WO2018038427A1

WO2018038427A1 - Far-field plasmonic lens and far-field plasmonic lens assembly

Info

Publication number: WO2018038427A1
Application number: PCT/KR2017/008594
Authority: WO
Inventors: 김승현; 김건희; 김이종
Original assignee: 한국기초과학지원연구원
Priority date: 2016-08-23
Filing date: 2017-08-09
Publication date: 2018-03-01
Also published as: KR101810846B1

Abstract

A far-field plasmonic lens according to the present invention comprises: a base substrate having a positive dielectric constant; and a nano structure array having a negative dielectric constant, and having a predetermined cross-sectional area and extending in a lengthwise direction at the upper part of the base substrate, wherein the nano structure array comprises a first nano structure formed at a central position, and a plurality of second nano structures arranged at intervals around the first nano structure.

Description

Far-field plasmonic lens and far-field plasmonic lens assembly

The present invention relates to a visible light lens that can be applied to an optical microscope, and more particularly, a far field that can measure the shape information below the diffraction limit of light using surface plasmon resonance induced by the metal nanostructure. (far-field) plasmonic lenses and far-field plasmonic lens assemblies.

Optical microscopes are an important tool for microstructure analysis, and are widely used in basic sciences such as physics, chemistry, biology, and medicine. Here, the general optical lens applied to the optical microscope cannot distinguish an object having a size smaller than the half wavelength of the applied wavelength due to the diffraction limit of light, so that the resolution in the visible region is 200 to 300 nm. The level is recognized as a limit.

As a technique for overcoming the diffraction limit of light, research on the surface plasmon resonance (SRP) phenomenon is emerging.

Surface plasmon resonance (SRP) is a phenomenon in which surface plasmon present at the interface between metal and dielectric resonates with incident light. (Surface Plasmon Polaritons, SPPs) are formed, which means that they exhibit an electromagnetic field that decreases exponentially in the vertical direction from the interface.

However, research on the surface plasmon resonance phenomenon is more active in the field of biosensor than in the field of optical microscope, and many prior arts including Korean Patent No. 1,621,437 (plasma sensor combined with multi-layered thin film structure and nano structure). Focuses on the design of plasmonic sensors to measure biomolecular properties (eg refractive index or concentration change) using SPR phenomena.

Currently, the design techniques of plasmonic lenses applicable to optical microscopes have not shown remarkable achievements, and some of the proposed plasmonic lenses to date have a complicated design structure, especially in near-field mode in the visible region. Limited. Accordingly, there is a need to develop a novel plasmonic lens having a simple design structure and increasing focal length to operate in a far-field mode in the visible light region.

Accordingly, the present invention has been made to solve the above-described problem, and using a surface plasmon resonance phenomenon, a far-field plasmonic lens for visible light that can measure the shape information below the diffraction limit of light It is to provide.

The present invention also provides a far-field far-field for visible light that can greatly improve focal length and spatial focus rate through an optimal design structure of a periodically arranged nanostructure formed on the base substrate and the base substrate. field) to provide a plasmonic lens.

In addition, in the present invention, a plurality of far-field plasmonic lenses having different resonance wavelengths and focusing distances are arranged, so that a far-field plasmonic lens can be easily used by changing the plasmonic lens as needed. To provide an assembly.

Other objects of the present invention will become more apparent through the preferred embodiments described below.

According to an aspect of the present invention, a far-field plasmonic lens includes: a base substrate having a positive dielectric constant; And a nanostructure array having a negative dielectric constant and extending in a longitudinal direction with a predetermined cross-sectional area on the base substrate, wherein the nanostructure array comprises a first nanostructure formed at a central position; It includes a plurality of second nanostructures spaced apart about one nanostructure.

In an embodiment, the plurality of second nanostructures may be spaced apart at regular intervals about the first nanostructure.

In example embodiments, the second nanostructure may be formed on an upper surface of the base substrate, and the first nanostructure may be formed by inserting at least a portion of the first nanostructure in a vertical lower direction based on the upper surface of the base substrate. .

Here, the first nanostructure may be formed to have a vertical length higher than the vertical length of the second nanostructure with respect to the upper surface of the base substrate.

In one embodiment, the nanostructure array may include at least two first nanostructures.

In one embodiment, the base substrate is formed of a dielectric, the first and second nanostructures may be formed of a metal.

In some embodiments, the first and second nanostructures may be formed of any one material of gold (Au), silver (Ag), and aluminum (Al).

