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

Abstract

The invention is suitable for the technical field of micro-nano optics, and provides a three-channel information encryption storage design method based on a unit cell meta-structure surface, and the meta-structure surface designed by the method is composed of unit cell nano unit structures which are the same in geometric dimension and are not completely the same in direction angle. The information encryption storage of three channels can be realized by utilizing the rich design freedom degree of the unit cell nano unit structure and combining the Malus law, the corner degeneracy and other design methods. The information of each channel is mutually independent and does not interfere with each other, so that the information storage capacity of the super-structure surface can be greatly improved; and the wavelength, polarization, diffraction distance and the like of the light wave are coded to three information channels as secret keys, so that the information security is greatly improved. The method is expected to play an important role in scenes such as mass data storage, ultra-compact image display, optical anti-counterfeiting, intelligent sensing, man-machine interaction, multifunctional diffractive optical elements, multi-dimensional information encryption and the like.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano optical technology, and in particular relates to a three-channel information encryption storage design method based on a single-cell metasurface. Background Art

[0002] With the continuous emergence of emerging technologies such as 5G communications and artificial intelligence, the total amount of information has exploded, and current information technology is facing unprecedented challenges. Optical information storage and encryption technology using photons as information carriers has many advantages such as low energy consumption, long life, high density, and resistance to electromagnetic radiation interference. It is gradually becoming one of the sustainable technical solutions to cope with 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. High-density, large-capacity, and highly reliable information security storage is becoming increasingly important in the fields of national defense security, intelligent sensing, and advanced display. Light waves carry multidimensional physical parameters such as polarization, wavelength, amplitude, and phase, and are ideal carriers for information storage and encryption. By regulating optical parameters, not only can the interaction between light and matter be manipulated, but ciphertext and keys can also be formed, and multiple information channels can be constructed to achieve large-capacity, high-density, high-security, and multi-functional multi-dimensional multiplexed optical information storage and encryption technology. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a three-channel information encryption storage design method based on a single-cell metasurface, aiming to realize a metasurface device with high information storage capacity and high security.

[0005] A first aspect of an embodiment of the present invention provides a three-channel information encryption storage design method based on a single-cell metasurface, comprising:

[0006] 1. Optimize the design of single-cell nanostructure.

[0007] The following is an example of a single-cell nanostructure that is a rectangular parallelepiped. The length, width, and height of the single-cell nanostructure are all sub-wavelength. Figure 1 As shown, the single-cell nanostructure is composed 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, the height in the z direction is H, the side lengths of the substrate in the x and y directions are both C, and the angle between L and the x direction is the direction angle α. Multiple single-cell nanostructures are arranged at equal intervals in the x and y directions to form a structure as shown in FIG. Figure 2 The metasurface device shown.

[0008] Determine two different operating wavelengths λ 1 and λ 2, the size parameters of the single-cell nanostructure are optimized by electromagnetic simulation software, so that the single-cell nanostructure can be operated at a wavelength of λ 1 When the working wavelength is λ 2 It can be equivalent to a micro-nano polarizer.

[0009] 2. Direction angle design method of metasurface.

[0010] First, a grayscale image image1 consisting of M×N pixels and having 256 (0-255) grayscale levels is selected as the near-field nanoprinting image of channel one.

[0011] According to Malus's law, when x-polarized light is incident on a single-cell nanostructure with a direction angle of α, which is equivalent to a micro-nano half-wave plate, if a polarizer with a transmission axis orthogonal to the x-axis is placed behind the single-cell nanostructure to form an orthogonal optical path, the intensity of the outgoing light after passing through the polarizer is

[0012] I out = I in sin 2 (2α) (1)

[0013] Among them, I in is the incident light intensity.

[0014] Let I in =255, the gray value of the pixel in the image is I out1 According to formula (1), four different nanobrick direction angles α can be obtained. 1 , α 2 , α 3 and α 4 ,like Figure 3 As shown, the four angles satisfy the following relationship: α 2 =90°-α 1 , α 3 =90°+α 1 and α 4 =180°-α 1 .

[0015] When the x-polarized light is incident on a single-cell nanostructure with a direction angle of α, which is equivalent to a micro-nano polarizer, the intensity of the outgoing light is

[0016] I out = I in cos 2 α (2)

[0017] 3. 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 of channel 2. The pixel positions of image2 and image1 correspond one to one. Figure 3 As shown, the direction angle α 2 and α 3 Corresponding to a relatively small gray value I low Therefore, the nanobrick direction angle corresponding to the pixel with gray value 0 is α 2 and α 3 Any one of the following; direction angle α 1 and α 4 Corresponding to a relatively large gray value I high (I high >I low ), so the nanobrick direction angle corresponding to the pixel with gray value of 255 is α 1 and α 4 Any one of .

