CN111899908A - Micro-nano particle manipulator based on capillary optical fiber - Google Patents

Micro-nano particle manipulator based on capillary optical fiber Download PDF

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CN111899908A
CN111899908A CN202010890984.0A CN202010890984A CN111899908A CN 111899908 A CN111899908 A CN 111899908A CN 202010890984 A CN202010890984 A CN 202010890984A CN 111899908 A CN111899908 A CN 111899908A
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optical fiber
fiber
micro
capillary
core
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邓洪昌
王瑞
罗中岳
苑立波
张文涛
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Guilin University of Electronic Technology
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Guilin University of Electronic Technology
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/006—Manipulation of neutral particles by using radiation pressure, e.g. optical levitation

Abstract

The invention provides a micro-nano particle manipulator based on a capillary optical fiber. The method is characterized in that: the fiber laser comprises a wavelength-adjustable laser (1), a single-core fiber (2), a coreless fiber (3) and a capillary fiber (4). The invention designs a unique structure, the single-core optical fiber, the coreless optical fiber and the capillary optical fiber are sequentially fused and welded and then connected into a whole, and the beam is divided by utilizing the diverging action of the coreless optical fiber on the beam and the conical transition region formed by the hot melting and collapsing of the capillary optical fiber. Due to the divergence of the light beam, the hollow light beam transmitted in the tubular cladding can form a plurality of strong convergence points in the air hole or near the fiber end after being reflected and refracted, so that a plurality of micro-nano particles are captured. And finally, the functions of storing, oscillating and transporting a plurality of micro-nano particles are realized by utilizing the characteristic that the positions of a plurality of convergent points can move axially when the wavelength is changed. The invention can be used for screening, capturing and directionally ejecting biological cells, nanoclusters, medium particles and the like.

Description

Micro-nano particle manipulator based on capillary optical fiber
(I) technical field
The invention relates to a micro-nano particle control device based on single optical fiber integration. The optical fiber micro particle screening device is mainly used for screening, capturing, detecting, oscillating, ejecting and the like of micro particles such as biomolecules, biological cells, nanoclusters, colloidal particles, medium particles and the like, and belongs to the technical field of optical fibers.
(II) background of the invention
Conventional optical tweezers are usually constructed based on an optical microscope system, which focuses a laser beam through a microscope objective lens, and uses a gradient force field near the focusing center to form an optical trap for capturing and manipulating tiny particles. The traditional optical tweezers are mature in technology, but the structure is complex, the flexibility is lacked, the size is large, the price is high, an optical trap moving system is complex, and the requirement on operation skill is high. Therefore, an optical waveguide optical tweezers technical scheme is proposed, and tiny particles are captured by means of a plurality of waveguide channels on the same material substrate [ Chinese patent CN1740831A ], and in view of the defects that the optical waveguide optical tweezers end has large volume and large preparation difficulty, the optical fiber optical tweezers technology is further developed [ Optics Letters,1993,18(21):1867-9, and Optics Express,2006,14(25):12510-6 ]. The optical tweezers are simple in structure and can be made into a micro probe form, and the optical traps and the operation thereof are separated from the optical microscope system, so that the optical traps are flexible to operate, and the system has high degree of freedom.
Optical fiber connection technology is one of the most basic techniques in the field of optical fiber applications. The connection of optical fibers refers to the joining together of two fiber end faces. The essential requirement for the connection is to maximize the transition of light energy from the input fiber to the receiving fiber. In addition to low connection loss and high return loss, the optical fiber connection technology also requires stable performance and sufficient mechanical strength when the ambient temperature changes. Precise mechanical and optical design and tooling is therefore required to ensure high precision matching of the two fiber ends.
The optical fiber is used for realizing three-dimensional capture operation on particles, and the tip of the optical fiber needs to be specially processed, and the specific processing methods are a fusion tapering method [ Optics Express,14(25): 12510-. The common objective of the different processing methods is to be able to construct a suitable tapered end of the fiber to enable the construction of a large gradient optical trapping field.
