CN111025666B - Multi-mode super surface for realizing dual-wavelength pseudo color coding and design method thereof - Google Patents

Multi-mode super surface for realizing dual-wavelength pseudo color coding and design method thereof Download PDF

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CN111025666B
CN111025666B CN201911291855.3A CN201911291855A CN111025666B CN 111025666 B CN111025666 B CN 111025666B CN 201911291855 A CN201911291855 A CN 201911291855A CN 111025666 B CN111025666 B CN 111025666B
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light
red
nano
green
brick
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CN111025666A (en
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郑国兴
李嘉鑫
李子乐
单欣
李仲阳
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Wuhan University WHU
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F3/00—Labels, tag tickets, or similar identification or indication means; Seals; Postage or like stamps
    • G09F3/02—Forms or constructions
    • G09F3/0291—Labels or tickets undergoing a change under particular conditions, e.g. heat, radiation, passage of time
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F3/00—Labels, tag tickets, or similar identification or indication means; Seals; Postage or like stamps
    • G09F3/02—Forms or constructions
    • G09F2003/0208—Indicia
    • G09F2003/0213—Concealed data

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  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
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Abstract

The invention provides a multi-mode super-surface for realizing double-wavelength pseudo-color coding and a design method thereof, which can effectively code and decode red and green components in incident ray polarization light so as to form a pseudo-color pattern in a near field, wherein the super-surface material is composed of nano brick unit structures capable of simultaneously responding to red light and green light. The nano brick unit structure is equivalent to a polarizer for incident red and green line polarized light, the light transmission axis is vertical, and transflective multiplexing can be realized. The nano-brick can effectively adjust the proportion of red and green components in incident ray polarization light according to different rotation angles, and a mapping is established between a monochromatic gray value and different colors, so that a pseudo-color pattern is formed in a near field. The pseudo-color coding multi-mode super surface provided by the invention can realize the modulation of the proportion of the red component and the green component in incident light only by changing the rotation angle of the nano brick, has small volume, low cost, light weight and simple design thought, and is very suitable for being applied in a micro photoelectric system.