In one embodiment, the base substrate may be formed of a transparent material.

In one embodiment, the base substrate is formed in a plane of a circular or oval shape of the top, it may be formed to have a convex three-dimensional shape in the lower direction.

According to another aspect of the invention, the far-field plasmonic lens assembly comprises a plurality of far-field plasmonic lenses spaced apart; And a mounting unit configured to fix the spaced apart plurality of far-field plasmonic lenses, wherein each of the plurality of far-field plasmonic lenses has a positive dielectric constant; And a nanostructure array having a negative dielectric constant and extending in a longitudinal direction with a predetermined cross-sectional area on the base substrate, wherein the nanostructure array comprises a first nanostructure formed at a central position; The first nanostructure includes a plurality of second nanostructures that are spaced apart at regular intervals.

Here, each of the plurality of far-field plasmonic lenses may be designed different from each other at least one of the shape of the base substrate, the refractive index of the base substrate, and the arrangement period of the second nanostructure.

The present invention can be applied to an optical microscope for visible light to measure shape information below the diffraction limit of light.

In addition, the present invention can significantly improve the focal length and the spatial focusing rate through the optimal design structure of the periodically arranged nanostructures formed on the base substrate and the base substrate.

In addition, the present invention is arranged a plurality of far-field plasmonic lenses having different resonance wavelengths and focusing distance, so that the plasmonic lens can be easily changed and used as needed.

1 is a cross-sectional view of a far-field plasmonic lens according to the present invention.

2 is a perspective view of a far-field plasmonic lens according to the present invention.

3 is a cross-sectional view of a far-field plasmonic lens according to the present invention.

4 is a cross-sectional view of a far-field plasmonic lens according to an embodiment of the present invention.

5 is a perspective view of a far-field plasmonic lens according to an embodiment of the present invention.

6 is a cross-sectional view of a far-field plasmonic lens according to another embodiment of the present invention.

7 is a cross-sectional view of a far-field plasmonic lens according to another embodiment of the present invention.

8 is a perspective view of a far-field plasmonic lens assembly according to the present invention.

9 is a cross-sectional view of a far-field plasmonic lens assembly according to the present invention.

10 to 16 are reference diagrams for explaining the operation and effects of the far-field plasmonic lens according to the present invention and one embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

The present invention relates to a visible light lens that can be applied to an optical microscope, and more particularly, a far field that can measure the shape information below the diffraction limit of light using surface plasmon resonance induced by the metal nanostructure. (far-field) plasmonic lenses and far-field plasmonic lens assemblies. As described above, the plasmonic lens applicable to the optical microscope is currently limited to the near-field mode because of its complicated design structure and particularly short focal length in the visible light region.

The present inventors have made intensive efforts to solve the above-described problems, and as a result, the nanostructure array having the negative dielectric constant is formed on the base substrate having the positive dielectric constant. It was confirmed that the effect that can significantly increase the distance and at the same time improve the spatial focusing rate, and completed the far-field plasmonic lens according to the present invention.

Hereinafter, a far-field plasmonic lens according to the present invention will be described in detail with reference to the accompanying drawings.

1 to 3 are reference diagrams for explaining the far-field plasmonic lens according to the present invention, and more specifically, FIGS. 1 and 3 are cross-sectional views of the far-field plasmonic lens according to the present invention, and FIG. Is a perspective view of a far-field plasmonic lens according to the present invention.

1 to 3, the far-field plasmonic lens 100 according to the present invention includes a base substrate 110 having a positive dielectric constant and

nanostructure arrays

120 and 130 having a negative dielectric constant. Here, the

nanostructure arrays

120 and 130 include a plurality of

nanostructures

120 and 130 formed to extend in the longitudinal direction with a predetermined cross-sectional area on the base substrate 110.

In an embodiment, the

nanostructure arrays

120 and 130 may be formed of a metal material, and may be formed of any one of gold (Au), silver (Ag), and aluminum (Al). It may be formed of gold (Au).

In one embodiment, the base substrate 110 may be formed of a dielectric. Here, the base substrate 110 may be formed of a transparent material, for example, may be formed of any one material of quartz (SiOx) or glass (glass).

The

nanostructure arrays

120 and 130 include a first nanostructure 120 formed at a central position and a plurality of second nanostructures 130 spaced apart from the first nanostructure 120.

