WGM-based single-fiber near-field optical tweezers

Abstract

The invention belongs to the technical field of near-field optical tweezers, and particularly relates to a pair of WGM-based single-fiber near-field optical tweezers, which comprises a silicon dioxide hollow microsphere, a laser light source and an optical fiber unit, and is characterized in that the silicon dioxide hollow microsphere comprises a spherical shell area and a hollow area positioned in the spherical shell area, and the refractive index of the spherical shell area is higher than that of the hollow area; the laser light source is used for emitting laser, the laser light source refracts the laser into the spherical shell area with the incidence angle being 90 degrees, an evanescent field is generated on the outer surface of the silicon dioxide hollow microsphere, and the laser emitted by the laser light source is 980 nm and 532 nm in wavelength. The near-field optical tweezers and the WGM structure can be combined, total reflection is carried out on the inner surface of the ball microcavity to form an evanescent field on the outer surface, the function of capturing nano-scale particles is achieved, and the purpose of capturing the nano-scale particles at different positions is achieved by changing the wavelength of incident laser.

Description

Technical Field

[0001] The invention belongs to the technical field of near-field optical tweezers, and in particular relates to single-fiber near-field optical tweezers based on WGM. Background Art

[0002] The theory of optical capture is based on the radiation force of light. Quantum theory holds that light is a stream of photons that move at the speed of light and have both mass and momentum. The interaction between the light radiation field and an object will cause the object to be affected by the radiation force of light. Laser capture is to use the dynamic effect of laser to achieve stable capture of particles.

[0003] Since optical tweezers use invisible light beams to achieve non-mechanical contact capture of particles, no mechanical damage will occur. All mechanical parts of the optical tweezers are much farther away from the captured object than the size of the captured object. It is a "remote control" operation, and thus has little impact on the surrounding environment of the particle. In addition, due to the characteristics of biological particles such as light penetration, optical tweezers technology is particularly suitable for living biological particles. The manipulation of particles by optical tweezers is not rigid, and the tiny interaction forces between particles can be measured in real time during the operation. Therefore, optical tweezers are also force probes or force sensors during the interaction of particles. This makes optical tweezers not only a manipulator for manipulating tiny particles, but also an ideal tool for studying the static and dynamic mechanical properties of tiny particles.

[0004] With the development of optical tweezers technology, further distinctions have been made based on the characteristics of the field. Optical tweezers are mainly divided into far-field optical tweezers based on propagation fields and near-field optical tweezers based on evanescent fields. According to the theory of near-field optics, near field and far field are only relative. People define the near field as: a freely propagating radiation field and an evanescent wave that is confined to the surface of a material and rapidly decays with distance. Because the evanescent wave is an inhomogeneous wave, it exists due to the medium and cannot exist in free space. The finer the structure of the medium, the more strongly the evanescent field can be confined to its surface (Zhao Yu. Research on micro-nano fiber optic tweezers based on evanescent field [D]. North University of China, 2014.).

[0005] Through continuous research, surface plasmon technology was discovered. The research on surface plasmon polaritons has gradually emerged, providing a new perspective for the generation of evanescent fields. Using metal nanostructures to excite surface plasmons can generate powerful evanescent fields.

[0006] In the early 2000s, near-field optical tweezers technology developed rapidly. Researchers began to use optical fiber tips, metal nanoparticles, and other microstructures to generate strong evanescent fields and capture and manipulate nanoparticles.

[0007] During this period, the application of evanescent field optical tweezers in the biomedical field gradually emerged, and researchers conducted a series of experiments using its ability to manipulate biological molecules and cells at the micron and nanoscale.

[0008] So far, among all the optical tweezers that use the field principle, the basic principle is to use the total reflection principle of laser to form an evanescent field at the interface, and then achieve the purpose of generating a near-field light field.

[0009] As the technology matures, the application scope of near-field optical tweezers continues to expand, including biological imaging, manipulation of nanomaterials, regulation of chemical reactions, etc. Researchers have achieved high-sensitivity and high-precision particle capture by improving the design of the equipment.