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

[0019]

[0020] On the basis of realizing the two-channel nanoprinting image display mentioned above, the orientation angle of the nanobrick can also provide two steps of geometric phase control, namely 2α 2 and 2α 3 One of the , or 2α 1 and 2α 4 One of Figure 3 As shown in Figure 2, any grayscale image image3 is selected as the far-field holographic image of channel three, and the simulated annealing algorithm is used to optimize the final directional angle distribution α.

[0021] A single-cell nanounit structure with M×N nanobricks of uniform size and angular arrangement according to an angular arrangement matrix α is arranged at equal intervals in the x and y directions to form a single-cell metasurface device that can realize three-channel information encryption storage.

[0022] 4. Expected function: When the incident wavelength is λ 1 When the x-polarized light is transmitted, a polarizer with the transmission axis along the y-axis is inserted in the direction of the outgoing light of the device, and the nano-printed image stored in channel 1 can be decoded in the near field. The effect is as follows Figure 7 As shown; when the incident wavelength is λ 2 When the x-polarized light is used, the nano-printed image of channel 2 is displayed in the near field, and the effect is as follows Figure 8As shown; when the incident wavelength is λ 1 When circularly polarized light is used, the holographic image in channel three can be projected in the far field. Fig. 9 As shown, the encrypted storage of information in three channels is finally achieved.

[0023] Optionally, the single-cell nanostructure is composed of a substrate and nanobricks on the substrate, but is not limited thereto.

[0024] Optionally, the single-cell nanostructure structure uses SOI material, the substrate is a double-layer substrate composed of silicon dioxide and silicon, and the nanobrick material is silicon, but not limited to this. The working mode of the designed metasurface device is reflective, but not limited to this.

[0025] Optionally, the size parameters of the single-cell nanostructure include the length L, width W, height H, direction angle α and side length C of the substrate of the nanobrick, but are not limited thereto.

[0026] Optional, operating wavelength λ 1 Select 630nm, λ 2 560nm is selected, the length L is 200nm, the width W is 100nm, the height H is 220nm, and the side length of the substrate is 300nm, but it is not limited to this.

[0027] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0028] (1) The metasurface designed based on the method of the present invention is a single-cell structure. The metasurface is composed of single-cell nanostructures with the same geometric size but different orientation angles, which greatly reduces the difficulty of processing;

[0029] (2) The metasurface device designed based on the method of the present invention can realize information storage in three channels, and there is no crosstalk between the information channels, which greatly improves the information storage capacity of the device;

[0030] (3) The present invention greatly improves information density and information security by encoding the wavelength, polarization, diffraction distance, etc. of the light wave as keys into three information channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 is a schematic diagram of a single-cell nanostructure provided by an embodiment of the present invention;

[0033] Figure 2 It is a schematic structural diagram of a three-channel information encryption storage metasurface device based on a single-cell metasurface provided in an embodiment of the present invention;

[0034] Figure 3 This is a design principle diagram for realizing three-channel information encryption storage based on a single-cell metasurface provided by an embodiment of the present invention;

[0035] Figure 4 is a graph showing the relationship between the long and short axis reflectivity and the wavelength of the designed single cell nanostructure provided in an embodiment of the present invention;

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

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

[0038] Figure 7 Schematic diagram of a channel one decoding method in a reflection mode provided by an embodiment of the present invention;

[0039] Figure 8 2 is a schematic diagram of a channel 2 decoding method in a reflection mode provided by an embodiment of the present invention;

[0040] Fig. 9 2 is a schematic diagram of a channel three decoding method in a reflection mode provided by an embodiment of the present invention;

[0041] Fig.10 This is a three-channel information simulation verification result provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to illustrate the technical solution of the present invention, a specific embodiment is provided below for illustration.

[0043] The embodiment of the present invention provides a three-channel information encryption storage design method based on a single-cell metasurface, wherein the metasurface designed by the method is composed of single-cell nanostructures with the same geometric dimensions but different orientation angles. By utilizing the rich design freedom of the single-cell nanostructure, combined with design methods such as Malus's law and angle degeneracy, three-channel information encryption storage can be achieved. The information of each channel is independent of each other and does not interfere with each other, which can greatly improve the information storage capacity of the metasurface; the wavelength, polarization, diffraction distance, etc. of the light wave are encoded as keys into the three information channels, which greatly improves the information security.