Patent publication No. CN1963583A discloses a method for manufacturing a fiber needle with parabolic microstructure by fusion-drawing one end of a segment of optical fiber. Coupling laser into the other end of the optical fiber, and forming a converged light field with the diameter of less than 1 micron waist spot at the front end of the optical fiber needle after the laser is emitted from the optical fiber needle, so that a stable three-dimensional light potential well can be formed, and single-fiber optical tweezers are realized; the Chinese invention patent with the publication number of CN101118300 provides a small-core-diameter ultra-high numerical aperture cone optical fiber optical tweezers and a manufacturing method thereof. The optical fiber is processed by a small-core-diameter ultrahigh-numerical-aperture optical fiber, and the optical fiber end of the optical fiber is ground into a cone shape. The divergent light field formed by the large numerical aperture of the tip of the optical fiber can form a larger light field gradient force potential well, thereby overcoming the dead weight of particles and realizing the three-dimensional capture of the single optical fiber of the tiny particles; in order to further control the attitude of the captured tiny particles, the chinese patent application publication No. CN101149449 also discloses a dual-core fiber optical tweezers; the invention patent with publication number CN101339274A provides a hollow capillary fiber optical tweezers with annular core layer, and an air pressure adjusting device is connected in the air hole to store and manipulate micro particles.
In order to expand the structure and the function of an optical fiber device, the invention carries out unique design on an optical fiber structure, realizes the division of the light beam by utilizing the diverging effect of the coreless optical fiber on the light beam and the conical transition region formed by the hot melting and collapsing of the capillary optical fiber, and forms a strong focused light beam with a plurality of convergent points on the optical axis in an air hole or near the fiber end after the hollow light beam transmitted in the tubular cladding of the capillary optical fiber is reflected and refracted, thereby simultaneously capturing a plurality of micro-nano particles. And the positions of a plurality of capture points are regulated and controlled by using the wavelength, and finally, the functions of storage, oscillation and ejection of the micro-nano particles are realized. The design of the invention not only enables the optical fiber optical tweezers device to be more miniaturized and integrated, but also provides a brand new thought for manufacturing the capillary optical fiber optical tweezers device and further capturing and operating the micro-nano particles.
Disclosure of the invention
The invention aims to provide a single optical fiber integrated device which realizes the splitting of light beams by utilizing a tapered transition region after a coreless optical fiber and a capillary optical fiber are fused and implements stable light capture and light manipulation on a plurality of micro-nano particles.
The purpose of the invention is realized as follows:
the micro-nano particle control device consists of a wavelength-adjustable laser, a single-core optical fiber, a coreless optical fiber and a capillary optical fiber. The wavelength tunable laser comprises a data input end and different wavelength output ends, a single-core optical fiber comprises a fiber core and a cladding, a coreless optical fiber comprises a cladding, and a capillary optical fiber comprises an air hole and a tubular cladding. The single-core optical fiber, the coreless optical fiber and the capillary optical fiber are sequentially fused and welded and then connected into a whole, and a conical transition area is formed at a welding point of the coreless optical fiber and the capillary optical fiber due to hot melting and collapse of an air hole. When the guided light wave in the core of the single-core optical fiber forms a hollow light beam through the divergence of the coreless optical fiber and the division of the conical transition region, the length of the coreless optical fiber can be accurately controlled so that the two parts of light beams can be fully divided and spread to the fiber end. And then, after being reflected and refracted, the hollow light beam transmitted in the tubular cladding of the capillary optical fiber forms a strong convergent light beam with a plurality of convergent points on the optical axis in the air hole or near the fiber end, so that three-dimensional light capture of a plurality of micro-nano particles at a plurality of light trap positions is realized. When the wavelength of light waves introduced into the single-core optical fiber is periodically regulated and controlled by using the wavelength-adjustable laser, the axial positions of a plurality of convergent points formed by strongly converging light beams in the capillary optical fiber are correspondingly changed, and the function of storage or periodic oscillation of a plurality of micro-nano particles captured near the fiber end can be realized.