[0010] In 1992, Satoshi Kawata, Tadao Sugiura et al. (Kawata S, Sugiura T. Movement of micrometer-sized particles in the evanescent field of a laser beam [J]. Optics letters, 1992, 17 (11): 772-774.) first used the evanescent field generated by prism total reflection to realize the manipulation of particles. When the incident angle of s-polarized light is greater than the critical angle, the 6.8μm diameter particle moves at a high speed of 8μm / s along the prism surface under the action of the evanescent field formed by total reflection on the sapphire prism surface. This experiment opened up in-depth research on near-field optical micromanipulation based on evanescent field. However, the evanescent field intensity generated by total reflection of a single prism is weak, and it is difficult to eliminate the influence of the external environment on particle capture.

[0011] In order to overcome the limitation of diffraction optics on gradient force and improve the accuracy of optical tweezers capture, in 2004, Kwak et al. (KwakES, OnutaTD, AmarieD, et al.Optical trapping with integrated near-fieldapertures[J].TheJournal of Physical ChemistryB,2004,108(36):13607-13612.) proposed to use laser to illuminate nano-apertures on metal film substrate to produce rapidly decaying evanescent field to achieve the capture of smaller size microspheres. Nano-aperture near-field optical tweezers can achieve the capture of nano-scale microspheres, providing a platform for ultra-sensitive measurement of sub-wavelength structured biophotonic sensors and dynamic characteristics of particles in a closed environment. However, it is not possible to capture a single nano-particle because all apertures will capture particles at the same time after light is passed.

[0012] In 2004, Min Gu et al. (Gu M, Haumonte JB, Micheau Y, et al. Laser trapping and manipulation under focused evanescent wave illumination [J]. Applied Physics Letters, 2004, 84 (21): 4236-4238.) used a microscope with a high numerical aperture to converge an annular hollow light beam, and then produced total reflection at the glass-solution interface, thereby capturing polystyrene microspheres with a diameter of 2 μm. Since multiple light beams interfere at the focal point, the intensity of the evanescent field is enhanced on the one hand, and the size of the axial capture is reduced on the other hand. Focusing the evanescent field optical tweezers can solve the problem that the distance between the probe and the sample is difficult to control due to the small range of the evanescent field, and can also overcome the defect of unstable capture caused by the thermal effect of the plasma resonance of the metal probe type optical tweezers.

[0013] Near-field optical manipulation also includes optical tweezers based on micro-resonant cavity coupling structure. The highly localized field in the cavity can generate a sufficiently strong force on the particles so that the particles are captured on the micro-cavity surface and move along the annular cavity. At the same time, the interference of the particles on the cavity can be used as a highly sensitive probe to analyze the physical properties of the object (size, refractive index, etc.). In 2010, Shi et al. (Lin S, Schonbrun E, Crozier K.Optical manipulation with planar silicon microring resonators [J]. Nano letters, 2010, 10 (7): 2408-2411.) from Harvard University analyzed in detail the interaction between the planar annular microcavity and the particles, the rigidity of the capture force, and the depth of the potential well. It was measured in the experiment that the power coupled into the straight waveguide was 0.67mW, which could achieve stable capture of the particles. Once the particle is captured, it is confined to the micro-cavity environment with a potential well depth of 25kBT and moves along the micro-cavity. However, the micro-ring resonator is a single-mode structure, and the particles can only achieve single-track movement.

[0014] In summary, the above-mentioned methods of generating evanescent fields to form approach capture have their own advantages and disadvantages. For example, the above-mentioned methods of generating evanescent fields to form approach capture can achieve the function of capturing nano-scale particles, but cannot change the position of capturing nano-particles according to needs. Summary of the invention

[0015] The purpose of the present invention is to provide a single-fiber near-field optical tweezers based on WGM, which can combine the near-field optical tweezers and the WGM (gallery mode) structure, and realize the function of capturing nano-scale particles by forming an evanescent field on the outer surface through total reflection on the inner surface of the spherical microcavity, and achieve the purpose of capturing nano-particles at different positions by changing the wavelength of the incident laser.

