Optical Trapping and Three-Dimensional Manipulation Device for Light-Absorbing Particles in Air Based on Hollow Light

Abstract

The present invention discloses an optical trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light, which includes a laser, a hollow light generating unit, and a polarization beam splitter arranged in sequence, and also includes an illumination unit, a lateral trapping unit, and a vertical trapping unit; the lateral trapping unit includes a first deflecting mirror, and the vertical trapping unit includes a second deflecting mirror. By respectively rotating the first deflecting mirror and the second deflecting mirror arranged in the lateral trapping unit and the vertical trapping unit, the present invention realizes the two-dimensional rotation of the trapped particles in the lateral and vertical directions in a plane perpendicular to the propagation direction of the trapping laser, and the rotation direction is controllable, solving the problem in the prior art that the rotation direction of particles cannot be controlled at a low trapping power when trapping light-absorbing particles in air; in addition, since hollow light is used to trap light-absorbing particles, the trapping power can be as low as 25 mW, so the problem of excessive light energy trapped by the particles during two-dimensional rotation is also solved.

Description

Technical Field

[0001] The present invention belongs to the field of nonlinear optical applications, and relates to an optical trapping and three-dimensional manipulation device, specifically to an optical trapping and three-dimensional manipulation device for absorbing particles in air based on hollow light. Background Art

[0002] In recent years, with the increasing demand for in-situ analysis of air pollution particles, the optical trapping and manipulation of light-absorbing particles have attracted people's attention. Among them, high-precision three-dimensional optical manipulation is a challenging technology because the trapped particles need to be displaced to the focal position of the excitation laser for spectral analysis. Currently, the manipulation of particles along the z-direction (the propagation direction of the trapping laser) is usually achieved by changing the power of the trapping laser. However, this method of displacement requires a large power of the trapping laser. And due to the change in the power of the trapping laser, the scattered light on the particles also changes, thus interfering with the extraction of the spectral signal.

[0003] More seriously, for some particles with poor optical stability, their physical and chemical properties change with the change in the power of the irradiated light, so non-destructive analysis of the particles cannot be achieved. For the optical manipulation of trapped particles in the x-y plane (the plane perpendicular to the propagation direction of the trapping laser), there are mainly two methods. One is by using a focused optical trap and a conical ring optical trap diffracted from a circular aperture; the other is by using a new method combining a cylindrical lens and a circular diaphragm. And both of these methods have their own defects. Using a focused optical trap and a conical ring optical trap diffracted from a circular aperture can achieve continuous rotation of the light-absorbing particles, but the rotation direction of the particles cannot be controlled; while using the new method combining a cylindrical lens and a circular diaphragm, the power of the trapping laser cannot be lower than 100 mW, otherwise the particles are easily escaped from the trapping device, and it is also impossible to simultaneously achieve one-dimensional manipulation of the trapped particles and two-dimensional rotation (three-dimensional manipulation) of the particles. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an optical trapping and three-dimensional manipulation device for absorbing particles in air based on hollow light, which solves the technical problems in the prior art that the rotation direction of particles cannot be controlled at a low trapping power during the trapping of absorbing particles in air and that one-dimensional manipulation of the trapped particles and two-dimensional rotation cannot be achieved simultaneously.

[0005] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0006] An optical trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light, comprising a laser, a hollow light generating unit, and a polarization beam splitter arranged in sequence, and further comprising a lateral trapping unit, a vertical trapping unit, and an illumination unit; the lateral trapping unit is arranged in the P-light direction of the polarization beam splitter, the vertical trapping unit is arranged in the S-light direction of the polarization beam splitter, and the illumination unit is arranged in the opposite direction of the S-light of the polarization beam splitter;

[0007] The lateral trapping unit includes a first deflecting mirror; the vertical trapping unit includes a second deflecting mirror.

[0008] The present invention further has the following technical features:

[0009] Specifically, the lateral trapping unit further includes a second convex lens, a first sample cell, and a lateral image collection mechanism arranged in sequence; the vertical trapping unit further includes a third convex lens, a second sample cell, and a vertical image collection mechanism arranged in sequence.

