CN112230424B

CN112230424B - Optical tweezers

Info

Publication number: CN112230424B
Application number: CN202011151883.8A
Authority: CN
Inventors: 谭航彬; 金尚忠; 姜丽; 金怀洲
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2020-10-22
Filing date: 2020-10-22
Publication date: 2022-11-25
Anticipated expiration: 2040-10-22
Also published as: CN112230424A

Abstract

The invention discloses optical tweezers which comprise a continuous spectrum light source, a single mode fiber, a pulse fiber, a step multimode fiber, a micro manipulator for controlling a capturing tweezer head, a capturing tweezer head at the tail end of the step multimode fiber, a metal reflector plate, an optical microscope, a sealed dimming system and a pulse light source, wherein the sealed dimming system is arranged at the joint of the single mode fiber and the step multimode fiber, the metal reflector plate is arranged on the pulse fiber, the metal reflector plate is used for controlling the rotation of the metal reflector plate by controlling pulse light to excite lamb waves on the surface of the pulse fiber, the metal reflector plate is used for reflecting laser emitted from the single mode fiber, and the laser injection angle of the step multimode fiber can be accurately controlled, so that the light trapping force can be quantitatively controlled.

Description

Optical tweezers

Technical Field

The invention belongs to the field of precise medical scientific research experimental equipment, and particularly relates to multimode fiber optical tweezers based on lamb wave control.

Background

The optical tweezers use the gradient force formed by the spatial variation of the light field intensity to stably capture the particles at the strongest position of the light field, namely the focal position of the light beam. When the laser beam moves, the particles can be driven to move together, and the precise control of the particles is realized. The optical tweezers technology is gradually applied to the biological and medical research fields, such as cell, virus and bacteria manipulation, because the optical tweezers have the characteristics of no damage, non-invasiveness and the like to the manipulated particles, the size of the particles captured by the optical tweezers is usually in the micrometer to nanometer order, and the size of biological cells and macromolecules is also usually in the dozen nanometers to dozens of micrometers. The traditional optical tweezers are constructed based on an optical microscope system, and focus laser beams through an optical microscope objective lens, and capture and operate particles by forming an optical trap through a gradient force field near a focusing center. The main structure of the traditional optical tweezers system is a high-precision optical microscope, the instrument is large in size, the system is complex and heavy, the price is high, the operation interface is complex, the requirement on operation skills is high, the degree of freedom of movement of a sample is small, and the capture range of the optical tweezers is limited.

Patent CN201710752028.4 discloses "step multimode optical tweezers based on oblique optical annular optical field", the invention injects light to multimode optical fiber obliquely through single mode fiber, the light in multimode optical fiber is transmitted forward in a spiral manner in the form of oblique light, and forms an annular optical field on the end surface of the fiber core of multimode optical fiber, the annular light is totally reflected and converged in the truncated cone structure of the end surface of the step multimode optical fiber, so as to generate strong optical trapping force, and can capture single cells and flying-rising micro-droplets.

The dimming part in patent CN201710752028.4 is implemented by injecting laser into a step-variable multimode fiber at a certain angle through a single mode fiber, and the angle of injected light is controlled by oblique incidence adjusting devices of the single mode fiber and the multimode fiber, which causes the dimming part to be exposed in the environment, and is very easily interfered by the external environment, resulting in reduced stability of the optical tweezers.

At present, traditional multimode fiber optical tweezers based on oblique light annular light field screens the cell through the angle that injects laser into multimode fiber when manual regulation single mode fiber, reaches the effect of control cell, but because this structure is not fixed and expose in the air, consequently stability is relatively poor, receives external factor's interference easily, and all need carry out the debugging of angle at every turn the operation, and is very inconvenient, has influenced the popularization and the application of multimode fiber optical tweezers.

Disclosure of Invention

In order to solve the problems of stability and convenience of a dimming part of the optical fiber optical tweezers, the invention provides a lamb wave dimming method, and the lamb wave based on the pulse light excitation is controlled, so that the angle of oblique incidence of laser to a multimode fiber is accurately controlled, and the change of the incidence angle can be realized without moving the positions of a single mode fiber and the multimode fiber.

The invention provides multimode fiber optical tweezers based on lamb wave control, which comprise a continuous spectrum light source, a single mode fiber, a step multimode fiber, a capturing tweezer head at the tail end of the step multimode fiber and a sealing dimming system, wherein light generated by the continuous spectrum light source is injected into the single mode fiber, the sealing dimming system is arranged at the joint of the single mode fiber and the step multimode fiber, the single mode fiber obliquely injects light into the step multimode fiber through the sealing dimming system, the light in the step multimode fiber is spirally transmitted forwards in an oblique light mode and forms an annular light field, and the annular light is totally reflected and converged at the capturing tweezer head end face at the tail end of the step multimode fiber to generate a light trap for capturing, so that single cells and flying-rise micro-droplets can be captured.