[0016] The technical solution adopted by the present invention is as follows:

[0017] A single-fiber near-field optical tweezers based on WGM, comprising:

[0018] Silica hollow microspheres, the silica hollow microspheres comprising a spherical shell region and a hollow region located inside the spherical shell region, and the refractive index of the spherical shell region is higher than that of the hollow region;

[0019] A laser light source is used to radiate laser light. The laser light source refracts the laser light into the spherical shell region at an incident angle of 90°, thereby generating an evanescent field on the outer surface of the hollow silica microsphere.

[0020] Furthermore, the laser light source emits laser wavelengths of 980nm and 532nm.

[0021] Furthermore, it also includes an optical fiber unit, one end of which is connected to the laser light source, and the hollow silica microspheres are fixedly connected to the other end of the optical fiber unit.

[0022] Furthermore, the optical fiber unit is an eccentric optical fiber line, the hollow silica microsphere is fixedly connected to the center position of the end of the eccentric optical fiber line, an eccentric fiber core body is arranged inside the eccentric optical fiber line, the distance from the center position of the eccentric optical fiber line to the eccentric fiber core body is the optical fiber eccentricity, and the radius of the hollow silica microsphere is the same as the optical fiber eccentricity.

[0023] Furthermore, it also includes:

[0024] Motorized micromanipulator;

[0025] A microscope, wherein a stage is mounted on the microscope;

[0026] CCD, mounted on the lower side of the microscope stage, used to collect and record the light field image on the stage;

[0027] Computer, which is electrically connected to the microscope and is used to display the images collected by the CCD

[0028] The laser light source includes a 532nm laser light source and a 980nm laser light source. The 980nm laser light emitted by the 980nm laser light source forms a light field on the stage of the microscope, and the 532nm laser light emitted by the 532nm laser light source serves as an indicator for the light field.

[0029] The eccentric optical fiber line and the hollow silica microspheres constitute a special optical fiber;

[0030] The 532nm laser light source and the 980nm laser light source are connected via ordinary single-mode optical fiber and special optical fiber;

[0031] The special optical fiber is assembled on a motorized micromanipulator.

[0032] A method for using single-fiber near-field optical tweezers based on WGM comprises the following steps:

[0033] Step 1: Take 500nm polystyrene microspheres in a reagent bottle, then add an appropriate amount of distilled water, seal and place in an ultrasonic oscillation device to ensure that the polystyrene microspheres are fully dissolved in water, and oscillate for 3 minutes;

[0034] Step 2: Control the electric micromanipulator so that the optical fiber probe with hollow silica microspheres of the special optical fiber appears in the field of view of the microscope, and adjust the focal length so that the optical fiber probe can be observed by the microscope, then take the polystyrene aqueous solution on a glass slide, place it on the glass slide of the microscope, and continue to adjust the focal length of the microscope to ensure that the optical fiber probe and the polystyrene microparticles in the polystyrene aqueous solution can be observed;

[0035] Step 3: Input 980nm laser to form an evanescent field at the end face of the optical fiber probe;

[0036] Step 4: Then operate the microscope to adjust the relative position of the polystyrene microparticle aqueous solution on the slide to capture the polystyrene microparticles.

[0037] The technical effects achieved by the present invention are:

[0038] The single-fiber near-field optical tweezers based on WGM of the present invention utilizes a combination of near-field optical tweezers and WGM (gallery mode) structure in structure, and forms an evanescent field on the outer surface through total reflection on the inner surface of a spherical microcavity, thereby capturing particles and forming a relatively novel fiber optical tweezers structure. Compared with other structure optical tweezers that can only capture micrometer-sized particles, the fiber optical tweezers can achieve the function of capturing nanometer-sized particles in terms of the scale of captured particles. At the same time, the evanescent field generated by this method can capture multiple nanoparticles at the position of an evanescent field to form a self-assembled structure, and the purpose of capturing nanoparticles at different positions can be achieved by changing the wavelength of the incident laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of single fiber optical tweezers in Example 1 of the present invention;

[0040] Figure 2 The present invention Figure 1 A partial enlarged view of the middle A;

[0041] Figure 3 The present invention Figure 1 A partial enlarged view of point B in the middle;

[0042] Figure 4 is a schematic diagram of a system in Embodiment 3 of the present invention;

[0043] Figure 5 It is a schematic diagram of the dislocation welding of a common single-mode optical fiber and an offset core optical fiber of the present invention;

[0044] Figure 6 Schematic diagram of the light force at the evanescent field on the outer surface of the microsphere of the present invention;

[0045] Figure 7 is a schematic diagram of the present invention's evanescent field capturing multiple nanoparticles to form self-assembly;

[0046] Figure 8 It is a schematic diagram of the present invention in which the particle capture position moves when the wavelength of the incident laser is changed.

