A WGM-based single-fiber near-field optical tweezers

Abstract

This invention belongs to the field of near-field optical tweezers technology, specifically relating to a single-fiber near-field optical tweezers based on a WGM (Whole Magnetic Gland) structure. It includes a hollow silica microsphere, a laser source, and an optical fiber unit. The hollow silica microsphere comprises a shell region and a hollow region located inside the shell region, with the refractive index of the shell region being higher than that of the hollow region. The laser source emits laser light, refracting it into the shell region at an incident angle of 90°, generating an evanescent field on the outer surface of the hollow silica microsphere. The laser emitted by the source has wavelengths of 980 nm and 532 nm. This invention combines near-field optical tweezers with a WGM structure, achieving the function of capturing nanoscale particles by total internal reflection on the inner surface of the microsphere and forming an evanescent field on the outer surface. Furthermore, by changing the wavelength of the incident laser, the nanoparticles can be captured at different locations.

Description

Technical Field

[0001] This invention belongs to the field of near-field optical tweezers technology, specifically relating to a single-fiber near-field optical tweezers based on WGM. Background Technology

[0002] Optical trapping theory is based on the radiative force of light. Quantum theory posits that light is a stream of photons with both mass and momentum, moving at the speed of light. The interaction between the light radiation field and an object causes the object to be subjected to the radiative force of light. Laser trapping utilizes the kinetic effects of lasers to achieve the stable trapping of particles.

[0003] Because optical tweezers use an invisible beam of light to capture particles without mechanical contact, they do not cause mechanical damage. Furthermore, all mechanical parts of the optical tweezers are located at a distance much larger than the size of the captured object, making it a "remote" operation that hardly affects the particle's surrounding environment. Combined with the light-penetrating properties of biological particles, optical tweezers technology is particularly suitable for living biological particles. The manipulation of particles by optical tweezers is not rigid; it allows for real-time measurement of minute inter-particle forces during operation. Therefore, optical tweezers also act as a force probe or force sensor in particle interactions. This makes optical tweezers not only a robotic hand for manipulating tiny particles but also an ideal tool for studying the static and dynamic mechanical properties of microparticles.

[0004] With the maturation 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 the propagation field and near-field optical tweezers based on the evanescent field. According to near-field optics theory, near-field and far-field are only relative terms. The near field is defined as: a freely propagating radiation field and an evanescent wave that is confined to the surface of a material and decays rapidly with distance. Because the evanescent wave is a non-uniform 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 China University of Technology, 2014.).

[0005] Through continuous research, the study of surface plasmons has gradually emerged, providing a new perspective on the generation of evanescent fields. By using metal nanostructures to excite surface plasmons, a powerful evanescent field can be generated.

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

[0007] During this period, the application of evanescent field optical tweezers in the biomedical field gradually emerged. Researchers used its ability to manipulate biomolecules and cells at the micron and nanoscale to carry out a series of experiments.

[0008] So far, among all optical tweezers that utilize the near-field principle, the basic principle is to use the total internal reflection principle of lasers to form an evanescent field at the interface, thereby achieving the purpose of generating a near-field optical field.

[0009] As the technology matures, the applications of near-field optical tweezers are constantly expanding, including bioimaging, manipulation of nanomaterials, and regulation of chemical reactions. Researchers have achieved high-sensitivity and high-precision particle capture by improving device design.

[0010] In 1992, Satoshi Kawata and 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 total internal reflection of a prism to manipulate microparticles. When the incident angle of s-polarized light is greater than the critical angle, a 6.8 μm diameter particle moves at a high speed of 8 μm / s along the prism surface under the influence of the evanescent field formed by total internal 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 generated by total internal reflection of a prism alone is relatively weak, and it is difficult to eliminate the influence of the external environment on particle capture.