[0044] In this embodiment, Figure 1As shown, the single-cell nanostructured structure is made of SOI material and is composed of a double-layer substrate 2 (made of silicon dioxide) and 3 (made of silicon), and a silicon nanobrick 1 etched on the substrate.

[0045] The specific design steps are as follows:

[0046] 1. Optimize the design of single-cell nanostructure.

[0047] The following is an example of a single-cell nanostructure that is a rectangular parallelepiped. The length, width, and height of the single-cell nanostructure are all sub-wavelength. Figure 1 As shown, the single-cell nanostructure is composed of substrates 2 and 3 and a nanobrick 1 etched on the substrate, and an xyz rectangular coordinate system is established. The length of the nanobrick is L, the width is W, the height in the z direction is H, the side lengths of the substrate in the x and y directions are both C, and the angle between L and the x direction is the direction angle α.

[0048] Two working wavelengths of 630nm and 560nm were determined. When the direction angle α = 0, the size parameters of the single-cell nanounit structure were optimized by electromagnetic simulation software. The optimized nanounit size is: length L is 200nm, width W is 100nm, height H is 220nm, and the side length of the substrate is 300nm. The relationship between the reflectivity and phase difference of the long axis and short axis of the nanobrick and the wavelength is as follows: Figure 4 As shown, it can be seen that the single-cell nanostructure of this size can be equivalent to a micro-nano half-wave plate when the working wavelength is 630nm, and can be equivalent to a micro-nano polarizer when the working wavelength is 560nm:

[0049] 2. Direction angle design method of metasurface.

[0050] First, a grayscale image image1 consisting of 500×500 (i.e., M=N=500) pixels and having 256 (0-255) grayscale levels is selected as the near-field nanoprinting image of channel 1, as shown in FIG. Figure 5 shown.

[0051] According to Malus's law, when x-polarized light is incident on a single-cell nanostructure with a direction angle of α, which is equivalent to a micro-nano half-wave plate, if a polarizer with a transmission axis orthogonal to the x-axis is placed behind the single-cell nanostructure to form an orthogonal optical path, the intensity of the outgoing light after passing through the polarizer is

[0052] I out = I in sin 2 (2α) (1)

[0053] Among them, I in is the incident light intensity.

[0054] Let I in =255, the gray value of the pixel in the image is I out1 According to formula (1), four different nanobrick direction angles α can be obtained. 1 , α 2 , α 3 and α 4 ,like Figure 3 As shown, the four angles satisfy the following relationship: α 2 =90°-α 1 , α 3 =90°+α 1 and α 4 =180°-α 1 .

[0055] When the x-polarized light is incident on a single-cell nanostructure with a direction angle of α, which is equivalent to a micro-nano polarizer, the intensity of the emitted light is

[0056] I out = I in cos 2 α (2)

[0057] Then, a black-and-white binary image image2 consisting of M×N pixels with grayscale values ​​of only 0 and 255 is selected as the near-field nanoprinting image of channel 2, as shown in FIG. Figure 5 As shown, the pixel positions of image2 and image1 correspond one to one. Figure 3 As shown, the direction angle α 2 and α 3 Corresponding to a relatively small gray value I low Therefore, the nanobrick direction angle corresponding to the pixel with gray value 0 is α 2 and α 3 Any one of the following; direction angle α 1 and α 4 Corresponding to a relatively large gray value I high (I high >I low ), so the nanobrick direction angle corresponding to the pixel with a gray value of 255 is α 1 and α 4 Any one of .

[0058] If the incident light is circularly polarized light, after passing through the single-cell nanostructure which is equivalent to a micro-nano half-wave plate, the outgoing light becomes reverse circularly polarized light with an additional phase Its size satisfies the following formula:

[0059]

[0060] On the basis of realizing the two-channel nanoprinting image display mentioned above, the orientation angle of the nanobrick can also provide two steps of geometric phase control, namely 2α 2 and 2α 3 One of the , or 2α 1 and 2α 4 One of Figure 3 As shown. Select any grayscale image image 3 as the far-field holographic image of channel three, as Figure 5 As shown in the figure, the simulated annealing algorithm is used to optimize the final direction angle distribution α, as shown in Figure 6 shown.

[0061] 500×500 single-cell nanostructures with the same size and directional angles arranged in the directional angle arrangement matrix α are arranged at equal intervals in the x and y directions to form a single-cell metasurface device that can realize three-channel information encryption storage. The structural schematic diagram is shown in Figure 2 shown.