The sealed dimming system comprises a shell, a pulse optical fiber and a metal reflector plate, wherein the pulse optical fiber and the metal reflector plate are arranged at the joint of the single-mode optical fiber and the step-step multimode optical fiber, and the pulse optical fiber penetrates through the shell or one end of the pulse optical fiber is inserted and fixed in the shell; the metal reflector plate is arranged in the shell, and a metal reflector plate is asymmetrically arranged on the pulse optical fiber by using the probe and is in physical contact with the pulse optical fiber; the pulse optical fiber is connected to a pulse light source, the lamb waves on the surface of the pulse optical fiber are excited by controlling the pulse light, the rotation of the metal reflector plate is controlled, the metal reflector plate is used for reflecting the laser emitted from the single-mode optical fiber, and the adjustment of an optical path is realized. .

The reflected light reflected by the metal reflector plate is incident into the step multimode fiber at a specific angle, the oblique light transmitted by the step multimode fiber forms an annular light field at the tail end of the step multimode fiber, and the annular light is totally reflected and converged at the end face of the capturing tweezer head at the tail end of the step multimode fiber to generate strong light trapping force, so that the operations of capturing, carrying, screening and the like of cells are realized.

Furthermore, one end parts of the single mode fiber and the step multimode fiber are inserted and fixed in the shell.

Further, the reflecting surface of the metal reflector plate faces to the single mode fiber and the step multimode fiber, and the reverse surface of the metal reflector plate is asymmetrically placed on the pulse fiber.

Further, the single-mode fiber is a 980nm single-mode fiber, the numerical aperture is 0.2, the diameter of a 980nm corresponding mode field is 4.2 mu m, the diameter of a core is 3.6 mu m, the diameter of a cladding is 125 mu m, and the front end of the single-mode fiber is coupled with a 980nm light source through a coupling lens.

Further, the optical tweezers also comprise a micro manipulator for controlling the capturing tweezers head, and the micro manipulator for controlling the capturing tweezers head is used for adjusting the position of the end section of the step-type multimode fiber.

Further, the optical tweezers further comprise an optical microscope for observing the optical traps generated by the capturing tweezers heads, and the captured cells can be observed under the optical microscope.

Compared with the prior art, the invention has the following benefits:

1. by controlling the pulse quantity of the pulse light, the laser injection angle of the step multimode fiber can be accurately controlled, so that the light trapping force can be quantitatively controlled, and the detection of some characteristic values of the captured cells is achieved;

2. the dimming system can be carried out in a closed space, the single-mode optical fiber and the multimode optical fiber do not need to be moved, external vibration and the influence of ambient light can be avoided, and the stability of the optical tweezers system is improved

3. The optical path does not need to be adjusted when the optical tweezers are used each time, so that the operation of the optical tweezers is more convenient and faster.

Drawings

FIG. 1 is a schematic diagram of an optical tweezers system;

FIG. 2 is a schematic diagram of a dimming system;

FIG. 3 is a schematic diagram of the light path of the dimming system;

FIG. 4 is a schematic cross-sectional view of a dimming system;

wherein, 1: continuous spectrum light source, 2: single-mode optical fiber, 3: pulsed optical fiber, 4: step multimode fiber, 5: controlling a micro manipulator of the capturing forceps head, 6: capturing tweezer head at the end of the step multimode fiber, 7: metal reflective sheet, 8: optical microscope, 9: sealed dimming system, 10: a pulsed light source.

Detailed Description

The present invention will be described in detail with reference to the specific embodiments shown in the drawings, which are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to the specific embodiments are included in the scope of the present invention.

As shown in fig. 1, the optical tweezers comprises a continuous spectrum light source 1, a single mode fiber 2, a step multimode fiber 4, a micro manipulator 5 for controlling the capturing tweezer head, a capturing tweezer head 6 at the tail end of the step multimode fiber, an optical microscope 8, a sealed dimming system 9 and a pulse light source 10, wherein light generated by the continuous spectrum light source 1 is coupled and injected into the single mode fiber 2, the single mode fiber 2 injects light to the step multimode fiber 4 obliquely through the sealed dimming system 9, light in the step multimode fiber 4 is spirally and forwardly transmitted in an oblique light mode to form an annular light field, the annular light is emitted and converged at the end face of the capturing tweezer head 6 at the tail end of the step multimode fiber, a focal region is converged to generate strong light trapping force, and single cells and flying-rise micro droplets can be captured.

