WO2021218200A1

WO2021218200A1 - Conical optical fiber and nanowire combined plasmon probe and working method thereof

Info

Publication number: WO2021218200A1
Application number: PCT/CN2020/138715
Authority: WO
Inventors: 杨树明; 李少博; 程碧瑶; 王飞; 张国锋
Original assignee: 西安交通大学
Priority date: 2020-04-26
Filing date: 2020-12-23
Publication date: 2021-11-04
Also published as: CN111505342A; CN111505342B

Abstract

A conical optical fiber and nanowire combined plasmon probe and a working method thereof. The probe comprises a conical probe fiber core (1), metal film covering layers (2), annular slit plasmon enhancement structures (3) and a nanowire (4). The metal film covering layers (2) are uniformly distributed on the outer surface of the conical probe fiber core (1); the annular slit plasmon enhancement structures (3) are etched on the metal film covering layers (2); and the nanowire (4) grows or is assembled at the needle point position of the metal film covering layers (2). By means of the plasmon enhancement structures (3), larger local field enhancement can be achieved at the needle point, a higher resolution and signal detection sensitivity are achieved, and in addition, surface and high-aspect-ratio complex three-dimensional structure morphology and optical information measurement can be achieved in combination with the structure of the large-length-diameter-ratio nanowire (4). The present invention has wide application prospects in fields such as nanometer extreme processing, spectrum analysis, and super-resolution imaging.

Description

Plasma probe with tapered optical fiber combined with nanowire and its working method

Technical field

The invention belongs to the fields of nano extreme processing, spectral analysis, super-resolution imaging and the like, and particularly relates to a plasmon probe combining a tapered optical fiber with a nanowire and a working method thereof.

Background technique

Scanning near-field optical microscope can realize optical imaging and chemical composition verification, and can break through the optical diffraction limit, realize nanometer resolution processing and measurement, and is widely used in near-field Raman detection, near-field super-resolution imaging and near-field optical processing And other fields. The resolution of the scanning near-field optical microscope depends on the near-field probe technology, the most commonly used are aperture probes and non-porous probes. The smaller cone angle and aperture size of the aperture probe results in a smaller light transmission rate, weak detection signal, and limited resolution capability, generally 50 nm-100 nm. The resolving power of the non-porous probe is determined by its tip diameter, which can reach 10 nm. However, non-porous near-field probes are generally externally directly illuminated, which will introduce a large background signal and require the use of complex interference and phase-locking techniques. In order to eliminate the background signal and retain the nanometer-level resolution capability, plasmon probes have been developed in recent years, which stimulate the propagation of surface plasmons by etching a specific structure on the traditional probe to achieve nano-focusing at the tip of the probe. However, the weak local light field of the existing plasmon probe tip makes it limited in super-resolution measurement and super-diffraction processing; and it can only measure the optical and topographic information of the sample surface. The measurement of complex three-dimensional nanostructures with high aspect ratio is limited.

technical problem

In order to solve the problems in the prior art, the present invention proposes a tapered fiber combined nanowire plasmon probe and its working method. The present invention can achieve greater local field enhancement at the tip of the needle and has higher resolution. Rate and signal detection sensitivity, at the same time, it can realize surface and high aspect ratio complex three-dimensional structure topography and optical information measurement.

Technical solutions

In order to achieve the above objective, the solution provided by the present invention is as follows:

A plasmon probe with a tapered optical fiber combined with a nanowire, comprising a tapered probe core, a metal film covering layer and a nanowire. The metal film covering layer is evenly distributed on the outer surface of the tapered probe core. The wire is arranged at the needle tip position of the metal film covering layer; the surface of the metal film covering layer is provided with a plurality of annular slit plasmon enhancement structures, and the plurality of annular slit plasmon enhancement structures can form resonance interference enhancement.

Preferably, the shape of the tapered probe core is a cone, the cone angle is 20°-40°, and the diameter of the cone tip is 25 nm-100 nm.

Preferably, the material of the metal thin film covering layer is gold, silver or aluminum, and the thickness is 40nm-100nm.

Preferably, the ring-shaped slit plasmon enhancement structure is a groove structure, the groove structure extends from the surface of the metal film covering layer to the surface of the tapered probe core, and the groove structure runs along the tapered probe core.的axial direction extension.

Preferably, the width of the ring-shaped slit plasmon enhancement structure is 50 nm to 150 nm.

Preferably, the nanowire material is gold or silver or carbon nanotubes.

Preferably, the diameter of the nanowire is 2 nm to 50 nm, and the length is 20 nm to 500 nm.

Preferably, the nanowires are grown or assembled at the tip of the metal film covering layer.

The working method of the tapered optical fiber combined with the nanowire plasmon probe of the present invention includes the following processes:

When the tapered fiber combined with the nanowire plasmon probe is in working condition, the fiber radial waveguide mode propagates in the core of the tapered probe, and the wave vector matches to excite the surface plasmon to propagate on the outer surface of the metal film coating. At the same time, the ring-shaped slit plasmon enhancement structure forms resonant interference to enhance the local light field of the surface plasmon, and then the nanowire surface plasmon propagation is excited by the butt coupling method to form a locally enhanced surface at the lower end of the nanowire Nano-scale light field.