[0047] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0048] 1-1, eccentric optical fiber; 1-1-1, eccentric fiber core; 1-2, UV curing glue; 1-3, hollow microsphere; 1-3-1, spherical shell region; 1-3-2, hollow region; 1-4, evanescent field; 2-1, computer; 2-3, special optical fiber; 2-4, microscope; 2-5, CCD; 2-6, 532nm laser light source; 2-7, 980nm laser light source; 2-8, electric micromanipulator; 2-9, ordinary single-mode optical fiber; 3-1, laser beam; 3-2, single-mode optical fiber connecting end; 3-3, eccentric optical fiber connecting end; 5-1, polystyrene aqueous solution; 5-2, nanoparticles; 6-1, white dotted line; 6-2, black solid line; 6-3, evanescent field. DETAILED DESCRIPTION

[0049] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0050] Embodiment 1:

[0051] like Figure 1-Figure 8As shown, a single-fiber near-field optical tweezer based on WGM includes a laser light source, an optical fiber unit and a hollow silica microsphere 1-3;

[0052] The hollow silica microsphere 1-3 comprises a spherical shell region 1-3-1 and a hollow region 1-3-2 located inside the spherical shell region 1-3-1, and the refractive index of the spherical shell region 1-3-1 is higher than that of the hollow region 1-3-2.

[0053] Among them, the laser light source is used to radiate laser light into the spherical shell area 1-3-1, and preferably refracts the laser light into the spherical shell area 1-3-1 at an incident angle of 90°. Since the refractive index of the middle spherical shell area 1-3-1 is higher than that of the hollow area 1-3-2, the laser light refracted by the laser light source into the spherical shell area 1-3-1 will propagate along the spherical shell area 1-3-1 for one circle without being refracted out again, thereby forming a stable corridor mode and generating an evanescent field 1-4 on the outer surface of the hollow silica microsphere 1-3. Since the light field density of the evanescent field 1-4 is relatively small, the combined action of the gradient force and the scattering force can be used to capture smaller-sized particles, and the present structure is sufficient to capture nanoscale tiny particles.

[0054] Here, the wavelength of the laser emitted by the laser light source can be changed, but its wavelength should satisfy the interference enhancement when it is totally reflected in the hollow area 1-3-2 and returns to the origin.

[0055] Preferably, the laser wavelengths emitted by the laser light source are 980nm laser and 532nm, wherein the 980nm laser provides an energy to form a light field, and the 532nm laser mainly functions as an indication of the light field.

[0056] Among them, one end of the optical fiber unit is connected to the laser light source, and the silica hollow microsphere 1-3 is fixedly connected to the other end of the optical fiber unit. At this time, the laser emitted by the laser light source is transmitted through the optical fiber unit, and through the fixed position relationship between the silica hollow microsphere 1-3 and the optical fiber unit, the laser can be simply and stably refracted into the spherical shell area 1-3-1 at an incident angle of 90°.

[0057] Furthermore, the optical fiber unit can be a concentric optical fiber or an eccentric optical fiber. In the present technical solution, an eccentric optical fiber line 1-1 is preferred. The hollow silica microsphere 1-3 is fixedly connected to the center position of the end of the eccentric optical fiber line 1-1. An eccentric fiber core body 1-1-1 is arranged inside the eccentric optical fiber line 1-1, so that the eccentric fiber core body 1-1-1 and the hollow silica microsphere 1-3 of the eccentric optical fiber line 1-1 are eccentrically arranged. In order to reduce optical loss, it is necessary to select a suitable outer radius of the hollow silica microsphere 1-3. In the present technical solution, the distance from the center position of the eccentric optical fiber line 1-1 to the eccentric fiber core body 1-1-1 is the optical fiber eccentricity. The radius of the hollow silica microsphere 1-3 needs to be roughly the same as the optical fiber eccentricity, so that the laser emitted from the eccentric fiber core body 1-1-1 is refracted into the spherical shell area 1-3-1 at an incident angle of 90°.