For example, referring to FIGS. 1 and 2, the far-field plasmonic lens 100 includes a flat base substrate 110 and a plurality of nanostructure arrays formed on the base substrate 110, wherein each nano The structures may be spaced apart in parallel to each other, the first nanostructures 120 may be formed at a central position, and the second nanostructures 131 to 136 may be arranged to be spaced in both directions of the first nanostructure 120. .

In some embodiments, the plurality of second nanostructures 130 may be spaced apart from each other by a predetermined period unit L with respect to the first nanostructure 120. More specifically, referring to FIG. 3, the

second nanostructures

131 and 132 are disposed on both sides of the first nanostructure 120 by the same distance, respectively, and then the second nanostructures 133 to 133. 136 may be arranged with the same period (L) in a direction away from the first nanostructure 120, respectively.

In some embodiments, each of the plurality of second nanostructures 131 to 136 may have the same width W and height H, and the first nanostructure 120 may include the second nanostructures 131 to 136. 136 may have a different width W.

On the other hand, Figures 1 to 3 are examples for explaining the far-field plasmonic lens 100 according to the present invention, and are not intended to limit the scope of the present invention, the number, width, It is apparent that the height, length, shape and spacing can be designed differently from the accompanying drawings as required (requirements).

The operation state when the far-field plasmonic lens 100 according to the present invention is applied to an optical microscope will be described.

The far-field plasmonic lens 100 may be positioned between the objective lens and the sample of the optical microscope, and the light source may pass through the objective lens to emit light in the visible region from the top of the far-field plasmonic lens 100 to the downward direction. You can investigate. At this time, surface plasmon polaritone (SPP) due to the coupling of surface plasmon and photons at the interface between the

nanostructure arrays

120 and 130 of the far-field plasmonic lens 100 and the base substrate 110. polariton) may be generated. Here, the SPP can be focused in an area smaller than the limit of diffraction (diffraction limit) of light as it appears in the form of an electromagnetic field. As a result, the light source primarily focused through the objective lens is secondly focused by the plasmonic lens described in the present invention, and the incident light reflected on the sample surface is measured by the detector, so that the shape information of the sample surface is measured. Can be obtained.

The SPP may be focused with a constant focal length in the process of going downward of the base substrate 110, and the focal length may be changed according to the shape or refractive index of the base substrate 110 and may be focused. The resonance wavelength may vary according to the separation period L of the second nanostructure 130 and the refractive index of the base substrate (or the nanostructure).

In the far-field plasmonic lens 100 according to the present invention, focusing wavelengths according to the design of the

nanostructures

120 and 130 will be described in detail. Here, the focusable wavelength is a resonance wavelength capable of representing surface plasmon resonance, and a high field intensity may appear at the focusable wavelength.

10 is a reference diagram for confirming the surface plasmon resonance wavelength. Here, FIG. 10 shows the width W and the height H of the

nanostructures

120 and 130 as 164 nm and 50 nm, and the separation period L of the second nanostructure 130 as 535 nm, respectively. This is the result of computerized transmission of wavelengths by designing the area ratio (ff, fill factor) of nano structure (ideally metal) in all plasmonic lens to 0.3.

Referring to FIG. 10, when the first nanostructure (PS tooth) is not configured in the plasmonic lens and only the second nanostructure 130 is periodically arranged, a decrease in transmittance occurs at wavelengths of about 540 nm and 790 nm. You can see that. Here, the decrease in transmittance at the wavelength of 540 nm is represented by the conversion of the incident photon into surface plasmon due to the generation of SPP at the air-natal interface (AM mode). It can be interpreted that the incident photons are converted into surface plasmons by the generation of SPP at the nano-substrate interface (MS mode).

On the other hand, according to the present invention constitutes a first nanostructure (PS tooth), the second nanostructure 130 is arranged periodically spaced about the first nanostructure 120 (ideally the first nanostructure ( 120 may have a separation distance of half a cycle to a period of the second nanostructure 130), and a decrease in transmittance occurs at wavelengths of about 540 nm (AM mode) and 750 nm (MS mode). It can be seen that a further decrease in transmittance occurs at a wavelength of 650 nm. That is, when the first nanostructure 120 is configured, compared to the case where the first nanostructure 120 is not configured, the resonant wavelength position in the MS mode is shifted to blue and an additional surface plasmon resonance may be exhibited. It can be seen that a resonance wavelength (about 650 nm) may appear.