Micro-nano particles with special structures are adopted, such as one of dielectric materials, biological materials or other transparent materials. Optionally, the material of the micro-nano particles can also be a mixed or laminated material of a transparent material and a non-transparent material. The particles with the structure can respond to the change of the light wavelength, namely, the phenomenon of Fano resonance or surface plasmon resonance exists. Fanoresence (Fanorresonance) is a scattering resonance phenomenon that produces an asymmetric line shape, and interference between background and resonant scattering produces an asymmetric line shape. The interference between the background and the resonant scattering produces an asymmetric line shape. The lineshape of the Fano resonance results from interference of two scattering amplitudes, one scattering for the continuum state (associated with background) and the other excitation for the discrete state (associated with resonance). The energy of the resonance state must be in the energy range of the continuous state, and the effect is thatShould it be generated. Near resonance energy, the amplitude of background scatter is generally very gentle with energy; however, the amplitude and phase of the resonant scattering change relatively quickly, resulting in asymmetry. Background scattering dominates when the energy is far from the resonance energy. Energy around resonance energy 2resIn the range of (3), the amplitude phase of the resonance scattering is different by pi. It is this sharp change in phase that results in an asymmetric line shape. The total cross-section σ of the Fano-proven scattering is of the following form:
Figure BDA0002656984930000031
whereinresThe peak width of the resonance energy, q is the Fano variable, representing the amplitude ratio between the resonance scattering and the direct (background) scattering.
Surface plasmon resonance, abbreviated as SPR. It means that evanescent wave and plasma wave will resonate when they meet at the interface of medium, and the reflected light intensity will be greatly reduced when they resonate. Energy is transferred from photons to surface plasmons, and most of the energy of incident light is absorbed by the surface plasmon waves, causing the energy of reflected light to be drastically reduced.
Fano resonance or surface plasmon resonance phenomenon, that is, the direction of resultant force applied to the micro-nano particles generates unusual forward and backward phenomena in the axial direction, which are closely related to the wavelength of light waves and appear as assisted capture and directional ejection of the particles in particle capture. By utilizing the mechanism, when the light wave with the specific wavelength is introduced into the micro-nano particle manipulator based on the capillary optical fiber, the positive radiation pressure of the strong focusing light beam formed by converging the light wave near the fiber end on the micro-nano particles is larger than the negative gradient force, and the micro-nano particles are ejected out according to the propagation direction of the strong focusing light beam under the action of the optical resultant force, so that the transport function of the micro-nano particles is realized.
The base angle theta of the fiber end cone of the capillary optical fiber meets the following relation:
θ≥arcsin(nm/n1) (2)
wherein n ismIs the refractive index of the environment surrounding the fiber end of the optical fiber, n1Is the refractive index of the capillary fiber tube cladding. When the condition is met, the light beam introduced into the capillary fiber meets the condition of total reflection when passing through the cone, so that the light beam is not leaked and is totally reflected to the end face of the fiber, and then the two parts of light beam are strongly converged at the fiber end to generate an optical trap capable of capturing micro-nano particles. Optionally, a metal film (reflective film) may be additionally plated in the grinding or tapering region of the truncated cone, and the taper angle is not limited, so that the light beam is collected more effectively.
The feasibility of the micro-nano particle manipulation device based on the capillary optical fiber is analyzed, and theoretical analysis results are shown in fig. 5(a) - (b). (a) The figure shows a two-dimensional plane optical field diagram of a single mode fiber, a coreless fiber and a capillary fiber which are connected and are used for transmitting light to the single mode fiber, and from the figure, we can see that a segment from 800um to 1000um in the z direction has a plurality of light intensity maximum values which represent the positions of a plurality of strong focus points, thereby capturing a plurality of micro-nano particles. When a wavelength tunable laser is used to modulate the optical field, the longitudinal optical trapping force curves of particles with the same radius at different positions in the 800um to 1000um section are shown in the graph (b), and the distance of deviation of each curve from the reference line represents the longitudinal optical trapping force applied to the particle at such wavelength. When the light-transmitting wavelength is 980nm, the multi-optical trap region is positioned near 925um, and the optical trapping force is larger and the trapping range is smaller at the moment; when the light passing wavelength is 1130nm, the multi-optical trap region is near 938um, and the optical trapping force is moderate and the trapping range is moderate; when the light-passing wavelength is 1280nm, the multi-trap region is in the vicinity of 958um, and the light trapping force is small at this time, and the trapping range is large. The device has different longitudinal optical trapping force for particles with different radiuses at the same position, and when the radius of the particles is smaller, the optical trapping force is smaller, and the trapping efficiency is higher; when the particle radius is larger, the light trapping force is larger, and the trapping efficiency is lower; when the radius of the micro-particles is too large, the multi-optical trap area is not enough to capture micro-nano particles, and the particles are pushed out of the air holes of the capillary fiber under the combined action of optical resultant force.