Beneficial effect

Compared with the prior art, the present invention has the following beneficial effects:

The tapered fiber combined with nanowire plasmon probe of the present invention has: (1) The tip local field optical field strength: the radial waveguide mode excites the surface plasmon through the wave vector matching condition, and at the same time, it is formed by the annular slit, etc. The excimer-enhancing structure forms resonance interference, which can increase the electromagnetic field density and generate a large local optical field at the tip of the needle. (2) High resolution: The topography and optical information measurement are carried out by nanowires with extremely small diameters. The resolution of the optical field and topography depends on the diameter of the nanowires, and a resolution of 10 nm can be achieved. (3) Able to realize the measurement of complex three-dimensional structures with high aspect ratio: grow or assemble high aspect ratio nanowire structures at the tip of the tapered fiber structure, enabling complex three-dimensional measurements of surface and high aspect ratios, and measurement of extremely small diameter nanowires The environmental impact is small, suitable for small disturbance measurement.

Description of the drawings

FIG. 1 is a schematic diagram of the XZ plane of the plasmon probe with tapered optical fiber combined with nanowire according to the present invention;

2 is a schematic diagram of the XY plane of the plasmon probe with tapered fiber combined with nanowire according to the present invention;

In the figure: 1 is the tapered probe core, 2 is the metal film covering layer, 3 is the ring-shaped slit plasmon enhancement structure, 4 is the nanowire, and 5 is the fiber radial waveguide mode.

Embodiments of the present invention

Hereinafter, the present invention will be explained clearly and specifically with reference to the accompanying drawings and specific implementation methods.

1 and 2, the tapered optical fiber combined with nanowire plasmon probe of the present invention includes a tapered probe core 1, a metal thin film cover layer 2, a ring-shaped slit plasmon enhancement structure 3, and a nanowire Line 4. The metal film covering layer 2 is evenly distributed on the outer surface of the tapered probe core 1, and a number of annular slit plasmon enhancement structures 3 are opened (which can be opened by etching) on the metal film covering layer 2. The nanowire 4 is grown or assembled at the needle tip position of the metal film covering layer 2, and several annular slit plasmon enhancement structures 3 can form a resonance interference enhancement effect. 1 and 2, in the present invention, the annular slit plasmon enhancement structure 3 is a groove structure, and the groove structure extends from the surface of the metal film covering layer 2 to the surface of the tapered probe core 1. The groove structure extends along the axial direction of the tapered probe core 1. For example, taking the orientation shown in FIG. 1 as an example, the annular slit plasmon enhancement structure 3 is arranged in the up and down direction.

When the plasmon probe of the tapered fiber combined with the nanowire of the present invention is in the working state, the fiber radial waveguide mode 5 is coupled to the tapered probe core 1 and propagates in it, and the surface plasmon is excited by the wave vector matching condition. The excimer propagates on the outer surface of the metal film covering layer 2, and at the same time, the specially designed annular slit plasmon enhancement structure 3 forms resonance interference to further enhance the surface plasmon local light field. With the tapered probe With the decrease of the radius, the surface plasmons gather at the tip of the tapered probe and generate a great electric field density. Then the surface plasmons of the nanowire 4 are excited to propagate through the butt coupling method, which can form a localization at the lower end of the nanowire 4 Field-enhanced nano-scale light field. The nano-locally enhanced light field can be used for super-resolution imaging, spectral analysis and super-diffraction processing, and the nanowires with high aspect ratio can be applied to the measurement of complex three-dimensional nanostructures with small disturbance and high aspect ratio.

As a preferred embodiment of the present invention, referring to Fig. 1, the tapered probe core 1 is etched and processed by bare optical fiber, the shape is a cone, the cone angle is 20°~40°, and the cone tip diameter is 25 nm~ 100 nm. .

As a preferred embodiment of the present invention, referring to Fig. 1, the metal film covering layer 2 is made of gold, silver or aluminum, uniformly covering the outer surface of the tapered probe core to form a non-porous probe. The thickness of the covering layer is 40 nm ~ 100 nm.

As a preferred embodiment of the present invention, referring to Figures 1 and 2, the ring-shaped slit plasmon-enhancing structure 3 is etched on the metal film cover layer 2, and the etching direction is parallel to the axis direction of the tapered probe core 1, and The etching depth is 20 nm ~ 100 nm, the etching width is 50 nm ~ 150 nm, and the ring-shaped slit plasmon enhanced structure 3 is coaxial with the tapered probe core 1.

As a preferred embodiment of the present invention, referring to FIG. 1 and FIG. 2, the nanowire 4 is made of gold, silver or carbon nanotubes, which are grown or assembled on the needle tip of the metal film covering layer 2.