[0011] To overcome the limitations of diffraction optics on gradient forces and improve the accuracy of optical tweezers trapping, in 2004, Kwak et al. (Kwak E S, Onuta TD, Amarie D, et al. Optical trapping with integrated near-field apertures[J]. The Journal of Physical Chemistry B, 2004, 108(36):13607-13612.) proposed using laser illumination of nanopores on a metal film substrate to generate a rapidly decaying evanescent field, thereby achieving the trapping of even smaller microspheres. Nanopore near-field optical tweezers can capture nanoscale microspheres, providing a platform for subwavelength biophotonic sensors and ultra-sensitive measurements of particle dynamics in enclosed environments. However, they cannot capture individual nanoparticles because all apertures simultaneously trap the particle after light transmission.

[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 high numerical aperture microscope objective to focus a ring-shaped hollow beam, resulting in total internal reflection at the glass-solution interface, thus achieving the trapping of polystyrene microspheres with a diameter of 2 μm. Because multiple beams interfere at the focal point, the intensity of the evanescent field is enhanced, and the size of the axial trapping is reduced. Focused evanescent field optical tweezers can solve the problem of difficulty in controlling the distance between the probe and the sample due to the small range of the evanescent field, and can also overcome the instability of trapping caused by the plasma resonance thermal effect of metal probe-type optical tweezers.

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

[0014] In summary, each of the above-mentioned methods for generating evanescent fields to form ingress traps has its own advantages and disadvantages. For example, while these methods can achieve the function of capturing nanoscale particles, they cannot change the position of the captured nanoparticles according to the needs. Summary of the Invention

[0015] The purpose of this invention is to provide a single-fiber near-field optical tweezers based on WGM (Wave Governing Mode), which combines near-field optical tweezers with WGM (Wave Governing Mode) structure. By performing total internal reflection on the inner surface of the spherical microcavity, an evanescent field is formed on the outer surface, thereby achieving the function of capturing nanoscale particles. Furthermore, by changing the wavelength of the incident laser, the nanoparticles can be captured at different locations.

[0016] The specific technical solution adopted by this invention is as follows:

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

[0018] Hollow silica microspheres, wherein the hollow silica microspheres include a shell region and a hollow region located inside the shell region, and the refractive index of the shell region is higher than that of the hollow region;

[0019] A laser source is used to emit laser light. The laser source refracts the laser light into the spherical shell region at an incident angle of 90°, 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 a laser 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, the silica hollow microsphere is fixedly connected to the center position of the end of the eccentric optical fiber, the eccentric fiber is provided with an eccentric core, the distance from the center position of the eccentric optical fiber to the eccentric core is the optical fiber eccentricity, and the radius of the silica hollow microsphere is the same as the optical fiber eccentricity.

[0023] Furthermore, it also includes:

[0024] Electric micromanipulator;

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

[0026] A CCD, mounted on the underside of the microscope stage, is used to acquire and record the light field image on the stage.

[0027] The computer and microscope are electrically connected for displaying images acquired by the CCD.

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

[0029] The eccentric fiber and the hollow silica microspheres form a special optical fiber.

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

[0031] The special optical fiber is mounted on an electric micromanipulator.

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

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

[0034] Step 2: Control the electric micromanipulator to make the fiber optic probe with special optical fiber containing hollow silica microspheres appear in the microscope's field of view, and adjust the focus so that the microscope can observe the fiber optic probe. Then, take a polystyrene aqueous solution on a glass slide, place it on the microscope slide, and continue to adjust the microscope's focus to ensure that the fiber optic probe and the polystyrene particles in the polystyrene aqueous solution can be observed.

