconstructed when the accuracy is 50%, which verifies the fault tolerance of the encryption scheme.

[0019] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A terahertz single-pixel encrypted metasurface device, characterized in that: The metasurface device is composed of n×n units, and the optical field is encrypted by using one unit at a time in a random order. Each unit has a side length of 24mm and a substrate thickness of 1mm. Each unit is composed of several square pillars, each of which has a side length of 3mm and a thickness of 0.83mm. The operating wavelength of the metasurface device is 0.3THz, which is in the terahertz band. The prismatic distribution of the metasurface device is a row-wise reconstruction of an n×n order Hadamard matrix, where n 2 The expression for an order-1 Hadamard matrix is: ； in: ; n is spatially distributed as 1 or -1 2 Each row of a Hadamard matrix can be reconstructed into an n×n unit matrix to obtain n. 2 Units; When a terahertz wave carrying image information passes through one unit of the metasurface device, its optical field phase is modulated to a spatial distribution of 0 or π. The terahertz wave is modulated sequentially by each unit of the metasurface device and collected by a single-pixel detector to obtain a single-pixel time series. This series is correlated with a key carrying the phase distribution and modulation order of each unit of the metasurface to reconstruct the image information.

2. A method for encrypting a terahertz single-pixel encrypted metasurface device, characterized in that: Based on the terahertz single-pixel encrypted metasurface device as described in claim 1, the steps of the method are as follows: S1. The sender transmits the key to the receiver through a private channel, and the receiver can then obtain the phase distribution of the sequential encryption unit corresponding to the key. S2. The sender incident a terahertz wave carrying image information onto the metasurface device, moves the metasurface according to the key sequence to encode the image, and then propagates it through a public channel. S3. The receiver focuses the terahertz wave passing through the metasurface device in the public channel and collects it with a single-pixel detector. After each movement, a single-pixel complex amplitude is recorded, and finally a time-domain sequence is obtained. S4. The receiver uses an association calculation algorithm to reconstruct the image information by combining the key of the private channel and the single-pixel sequence of the public channel.

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