[0058] like Figure 1 As shown, a fixing method of the silica hollow microspheres 1-3 is disclosed herein, a UV curing glue 1-2 is provided at the end of the eccentric optical fiber 1-1, and the silica hollow microspheres 1-3 are bonded to the end of the eccentric optical fiber 1-1 through the UV curing glue 1-2, thereby facilitating the connection between the eccentric optical fiber 1-1 and the silica hollow microspheres 1-3, and the refractive index of the UV curing glue 1-2 and the refractive index of the silica hollow microspheres 1-3 are 1.459 and 2.2, respectively.

[0059] Embodiment 2:

[0060] like Figure 1-Figure 8 As shown, in this embodiment, the capture mechanism of the single-fiber near-field optical tweezers is disclosed in detail. The capture mechanism of the single-fiber near-field optical tweezers is mainly through emitting laser from the offset core optical fiber line 1-1, then entering the silica hollow microsphere 1-3, and forming an evanescent field 1-4 by total reflection at a certain point on the outer surface of the spherical shell area 1-3-1. The optical force of the evanescent field 1-4 at this point is as follows: Figure 6 As shown. Since it is formed by total reflection of light, its existence distance is limited. The farther away from the outer surface of the hollow silica microspheres 1-3, the weaker the light field force. Secondly, the particles in the light field are subjected to a scattering force parallel to the outer surface and in the direction of the light beam and a gradient force perpendicular to the outer surface of the hollow silica microspheres 1-3 and pointing to the hollow silica microspheres 1-3, thereby firmly binding the particles in the liquid environment.

[0061] In addition, the mechanism of the generation of evanescent fields 1-4 can be explained from the direction of total reflection of light. When light is incident from the optically dense medium n1 to the optically sparse medium n2, when the incident angle is greater than the critical angle When the incident wave is reflected by the light, total reflection will occur at the incident interface. At this time, although the incident wave energy is completely reflected back to the optically dense medium, there are still surface waves near the interface surface in the optically sparse medium, which are evanescent waves.

[0062] The position of the particle capture region 6-3 generated in the evanescent field 1-4 on the outer surface of the hollow silica microsphere 1-3 will change with the change of the wavelength. Figure 8 It can be seen that as the wavelength of the incident laser is reduced, the reflected light path inside the hollow silica microsphere 1-3 changes from the white dotted line 6-1 to the black solid line 6-2. At the same time, the position of the captureable particle area 6-3 for capturing the nanoparticle 5-2 also changes accordingly, thereby achieving stable capture of the studied nanoparticle 5-2 at different positions on the outer surface of the hollow silica microsphere 1-3.

[0063] The particle self-assembly captures multiple nanoparticles 5-2 by light trapping force within the formed evanescent field 1-4 light field. Figure 7 As shown, since the optical trapping force of its optical field is determined, the nanoparticles 5-2 captured by its optical field will accumulate together to form a specific shape and cannot be changed.

[0064] The technical solution structurally utilizes a combination of near-field optical tweezers and WGM (gallery mode) structures. By performing total reflection on the inner surface of the spherical microcavity and forming an evanescent field 1-4 on the outer surface, the particles are captured, and a relatively novel fiber optic tweezers structure is formed. In terms of the scale of captured particles, compared with other structural optical tweezers that can only capture micron-sized particles, the fiber optic tweezers can achieve the function of capturing nanometer-sized particles. At the same time, the evanescent field 1-4 generated by this method can capture multiple nanoparticles 5-2 at the position of an evanescent field 1-4 to form a self-assembled structure, and the purpose of capturing nanoparticles 5-2 at different positions can be achieved by changing the wavelength of the incident laser.

[0065] Embodiment 3:

[0066] like Figure 1-3 As shown, this embodiment further discloses a structure of a single-fiber near-field optical tweezers based on WGM on the basis of Embodiment 1, and specifically, the single-fiber near-field optical tweezers also includes a computer 2-1, a microscope 2-4, a CCD 2-5 and an electric micromanipulator 2-8;

[0067] A stage is mounted on the microscope 2-4;

[0068] The laser light sources include a 532nm laser light source 2-6 and a 980nm laser light source 2-7. The 980nm laser emitted by the 980nm laser light source 2-7 forms a light field on the stage of the microscope 2-4, and the 532nm emitted by the 532nm laser light source 2-6 serves as an indicator for the light field.

