CN114167706B - Rotary multiplexing method based on cascade metasurface holography - Google Patents

Rotary multiplexing method based on cascade metasurface holography Download PDF

Info

Publication number
CN114167706B
CN114167706B CN202111475245.6A CN202111475245A CN114167706B CN 114167706 B CN114167706 B CN 114167706B CN 202111475245 A CN202111475245 A CN 202111475245A CN 114167706 B CN114167706 B CN 114167706B
Authority
CN
China
Prior art keywords
metasurface
holograms
cascaded
phase distribution
cascade
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202111475245.6A
Other languages
Chinese (zh)
Other versions
CN114167706A (en
Inventor
黄玲玲
魏群烁
赵睿哲
李晓炜
王涌天
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beijing Institute of Technology BIT
Original Assignee
Beijing Institute of Technology BIT
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beijing Institute of Technology BIT filed Critical Beijing Institute of Technology BIT
Priority to CN202111475245.6A priority Critical patent/CN114167706B/en
Publication of CN114167706A publication Critical patent/CN114167706A/en
Application granted granted Critical
Publication of CN114167706B publication Critical patent/CN114167706B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/0005—Adaptation of holography to specific applications
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/0005—Adaptation of holography to specific applications
    • G03H1/0011—Adaptation of holography to specific applications for security or authentication
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/08—Synthesising holograms, i.e. holograms synthesized from objects or objects from holograms
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/22—Processes or apparatus for obtaining an optical image from holograms
    • G03H1/2249—Holobject properties
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/0005—Adaptation of holography to specific applications
    • G03H1/0011—Adaptation of holography to specific applications for security or authentication
    • G03H2001/0016—Covert holograms or holobjects requiring additional knowledge to be perceived, e.g. holobject reconstructed only under IR illumination

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Computer Hardware Design (AREA)
  • Evolutionary Computation (AREA)
  • Geometry (AREA)
  • General Engineering & Computer Science (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)
  • Holo Graphy (AREA)

Abstract

The invention relates to a rotary multiplexing method based on cascade metasurface holography, and belongs to the technical field of micro-nano optics, holographic display and channel multiplexing application. The method uses an iterative gradient descent optimization algorithm to obtain the phase distribution of two metamaterial surface holograms participating in cascade connection, and the phase distribution is coded on different glass substrates by amorphous silicon nanorod antennas through the processes of deposition, photoetching, stripping, etching and the like. When the method is used for holographic encryption, only two single-layer metasurface holograms are stacked according to the correct relative in-plane rotation angle, the encrypted information can be read, and the method can be applied to the fields of information security, encryption, anti-counterfeiting and the like needing to hide confidential data. Furthermore, the holographic reconstruction of the rotationally multiplexed cascaded metasurface system can be encoded over discrete and equidistant angular spatial positions, which makes it potential for use as an optical protractor.

