CN112327477A - Optical nano focusing method and device - Google Patents
Optical nano focusing method and device Download PDFInfo
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- CN112327477A CN112327477A CN202011279805.6A CN202011279805A CN112327477A CN 112327477 A CN112327477 A CN 112327477A CN 202011279805 A CN202011279805 A CN 202011279805A CN 112327477 A CN112327477 A CN 112327477A
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Abstract
The invention relates to an optical nanometer focusing method and a device, wherein the device comprises the following components: the device comprises a probe, a sample scanning table, a focusing objective lens, a beam splitter, a Raman spectrum acquisition system, a vortex light beam generator, a laser light source and a control system; the method comprises the following steps: s1: preparing a nano structure on the surface of the probe by utilizing a nano processing technology; s2: the probe is coaxially arranged with the focusing objective lens and the beam splitter; s3: emitting a common light beam by using a laser light source, and converting the common light beam into a vortex light beam; s4: focusing the vortex light velocity to generate annularly distributed light spots; s5: irradiating the annular light beam of the focused light beam to the surface of the metal probe, and exciting the surface plasmon wave in a propagation mode after the nano structure on the surface of the probe is irradiated by the annular focused light beam; s6: the surface plasmon wave propagates along the surface of the metal probe and is converged at the probe tip to generate a nanometer focusing light spot. The invention can reduce the effect of conventional diffraction focusing light spots and improve the effect of nanometer focusing light beams.
Description
Technical Field
The invention relates to the field of optical nano focusing, in particular to an optical nano focusing method and device.
Background
The conventional optical system is difficult to realize optical focusing and imaging in a scale below half wavelength under the limit of optical diffraction limit. The limit of optical diffraction limit is broken through, and the realization of nanoscale optical focusing has important application value in the aspects of micro-nano optics, nano manufacturing, detection, imaging and the like. The method for realizing the nanoscale spot focusing by using the metal probe is a common method and is also a basic principle model of a needle-Tip Enhanced Raman Scattering (TERS) technology. The method mainly focuses light beams to a probe tip to excite local surface plasmons by means of a conventional optical focusing means. However, in the method, highly localized surface plasmons are superimposed on conventional diffraction-limited optical focusing, so that a conventional focusing spot with large spatial distribution and a localized surface plasmon field with small spatial distribution exist simultaneously. However, when the method is applied to signal detection, the effects of the two methods cannot be distinguished, and the former method brings adverse effects such as reduction of signal contrast and reduction of imaging quality. Preparing a probe with nanoparticles or fabricating nanostructures on the surface of the probe to excite surface plasmon waves (jpn.j.appl.phys.2016,55,08nb03.nano lett.2018,19, 100-107) of a propagation mode on the surface of the probe can generate a focused light spot in a nanometer scale on the probe tip, but at present, the schemes are only suitable for a tip-enhanced raman scattering system with side illumination or non-transmission illumination and are difficult to adapt to a transmission optical system.
Disclosure of Invention
The invention provides an optical nano focusing method and device for overcoming the defect of poor optical nano focusing effect in the prior art.
The method comprises the following steps:
s1: preparing a nano structure on the surface of the probe by utilizing a nano processing technology;
s2: the probe is coaxially arranged with the focusing objective lens and the beam splitter;
s3: emitting a common light beam by using a laser light source, and converting the common light beam into a vortex light beam;
s4: focusing the vortex light velocity to generate annularly distributed light spots;
s5: irradiating the annular light beam of the focused light beam to the surface of the probe, and exciting the surface plasmon wave in a propagation mode after the nano structure on the surface of the probe is irradiated by the annular focused light beam;
s6: the surface plasmon wave propagates along the surface of the metal probe, and is converged at the probe tip to generate a nanometer focusing light spot of dozens of nanometers or even smaller.
Preferably, the vortex beam in S1 is a vortex beam with a phase topological charge.
Preferably, S1 is specifically: the ordinary light beam is passed through a vortex light beam generator to be converted into a vortex light beam.
Preferably, the center of the annular light spot in S2 is an annular distribution light spot with high intensity around the dark nucleus.
Preferably, S2 is specifically: the vortex light velocity is focused by a focusing objective lens to generate annular distribution light spots.
Preferably, the focused spot of the probe tip is a surface plasmon component; there is no conventional beam diffractive focusing component.
Preferably, the vortex light velocity is focused by the focusing objective lens in S4 to generate a ring-shaped distributed light spot.