[0069] CCD2-5 is installed on the lower side of the microscope 2-4 stage and is used to collect and record the light field image on the stage. CCD2-5 is used to observe the light field carefully. The end of the ordinary single-mode optical fiber 2-9 away from the 532nm laser light source 2-6 and the 980nm laser light source 2-7 is the single-mode optical fiber connection end 3-2, and the end of the eccentric optical fiber line 1-1 away from the silica hollow microsphere 1-3 is the eccentric optical fiber connection end 3-3. When the light field is stable enough, the single-mode optical fiber connection end 3-2 and the eccentric optical fiber connection end 3-3 are welded together by a welding machine to complete the staggered welding of the ordinary single-mode optical fiber 2-9 and the eccentric optical fiber line 1-1. After the staggered welding is completed, the laser beam 3-1 emitted by the 532nm laser light source 2-6 and the 980nm laser light source 2-7 can be transmitted to the eccentric optical fiber line 1-1 through the ordinary single-mode optical fiber 2-9.

[0070] Here, the eccentric optical fiber line 1-1 and the silica hollow microspheres 1-3 constitute a special optical fiber 2-3. Meanwhile, the special optical fiber 2-3 may also include a UV curing glue 1-2.

[0071] The 532nm laser light source 2-6 and the 980nm laser light source 2-7 are connected to the special optical fiber 2-3 through the common single-mode optical fiber 2-9, so that the lasers emitted by the 532nm laser light source 2-6 and the 980nm laser light source 2-7 can be emitted through the special optical fiber 2-3.

[0072] The special optical fiber 2-3 is mounted on an electric micromanipulator 2-8, and the position of the special optical fiber 2-3 can be adjusted by the electric micromanipulator 2-8;

[0073] The computer 2-1 and the microscope 2-4 are electrically connected to display the image captured by the CCD2-5.

[0074] Embodiment 4:

[0075] like Figure 1-6 As shown, this embodiment discloses a method for manufacturing a single-fiber near-field optical tweezers based on Embodiment 3, and the manufacturing method includes the following steps:

[0076] Step 1: Cut off about 2m of the eccentric optical fiber 1-1, use a wire stripper to strip off about 2cm of the coating layer at one end of the eccentric optical fiber 1-1, and use an alcohol cloth with alcohol to wipe the section of optical fiber to ensure that the end face is clean and pollution-free, use a light cutter to cut its end face as flat as possible, and then stick the eccentric optical fiber 1-1 vertically to the three-position adjustment frame of the electric micromanipulator 2-8, and manipulate it under the microscope 2-4. First, use the microscope 2-4 to find the silica hollow microsphere 1-3 of the appropriate size, and then use the electric micromanipulator 2-8 manipulate the eccentric optical fiber 1-1 to pick up a small amount of UV curing glue 1-2, so that the UV curing glue 1-2 exists at the optical fiber end of the eccentric optical fiber 1-1, and then move it back to the top of the found silica hollow microsphere 1-3, and use the viscosity of the UV curing glue 1-2 to adsorb the silica hollow microsphere 1-3, and finally use a UV lamp to irradiate the UV curing glue 1-2 at the connection between the eccentric optical fiber 1-1 and the silica hollow microsphere 1-3. The UV curing glue 1-2 will solidify in about 1 minute, and the optical fiber tweezers of this structure can be completed.

[0077] When the end face of the eccentric optical fiber 1-1 and the hollow silica microspheres 1-3 are clearly visible under the microscope 2-4, the hollow silica microspheres 1-3 are bonded to the end face of the eccentric optical fiber 1-1 to ensure that the bonding position of the hollow silica microspheres 1-3 is correct to ensure normal transmission of the laser and generate an evanescent field 1-4 that can capture nano-sized particles.

