Extrinsic chiral metasurface structure and method for modulating circularly polarized light reflection intensity
By designing an external chiral superstructure structure containing a vertically extended rod body, the circular polarized light reflection intensity is adjusted by regulating the circular polarized light field in the prior art, and high chirality is achieved Sequence grayscale imaging and image confidentiality.
Patent Information
- Application Number
- CN202211277533.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-19
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2042-10-19
AI Technical Summary
It is difficult to process and prepare complex micro-nano structures at low cost to achieve effective regulation of the circular polarized light field, especially in the visible and near-infrared bands, and it is impossible to simply and effectively regulate the circular polarized light reflection intensity.
Design an external chiral superstructure structure consisting of a plurality of matrix structural units, including a first metal layer, a dielectric layer and a second metal layer, the second metal layer including a vertically extending first rod body and a second rod The body, by changing the length of the first rod body, controls the reflection intensity of the specific rotating circularly polarized light, and maintains the reflection intensity of the other rotating circularly polarized light.
It realizes direct regulation of circularly polarized light reflection intensity at specific wavelengths, supports chiral high-order grayscale imaging, and has the advantages of convenient structural design and high image confidentiality.
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Figure CN115586598B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of micro-nano optical technology, and in particular to an external chiral metasurface structure and a method for modulating the reflection intensity of circularly polarized light. Background Art
[0002] In artificial microstructures, strong chiral optical responses mostly exist in three-dimensional metamaterials and few-layer metasurfaces that lack mirror symmetry. However, in the visible and near-infrared bands, it is impossible to use existing micro-nanofabrication processes to low-cost process and prepare complex micro-nanostructures and precisely control their structural parameters to obtain the required chiral optical response, thereby achieving effective regulation of circularly polarized light fields. Recently, the extrinsic chiral optical response in a single-layer metasurface composed of simple structures has provided a new and powerful means for the effective regulation of circularly polarized light fields in the visible and near-infrared bands. At present, by using the extrinsic chiral optical response of the metasurface, the selective reflection of left-handed and right-handed circularly polarized light fields can be achieved at a specific angle by changing the angle at which the incident light enters the metasurface. However, a simple and effective method for continuously regulating the intensity of circularly polarized light using extrinsic chiral metasurfaces has not yet been proposed. Summary of the invention
[0003] The purpose of the present invention is to provide an external chiral metasurface structure and a method for modulating the reflection intensity of circularly polarized light. When the circularly polarized light is incident obliquely along a specific direction, the reflection intensity of a certain chiral circularly polarized light can be directly regulated at a specific wavelength by controlling only a single structural parameter of the metasurface, and the reflection intensity of another circularly polarized light can be kept basically unchanged, thereby realizing chiral high-order grayscale imaging.
[0004] In a first aspect, the extrinsic chiral metasurface structure provided by the present invention is composed of a plurality of base structure units, wherein the base structure unit comprises: a first metal layer; a dielectric layer disposed on the first metal layer; and a second metal layer disposed on the dielectric layer;
[0005] The second metal layer includes: a first rod and a second rod, the first rod and the second rod respectively extend along the surface of the dielectric layer, the first rod is spaced from the second rod, and the extension direction of the first rod is perpendicular to the extension direction of the second rod.
[0006] In combination with the first aspect, the present invention provides a first possible implementation manner of the first aspect, wherein the matrix structure unit serves as a pixel point of a grayscale image, and the first rod length dimensions provided for two pixel points with a grayscale difference have a difference.
[0007] In combination with the first aspect, the present invention provides a second possible implementation manner of the first aspect, wherein the length of the first rod is 400 nm to 520 nm.
[0008] In combination with the first aspect, the present invention provides a third possible implementation manner of the first aspect, wherein the thickness of the first metal layer is 90 nm to 100 nm.
[0009] In combination with the first aspect, the present invention provides a fourth possible implementation manner of the first aspect, wherein the thickness of the dielectric layer is 100 nm to 160 nm.
[0010] In combination with the first aspect, the present invention provides a fifth possible implementation manner of the first aspect, wherein the thickness of the first rod body and the second rod body are both 20 nm to 40 nm.
[0011] In combination with the first aspect, the present invention provides a sixth possible implementation manner of the first aspect, wherein the width of the first rod is 60 nm to 80 nm.
[0012] In combination with the first aspect, the present invention provides a seventh possible implementation manner of the first aspect, wherein the width of the second rod is 65 nm to 85 nm.