As a preferred embodiment of the present invention, the nanowire 4 has a diameter of 2 nm to 50 nm and a length of 20 nm to 500 nm.

Example

The structure of the novel plasmon probe of the tapered fiber combined with the nanowire in this embodiment is shown in Figure 1 and Figure 2. The core of the tapered probe is formed by chemical wet etching, and the cone angle is 32° , The cone tip diameter is 30 nm; the metal film covering layer 2 is made of gold (Au) and the thickness is 80 nm; the annular slit plasmon enhanced structure 3 is completely etched, the etching depth is 80 nm, and the etching width is 100 nm ; The nanowire 4 is made of carbon nanotubes with a diameter of 10 nm and a length of 100 nm, assembled at the tip of the metal film covering layer 2.

Radial light with a wavelength of 632.8 nm is coupled to the tapered probe core 1 and propagates in its intrinsic radial waveguide mode 5. The surface plasmon is excited by the wave vector matching condition to propagate on the outer surface of the metal film covering layer 2. The specially designed annular slit plasmon enhancement structure 3 forms a resonance interference enhancement effect, which further enhances the local optical field of the surface plasmon. As the radius of the cone probe decreases, the surface plasmon increases The position of the tip of the tapered probe gathers and generates a great electric field density, and then the surface plasmon propagation of the nanowire 4 is excited by the butt coupling method, and a locally enhanced nano-scale light field can be formed at the lower end of the nanowire 4.

When performing super-resolution imaging and spectral analysis, the nanowire 4 is penetrated into a small disturbance measurement environment or a complex three-dimensional structure with high aspect ratio. By controlling the height of the needle tip in the Z direction, the local enhanced light field of the nanowire 4 needle tip is coupled with the sample , And then the signal with the near-field optical or composition information of the sample can be collected by the external lens to the photodetector; the signal can also be reverse-coupled into the optical fiber by the nanowire 4, the metal film cover layer 2 and the tapered probe core 1 collect. At the same time, the morphology information of the sample can be restored by extracting the mechanical signal of the detection nanowire 4.

When performing super-diffraction processing, the nanowire 4 needle tip local enhanced light field can enhance the interaction between the sample and the needle tip light field. By controlling the height of the needle tip in the Z direction, the material can be processed by the needle tip local light field while monitoring the probe Z Orientation position and scanning operation of the probe can realize nano-scale processing of complex patterns of the sample.

Claims

A plasmon probe with a tapered optical fiber combined with a nanowire, which is characterized in that it comprises a tapered probe core (1), a metal film covering layer (2) and a nanowire (4), and a metal film covering layer ( 2) Evenly distributed on the outer surface of the tapered probe core (1), the nanowires (4) are arranged at the needle tip position of the metal film covering layer (2); the surface of the metal film covering layer (2) is provided with a number of annular slits, etc. The ion-enhanced structure (3) and several ring-shaped slit plasmon-enhanced structures (3) can form resonance interference enhancement.
The tapered optical fiber combined with nanowire plasmon probe according to claim 1, wherein the shape of the tapered probe core (1) is a cone with a cone angle of 20° ~40°, the diameter of the cone tip is 25 nm to 100 nm.
The tapered optical fiber combined with nanowire plasmon probe according to claim 1, characterized in that the material of the metal film covering layer (2) is gold, silver or aluminum, and the thickness is 40nm-100nm .
The tapered optical fiber combined with nanowire plasmon probe according to claim 1, wherein the ring-shaped slit plasmon enhancement structure (3) is a groove structure, and the groove structure is made of a metal film The surface of the covering layer (2) extends to the surface of the tapered probe core (1), and the groove structure extends along the axial direction of the tapered probe core (1).
The tapered fiber combined nanowire plasmon probe according to claim 1 or 4, wherein the width of the ring-shaped slit plasmon enhancement structure (3) is 50 nm to 150 nm.
The tapered fiber combined nanowire plasmon probe according to claim 1, wherein the material of the nanowire (4) is gold, silver or carbon nanotubes.
The tapered fiber combined nanowire plasmon probe according to claim 1 or 6, wherein the nanowire (4) has a diameter of 2nm-50nm and a length of 20nm-500nm.
The tapered optical fiber combined with nanowire plasmon probe according to claim 1, wherein the nanowire (4) is grown or assembled at the tip of the metal film covering layer (2).
The working method of the tapered fiber combined nanowire plasmon probe according to any one of claims 1-8, characterized in that it comprises the following process:

When the tapered fiber combined with the nanowire plasmon probe is in the working state, the fiber radial waveguide mode (5) propagates in the tapered probe core (1), and the wave vector matches to excite the surface plasmon in the metal The film cover layer (2) spreads on the outer surface, and the ring-shaped slit plasmon enhancement structure (3) forms resonance interference to enhance the surface plasmon local light field, and then the surface of the nanowire (4) is excited by the butt coupling method The plasmon propagates and forms a locally enhanced nano-scale light field at the lower end of the nanowire (4).