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

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

[0037] The technical effects achieved by this invention are as follows:

[0038] This invention discloses a single-fiber near-field optical tweezers based on WGM (Wave Governing Mode). Structurally, it combines near-field optical tweezers with a WGM structure. By performing total internal reflection on the inner surface of a spherical microcavity, an evanescent field is formed on the outer surface, thereby capturing microparticles and forming a novel fiber tweezers structure. In terms of particle size capture, compared to other optical tweezers that can only capture micrometer-scale particles, this fiber tweezers can capture nanometer-scale particles. Furthermore, the evanescent field generated by this method can capture multiple nanoparticles at a single location, forming a self-assembled structure. By changing the wavelength of the incident laser, the aim is to capture nanoparticles at different locations. Attached Figure Description

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

[0040] Figure 2 This is the present invention. Figure 1 A magnified view of a section at point A in the middle;

[0041] Figure 3 This is the present invention. Figure 1 A magnified view of a section at point B in the middle;

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

[0043] Figure 5 This is a schematic diagram of the misaligned welding of a common single-mode fiber and an eccentric fiber according to the present invention.

[0044] Figure 6 This is a schematic diagram of the light interaction force at the evanescent field on the outer surface of the microspheres of the present invention;

[0045] Figure 7 This is a schematic diagram of how the evanescent field of this invention captures multiple nanoparticles to form a self-assembly.

[0046] Figure 8 This is a schematic diagram illustrating how the particle capture position shifts when the incident laser wavelength is changed according to the present invention.

[0047] The attached diagram lists the components represented by each number as follows:

[0048] 1-1. Off-core fiber optic cable; 1-1-1. Off-core fiber core; 1-2. UV-curable adhesive; 1-3. Hollow microspheres; 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 source; 2-7. 980nm laser source; 2-8. Motorized micromanipulator; 2-9. Ordinary single-mode optical fiber; 3-1. Laser beam; 3-2. Single-mode optical fiber connector; 3-3. Off-core optical fiber connector; 5-1. Polystyrene aqueous solution; 5-2. Nanoparticles; 6-1. White dashed line; 6-2. Black solid line; 6-3. Evanescent field. Detailed Implementation

[0049] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0050] Example 1:

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

[0052] Among them, the hollow silica microspheres 1-3 include a shell region 1-3-1 and a hollow region 1-3-2 located inside the shell region 1-3-1, and the refractive index of the shell region 1-3-1 is higher than that of the hollow region 1-3-2.

[0053] The laser source is used to radiate laser light into the spherical shell region 1-3-1. Preferably, the laser light is refracted into the spherical shell region 1-3-1 at an incident angle of 90°. Since the refractive index of the middle spherical shell region 1-3-1 is higher than that of the hollow region 1-3-2, the laser light refracted into the spherical shell region 1-3-1 will propagate around the spherical shell region 1-3-1 without being refracted out again, thereby forming a stable corridor mode. An evanescent field 1-4 is generated on the outer surface of the silica hollow microsphere 1-3. Since the light field density of the evanescent field 1-4 is small, smaller particles can be captured by the combined action of gradient force and scattering force. This structure is sufficient to capture nanoscale microparticles.

[0054] Here, the wavelength of the laser emitted by the laser source can be changed, but its wavelength should satisfy the condition that when it undergoes total internal reflection within the hollow region 1-3-2 and returns to the origin, interference enhancement occurs.

[0055] Preferably, the laser light source emits laser wavelengths of 980nm and 532nm, where the 980nm laser provides energy to form a light field, and the 532nm laser mainly serves as an indicator of the light field.

[0056] One end of the optical fiber unit is connected to the laser source, and the hollow silica microspheres 1-3 are fixedly connected to the other end of the optical fiber unit. At this time, the laser emitted by the laser source is transmitted through the optical fiber unit, and through the fixed positional relationship between the hollow silica microspheres 1-3 and the optical fiber unit, the laser can be simply and stably refracted into the spherical shell region 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 this technical solution, an eccentric optical fiber line 1-1 is preferred. A silica hollow microsphere 1-3 is fixedly connected to the center of the end of the eccentric optical fiber line 1-1. An eccentric core body 1-1-1 is provided inside the eccentric optical fiber line 1-1, so that the eccentric core body 1-1-1 and the silica hollow microsphere 1-3 are eccentrically set. In order to reduce optical loss, a suitable outer radius of silica hollow microsphere 1-3 needs to be selected. In this technical solution, the distance from the center of the eccentric optical fiber line 1-1 to the eccentric core body 1-1-1 is the optical fiber eccentricity. The radius of the silica hollow microsphere 1-3 needs to be approximately the same as the optical fiber eccentricity so that the laser emitted from the eccentric core body 1-1-1 is refracted into the spherical shell region 1-3-1 with an incident angle of 90°.