Description

Rotary multiplexing method based on cascade metasurface holography
Technical Field
The invention relates to a rotary multiplexing method based on cascade metasurface holography, and belongs to the technical field of micro-nano optics, holographic display and channel multiplexing application.
Background
The metasurface is usually composed of a subwavelength-sized metal or dielectric nano antenna array, can perform high-freedom modulation on the characteristics of amplitude, phase, polarization, wavelength, orbital angular momentum and the like of an optical field, and has wide application prospects in the fields of micro-nano holography, color printing, beam shaping, edge detection, optical encryption, anti-counterfeiting and the like. Information capacity is a very important attribute for metasurfaces. As a carrier of information, a metasurface can store optical information densely at a subwavelength scale, and the higher its information capacity, the more information can be recorded. In order to increase the information capacity of the metasurfaces, a technique of expanding an additional channel for recording a more target image without increasing the number of pixels included in the metasurfaces is called a multiplexing technique. The current more common metasurface multiplexing technology comprises a synthesis spectrum method, spatial multiplexing, position multiplexing, polarization multiplexing, wavelength multiplexing, angle multiplexing and the like, the methods are compiled by utilizing a holographic algorithm, and new degrees of freedom are introduced by different ways such as arrangement modes, structural characteristics or wavefront modulation mechanisms of metasoma atoms, so that the information capacity of metasurfaces is greatly increased.
However, for a single-layer metasurface, the number of degrees of freedom is limited due to its mirror symmetry with respect to its own structural plane. On the other hand, a single-layer metasurface can only provide an additional information channel by designing and arranging the metasons on the metasurface, and cannot achieve physical resolution of information. In recent years, multilayer metasurfaces and cascade metasurfaces have been rapidly developed and have realized many unprecedented functions, wherein the integrated multilayer metasurfaces can be used to realize multispectral achromatic superlenses, image differentiation, asymmetric transmission with phase modulation function, differential wavefront modulation related to the propagation direction, micro-nano holography combined with color printing, and the like. And for the cascade metasurface which can be replaced, translated or rotated, the component assembly can be used for processing light propagation tracks, constructing a focal length-adjustable Morlet super lens, realizing dynamic wavefront modulation and the like.
In addition, in order to promote the practical application of the cascaded metasurfaces in the fields of encryption anti-counterfeiting, information security and the like, the cascaded metasurface holography is beginning to be valued by researchers. However, the existing cascaded metasurface information capacity is still relatively small, the versatility is relatively poor, and the practical application is limited.
Disclosure of Invention
The invention aims to solve the problems that the existing cascade metasurface has smaller information capacity and poorer versatility. The invention provides a rotary multiplexing method based on cascade metasurface holography; the method uses the relative in-plane rotation angle between two metasurface holograms as a new design freedom degree, and takes a plurality of cascade metasurfaces with different relative in-plane rotation angles as completely different optical systems when each metasurface hologram can reproduce a target image of the metasurface hologram, and a plurality of different holographic reproduction images are coded on the cascade metasurface holograms; i.e., a plurality of different holographic images reconstructed based on the cascaded metasurfaces, can be switched by rotating one metasurface hologram in the cascaded metasurface system about the normal of its own geometric center. The rotation multiplexing method based on the cascade metasurface holography can encode a large amount of information by means of the rotation angle in the relative plane, and endows the cascade metasurface with larger information capacity and stronger versatility.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a rotary multiplexing method based on cascade metasurface holography, which comprises the following steps:
step one, the phase distributions of two metasurface holograms A and B constituting the rotating multiplexing cascade metasurface system are efficiently and directly obtained by using an iterative gradient descent optimization algorithm. The two metasurface holograms a and B each correspond to a reproduction image independent of each other, and when the two metasurface holograms are stacked at a preset distance, a plurality of brand new reproduction images can be reproduced according to different relative in-plane rotation angles.
The method for realizing the phase distribution of the two metasurface holograms A and B forming the rotary multiplexing cascade metasurface system by using the iterative gradient descent optimization algorithm comprises the following steps:
step one, calculating a corresponding reproduction image C before the metasurface hologram A is cascaded 1 To reproduce the image C 1 Comparing with the target image of A, and calculating the mean square error E 1 ；
