CN110568224A - A compound near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution and its preparation method - Google Patents

Abstract

the invention belongs to the field of optical devices, and relates to a composite near-field optical probe capable of simultaneously realizing high optical signal flux and high resolution and a preparation method thereof. The optical fiber type near-field optical probe solves the technical problems that an optical signal is weak and the optical resolution depends on the aperture size of the probe in the conventional optical fiber type near-field optical probe. The core part of the composite near-field optical probe is that a nano-sized micro lens is adhered to the light outlet hole part of the probe tip of the optical fiber by using an adhesive. The composite near-field optical probe is used as a probe part of a near-field scanning microscope and applied to near-field imaging. The laser beams are converged by the micro lens after being emitted from the light outlet of the optical fiber probe, so that the spatial resolution is improved while the optical signal flux is improved. The composite near-field optical probe prepared by the invention can simultaneously improve the spatial resolution and the optical signal flux of the near-field microscope on the premise of not increasing the operation complexity. The method is low in cost, easy to implement, high in controllability and capable of realizing batch production.

Description

A Hybrid Near-Field Light Capable of Simultaneously Achieving High Optical Signal Throughput and High Resolution Chemical probe and its preparation method

technical field

The invention relates to the field of optical devices, in particular to a compound near-field optical probe capable of simultaneously realizing high optical signal flux and high resolution and a preparation method thereof.

Background technique

Due to its non-contact, non-destructive and in-situ real-time observation advantages, the optical microscope plays an important role in the activities of human beings to explore the mysteries of the microscopic world. With the development of modern science, people are eager to reveal the microscopic mechanism of life process and the relationship between the microstructure and properties of materials at the molecular level. However, optical microscopes are limited by the diffraction effect of light, and there is a resolution limit, also known as the Abbe limit. The Abbe limit means that an ideal object point is imaged by an optical system. Due to the limitation of diffraction, an ideal image point cannot be obtained, but a Fraunhofer diffraction image is obtained. Therefore, when the distance between two point objects is relatively close, the diffraction images formed after they pass through the imaging system will overlap and cannot be resolved, and the distance between the two object points that can be resolved is the limit resolution distance. For an optical microscope, the resolution limit of this diffraction image is between 200-400 nanometers. The organelles and biomolecules in the cell are about 5-100 nanometers. Therefore, it is difficult for traditional optical microscopes to accurately image intracellular structures and biomolecules. Whether this limitation can be broken is recognized as one of the major challenges in the field of optics today.

Many "super-resolution" microscopy techniques have been invented in recent years to overcome the limitations of diffraction effects, including stimulated emission depletion (STED) microscopy that exploits nonlinear effects to reduce the excitation range, stochastic optical reconstruction based on the localization of individual fluorescent molecules (STORM) and light-activated localization technology (PALM) and so on. These technologies circumvent the diffraction limitation of light through ingenious methods to achieve precise imaging of molecules or organelles with sizes above 30 nanometers. However, these super-resolution techniques still have certain limitations, such as long imaging time, the need for subsequent complex image processing, and complex optical paths. This limits the application of these techniques in cell biology.

Diffraction effects are not intrinsic to the limit of optical microscope resolution. When a sub-wavelength tiny light source irradiates the object in the near-field range of the object, the area of the illuminated spot is only related to the aperture size and has nothing to do with the wavelength. In this way, the reflected light or transmitted light will carry the sub-wavelength size structure information of the object, By collecting the signal light at each point of the sample, a near-field image of the sample with a resolution less than half the wavelength can be obtained. This line of thinking led to the birth of the near-field scanning optical microscope.

The structure of the near-field optical microscope can correspond one-to-one with the structure of the traditional far-field optical microscope, including the "local light source" composed of lasers and fiber optic probes, the "sample stage" with ultra-micro scanning devices, and the microscopic objective lens. The "optical magnification system" and other parts. The core component is the probe that provides near-field local illumination for the sample, and its light-transmitting aperture size has a decisive influence on the resolution of the near-field optical microscope. For near-field optical microscopy, in order to obtain higher resolution, on the one hand, the light beam passing through the optical probe should be confined as much as possible in the lateral direction; on the other hand, the light flux passing through the restricted area should be as large as possible to improve SNR. But the two are contradictory, the optical fiber probe aperture scale decreases, the light transmission efficiency will drop sharply, which seriously limits the application of these probes. Therefore, preparing a probe that can simultaneously achieve high light flux and high resolution will greatly expand the application of near-field microscopy.

