Micro-nano particle self-assembly and optical control method and device based on vector light field

Abstract

The invention relates to the technical field of optical systems, in particular to a micro-nano particle self-assembly and optical control method and device based on a vector light field. The purpose of the invention is to improve the precision of controlling the micro-nano particles. The first purpose is to provide a micro-nano particle self-assembly and optical control method based on a vector light field, and the method comprises the steps: carrying out the combined regulation and control of the orbital angular momentum and polarization state of a linear polarization Gaussian beam through a light field regulation and control assembly, so as to enable the linear polarization Gaussian beam to be converted into a high-order Poincare vector light field with a spatial polarization distribution characteristic; the vector light field is collimated, reflected and focused through the light guiding assembly, so that the vector light field acts on the micro-nano particles, and the micro-nano particles are self-assembled to form a self-assembled structure; and the rotation direction and the rotation speed of the self-assembly structure are regulated and controlled through the light field regulation and control assembly. The second purpose is to provide a micro-nano particle self-assembly and optical control system based on a vector light field.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and more specifically, to a method and device for self-assembly and optical manipulation of micro-nano particles based on vector optical fields. Background Art

[0002] The optomechanical effect is the result of momentum exchange during the interaction between light and matter. Due to its advantages such as non-contact, non-destructive, and high operation accuracy, it is widely used in frontier fields such as physics, chemistry, biology, and medicine. Currently, optical micro-manipulation techniques usually use traditional Gaussian optical fields or structured optical fields such as vortex light and cylindrical vector light. Among them, the angular momentum characteristics of the structured optical field play a key role in applications such as micro-nano particle capture, rotation, and sorting. To improve the precise control ability of the rotational motion of micro-nano particles, researchers have introduced scalar structured light and cylindrical vector light carrying topological charges, enabling them to drive the rotation of micro-nano particles. However, these methods still have certain limitations in terms of regulation flexibility and stability. For scalar structured light, the increase in its orbital angular momentum is usually accompanied by the expansion of the Gaussian beam size, which makes it difficult to stably manipulate micro-nano particles and limits the fine control of the rotation speed. For cylindrical vector light, although it has a certain angular momentum modulation ability, due to the inherent coupling relationship between its polarization mode and orbital angular momentum, it is difficult to achieve flexible control of the rotational motion of micro-nano particles.

[0003] Application No. 2011101137934 discloses a two-way bent surface core fiber micro-particle rotator, which includes two bent single-core fibers and micro-particles. This device relies on specific-shaped micro-particles and has strict requirements for the geometric structure and material of the particles, lacking universality and being difficult to apply to different types of micro-nano particles. In addition, this device relies on the optical fiber and its evanescent field. The arrangement method of the optical fiber limits the flexible manipulation of the micro-particles, and the device structure is complex, making it difficult to achieve the manipulation of a large number of micro-particles. At the same time, the regulation of the rotational motion of this device mainly relies on light intensity adjustment, and the rotation direction and speed cannot be independently controlled, limiting the ability to finely regulate the micro-particles.

[0004] Application No. 2019109995249 discloses an optical manipulation system and method based on a vector optical field. This system uses a helium-neon laser, a Q-plate, and an anisotropic crystal to generate a vector optical field and acts the optical field on the particles to be manipulated, causing the particles to rotate under the action of orbital angular momentum. However, this system only relies on an independent orbital angular momentum optical field for manipulation, and the regulation of the optical field angular momentum is not flexible. In addition, the micro-particles are only affected by a single orbital angular momentum and cannot precisely control the self-assembly behavior of the micro-particles, limiting the formation and manipulation ability of the micro-structure. Further, the increase in the orbital angular momentum in this system will cause the spot size to expand, affecting the stable capture of micro-nano particles and limiting the accuracy of rotational manipulation, making it difficult to meet the requirements of fine optical micro-manipulation.

