Metasurface for realizing four-channel two-dimensional code and its design method

Abstract

The present invention discloses a metasurface for realizing four-channel two-dimensional codes and a design method thereof. By combining different spectral responses of different nanobricks and intensity modulation under different polarizer combinations, a metasurface device can be used to realize the display of up to four two-dimensional codes. The four two-dimensional codes are combined to jointly restore the encoded information, which has the characteristics of high security and high information density.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano optical technology, and in particular to a metasurface for realizing a four-channel two-dimensional code and a design method thereof. Background Art

[0002] Two-dimensional code technology is widely used in daily life. People cannot do without it when traveling, shopping, and riding. However, two-dimensional codes are now facing two problems: 1. Insufficient information density. Once the grayscale distribution of a two-dimensional code is fixed, it cannot be changed, and the information density is low. 2. Insufficient security. In some situations where encryption is required, the information contained in the two-dimensional code is difficult to hide. In response to the above problems, the present invention cleverly combines the spectral response of the metasurface with the Malus law based on the polarization state to design a four-channel two-dimensional code. Four two-dimensional code channels can be designed on a scale of hundreds of microns, and the information density is extremely high. Moreover, each channel requires a special decoding method, which has the characteristics of high security. Summary of the Invention

[0003] To significantly improve the security and information density of QR codes, this invention provides a metasurface capable of displaying four QR codes under different incidence conditions. This invention, for the first time, utilizes a simple structure and ingenious methods to achieve the display of four binary patterns. This invention has broad applications in fields such as information encryption, storage, and anti-counterfeiting.

[0004] One of the purposes of the present invention is to provide a metasurface that can realize four-channel QR codes. Combining Malus's law and spectral optics and its design method, the four-channel QR code designed by this method can observe four different QR codes under four incident conditions, and the QR code area is on the order of hundreds of microns, with the characteristics of high security and high information density.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for designing a metasurface for implementing a four-channel two-dimensional code, characterized in that it comprises the following steps:

[0007] S1: Optimizing a nanobrick unit structure with polarizer characteristics: Determine an operating wavelength λ, and optimize the dimensional parameters of two nanobrick unit structures of different sizes, namely, nanobrick a and nanobrick b, using electromagnetic simulation software. Optimize the nanobrick unit structure with polarizer characteristics so that when linearly polarized light at the same operating wavelength is incident on the nanobrick unit structure, for the two different sized bricks, the components polarized along the long axis are completely reflected, and the components polarized along the short axis are completely transmitted; the nanobrick unit structure is composed of a substrate and nanobricks etched on the substrate; the dimensional parameters of the nanobrick unit structure include the length L, width W, height H, and center spacing C of the nanobricks;

[0008] S2: Select four QR code patterns, namely QR code #1, QR code #2, QR code #3, and QR code #4; divide the information to be encrypted into four parts and assign them to the four QR codes respectively; design the nanobrick corner arrangement: According to step S1, two different sizes of nanobricks a and nanobricks b are equivalent to a polarizer at an operating wavelength of λ; set the operating wavelength to λ, and according to the formula for the output light intensity after the incident polarized light passes through the nanounit structure and the analyzer in sequence:

[0009]

[0010] Set three rotation angle combinations of polarizer and analyzer;

[0011] When the polarizer angle is π / 2 and the analyzer angle is 0, the intensity expression of the outgoing light is: I r1 =I0sin 2 2θ;

[0012] When the polarizer angle is 5π / 8 and the analyzer angle is -π / 8, the intensity expression of the outgoing light is:

[0013] When the polarizer rotation angle is -π / 8 and the analyzer rotation angle is 3π / 8, the intensity expression of the outgoing light is:

[0014] When the nanobrick rotation angle is 1π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 0, and 1 respectively;

[0015] When the nanobrick rotation angle is 3π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 0, and 1 respectively;

[0016] When the rotation angle of the nanobrick is 5π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 0, 0;

[0017] When the nanobrick rotation angle is 7π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 0, 0;