Each resonance mode (photon-surface plasmon coupling) can be identified by computer simulation. 11 is a reference diagram illustrating an H-Field according to a change in wavelength applied to a far-field plasmonic lens. Referring to FIGS. 11A to 11D, in the 540 nm wavelength (AM mode), a strong H-Field can be identified at the interface between the atmosphere and the nanostructure, and the 650 nm wavelength (coupling mode) and about 750 nm In the wavelength (MS mode), it can be seen that a strong H-Field is displayed while focusing downward. On the other hand, at the wavelength of 1,000 nm rather than the resonance wavelength, the focusing ratio of the H-Field is relatively weak.

That is, according to the far-field plasmonic lens 100 according to the present invention, two ranges of focusable wavelengths may be obtained by configuring the first nanostructure 120.

In the present invention, the focusable wavelength of the far-field plasmonic lens 100 may be changed according to the separation period L of the second nanostructure 130. FIG. 12 is a reference diagram illustrating transmission for each wavelength according to the separation period L of the second nanostructure 130. Referring to FIG. 12, the separation period L of the second nanostructure 130 may be defined as follows. As it gradually increases from 435nm to 635nm

It can be seen that the MS mode (or AM mode) wavelength gradually shifts in red color. That is, the far-field plasmonic lens 100 according to the present invention may change the focusable wavelength as necessary by varying the separation period L of the second nanostructure 130.

Hereinafter, a preferred embodiment of the far-field plasmonic lens according to the present invention will be described in detail with reference to FIGS. 4 to 7. 4, 6 and 7 are cross-sectional views of the far-field plasmonic lens according to an embodiment of the present invention, Figure 5 is a perspective view of the far-field plasmonic lens according to an embodiment of the present invention.

According to a preferred embodiment of the present invention described below, compared to the far-field plasmonic lens 100 described above, it is possible to increase the focusing rate by about 7 times or more and the focusing distance by about 15 μm or more.

In one embodiment, the base substrate 110 may be formed to have a circular or oval planar upper surface, and may have a convex three-dimensional shape in the lower direction. For example, as illustrated in FIGS. 4 and 5, the base substrate 210 of the far-field plasmonic lens 200 may be formed in a hemisphere shape having a circular plane on the top.

FIG. 13 is a reference diagram illustrating an H-Field according to a change in a wavelength and a shape of a base substrate 210 applied to a far-field plasmonic lens 200, and FIG. 14 illustrates field intensity according to an advancing distance of an SPP. It is the reference figure which shows. 13 and 14, when the base substrate 210 is formed as a hemisphere, it can be seen that the electric field focusing rate is increased by about 7 times or more compared with the flat base substrate 210.

Hereinafter, a design structure capable of further improving (approximately 70% or more) the focusing ratio of the far-field plasmonic lens 200 according to the preferred embodiment of the present invention described above with reference to FIGS. 6 and 7 will be described. .

In one embodiment, the second nanostructure 130 is formed on an upper surface of the base substrate 210, and the first nanostructure 320 is at least in a vertical lower direction relative to the upper surface of the base substrate 210. A part may be inserted and formed. For example, as shown in FIG. 6, the first nanostructure 320 may be partially inserted and mounted based on the upper surface of the base substrate 210, unlike the second nanostructure 130.

In one embodiment, the first nanostructure 320 may be formed to have a vertical length higher than the vertical length of the second nanostructure 130 with respect to the upper surface of the base substrate 210. For example, as shown in FIG. 7, the first nanostructure 320 is partially inserted with respect to the upper surface of the base substrate 210 and formed to have a vertical length higher than that of the second nanostructure 130. Can be.

FIG. 15 is a reference diagram illustrating field intensity according to an advancing distance of an SPP. Referring to FIG. 15, when the first nanostructure (Au PS tooth) is inserted by 0.5 μm in the downward direction based on the upper surface of the base substrate 210 and formed by 0.1 μm higher than the second nanostructure 130. In comparison with the case where the first nanostructure (Au PS tooth) is formed at the same height as the second nanostructure 130, the field concentration rate is improved by 11.3% (wavelength 811 nm-MS mode).

Furthermore, when the first nanostructure (Au PS tooth) is inserted by 0.5 μm in the downward direction relative to the upper surface of the base substrate 210 and formed by 0.5 μm higher than the second nanostructure 130, the first nano structure Compared to the case in which the structure (Au tooth) is formed at the same height as the second nanostructure 130, the electric field focusing rate is improved by 71.5% (wavelength 811 nm-MS mode).