[0005] In summary, in the process of rotating and controlling micro-nano particles in the prior art, there are still problems such as non-adjustable rotation speed, uncontrollable rotation direction, limited manipulation accuracy, and difficulty in forming stable aggregates. Summary of the Invention

[0006] The present invention aims to overcome at least one defect of the above-mentioned prior art, and provides a method and device for self-assembly and optical manipulation of micro-nano particles based on a vector light field, for improving the accuracy of manipulating micro-nano particles.

[0007] The first object of the present invention is to provide a method for self-assembly and optical manipulation of micro-nano particles based on a vector light field, including the following steps:

[0008] S01. Jointly regulate the orbital angular momentum and polarization state of a linearly polarized Gaussian beam through a light field regulation component, so as to convert the linearly polarized Gaussian beam into a high-order Poincaré vector light field with a spatial polarization distribution characteristic. The vector light field is linearly composed of a left-handed circularly polarized Laguerre-Gaussian beam and a right-handed circularly polarized Laguerre-Gaussian beam with opposite topological charge numbers and orthogonal conjugate polarization states. Among them, the right-handed circularly polarized Laguerre-Gaussian beam is configured with a first orthogonal polarization component weight coefficient, and the left-handed circularly polarized Laguerre-Gaussian beam is configured with a second orthogonal polarization component weight coefficient;

[0009] S02. Collimate, reflect and focus the vector light field through a light guiding component, so that the vector light field acts on the micro-nano particles and causes the micro-nano particles to self-assemble into a self-assembled structure;

[0010] S03. Adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient through the light field regulation component to control the rotation direction and rotation speed of the self-assembled structure.

[0011] In the present invention, the motion state of micro-nano particles in the high-order Poincaré vector light field is significantly affected by the combination of orbital angular momentum and polarization state. By adjusting the light field regulation component, the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient can be precisely controlled, and then the total orbital angular momentum of the vector light field can be adjusted, so as to induce the micro-nano particles to spontaneously assemble into a self-assembled structure. Moreover, the rotation direction and rotation speed of the self-assembled structure can be controlled by fine-tuning the light field regulation component while keeping the spot size unchanged. In this way, the flexibility and accuracy of manipulating micro-nano particles can be significantly improved.

[0012] Preferably, the self-assembled structure is a "propeller" structure.

[0013] In some embodiments, the light field regulation component at least includes a beam expander-collimator device, a half-wave plate, a quarter-wave plate, and a vortex half-wave plate that are coaxially arranged and spaced apart in sequence;

[0014] The combined regulation of the orbital angular momentum and polarization state of a linearly polarized Gaussian beam by the optical field regulation component includes:

[0015] S11. After the linearly polarized Gaussian beam sequentially passes through a beam expander-collimator, a half-wave plate, and a quarter-wave plate, it is transformed into a first optical field in which a left-handed circularly polarized light without carrying orbital angular momentum and a right-handed circularly polarized light without carrying orbital angular momentum are orthogonally superposed.

[0016] S12. After the first optical field passes through a vortex half-wave plate, the left-handed circularly polarized light without carrying orbital angular momentum is transformed into a right-handed circularly polarized Laguerre-Gaussian beam carrying orbital angular momentum, and the right-handed circularly polarized light without carrying orbital angular momentum is transformed into a left-handed circularly polarized Laguerre-Gaussian beam carrying orbital angular momentum.

[0017] In the present invention, the half-wave plate and the quarter-wave plate are used to adjust the polarization state of the beam, converting the linearly polarized Gaussian light into orthogonally circularly polarized Gaussian light; the vortex half-wave plate is used to endow the beam with orthogonally circularly polarized Laguerre-Gaussian beams carrying orbital angular momentum, thereby forming a high-order Poincaré vector optical field. The structure of this optical field regulation component is simple, and a high-order Poincaré vector optical field can be obtained efficiently and conveniently.

[0018] The method for self-assembly and optical manipulation of micro-nano particles in the present invention is based on the orbital angular momentum carried by the high-order Poincaré optical field. By applying the orbital angular momentum and optical force to the micro-nano particles through the optical field, the particles are induced to self-assemble in the optical field and form a propeller form with a stable structure. The principle is as follows:

[0019] In step S11, after the linearly polarized Gaussian beam emitted by the light source component passes through the half-wave plate and the quarter-wave plate, the optical field is transformed as follows.