[0018] When the nanobrick rotation angle is 9π / 16, I r1 , I r2 , Ir3 The grayscales are approximately equivalent to 0, 1, and 1 respectively;

[0019] When the nanobrick rotation angle is 11π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 1, 1;

[0020] When the nanobrick rotation angle is 13π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 1, and 0 respectively;

[0021] When the nanobrick rotation angle is 15π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 1, and 0 respectively;

[0022] Thus, for each nanobrick, there are 8 corners to choose from to satisfy all grayscale combinations of the three QR codes QR code #1, QR code #2, and QR code #3 (8=2 3 ), that is, by reasonably selecting the rotation angle of the nanobrick, three different QR codes can be observed under the above three incident conditions;

[0023] S3: Design the size arrangement of nanobricks: Since the two different sizes of nanobricks have different spectral responses, they will show different colors when natural light is incident. Select QR code #4 and determine the size arrangement of nanobricks based on the grayscale distribution of QR code #4. When the grayscale of the pixel point of QR code #4 is 1, nanobrick a is selected, and when the grayscale of the pixel point of QR code #4 is 0, nanobrick b is selected.

[0024] As a preferred solution, in step S1, the operating wavelength is selected as 533 nm; when the operating wavelength is selected as 533 nm, the length L of the nanobrick a is a is 220nm, and the length L of the nanobrick b is b The unit structure center spacing C is 300nm.

[0025] In a second aspect, the present invention provides a metasurface for realizing a four-channel two-dimensional code, characterized in that the base material is alumina and the nanobrick material is silicon.

[0026] As a preferred solution, (1) the nano brick material is S i , the base material is Al2O3.

[0027] Furthermore, the two-dimensional code is composed of two nanobricks of different sizes, namely nanobrick a and nanobrick b; the two nanobricks, namely nanobrick a and nanobrick b, are equivalent to polarizers and have different spectral responses, showing different colors when white light is incident;

[0028] When linearly polarized light is incident, three different QR codes, #1, #2, and #3, can be produced by changing the rotation angle combination of the analyzer.

[0029] When white non-polarized light is incident, a QR code #4 can be displayed.

[0030] The advantages and beneficial effects of the present invention are as follows:

[0031] 1. The design method of the present invention is simple. It only needs to change the orientation angle and size of the nanobrick unit structure to achieve four-channel binary image display.

[0032] 2. The four-channel two-dimensional code display technology designed by the present invention has a large information capacity and can display four two-dimensional codes within a size of 100 microns).

[0033] 3. The four-channel two-dimensional code display technology designed by the present invention is simple and compact, small in size, light in weight, and easy to be highly integrated, and is suitable for the development trend of miniaturization and micro-miniaturization of optical systems.

[0034] 4. The four-channel two-dimensional code metasurface processing method designed by the present invention is simple and can be prepared based on mature SOS materials, which has the foundation for large-scale manufacturing.

[0035] 5. The four-channel QR code designed by the present invention has the characteristics of high security and requires a specific polarization and spectrum combination of the incident light to decode the required QR code. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of the nanobrick unit structure of the present invention;

[0037] Figure 2 is the reflectivity of the two nanobrick unit structures designed in the present invention;

[0038] Figure 3 This is a schematic diagram of the optical path for decoding QR code #1, QR code #2, and QR code #3. The corresponding analyzer polarization combinations are (π / 2, 0), (5π / 8, -π / 8), and (-π / 8, 3 / 8), respectively.

[0039] Figure 4 This is the optical path diagram for decoding QR code #4;

[0040] Figure 5 This is the simulated display effect of QR code #1 in the present invention;

[0041] Figure 6 This is the simulated display effect of QR code #2 in the present invention;

[0042] Figure 7 This is the simulated display effect of QR code #3 in the present invention;

[0043] Figure 8 This is the simulated display effect of QR code #4 in the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] 1. Optimize the design of two different sized nanobrick unit structures with polarizer function.

[0047] The following description will be made by taking a nanobrick unit structure as a cuboid as an example, wherein the length, width and height of the nanobrick unit structure are all sub-wavelength.