[0062] 3. The Rayleigh-Sommerfeld formula is used to simulate and calculate the effect diagram of the designed metasurface device in the reflection space, such as Fig.10 When the incident wavelength is 610nm x-polarized light, insert a polarizer with the transmission axis along the y-axis in the outgoing light direction of the device, and the nano-printed image stored in channel 1 can be decoded in the near field. The effect is as follows Figure 7 As shown; when the incident wavelength is 560nm x-polarized light, the nano-printed image of channel 2 is displayed in the near field, the effect is as follows Figure 8 As shown; when the incident wavelength is 610nm circularly polarized light, the holographic image in channel three can be projected in the far field, the effect is as follows Fig. 9 As shown in the figure, the encrypted storage of information in three channels is finally realized. The simulation results are completely consistent with the design, which proves the correctness of this method.

[0063] The metasurface device based on the present invention can display two grayscale images in the near field of the reflection space and project a holographic image in the far field, thereby realizing a functional two-in-one metasurface device with three information channels, which greatly improves the information storage capacity of the device. In addition, when designing the device, the wavelength, polarization, diffraction distance, etc. of the light wave are encoded as keys into the three information channels, and three decryption methods are used to completely crack all stored information, which significantly improves the security of information storage.

[0064] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0065] An embodiment of the present invention further provides a three-channel information encryption storage metasurface device based on a single-cell metasurface, and the device is designed according to the design method of the above embodiment.

[0066] The present invention can integrate two different functions and three information channels into the same metasurface device, and encode the wavelength, polarization, diffraction distance, etc. of the light wave as keys into the three information channels, greatly improving the information capacity and security. The use of single-cell nanostructures can reduce the difficulty of processing. The present invention 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, multifunctional diffractive optical elements, and multi-dimensional information encryption.

[0067] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A three-channel information encryption storage design method based on a single-cell metasurface, characterized in that: include: Step 1: Preset two different working wavelengths λ1 and λ2, and optimize the size parameters of the single-cell nanostructure by electromagnetic simulation software, so that the single-cell nanostructure 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 2: Select a grayscale image image1 consisting of M×N pixels with 256 (0-255) grayscale levels as the near-field nanoprinting image of channel 1; set the incident light intensity I in =255, the gray value of the pixel in the image is I out1 , according to formula I out1 =I in sin 2 (2α), determine four different nanobrick 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 3: Select a black-and-white binary image image2 composed of M×N pixels with grayscale values ​​of only 0 and 255 as the near-field nanoprinting image of channel 2. The pixel positions of image2 and image1 correspond one to one; pixels with a grayscale value of 0 correspond to relatively small grayscale values ​​I low The nanobrick direction angle corresponding to the pixel is selected from any one of α2 and α3; the pixel with a gray value of 255 corresponds to a relatively large gray value I high (I high >I low ), the nanobrick direction angle corresponding to the pixel is selected from any one of α1 and α4; Step 4: On the basis of realizing the two-channel nano-printed image display, the azimuth angle of the nano-brick also provides two steps of geometric phase control, namely, one of 2α2 and 2α3, or one of 2α1 and 2α4; select any grayscale image image3 as the far-field holographic image of channel three, and use the simulated annealing algorithm to optimize the final azimuth angle distribution α, and its corresponding phase distribution is Φ=2α; Step 5. Arrange M×N single-cell nanounit structures with uniform size of nanobricks and directional angles arranged according to directional angle distribution α at equal intervals in the x and y directions to form a single-cell metasurface device that can realize three-channel information encryption storage; when the incident x-polarized light with a wavelength of λ1 is received, a polarizer with a transmission axis along the y-axis is inserted in the outgoing light direction of the device, and the nano-printed image stored in channel one can be decoded in the near field; when the incident x-polarized light with a wavelength of λ2 is received, the nano-printed image stored in channel two is displayed in the near field; when the incident circularly polarized light with a wavelength of λ1 is received, 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 a single-cell metasurface as claimed in claim 1, characterized in that: The single-cell nanostructure is composed of a substrate and nanobricks on the substrate, and all nanobricks have the same geometric dimensions but different orientation angles.

3. The three-channel information encryption storage design method based on a single-cell metasurface as claimed in claim 2 is characterized in that: The size parameters of the single-cell nanostructure include: The length L, width W, height H, orientation angle α and side length C of the nanobrick.

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

Images