Metasurface device for realizing multiplexing of double-channel image holographic nano printing image and construction method of metasurface device

Abstract

The invention discloses a metasurface device for realizing multiplexing of a dual-channel image holographic nano printing image and a construction method of the metasurface device. Zero-order diffraction emergent light and first-order diffraction emergent light are respectively selected as coding channels, a binary gray image is coded into a zero-order diffraction channel, and a continuous gray image is coded into a first-order diffraction channel; according to different diffraction order characteristics of Bessel expansion, a continuous grayscale image is firstly encoded into initial hologram phase distribution, and then the phase of each pixel point on a hologram is adjusted by combining a one-to-two mapping relation and the grayscale value of each pixel point on a binary grayscale image, so that final phase distribution is obtained. The metasurface device provided by the invention is compact in structure, has the advantages of miniaturization and light weight, can directly observe holographic nano printing images without the assistance of a polarizer and an analyzer, and is expected to promote the practical application of the nano printing images in the fields of information multiplexing, information encryption, optical anti-counterfeiting and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of micro-nano optics, and more specifically, relates to a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing and a construction method thereof. Background Art

[0002] Regarding the current polarization multiplexing of nano-printing images, there are methods of optimizing the sub-wavelength unit structure into a half-wave plate, combining a polarizer and an analyzer, and using the Jones matrix method to adjust the intensity distribution of the outgoing light by rotating the metasurface for nano-printing image switching, and optimizing the sub-wavelength unit structure into a polarizer, combining a polarizer and an analyzer, and using the Jones matrix method to adjust the intensity distribution of the outgoing light by rotating the analyzer for nano-printing image switching. These schemes are all limited by the complex observation optical path, that is, the combination of the polarizer and the analyzer, making it difficult to simplify the observation of nano-printing images. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention proposes a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing and a construction method thereof based on the Bessel expansion characteristics of hologram phase. By using the diffraction orders of the outgoing light after Bessel expansion, the feasibility of realizing two image holographic nano-printing images is theoretically proved, and a continuous grayscale image holographic nano-printing image and a binary grayscale image holographic nano-printing image are encoded into a single hologram phase, and then simulation verification is carried out. This method simplifies the observation conditions of nano-printing images and promotes the application of nano-printing images in the fields of optical anti-counterfeiting, information encryption, image display, etc.

[0004] According to one aspect of the specification of the present invention, a construction method of a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing is provided, including: Deriving an initial hologram phase distribution according to the target continuous grayscale image and the diffraction order multiplexing principle, and then adjusting the phase according to the one-to-two mapping relationship and the gray value of the corresponding pixel points of the binary grayscale image to obtain the final hologram phase distribution; Designing a unit structure for constructing the metasurface device, the unit structure including a substrate and nano-bricks on the working surface of the substrate; establishing an xoy coordinate system with the directions of two sides parallel to the working surface of the substrate as the x-axis and the y-axis; the nano-bricks are rectangular structures, the major axis and the minor axis of the nano-bricks are both parallel to the working surface of the substrate, and the rotation angle of the nano-bricks is the included angle between the major axis of the nano-bricks and the x-axis; Optimizing the designed unit structure through an electromagnetic simulation software to obtain a unit structure equivalent to a half-wave plate; According to the phase of each pixel on the hologram, arrange the unit structures with a rotation angle equal to half of the phase value to construct a metasurface device capable of realizing dual-channel image holographic nano-printing image multiplexing.

[0005] As a further technical solution, when an incident plane wave irradiates the metasurface device, the zero-order outgoing light forms a binary gray-scale image holographic nano-printing image on the surface of the metasurface device; the first-order outgoing light forms a continuous gray-scale image holographic nano-printing image on the surface of the metasurface device.

[0006] As a further technical solution, the transmittance of the long axis and the short axis of the unit structure is higher than 80% and the phase difference between the long axis and the short axis is close to , the phase added by the unit structure to the incident circularly polarized light is related to the rotation angle of the unit structure and is twice the rotation angle.