Contents of the invention

The present invention aims to solve the technical problem that the optical signal of the fiber-optic near-field optical probe is weak and the optical resolution depends on the aperture size of the probe in the prior art, and provides a composite probe that can realize high optical signal throughput and high resolution at the same time. A near-field optical probe and a preparation method thereof.

In order to solve the problems of the technologies described above, the technical solution of the present invention is specifically as follows:

A compound near-field optical probe capable of achieving high optical signal throughput and high resolution at the same time, which consists of two parts: a fiber optic probe and a micro lens;

The optical fiber probe is a light-transmitting optical fiber with a tapered head, and the tip is provided with a light exit hole with an aperture of 20-200 nanometers, and the outer layer of the tip is coated with an opaque metal film;

The microlens is fixed at the light exit hole of the fiber probe;

The diameter or major axis diameter of the microlens is 20-500 nanometers;

When the laser light exits from the light exit hole of the optical fiber probe, it is converged by the micro-lens and reaches the sample area, thereby increasing the optical signal throughput while improving the optical resolution.

In the above technical solution, the material of the optical fiber probe is optical glass, germanium dioxide, silicon dioxide, optical matter or optical waveguide.

In the above technical solution, the optical fiber probe is a bare optical fiber.

In the above technical solution, the optical fiber probe is a cantilever beam type, an optical fiber light guiding type or a hybrid optical type.

In the above technical solution, the micro lens is ellipsoidal or spherical.

In the above technical solution, the material of the micro-lens is an optically transparent material.

In the above technical solution, the microlens is fixed at the light exit hole of the optical fiber probe using an adhesive.

In the above technical solution, the adhesive is ultraviolet curable adhesive, cyanoacrylate, epoxy resin, or silane-modified polymer.

In the above technical solution, the microlenses are circular barium titanate microspheres.

A method for preparing a compound near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution, comprising the following steps:

Cover the surface of the hydrofluoric acid etching solution with a layer of organic solvent insoluble in the etching solution as a protective phase, and then insert the optical fiber probe with a flat end face into the etching solution for static etching; the above process always keeps the temperature constant ; Carry out vacuum coating treatment on the end of the chemically etched fiber probe, and form a light exit hole with an aperture size of 20-200 nanometers at the tip of the fiber probe; finally, use an adhesive to adhere the micro lens to the light exit of the fiber probe The holes were fixed after being irradiated with UV light.

The beneficial effects of the present invention are:

The core part of the composite near-field optical probe of the present invention is to use an adhesive to adhere a nanometer-sized micro-lens to the light exit hole at the tip of the fiber probe. The compound near-field optical probe is used as a probe part of a near-field scanning microscope for near-field imaging. The laser beam exits from the light outlet of the fiber probe and is converged by the micro lens, thus improving the optical signal throughput and improving the spatial resolution at the same time. Compared with the prior art, the composite near-field optical probe prepared according to the present invention can improve the spatial resolution and optical signal flux of the near-field microscope at the same time without increasing the complexity of the operation, and solve the problem of near-field microscope signal Weak inherent problems.

The preparation method of the composite near-field optical probe provided by the invention has simple manufacturing process, low cost, easy realization, high controllability, and easy realization of mass production. Simultaneously improving probe optical signal throughput and image spatial resolution through a simple method.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

FIG. 1 is a schematic diagram of a compound near-field optical probe provided by the present invention applied to a near-field optical microscope.

The reference signs in the figure represent:

1-laser light source, 2-beam expander, 3-half slide, 4-fiber coupler, 5-atomic force microscope scanning head, 6-compound near-field optical probe, 7-sample area, 8-objective lens, 9- Avalanche counter.

Detailed ways

The invention provides a composite near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution, which is composed of an optical fiber probe and a micro lens. The optical fiber probe is a light-transmitting optical fiber with a tapered head, a light exit hole with a diameter of 20-200 nanometers is provided at the tip, and the outer layer of the tip is covered with a light-proof metal film. The microlens is fixed at the light exit hole of the fiber probe. The diameter of the microlens is 20-500 nanometers. When the laser light exits from the light exit hole of the optical fiber probe, it is converged by the micro-lens and reaches the sample area, thereby increasing the optical signal throughput while improving the optical resolution. The optical fiber probe adopts a common single-mode or multi-mode optical fiber for optical communication or a probe of a near-field optical microscope, and its material is optical glass, germanium dioxide, silica plastic, optical matter or optical waveguide. Preferably the fiber optic probe is a bare fiber. The fiber optic probe is used for local illumination, including but not limited to cantilever beam type, fiber optic light guiding type or hybrid optical type. The micro lens is ellipsoidal or spherical. The microlens is fixed at the light exit hole of the fiber probe with an adhesive that can adhere to the fiber probe and the microlens at the same time, including but not limited to ultraviolet curing glue, cyanoacrylate, ring Oxygen resins, or silane-modified polymers. The material of the microlens is an optically transparent material, preferably barium titanate. The microlenses are preferably round barium titanate microspheres.