The device of the invention comprises: the device comprises a probe, a sample scanning table, a focusing objective lens, a beam splitter, a Raman spectrum acquisition system, a vortex light beam generator, a laser light source and a control system;
the laser light source is used for emitting a common light beam;
the vortex light beam generator is used for converting the common light beam into a vortex light beam;
the focusing objective is used for focusing the vortex light speed to generate an annular distribution light spot;
the beam splitter is used for distinguishing laser light from detection signal light;
the sample scanning table is used for controlling the movement of the sample;
when the probe irradiates the surface of the metal probe with the annular beam of the focused beam, the surface plasmon wave in a propagation mode is excited, the surface plasmon wave propagates along the surface of the metal probe, and the surface plasmon wave is converged at the probe tip to generate a nanometer focusing light spot.
The Raman spectrum system is used for collecting Raman spectrum signals;
the control system and the Raman spectrum system perform bidirectional linkage control to realize sample positioning and spectrum collection.
Preferably, the surface of the probe is provided with a nano structure, so that the excitation of surface plasmons can be realized.
Preferably, the smaller the probe tip size, the better.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that: the vortex phase light beam is used for exciting the annular focusing light beam, so that the influence of the conventional focusing light spot in the central area of the light beam is weakened; the annular light beam acts with a probe with a nano structure, surface plasmon surface waves in a propagation mode are excited on the surface of the probe, and the surface plasmon surface waves are converged at the probe tip to form an enhanced focusing field with a nano scale. The method can effectively weaken the influence of conventional focusing light spots with larger spatial distribution, improve the action of the nano focusing light beams, and is beneficial to improving the signal contrast of the action of the nano light beams, improving the spatial resolution and the like.
Drawings
FIG. 1 is a flow chart of the optical nano-focusing method described in example 1.
Fig. 2 is a schematic view of the optical nano-focusing apparatus according to embodiment 2.
In the figure: the system comprises a probe 1, an annular light beam 2, a sample scanning table 3, a focusing objective 4, a beam splitter 5, a Raman spectrum acquisition system 6, a vortex light beam generator 7, a laser light source 8 and a control system 9.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1:
the present embodiment provides an optical nano-focusing method; as shown in fig. 1, the method comprises the steps of:
s1: preparing a nano structure on the surface of the probe by utilizing a nano processing technology;
s2: the probe is coaxially arranged with the focusing objective lens and the beam splitter;
s3: emitting a common light beam by using a laser light source, and converting the common light beam into a vortex light beam;
s4: focusing the vortex light velocity to generate annularly distributed light spots;
s5: irradiating the annular light beam of the focused light beam to the surface of the probe, and exciting the surface plasmon wave in a propagation mode after the nano structure on the surface of the probe is irradiated by the annular focused light beam;
s6: the surface plasmon wave propagates along the surface of the metal probe, and is converged at the probe tip to generate a nanometer focusing light spot of dozens of nanometers or even smaller.
Wherein, the vortex light beam in the S1 is a vortex light beam with phase topological charge.
S1 specifically includes: the ordinary light beam is passed through a vortex light beam generator to be converted into a vortex light beam.
The center of the annular light spot in S2 is an annular distribution light spot with high peripheral intensity of the dark nucleus.
S2 specifically includes: the vortex light velocity is focused by a focusing objective lens to generate annular distribution light spots.
The focusing light spot of the probe tip is a surface plasmon component; there is no conventional beam diffractive focusing component.
And S4, focusing the vortex light velocity by using a focusing objective lens to generate an annular distribution light spot.
Because the vortex light beam generates annularly distributed light spots after being focused, the light intensity of the focusing center position of the optical system is very weak. In the embodiment, the nano structure is manufactured on the surface of the metal probe, so that the surface plasmon can be excited on the surface of the probe.
In addition, because the metal probe and the optical system are coaxially arranged, the probe tip is mainly a plasmon focusing light spot generated on the surface of the metal, and the focusing light spot of the conventional optical system does not exist, so that the contrast of the nanometer light spot can be greatly improved, and the imaging quality and other advantages can be favorably improved.
Finally, the size of the nanometer focusing light spot in S6 is closely related to the size of the probe tip, the metal probe with smaller tip radius is used to realize the light spot focusing with smaller scale, and the focusing field of the probe tip is mainly surface plasmon component, and there is no diffraction focusing component of the conventional light beam, so that there is only highly localized near field optical component at the probe tip to participate in the imaging process, such as raman imaging, in the aspect of raman signal acquisition, the general optical system collects information in a confocal manner (the acquisition range of the signal is generally equivalent to the diffraction limit size of the conventional light spot), i.e. only acquires the signal near the probe tip, and the annular focusing distribution of the vortex light beam is mainly concentrated in the peripheral area far away from the probe, which can effectively avoid the possibility that the signal generated by the conventional focusing light spot is collected, thus providing signal contrast in the aspect of raman detection imaging, and the imaging resolution is improved.