The micro-nano particle manipulator based on the capillary optical fiber can further comprise:
1. the single-core optical fiber is one of a single-mode optical fiber, a few-mode optical fiber or a multi-mode optical fiber, and the shape of the fiber core can be as follows: one of circular, annular, triangular, rectangular, or other polygonal shapes.
2. The coreless fiber can also be a step-index multimode fiber or a graded-index multimode fiber.
3. The air hole shape of the capillary optical fiber can be as follows: one of a circle, a regular triangle, a square, or other regular polygon, and the shape of the tubular cladding may be one of a circle, a square, or other regular polygon.
4. The conical surface of the fiber end of the conical frustum can directly carry out total reflection on the conduction light wave in the tubular cladding, and a layer of metal reflecting film can be additionally plated to enhance the total reflection effect.
The manufacturing method of the micro-nano particle manipulator based on the capillary optical fiber comprises the following steps:
two rotatable optical fiber presss from both sides and is used for two fixed fusion optical fibers (single core fiber, centreless optic fibre, capillary optic fibre) of treating respectively in the optical splicer, and the optical fiber cutting knife is used for cutting two fusion optical fibers of treating and forms the fiber end face that supplies the butt fusion respectively, and fiber end face positioning unit is used for showing the structure of fiber end face, and the fiber end face butt fusion of two fusion optical fibers of treating is in the same place in the fiber fusion unit. Manufacturing a conical frustum fiber end of a capillary fiber: the first method comprises the following steps: the capillary optical fiber is fixed by an optical fiber clamp, then the fiber end is placed on a grinding disc, the optical fiber clamp and the optical fiber grinding disc can rotate around respective central axes, and the cone frustum fiber end with different opening angles is prepared by controlling the included angle between the optical fiber and the normal line of the disc surface of the grinding disc. The second method comprises the following steps: and placing the optical fiber on an optical fiber tapering machine, drawing the optical fiber into a proper taper length, and cutting the optical fiber at a proper position in a tapering area to form a truncated cone fiber end with an arc-shaped conical surface.
The invention has the advantages that the defects of the prior art are overcome, the beam is divided by utilizing the diverging effect of the coreless fiber on the beam and the conical transition region formed by the hot melting and collapsing of the capillary fiber, and the hollow beam transmitted in the tubular cladding of the capillary fiber can form a strong focused beam with a plurality of convergent points on the optical axis in the air hole or near the fiber end after being reflected and refracted, thereby simultaneously capturing a plurality of micro-nano particles. And the positions of a plurality of capture points are regulated and controlled by using the wavelength, and finally, the functions of storage, oscillation and ejection of the micro-nano particles are realized. The whole device is small in structure and strong in integration, can rotate at any angle or translate at a long distance, and is strong in operability. The unique design not only enables the optical fiber optical tweezers device to be more miniaturized and integrated, but also provides a brand new thought for manufacturing the capillary optical fiber optical tweezers device, and enables the capillary optical fiber optical tweezers device to have wide application value in the fields of biomedical research, particle transport and the like.
(IV) description of the drawings
Fig. 1 is a schematic structural diagram of a micro-nano particle manipulator based on a capillary fiber. The wavelength tunable laser comprises a wavelength tunable laser 1, a single-core optical fiber 2, a coreless optical fiber 3 and a capillary optical fiber 4.
