Three-channel information encryption storage design method based on unit cell superstructure surface

Abstract

The application is suitable for the field of micro-nano optical technology, and provides a three-channel information encryption storage design method based on a unit cell superstructure surface.The superstructure surface designed by the method is composed of unit cell nano unit structures with the same geometric size and only slightly different direction angles. The three-channel information encryption storage can be realized by using the rich design freedom of the unit cell nano unit structure, combining with the design methods such as Malus law and corner degeneracy. The information of each channel is independent and does not interfere with each other, which can greatly improve the information storage capacity of the superstructure surface. The wavelength, polarization and diffraction distance of the light wave are used as the key code to the three information channels, which greatly improves the information security. The application is expected to play an important role in the fields of mass data storage, super-compact image display, optical anti-counterfeiting, intelligent sensing, human-computer interaction, multi-functional diffractive optical element and multi-dimensional information encryption.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of micro-nano optics, and particularly relates to a three-channel information encryption storage design method based on a unit cell superstructure surface. BACKGROUND

[0002] With the continuous emergence of emerging technologies such as 5G communication and artificial intelligence, the total amount of information is showing explosive growth, and current information technology is facing unprecedented challenges. Optical information storage and encryption technology, which uses photons as information carriers, has many advantages such as low energy consumption, long life, high density, and resistance to electromagnetic radiation interference, and is gradually becoming one of the sustainable technical solutions to meet the growing data capacity and security needs in the big data era.

[0003] Optical information storage and encryption is the most important link in the optical information technology chain, and high-density, high-capacity, and high-reliability information security storage is increasingly important in national security, intelligent sensing, advanced display, and other fields. Light carries multiple physical parameters such as polarization, wavelength, amplitude, and phase, making it an ideal carrier for information storage and encryption. By controlling optical parameters, not only can light-matter interactions be controlled, but also ciphertexts and keys can be formed to construct multiple information channels, enabling high-capacity, high-density, high-security, and multi-functional multi-dimensional multiplexed optical information storage and encryption technology. SUMMARY

[0004] Therefore, the present application provides a three-channel information encryption storage design method based on a unit cell superstructure surface, aiming to realize a superstructure surface device with high information storage capacity and high security.

[0005] The first aspect of the present application provides a three-channel information encryption storage design method based on a unit cell superstructure surface, comprising:

[0006] 1. Optimizing the design of the unit cell nano unit structure.

[0007] The following will be described taking a cuboid as an example. The length, width, and height of the unit cell nano unit structure are all subwavelength. As shown in Figure 1 , the unit cell nano unit structure is composed of a substrate 2 and 3 and a nano brick 1 etched on the substrate, an xyz rectangular coordinate system is established, the length of the nano brick is L, the width is W, the height in the z direction is H, the edge length of the substrate in the x and y directions is C, and the angle between L and the x direction is the directional angle a. A plurality of unit cell nano unit structures are arranged at equal intervals in the x and y directions to form a superstructure surface device as shown in Figure 2 .

[0008] Two different working wavelengths λ1 and λ2 are determined, and the size parameters of the unit cell nano-unit structure are optimized by electromagnetic simulation software, so that the unit cell nano-unit structure can be equivalent to a micro-nano half-wave plate at the working wavelength λ1, and can be equivalent to a micro-nano polarizer at the working wavelength λ2.

[0009] 2. A method for designing a directional angle of a super-structured surface.

[0010] First, a gray-scale image image1 composed of MxN pixels with 256 (0-255) gray levels is selected as the near-field nano-printed image of channel one.

[0011] According to Malus law, when the x-ray polarized light is incident on the unit cell nano-unit structure with a directional angle of α, which can be equivalent to a micro-nano half-wave plate, if a polarizer with a transparent axis perpendicular to the x-axis is placed behind the unit cell nano-unit structure to form a perpendicular optical path, then the intensity of the outgoing light after the polarizer is

[0012] I out = I in sin 2 (2α) (1)

[0013] where I in is the incident light intensity.