[0010] Specifically, the lateral image collection mechanism includes a first microscopic objective lens, a first notch filter, and a first imaging structure fixedly connected in sequence; the vertical image collection mechanism includes a second microscopic objective lens, a second notch filter, and a second imaging structure fixedly connected in sequence.

[0011] Specifically, a third microscopic objective lens and a third imaging structure are fixedly connected to the upper side of the first sample cell in the vertical direction; a fourth microscopic objective lens and a fourth imaging structure are fixedly connected to the front side of the second sample cell in the horizontal direction.

[0012] Specifically, the first deflecting mirror and the second deflecting mirror are wedge prisms.

[0013] Specifically, the illumination unit includes a first convex lens and an incandescent lamp arranged in sequence on the lower side of the polarization beam splitter in the vertical direction.

[0014] Specifically, the hollow light generating unit is a cross-phase spatial beam modulation system or a spatial light modulator.

[0015] Specifically, the laser is a 532nm semiconductor continuous laser or an all-solid-state tunable titanium sapphire dye continuous laser.

[0016] Specifically, the first imaging structure, the second imaging structure, the third imaging structure, and the fourth imaging structure are CCD cameras, ICCD cameras, or CMOS cameras.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are: The present invention further has the following technical features:

[0018] (I) By separately rotating the first deflecting mirror and the second deflecting mirror provided in the horizontal capture unit and the vertical capture unit, the present invention realizes the two-dimensional rotation of the captured particles on the planes perpendicular to the propagation direction of the capture laser in the horizontal and vertical directions, and the rotation direction is controllable, solving the problem in the prior art that the rotation direction of the light-absorbing particles in the air cannot be controlled at a low capture power; in addition, since a hollow light is used to capture the light-absorbing particles, the capture power can be as low as 25 mW, so the problem of excessive capture light energy during the two-dimensional rotation of the microparticles is also solved.

[0019] (II) By changing the size of the hollow light, the present invention realizes the one-dimensional manipulation of the captured microparticles in the propagation direction of the capture laser; in addition, due to the addition of the deflecting mirror, the one-dimensional manipulation and the two-dimensional rotation of the captured microparticles are effectively combined, that is, the three-dimensional manipulation of the captured particles at the micron level in the vertical capture unit and the horizontal capture unit is realized, and the technical problem in the prior art that the one-dimensional manipulation and the two-dimensional rotation of the captured particles cannot be realized simultaneously is solved. Brief Description of the Drawings

[0020] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 is a rotation diagram of the captured particles in the horizontal device collected by the present invention on the plane perpendicular to the laser direction;

[0022] Figure 3 is a rotation diagram of the captured particles in the vertical device collected by the present invention on the plane perpendicular to the laser direction;

[0023] Figure 4 is a schematic diagram of the modulation of the laser power and the change of the hollow light size;

[0024] Figure 5 shows the linear fitting diagram of the modulation light power and the hollow light size;

[0025] Figure 6 Horizontal direction, relationship diagram between the hollow light size and the moving distance of the captured particles in the laser propagation direction;

[0026] Figure 7 Vertical direction, relationship diagram between the hollow light size and the moving distance of the captured particles in the laser propagation direction.

[0027] The meanings of the various labels in the figure are as follows: 1 - laser, 2 - hollow light generation unit, 3 - polarization beam splitter, 4 - horizontal capture unit, 5 - vertical capture unit, 6 - illumination unit;

[0028] 401 - The first deflection mirror, 402 - The second convex lens, 403 - The first sample cell, 404 - The lateral image collection mechanism, 405 - The third microscopic objective lens, 406 - The third imaging structure;

[0029] 40401 - The first microscopic objective lens, 40402 - The first notch filter, 40403 - The first imaging structure;

[0030] 501 - The second deflection mirror, 502 - The third convex lens, 503 - The second sample cell, 504 - The vertical image collection mechanism, 505 - The fourth microscopic objective lens, 506 - The fourth imaging structure;

[0031] 50401 - The second microscopic objective lens, 50402 - The second notch filter, 50403 - The second imaging structure;

[0032] 601 - The first convex lens, 602 - The incandescent lamp.