[0020]

[0021] Among them, the linearly polarized Gaussian beam uses a horizontally polarized Gaussian beam. represents a left-handed circularly polarized light without carrying topological charge. represents a right-handed circularly polarized light without carrying topological charge, r represents the radial coordinate. represents the azimuth angle, i represents the imaginary unit, and α represents the fast-axis angle of the half-wave plate.

[0022] In step S12, after the beam generated in step S11 passes through the vortex half-wave plate, the optical field is transformed as follows.

[0023]

[0024] The light beam acquires orbital angular momentum after passing through the vortex half-wave plate. Among them, the topological charge number m represents the quantum number of the orbital angular momentum carried by the right-handed circularly polarized Laguerre-Gaussian beam, and -m represents the quantum number of the orbital angular momentum carried by the left-handed circularly polarized Laguerre-Gaussian beam;

[0025] Define as the weight coefficient A of the first orthogonally polarized component, and define to represent the weight coefficient B of the second orthogonally polarized component. At this time, the total orbital angular momentum of the vector optical field can be defined as <oam>∝(|A| - |B|)· <m>, when the topological charge number m is determined, the direction and magnitude of the total orbital angular momentum can be determined by the values of the weight coefficient A of the first orthogonal polarization component and the weight coefficient B of the second orthogonal polarization component of the vector optical field. Therefore, by adjusting the fast axis angle α of the half-wave plate, the total orbital angular momentum can be changed, and thus the rotation direction and rotation speed of the micro-nano particles can be controlled.

[0026] Research shows that when micro-nano particles are uniformly distributed in the above-mentioned formed high-order Poincaré vector optical field, the motion state of the micro-nano particles in the optical field is significantly affected by the combination of orbital angular momentum and polarization state. By adjusting the fast axis angle of the half-wave plate, the total orbital angular momentum of the light beam can be changed, thereby inducing the micro-nano particles to spontaneously assemble into self-assembled structures, such as "propeller" structures. The rotation speed and morphological characteristics of the self-assembled structure are closely related to the magnitude of the angular momentum and polarization distribution of the optical field.

[0027] Furthermore, by adjusting the weight coefficient A of the first orthogonal polarization component and the weight coefficient B of the second orthogonal polarization component to equal values, a stable self-assembled structure can be achieved. By rotating different numbers of particles, different structures can be realized. When the self-assembled structure is a "propeller" structure, the number of blades of the "propeller" corresponds to the number of particles. Among them, the two-blade and four-blade structures have biaxial rotational symmetry, and the three-blade structure has triaxial rotational symmetry.

[0028] Among them, the rotation of the self-assembled structure originates from the orbital angular momentum of the optical field. By adjusting the fast axis angle of the half-wave plate, the total orbital angular momentum of the light beam can be precisely controlled, thereby affecting the rotation direction of the self-assembled structure. Specifically, the rotation directions include clockwise and counterclockwise. In addition, by changing the orbital angular momentum of the light beam and the number of blades of the "propeller", the rotation speed of the propeller can be effectively adjusted to achieve precise control of the motion of micro-nano particles.

[0029] In some embodiments, the value range of m is 1 - 128.

[0030] In some embodiments, in step S03, the adjusting the weight coefficient A of the first orthogonal polarization component and the weight coefficient B of the second orthogonal polarization component by the optical field control component includes:

[0031] Adjusting the weight coefficient A of the first orthogonal polarization component and the weight coefficient B of the second orthogonal polarization component by adjusting the fast axis angle of the half-wave plate.

[0032] In some embodiments, the wavelength of the linearly polarized Gaussian beam is 780 - 1650 nm.

[0033] In some embodiments, the micro-nano particles are transparent dielectric micro-nano particles.

[0034] Preferably, the micro-nano particles are polystyrene micro-nano particles or silica micro-nano particles.

[0035] Preferably, the particle size range of the micro-nano particles is 50 nm - 10 μm.