[0058] like Figure 1 As shown, the method of fixing the silica hollow microspheres 1-3 is disclosed here. A UV-curable adhesive 1-2 is provided at the end of the eccentric fiber 1-1, and the silica hollow microspheres 1-3 are bonded to the end of the eccentric fiber 1-1 by the UV-curable adhesive 1-2, thereby facilitating the connection between the eccentric fiber 1-1 and the silica hollow microspheres 1-3. The refractive index of the UV-curable adhesive 1-2 and the refractive index of the silica hollow microspheres 1-3 are 1.459 and 2.2, respectively.

[0059] Example 2:

[0060] like Figures 1-8 As shown, this embodiment discloses in detail the acquisition mechanism of single-fiber near-field optical tweezers. The acquisition mechanism of single-fiber near-field optical tweezers mainly involves laser light emitted from the eccentric fiber 1-1, which then enters the hollow silica microsphere 1-3. At a certain point on the outer surface of the spherical shell region 1-3-1, a fleeting field 1-4 is formed by total internal reflection. The optical force of the fleeting field 1-4 at that point is as follows... Figure 6 As shown. Since it is formed by total internal reflection of light, its existence distance is limited; the farther away from the outer surface of the silica hollow 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 towards the direction of the light beam, and a gradient force perpendicular to the outer surface of the silica hollow microspheres 1-3 and pointing towards the silica hollow microspheres 1-3, thereby stably binding the particles in the liquid environment.

[0061] Furthermore, the mechanism of evanescent field 1-4 can be explained from the perspective of total internal reflection. When light is incident from an optically denser medium n1 to an optically less dense medium n2, and the angle of incidence is greater than the critical angle... When the incident wave energy is completely reflected back into the optically denser medium, a surface wave, or evanescent wave, still exists near the interface surface in the optically less dense medium.

[0062] The position of the particle-trapping region 6-3 generated within the evanescent field 1-4 on the outer surface of the silica hollow microspheres 1-3 changes with the wavelength. Figure 8 As can be seen, with decreasing the wavelength of the incident laser, the reflected light path inside the silica hollow microspheres 1-3 changes from the white dashed line 6-1 to the black solid line 6-2. Simultaneously, the position of the trapping region 6-3, which captures the nanoparticles 5-2, also changes, thereby achieving stable trapping of the studied nanoparticles 5-2 at different positions on the outer surface of the silica hollow microspheres 1-3.

[0063] The microparticles self-assemble within the evanescent field 1-4, where they are trapped by optical trapping forces, thereby capturing multiple nanoparticles 5-2. Figure 7 As shown, due to the definite light trapping force of its light field, the nanoparticles 5-2 trapped by its light field will accumulate together to form a specific shape that cannot be changed.

[0064] This technical solution combines near-field optical tweezers and WGM (Wave Governing Mode) structure. By performing total internal reflection on the inner surface of the spherical microcavity, an evanescent field 1-4 is formed on the outer surface, thereby capturing microparticles and forming a relatively novel fiber optic tweezers structure. In terms of the scale of captured particles, compared with other optical tweezers that can only capture micron-sized particles, this fiber optic tweezers can achieve the function of capturing nano-sized particles. At the same time, the evanescent field 1-4 generated by this method can capture multiple nanoparticles 5-2 at one location of the evanescent field 1-4, forming a self-assembled structure. By changing the wavelength of the incident laser, the nanoparticles 5-2 can be captured at different locations.