As shown in fig. 2, the sealed dimming system 9 is disposed at the connection between the single mode fiber 2 and the step-multimode fiber 4, and includes a housing 91 with a certain sealing property, the pulse fiber 3, and the metal reflector 7. The dark room is arranged inside the shell 91, so that the interference of ambient light can be prevented, one end parts of the single mode fibers 2 and the step multimode fibers 4 are inserted into the shell 91, and the parts of the single mode fibers 2 and the step multimode fibers 4 inside the shell 91 are fixed relative to the shell 91, so that the movement of the angle of emergent light of the single mode fibers 2 and the angle of receiving light of the step multimode fibers 4 is avoided. The pulse fiber 3 may penetrate the housing, and may also have one end inserted into the housing 91 like the single mode fiber 2 and the step-multimode fiber 4, and the pulse fiber 3 is connected to the pulse light source 10, so that the pulse light source 10 increases the pulse light signal. The metal reflector 7 is disposed inside the housing 7, and the metal reflector 7 has physical contact with the pulse fiber 3, specifically, the reflective surface of the metal reflector 3 is disposed facing the single mode fiber 2 and the step-up multimode fiber 4, and the reverse surface is asymmetrically disposed on the pulse fiber 3. In one embodiment, the length of each side of the metal reflector 7 is in the order of 10 microns and the thickness is 30-80 nm, at which the metal reflector 7 and the pulsed optical fiber 3 are mainly van der waals forces at rest and thus can adhere to the fiber without falling off.

Referring to fig. 3, when the pulse light passes through the pulse fiber 3, lamb waves are generated on the surface of the pulse fiber 3, the lamb waves on the surface of the pulse fiber 3 propagate along the metal reflector 7 to the left and right, and the two lamb waves are excited and propagate along the two sides of the metal reflector 7 with the same initial amplitude.

As shown in fig. 4, they are reflected back after reaching the boundary of the metal reflector 7, and the asymmetry of the structure of the metal reflector 7 on the fiber results in an asymmetry of the propagation length.

Therefore, when these two lamb waves are reflected from the edge of the metal reflection sheet 7, their effects cannot be cancelled out. Therefore, the lamb waves reflected from the shorter side (with less attenuation) dominate the lamb waves reflected from the longer side (with greater attenuation), so that the lamb waves in a certain direction drive the metal reflector plate 7 to rotate around the pulse optical fiber 3, and under the drive of continuous optical pulses, the metal reflector plate 7 rotates step by step, the rotation of the metal reflector plate is in a quasi-continuous state, and the rotation direction depends on the initial relative position of the metal reflector plate 7 on the pulse optical fiber 3. Since the resulting lamb wave propagates primarily in a direction perpendicular to the fiber axis, it is caused to rotate about the pulsed fiber 3 rather than to move translationally along the fiber axis. In the case where the metal reflecting sheet 7 is moved to the right (i.e., the metal reflecting sheet 7 is placed on top of the pulse optical fiber 3 and the center of the metal reflecting sheet 7 is moved to the right half of the pulse optical fiber 3), that is, the metal reflecting sheet 7 is rotated counterclockwise and the metal reflecting sheet 7 is rotated clockwise when moved to the left. If the metal reflective sheet 7 is placed on the pulse optical fiber 3 in a symmetrical configuration, it does not rotate. The rotating direction is determined by the asymmetry of the metal reflector 7 relative to the left and right parts of the pulse optical fiber 3, and is independent of the gravity of the metal reflector 7.

The angle that each fixed pulsed light can drive metal reflector plate 7 to rotate is fixed, so long as the quantity of the pulse light of control through pulsed light source 10 just can control the rotation angle of metal reflector plate 7, when continuous laser shines on metal reflector plate 7, through metal reflector plate 7 reflection entering step multimode fiber 4, the injection angle of incident light alright in order to obtain control like this to reach the effect of adjusting luminance. Meanwhile, the dimming system is in a sealed environment, and the interference of the external environment is avoided.

The metal reflector plate 7 is driven by lamb waves to move leftwards or rightwards, and meanwhile, the metal reflector plate 7 rotates due to the radial adhesive force. Therefore, the movement of the metal reflector 7 driven by one pulse does not cause the change of the relative contact area of the metal reflector 7 and the optical fiber. When the metal reflector 7 is driven by a series of pulses, the cooperation between the relative movement and the rotation ensures that the metal reflector 7 can rotate around the pulse optical fiber 3 quasi-continuously without being separated from the pulse optical fiber 3.

In summary, the dimming principle of the sealed dimming system 9 is as follows: when pulse light is transmitted in light, lamb waves are generated on the surface of the pulse optical fiber 3, the lamb waves can drive the metal reflector plate 7 on the surface of the light to rotate without enabling the metal reflector plate 7 to fall off, the rotating speed of the metal reflector plate 7 is in linear proportion to the repetition frequency of the light pulses, the rotating angle of the metal reflector plate 7 is kept unchanged due to each light pulse, laser emitted by the single-mode optical fiber 2 irradiates the metal reflector plate 7 and is reflected by the metal reflector plate 7, and reflected light is emitted into the step-type multimode optical fiber 4 at a specific angle. In this embodiment, the rotation angle of one light pulse is 0.018 °, and the radius of the pulse fiber 3 is 800 to 1000nm.