[0033] The following further elaborates on the specific content of the present invention in conjunction with embodiments. Detailed implementation mode

[0034] It should be noted that the reason for using a hollow beam in the present invention is as follows: When a beam of light irradiates the surface of an absorbent particle, the temperature of the irradiated surface of the particle increases, which further causes the thermal motion of the gas molecules attached to the particle surface to intensify. The gas molecules will bounce off the particle surface at a greater speed. Since the thermal motion of the gas molecules on the irradiated surface is greater than that on the unirradiated surface, a net force will be generated on the particle that points from the irradiated surface to the unirradiated surface under the combined action. For a hollow beam, the force acting on the particle surface can be expressed as:

[0035]

[0036] Among them, ρ α is the density of air, m α is the mass of an air molecule, B is the universal gas constant, T is the temperature of the particle surface, M is the molar mass of air molecules, and S is the area of the light irradiation region on the particle;

[0037] For irregular particles:

[0038]

[0039] γ is the specific heat ratio of the gas environment, P is the gas pressure, P * is the characteristic pressure, is the average velocity of gas molecules, P l is the effective power of the capture laser beam irradiating the particle, Δα = α1 - α2,

[0040] Under the combined action of gravity, F ΔT and F Δα the microparticles can be captured after the focal point; during the manipulation process, the resistance, gravity, F ΔT and F Δα can stably capture the microparticles during the manipulation process, so as to perform three-dimensional manipulation on the captured microparticles.

[0041] Therefore, using hollow light can stably capture microparticles and perform three-dimensional manipulation.

[0042] It should be noted that Figure 4 and Figure 5 illustrate that when the energy of the trapping laser (hollow light) remains unchanged, the linear change of the hollow light size can be effectively controlled.

[0043] It should be noted that all components in the present invention are, without special instructions, components known in the art.

[0044] The following gives specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solutions of this application fall within the protection scope of the present invention.

[0045] Embodiment:

[0046] This embodiment provides an optical trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light, as Figure 1 shown, which includes a laser 1, a hollow light generation unit 2, and a polarization beam splitter 3 arranged in sequence, and also includes a horizontal trapping unit 4, a vertical trapping unit 5, and an illumination unit 6; the horizontal trapping unit 4 is arranged in the P-light direction of the polarization beam splitter 3, the vertical trapping unit 5 is arranged in the S-light direction of the polarization beam splitter 3, and the illumination unit 6 is arranged in the opposite direction of the S-light of the polarization beam splitter 3;

[0047] The horizontal trapping unit 4 includes a first deflecting mirror 401; the vertical trapping unit 5 includes a second deflecting mirror 501.

[0048] In this embodiment, the function of the first deflecting mirror and the second deflecting mirror is to deflect the two hollow light beams obtained by the polarization beam splitter 3 by a certain angle, and by rotating the deflecting mirror, the hollow light beam after passing through the deflecting mirror also rotates around the optical axis.

[0049] In the above technical solution, by rotating the first deflection mirror and the second deflection mirror arranged in the horizontal capture unit and the vertical capture unit respectively, the two-dimensional rotation of the captured particles in the horizontal and vertical planes perpendicular to the propagation direction of the capture laser is realized, and the rotation direction is controllable, which solves the problem that the existing technology cannot control the rotation direction of the particles at low capture power when capturing light-absorbing particles in the air; in addition, since hollow light is used to capture light-absorbing particles, the capture power can be as low as 25mW, which also solves the problem of excessive capture light energy during the two-dimensional rotation of the particles.

[0050] As a preferred solution of this embodiment, the horizontal capture unit 4 also includes a second convex lens 402, a sample pool No. 1 403 and a horizontal image collection mechanism 404 arranged in sequence; the vertical capture unit 5 also includes a third convex lens 502, a sample pool No. 2 503 and a vertical image collection mechanism 504 arranged in sequence.