Description

Multi-mode super surface for realizing dual-wavelength pseudo color coding and design method thereof
Technical Field
The invention belongs to the fields of micro-nano optics and polarized optics, and particularly relates to a multi-mode super surface for realizing dual-wavelength pseudo-color coding and a design method thereof.
Background
Image display is one direction of great importance in the field of optics. The super surface is used for realizing the display of the near field image, and the resolution of the image can be greatly improved. The ability to distinguish gray levels is weak, up to 20 gray levels, but the ability to distinguish different colors is particularly strong, and can exceed one thousand levels. Therefore, different gray scales of one gray scale image are mapped into corresponding colors (pseudo colors), namely, gray scale changes which cannot be distinguished by human eyes are applied with different colors, so that an observer can easily distinguish different layers, and the acquisition amount of useful information is greatly improved. Therefore, the method for carrying out the pseudo-color processing on the gray level image is a very effective image enhancement technology and has wide application market and technical redevelopment prospect. The multi-mode super-surface image display method based on the pseudo-color coding ensures the super-surface display to have extremely high resolution, and establishes a mapping between different gray scales and colors, thereby converting a target gray scale image into a pseudo-color image and greatly improving the visibility of the pattern.
Disclosure of Invention
Aiming at the defects of the traditional image display, the invention provides a multi-mode super surface capable of efficiently realizing dual-wavelength pseudo-color coding and a design method thereof by combining the polarization theory and designing the geometric dimension of the silver nano bricks and the rotation angle of the array.
One of the purposes of the invention is to provide a multi-mode super surface for realizing dual-wavelength pseudo color coding, wherein the corner of the nano brick of the super surface material utilizes the variable formula I of Malus law0cos4Theta is determined, and the rotation angles are distributed between 0-90 degrees. The super-surface material realizes near-field pseudo-color coding through a nano brick unit structure array with a single geometric dimension for the first time, and can easily realize the change of image colors by changing the corner of a sample wafer. The invention has simple structure and principle, easy processing and good application potential in the aspects of pseudo-color treatment, high-resolution color image display and optical anti-counterfeiting;
the invention also aims to provide a design method of the multi-mode super surface for realizing the dual-wavelength pseudo color coding, which skillfully superposes red and green gray scale images with reversed gray scales by utilizing the dual-wavelength resonance characteristic of the super surface material and the Malus law, thereby coding a pseudo color pattern on the surface of the super surface material and greatly improving the available information content of the image.
In order to achieve the purpose, the scheme of the invention is as follows:
in a first aspect, the present invention provides a multi-mode metasurface for implementing dual wavelength pseudo color coding, characterized by:
the super-surface material is formed into a nano brick unit array by nano bricks capable of simultaneously responding to red light and green light, the interval between different nano brick unit structures is a period CS, and nano brick units at different positions correspond to different corners;
the nanometer brick unit structure has the effect on red and green line polarization equivalent to a transflective multiplexing polarizer; when incident red and green line polarized light is polarized along the long axis of the nano brick, the red light is reflected, and the green light is transmitted; when incident red and green line polarized light is polarized along the minor axis of the nano brick, green light is reflected, and red light is transmitted;
designing the corner of each nano-brick on the nano-brick array, wherein the corner of each nano-brick is represented by the variable formula I (I) of the Malus law0cos4Determining theta, and distributing the theta at 0-90 degrees; when incident red and green light passes through a polarizer and then passes through the super surface, reflected light passes through an analyzer again, and color nano printing patterns are formed on the surface of the super surface material, wherein the formed color nano printing colors are continuously changed between red and green; the polarizer and the analyzer are both polarized along the x-axis.
In a second aspect, the present invention provides a design method for displaying a multi-mode super-surface image to implement dual-wavelength pseudo color coding, which is characterized in that: the method comprises the following steps:
(1) according to the two selected incident light wavelengths, when the incident ray polarization light vertically irradiates the nano brick unit through electromagnetic simulation software, the red light polarized along the long axis has high reflection efficiency and the green light has high transmission efficiency; the red light polarized along the short axis has high transmission efficiency, the green light reflection efficiency is high as a target, and the cycle CS of the nano brick unit structure, the width W, the length L and the height H of the nano brick unit structure are optimized;
(2) the angle of rotation of the nano-brick is defined as the included angle between the long axis of the nano-brick and the x axis, the incident light is incident on the sample plate through the polarizer with the polarization direction as the x axis, the reflected light passes through the analyzer with the polarization direction as the x axis again, and the light intensity of the red light in the reflected light is I according to the Malus lawR＝IR0cos4Theta, green light intensity of IG＝IG0sin4Theta; in the formula IR0And IG0The light intensity of red light and green light in incident light respectively;
(3) selecting a red gray scale image, and calculating the rotation angle of each nano brick on the array according to the light intensity formula of the red reflected light in the step (2), wherein the rotation angle range is 0-90 degrees; if a red laser source is adopted to be incident on the super-surface according to the optical path in the step (2), restoring a selected red gray-scale image; converting a light source into red and green laser, and combining a red light reflection light intensity formula and a green light reflection light intensity formula to obtain a pseudo color pattern with complementary red component and green component gray levels;
(4) preparing a multi-mode super surface for realizing double-wavelength pseudo color coding by adopting a photoetching process according to the silicon nano brick array structure determined in the step (3);
(5) and (4) according to the super-surface obtained in the step (4), observing the color nano printing pattern on the surface of the sample wafer after the incident light passes through the polarizer and the analyzer.