[0014] Let I in = 255, and the gray value of the pixel in the image is I out1 . According to formula (1), four different nano-brick directional angles α1, α2, α3 and α4 can be obtained, as shown in Table 1, wherein the four angles satisfy the following relationships: α2 = 90° - α1, α3 = 90° + α1 and α4 = 180° - α1.

[0015] When the x-ray polarized light is incident on the unit cell nano-unit structure with a directional angle of α, which can be equivalent to a micro-nano polarizer, the intensity of the outgoing light is

[0016] I out = I in cos 2 α (2)

[0017] 3. A black-and-white binary image image2 composed of MxN pixels with only 0 and 255 gray values is selected as the near-field nano-printed image of channel two, and the pixel positions of image2 and image1 correspond one-to-one. As shown in Table 2, the directional angles α2 and α3 correspond to smaller gray values I low , so the nano-brick directional angle of the pixel with a gray value of 0 is selected as any one of α2 and α3; the directional angles α1 and α4 correspond to larger gray values I high , so the nano-brick directional angle of the pixel with a gray value of 255 is selected as any one of α1 and α4. Figure 3 ​high (I high >I low ), so the pixel with the gray value of 255 corresponds to any one of the direction angles a1 and a4 of the nanobrick.

[0018] If the incident light is circularly polarized light, after passing through the unit cell nanometer unit structure which can be equivalent to a micro-nano half-wave plate, the outgoing light becomes reverse circularly polarized light with an additional phase The size satisfies the following formula:

[0019]

[0020] On the basis of realizing the two-channel nanometer printing image display, the direction angle of the nanobrick can also provide two-step geometric phase control quantities, that is, one of 2a2 and 2a3, or one of 2a1 and 2a4, as shown in the following formula: Figure 3 Select any one gray-scale image image3 as the far-field holographic image of channel three, and use the simulated annealing algorithm to obtain the final direction angle distribution a.

[0021] The unit cell nanometer unit structure with the same size of MxN nanobricks and arranged according to the direction angle arrangement matrix a is arranged at equal intervals in the x and y directions to form a unit cell metasurface device capable of realizing three-channel information encryption storage.

[0022] 4. Expected function: when the incident x-ray polarized light with a wavelength of l1, a polarizer with a transparent axis along the y axis is inserted in the direction of the outgoing light of the device, the nanometer printing image stored in channel one can be decoded in the near field, and the effect is as shown in the following formula: Figure 7 When the incident x-ray polarized light with a wavelength of l2, the nanometer printing image in channel two can be displayed in the near field, and the effect is as shown in the following formula: Figure 8 When the incident circularly polarized light with a wavelength of l1, the holographic image in channel three can be projected in the far field, and the effect is as shown in the following formula: Figure 9 Finally, three-channel information encryption storage is realized.

[0023] Optionally, the unit cell nanometer unit structure is composed of a substrate and nanobricks on the substrate, but is not limited thereto.

[0024] Optionally, the unit cell nanometer unit structure is made of SOI material, the substrate is a double-layer substrate composed of silicon dioxide and silicon, and the nanobrick material is silicon, but is not limited thereto. The working mode of the designed metasurface device is reflective, but is not limited thereto.

[0025] Optionally, the size parameters of the unit cell nanometer unit structure include the length L, width W, height H and direction angle a of the nanobrick, and the side length C of the substrate, but are not limited thereto.

[0026] Optionally, the working wavelength λ1 is 630 nm, λ2 is 560 nm, the length L is 200 nm, the width W is 100 nm, the height H is 220 nm, and the side length of the substrate is 300 nm, but not limited thereto.