Fig. 2(a) is a schematic diagram of an optical fiber fusion splicer splicing optical fibers in respective lengths. The device comprises a single-core optical fiber 201, a coreless optical fiber 202, a capillary optical fiber 203, a movable clamping device 204, a clamping device 205 and a welding unit 206. FIG. 2(b) is a flow chart of a fusion splicing process of optical fibers. The device consists of four parts, namely optical fiber cutting, optical fiber end face cleaning, angular positioning and optical fiber welding.
FIG. 3(a) is a schematic diagram of a truncated cone fiber end with an arc-shaped taper surface formed by tapering. Consists of a CMOS camera 301, a left-hand taper platform 302, a heating platform 303, a right-hand taper platform 304, a heating system 305, fiber alignment, a taper system 306, a fiber image detection system 307, a hardware system manipulation platform 308, a fiber image 309 and a computer manipulation system 310. Fig. 3(b) is a schematic structural view of a truncated cone fiber end with an arc-shaped taper surface.
FIG. 4 is a schematic diagram of a conical fiber end prepared by a grinding cone. The device consists of a fiber clamp 401, a capillary fiber 402 and a grinding disc 403. Fig. 4(b) is a schematic structural view of a truncated cone fiber end.
Fig. 5 is a diagram illustrating a feasibility analysis result of a micro-nano particle manipulator based on a capillary fiber.
FIG. 6 shows the refractive index profile when a coreless fiber is replaced with a multimode fiber. Respectively, the schematic structural diagrams of the step-index multimode fiber and the graded-index multimode fiber.
Fig. 7 shows a schematic diagram of different core shape structures of a single-core optical fiber. (a) The figure shows a schematic structure of a triangular core shape. (b) The figure shows a schematic structure of a square core. (c) The figure shows a schematic structure of the core in the shape of a ring. (d) The figure shows a schematic structure of the case where the core has a polygonal shape.
Fig. 8 shows the structure of different air holes and the shape of the tubular cladding of the capillary fiber. (a) The figure shows the structure of the air hole in square shape and the tubular cladding in round shape. (b) The figure shows the structure of the square air hole and the square tubular cladding.
Fig. 9 is an application structure schematic diagram of a micro-nano particle manipulator based on a capillary fiber.
(V) detailed description of the preferred embodiments
The invention will be further elucidated by way of example with reference to the drawing.
Referring to fig. 1 and 9, in the embodiment of the present invention, a single-core fiber, a coreless fiber and a capillary fiber are sequentially fusion-welded and then connected into a whole, and a tapered transition region is formed at a welding point of the coreless fiber and the capillary fiber due to air hole hot melting and collapse. When the guided light wave in the core of the single-core optical fiber forms a hollow light beam through the divergence of the coreless optical fiber and the division of the conical transition region, the length of the coreless optical fiber can be accurately controlled so that the two parts of light beams can be fully divided and spread to the fiber end. And then, after being reflected and refracted, the hollow light beam transmitted in the tubular cladding of the capillary optical fiber forms a strong convergent light beam with a plurality of convergent points on the optical axis in the air hole or near the fiber end, so that three-dimensional light capture of a plurality of micro-nano particles at a plurality of light trap positions is realized. When the wavelength of light waves introduced into the single-core optical fiber is periodically regulated and controlled by using the wavelength-adjustable laser, the axial positions of a plurality of convergent points formed by strongly converging light beams in the capillary optical fiber are correspondingly changed, and the function of storage or periodic oscillation of a plurality of micro-nano particles captured near the fiber end can be realized.
Micro-nano particles with special structures are adopted, such as one of dielectric materials, biological materials or other transparent materials. Optionally, the material of the micro-nano particles can also be a mixed or laminated material of a transparent material and a non-transparent material. The particle with the structure can respond to the change of the optical wavelength, namely, the phenomenon of Fano resonance or surface plasma resonance exists, namely, the phenomenon that the direction of resultant force borne by the micro-nano particle generates unusual forward and reverse directions in the axial direction is closely related to the wavelength of the optical wave, and the phenomenon is represented as assisted capture and directional ejection of the particle in particle capture. By utilizing the mechanism, when the light wave with the specific wavelength is introduced into the micro-nano particle manipulator based on the capillary optical fiber, the positive radiation pressure of the strong focusing light beam formed by converging the light wave near the fiber end on the micro-nano particles is larger than the negative gradient force, and the micro-nano particles are ejected out according to the propagation direction of the strong focusing light beam under the action of the optical resultant force, so that the transport function of the micro-nano particles is realized.