[0013] In combination with the first aspect, the present invention provides an eighth possible implementation manner of the first aspect, wherein the length of the second rod is 150 nm to 200 nm.
[0014] In a second aspect, the method for modulating the reflection intensity of circularly polarized light provided by the present invention adopts the external chiral metasurface structure described in the first aspect, and comprises the following steps:
[0015] Define the extending direction of the first rod as the x-axis direction, and the extending direction of the second rod as the y-axis direction;
[0016] A plurality of matrix structural units are arrayed along the x-axis and the y-axis respectively;
[0017] Under the condition of oblique incidence of left-handed circularly polarized light or right-handed circularly polarized light, the length of the first rod in each matrix structural unit is changed to modulate the reflection intensity of the circularly polarized light with a specific rotation;
[0018] The angle between the direction of the incident light and the x-axis is 45°, and the angle between the direction of the incident light and the z-axis is 45°.
[0019] The embodiments of the present invention bring the following beneficial effects: a plurality of base structure units are used to form an external chiral metasurface structure, in which a first metal layer, a dielectric layer and a second metal layer are arranged in sequence, and the second metal layer includes a first rod and a second rod, the first rod and the second rod are respectively extended along the surface of the dielectric layer, the first rod and the second rod are arranged at intervals, and the extension direction of the first rod is perpendicular to the extension direction of the second rod, when circularly polarized light is obliquely incident along a specific direction, only the length parameter of the first rod is changed to directly adjust the reflection intensity of a specific handedness circularly polarized light at a specific wavelength, and the reflection intensity of another circularly polarized light can be kept basically unchanged, thereby realizing chiral high-order grayscale imaging, which has the advantages of convenient structural design and high image confidentiality.
[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related technologies, the drawings required for use in the specific embodiments or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0022] Figure 1 A schematic diagram of a base structure unit of an extrinsic chiral metasurface structure provided by an embodiment of the present invention;
[0023] Figure 2 A top view of a first base structure unit of an extrinsic chiral metasurface structure provided by an embodiment of the present invention;
[0024] Figure 3 A schematic diagram of the reflection spectrum of the first base structure unit of the extrinsic chiral metasurface structure provided in an embodiment of the present invention under the conditions of oblique incidence of left-handed and right-handed circularly polarized light in the wavelength range of 1200nm to 1500nm;
[0025] Figure 4 A top view of a second base structure unit of an extrinsic chiral metasurface structure provided by an embodiment of the present invention;
[0026] Figure 5 A schematic diagram of the reflection spectrum of the second base structure unit of the extrinsic chiral metasurface structure provided in an embodiment of the present invention under the conditions of oblique incidence of left-handed and right-handed circularly polarized light in the wavelength range of 1200nm to 1500nm;
[0027] Figure 6A schematic diagram showing how the reflection intensity of the first base structure unit of the extrinsic chiral metasurface structure provided in an embodiment of the present invention changes with the length of the first rod under the conditions of left-handed and right-handed circularly polarized light at a wavelength of 1330 nm;
[0028] Figure 7 A schematic diagram showing how the reflection intensity of the second base structure unit of the extrinsic chiral metasurface structure provided in an embodiment of the present invention changes with the length of the first rod under left- and right-handed circularly polarized light conditions at a wavelength of 1330 nm.
[0029] Icon: 100 - first metal layer; 200 - dielectric layer; 300 - second metal layer; 310 - first rod; 320 - second rod. DETAILED DESCRIPTION
[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0031] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. Physical quantities in formulas, if not separately marked, should be understood as basic quantities of the base units of the International System of Units, or derived quantities derived from the basic quantities through mathematical operations such as multiplication, division, differentiation or integration.
[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0033] like Figure 1 , Figure 2 and Figure 4As shown, the extrinsic chiral metasurface structure provided by the embodiment of the present invention is composed of a plurality of base structure units, the base structure units comprising: a first metal layer 100; a dielectric layer 200 disposed on the first metal layer 100; and a second metal layer 300 disposed on the dielectric layer 200; the second metal layer 300 comprises: a first rod 310 and a second rod 320, the first rod 310 and the second rod 320 respectively extending along the surface of the dielectric layer 200, the first rod 310 and the second rod 320 being spaced apart, and the extension direction of the first rod 310 is perpendicular to the extension direction of the second rod 320.