[0078] Step 2: The end faces of the eccentric fiber connection end 3-3 and the single-mode fiber connection end 3-2 at the other end of the eccentric fiber line 1-1 are processed to make them smooth and neat. The eccentric fiber line 1-1 of about 2 mm is cut, and the coating layer of about 2 cm is stripped off at one end using a wire stripper, and the processed ordinary single-mode fiber 2-9 and the eccentric fiber line 1-1 are cut with an optical fiber cutter to ensure that the end faces are neat and flat. Then, the optical fiber fusion splicer unique to the laboratory is used to fusion splice the optical fibers. First, the automatic program of the fusion splicer is used to make preliminary corrections to the end faces of the two optical fibers, and then the mode is adjusted to manual, and the motor adjustment option of the fusion splicer is selected to manually move the ordinary single-mode optical fiber 2-9 until the core of the ordinary single-mode optical fiber 2-9 is aligned with the core of the eccentric fiber line 1-1. At this time, press the completion key, and the system welds it. At this time, the step of dislocation fusion splicing of the two optical fibers is completed. After the dislocation welding is completed, the output light field and welding point need to be observed under the microscope 2-4.

[0079] Here, the cladding diameters of the common single-mode optical fiber 2-9 and the eccentric optical fiber 1-1 are unified to be 125 μm. The consistency of the diameters of the common single-mode optical fiber 2-9 and the eccentric optical fiber 1-1 can ensure consistent transmission.

[0080] Embodiment 5:

[0081] This embodiment discloses a method for using single-fiber near-field optical tweezers based on Embodiment 3, and the method for using includes the following steps:

[0082] Step 1: Take an appropriate amount of 500nm polystyrene microspheres into a reagent bottle, then add an appropriate amount of distilled water, seal and place in an ultrasonic oscillation device to ensure that the polystyrene microspheres are fully dissolved in water, and oscillate for about 3 minutes to form a polystyrene microparticle aqueous solution 5-1.

[0083] Step 2: Control the electric micromanipulator 2-8 so that the optical fiber probe of the special optical fiber 2-3 having the hollow silica microspheres 1-3 appears in the field of view of the microscope 2-4 used for observation, and adjust the focal length so that the microscope 2-4 can clearly observe the structure of the optical fiber probe, and then use a micropipette to absorb a small amount of the polystyrene microparticle aqueous solution 5-1 onto a glass slide, place it on the glass slide of the microscope 2-4, and continue to adjust the focal length of the microscope 2-4 to ensure that the optical fiber probe and the polystyrene microparticles in the polystyrene microparticle aqueous solution 5-1 can be observed.

[0084] Step 3: At this time, a 980nm laser is input into the common single-mode optical fiber 2-9 and fully coupled into the eccentric optical fiber line 1-1, so that an evanescent field 1-4 can be formed on the end face of the manufactured optical fiber probe;

[0085] Step 4: Then operate the microscope 2-4, adjust the relative position of the polystyrene microparticle aqueous solution 5-1 on the slide, and try to capture the polystyrene microparticles. When observing the polystyrene microparticles on the end surface of the optical fiber probe, slowly move the optical fiber probe to observe whether the microparticles move with the movement of the optical fiber probe to ensure that the polystyrene microparticles are stably captured.

[0086] In step 2, by changing the wavelength of the incident laser, an evanescent field 1-4 can be formed at different positions on the outer surface of the offset optical fiber 1-1, thereby achieving the purpose of changing the position of capturing the nanoparticles 5-2.

[0087] Here, the optical fiber probe is a special optical fiber 2-3 having a hollow silica microsphere 1-3 at one end.

[0088] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A single-fiber near-field optical tweezers based on WGM, characterized by: include: Silica hollow microspheres (1-3), the silica hollow microspheres (1-3) comprising a spherical shell region (1-3-1) and a hollow region (1-3-2) located inside the spherical shell region (1-3-1), and the refractive index of the spherical shell region (1-3-1) is higher than that of the hollow region (1-3-2); A laser light source is used to radiate laser light, and the laser light enters the spherical shell region (1-3-1) to generate an evanescent field (1-4) on the outer surface of the hollow silica microsphere (1-3).

2. The single-fiber near-field optical tweezers based on WGM according to claim 1, characterized in that: The laser light source refracts the laser into the spherical shell region (1-3-1) at an incident angle of 90°.