[0036] Based on the same inventive concept, the present invention also provides a micro-nano particle self-assembly and optical manipulation device based on a vector optical field, comprising:

[0037] A sample stage for placing micro-nano particles;

[0038] A light source assembly for emitting a linearly polarized Gaussian beam;

[0039] A light field modulation assembly for modulating the orbital angular momentum and polarization state of the linearly polarized Gaussian beam emitted by the light source assembly, so that the linearly polarized Gaussian beam is converted into a high-order Poincaré vector optical field with a spatial polarization distribution characteristic, and the vector optical field is composed of a left-handed circularly polarized Laguerre-Gaussian beam and a right-handed circularly polarized Laguerre-Gaussian beam with opposite topological charges and orthogonal conjugate polarization states. Among them, the vector optical field has a first orthogonal polarization component weight coefficient and a second orthogonal polarization component weight coefficient defined based on the right-handed circularly polarized Laguerre-Gaussian beam and the left-handed circularly polarized Laguerre-Gaussian beam;

[0040] A light guiding assembly for collimating, reflecting and focusing the vector optical field onto the micro-nano particles, and causing the micro-nano particles to self-assemble into a self-assembled structure. The light field modulation assembly is further used to adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient to control the rotation direction and rotation speed of the self-assembled structure;

[0041] An imaging assembly for imaging the micro-nano particles and / or the movement process of the micro-nano particles.

[0042] The light source assembly at least includes a laser for emitting a linearly polarized Gaussian beam. Preferably, the power range of the laser is 1 milliwatt to 5 watts.

[0043] In some embodiments, the light field modulation assembly includes a beam expander-collimator, a half-wave plate, a quarter-wave plate and a vortex half-wave plate that are coaxially and sequentially spaced. The linearly polarized Gaussian beam emitted by the light source assembly sequentially passes through the beam expander-collimator, the half-wave plate, the quarter-wave plate and the vortex half-wave plate. Among them, the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient are adjusted by adjusting the fast axis angle of the half-wave plate.

[0044] First, the light source component generates a stable linearly polarized Gaussian beam. After passing through the beam expander and collimator, a half-wave plate and a quarter-wave plate are used to convert it into a circularly polarized light. Second, the circularly polarized beam obtains orbital angular momentum through a vortex half-wave plate, forming a high-order Poincaré vector beam. Then, by adjusting the angle of the half-wave plate, the weight of the orthogonal polarization components is precisely controlled, thereby regulating the total orbital angular momentum of the light field while keeping the spot size unchanged.

[0045] In some embodiments, the beam expander and collimator includes a first convex lens and a second convex lens arranged at coaxial intervals. Preferably, the focal lengths of both the first convex lens and the second convex lens are 50 mm - 250 mm. Among them, the focal length of the first convex lens is smaller than that of the second convex lens and is closer to the laser in terms of spatial position.

[0046] In some embodiments, the sample stage is provided with a three-dimensional adjustable mechanism configured to enable the position of the micro-nano particles in the vector light field to be adjustable along the x - y - z directions.

[0047] In some embodiments, the light guiding component includes a mirror and a first objective lens;

[0048] The vector light field adjusts its propagation direction through the mirror and is incident on the first objective lens. Then, it penetrates the sample stage through the first objective lens and is focused on the micro-nano particles.

[0049] In some embodiments, the light guiding component further includes a beam splitter disposed between the mirror and the first objective lens. The vector light field reflected by the mirror is transmitted through the beam splitter to the first objective lens;

[0050] The imaging component includes an illumination light source, a second objective lens, a light focusing device, and a CCD camera. The second objective lens is disposed above the sample stage, and the second objective lens focuses the illumination light source on the micro-nano particles. After passing through the micro-nano particles, the illumination light source penetrates the sample stage and is incident on the first objective lens. Then, it is reflected by the beam splitter to the light focusing device and then imaged on the CCD camera. Among them, the CCD camera is connected to a computer.

[0051] Preferably, the light focusing device uses a third convex lens, and the third convex lens is located in front of the CCD camera.