[0007] As a further technical solution, the intensity distributions of the outgoing lights of different diffraction orders are as follows: , wherein, represents the phase distribution of the hologram, represents the periodic phase, which divides the outgoing light into different diffraction orders, so as to encode different target gray-scale images on the outgoing lights of different diffraction orders, represents the Bessel function of the first kind of order m, , respectively represent the intensity distributions of the binary gray-scale image and the continuous gray-scale image.

[0008] As a further technical solution, when obtaining the final hologram phase distribution, it further includes: According to the mapping relationship in the outgoing light intensity distribution and the hologram phase formula, deduce the value corresponding to each pixel point of the continuous gray-scale image to obtain the initial phase distribution, and then adjust the phase according to the one-to-two mapping relationship and the gray-scale value of the corresponding pixel point of the binary gray-scale image to obtain the final hologram phase distribution; According to the relationship between the deduced final hologram phase distribution and the rotation angle of the unit structure and the phase modulation amount, determine the rotation angle of the nano-bricks in the unit structure corresponding to each pixel point, and then arrange the optimized designed unit structures to construct a metasurface device capable of realizing dual-channel image holographic nano-printing image multiplexing.

[0009] As a further technical solution, when optimizing the design of the unit structure, it further includes: Determine the height of the nano-bricks and the distance between the center points of adjacent nano-bricks according to the processing conditions; Use an electromagnetic simulation software to perform parametric scans on the major and minor axis dimensions of the nano-bricks at the working wavelength, and simulate the schematic diagrams of the transmittance of the major and minor axes and the phase difference between the major and minor axes for nano-bricks of different sizes; Select the unit structure with the highest circular polarization conversion efficiency in the working band according to the scan results.

[0010] As a further technical solution, the transmittance of the major and minor axes of the selected unit structure is higher than 80% and the phase difference between the major and minor axes is close to .

[0011] According to one aspect of the specification of the present invention, there is provided a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing, which is obtained by using the method for constructing a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing.

[0012] One or more technical solutions provided in the present invention have at least the following technical effects or advantages: In the present invention, the zero-order diffracted light and the first-order diffracted light are respectively selected as the encoding channels, and the binary gray-scale image is encoded into the zero-order diffraction channel and the continuous gray-scale image is encoded into the first-order diffraction channel; according to the characteristics of different diffraction orders of the Bessel expansion, the continuous gray-scale image is first encoded into the initial hologram phase distribution, and then combined with the one-to-two mapping relationship and the gray-scale value of each pixel point on the binary gray-scale image, the phase of each pixel point on the hologram is adjusted to obtain the final phase distribution, overcoming the limitation that the current nano-printing image requires complex optical path assistance for observation.

[0013] The metasurface device provided by the present invention has a compact structure, and at the same time has the advantages of miniaturization and light weight. It can directly observe the image holographic nano-printing image without the assistance of a polarizer and an analyzer, and is expected to promote the practical application of nano-printing images in the fields of information multiplexing, information encryption, optical anti-counterfeiting, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings used in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is a conceptual diagram of a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing provided by an embodiment of the present invention.

[0016] Figure 2 It is a schematic diagram of the design principle of a metasurface device for realizing dual-channel image holographic nano-printing image multiplexing provided by an embodiment of the present invention.

[0017] Figure 3 This is the design flow chart of the metasurface device provided by the embodiment of the present invention.

[0018] Figure 4 (a)-(d) are the simulation result diagrams of the dual-channel image holographic nanoprinting images provided by the embodiment of the present invention. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. In addition, the technical features in each embodiment or individual embodiment provided by the present invention can be combined with each other arbitrarily to form a new technical solution. This combination is not restricted by the order of steps and / or the structural composition mode, but must be based on what can be achieved by those of ordinary skill in the art. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention. Embodiment 1

[0020] Embodiment 1 provides a method for constructing a metasurface device for realizing dual-channel image holographic nanoprinting image multiplexing, including the following steps: Step 1: Derive the initial hologram phase distribution according to the target continuous grayscale image and the diffraction order multiplexing principle, and then adjust the phase according to the one-to-two mapping relationship and the grayscale values of the corresponding pixel points of the binary grayscale image to obtain the final hologram phase distribution. When an incident plane wave irradiates the hologram, the zero-order outgoing light can decode a binary grayscale image holographic nanoprinting image on the surface of the metasurface device, and the first-order outgoing light can decode a continuous grayscale image holographic nanoprinting image on the surface of the metasurface device.