Step two, calculating a corresponding reproduction image C before the metasurface hologram B is cascaded 2 To reproduce the image C 2 Comparing with the target image of B, and calculating the mean square error E 2 ；
Step three, when the metasurface hologram A and the metasurface hologram B are cascaded, the metasurface hologram B rotates in situ around the normal of the geometric center thereof to obtain N cascaded metasurface systems corresponding to N different relative in-plane rotation anglesN reproduction images C 3_1 ，C 3_2 ，…，C 3_N Respectively reproducing the images C 3_1 ，C 3_2 ，…，C 3_N Comparing with respective target image, and calculating mean square error E 3_1 ，E 3_2 ，…，E 3_N ；
Step four, calculating the mean square error E 1 、E 2 And E 3_1 ，E 3_2 ,…,E 3_N Adding together to obtain a total error;
step five, obtaining a gradient through the total error obtained in the step four: the gradient is the derivative of the total error to the phase distribution of the two metasurface holograms a and B;
step six, updating the phase distribution of the two metasurface holograms A and B based on an Adam gradient descent optimization algorithm according to the gradient obtained in the step five;
and step seven, repeating the step one to the step six, performing multiple iterations, continuously updating the phase distribution of the metasurface holograms in the iterative optimization process, ensuring that the gradient is converged to be locally optimal finally, and finding a group of metasurface holograms with the minimum total error.
Step two, the cascade metasurface is formed by arranging medium nano-antennas with higher reverse-rotation circular polarization transmissivity; encoding a spatial phase distribution of the metasurface hologram for which the total error is minimal using the dielectric nanoantenna: the dielectric nano-antennas are arranged into a spatial array, and the spatial phase distribution is modulated through different in-plane azimuth angles of the dielectric nano-antennas.
And (3) encoding the phase distribution of the rotating multiplexing cascade metasurface hologram obtained in the first step through the medium nano antenna.
The encoding is realized by modulating the phase by a geometric phase modulation principle, and the specific method comprises the following steps: and determining different in-plane azimuth angles of the dielectric nano-antennas at various positions in the metasurface according to the spatial phase distribution of the target light field by using the dielectric nano-antennas with higher reverse circular polarization transmissivity. Based on the phase control characteristic of the chiral selectivity of the geometric phase, when left/right-handed circularly polarized incident light is incident on the dielectric nano antenna with the azimuth angle theta, the mutually conjugated phase modulation with the size of +/-2 theta can be formed on the right/left-handed circularly polarized emergent light, wherein +/-or < - > is determined by the specific polarization state combination (left-handed/right-handed, right-handed/left-handed) of the incident light and the emergent light.
And step three, processing the all-dielectric metasurface holograms A and B formed by the dielectric nano antenna on different glass substrates by deposition, photoetching, stripping and etching methods. The holohedral metasurface holograms A and B can reconstruct independent reproduction images in a far field through a lens; meanwhile, when the full-medium metasurface holograms a and B are stacked at a preset distance to form a cascade metasurface system, N brand-new reconstructed images are generated under specific N relative internal rotation angles, so that rotation multiplexing based on the cascade metasurface holography is realized.
And the dielectric nano antenna in the step two is an amorphous silicon nano rod antenna.
The shape and the size of the amorphous silicon nanorod antenna are determined by a strict coupled wave analysis (RCWA) method or a time domain finite difference (FDTD) method.
Has the advantages that:
1. the rotary multiplexing method based on the cascade metasurface holography, disclosed by the invention, can endow a cascade metasurface system with extremely large information capacity, not only can two metasurface holograms forming the rotary multiplexing cascade metasurface system respectively correspond to a reproduction image which is independent from each other, but also can reproduce a plurality of brand-new reproduction images different from the reproduction images corresponding to the two single-layer metasurface holograms forming the rotary multiplexing cascade metasurface system according to different relative in-plane rotation angles when the two metasurface holograms are stacked at a preset distance.
2. The invention discloses a rotary multiplexing method based on cascade metasurface holography. Has great potential in the fields of encryption and anti-counterfeiting. The reproduced images of the holograms of the two single-layer metasurfaces are completely unrelated to the reproduced images corresponding to the cascaded metasurface systems before and after relative rotation, and no leakage or crosstalk exists between the reproduced images. Only when the relative rotational position as a multiplexing channel is known, and two single-layer metasurface holograms are stacked according to the correct relative in-plane rotational angle, the encrypted information can be read. By utilizing the characteristic, the all-medium metasurface can be applied to the fields of information security, encryption, anti-counterfeiting and the like needing to hide confidential data;