The present invention also provides a method for preparing a composite near-field optical probe capable of simultaneously achieving high optical signal throughput and high resolution, comprising the following steps:

Cover the surface of the hydrofluoric acid etching solution with a layer of organic solvent insoluble in the etching solution as a protective phase, and then insert the optical fiber probe with a flat end face into the etching solution for static etching; the above process always keeps the temperature constant ; Carry out vacuum coating treatment on the end of the chemically etched fiber probe, and form an aperture with a size of 20-200 nanometers at the tip of the fiber probe as a light exit hole; finally, use an adhesive to adhere the micro lens to the fiber probe. At the light exit hole, the fixation is completed after being irradiated with ultraviolet light.

In order to make the purpose and technical solution of the present invention clearer, the specific implementation manner of the present invention will be described in detail below in conjunction with the accompanying drawings.

The present invention is described in detail below with the aid of preferred embodiments, but the present invention is not limited by the following embodiments. Those skilled in the art should realize that without departing from the technical features and scope provided by the technical solution of the present invention, the additions to the technical features and the replacement of some of the same content in the field should all belong to the protection of the present invention scope.

FIG. 1 is a schematic diagram of the application of the compound near-field optical probe of the present invention to a near-field optical microscope. Referring to Fig. 1, the composite near-field optical probe of the present invention capable of simultaneously achieving high optical signal throughput and high resolution is composed of a fiber probe and a micro lens. That is, the compound near-field optical probe 6 in FIG. 1 .

The preparation of the composite near-field optical probe 6 of the present invention is as follows:

The preparation of described optical fiber probe of the present invention:

The raw material of the optical fiber probe is bare optical fiber, and its main components are germanium dioxide and silicon dioxide.

Take a 100mL beaker, pour 25mL of hydrofluoric acid etching solution with a mass fraction of 30%, and then cover the surface with a layer of 4cm thick isooctane, which is an organic solvent that is insoluble in the etching solution , can be used as a protective layer; put the beaker in a constant temperature water bath at 30°C, insert the bare optical fiber with a flat end into the hydrofluoric acid etching solution, and perform static etching for 90 minutes; after the etching is completed, place the tip of the bare optical fiber in a Ionized water, and ultrasonic cleaning to remove residual hydrofluoric acid and isooctane; use vacuum coating method to modify the tapered fiber optic probe tip obtained by chemical etching method to obtain light-through holes. Specific operation: The evaporation source vaporizes the rotating fiber optic probe tip at a certain inclination angle. Since the end face of the fiber optic probe tip is blocked by itself, it will not be plated with metal, and it can form a direct aperture at the fiber probe tip. 20-200 nanometer level light-transmitting holes without metal. The metal coating becomes an effective aperture for the rest of the fiber optic probe. In this embodiment, the vapor deposition angle is adjusted to obtain light-transmitting small holes with a diameter of 100 nanometers.

Preparation of the composite near-field optical probe 6 of the present invention:

The optical fiber probe adopts the optical fiber probe prepared above, and its tip has a light-transmitting small hole with a diameter of 100 nanometers, and an appropriate amount of ultraviolet curing glue is coated on the tip of the optical fiber probe. Use barium titanate round microspheres with a diameter of 200 nanometers as micro-lenses, adhere the barium titanate round microspheres to the light exit hole of the fiber optic probe with ultraviolet curing glue, and irradiate them under ultraviolet light (200W/cm ² ) for 10 minutes Finally, the fixation is completed, and the composite near-field optical probe 6 is prepared.