The manufacturing process of the particle manipulation device based on the fusion of the coreless fiber and the capillary fiber can be divided into the following two steps (see fig. 2-4):
and step 1, welding the optical fibers (see figure 2). All be equipped with on optic fibre cutting knife, optic fibre terminal surface positioning unit and the optical fiber fusion unit with the shape or the size assorted setting element of rotatable optic fibre clamp, can realize the quick installation of rotatable optic fibre clamp and optic fibre cutting knife, optic fibre terminal surface positioning unit or optical fiber fusion unit and keep the mounted position fixed through the setting element. The positioning element can be a positioning hole, a positioning groove or a fixing position, etc. The optical fiber cutter automatically fixes the position of the rotatable optical fiber clamp through the fixing piece, and the consistency of the cutting position every time is ensured. The optical fiber end face positioning unit is quickly installed and fixed with the rotatable optical fiber clamp through the fixing piece, and the accuracy and the operation consistency of the observed optical fiber end face structure are ensured. The fixing piece on the optical fiber welding unit 206 can fix two rotatable optical fiber clamps at the same time, and the two rotatable optical fiber clamps can be arranged symmetrically left and right, so that the two installed rotatable optical fiber clamps and two optical fibers to be welded fixed by the two rotatable optical fiber clamps can be welded quickly and accurately;
step 2, fiber end micromachining (the step can be prepared by two methods): the fiber is tapered (see fig. 3). After a coating layer of an optical fiber is removed, the optical fiber is fixed on an optical fiber clamp, a control system drives a left hand electric control displacement platform 302 and a right hand electric control displacement platform 304 which bear the optical fiber, the optical fiber is sent to a field range of a CMOS camera 301, the optical fiber is focused in the field range through an automatic focusing system to obtain a clear image 309, and the image can be displayed through a computer control system 310. And calculating the geometric parameters and pose information of the optical fiber to serve as feedback quantity, and adjusting the micro-motion execution device with five dimensions of left and right hands to realize the alignment of the optical fiber waveguide and the heating device. The melting area is sent to the waveguide alignment position by the driving electric heating device 308 to be heated, the optical fiber is stretched at a certain speed by the left and right manual-control displacement platforms, and after the tapering is finished, the optical fiber is cut by the optical fiber cutting knife at the central point, and finally the fiber end of the cone frustum with the arc-shaped conical surface is formed. The fiber ends were ground (see fig. 4). Fixing a capillary optical fiber 402 by using an optical fiber clamp 401, then placing the fiber end on a grinding disc 403, wherein the optical fiber clamp and the optical fiber grinding disc are respectively connected with a direct current motor to drive the optical fiber clamp and the optical fiber grinding disc to rotate around respective central axes; the capillary optical fiber is kept to form a fixed included angle theta with the normal line of the disc surface of the grinding disc, and the conical fiber end with the opening angle theta can be ground through the autorotation of the optical fiber clamp and the grinding disc.
Alternatively, the refractive index profile when the coreless fiber is replaced with the multimode fiber may be one of a step-index multimode fiber and a graded-index multimode fiber, as shown in fig. 6(a) - (b).
Optionally, the single-core optical fiber is one of a single-mode optical fiber, a few-mode optical fiber, or a multi-mode optical fiber, and the shape of the core may be: one of a circle, a ring, a triangle, a rectangle, or other polygon, as shown in fig. 7(a) - (c).
Alternatively, the air hole shape of the capillary fiber may be: one of a circle, a regular triangle, a square, or other regular polygon, and the shape of the tubular cladding may be one of a circle, a square, or other regular polygon, as shown in fig. 8(a) - (b).