3. the rotating multiplexing method based on the cascade metasurface holography can utilize the rotating angle in the opposite plane as a new multiplexing dimension, regard the cascade metasurface systems with different rotating angles in the opposite plane as completely different optical systems, and encode different holographic reproduction images serving as encrypted information on the optical systems. In practical applications, the holographic reconstruction image of the rotating multiplexed cascaded metasurface system can be encoded at discrete and angularly equidistant spatial positions, making it potentially useful as an optical protractor.
4. The invention discloses a rotating multiplexing method based on cascade metasurface holography, which uses a gradient descent optimization algorithm based on an Adam optimization algorithm, and the algorithm can adjust the learning rate in the optimization process and ensure that the gradient is converged to local optimum.
Drawings
FIG. 1 is a flow chart of a rotary multiplexing method based on cascade metasurface holography disclosed by the invention;
FIG. 2 is a flow chart of a gradient descent optimization algorithm used in the rotational multiplexing method based on the cascaded metasurface holography disclosed by the invention;
FIG. 3 is a scanning electron microscope photograph of a sample of the rotating multiplexed cascading metasurfaces processed in example 1 and a schematic diagram of an experimental apparatus used to observe a reconstructed image of a hologram; FIG. (a) is a scanning electron microscope photograph of the processed rotating multiplexed cascading metasurface samples; FIG. (b) is a schematic view of the experimental apparatus;
fig. 4 is an experimental reproduction of the sample of the rotating multiplexed cascade metasurface processed in example 1; FIG. a is an experimental reproduction of each of two single-layer metasurface holograms; the graph (b) is four experimental reproduction images corresponding to the four cascade metasurface optical systems formed when two metasurface holograms are stacked together at relative rotation angles in planes of 0 °, 90 °, 180 ° and 270 °, respectively.
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example 1
The method is characterized in that rotary multiplexing is realized based on the cascade metasurface holography, a relative in-plane rotation angle is used as a new multiplexing dimension, a cascade metasurface system with relative in-plane rotation angles of 0 degree, 90 degrees, 180 degrees and 270 degrees is regarded as a completely different optical system, and different holographic reproduction images serving as encrypted information are encoded on the optical system.
As shown in fig. 1, the present embodiment includes the following steps:
the method comprises the following steps: the phase distributions of two metasurface holograms a and B constituting the rotating multiplexed cascaded metasurface system are obtained efficiently and directly using an iterative gradient descent optimization algorithm.
The flow chart of the iterative gradient descent optimization algorithm used is shown in fig. 2, and the specific steps are as follows:
1) calculating the corresponding reconstructed image C before the metasurface hologram A is concatenated 1 To reproduce the image C 1 Comparing with the target image (letter 'pi') of A, calculating the mean square error E 1 ；
2) Computing a corresponding reconstructed image C prior to cascading the metasurface holograms B 2 To reproduce the image C 2 Comparing with the target image (magnifying glass) of B, calculating the mean square error E 2 ；
3) When the metasurface hologram A and the metasurface hologram B are cascaded, the metasurface hologram B is rotated around the normal of the geometric center thereof to obtain 4 reproduction images C of 4 cascaded metasurface systems with the rotation angles of 0 degree, 90 degrees, 180 degrees and 270 degrees in the relative plane 3_1 ，C 3_2 ，C 3_3 ，C 3_4 Respectively reproducing images C 3_1 ，C 3_2 ，C 3_3 ，C 3_4 The mean square error E is calculated in comparison with the respective target images (symbols "+", "-", "×" and "÷") 3_1 ，E 3_2 ，E 3_3 ，E 3_4 ；
4) Mean square error E 1 、E 2 And E 3_1 ，E 3_2 ，E 3_3 ，E 3_4 Adding together to obtain a total error; the foregoing processes are all performed within the automated differential framework of modern machine learning libraries to track changes in gradients;
5) obtaining a gradient through the total error obtained in the step 4): the gradient is the derivative of the total error to the phase distribution of the two metasurface holograms A and B;
6) updating the phase distribution of the two metasurface holograms A and B based on an adam (adaptive motion) gradient descent optimization algorithm according to the gradient obtained in the step 5);
7) and (4) repeating the steps 1) to 6), carrying out multiple iterations, continuously updating the phase distribution of the metasurface holograms in the iterative optimization process, ensuring that the gradient is converged to be locally optimal finally, and finding a group of metasurface holograms with the minimum total error.