[0051] In this embodiment, the second convex lens 402 and the third convex lens 502 are used to focus the generated hollow light beam to form a light trap, wherein the focal lengths of the second convex lens and the third convex lens are both 45 mm; the No. 1 sample pool 403 and the No. 2 sample pool 503 are used to reduce the impact of airflow disturbances in the air when capturing particles.

[0052] As a preferred solution of this embodiment, the horizontal image collection mechanism 404 includes a first microscope objective lens 40401, a first notch filter 40402 and a first imaging structure 40403 fixedly connected in sequence; the vertical image collection mechanism 504 includes a second microscope objective lens 50401, a second notch filter 50402 and a second imaging structure 50403 fixedly connected in sequence.

[0053] In this embodiment, in the lateral image collection mechanism 404, the image of the captured particle is respectively passed through the first microscope objective lens, the light intensity is attenuated by the first notch filter, and the image is formed on the first imaging structure by adjusting the distance between the first microscope objective lens and the first imaging structure, as shown in FIG. Figure 2 As shown, the rotation direction of the particles is controllable; in the vertical image collection mechanism 504, the image of the captured particles is imaged by the second microscope objective lens, the light intensity is attenuated by the second notch filter, and the image is formed on the second imaging structure by adjusting the distance between the second microscope objective lens and the second imaging structure, as shown in FIG. Figure 3 As shown, the rotation direction of the particles is controllable.

[0054] As a preferred solution of this embodiment, a third microscope objective lens 405 and a third imaging structure 406 are fixedly connected to each other on the vertical upper side of the No. 1 sample pool 403; a fourth microscope objective lens 505 and a fourth imaging structure 506 are fixedly connected to each other on the horizontal front side of the No. 2 sample pool 503.

[0055] In this embodiment, the third microscope objective lens 405 and the fourth microscope objective lens 505 are used to collect the scattered light on the trapped particle. By adjusting the distance between the third microscope objective lens and the third imaging structure, the image is formed on the third imaging structure, as shown in Figure 6 shown; by adjusting the distance between the fourth microscope objective lens and the fourth imaging structure, the image is formed on the fourth imaging structure, as shown in Figure 7 shown. By combining the above imaging with Figure 2 and Figure 3 combined, it can be obtained that the three-dimensional manipulation of the trapped particle is realized in the present invention.

[0056] As a preferred solution of this embodiment, the first deflecting mirror 401 and the second deflecting mirror 501 are wedge prisms, and the rotation direction of the particle can be changed by rotating the wedge prism.

[0057] As a preferred solution of this embodiment, the illumination unit 6 includes a first convex lens 601 and an incandescent lamp 602 which are sequentially arranged on the vertical lower side of the polarization beam splitter 3.

[0058] In this embodiment, by adjusting the distances among the incandescent lamp, the first convex lens and the polarization beam splitter, illumination is provided for the fields of view of the horizontal image collection mechanism and the vertical image collection mechanism, so that the trapped particles can be observed. Among them, the focal length of the first convex lens is 30 mm.

[0059] As a preferred solution of this embodiment, the hollow light generating unit 2 is a cross-phase spatial beam modulation system or a spatial light modulator.

[0060] As a preferred solution of this embodiment, the laser 1 is a 532 nm semiconductor continuous laser or an all-solid-state tunable titanium sapphire dye continuous laser.

[0061] In this embodiment, a 532 nm semiconductor continuous laser is used.

[0062] As a preferred solution of this embodiment, the first imaging structure 40403, the second imaging structure 50403, the third imaging structure 406 and the fourth imaging structure 506 are CCD cameras, ICCD cameras or CMOS cameras.

[0063] In this example, a CMOS camera is used.