The visibility of the pseudo-color pattern encoded according to the method is greatly improved compared to the original grey scale map. When the pseudo color coding pattern of the near field is observed, a polarizer and an analyzer are needed to be configured, when incident double-color light is incident on a sample through the polarizer, reflected light passes through the analyzer, and a frame of pseudo color coding nano printing pattern is observed on the surface of the super-surface material through a microscope;
the invention has the following advantages and beneficial effects:
(1) the provided dual-wavelength pseudo-color coding multi-mode super-surface realizes color modulation (521.74 nm-615.25 nm) of incident light, when incident ray polarization light is polarized along the long axis of a nano brick, the reflection efficiency of red light (487.61Thz) can reach 92.16%, and the transmission efficiency of green light can reach 75.38%; when incident linear polarization light is polarized along the short axis of the nano brick, the reflection efficiency of green light (483.87Thz) can reach 77.95 percent, and the transmission efficiency of red light can reach 91.92 percent; the mixing of red and green components in different proportions in reflected (transmitted) light can be realized by rotating the nano-bricks.
(2) The provided dual-wavelength pseudo-color coding multi-mode super surface can establish a mapping between different gray scales and colors according to Malus law, namely I0cos4After the turning angle of the nano-brick is calculated by theta, the nano-brick array can encode the original gray-scale image into a pseudo-color pattern, so that the gray-scale change is converted into color change, and the visibility of the pattern is greatly improved;
(3) compared with the traditional image display, the pattern resolution provided by the invention is greatly improved to reach 74705dpi, and a decoding process is required, so that the method has certain confidentiality;
(4) compared with the traditional image display device, the invention has the advantages of small volume, low cost, light weight and capability of realizing dynamic modulation;
(5) the structure has an ultramicro structure and can be widely applied to the field of photonic integration;
(6) the metal nano brick array structure can be processed by a standard photoetching process, and the process is simple;
(7) provides a new idea for the design and preparation of image display and encryption, and has great reference value and application prospect.
Drawings
FIG. 1 is a schematic diagram of a structural unit of a near-far field multiplexing super surface in example 1, and a rotation angle θ is an included angle between a long axis of a nano brick and an x axis;
FIG. 2 is a schematic diagram of a three-dimensional structure of a part of the silver nanobead array structure in example 1;
fig. 3 is a graph showing simulation results of the silver nanoblock array of example 1 on incident light, wherein the x-axis is wavelength and the y-axis is reflection efficiency and transmission efficiency, including long-axis reflection efficiency, short-axis reflection efficiency, long-axis transmission efficiency, and short-axis transmission efficiency.
Fig. 4 is a schematic diagram of the principle of encoding a red grayscale image into a pseudo-color image in embodiment 1;
FIG. 5 is a schematic optical path diagram for decoding a reflected near-field pseudo-color pattern in example 1;
FIG. 6 is a schematic optical path diagram for decoding a transmitted near-field pseudo-color pattern in example 1;
in the figure: 1. nano bricks; 2. a substrate; l, the long axis size of the nano brick; w, the minor axis size of the nano brick; H. the height of the nano brick is high; CS and the distance between the nano bricks.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
The embodiment of the invention provides a multi-mode super-surface material for realizing dual-wavelength pseudo-color coding, which is formed by a transparent substrate, namely a nano unit array etched on the surface of the substrate, wherein the nano unit array comprises a plurality of nano unit structures (in the embodiment, the nano unit structures are silver nano bricks), and a gray pattern can be coded into a pseudo-color pattern through design.
The silver nano brick array structure shown in fig. 1-2 comprises two layers of silver nano bricks 1 and a substrate 2 from top to bottom in sequence. The silver nano brick array 1 is formed by periodically arranging silver nano brick unit structures, the silver nano bricks are cuboids, and the length, the width and the height of the silver nano bricks are sub-wavelength sizes. The structure of a single silver nanobead unit is shown in fig. 1. In this embodiment, the substrate 2 is a silicon dioxide substrate. Fig. 2 is a nano-brick array composed of nano-brick unit structures.
Selecting 521.74nm and 615.25nm as working wavelengths, and adopting the existing CST STUDIO SUITE electromagnetic simulation tool to optimize the structure of the silicon nano brick unit under the working wavelengths, so that the red light reflection efficiency and the green light transmission efficiency are highest when incident linear polarization light is polarized along the long axis of the nano brick; when incident linear polarization light is polarized along the short axis of the nano brick, the green light reflection efficiency and the red light reflection efficiency are highest; by rotating the nano-brick array structure, the change of reflected light from red light to green light can be realized, so that a mapping is established between different gray scales and colors. In this embodiment, the optimized silicon nanoblock has a length L of 140nm, a width W of 95nm, a thickness H of 70nm, and a unit structure CS of 340 nm; the simulated polarization efficiency graph is shown in fig. 3, the reflection efficiency of the red light polarized along the major axis reaches 90.92%, and the reflection efficiency of the green light polarized along the minor axis reaches 77.95%;
after the first step, the structure of a single silver nano brick unit can be determined, a color image with n pixels in the color range between red and green is selected, as shown in fig. 4a, and the Malus law variable formula I is obtained according to the gray value of each pixel point and the reflection efficiency of the long axis of red lightR＝IR0cos4And theta, determining the rotation angle theta (0-90 degrees) of each pixel point nano brick, as shown in fig. 4b and c. According to the calculated rotation angle, combining the short-axis reflection efficiency I of the green lightG＝IG0sin4Theta; overlapping the red gray scale image and the green gray scale imageAdding the false color pattern to the coded pattern, and the coded patterns in the patterns of 0 degree and 90 degree are shown in fig. 4d and e respectively.
And preparing the multi-mode super surface material for realizing the dual-wavelength pseudo-color coding by adopting a photoetching process according to the determined silicon nano brick array structure. According to the obtained super-surface, after the incident light passes through the polarizer and the analyzer, the color nano-printed pattern is observed on the surface of the sample wafer, and the reflection light path diagram and the transmission light path diagram are shown in fig. 5 and 6.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.