3. The single-fiber near-field optical tweezers based on WGM according to claim 1, characterized in that: The laser light source emits laser wavelengths of 980nm and 532nm.

4. The single-fiber near-field optical tweezers based on WGM according to claim 1, characterized in that: It also comprises an optical fiber unit, one end of which is connected to a laser light source, and the hollow silica microspheres (1-3) are fixedly connected to the other end of the optical fiber unit.

5. The single-fiber near-field optical tweezers based on WGM according to claim 3, characterized in that: The optical fiber unit is an eccentric optical fiber (1-1); the hollow silica microsphere (1-3) is fixedly connected to the center position of the end of the eccentric optical fiber (1-1); an eccentric fiber core (1-1-1) is arranged inside the eccentric optical fiber (1-1); the distance from the center position of the eccentric optical fiber (1-1) to the eccentric fiber core (1-1-1) is the optical fiber eccentricity; and the radius of the hollow silica microsphere (1-3) is the same as the optical fiber eccentricity.

6. The single-fiber near-field optical tweezers based on WGM according to claim 5, characterized in that: The end of the eccentric optical fiber (1-1) is provided with a UV curing adhesive (1-2), and the hollow silica microspheres (1-3) are bonded to the end of the eccentric optical fiber (1-1) by the UV curing adhesive (1-2).

7. The single-fiber near-field optical tweezers based on WGM according to claim 6, characterized in that: The refractive index of the UV curing adhesive (1-2) and the refractive index of the hollow silica microspheres (1-3) are 1.459 and 2.2 respectively.

8. A single-fiber near-field optical tweezers based on WGM according to any one of claims 5 to 7, characterized in that: Also includes: Electric micromanipulator (2-8); A microscope (2-4), wherein a stage is installed on the microscope (2-4); CCD (2-5), mounted on the lower side of the stage of the microscope (2-4), for collecting and recording the light field image on the stage; A computer (2-1) is electrically connected to a microscope (2-4) and is used to display images collected by a CCD (2-5). The laser light source comprises a 532nm laser light source (2-6) and a 980nm laser light source (2-7); the 980nm laser light emitted by the 980nm laser light source (2-7) forms a light field on the stage of the microscope (2-4); and the 532nm laser light emitted by the 532nm laser light source (2-6) serves as an indicator for the light field; The eccentric optical fiber (1-1) and the hollow silica microspheres (1-3) form a special optical fiber (2-3); The 532nm laser light source (2-6) and the 980nm laser light source (2-7) are connected via a common single-mode optical fiber (2-9) and a special optical fiber (2-3); The special optical fiber (2-3) is assembled on an electric micromanipulator (2-8).

9. The single-fiber near-field optical tweezers based on WGM according to claim 8, characterized in that: The cladding diameters of the common single-mode optical fiber (2-9) and the eccentric optical fiber (1-1) are uniformly 125 μm.

10. A method for using a single-fiber near-field optical tweezers based on WGM, using the single-fiber near-field optical tweezers based on WGM according to claim 8, characterized in that: The following steps are involved: Step 1: Take 500nm polystyrene microspheres in a reagent bottle, then add an appropriate amount of distilled water, seal and place in an ultrasonic oscillation device to ensure that the polystyrene microspheres are fully dissolved in water, and oscillate for 3 minutes; Step 2: Control the electric micromanipulator (2-8) so that the optical fiber probe having the hollow silica microspheres (1-3) of the special optical fiber (2-3) appears in the field of view of the microscope (2-4), and adjust the focal length so that the optical fiber probe can be observed by the microscope (2-4), then take the polystyrene microparticle aqueous solution (5-1) on a glass slide, place it on the glass slide of the microscope (2-4), and continue to adjust the focal length of the microscope (2-4) to ensure that the optical fiber probe and the polystyrene microparticles in the polystyrene microparticle aqueous solution (5-1) can be observed; Step 3: Input 980nm laser to form an evanescent field (1-4) at the end face of the optical fiber probe; Step 4: Then operate the microscope (2-4) to adjust the relative position of the polystyrene microparticle aqueous solution (5-1) on the slide to capture the polystyrene microparticles.

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