[0021] Step 2: Design a unit structure for constructing the metasurface device. The unit structure includes a substrate and nanobricks on the working surface of the substrate; establish an xoy coordinate system with the directions of two sides parallel to the working surface of the substrate as the x-axis and the y-axis; the nanobricks are rectangular structures, the major axis and the minor axis of the nanobricks are parallel to the working surface of the substrate, and the rotation angle of the nanobricks is the included angle between the major axis of the nanobricks and the x-axis.

[0022] Step 3: Optimize the designed unit structure through electromagnetic simulation software to obtain a unit structure equivalent to a half-wave plate, where the transmittances of the major axis and minor axis of the unit structure are higher than 80% and the phase difference between the major axis and the minor axis is close to , and the phase added by the unit structure to the incident circularly polarized light is related to the rotation angle of the unit structure and is twice the rotation angle.

[0023] Step 4: Arrange the unit structures with rotation angles equal to half of the phase values according to the phase of each pixel point on the hologram to construct a metasurface device capable of realizing dual-channel image holographic nanoprinting image multiplexing: When an incident plane wave irradiates the metasurface device, the zero-order outgoing light forms a binary gray-scale image holographic nanoprinting image on the surface of the metasurface device; the first-order outgoing light forms a continuous gray-scale image holographic nanoprinting image on the surface of the metasurface device.

[0024] In the said Step 1, the intensity distributions of the outgoing lights of different diffraction orders are as follows: , wherein, represents the phase distribution of the hologram, represents the periodic phase, which divides the outgoing light into different diffraction orders, so as to encode different target gray-scale images on the outgoing lights of different diffraction orders, represents the first-kind Bessel function of order m, , respectively represent the intensity distributions of the binary gray-scale image and the continuous gray-scale image.

[0025] When obtaining the final hologram phase distribution, first, according to the mapping relationship between the outgoing light intensity distribution and A in the hologram phase formula, deduce the value of A corresponding to each pixel point of the continuous gray-scale image, so as to obtain the initial phase distribution , and then perform phase adjustment according to the one-to-two mapping relationship and the gray-scale value of the corresponding pixel point of the binary gray-scale image to obtain the final hologram phase distribution . Determine the rotation angle of the nano-bricks in the unit structure corresponding to each pixel point according to the deduced final hologram phase distribution and the relationship between the rotation angle of the unit structure and the phase control amount, and then arrange the optimized designed unit structures to construct a metasurface device capable of realizing dual-channel image holographic nanoprinting image multiplexing.

[0026] In the said Step 3, when optimizing the design of the unit structure, first determine the height of the nano-bricks and the distance between the centers of adjacent nano-bricks according to the processing conditions, and then use electromagnetic simulation software to perform parametric scanning on the major axis and minor axis dimensions of the nano-bricks at the working wavelength, and simulate the schematic diagrams of the transmittances of the major axis and minor axis and the schematic diagram of the phase difference between the major axis and the minor axis under nano-bricks of different sizes; finally, select the unit structure with the highest circular polarization conversion efficiency in the working band according to the scanning results.

[0027] The transmittances of the major axis and minor axis of the selected unit structure are higher than 80%, and the phase difference between the major axis and the minor axis is close to .

[0028] When parameterizing the scanning unit structure, the major axis of the nanobrick is parallel to the x-axis, and periodic boundary conditions are used. Example 2

[0029] Example 2 provides a metasurface device for realizing dual-channel image holographic nanoprinting image multiplexing, which is obtained by using the construction method of a metasurface device for realizing dual-channel image holographic nanoprinting image multiplexing provided in Example 1.

[0030] The present invention will be further described below.

[0031] The metasurface device includes a substrate and nanobricks arranged periodically above the substrate, wherein both the substrate and the nanobricks are sub-wavelength sized. The substrate material is fused silica, and the nanobrick material is amorphous silicon. The substrate is divided into square units with the same size, and a nanobrick is placed above the center of each unit. The side length of the square unit is equal to the distance between the centers of adjacent nanobricks. The designed working wavelength band of the metasurface device is green light (wavelength 533 nm). The following will be described by taking the working wavelength of 533 nm as an example.