That is, in the design of the far-field plasmonic lens 300, the base substrate 210 is designed in a convex three-dimensional shape in the downward direction, and the first nanostructure 320 is based on the upper surface of the base substrate 210. When a part is inserted in the downward direction and designed to have a vertical length higher than that of the second nanostructure 130, the maximum focusing distance and the focusing ratio may be exhibited.

In one embodiment, the far-field plasmonic lens 300 may include at least two first nanostructures 320. Referring to FIG. 16, three first nanostructures (Au PS tooth) are inserted by 0.5 μm in a downward direction with respect to the upper surface of the base substrate 210 and formed by 0.5 μm higher than the second nanostructure 130. In the case of constructing, the intensity and focusing distance of the system is insignificant compared with the case of constructing one first nanostructure (Au PS tooth).

8 and 9, a far-field plasmonic lens assembly according to the present invention will be described. 8 is a perspective view of a far-field plasmonic lens assembly according to the present invention, and FIG. 9 is a cross-sectional view of the far-field plasmonic lens assembly according to the present invention.

8 and 9, the far-field plasmonic lens assembly 400 fixes and supports a plurality of far-field plasmonic lenses 300-1 to 300-3, which are spaced apart, and a plurality of far-field plasmonic lenses. It includes a mounting portion 410. Here, the far-field plasmonic lens may be applied to the far-field plasmonic lens of the various embodiments described above.

In one embodiment, each of the plurality of far-field plasmonic lenses 300-1 to 300-3 may be designed such that at least one of the shape of the base substrate, the refractive index of the base substrate, and the arrangement period of the second nanostructure are different from each other. have. That is, each of the plurality of far-field plasmonic lenses 300-1 to 300-3 may be designed to have different focusing wavelengths or focusing distances, and may be spaced apart from and fixed to one mounting unit 410.

The far-field plasmonic lens assembly 400 according to the present invention may be mounted to an optical microscope, and may be configured such that an appropriate far-field plasmonic lens is applied as necessary through a moving device and a control device configured in the optical microscope.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

Claims

A base substrate having a positive dielectric constant; And

It includes; having a negative dielectric constant, the nanostructure array is formed extending in the longitudinal direction with a predetermined cross-sectional area on the base substrate;

The nanostructure array is

A far-field plasmonic lens comprising a first nanostructure formed at a central position and a plurality of second nanostructures spaced apart from the first nanostructure.
The method of claim 1, wherein the plurality of second nanostructures

Far-field plasmonic lens, characterized in that spaced apart at regular intervals centered on the first nanostructure.
The method of claim 1,

The second nanostructure is formed on the upper surface of the base substrate,

The first nanostructure is far-field plasmonic lens, characterized in that formed by inserting at least a portion in the vertical lower direction relative to the upper surface of the base substrate.
The method of claim 3, wherein the first nanostructure is

Far-field plasmonic lens, characterized in that formed to have a vertical length higher than the vertical length of the second nanostructure with respect to the upper surface of the base substrate.
The method of claim 3 or 4, wherein the nanostructure array is

A far field plasmonic lens comprising at least two first nanostructures.
The method of claim 1,

The base substrate is formed of a dielectric, wherein the first and second nanostructures are formed of a metal, the far-field plasmonic lens.
The method of claim 6, wherein the first and second nanostructures are

Far-field plasmonic lens, characterized in that formed from any one of gold (Au), silver (Ag) and aluminum (Al).
The method of claim 6, wherein the base substrate

Far-field plasmonic lens, characterized in that formed from transparent materials.
The method of claim 1, wherein the base substrate

A far field plasmonic lens, characterized in that the upper portion is formed in a circular or oval plane, and has a convex three-dimensional shape in the lower direction.
In the far field plasmonic lens assembly,

A plurality of far-field plasmonic lenses spaced apart; And

And a mounting unit configured to fix the spaced apart plurality of far-field plasmonic lenses.

Each of the plurality of far-field plasmonic lenses is

A base substrate having a positive dielectric constant; And

And having a negative dielectric constant and having a predetermined cross-sectional area over the base substrate and extending in a longitudinal direction.

The nanostructure array includes a first nanostructure formed at a central position, and the far field plasmonic lens assembly including a plurality of second nanostructures are arranged spaced apart at regular intervals about the first nanostructure.
The method of claim 10, wherein each of the plurality of far-field plasmonic lenses

A far-field plasmonic lens assembly, wherein at least one of the shape of the base substrate, the refractive index of the base substrate, and the arrangement period of the second nanostructures are designed to be different from each other.