[0048] like Figure 1 As shown, an xyz rectangular coordinate system is established, the long side direction of the nanobrick unit structure represents the major axis, the short side direction represents the minor axis, Φ is the angle between the major axis of the nanobrick unit structure and the x-axis, that is, the direction angle of the nanobrick unit structure (the value range of Φ is 0° to 180°), as shown Figure 1 shown.

[0049] The working wavelength is selected as 533nm, and the size parameters of the two sets of nanobrick unit structures are optimized by electromagnetic simulation software, including the height H, length L, width W of the nanobrick unit structure 1 and the unit structure base side length C, as shown in the figure. Figure 1 As shown, when the linear polarized light at the working wavelength is incident on the nanobrick unit structure, two sets of size parameters are obtained, with the transmittance along the short axis being high and equal, and the reflectivity along the long axis being the highest and equal, as shown in FIG. Figure 2 As shown, the two groups of nanobricks have different reflective spectra, so they can show different colors under natural light.

[0050] 2. The optimized nanobrick unit structure can function as a polarizer and can be used as a Jones matrix. To express it, when the incident light is polarized light with the electric field direction along the x-axis at an angle of α1, the outgoing light after passing through the nanobrick unit structure and the analyzer can be expressed as:

[0051]

[0052] Among them, A in Represents the amplitude of the incident light (0 in ≤1). The intensity of the outgoing light is: ​

[0053]

[0054] Three polarizer and analyzer rotation angle combinations are set: (π / 2, 0), (5π / 8, -π / 8) and (-π / 8, 3π / 8). The metasurface will show different intensities when working in this channel. The optical path diagram is as follows Figure 3 shown.

[0055] When the polarizer angle is π / 2 and the analyzer angle is 0, the intensity expression of the outgoing light is: I r1 =I0sin 2 2θ.

[0056] When the polarizer angle is 5π / 8 and the analyzer angle is -π / 8, the intensity expression of the outgoing light is:

[0057] When the polarizer rotation angle is -π / 8 and the analyzer rotation angle is 3π / 8, the intensity expression of the outgoing light is:

[0058] When the nanobrick rotation angle is 1π / 16, I r1 , I r2 , I r3 The grayscale values ​​are approximately equivalent to 0, 0, and 1 respectively.

[0059] When the nanobrick rotation angle is 3π / 16, I r1 , I r2 , I r3 The grayscale values ​​are approximately equivalent to 1, 0, and 1 respectively.

[0060] When the rotation angle of the nanobrick is 5π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 0, 0 respectively.

[0061] When the nanobrick rotation angle is 7π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 0, 0.

[0062] When the nanobrick rotation angle is 9π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 1, and 1 respectively.

[0063] When the nanobrick rotation angle is 11π / 16, I r1 , I r2 , I r3The grayscales are approximately equivalent to 1, 1, 1.

[0064] When the nanobrick rotation angle is 13π / 16, I r1 , I r2 , I r3 The grayscale values ​​are approximately equivalent to 1, 1, and 0 respectively.

[0065] When the nanobrick rotation angle is 15π / 16, I r1 , I r2 , I r3 The grayscale values ​​are approximately equivalent to 0, 1, and 0 respectively.

[0066] 3. Select QR code #1, QR code #2, and QR code #3. That is, based on the intensity correspondence in step 2, the angle of the nanobrick is reasonably selected, and three different QR codes are observed under the three incident conditions mentioned above.

[0067] 4. Select QR code #4. Pixels with an intensity of 1 are selected as nanobrick a, and pixels with an intensity of 0 are selected as nanobrick b. Since the two nanobricks have different reflective spectra, they will appear in different colors under natural light, thus observing QR code #4. Its light path diagram is as follows: Figure 4 shown.

[0068] The simulated QR code display effect is shown in the figure below: Figure 5 、 6 , 7, and 8.