[0034] Specifically, the base structure units are distributed in an array in the x-axis and y-axis directions, and the size of a base structure unit in the x-axis and y-axis directions is 560nm. The first metal layer 100 can be configured as a gold reflective layer, or it can be replaced by other metal materials; the dielectric layer 200 is configured as a silicon dioxide interlayer, or it can be replaced by other dielectric material interlayers; the second metal layer 300 is configured as a gold rod structure layer, or it can be replaced by other metal materials. Figure 1 and Figure 2 As shown, the first rod 310 extends along the x-axis, and the second rod 320 extends along the y-axis, thereby forming a first base structure unit; Figure 4 As shown, compared with the first base structure unit, the second base structure unit is formed by rotating 90 degrees around the z-axis, wherein the first rod 310 extends along the y-axis and the second rod 320 extends along the x-axis.
[0035] In an embodiment of effect verification, when the length of the first rod 310 in the metasurface structure is 520 nm, the length of the second rod 320 is 175 nm, the width of the first rod 310 is 70 nm, the width of the second rod 320 is 75 nm, the thickness of the first metal layer 100 is 90 nm, the thickness of the dielectric layer 200 is 130 nm, and the thickness of the first rod 310 and the second rod 320 is 30 nm, under the condition of oblique irradiation of left-handed circularly polarized light or right-handed circularly polarized light (the angle between the incident light direction and the x-axis theta is 45°, so that the angle between the incident light direction and the z-axis phi is 45°), within the wavelength range of 1200 nm to 1500 nm, the reflection spectrum of the first matrix structure unit is shown in FIG. Figure 3 As shown, the reflectance spectrum of the second matrix structural unit can be found in Figure 5 See Figure 3 The extrinsic chiral metasurface structure has significant circular dichroism at a wavelength of 1330nm, which achieves a strong absorption efficiency of about 99% for RCP, while LCP achieves a high reflection efficiency of about 80% in the entire band. Figure 5When the base structural unit constituting the metasurface is rotated 90° along the z-axis, the circular dichroism of the external chiral metasurface structure is exactly opposite to that before the structure is rotated, achieving high reflection of RCP and high-efficiency absorption of LCP. When the wave vector direction deviates from theta=phi=±45°, the circular dichroism intensity gradually decreases until the chiral light resonance completely disappears at normal incidence (theta=0 or phi=0°), and both types of circularly polarized light are reflected with high efficiency.
[0036] See also Figure 2 and Figure 6 By adjusting the length L1 of the first rod 310, the overall translation of the spectrum within the wavelength band can be achieved, so the continuous regulation of the reflection intensity of RCP at 1330nm can be achieved without affecting the reflection intensity of LCP at this wavelength. Figure 4 and Figure 7 By adjusting the length L1 of the first rod 310, the overall translation of the spectrum within the wavelength band can be achieved, so the reflection intensity of LCP at 1330nm can be continuously regulated without affecting the reflection intensity of RCP at this wavelength. When left-handed or right-handed circularly polarized light with a wavelength of 1330nm is incident along a specific direction, the reflection intensity can be modulated from 0.8 to 0.
[0037] In the embodiment of the present invention, the matrix structure unit is used as a pixel point of the grayscale image, and the length dimension of the first rod 310 provided for two pixels with grayscale difference has a difference. By adjusting a single parameter (the length dimension of the first rod 310), the reflection intensity of a specific pixel point under a specific circularly polarized light condition can be regulated, thereby achieving grayscale adjustment of the pixel point. Since the length dimension of the first rod 310 can be continuously adjusted, high-order grayscale imaging can be achieved. See Figure 6 and Figure 7 The length dimension L1 of the first rod 310 is set to 400nm, 479nm, 500nm or 520nm respectively. Under different chiral circularly polarized light oblique incidence (theta=phi=±45°), the four structures show significantly different reflection intensities, thereby realizing fourth-order chiral grayscale imaging.
[0038] like Figure 1 , Figure 2 , Figure 4 , Figure 6 and Figure 7 As shown, the length L1 of the first rod 310 is 400 nm to 520 nm. The length L1 of the first rod 310 can also be set to 420 nm, 440 nm, 460 nm or 500 nm.
[0039] like Figure 1As shown, the thickness t1 of the first metal layer 100 is 90 nm to 100 nm, and the thickness t1 of the first metal layer 100 can be set to 92 nm, 95 nm or 97 nm.
