Nanometer crescent array structure for enhancing chiral optics

Abstract

The invention relates to the technical field of production and processing, and particularly discloses a nano crescent array structure for enhancing chiral optics, which comprises a first substrate and crescent metal positioned on the first substrate, wherein the crescent metal is a chiral structure unit which is arranged on the upper surface of the first substrate and is in a hexagonal array, the chiral structure unit comprises metal crescent, the irregularity of the metal crescent can be adjusted, the crescent center spacing distances of the metal crescent are equal, and the metal crescent is arranged on the upper surface of the first substrate and is in a hexagonal array; the irregularity of the metal crescent can be adjusted, the chiral structure units are uniformly arranged in the transverse direction and the longitudinal direction of the first substrate, and the first substrate is made of a light-transmitting material. According to the nano crescent array structure for enhancing chiral optics, a regular hexagon arrangement mode is added on the basis of an original single irregular metal crescent, so that the circular dichroism of the chiral optical structure is remarkably enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of optical array structures, and in particular to a nano-crescent array structure for enhancing chiral optics. Background Art

[0002] Chirality refers to the property that a structure and its mirror image cannot overlap. Chiral structures are commonly found in nature, such as biomacromolecules such as proteins, glycosylation and DNA. Chirality plays a key role in biochemistry and life evolution. Chirality can be divided into intrinsic chirality and extrinsic chirality according to its structural characteristics. Intrinsic chirality refers to the chirality of the structure itself, while extrinsic chirality refers to the chirality formed by the structure and the incident light.

[0003] Circular dichroism (CD) is an optical technique used to measure the difference in absorption of circularly polarized light by molecules. It is a very important method for studying chiral compounds. In the study of the asymmetry of chiral molecules, when left-handed circularly polarized light and right-handed circularly polarized light are incident, the chiral material will show different effective refractive indices and propagation speeds. Since the interaction between chiral molecules and electromagnetic waves is very weak, the sensitivity and accuracy of detection are greatly limited.

[0004] In the prior art research on chiral structures, by designing a two-dimensional metal chiral structure, it is possible to modulate the polarization characteristics of a light beam or detect the circular dichroism of a chiral substance. However, when the detected signal itself is relatively weak, the obtained circular dichroism signal is not obvious, that is, the detection effect is poor.

[0005] Therefore, we propose a nano-crescent array structure for enhancing chiral optics to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a nano-crescent array structure for enhancing chiral optics to solve the problem raised in the above background technology that when the current chiral structure detects the circular dichroism spectrum of chiral substances, when the detected signal itself is relatively weak, the obtained circular dichroism spectrum signal is not obvious and the detection effect is poor.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a nano-crescent array structure for enhancing chiral optics, comprising: a first substrate and a crescent-shaped metal located on the first substrate; wherein the crescent-shaped metal is a chiral structural unit on the upper surface of the first substrate and arranged in a hexagonal array, and the chiral structural unit comprises: metal crescents with adjustable irregularity and equal spacing between the centers of the crescents.

[0008] Preferably, the metal crescents are arranged in a hexagonal array on the upper surface of the first substrate, and the irregularity of the metal crescents is adjustable.

[0009] Preferably, the chiral structural units are evenly arranged in both the lateral and longitudinal directions of the first substrate.

[0010] Preferably, the period of the chiral structural units arranged in the horizontal direction ranges from 400 to 500 nm.

[0011] Preferably, the period of the chiral structural units arranged in the vertical direction ranges from 400√3 to 500√3 nm.

[0012] Preferably, the distances between the center points of the chiral structural units are the same.

[0013] Preferably, the first substrate is made of a light-transmitting material.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: the nano-crescent array structure for enhancing chiral optics significantly enhances the circular dichroism of the chiral optical structure by adding a regular hexagonal arrangement pattern on the basis of the original single irregular metal crescent. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0016] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0017] Figure 2 It is a schematic diagram of the top plan structure of the present invention;

[0018] Figure 3 Schematic diagram of the chiral structural unit structure of the present invention;

[0019] Figure 4 A schematic diagram of crescent irregularity in a chiral structural unit defined in the present invention;

[0020] Figure 5 A schematic diagram of the principle of producing circular dichroism in the present invention;

[0021] Figure 6 This is a structural comparison diagram of the chiral structural units of the present invention that are not arranged in a regular hexagonal array;

[0022] Figure 7 This is a structural comparison diagram of the chiral structural units arranged in a regular hexagonal array according to the present invention;

[0023] Figure 8 The circular dichroism transmission spectrum of the chiral structural unit of the metal crescent with periodic array structure arrangement of the present invention;

[0024] Fig. 9 This is a comparison diagram of the unit circular dichroism spectra of the present invention.

[0025] In the figure: 11, first substrate; 12, metal crescent; 13, chiral structural unit; 21, second substrate; 22, central metal crescent; 23, incomplete metal crescent; 31, third substrate; 32, shadow crescent. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0027] See also Figure 1-9 , the present invention provides the following technical solutions:

[0028] A nano-crescent array structure for enhancing chiral optics, comprising: a first substrate 11, a metal crescent 12, a chiral structural unit 13, a second substrate 21, a central metal crescent 22, a broken metal crescent 23, a third substrate 31, and a shadow crescent 32;

[0029] Embodiment 1

[0030] See also Figure 1 and Figure 2 The chiral optical array structure includes: a first substrate 11 and a metal crescent 12 located on the first substrate 11.

[0031] The first substrate 11 is made of a material having high transmittance to the used light wavelength band, such as silicon dioxide, quartz, etc.

[0032] The first substrate 11 is provided with a plurality of chiral structural units 13 which cover the upper surface of the first substrate 11 and are arranged in a regular hexagonal array. The chiral structural units 13 include: a complete metal crescent 12 in the center and four incomplete metal crescents around it (the four incomplete metal crescents can be spliced ​​into a complete metal crescent).

[0033] The metal crescents 12 are evenly arranged in the horizontal and vertical directions in the chiral structural unit 13. The period of the arrangement of the metal crescents 12 in the horizontal direction is Px, and the period of the arrangement in the vertical direction is Py. The length range of Px is 400nm to 500nm, and the length range of Py is 400√3nm to 500√3nm.

[0034] See also Figure 3The chiral structural unit includes a second substrate 21, a central metal crescent 22 located on the second substrate 21, and incomplete metal crescents 23 also located on the second substrate 21 and around the central metal crescent 22.

[0035] Among them, each metal crescent has the same height.

[0036] The thickness of the central metal crescent 22 is 100 nm, and the material of the central metal crescent 22 is a good conductor, including precious metals such as gold, silver, copper, and aluminum.

[0037] The metal crescent irregularity scale standard in the chiral structural unit of the embodiment of the present invention is defined by two ellipses cut perpendicularly to each other horizontally and vertically, and the crescent shape protruding in the horizontal direction is used as the specific morphology for research, see Figure 4 In order to prevent the horizontal ellipse from coinciding with the vertical ellipse boundary when it is cut up and down, the experimental example of the present invention sets the horizontal and vertical diameters L1 and L2 of the vertically arranged ellipse to be 160nm and 250nm; the horizontal and vertical diameters L3 and L2 of the horizontally arranged ellipse to be 150nm and 250nm, and the horizontally arranged ellipse is kept unchanged, and only the vertically arranged ellipse is moved along the y-axis direction, and the moving distance range L4 is 10nm to 30nm. The shadow crescent 32 is used by the present invention, and the third substrate 31 is the same as the second substrate 21 mentioned above.

[0038] The central metal crescent 22 is made of gold. The lengths of the horizontal period Px and the vertical period Py of the chiral structural unit 13 are 500nm and 500√3nm respectively. The thickness of the metal crescent 22 is 100nm. The irregularity of the metal crescent 22 is the above-mentioned cutting ellipse movement L4=20nm.

[0039] The chiral optical array structure of the present invention has an irregular metal crescent array structure with a periodic regular hexagonal matrix arrangement, so that the circular dichroism of the chiral optical structure is significantly enhanced.

[0040] Embodiment 2

[0041] See also Figure 5 When a beam of left circularly polarized light (LCP) is incident from the front of the chiral optical structure at a vertical angle, after passing through the chiral optical array structure, the transmittance of the received left-circularly polarized light is T--, and when a beam of right circularly polarized light (RCP) is incident from the front of the chiral optical structure at the same incident angle, after passing through the chiral optical structure, the transmittance of the received right-circularly polarized light is T++, where the subscript "--" represents left-circularly polarized light and "++" represents right-circularly polarized light. The circular dichroism of the chiral structure unit 13 can be expressed as:

[0042] CD=(T++-T--) / (T+++T--)

[0043] The transmittance of left-handed polarized light and right-handed polarized light after passing through a chiral optical device is different, that is, T++≠T--. Therefore, the size of CD represents the strength of the circular dichroism of the chiral optical device.

[0044] See also Figure 6 and Figure 7 , wherein the central metal crescent 22 is made of gold material, the horizontal period Px and vertical period Py lengths of the chiral structural unit 13 are 500nm and 500√3nm respectively, the thickness of the central metal crescent 22 is 100nm; the irregularity of the central metal crescent 22 is the above-mentioned cutting ellipse movement L4=20nm.

[0045] See also Figure 8 , where "T--" represents left-handed polarized light and "T++" represents right-handed polarized light; the circularly polarized light is in the zx plane, and both left-handed and right-handed light are vertically incident on the chiral structural unit 13 with the added hexagonal array structure, and the obtained Figure 8 ;

[0046] See also Fig. 9 , wherein the circularly polarized light is in the zx plane, and both the left and right rotating light are vertically incident on the chiral structural unit 13 (such as Figure 6 As shown) and adding a chiral structural unit 13 of a regular hexagonal array structure (as shown Figure 7 As shown), we get Fig. 9 .

[0047] Depend on Fig. 9 It can be seen that in the CD spectrum of the chiral structural unit 13 without adding the regular hexagonal array structure, the CD at wavelength λ=660nm is 1.5%, and in the CD spectrum of the chiral structural unit 13 with adding the regular hexagonal array structure, the CD at wavelength λ=660nm is 12%. This is because, before adding the regular hexagonal array structure, the chiral structural unit 13 only generates electric dipoles, and the addition of the regular hexagonal array structure changes the current flow direction on the original basic chiral structural unit 13, and a magnetic dipole appears between the metal crescents. Due to the combined effect of the electric dipole and the magnetic dipole, the CD signal is significantly enhanced.

[0048] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention; although the present invention has been described in detail with reference to the aforementioned embodiments, for technicians in this field, they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A nano-crescent array structure for enhancing chiral optics, characterized in that: include: A first substrate (11) and a crescent-shaped metal located on the first substrate (11); wherein the crescent-shaped metal is a chiral structural unit (13) arranged in a hexagonal array on the upper surface of the first substrate (11), and the chiral structural unit (13) comprises: metal crescents (12) with adjustable irregularity and equal spacing between the centers of the crescents.

2. The nano-crescent array structure for enhancing chiral optics according to claim 1, characterized in that: The metal crescents (12) are arranged on the upper surface of the first substrate (11) in a hexagonal array, and the irregularity of the metal crescents (12) is adjustable.

3. The nano-crescent array structure for enhancing chiral optics according to claim 1, characterized in that: The chiral structural units (13) are evenly arranged in both the lateral and longitudinal directions of the first substrate (11).

4. The nano-crescent array structure for enhancing chiral optics according to claim 1, characterized in that: The period of the chiral structural units (13) arranged in the horizontal direction ranges from 400 to 500 nm.

5. The nano-crescent array structure for enhancing chiral optics according to claim 1, characterized in that: The period of the chiral structural units (13) arranged in the vertical direction has a value range of 400√3 to 500√3 nm.

6. The nano-crescent array structure for enhancing chiral optics according to claim 1, characterized in that: The distances between the central points of the chiral structural units (13) are the same.

7. The nano-crescent array structure for enhancing chiral optics according to claim 1, characterized in that: The material of the first substrate (11) is a light-transmitting material.

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