[0065] Example 3:

[0066] like Figure 1-3 As shown, this embodiment further discloses the structure of a WGM-based single-fiber near-field optical tweezers based on embodiment 1. 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 microscope 2-4;

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

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

[0070] Here, the eccentric fiber 1-1 and the silica hollow microspheres 1-3 form a special optical fiber 2-3. At the same time, the special optical fiber 2-3 may also include a UV-curable adhesive 1-2.

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

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

[0073] The computer 2-1 and microscope 2-4 are electrically connected for displaying images acquired by the CCD 2-5.

[0074] Example 4:

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

[0076] Step 1: Cut approximately 2m of eccentric fiber 1-1. Use wire strippers to remove about 2cm of the coating from one end of the eccentric fiber 1-1. Wipe the fiber end with an alcohol-soaked cloth to ensure the end face is clean and free of contamination. Use a fiber optic cleaver to cut the end face as flat as possible. Then, vertically attach the eccentric fiber 1-1 to the three-position adjustment frame of the motorized micromanipulator 2-8 and manipulate it under microscope 2-4. First, use microscope 2-4 to locate appropriately sized hollow silica microspheres 1-3, then use the motorized micromanipulator... 2-8 Manipulate the eccentric fiber 1-1 to apply a small amount of UV-curable adhesive 1-2, ensuring that the UV-curable adhesive 1-2 is present at the fiber end of the eccentric fiber 1-1. Then move it back above the found silica hollow microsphere 1-3 and use the adhesive properties of the UV-curable adhesive 1-2 to adsorb the silica hollow microsphere 1-3. Finally, use a UV lamp to irradiate the UV-curable adhesive 1-2 at the junction of the eccentric fiber 1-1 and the silica hollow microsphere 1-3. The UV-curable adhesive 1-2 will solidify in about 1 minute. The fiber optic tweezers of this structure can then be completed.

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

[0078] Step two: The other end of the eccentric fiber 1-1, eccentric fiber connector 3-3 and single-mode fiber connector 3-2, are treated to make them smooth and clean. A 2mm section of eccentric fiber 1-1 is cut, and approximately 2cm of the coating is stripped from one end using wire strippers. The treated ordinary single-mode fiber 2-9 and eccentric fiber 1-1 are then cut using a fiber optic cleaver to ensure clean and flat end faces. Next, the fibers are spliced ​​using a laboratory-specific fiber optic fusion splicer. First, the automatic program of the fusion splicer is used for initial alignment of the two fiber end faces. Then, the mode is switched to manual, and the motor adjustment option of the fusion splicer is selected. The ordinary single-mode fiber 2-9 is manually moved until its core aligns with the core of the eccentric fiber 1-1. At this point, the "Complete" button is pressed, and the system performs the welding. This completes the misaligned fusion splicing of the two fibers. After the misaligned welding is completed, the output light field and the welding point are observed under microscope 2-4.

[0079] Here, the cladding diameter of ordinary single-mode fiber 2-9 and eccentric fiber 1-1 is uniformly 125μm. As long as the diameters of ordinary single-mode fiber 2-9 and eccentric fiber 1-1 are the same, consistent transmission can be guaranteed.

[0080] Example 5:

[0081] This embodiment discloses the method of using single-fiber near-field optical tweezers based on embodiment 3. The method 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, 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 fiber optic probe with silica hollow microspheres 1-3 on the special optical fiber 2-3 appears in the field of view of the microscope 2-4 for observation, and adjust the focus so that the structure of the fiber optic probe can be clearly observed by the microscope 2-4. Then, use a micropipette to draw a small amount of polystyrene microparticle aqueous solution 5-1 onto a glass slide and place it on the glass slide of the microscope 2-4. Continue to adjust the focus of the microscope 2-4 to ensure that the fiber optic probe and the polystyrene microparticles in the polystyrene microparticle aqueous solution 5-1 are observed.

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

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

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

[0087] Here, the fiber optic probe is a special fiber 2-3 with one end containing hollow silica microspheres 1-3.