[0052] In some embodiments, the focal length of the third convex lens is 50 mm - 250 mm.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] (1) The present invention uses a high-order Poincaré vector light field, making the offset and rotation of micro-nano particles more precise. Especially in low light intensity and complex microenvironments, stable manipulation can still be achieved.

[0055] (2) The present invention can simultaneously control the self-assembly process of micro-nano particles and their rotational motion. Especially during the formation process of the "propeller" self-assembly, the rotational speed and direction can be independently adjusted, providing a new solution for the complex motion control of micro-mechanical systems.

[0056] (3) Based on the regulation method of the weight coefficients of the first orthogonal polarization component and the second orthogonal polarization component, the present invention can precisely adjust the orbital angular momentum without changing the beam size, realizing flexible control of the rotational behavior of micro-nano particles and breaking through the limitations of traditional methods. Brief Description of the Drawings

[0057] Figure 1 It is a flowchart of the method for self-assembly and optical manipulation of micro-nano particles based on vector light fields in Example 1.

[0058] Figure 2 It is a schematic diagram of the device for self-assembly and optical manipulation of micro-nano particles based on vector light fields in Example 2.

[0059] Figure 3 It is the intensity distribution of the high-order Poincaré light field and the total orbital angular momentum distribution under different component weightings demonstrated by the method based on Example 1.

[0060] Figure 4 It is the demonstration that micro-nano particles are self-assembled into propellers with different numbers of blades by the method based on Example 1.

[0061] Figure 5 It is the demonstration of the rotational direction of the four-blade structure propeller under different fast-axis angles of the half-wave plate by the method based on Example 1.

[0062] Figure 6 It is the demonstration of the rotational speed of propellers with different structures under different fast-axis angles of the half-wave plate by the method based on Example 1.

[0063] Brief Description of the Drawings: Laser 1, First convex lens 2, Second convex lens 3, Half-wave plate 4, Quarter-wave plate 5, Vortex half-wave plate 6, Reflecting mirror 7, Beam splitter 8, First objective lens 9, Sample stage 10, Micro-nano particles 11, Second objective lens 12, Illumination light source 13, Third convex lens 14, CCD camera 15, Computer 16. Detailed Embodiments

[0064] The drawings of the present invention are only for illustrative purposes and should not be construed as a limitation to the present invention. For better illustrating the following embodiments, some components in the drawings may be omitted, enlarged or reduced, which do not represent the dimensions of the actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0065] In addition, in the present invention, unless otherwise clearly specified and defined, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In addition, in the present invention, descriptions such as "first" and "second" are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0067] Embodiment 1

[0068] As Figure 1 shown, this embodiment provides a method for self-assembly and optical manipulation of micro-nano particles based on vector optical fields, including the following steps:

[0069] S01. Jointly regulate the orbital angular momentum and polarization state of a linearly polarized Gaussian beam through an optical field regulation component, so as to convert the linearly polarized Gaussian beam into a high-order Poincaré vector optical field with spatial polarization distribution characteristics. The vector optical field is linearly composed of a left-handed circularly polarized Laguerre-Gaussian beam and a right-handed circularly polarized Laguerre-Gaussian beam with opposite topological charge numbers and orthogonally conjugate polarization states. Among them, the right-handed circularly polarized Laguerre-Gaussian beam is configured with a first orthogonal polarization component weight coefficient, and the left-handed circularly polarized Laguerre-Gaussian beam is configured with a second orthogonal polarization component weight coefficient;

[0070] S02. Collimate, reflect and focus the vector optical field through an optical guiding component, so that the vector optical field acts on the micro-nano particles and causes the micro-nano particles to self-assemble into a self-assembled structure;

[0071] S03. Adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient through the optical field regulation component to regulate the rotation direction and rotation speed of the self-assembled structure.

[0072] Specifically, when implemented, the wavelength range of the linearly polarized Gaussian beam is 780 - 1650 nm. In the test example, a horizontally polarized Gaussian beam is used, and the wavelength is set to 1064 nm.