An embodiment of the compound near-field optical probe of the present invention being applied to a near-field optical microscope:

Install the composite near-field optical probe 6 prepared above on the scanning head 5 of the atomic force microscope, and make the composite near-field optical probe 6 close to the sample surface on the sample area 7 under the control of the atomic force microscope controller, and pass through the Interacts with the shear force between the samples to maintain a constant distance from the sample. The compound near-field optical probe 6 is connected to the laser light source 1 and the fiber coupler 4, and the 325nm laser emitted by the laser light source 1 enters the compound type through the beam expander 2, the half glass 3 and the fiber coupler 4. The light outlet of the fiber optic probe of the near-field optical probe 6 is converged by the micro-lens of the composite near-field optical probe 6 after exiting, that is, the barium titanate round microspheres. The light beams are converged, and the converged light is irradiated to a very small area in the sample area 7 . The transmitted light carrying the sample information is received by the objective lens 8, and finally the signal can be collected by the avalanche counter 9. The near-field imaging map with high spatial resolution is obtained by cumulatively imaging the point light source after point-by-point scanning and point-by-point recording on the surface.

In the above examples, the fiber optic probe used in the present invention can also be other types or materials defined above, and the microlens used can also be other shapes, diameters or major axis diameters, materials defined above, and the adhesive used can also be It can also be other types of adhesives defined above, which will not be enumerated here.

The core part of the composite near-field optical probe of the present invention is to use an adhesive to adhere a nanometer-sized micro-lens to the light exit hole at the tip of the fiber probe. The compound near-field optical probe is used as a probe part of a near-field scanning microscope for near-field imaging. The laser beam exits from the light outlet of the fiber probe and is converged by the micro lens, thus improving the optical signal throughput and improving the spatial resolution at the same time. Compared with the prior art, the composite near-field optical probe prepared according to the present invention can improve the spatial resolution and optical signal flux of the near-field microscope at the same time without increasing the complexity of the operation, and solve the problem of near-field microscope signal Weak inherent problems. Moreover, the preparation method of the invention has low cost, is easy to realize, has high controllability, and can be produced in batches.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. A compound near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution is characterized in that it is composed of two parts: an optical fiber probe and a micro lens; The optical fiber probe is a light-transmitting optical fiber with a tapered head, and the tip is provided with a light exit hole with an aperture of 20-200 nanometers, and the outer layer of the tip is coated with an opaque metal film; The microlens is fixed at the light exit hole of the fiber probe; The diameter or major axis diameter of the microlens is 20-500 nanometers; When the laser light exits from the light exit hole of the optical fiber probe, it is converged by the micro-lens and reaches the sample area, thereby increasing the optical signal throughput while improving the optical resolution. 2. the composite near-field optical probe capable of realizing high optical signal throughput and high resolution simultaneously according to claim 1, is characterized in that, the material of the optical fiber probe is optical glass, germanium dioxide, bismuth Silicon oxide, optical matter or optical waveguide. 3. The compound near-field optical probe capable of simultaneously achieving high optical signal throughput and high resolution according to claim 1, wherein the fiber probe is a bare optical fiber. 4. The composite near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution according to claim 1, wherein the fiber probe is a cantilever beam type, an optical fiber light guide type or a hybrid optical type. 5 . The compound near-field optical probe capable of simultaneously achieving high optical signal throughput and high resolution according to claim 1 , wherein the microlens is ellipsoidal or spherical. 6 . 6 . The compound near-field optical probe capable of simultaneously achieving high optical signal throughput and high resolution according to claim 1 , wherein the material of the microlens is an optically transparent material. 7. The composite near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution according to claim 1, wherein the microlens is fixed on the fiber probe using an adhesive. At the light hole. 8. The composite near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution according to claim 7, wherein the adhesive is an ultraviolet curable adhesive, cyanoacrylate, ring Oxygen resins, or silane-modified polymers. 9. The composite near-field optical probe capable of simultaneously realizing high optical signal throughput and high resolution according to any one of claims 1-8, wherein the microlens is a circular barium titanate Microspheres. 10. A method for preparing a compound near-field optical probe capable of realizing high optical signal throughput and high resolution simultaneously according to any one of claims 1-8, characterized in that it comprises the following steps: Cover the surface of the hydrofluoric acid etching solution with a layer of organic solvent insoluble in the etching solution as a protective phase, and then insert the optical fiber probe with a flat end face into the etching solution for static etching; the above process always keeps the temperature constant ; Carry out vacuum coating treatment on the end of the chemically etched fiber probe, and form a light exit hole with an aperture size of 20-200 nanometers at the tip of the fiber probe; finally, use an adhesive to adhere the micro lens to the light exit of the fiber probe The holes were fixed after being irradiated with UV light.