[0040] Furthermore, the thickness t2 of the dielectric layer 200 is 100 nm to 160 nm. The thickness t2 of the dielectric layer 200 may be set to 110 nm, 120 nm, 130 nm, 140 nm or 150 nm.
[0041] Furthermore, the thickness t3 of the first rod 310 and the second rod 320 are both 20 nm to 40 nm, and the thickness t3 of the second metal layer 300 can be set to 22 nm, 25 nm, 27 nm, 30 nm, 32 nm or 35 nm.
[0042] Furthermore, the width w1 of the first rod 310 is 60 nm to 80 nm, and the width w1 of the first rod 310 can be set to 65 nm, 70 nm or 75 nm.
[0043] Furthermore, the width w2 of the second rod 320 is 65 nm to 85 nm, and the width w2 of the second rod 320 can be set to 70 nm, 75 nm or 80 nm.
[0044] Furthermore, the length L2 of the second rod 320 is less than the length L1 of the first rod 310 , and the length L2 of the second rod 320 is 150 nm to 200 nm. The length L2 of the second rod 320 can be set to 160 nm, 170 nm, 180 nm or 190 nm.
[0045] like Figure 1 , Figure 2 and Figure 3 As shown, the method for modulating the reflection intensity of circularly polarized light provided in the embodiment of the present invention adopts the external chiral metasurface structure described in the above embodiment, and includes the following steps:
[0046] A plurality of matrix structural units are arrayed along the x-axis and the y-axis to form a grayscale image plane; when left-handed circularly polarized light or right-handed circularly polarized light is incident at an angle along a specific direction, the length dimension of the first rod 310 is changed to change the reflection intensity of the circularly polarized light of a specific rotation; wherein the direction of the incident light is at an angle of 45° to the x-axis, and the direction of the incident light is at an angle of 45° to the z-axis.
[0047] In the embodiment of the present invention, an external chiral metasurface structure is used, which can directly regulate the reflection intensity of a specific chiral circularly polarized light at a specific wavelength by controlling only a single parameter (the length dimension of the first rod 310) when circularly polarized light is obliquely incident in a specific direction, and keep the reflection intensity of another chiral circularly polarized light basically unchanged, thereby realizing high-order chiral grayscale imaging, which can be used for image encryption and has the advantages of convenient design and easy implementation.
[0048] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. An extrinsic chiral metasurface structure, composed of a plurality of matrix structural units, characterized in that: The base structure unit comprises: a first metal layer (100); a dielectric layer (200) disposed on the first metal layer (100); and a second metal layer (300) disposed on the dielectric layer (200); The second metal layer (300) comprises: a first rod (310) and a second rod (320), wherein the first rod (310) and the second rod (320) extend along the surface of the dielectric layer (200) respectively, the first rod (310) and the second rod (320) are arranged at intervals, and the extension direction of the first rod (310) is perpendicular to the extension direction of the second rod (320).
2. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The matrix structure unit serves as a pixel point of a grayscale image, and the length dimensions of the first rod body (310) provided at two pixel points with a grayscale difference have a difference.
3. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The length of the first rod (310) is 400 nm to 520 nm.
4. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The thickness of the first metal layer (100) is 90nm-100nm.
5. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The thickness of the dielectric layer (200) is 100 nm to 160 nm.
6. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The thickness of the first rod (310) and the second rod (320) are both 20nm-40nm.
7. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The width of the first rod (310) is 60nm-80nm.
8. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The width of the second rod (320) is 65nm-85nm.
9. The extrinsic chiral metasurface structure according to claim 1, characterized in that: The length of the second rod (320) is 150nm-200nm.
10. A method for modulating the reflection intensity of circularly polarized light, characterized in that: The method adopts the extrinsic chiral metasurface structure according to any one of claims 1 to 9, and comprises the following steps: The extension direction of the first rod (310) is defined as the x-axis direction, and the extension direction of the second rod (320) is defined as the y-axis direction; A plurality of base structure units are arrayed along the x-axis and the y-axis respectively; Under the condition of oblique incidence of left-handed circularly polarized light or right-handed circularly polarized light, the length of the first rod (310) in each base structure unit is changed to modulate the reflection intensity of the circularly polarized light with a specific rotation; The angle between the direction of the incident light and the x-axis is 45°, and the angle between the direction of the incident light and the z-axis is 45°.