[0088] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A single-fiber near-field optical tweezers based on WGM, characterized in that: include: Hollow silica microspheres (1-3), wherein the hollow silica microspheres (1-3) include a shell region (1-3-1) and a hollow region (1-3-2) located inside the shell region (1-3-1), and the refractive index of the shell region (1-3-1) is higher than that of the hollow region (1-3-2); Laser source, the laser source being used to emit laser light; An optical fiber unit, one end of which is connected to a laser source, and the hollow silica microspheres (1-3) are fixedly connected to the other end of the optical fiber unit; The laser source refracts the laser into the spherical shell region (1-3-1) at an incident angle of 90°. The laser refracted into the spherical shell region (1-3-1) propagates along the spherical shell region (1-3-1) to form a corridor pattern and generates an evanescent field (1-4) on the outer surface of the silica hollow microsphere (1-3). Nanoparticles at different locations are captured by changing the wavelength of the incident laser.

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

3. The single-fiber near-field optical tweezers based on WGM according to claim 2, characterized in that: The optical fiber unit is an eccentric optical fiber (1-1). The silica hollow microsphere (1-3) is fixedly connected to the center of the end of the eccentric optical fiber (1-1). An eccentric fiber core (1-1-1) is provided inside the eccentric optical fiber (1-1). The distance from the center of the eccentric optical fiber (1-1) to the eccentric fiber core (1-1-1) is the optical fiber eccentricity. The radius of the silica hollow microsphere (1-3) is the same as the optical fiber eccentricity.

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

5. The single-fiber near-field optical tweezers based on WGM according to claim 4, characterized in that: The refractive indices of the UV-curable adhesive (1-2) and the silica hollow microspheres (1-3) are 1.459 and 2.2, respectively.

6. A single-fiber near-field optical tweezers based on WGM according to any one of claims 3-5, characterized in that: Also includes: Electric micromanipulator (2-8); A microscope (2-4) having a stage mounted on it; The CCD (2-5) is installed on the underside of the stage of the microscope (2-4) and is used to acquire and record the light field image on the stage. The computer (2-1) and microscope (2-4) are electrically connected for displaying images acquired by the CCD (2-5). The laser source includes a 532nm laser source (2-6) and a 980nm laser source (2-7). The 980nm laser emitted from the 980nm laser source (2-7) forms a light field on the stage of the microscope (2-4), and the 532nm laser emitted from the 532nm laser source (2-6) serves as an indicator for the light field. The eccentric fiber line (1-1) and the silica hollow microspheres (1-3) form a special optical fiber (2-3). The 532nm laser source (2-6) and the 980nm laser source (2-7) are connected by ordinary single-mode optical fiber (2-9) and special optical fiber (2-3); The special optical fiber (2-3) is mounted on the electric micromanipulator (2-8).

7. The single-fiber near-field optical tweezers based on WGM according to claim 6, characterized in that: The cladding diameter of the ordinary single-mode fiber (2-9) and the eccentric fiber (1-1) is uniformly 125 μm.

8. A method for using a WGM-based single-fiber near-field optical tweezers, employing the WGM-based single-fiber near-field optical tweezers described in claim 6, characterized in that: Includes the following steps: Step 1: Take 500nm polystyrene microspheres into a reagent bottle, then add an appropriate amount of distilled water, seal and place in an ultrasonic vibration device to ensure that the polystyrene microspheres are fully dissolved in water, and vibrate for 3 minutes; Step 2: Control the electric micromanipulator (2-8) so that the fiber optic probe with silica hollow microspheres (1-3) on the special optical fiber (2-3) appears in the field of view of the microscope (2-4), and adjust the focus so that the fiber optic probe can be observed by the microscope (2-4). Then take the polystyrene microparticle aqueous solution (5-1) on the glass slide and place it on the glass slide of the microscope (2-4). Continue to adjust the focus of the microscope (2-4) to ensure that the fiber optic probe and the polystyrene microparticles in the polystyrene microparticle aqueous solution (5-1) can be observed. Step 3: Input a 980nm laser to form an evanescent field (1-4) on the end face of the fiber optic 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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