[0073] In some embodiments, in order to stably obtain a high-order Poincaré vector optical field that meets the requirements, refer to Figure 2 , the optical field modulation component at least includes a beam expander and collimator device, a half-wave plate 4, a quarter-wave plate 5, and a vortex half-wave plate 6 that are coaxially arranged and spaced apart in sequence. Among them, the half-wave plate 4 and the quarter-wave plate 5 are used to adjust the polarization state of the light beam to convert linearly polarized light into orthogonally circularly polarized light; the vortex half-wave plate 6 is used to endow the orthogonally circularly polarized light with orbital angular momentum to form a high-order Poincaré vector optical field.

[0074] Specifically, refer to Figure 2 , in step S01, the linearly polarized Gaussian beam first passes through the beam expander and collimator device, the half-wave plate 4, and the quarter-wave plate 5, and is converted into a first optical field in which a left-handed circularly polarized light without orbital angular momentum and a right-handed circularly polarized light without orbital angular momentum are orthogonally superposed. Then, the first optical field passes through the vortex half-wave plate 6, and the left-handed circularly polarized light without orbital angular momentum is converted into a right-handed circularly polarized Laguerre-Gaussian (LG) beam with orbital angular momentum, and the right-handed circularly polarized light without orbital angular momentum is converted into a left-handed circularly polarized Laguerre-Gaussian beam with orbital angular momentum.

[0075] The method for self-assembly and optical manipulation of micro-nano particles of the present invention is based on the orbital angular momentum carried by the high-order Poincaré optical field. By applying the orbital angular momentum and optical force to the micro-nano particles through the optical field, the particles are induced to self-assemble in the optical field and form a self-assembled structure with a stable structure, such as a "propeller" structure. The principle is as follows:

[0076] After the linearly polarized Gaussian beam passes through the half-wave plate 4 and the quarter-wave plate 5, the optical field is transformed as follows,

[0077]

[0078] Among them, the three columns of Jones vectors in formula (1) are specifically: the linearly polarized Gaussian beam uses a horizontally polarized Gaussian beam represents a left-handed circularly polarized light without orbital angular momentum, represents a right-handed circularly polarized light without orbital angular momentum, r represents the radial coordinate, represents the azimuth angle, i represents the imaginary unit, and α represents the fast axis angle of the half-wave plate 4. Exemplarily, for the convenience of subsequent adjustment operations of the half-wave plate 4, the included angle between the fast axis of the quarter-wave plate 5 and the horizontal axis (such as the x-axis in Figure 2 ) in the test example is 45°.

[0079] Then, the above-mentioned left-handed circularly polarized light and right-handed circularly polarized light pass through the vortex half-wave plate 6, and the optical field is transformed as follows,

[0080]

[0081] The light beam acquires orbital angular momentum after passing through the vortex half-wave plate 6. Among them, the left-handed circularly polarized light is converted into a right-handed circularly polarized Laguerre-Gaussian beam, and the right-handed circularly polarized light is converted into a left-handed circularly polarized Laguerre-Gaussian beam. Moreover, both carry orbital angular momenta with opposite topological charges, forming a high-order Poincaré vector light field. The topological charge number m represents the orbital angular momentum quantum number carried by the right-handed circularly polarized Laguerre-Gaussian beam, and -m represents the orbital angular momentum quantum number carried by the left-handed circularly polarized Laguerre-Gaussian beam.

[0082] Furthermore, define as the weight coefficient A of the first orthogonally polarized component, and define to represent the weight coefficient B of the second orthogonally polarized component. At this time, the total orbital angular momentum of the vector light field can be defined as <oam>∝(|A| - |B|)· <m>It is easy to understand that when the topological charge number m is determined, the direction and magnitude of the total orbital angular momentum can be determined by the weights of the orthogonal polarization components of the vector optical field: the values of the first orthogonal polarization component weight coefficient A and the second orthogonal polarization component weight coefficient B. Since the values of A and B are determined based on the fast axis angle α of the half-wave plate 4, therefore, by adjusting the fast axis angle α of the half-wave plate 4, the first orthogonal polarization component weight coefficient A and the second orthogonal polarization component weight coefficient B can be adjusted, thereby changing the total orbital angular momentum, and further controlling the rotation direction and rotation speed of the micro-nano particles.