[0032] Each nanobrick corresponds to an imaging pixel. Nanobricks with the same size but different rotation angles add different phase delay amounts to the incident light with a wavelength of 533 nm. By reasonably arranging the rotation angle distribution of nanobricks with the same size, two independent image holographic nanoprinting images can be generated under the irradiation of the same incident light without the assistance of any polarizer and analyzer.

[0033] Principle of different rotation angles of nanobricks adding different phase delay amounts to 533 nm incident circularly polarized light: When the incident circularly polarized light irradiates on nanobricks with the same size but different rotation angles, by using the Jones matrix of the incident circularly polarized light, the Jones matrix of the nanobrick, and the rotation matrix in combination with the Jones matrix method, it can be deduced that the outgoing light contains circularly polarized light with the same rotation direction and circularly polarized light with the opposite rotation direction. Among them, the circularly polarized light with the same rotation direction has no additional phase, while the circularly polarized light with the opposite rotation direction has an additional phase, and the additional phase is twice the rotation angle of the nanobrick. Therefore, only the rotation angle of the nanobrick needs to be determined according to the requirement of the phase delay amount.

[0034] When designing the size of the nanobricks, the long axis of the nanobricks is parallel to the x-axis. Through parametric scanning, the phases added by nanobricks of different sizes to polarized light in the long-axis direction and short-axis direction are obtained. The phase difference between the long and short axes of nanobricks of different sizes under the illumination of green light with a wavelength of 533 nm is acquired. Meanwhile, through parametric scanning, the transmittance of nanobricks of different sizes to green light with a wavelength of 533 nm is obtained. Finally, nanobricks with a phase difference between the long and short axes close to and a transmittance of both the long and short axes of the nanobricks exceeding 80% are selected.

[0035] When obtaining the phase distribution of the hologram, first, according to the mapping relationship between the intensity distribution of the outgoing light and A in the hologram phase formula, the value of A corresponding to each pixel point of the continuous grayscale image is deduced, thereby obtaining the initial phase distribution Then, based on the one-to-two mapping relationship and the gray values of the corresponding pixel points of the binarized grayscale image, the phase is adjusted to obtain the final hologram phase distribution Thereby, a continuous grayscale image and a binarized grayscale image are encoded into the hologram phase.

[0036] Each nanobrick in the metasurface corresponds to a pixel. According to the hologram phase distribution obtained from the above derivation and the relationship between the rotation angle of the unit structure and the phase modulation amount, the rotation angle distribution of the nanobricks is determined . When the incident light with a wavelength of 533 nm irradiates the metasurface device, the intensity distributions of the zero-order diffracted outgoing light and the first-order diffracted outgoing light are:

[0037] Among them, represents the phase distribution of the hologram, represents the periodic phase, which divides the outgoing light into different diffraction orders, thereby encoding different target grayscale images on the outgoing light of different diffraction orders, represents the first-kind Bessel function of order m, 、 represent the intensity distributions of the binarized grayscale image and the continuous grayscale image respectively.

[0038] Without the assistance of any polarizer and analyzer, when the light with a wavelength of 533 nm irradiates the metasurface device, a binarized grayscale image can be generated in the zero-order diffraction channel and a continuous grayscale image can be generated in the first-order diffraction channel.

[0039] A method for constructing a metasurface device for realizing dual-channel independent image holographic nanoprinting image multiplexing includes the following steps: (1) Determine the materials and basic structures of the substrate and the nanobricks. The two mutually perpendicular sides of the substrate are the x-axis and the y-axis. Determine the height H of the nanobricks and the side length of the square substrate unit according to the processing conditions.

[0040] (2)Optimized unit structure dimensions: Under the incidence of x - polarized light and y - polarized light, parametrically scan the long and short axis dimensions of the nanobricks, simulate the transmittance of the long and short axes of nanobricks with different dimensions and the phase difference between the long axis and the short axis of nanobricks with different dimensions, and select the nanobrick structure whose transmittance of both the long and short axes exceeds 80% and the phase difference between the long axis and the short axis is close to π.