Claims (2)

1. A multi-mode metasurface implementing dual wavelength pseudo color coding, comprising:
the super-surface material is formed into a nano brick unit array by nano bricks capable of simultaneously responding to red light and green light, the interval between different nano brick unit structures is a period CS, and nano brick units at different positions correspond to different corners;
the nanometer brick unit structure has the effect on red and green line polarization equivalent to a transflective multiplexing polarizer; when incident red and green line polarized light is polarized along the long axis of the nano brick, the red light is reflected, and the green light is transmitted; when incident red and green line polarized light is polarized along the minor axis of the nano brick, green light is reflected, and red light is transmitted;
designing the corner of each nano-brick on the nano-brick array, wherein the corner of each nano-brick is represented by the variable formula I (I) of the Malus law0cos4Determining theta, and distributing the theta at 0-90 degrees; when incident red and green light passes through a polarizer and then passes through the super surface, reflected light passes through an analyzer again, and color nano printing patterns are formed on the surface of the super surface material, wherein the formed color nano printing colors are continuously changed between red and green; the polarizer and the analyzer are both polarized along the x-axis.
2. A design method for realizing dual wavelength pseudo color coded multi-mode super surface image display as claimed in claim 1, wherein: the method comprises the following steps:
(1) according to the two selected incident light wavelengths, when the incident ray polarization light vertically irradiates the nano brick unit through electromagnetic simulation software, the red light polarized along the long axis has high reflection efficiency and the green light has high transmission efficiency; the red light polarized along the short axis has high transmission efficiency, the green light reflection efficiency is high as a target, and the cycle CS of the nano brick unit structure, the width W, the length L and the height H of the nano brick unit structure are optimized;
(2) the angle of rotation of the nano-brick is defined as the included angle between the long axis of the nano-brick and the x axis, the incident light is incident on the sample plate through the polarizer with the polarization direction as the x axis, the reflected light passes through the analyzer with the polarization direction as the x axis again, and the light intensity of the red light in the reflected light is I according to the Malus lawR＝IR0cos4Theta, green light intensity of IG＝IG0sin4Theta; in the formula IR0And IG0The light intensity of red light and green light in incident light respectively;
(3) selecting a red gray scale image, and calculating the rotation angle of each nano brick on the array according to the light intensity formula of the red reflected light in the step (2), wherein the rotation angle range is 0-90 degrees; if a red laser source is adopted to be incident on the super-surface according to the optical path in the step (2), restoring a selected red gray-scale image; converting a light source into red and green laser, and combining a red light reflection light intensity formula and a green light reflection light intensity formula to obtain a pseudo color pattern with complementary red component and green component gray levels;
(4) preparing a multi-mode super surface for realizing double-wavelength pseudo color coding by adopting a photoetching process according to the silicon nano brick array structure determined in the step (3);
(5) and (4) according to the super-surface obtained in the step (4), observing the color nano printing pattern on the surface of the sample wafer after the incident light passes through the polarizer and the analyzer.
CN201911291855.3A 2019-12-16 2019-12-16 Multi-mode super surface for realizing dual-wavelength pseudo color coding and design method thereof Expired - Fee Related CN111025666B (en)

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