[0027] Compared with the prior art, the embodiment of the present application has the following beneficial effects:

[0028] (1) The superstructure designed based on the method of the present application is a unit cell structure, which is composed of unit cell nano unit structures with the same geometric size and different direction angles, greatly reducing the processing difficulty;

[0029] (2) The superstructure device designed based on the method of the present application can realize three-channel information storage, and there is no crosstalk between the information channels, greatly improving the information storage capacity of the device;

[0030] (3) The present application encodes the wavelength, polarization, diffraction distance, etc. of the light wave as a key to three information channels, greatly improving the information density and information security. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0032] Figure 1 is a schematic diagram of the unit cell nano unit structure provided by the embodiment of the present application;

[0033] Figure 2 is a structural schematic diagram of the three-channel information encryption storage superstructure device based on the unit cell superstructure provided by the embodiment of the present application;

[0034] Figure 3 is a design principle diagram for realizing three-channel information encryption storage based on the unit cell superstructure provided by the embodiment of the present application;

[0035] Figure 4 is a graph of the relationship between the long and short axis reflectivity of the designed unit cell nano structure and the wavelength provided by the embodiment of the present application;

[0036] Figure 5 is a design image of three-channel information provided by the embodiment of the present application;

[0037] Figure 6 is a direction angle matrix of the designed three-channel information encryption storage superstructure device provided by the embodiment of the present application;

[0038] Figure 7 This is a schematic diagram of the channel-one decoding method in reflection mode provided in an embodiment of the present invention;

[0039] Figure 8 This is a schematic diagram of the channel two decoding method in reflection mode provided in an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of the channel three-way decoding method in reflection mode provided in an embodiment of the present invention;

[0041] Figure 10 This is the simulation verification result of the three-channel information provided in the embodiment of the present invention. Detailed Implementation

[0042] To illustrate the technical solution described in this invention, specific embodiments are described below.

[0043] This invention provides a three-channel information encryption storage design method based on a unit cell metasurface. The metasurface designed by this method consists of unit cell nanounit structures with the same geometric dimensions but different orientation angles. Utilizing the rich design freedom of the unit cell nanounit structure, and combining design methods such as Malus's law and rotation degeneracy, three-channel information encryption storage can be achieved. The information in each channel is independent and does not interfere with each other, which can greatly improve the information storage capacity of the metasurface. Encoding the wavelength, polarization, and diffraction distance of light waves as keys into the three information channels greatly improves information security.

[0044] In this embodiment, as Figure 1 As shown, the unit cell nanounit structure uses SOI material and consists of a bilayer substrate 2 (made of silicon dioxide) and 3 (made of silicon), as well as silicon nanobricks 1 etched on the substrate.

[0045] The specific design steps are as follows:

[0046] 1. Optimize the design of unit cell nanounit structure.

[0047] The following explanation uses a cuboid-shaped unit cell nanostructure as an example. The length, width, and height of the unit cell nanostructure are all subwavelength. For example... Figure 1 As shown, the unit cell nanounit structure consists of substrates 2 and 3 and nanobricks 1 etched on the substrates. An xyz rectangular coordinate system is established. The length of the nanobrick is L, the width is W, and the height in the z direction is H. The side length of the substrate in the x and y directions is C. The angle between L and the x direction is the direction angle α.

[0048] Two working wavelengths 630 nm and 560 nm are determined, and the size parameters of the unit cell nano-unit structure are optimized by electromagnetic simulation software at a direction angle α = 0, and the optimized nano-unit size is: the length L is 200 nm, the width W is 100 nm, the height H is 220 nm, and the side length of the substrate is 300 nm. The relationship between the reflectivity and phase difference corresponding to the long axis and short axis of the nano-brick and the wavelength is shown in Figure 4 It can be seen that the unit cell nano-unit structure of this size can be equivalent to a micro-nano half-wave plate at a working wavelength of 630 nm, and can be equivalent to a micro-nano polarizer at a working wavelength of 560 nm:

[0049] 2. The direction angle design method of the super-structured surface.

[0050] First, a gray image image1 with 256 (0-255) gray levels composed of 500x500 (i.e. M=N=500) pixels is selected as a near-field nano-printing image of channel one, as shown in Figure 5 .