[0041] (3)Determine the hologram phase distribution according to the mapping relationship between the intensity distribution of the target binary gray - scale image, the intensity distribution of the target continuous gray - scale image and the Bessel expansion characteristics of the zero - order diffracted outgoing light and the first - order diffracted outgoing light, and then determine the rotation angles of each nanobrick on the metasurface device according to the relationship between the hologram phase distribution and the rotation angle and phase modulation amount of the unit structure.

[0042] The following further explains the present invention with reference to the drawings.

[0043] Figure 1 It is a conceptual diagram of a metasurface device for realizing dual - channel independent - image holographic nano - printing image multiplexing. The metasurface device includes a fused - silica substrate and amorphous silicon nanobricks of the same size but different rotation angles. When incident light irradiates the metasurface device, a binary gray - scale image will be generated in the zero - order diffraction channel and a continuous gray - scale image will be generated in the first - order diffraction channel.

[0044] The design principle of the metasurface device for realizing dual - channel independent - image holographic nano - printing image multiplexing is as Figure 2 shown. When the phase distribution of the metasurface device is , when incident light irradiates the metasurface, the outgoing light can be divided into diffracted lights of different orders. Among them, the light - field intensity distribution of the zero - order diffracted outgoing light is:

[0045] The light - field intensity distribution of the first - order diffracted outgoing light is:

[0046] According to the mapping relationship between the intensity of the zero - order diffracted outgoing light and A in the hologram phase, it can be known that one intensity value of the continuous gray - scale image can correspond to two A values. In the mapping relationship between the intensity of the first - order diffracted outgoing light and A in the hologram phase, the two A values can respectively correspond to two states of "black" and "white". Then, combined with the gray - scale values of the binary gray - scale image, select the A values that meet the design requirements, so as to realize the simultaneous encoding of a binary gray - scale image and a continuous gray - scale image by one metasurface device.

[0047] Figure 3It is the design flow chart of the metasurface device. First, based on the intensity distribution of the continuous grayscale image and the mapping relationship between the intensity of the first-order diffracted light and A in the hologram phase, the initial phase distribution is deduced. Then, according to the one-to-two mapping relationship and the gray values of the corresponding pixels of the binarized grayscale image, the phase is adjusted to obtain the final hologram phase distribution. Furthermore, the simultaneous encoding of two grayscale images is realized.

[0048] In this embodiment, the number of pixels of the metasurface device is 1000*1000, which is the same as the number of pixels of the target image. The working wavelength is 533 nm. The period CS of the selected nanobrick is 300 nm, and the height H is 180 nm. Using the CST electromagnetic simulation software, the long and short axis dimensions of the nanobrick are parametrically scanned at the working wavelength, and the periodic boundary condition is used. The short axis scanning range is 60 nm - 140 nm, the long axis scanning range is 200 nm - 280 nm, and the step size is 2 nm. The transmission rates of the long and short axes and the phase difference between the long axis and the short axis of the nanobrick with different sizes under the incidence of x-polarized light and y-polarized light are obtained by simulation. According to the target that the transmission rates of the long and short axes are greater than 80% and the phase difference between the long axis and the short axis is close to π, the nanobrick size that meets the design requirements is selected: the length L is 240 nm, and the width W is 84 nm.

[0049] According to the phase distribution of the metasurface device and the relationship between the rotation angle of the unit structure and the phase modulation amount, the rotation angles of each nanobrick on the metasurface device are determined. Then, using a plane wave with a wavelength of 533 nm to irradiate this metasurface device, a binarized grayscale image highly consistent with the target image can be observed in the zero-order diffraction channel, as shown in Figure 4 Figures (a) and (b), and a continuous grayscale image exactly the same as the target image can be observed in the first-order diffraction channel, as shown in Figure 4 Figures (c) and (d).

[0050] The metasurface device and the construction method for realizing dual-channel independent image holographic nano-printing image multiplexing provided by the embodiment of the present invention at least include the following technical effects: (1) In the present invention, a binarized grayscale image is generated in the zero-order diffraction channel of the metasurface device and a continuous grayscale image is generated in the first-order diffraction channel of the metasurface device. By exploiting the Bessel expansion characteristics of the hologram phase, image holographic nano-printing images with diffractive order multiplexing can be realized, and the switching of nano-printing images can be achieved only by changing the observation angle, overcoming the limitations of the complex observation conditions and cumbersome switching conditions of traditional nano-printing images, and greatly simplifying the observation conditions and switching conditions of nano-printing images.