Claims

1. A design method for a metasurface for realizing a four-channel two-dimensional code, characterized in that: The following steps are involved: S1: Optimizing the nanobrick unit structure with polarizer characteristics: determining the working wavelength λ, optimizing the size parameters of two nanobrick unit structures of different sizes, namely nanobrick a and nanobrick b, through electromagnetic simulation software, optimizing the nanobrick unit structure with polarizer characteristics, so that when linear polarized light at the same working wavelength is incident on the nanobrick unit structure, for the two bricks of different sizes, the components polarized along the long axis are all reflected, and the components polarized along the short axis are all transmitted; the nanobrick unit structure is composed of a substrate and nanobricks etched on the substrate; the size parameters of the nanobrick unit structure include the length L, width W, height H, and center interval C of the nanobrick; S2: Select four QR code patterns, namely QR code #1, QR code #2, QR code #3, and QR code #4; divide the information to be encrypted into four parts and assign them to the four QR codes respectively; design the nanobrick corner arrangement: According to step S1, two different sizes of nanobricks a and nanobricks b are equivalent to a polarizer at a working wavelength of λ; set the working wavelength to λ, and according to the output light intensity formula after the incident line polarization passes through the nanounit structure and the analyzer in sequence: Set three rotation angle combinations of polarizers and analyzers; When the polarizer is rotated at π / 2 and the analyzer is rotated at 0, the intensity of the outgoing light is expressed as: I r1 =I0sin 2 2θ; When the polarizer angle is 5π / 8 and the analyzer angle is -π / 8, the intensity expression of the outgoing light is: When the polarizer rotation angle is -π / 8 and the analyzer rotation angle is 3π / 8, the intensity expression of the outgoing light is: When the nanobrick rotation angle is 1π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 0, and 1 respectively; When the nanobrick rotation angle is 3π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 0, and 1 respectively; When the rotation angle of the nanobrick is 5π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 0, 0; When the nanobrick rotation angle is 7π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 0, 0; When the nanobrick rotation angle is 9π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 1, and 1 respectively; When the nanobrick rotation angle is 11π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 1, 1; When the nanobrick rotation angle is 13π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 1, 1, and 0 respectively; When the nanobrick rotation angle is 15π / 16, I r1 , I r2 , I r3 The grayscales are approximately equivalent to 0, 1, and 0 respectively; Thus, for each nanobrick, there are 8 corners to choose from to satisfy all grayscale combinations of the three 2D codes 2D code #1, 2D code #2, and 3 (8 = 2 3 ), that is, by reasonably selecting the rotation angle of the nanobrick, three different two-dimensional codes can be observed under the above three incident conditions; S3: Design the size arrangement of nanobricks: Since the two different sizes of nanobricks have different spectral responses, they will show different colors when natural light is incident. Select QR code #4 and determine the size arrangement of nanobricks based on the grayscale distribution of QR code #4. When the grayscale of the pixel of QR code #4 is 1, nanobrick a is selected, and when the grayscale of the pixel of QR code #4 is 0, nanobrick b is selected.

2. The method for designing a metasurface for realizing a four-channel two-dimensional code according to claim 1, characterized in that: In step S1, the working wavelength is selected as 533 nm; when the working wavelength is selected as 533 nm, the length L of the nanobrick a a is 220nm, and the length L of the nanobrick b is b The unit structures have a center spacing C of 300 nm and a width W of 60 nm.

3. A metasurface for realizing a four-channel two-dimensional code, characterized in that: The super surface is designed by the method according to claim 1 or claim 2, the base material is alumina, and the nano brick material is silicon.

4. The metasurface for realizing four-channel two-dimensional code according to claim 3, characterized in that: (1) The nano brick material is S i , the base material is Al2O3.

5. The metasurface for realizing four-channel two-dimensional code according to claim 3 or 4, characterized in that: The two-dimensional code is composed of two nanobricks of different sizes, namely nanobrick a and nanobrick b; the two nanobricks, namely nanobrick a and nanobrick b, are equivalent to polarizers and have different spectral responses, and present different colors when white light is incident; When linear polarized light is incident, three different QR codes #1, #2 and #3 can be realized by changing the rotation angle combination of the analyzer; When white non-polarized light is incident, a QR code #4 can be displayed.

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