[0051] According to Malus' law, when x-ray polarized light is incident on the unit cell nano-unit structure equivalent to a micro-nano half-wave plate with a direction angle α, if a polarizer with a transparent axis direction orthogonal to the x-axis is placed behind the unit cell nano-unit structure, an orthogonal optical path is formed, and the exit light intensity after the polarizer is

[0052] I out = I in sin 2 (2α) (1)

[0053] Where I in is the incident light intensity.

[0054] Let I in = 255, and the gray value of the pixel in the image is I out1 . According to formula (1), four different nano-brick direction angles α1, α2, α3 and α4 can be obtained, as shown in Figure 3 , and the four angles satisfy the following relationships: α2 = 90°-α1, α3 = 90°+α1 and α4 = 180°-α1.

[0055] When x-ray polarized light is incident on the unit cell nano-unit structure equivalent to a micro-nano polarizer with a direction angle α, the exit light intensity is

[0056] I out = I in cos 2 α (2)

[0057] Next, select a black and white binary image (image2) consisting of M×N pixels with grayscale values ​​of only 0 and 255, as the near-field nanoprinting image for channel two, such as... Figure 5 As shown, the pixel positions of image2 and image1 correspond one-to-one. Figure 3 As shown, the orientation angles α2 and α3 correspond to relatively small grayscale values ​​I. low Therefore, the orientation angle of the nanobrick corresponding to a pixel with a grayscale value of 0 can be either α2 or α3; orientation angles α1 and α4 correspond to relatively large grayscale values ​​I. high (I high >I low Therefore, the orientation angle of the nanobrick corresponding to a pixel with a grayscale value of 255 can be either α1 or α4.

[0058] If the incident light is circularly polarized, after passing through a unit cell nanostructure that can be equivalent to a micro / nano half-wave plate, the outgoing light becomes reverse-polarized and carries an additional phase. Its size satisfies the following formula:

[0059]

[0060] Building upon the aforementioned two-channel nanoprinted image display, the orientation angle of the nanobricks can also provide two-step geometric phase modulation values, namely one of 2α2 and 2α3, or one of 2α1 and 2α4, such as... Figure 3 As shown. Select any grayscale image image 3 as the far-field holographic image of channel three, as follows. Figure 5 As shown, the final orientation angle distribution α is obtained by optimizing using the simulated annealing algorithm, as follows: Figure 6 As shown.

[0061] Arranging 500×500 uniformly sized, orientation-angled unit-cell nanounits at equal intervals along the x and y directions according to an orientation-angle matrix α creates a unit-cell metasurface device capable of encrypting and storing three-channel information. A schematic diagram is shown below. Figure 2 As shown.

[0062] 3. Using Rayleigh-Sommerfeld's formula, simulations were performed to obtain the effect diagrams of the designed metasurface device in the reflection space, such as... Figure 10 As shown. When incident with X-ray linearly polarized light of wavelength 610 nm, inserting an analyzer with its transmission axis along the y-axis in the direction of the emitted light from the device allows for near-field decoding of the nanoprinted image stored in channel one, with the effect shown. Figure 7 As shown; when incident with X-ray linearly polarized light at a wavelength of 560 nm, the nanoprinted image of channel two is displayed in the near field, and the effect is as follows. Figure 8 As shown; when circularly polarized light with an incident wavelength of 610nm is incident, a holographic image in channel three can be projected in the far field, with the effect as follows.Figure 9 The simulation results and the design are completely consistent, which proves the correctness of the method.

[0063] The super-structured surface device based on the application can display two gray scale images in the near field of the reflection space and project a holographic image in the far field, thereby realizing a two-in-one super-structured surface device with three information channels and greatly improving the information storage capacity of the device. In addition, in the design of the device, the wavelength, polarization, diffraction distance and the like of the light wave are encoded as keys to the three information channels, and three decryption methods are adopted to completely crack all the stored information, thereby significantly improving the security of the information storage.