In addition, the light beam with the best convergence effect can be obtained by controlling the length of the coreless fiber and the opening angle of the conical fiber end of the capillary fiber, so that micro-nano particles can be captured and controlled more accurately.
The invention is further illustrated below with reference to specific examples.
Step 1, device preparation: a device formed by fusion-bonding 10 sets of single-core optical fibers, coreless optical fibers, and capillary optical fibers was manufactured according to the optical fiber manufacturing method of the embodiment. The length of the coreless fiber and the opening angle of the truncated cone in 10 groups of devices are different. A wavelength-adjustable laser with a tail fiber and a common single-mode fiber are adopted for light injection (see the figure 1, the figure 2 and the figure 9);
step 2, fiber end micromachining (the step can be prepared by two methods): tapering the optical fiber: the fiber end structure of the truncated cone with the arc-shaped conical surface is manufactured according to the optical fiber tapering method of the embodiment (see fig. 3), and the fiber end of the optical fiber is ground: manufacturing a truncated cone fiber end structure according to the optical fiber end grinding method of the embodiment (see fig. 4);
step 3, storage and oscillation functions of the micro-nano particles (see fig. 1 and 9): the method is characterized in that a laser with adjustable wavelength is adopted to introduce light beams with fixed optical power into a fiber core of a single-core optical fiber, after the light beams reach the joint of the single-core optical fiber and the coreless optical fiber, the light beams are divided by utilizing the divergence effect of the coreless optical fiber on the light beams and a conical transition region formed after the capillary optical fiber is melted, and the length of the coreless optical fiber can be accurately controlled to enable the two parts of the light beams to be fully separated and spread to a fiber end. And then, after being reflected and refracted, the hollow light beam transmitted in the tubular cladding of the capillary optical fiber forms a strong convergent light beam with a plurality of convergent points on the optical axis in the air hole or near the fiber end, so that three-dimensional light capture of a plurality of micro-nano particles at a plurality of light trap positions is realized. When the wavelength of light waves introduced into the single-core optical fiber is periodically regulated and controlled by using the wavelength-adjustable laser, the axial positions of a plurality of convergent points formed by strongly converging light beams in the capillary optical fiber are correspondingly changed, and the function of storage or periodic oscillation of a plurality of micro-nano particles captured near the fiber end can be realized. Sequentially replacing each group of prepared devices, observing and recording the capturing effect of the devices on a plurality of particles, and obtaining the length of the coreless optical fiber and the opening angle of the cone frustum when the capturing effect is optimal;
step 4, directional ejection function of the micro-nano particles (see the figure 1 and the figure 9): micro-nano particles with special structures are adopted, such as one of dielectric materials, biological materials, other transparent materials, transparent material and non-transparent material mixed or laminated materials. When the particles with the structure are in an optical field with variable optical wavelength, a phenomenon of Fano resonance or plasma resonance exists, when the optical wave with the specific wavelength is introduced into the micro-nano particle manipulator based on the capillary optical fiber, the positive radiation pressure of the strong focused light beam formed by converging the particles near the fiber end on the micro-nano particles is larger than the negative gradient force, and the micro-nano particles are pushed out of the air hole according to the propagation direction of the strong focused light beam under the action of the optical resultant force. According to actual needs, the optical fiber optical tweezers device is integrally moved, and the micro-nano particles are directionally ejected to different channels of the micro-fluidic multi-channel 8 according to a preset path, so that the device is utilized to complete accurate optical manipulation on the micro-nano particles.