The above calculation process is a forward process calculated with an explicit formula, in which the propagation of a 100 micron spacer layer between two metasurfaces is simulated using the angular spectrum theory, and the holograms of two single-layer metasurfaces and the hologram reconstruction images corresponding to the four cascaded metasurface systems are calculated by FFT, i.e., fast fourier transform.
Step two: the medium nano-antenna forming the metamaterial surface hologram is designed by adopting a strict coupled wave analysis method or a time domain finite difference method.
A series of simulation simulations are carried out based on a strict coupled wave analysis method and a time domain finite difference method, amorphous silicon nanorod antennas are selected as basic composition units of the all-dielectric metasurface holograms, and the phase distribution of the metasurface holograms is coded by using a geometric phase modulation principle.
In the structural design process, the height of the amorphous silicon nanorod antenna is fixed to 600 nanometers, the period in the x and y directions is fixed to 500 nanometers, the working wavelength is set to 800 nanometers, and then the length and the width of the amorphous silicon nanorod antenna are scanned in the range from 70 nanometers to 300 nanometers in 5 nanometer steps under the condition. Due to the use of the geometrical phase modulation principle, the dimensions of the structure should be chosen to have a high anti-circular polarization transmission and a low co-circular polarization transmission at the operating wavelength. Considering the balance between the manufacturing precision and the structural performance, this example selects an amorphous silicon nanorod antenna with a length of 195 nm and a width of 130 nm, and its scanning electron micrograph is shown in fig. 3 (a).
Step three: two full-medium metasurface holograms formed by the medium nano antenna are processed on different glass substrates through the processes of deposition, photoetching, stripping, etching and the like, and are stacked at a preset distance to form the designed rotary multiplexing cascade metasurface system.
The specific implementation method comprises the following steps:
1) an amorphous silicon thin film of 600 nm thickness was prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD). Subsequently, a polymethyl methacrylate resist layer was spin-coated on the amorphous silicon thin film, and baked on a hot plate at 170 ℃ for 2 minutes to remove the solvent;
2) the desired structure was made by standard electron beam lithography followed by developing the sample in a 1:3 solution of MIBK: IPA and washing with IPA followed by coating of a 20 nm thick layer of chrome by electron beam evaporation;
3) the stripping process was completed in hot acetone;
4) the desired structure is converted from chromium to silicon using inductively coupled plasma reactive ion etching (ICP-RIE) and finally the residual chromium mask is removed using a standard wet etch process.
According to design, the size of the processed all-dielectric metasurface hologram samples a and B of the example is 496 × 496 microns, the pixel size is 62 × 62 pixels, the pixel size is 8 microns, each pixel is composed of a 16 × 16 amorphous silicon nanorod antenna array, and the grid period is 500 nanometers. Each amorphous silicon nanorod antenna has a length of 195 nm and a width of 130 nm. The larger pixel size was chosen to facilitate alignment of the metasurfaces of the cascade stack in the experiment.
This example was experimentally verified for the processed all-dielectric rotating multiplexed cascading metasurfaces using the experimental apparatus shown in fig. 3 (b). The sample processed by the embodiment realizes phase modulation by using a geometric phase modulation principle, so that a combination of a linear polarizer and a quarter-wave plate is required to be respectively arranged in front of and behind the sample to prepare and select a circular polarization state required by incident light and transmitted light, and the unique chiral selectivity of the geometric phase modulation principle is met. A microscope objective is placed behind the sample to magnify the metasurface and since the reconstructed holographic reconstruction is in k-space, a further lens is placed to view the fourier plane with a CCD camera.
The experimental results are shown in fig. 4, and it can be seen that the holohedral metasurface holograms a and B each correspond to a reproduced image independent of each other, i.e., letters "pi" and "magnifying glass"; and when two full-media metasurface holograms are stacked 100 microns apart, at relative in-plane rotation angles of 0 °, 90 °, 180 ° and 270 °, the corresponding reconstructed images of the cascaded metasurface system are respectively the symbols "+", "-", "×" and "÷ div".
In summary, the present embodiment provides a rotation multiplexing method based on the cascaded metasurface holography, which can use the rotation angle in the relative plane as a new multiplexing dimension, regard the cascaded metasurface systems with different rotation angles in the relative plane as completely different optical systems, encode different holographic reconstruction images serving as encrypted information thereon, and apply the method to the fields of encryption and anti-counterfeiting. In practice, the holographic reconstruction image of the rotating multiplexed cascaded metasurface system can be encoded at discrete and angularly equidistant spatial positions, which makes it potentially useful as an optical protractor.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (5)