The reflected light reflected by the metal reflector plate 7 is incident into the step multimode fiber 4 at a specific angle, the oblique light transmitted by the step multimode fiber 4 forms an annular light field at the tail end of the step multimode fiber 4, and the annular light is totally reflected and converged at the end face of the capturing tweezer head 6 at the tail end of the step multimode fiber 4 to generate strong light trapping force. Can be observed under an optical microscope 8, and the position of the end section of the step multimode fiber can be adjusted by using a micro manipulator 5 for controlling the capturing forceps head, thereby realizing the operations of capturing, transporting, screening and the like of cells.

In addition, the rotating angle of the metal reflector plate 7 is controlled by the pulse number, so that incident light rays with different incident angles can be incident into the step multimode fiber 4, the focus of a converged light beam generated by the forceps head 6 can be adjusted, the adjustment convenience of the annular light field optical forceps is greatly improved, and the application value of the optical forceps is improved.

In this embodiment, the continuous spectrum light source 1 is a 980nm laser, which uses a butterfly semiconductor, and combines with an optical fiber FBG to ensure stable spectral wavelength and continuously adjustable power, and after coupling to a 980nm single-mode fiber, the maximum output power is greater than 400mW.

In this embodiment, the single mode fiber 2 is a 980nm single mode fiber, the numerical aperture is 0.2, the 980nm mode field diameter is 4.2 μm, the core diameter is 3.6 μm, the cladding diameter is 125 μm, and the front end is coupled with the 980nm continuous spectrum light source 1 through a coupling lens.

In this embodiment, the step-index multimode fiber 4 is a glass-clad step-index multimode fiber, and has a numerical aperture of 0.22, a fiber core diameter of 105 μm, and a cladding diameter of 125 μm.

In this embodiment, the capturing tweezer head 6 is manufactured by processing the tail end of the step multimode fiber 4 by using a bare fiber grinding technology.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. An optical tweezers, characterized in that: the device comprises a continuous spectrum light source, a single mode fiber, a step multimode fiber, a capturing tweezer head at the tail end of the step multimode fiber and a sealing dimming system, wherein light generated by the continuous spectrum light source is coupled and injected into the single mode fiber, the sealing dimming system is arranged at the joint of the single mode fiber and the step multimode fiber, the single mode fiber injects light to the step multimode fiber in an oblique incidence mode through the sealing dimming system, light in the step multimode fiber is spirally and forwards transmitted in an oblique light mode to form an annular light field, the annular light is emitted and converged at the end face of the capturing tweezer head at the tail end of the step multimode fiber to generate a light trap for capturing, and the sealing dimming system comprises a shell, a pulse fiber and a metal reflector plate; the pulse optical fiber penetrates through the shell or one end of the pulse optical fiber is inserted and fixed in the shell; the metal reflector plate is arranged in the shell and is in physical contact with the pulse optical fiber; the pulse optical fiber is connected to a pulse optical source, lamb waves on the surface of the pulse optical fiber are excited by control pulse light, the rotation of the metal reflector plate is controlled, and the metal reflector plate is used for reflecting laser emitted from the single-mode optical fiber to realize the adjustment of an optical path.

2. The optical tweezers of claim 1, wherein: the metal reflector plate is placed on the pulse optical fiber in an asymmetrical mode.

3. The optical tweezers of claim 1, wherein: the length of each side of the metal reflector plate is 10 microns, and the thickness of each side of the metal reflector plate is 30-80 nm.

4. The optical tweezers of claim 1, wherein: the angle of the single pulse light emitted by the pulse light source for driving the metal reflecting sheet to rotate is 0.018 degrees.

5. The optical tweezers of claim 1, wherein: one end parts of the single mode fiber and the step multimode fiber are inserted and fixed in the shell.

6. The optical tweezers of claim 5, wherein: the reflecting surface of the metal reflecting sheet faces to the single mode fiber and the step multimode fiber, and the reverse surface of the metal reflecting sheet is asymmetrically placed on the pulse fiber.

7. The optical tweezers of claim 1, wherein: the single mode fiber is a 980nm single mode fiber, the numerical aperture is 0.2, the diameter of a 980nm corresponding mode field is 4.2 mu m, the diameter of a core is 3.6 mu m, the diameter of a cladding is 125 mu m, and the front end of the single mode fiber is coupled with a 980nm light source through a coupling lens.

8. The optical tweezers of claim 1, wherein: the micro manipulator is used for controlling the capturing forceps head and is arranged at the position of the end section of the step multimode fiber.

9. The optical tweezers of claim 1, wherein: an optical microscope for observing the optical traps generated by the capturing tweezer heads is also included.