Example 2:
this embodiment provides an optical nano-focusing method and apparatus, which can implement the method described in embodiment 1.
As shown in fig. 2, the apparatus includes: the device comprises a probe 1, a sample scanning table 3, a focusing objective 4, a beam splitter 5, a Raman spectrum acquisition system 6, a vortex light beam generator 7, a laser light source 8 and a control system 9;
the laser light source 8 is used for emitting a common light beam;
the vortex light beam generator 7 is used for converting the ordinary light beam into a vortex light beam;
the focusing objective 4 is used for focusing the vortex light speed to generate an annular distribution light spot;
the beam splitter is used for distinguishing laser light from detection signal light;
the sample scanning platform 3 is used for controlling the movement of the sample;
when the probe irradiates the surface of the metal probe 1 with the annular light beam 2 of the focused light beam, the surface plasmon wave of the propagation mode is excited, the surface plasmon wave propagates along the surface of the metal probe 1, and the surface plasmon wave is converged at the tip of the probe 1 to generate a nanometer focused light spot.
The Raman spectrum system 6 is used for collecting Raman spectrum signals;
the control system 9 and the Raman spectrum system 6 carry out bidirectional linkage control to realize sample positioning and spectrum collection.
The surface of the probe 1 is provided with a nano structure, so that the excitation of surface plasmons can be realized.
The smaller the tip size of the probe 1, the better.
The same or similar reference numerals correspond to the same or similar parts;
the terms describing positional relationships in the drawings are for illustrative purposes only and are not to be construed as limiting the patent;
it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. An optical nano-focusing method, characterized in that it comprises the steps of:
s1: preparing a nano structure on the surface of the probe by utilizing a nano processing technology;
s2: the probe is coaxially arranged with the focusing objective lens and the beam splitter;
s3: emitting a common light beam by using a laser light source, and converting the common light beam into a vortex light beam;
s4: focusing the vortex light velocity to generate annularly distributed light spots;
s5: the annular distribution light spot generated by S4 irradiates the surface of the metal probe, and the nano structure on the surface of the probe is irradiated by the annular focusing light beam to excite the surface plasmon wave of the propagation mode;
s6: the surface plasmon wave propagates along the surface of the probe and is converged at the probe tip to generate a nanometer focusing light spot.
2. The optical nano-focusing method as claimed in claim 1, wherein the vortex beam in S1 is a vortex beam with phase topological charge.
3. The optical nano-focusing method according to claim 2, wherein S1 specifically is: the ordinary light beam is passed through a vortex light beam generator to be converted into a vortex light beam.
4. The optical nano-focusing method as claimed in claim 3, wherein the center of the annular light spot in S2 is an annular distribution light spot with high intensity around the dark nucleus.
5. The optical nano-focusing method according to claim 4, wherein S2 specifically comprises: the vortex light velocity is focused by a focusing objective lens to generate annular distribution light spots.
6. The optical nano-focusing method as claimed in claim 5, wherein the focusing spot of the probe tip is a surface plasmon component; there is no conventional beam diffractive focusing component.
7. The optical nano-focusing method as claimed in claim 6, wherein the vortex light velocity is focused by the focusing objective lens to generate the ring-shaped distributed light spot in S4.
8. An optical nano-focusing device, comprising: the device comprises a probe, a sample scanning table, a focusing objective lens, a beam splitter, a Raman spectrum acquisition system, a vortex light beam generator, a laser light source and a control system;
the laser light source is used for emitting a common light beam;
the vortex light beam generator is used for converting the common light beam into a vortex light beam;
the focusing objective is used for focusing the vortex light speed to generate an annular distribution light spot;
the beam splitter is used for distinguishing laser light from detection signal light;
the sample scanning table is used for controlling the movement of the sample;
when the probe irradiates the surface of the metal probe with the annular beam of the focused beam, the surface plasmon wave in a propagation mode is excited, the surface plasmon wave propagates along the surface of the metal probe, and the surface plasmon wave is converged at the probe tip to generate a nanometer focusing light spot.
The Raman spectrum system is used for collecting Raman spectrum signals;
the control system and the Raman spectrum system perform bidirectional linkage control to realize sample positioning and spectrum collection.
9. The optical nano-focusing device of claim 8, wherein the probe surface is provided with nano-structures for exciting surface plasmons.
10. An optical nano-focusing device according to claim 8 or 9, wherein the smaller the size of the tip of the probe, the better.
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