1. The rotation multiplexing method based on the cascade metasurface holography is characterized by comprising the following steps of: the method comprises the following steps:
obtaining the phase distribution of two metasurface holograms A and B forming the rotating multiplexing cascade metasurface system by using an iterative gradient descent optimization algorithm; the two metasurface holograms A and B respectively correspond to a reproduction image which is independent of each other; when two metasurface holograms are stacked at a preset distance, a plurality of brand new reproduced images can be reproduced according to different relative in-plane rotation angles;
obtaining the phase distribution of two metasurface holograms A and B forming the rotating multiplexing cascade metasurface system by using an iterative gradient descent optimization algorithm, comprising the following steps:
step one, calculating a corresponding reproduction image C before cascading of the metamaterials surface holograms A 1 To reproduce the image C 1 Comparing with the target image of A, calculating the mean square error E 1 ；
Step two, calculating a corresponding reproduction image C before the metasurface hologram B is cascaded 2 To reproduce the image C 2 Comparing with the target image of B, and calculating the mean square error E 2 ；
Step three, when the metasurface hologram A and the metasurface hologram B are cascaded, the metasurface hologram B rotates in situ around the normal of the geometric center of the metasurface hologram B to obtain N reproduction images C of N cascaded metasurface systems corresponding to N different in-plane rotation angles 3_1 ，C 3_2 ，…，C 3_N Respectively reproducing the images C 3_1 ，C 3_2 ，…，C 3_N Comparing with respective target image, and calculating mean square error E 3_1 ，E 3_2 ，…，E 3_N ；
Step four, calculating the mean square error E 1 、E 2 And E 3_1 ，E 3_2 ,…,E 3_N Adding together to obtain a total error;
step five, obtaining a gradient through the total error obtained in the step four: the gradient is the derivative of the total error to the phase distribution of the two metasurface holograms a and B;
step six, updating the phase distribution of the two metasurface holograms A and B based on an Adam gradient descent optimization algorithm according to the gradient obtained in the step five;
and step seven, repeating the step one to the step six, performing multiple iterations, continuously updating the phase distribution of the metasurface holograms in the iterative optimization process, ensuring that the gradient is converged to be locally optimal finally, and finding out the phase distribution of a group of metasurface holograms with the minimum total error.
2. A cascaded metasurface for implementing the method of claim 1, wherein: the antenna is formed by arranging medium nano-antennas with high reverse circular polarization transmissivity; encoding the spatial phase distribution of the metasurface hologram with the smallest total error using the dielectric nano-antenna: the dielectric nano-antennas are arranged into a spatial array, and the spatial phase distribution is modulated through different in-plane azimuth angles of the dielectric nano-antennas.
3. The cascaded metasurface of claim 2, wherein: the dielectric nano antenna is an amorphous silicon nano rod antenna.
4. The cascaded metasurface of claim 3, wherein: the shape and the size of the amorphous silicon nanorod antenna are determined by a strict coupled wave analysis method or a time domain finite difference method.
5. A method of preparing the cascaded metasurface of claim 2, wherein: processing all-dielectric metasurface holograms A and B formed by the dielectric nano antenna on different glass substrates by deposition, photoetching, stripping and etching methods; the holohedral metasurface holograms A and B can reconstruct independent reproduction images in a far field through a lens; meanwhile, when the full-medium metasurface holograms a and B are stacked at a preset distance to form a cascaded metasurface system, N brand-new reconstructed images can be generated under N relative internal rotation angles, and rotation multiplexing based on the cascaded metasurface holography is realized.
CN202111475245.6A 2021-12-06 2021-12-06 Rotary multiplexing method based on cascade metasurface holography Active CN114167706B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111475245.6A CN114167706B (en) 2021-12-06 2021-12-06 Rotary multiplexing method based on cascade metasurface holography