[0051] (2)The metasurface device provided by the present invention has a compact structure, and at the same time has the advantages of miniaturization and light weight. It can directly observe holographic nano-printed images without the assistance of a polarizer and an analyzer, and is expected to promote the practical application of nano-printed images in the fields of information multiplexing, information encryption, optical anti-counterfeiting, etc.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images, characterized in that, Including: Derive the initial hologram phase distribution based on the target continuous grayscale image and the diffraction order multiplexing principle, and then adjust the phase according to the one-to-two mapping relationship and the grayscale values of the corresponding pixels of the binary grayscale image to obtain the final hologram phase distribution; Design a unit structure for constructing a metasurface device. The unit structure includes a substrate and nanobricks on the working surface of the substrate. Establish an xoy coordinate system with the directions of two sides parallel to the working surface of the substrate as the x-axis and the y-axis. The nanobricks are rectangular structures, the major axis and minor axis of the nanobricks are both parallel to the working surface of the substrate, and the rotation angle of the nanobricks is the angle between the major axis of the nanobricks and the x-axis; Through electromagnetic simulation software, optimize the designed unit structure to obtain a unit structure equivalent to a half-wave plate; According to the phase of each pixel point on the hologram, arrange the unit structures with the rotation angle equal to half of the phase value to construct a metasurface device capable of realizing dual-channel image holographic nanoprinting image multiplexing.

2. The method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images according to claim 1, wherein When an incident plane wave irradiates the metasurface device, the zero-order outgoing light forms a binary grayscale image holographic nanoprinting image on the surface of the metasurface device; the first-order outgoing light forms a continuous grayscale image holographic nanoprinting image on the surface of the metasurface device.

3. The method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images according to claim 1, wherein, The transmittances of the major axis and the minor axis of the unit structure are higher than 80%, and the phase difference between the major axis and the minor axis is close to , the phase added to the incident circularly polarized light by the unit structure is related to the rotation angle of the unit structure and is twice the rotation angle.

4. The method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images according to claim 1, wherein The intensity distributions of the outgoing light of different diffraction orders are as follows: ， Among them, represents the phase distribution of the hologram, represents the periodic phase, which divides the outgoing light into different diffraction orders, thereby encoding different target grayscale images on the outgoing light of different diffraction orders, represents the Bessel function of the first kind of order m, and represent the intensity distributions of the binary grayscale image and the continuous grayscale image respectively.

5. The method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images according to claim 4, wherein When obtaining the final hologram phase distribution, it also includes: According to the mapping relationship between the outgoing light intensity distribution and the hologram phase formula, derive the value corresponding to each pixel point of the continuous grayscale image to obtain the initial phase distribution, and then adjust the phase according to the one-to-two mapping relationship and the grayscale values of the corresponding pixels of the binary grayscale image to obtain the final hologram phase distribution; According to the relationship between the derived final hologram phase distribution and the rotation angle of the unit structure and the phase control amount, determine the rotation angle of the nanobricks in the unit structure corresponding to each pixel point, and then arrange the optimized designed unit structures to construct a metasurface device capable of realizing dual-channel image holographic nanoprinting image multiplexing.

6. The method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images according to claim 1, characterized in that, When optimizing the designed unit structure, it also includes: Determine the height of the nanobricks and the distance between the center points of adjacent nanobricks according to the processing conditions; Use electromagnetic simulation software to perform parametric scanning on the major axis and minor axis dimensions of the nanobricks at the working wavelength, and simulate the schematic diagrams of the transmittance of the major axis and minor axis and the phase difference between the major axis and minor axis under different sizes of nanobricks; Select the unit structure with the highest circular polarization conversion efficiency in the working band according to the scanning results.

7. The method for constructing a metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images according to claim 6, wherein The transmittance of the major axis and minor axis of the selected unit structure is higher than 80% and the phase difference between the major axis and minor axis is close to π.

8. A metasurface device for realizing dual-channel image multiplexing of holographic nano-printed images, characterized in that, Obtained by using the method for constructing a metasurface device for realizing dual-channel image holographic nanoprinting image multiplexing according to any one of claims 1-7.

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