Claims (6)

1. A micro-nano particle manipulator based on capillary optical fibers is characterized in that: the wavelength tunable laser comprises a wavelength tunable laser (1), a single-core optical fiber (2), a coreless optical fiber (3) and a capillary optical fiber (4), wherein the wavelength tunable laser (1) comprises a data input end (101) and different wavelength output ends (102), the single-core optical fiber (2) comprises a fiber core (201) and a cladding (202), the coreless optical fiber (3) comprises a cladding (301), the capillary optical fiber (4) comprises an air hole (401) and a tubular cladding (402), the single-core optical fiber, the coreless optical fiber and the capillary optical fiber are sequentially fused and welded and then connected into a whole, and a conical transition region (403) is formed at a welding point (7) of the coreless optical fiber (3) and the capillary optical fiber (4) due to hot melting and collapse of the air hole (401); when a conduction light wave in a fiber core (201) of a single-core optical fiber (2) passes through a coreless optical fiber (3) and a conical transition region (403), the conduction light wave is divided into hollow light beams, and then the hollow light beams transmitted in a tubular cladding (402) of a capillary optical fiber (4) are reflected and refracted to form strong convergent light beams (5) with a plurality of convergent points on an optical axis in an air hole or near the fiber end, so that a plurality of micro-nano particles (6) are subjected to light capture at the same time; when the wavelength of light waves introduced into the single-core optical fiber (2) is periodically regulated and controlled by using the wavelength-adjustable laser (1), the axial positions of a plurality of convergent points formed by strongly converging light beams (5) in the capillary optical fiber (4) can be periodically changed, and the storage or periodic oscillation function of micro-nano particles (6) captured near the fiber end can be realized; if the micro-nano particles (6) have surface plasma resonance or Fano resonance phenomenon to the light wave with the specific wavelength, when the light wave with the specific wavelength is introduced into the micro-nano particle manipulator based on the capillary optical fiber, the positive radiation pressure of the strong focusing light beams (5) formed by converging near the fiber end to the micro-nano particles (6) is larger than the negative gradient force, the micro-nano particles (6) are ejected out according to the propagation direction of the strong focusing light beams (5) under the action of the optical resultant force, and the transportation function of the micro-nano particles (6) is realized.
2. The capillary fiber-based micro-nano particle manipulator according to claim 1, which is prepared by the following steps: (1) and (3) hot melting welding: the single-core optical fiber, the coreless optical fiber and the capillary optical fiber are sequentially welded together by a welding wire welding machine; (2) the fiber end of the capillary optical fiber can adopt a truncated cone fiber end structure, and the truncated cone fiber end is manufactured as follows: the first method comprises the following steps: fixing the capillary optical fiber by using an optical fiber clamp, then placing the fiber end on a grinding disc, wherein the optical fiber clamp and the optical fiber grinding disc can rotate around respective central axes, and preparing the cone frustum fiber end with different opening angles by controlling the included angle between the optical fiber and the normal line of the disc surface of the grinding disc; the second method comprises the following steps: and placing the optical fiber on an optical fiber tapering machine, drawing the optical fiber into a proper taper length and taper angle, and cutting the optical fiber at a proper position in a tapering area to form a truncated cone fiber end with an arc-shaped taper surface.
3. The frustoconically shaped fiber end of claim 2, wherein: the conical surface of the fiber end of the conical frustum can directly carry out total reflection on the transmitted light wave, and a layer of metal reflecting film can be additionally plated to enhance the total reflection effect.
4. The micro-nano particle manipulator based on the capillary optical fiber according to claim 1, which is characterized in that: the single-core optical fiber is one of a single-mode optical fiber, a few-mode optical fiber or a multi-mode optical fiber, and the shape of the fiber core can be as follows: one of circular, annular, triangular, rectangular, or other polygonal shapes.
5. The micro-nano particle manipulator based on the capillary optical fiber according to claim 1, which is characterized in that: the coreless fiber can also be a step-index multimode fiber or a graded-index multimode fiber.
6. The micro-nano particle manipulator based on the capillary optical fiber according to claim 1, which is characterized in that: the air hole shape of the capillary optical fiber can be as follows: one of a circle, a regular triangle, a square, or other regular polygon, and the shape of the tubular cladding may be one of a circle, a square, or other regular polygon.
CN202010890984.0A 2020-08-29 2020-08-29 Micro-nano particle manipulator based on capillary optical fiber Pending CN111899908A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113687470A (en) * 2021-08-30 2021-11-23 桂林电子科技大学 Single-fiber optical tweezers based on air defect microcavity

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113687470A (en) * 2021-08-30 2021-11-23 桂林电子科技大学 Single-fiber optical tweezers based on air defect microcavity

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