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111475245.6A CN114167706B (en) 2021-12-06 2021-12-06 Rotary multiplexing method based on cascade metasurface holography

Publications (2)

Publication Number Publication Date
CN114167706A CN114167706A (en) 2022-03-11
CN114167706B true CN114167706B (en) 2022-09-30

Family

ID=80483514

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111475245.6A Active CN114167706B (en) 2021-12-06 2021-12-06 Rotary multiplexing method based on cascade metasurface holography

Country Status (1)

Country Link
CN (1) CN114167706B (en)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8199387B1 (en) * 2009-09-14 2012-06-12 Physical Optics Corporation Phase addressed holographic associative memory
US9952557B2 (en) * 2015-05-11 2018-04-24 Purdue Research Foundation System for producing ultra-thin color phase hologram with metasurfaces
CN110442007B (en) * 2019-08-14 2020-06-05 北京理工大学 Common modulation method for full-medium metasurface color printing and holographic encryption
CN111240173B (en) * 2020-01-17 2021-02-02 北京理工大学 Super-surface holographic method based on polarization and orbital angular momentum encryption
CN113156792B (en) * 2021-02-09 2022-03-18 北京理工大学 Translation holographic multiplexing method based on cascade metasurfaces
CN112799291B (en) * 2021-03-01 2022-02-15 北京理工大学 Optical encryption method based on metasurface holographic technology
CN113203687B (en) * 2021-04-29 2023-09-08 深圳大学 Multi-dimensional imaging method and device based on composite phase super-structured surface

Also Published As

Publication number Publication date
CN114167706A (en) 2022-03-11

Similar Documents

Publication Publication Date Title
CN109459870B (en) Multi-channel vector holographic polarization multiplexing method based on birefringent medium metasurface
Wei et al. Broadband multiplane holography based on plasmonic metasurface
Zhao et al. Multichannel vectorial holographic display and encryption
Zhao et al. Polarization and Holography Recording in Real‐and k‐Space Based on Dielectric Metasurface
CN110442007B (en) Common modulation method for full-medium metasurface color printing and holographic encryption
Ni et al. Metasurface holograms for visible light
CN111240173B (en) Super-surface holographic method based on polarization and orbital angular momentum encryption
Wang et al. Real‐time tunable nanoprinting‐multiplexing with simultaneous meta‐holography displays by stepwise nanocavities
CN114690404B (en) Multi-diffraction-order independent light wave field regulation and control method based on super surface
CN113238470B (en) Code division multiplexing method based on metasurface holography
Peng et al. Mix-and-match holography.
CN114137812B (en) Triple-correlation hybrid holographic encryption method based on metasurface
CN113591357B (en) Simultaneous storage method of gray level and vector holographic image based on medium metasurface
CN109991736A (en) The method for realizing curved holographic based on the conformal super clever surface of Ω type
CN110196546B (en) Non-reciprocity asymmetric transmission wavefront modulation method based on multilayer metasurfaces
CN113885104B (en) Super-surface structure multiplexing method based on phase change material and application thereof
CN113156792B (en) Translation holographic multiplexing method based on cascade metasurfaces
CN114167706B (en) Rotary multiplexing method based on cascade metasurface holography
CN114759985A (en) Optical encryption system and method based on super surface
CN114894718A (en) Phase restoration method based on anisotropic super surface
Márquez et al. Information multiplexing from optical holography to multi-channel metaholography
Desai et al. Generation of V-point polarization singularity array by Dammann gratings
CN105116706A (en) Synthetic phase shifting digital holographic microscopy
Shen et al. Electrically tunable all-dielectric metasurfaces integrated with nematic liquid crystals for information encryption
CN112882369B (en) Optical secret sharing method based on cascade metasurface holography

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant