A micro-nanostructure with tunable circular dichroism

Abstract

The present invention relates to the technical field of circular dichroism application, and specifically to a micro-nano structure with adjustable circular dichroism, comprising a substrate, a noble metal layer, a first carbon nanotube strip array, a first electrode, and a gate. When applied, the gate and the first electrode are connected to an external circuit to change the gate voltage of the first carbon nanotube strip, thereby changing the effective dielectric constant of the first carbon nanotube strip, and then changing the dielectric environment on the first parallel arm, changing the chirality of the U-shaped structure, and thus realizing the circular dichroism regulation of the U-shaped structure. In the present invention, by adjusting the voltage between the first electrode and the gate, the dielectric environment at the first parallel arm can be conveniently adjusted, and then the circular dichroism can be regulated, and the regulation is convenient, flexible, and has a fast response speed.

Description

Technical Field

[0001] The invention relates to the technical field of circular dichroism application, and in particular to a micro-nano structure with adjustable circular dichroism. Background Art

[0002] The structure itself and its mirror image cannot overlap is called a chiral structure. Circular dichroism refers to the difference in the degree of absorption of left-handed circularly polarized light and right-handed circularly polarized light. The relationship between the absorption degree and the wavelength is called circular dichroism, which is a spectroscopic method for measuring the asymmetric structure of molecules.

[0003] The study found that naturally existing chiral structures have relatively weak circular dichroism, and metals have a relatively strong interaction with light, so the experimenters designed some metal nanostructures to obtain larger circular dichroism. When the metal nanostructure is prepared, its circular dichroism is fixed.

[0004] In order to regulate the chirality of metal nanostructures, researchers have proposed a method for applying ambient temperature to change the circular dichroism of micro-nanostructures. For example, invention patent CN108761850A discloses an optical structure with adjustable circular dichroism and its adjustment method. The optical structure is composed of a plurality of identical periodic units combined in a rectangular periodic array, and the periodic unit includes a first rectangular bar, a second rectangular bar, a third rectangular bar and a fourth rectangular bar, one end of the third rectangular bar is connected to the first rectangular bar, and the other end is connected to the second rectangular bar, one end of the fourth rectangular bar is connected to the first rectangular bar, and the other end is connected to the second rectangular bar, the first rectangular bar, the second rectangular bar and the third rectangular bar are made of precious metal materials, and the fourth rectangular bar is made of VO2 material. By adjusting the ambient temperature, VO2 obtains different phases, produces different absorption for different incident light, and obtains different circular dichroism for the incident light, thereby realizing the adjustment of the fixed mode of circular dichroism of the optical structure of the embodiment of the present application. However, the effect of ambient temperature on changing the refractive index of VO2 is poor, resulting in slow response speed and inflexible regulation during circular dichroism regulation. Summary of the invention

[0005] To solve the above problems, the present invention provides a micro-nano structure with adjustable circular dichroism, including a substrate, a noble metal layer, a first carbon nanotube strip array, a first electrode, and a gate; the noble metal layer is arranged on the upper surface of the substrate, the gate is in a sheet shape, and the gate is arranged on the lower surface of the substrate. The noble metal layer includes a periodically arranged U-shaped structure, the period is a rectangular period, the U-shaped structure includes a first parallel arm, a second parallel arm, and a connecting arm, the first parallel arm and the second parallel arm are parallel, and the first parallel arm and the second parallel arm are arranged along the periodic direction, the first carbon nanotube strip array includes a first carbon nanotube strip arranged in a one-dimensional periodic manner, the first carbon nanotube strip covers the first parallel arm, the first electrode is placed on one side of the upper surface of the substrate, the first electrode is in a strip shape, the direction of the strip is along the periodic direction, and one end of the first carbon nanotube strip is connected to the first electrode.

[0006] Furthermore, the lengths of the first parallel arm and the second parallel arm are not equal.

[0007] Furthermore, the first carbon nanotube strip includes two carbon nanotubes, and the two carbon nanotubes are parallel.

[0008] Furthermore, the distance between two carbon nanotubes is less than 10 nanometers.

[0009] Furthermore, the two carbon nanotubes are doped with nitric acid.

[0010] Furthermore, it also includes a second carbon nanotube strip array and a second electrode, the second carbon nanotube strip array includes second carbon nanotube strips arranged in a one-dimensional periodic manner, the second carbon nanotube strips cover the second parallel arms, the second electrode is placed on the opposite side of the first electrode on the upper surface of the substrate, the second electrode is in a strip shape, the second electrode is parallel to the first electrode, and one end of the second carbon nanotube strip is connected to the second electrode.

[0011] Furthermore, a gap is provided on the connecting arm.

[0012] Furthermore, the width of the gap is less than 40 nanometers.

[0013] Furthermore, the material of the noble metal layer is gold or silver.

[0014] Furthermore, the material of the substrate is an insulating material.

[0015] Beneficial effects of the invention: The invention provides a micro-nano structure with adjustable circular dichroism, comprising a substrate, a noble metal layer, a first carbon nanotube strip array, a first electrode, and a gate; the noble metal layer is arranged on the upper surface of the substrate, the gate is in the shape of a sheet, the gate is arranged on the lower surface of the substrate, the noble metal layer comprises a periodically arranged U-shaped structure, the period is a rectangular period, the U-shaped structure comprises a first parallel arm, a second parallel arm, and a connecting arm, the first parallel arm and the second parallel arm are parallel, the first parallel arm and the second parallel arm are arranged along the periodic direction, the first carbon nanotube strip array comprises a first carbon nanotube strip arranged in a one-dimensional periodic manner, the first carbon nanotube strip covers the first parallel arm, the first electrode is placed on one side of the upper surface of the substrate, the first electrode is in the shape of a strip, the direction of the strip is along the periodic direction, and one end of the first carbon nanotube strip is connected to the first electrode. When used, the gate and the first electrode are connected to an external circuit, the gate voltage of the first carbon nanotube strip is changed, thereby changing the effective dielectric constant of the first carbon nanotube strip, thereby changing the dielectric environment on the first parallel arm, changing the chirality of the U-shaped structure, and thus regulating the circular dichroism of the U-shaped structure. In the present invention, by adjusting the voltage between the first electrode and the gate, the dielectric environment at the first parallel arm can be conveniently adjusted, thereby adjusting the circular dichroism, and the adjustment is convenient, flexible and has a fast response speed.

[0016] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a micro-nanostructure with tunable circular dichroism.

[0018] Figure 2 This is a schematic diagram of another micro-nanostructure with tunable circular dichroism.

[0019] In the figure: 1, substrate; 2, U-shaped structure; 21, first parallel arm; 22, second parallel arm; 31, first carbon nanotube strip; 32, second carbon nanotube strip; 41, first electrode; 42, second electrode; 5, gap. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0021] Example 1

[0022] The present invention provides a micro-nanostructure with adjustable circular dichroism. Figure 1 As shown, the micro-nano structure with adjustable circular dichroism includes a substrate 1, a noble metal layer, a first carbon nanotube strip array, a first electrode 41, and a gate.

[0023] The noble metal layer is arranged on the upper surface of the substrate 1. The material of the noble metal layer is gold or silver. The material of the substrate 1 is an insulating material. The gate is in the shape of a sheet and is arranged on the lower surface of the substrate 1. On the one hand, the substrate 1 is used to support the noble metal layer; on the other hand, the substrate 1 separates the gate and the noble metal layer. The noble metal layer includes a periodically arranged U-shaped structure 2, and the period is a rectangular period. The U-shaped structure 2 includes a first parallel arm 21, a second parallel arm 22, and a connecting arm. The first parallel arm 21 and the second parallel arm 22 are parallel, and the first parallel arm 21 and the second parallel arm 22 are arranged along the periodic direction. Figure 1 In the embodiment, the first parallel arm 21 and the second parallel arm 22 are in the vertical direction, and the connecting arm is in the horizontal direction. The rectangular period of the U-shaped structure 2 is in the horizontal direction and the vertical direction.

[0024] The first carbon nanotube strip array includes first carbon nanotube strips 31 arranged in a one-dimensional periodic manner. The first carbon nanotube strips 31 cover the first parallel arms 21. The first electrode 41 is disposed on one side of the upper surface of the substrate 1. The first electrode 1 is in a strip shape, and the direction of the strip is along the periodic direction. One end of the first carbon nanotube strip 31 is connected to the first electrode 41. Figure 1In the embodiment, the period of the first carbon nanotube strip array is along the horizontal direction, and the first carbon nanotube strip 31 is along the vertical direction. The first carbon nanotube strip 31 is arranged on a plurality of first parallel arms 21 in the vertical direction, and the width of the first carbon nanotube strip 31 is smaller than the width of the first parallel arm 21, so as to facilitate the arrangement of the first carbon nanotube strip 31. The first electrode 41 is arranged on the upper side of the substrate 1, and the first electrode 41 is along the horizontal direction, and the direction of the first electrode 41 is perpendicular to the direction of the first carbon nanotube strip 31.

[0025] When used, the gate and the first electrode 41 are connected to an external circuit to change the gate voltage of the first carbon nanotube strip 31, thereby changing the effective dielectric constant of the first carbon nanotube strip 31, and then changing the dielectric environment on the first parallel arm 21, changing the chirality of the U-shaped structure 2, and thus realizing the circular dichroism regulation of the U-shaped structure 2. In the present invention, by adjusting the voltage between the first electrode 41 and the gate, the dielectric environment at the first parallel arm 21 can be conveniently adjusted, and then the circular dichroism can be regulated, and the regulation is convenient, flexible, and has a fast response speed.

[0026] Generally, if the circular dichroism signal of micro-nanostructure is to be regulated, it is necessary to re-prepare metal structures with different parameters to achieve the purpose of regulation. However, this device can achieve the purpose of regulating and enhancing the circular dichroism signal by controlling the bias voltage of carbon nanotubes. It greatly saves material and time costs. Since the change of bias voltage is reversible, it can be regulated many times and reused.

[0027] In addition, it should be noted that when light is irradiated onto a nanostructure, there is a coupling effect between the free electrons in the nanostructure and the light. This electromagnetic resonance mode localized on the surface of the nanostructure is called a surface plasmon. The method for measuring circular dichroism is: first irradiate with left-handed circularly polarized light and receive a transmission spectrum T--; then irradiate with right-handed circularly polarized light and receive a transmission spectrum T++; the difference between the transmission spectra T-- and T++ is the circular dichroism spectrum.

[0028] Example 2

[0029] On the basis of Example 1, Figure 1 As shown, the lengths of the first parallel arm 21 and the second parallel arm 22 are not equal. Furthermore, the length of the first parallel arm 21 is greater than the length of the second parallel arm 22. In this way, when a gate voltage is applied to the first carbon nanotube strip 31, the refractive index of the environment near the first parallel arm 21 is increased, so that the resonance wavelength of the first parallel arm 21 is further red-shifted, thereby further increasing the asymmetry or chirality of the U-shaped structure 2. Therefore, the change of the gate voltage can further regulate the chirality of the U-shaped structure 2.

[0030] Example 3

[0031] On the basis of Example 2, the first carbon nanotube strip 31 includes two carbon nanotubes, the two carbon nanotubes are parallel, and the distance between the two carbon nanotubes is less than 10 nanometers. In this way, not only coupling occurs between a single carbon nanotube and the first parallel arm 21, but also coupling occurs between the two carbon nanotubes. Therefore, a strong electric field aggregation is formed between the two carbon nanotubes and the first parallel arm 21. These strong electric field aggregations change the environment around the first parallel arm 21 more. Therefore, when the gate voltage changes, the environment around the first parallel arm 21 changes more, thereby achieving more obvious U-shaped structure 2 chirality regulation.

[0032] Example 4

[0033] On the basis of Example 3, nitric acid is doped on the two carbon nanotubes. In practice, nitric acid can be doped on the two carbon nanotubes by evaporating nitric acid in a closed container. For the carbon nanotubes doped with nitric acid, when the gate voltage changes, the degree of binding between the carbon nanotubes and the nitric acid thereon is also changed, thereby further changing the dielectric properties of the carbon nanotube / nitric acid composite structure, thereby further changing the dielectric environment around the first parallel arm 21, thereby achieving a greater degree of regulation of the chirality of the U-shaped structure 2.

[0034] Example 5

[0035] On the basis of Example 4, Figure 2 As shown, it also includes a second carbon nanotube strip array and a second electrode 42. The second carbon nanotube strip array includes second carbon nanotube strips 32 arranged in a one-dimensional periodic manner. The second carbon nanotube strips 32 cover the second parallel arms 22. The second electrode 42 is placed on the opposite side of the first electrode 41 on the upper surface of the substrate 1. The second electrode 42 is in a strip shape and is parallel to the first electrode 41. One end of the second carbon nanotube strip 32 is connected to the second electrode 42. Figure 2 In the embodiment, the period of the second carbon nanotube strip array is along the horizontal direction, and the second carbon nanotube strip 32 is along the vertical direction. The second electrode 42 is along the horizontal direction, and the second electrode 42 is connected to the second carbon nanotube strip 32. The width of the second carbon nanotube strip 32 is smaller than the width of the second parallel arm 22, so as to facilitate the determination that the second carbon nanotube strip 32 is placed on the second parallel arm 22. When applied, the second electrode 42 is connected to another power supply, that is, different voltages are set between the second electrode 42 and the gate. The first carbon nanotube strip 31 and the second carbon nanotube strip 32 are distributed to regulate the dielectric environment around the first parallel arm 21 and the second parallel arm 22, thereby achieving more flexible regulation of the chirality of the U-shaped structure 2.

[0036] Example 6

[0037] On the basis of Example 5, a gap 5 is provided on the connecting arm. In this way, the first parallel arm 21 and the second parallel arm 22 are disconnected, and the charge on the first parallel arm 21 will not be conducted to the second parallel arm 22. Therefore, the charge vibration on the first parallel arm 21 and the charge vibration on the second parallel arm 22 can be independently regulated, thereby increasing the phase difference between the two charge vibrations, thereby achieving more flexible chirality regulation of the U-shaped structure 2.

[0038] In practical applications, the gate voltages on the first carbon nanotube strip 31 and the second carbon nanotube strip 32 can be set to be opposite, so as to achieve a greater degree of chirality control of the U-shaped structure 2.

[0039] Furthermore, the width of the gap is less than 40 nanometers so as to enhance the coupling between the charge vibrations on the first parallel arm 21 and the second parallel arm 22 .

[0040] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A micro-nanostructure with adjustable circular dichroism, characterized in that: It includes a substrate, a noble metal layer, a first carbon nanotube strip array, a first electrode, and a gate; the noble metal layer is arranged on the upper surface of the substrate, the gate is in a sheet shape, and the gate is arranged on the lower surface of the substrate. The noble metal layer includes a periodically arranged U-shaped structure, the period is a rectangular period, the U-shaped structure includes a first parallel arm, a second parallel arm, and a connecting arm, the first parallel arm and the second parallel arm are parallel, and the first parallel arm and the second parallel arm are arranged along the periodic direction. The first carbon nanotube strip array includes a first carbon nanotube strip arranged in a one-dimensional period, the first carbon nanotube strip covers the first parallel arm, the first electrode is placed on one side of the upper surface of the substrate, the first electrode is in a strip shape, and the direction of the strip is along the periodic direction. One end of the first carbon nanotube strip is connected to the first electrode, and the gate and the first electrode are connected to an external circuit to change the gate voltage of the first carbon nanotube strip.

2. The micro-nanostructure with adjustable circular dichroism according to claim 1, characterized in that: The lengths of the first parallel arm and the second parallel arm are not equal.

3. The micro-nanostructure with adjustable circular dichroism according to claim 2, characterized in that: The first carbon nanotube strip includes two carbon nanotubes, and the two carbon nanotubes are parallel.

4. The micro-nanostructure with adjustable circular dichroism according to claim 3, characterized in that: The distance between the two carbon nanotubes is less than 10 nanometers.

5. The micro-nanostructure with adjustable circular dichroism according to claim 4, characterized in that: The two carbon nanotubes are doped with nitric acid.

6. The micro-nanostructure with adjustable circular dichroism according to any one of claims 1 to 5, characterized in that: The material of the noble metal layer is gold or silver.

7. The micro-nanostructure with adjustable circular dichroism according to claim 6, characterized in that: The material of the substrate is insulating material.

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