[0064] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the application.

[0065] The application also provides a three-channel information encryption storage super-structured surface device based on a unit cell super-structured surface, which is designed according to the design method of the above embodiments.

[0066] The application can integrate two different functions and three information channels into the same super-structured surface device, and encode the wavelength, polarization, diffraction distance and the like of the light wave as keys to the three information channels, thereby greatly improving the information capacity and security. Using unit cell nanostructures can reduce the processing difficulty, and the application is expected to play an important role in scenarios such as mass data storage, ultra-compact image display, optical anti-counterfeiting, intelligent sensing, human-computer interaction, multi-functional diffractive optical elements, multi-dimensional information encryption and the like.

[0067] The above-described embodiments are only used to illustrate the technical solutions of the application, rather than limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application, and should be included in the protection scope of the application.

Claims

1. A three-channel information encryption storage design method based on a unit cell superstructure surface, characterized in that, The method comprises the following steps: Step one, two different working wavelengths λ1 and λ2 are preset, and the size parameters of the unit cell nano-unit structure are optimized by electromagnetic simulation software, so that the unit cell nano-unit structure can be equivalent to a micro-nano half-wave plate when the working wavelength is λ1, and can be equivalent to a micro-nano polarizer when the working wavelength is λ2; Step two, select a gray image image1 with 256 (0~255) gray levels composed of MxN pixels as the near-field nano-printing image of channel one; set the incident light intensity I in =255, the gray value of the pixel in the image is I out1 , according to the formula I out1 =I in sin 2 (2α), determine four different nano-brick direction angles α1, α2, α3 and α4, and the four angles satisfy the following relationship: α2=90°-α1, α3=90°+α1 and α4=180°-α1; Step three, select a black and white binary image image2 composed of MxN pixels with only 0 and 255 gray values as the near-field nano-printing image of channel two, image2 and image1 pixel positions one-to-one corresponding; the pixel with gray value 0 corresponds to a smaller gray value I low , the pixel corresponding direction angle of the nano brick selects any one of α2 and α3; the pixel with gray value 255 corresponds to a larger gray value I high (I high >I low , the pixel corresponding direction angle of the nano brick selects any one of α1 and α4; Step four, on the basis of realizing two-channel nano-printed image display, the directional angle of the nano-brick also provides two-step geometric phase control amount, i.e. one of 2α2 and 2α3, or one of 2α1 and 2α4; any one gray-scale image image3 is selected as the far-field holographic image of channel three, and the final directional angle distribution α is obtained by using the simulated annealing algorithm, and the corresponding phase distribution is Φ = 2α; Step five, the unit cell nano-unit structure with the same size and arranged according to the directional angle distribution α is arranged at equal intervals in the x and y directions to form a unit cell metasurface device capable of realizing three-channel information encryption storage; when the x-polarized light with the wavelength λ1 is incident, a polarizer with the optical axis along the y axis is inserted in the exit direction of the device, and the nano-printed image stored in channel one can be decoded in the near field; when the x-polarized light with the wavelength λ2 is incident, the nano-printed image stored in channel two can be displayed in the near field; when the circularly polarized light with the wavelength λ1 is incident, the holographic image stored in channel three can be projected in the far field.

2. The three-channel information encryption storage design method based on metasurface unit cells according to claim 1, wherein, The unit cell nano-unit structure is composed of a substrate and nano-bricks on the substrate, all the nano-bricks have the same geometric size and different directional angles.

3. The three-channel information encryption storage design method based on metasurface unit cells according to claim 2, wherein, The size parameters of the unit cell nano-unit structure include: The length L, the width W, the height H, the directional angle α of the nano-bricks, and the side length C of the substrate.

4. A three-channel information encryption storage metacell metasurface device, characterized in that, The unit cell metasurface device is designed according to the method of any one of claims 1 to 3.

Images