[0064] The working process of the present invention is as follows:

[0065] A Gaussian-distributed continuous laser beam is obtained from the laser 1, and the obtained continuous laser beam passes through the hollow light generating unit 2 to obtain a hollow beam; the obtained hollow beam is incident on the polarization beam splitter 3 to obtain two hollow beams with perpendicular directions, and then the two hollow beams respectively enter the transverse trapping unit 4 and the vertical trapping unit 5. First, the two hollow beams are respectively incident on the first deflecting mirror 401 and the second deflecting mirror 501; the two hollow beams are deflected at a certain angle, and then are respectively incident on the second convex lens 402 and the third convex lens 502 to form converging hollow beams, and the converging hollow beams are incident on the first sample cell 403 and the second sample cell 503; sample particles are sprayed into the sample cells, and the trapped particles can be observed near the focal point; by changing the size of the hollow beam, the third microscopic objective lens 405 can image the trapped particles in the third imaging structure 406 to obtain a graph of the transverse particle movement distance varying with the hollow light size; by rotating the first deflecting mirror 401, the two-dimensional rotation graph of the particles in the transverse direction can be obtained by the transverse image collecting mechanism 404; similarly, by changing the size of the hollow beam, the fourth microscopic objective lens 505 can image the trapped particles in the fourth imaging structure 506 to obtain a graph of the vertical particle movement distance varying with the hollow light size; by rotating the second deflecting mirror 501, the two-dimensional rotation graph of the particles in the vertical direction can be obtained by the vertical image collecting mechanism 504.

Claims

1. A light trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light, comprising a laser (1), a hollow light generating unit (2), and a polarization beam splitter (3) arranged in sequence, characterized in that, It further includes a horizontal capture unit (4), a vertical capture unit (5) and an illumination unit (6); the horizontal capture unit (4) is arranged in the P-light direction of the polarization beam splitter (3), the vertical capture unit (5) is arranged in the S-light direction of the polarization beam splitter (3), and the illumination unit (6) is arranged in the reverse direction of the S-light of the polarization beam splitter (3); The horizontal capture unit (4) includes a first deflecting mirror (401); the vertical capture unit (5) includes a second deflecting mirror (501); both the first deflecting mirror (401) and the second deflecting mirror (501) are wedge prisms and rotatable; The horizontal capture unit (4) further includes a second convex lens (402), a first sample cell (403) and a horizontal image collection mechanism (404) arranged in sequence; the vertical capture unit (5) further includes a third convex lens (502), a second sample cell (503) and a vertical image collection mechanism (504) arranged in sequence; A third microscope objective lens (405) and a third imaging structure (406) fixedly connected are arranged on the upper side in the vertical direction of the first sample cell (403); a fourth microscope objective lens (505) and a fourth imaging structure (506) fixedly connected are arranged on the front side in the horizontal direction of the second sample cell (503).

2. The optical trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light according to claim 1, wherein The horizontal image collection mechanism (404) includes a first microscope objective lens (40401), a first notch filter (40402) and a first imaging structure (40403) fixedly connected in sequence; the vertical image collection mechanism (504) includes a second microscope objective lens (50401), a second notch filter (50402) and a second imaging structure (50403) fixedly connected in sequence.

3. The optical trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light according to claim 1, characterized in that The illumination unit (6) includes a first convex lens (601) and an incandescent lamp (602) arranged in sequence on the lower side in the vertical direction of the polarization beam splitter (3).

4. The light trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light according to claim 1, wherein The hollow light generating unit (2) is a cross-phase space beam modulation system.

5. The light trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light according to claim 4, characterized in that, The hollow light generating unit (2) is a spatial light modulator.

6. The light trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light according to claim 1, characterized in that, The laser (1) is a 532nm semiconductor continuous laser or an all-solid-state tunable titanium sapphire dye continuous laser.

7. The optical trapping and three-dimensional manipulation device for light-absorbing particles in air based on hollow light according to claim 2, characterized in that The first imaging structure (40403), the second imaging structure (50403), the third imaging structure (406) and the fourth imaging structure (506) are CCD cameras, ICCD cameras or CMOS cameras.

Images