[0083] In specific implementation, the micro-nano particles are transparent dielectric micro-nano particles, such as polystyrene micro-nano particles or silica micro-nano particles. Among them, the particle size range of the micro-nano particles is 50nm - 10μm. In the test example, the micro-nano particle sample is prepared using a polystyrene solution with a diameter of 2.5μm and a concentration of 0.125%.

[0084] Example 2

[0085] Reference Figure 2 , this embodiment provides a micro-nano particle self-assembly and optical manipulation device based on a vector optical field, which is applicable to implementing the micro-nano particle self-assembly and optical manipulation method based on a vector optical field in Embodiment 1, including:

[0086] A sample stage 10 for placing the micro-nano particles 11;

[0087] A light source assembly for emitting a linearly polarized Gaussian beam;

[0088] A light field regulation assembly for regulating the orbital angular momentum and polarization state of the linearly polarized Gaussian beam emitted by the light source assembly, so as to convert the linearly polarized Gaussian beam into a high-order Poincaré vector optical field with a spatial polarization distribution characteristic. The vector optical field is composed of a linearly polarized superposition of a left-handed circularly polarized Laguerre-Gaussian beam and a right-handed circularly polarized Laguerre-Gaussian beam with opposite topological charges and orthogonal conjugate polarization states. Among them, the right-handed circularly polarized Laguerre-Gaussian beam is configured with a first orthogonal polarization component weight coefficient, and the left-handed circularly polarized Laguerre-Gaussian beam is configured with a second orthogonal polarization component weight coefficient;

[0089] A light guiding assembly for collimating, reflecting and focusing the vector optical field onto the micro-nano particles, and causing the micro-nano particles to self-assemble to form a self-assembled structure. The light field regulation assembly is also used to adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient to control the rotation direction and rotation speed of the self-assembled structure;

[0090] An imaging assembly for imaging the micro-nano particles 11 and / or the movement process of the micro-nano particles 11.

[0091] In specific implementation, the optical field modulation component includes a beam expander and collimator device, a half-wave plate 4, a quarter-wave plate 5, and a vortex half-wave plate 6 that are sequentially arranged at intervals along the horizontal axis. Among them, the weight coefficients of the first orthogonal polarization component and the second orthogonal polarization component are adjusted by adjusting the fast axis angle of the half-wave plate. The linearly polarized Gaussian beam emitted by the light source component sequentially passes through the beam expander and collimator device, the half-wave plate 4, the quarter-wave plate 5, and the vortex half-wave plate 6. Among them, the light source component includes at least a laser 1. In the test example, the power of the laser 1 is 40 milliwatts, and the wavelength of the emitted linearly polarized Gaussian beam is 1064 nm.

[0092] Specifically, the quarter-wave plate 5 is arranged in front of the half-wave plate 4, and the vortex half-wave plate 6 is arranged in front of the quarter-wave plate 5. Referring to Figure 2 the coordinate system shown, the "front" is defined as being away from the laser 1 along the +z direction. In the test example, the topological charge number m of the vortex half-wave plate 6 is 2.

[0093] During operation, the light source component generates a stable linearly polarized Gaussian light. After being collimated by the beam expander and collimator device, it is converted into circularly polarized light by using the half-wave plate 4 and the quarter-wave plate 5. Specifically, the circularly polarized light includes left-handed circularly polarized light and right-handed circularly polarized light that are orthogonally superimposed. Then, the circularly polarized light beam obtains orbital angular momentum through the vortex half-wave plate 6. Among them, the left-handed circularly polarized light is converted into a right-handed circularly polarized Laguerre-Gaussian beam carrying orbital angular momentum, and the right-handed circularly polarized light is converted into a left-handed circularly polarized Laguerre-Gaussian beam carrying orbital angular momentum. The right-handed circularly polarized Laguerre-Gaussian beam and the left-handed circularly polarized Laguerre-Gaussian beam are linearly superimposed to form a high-order Poincaré vector optical field.

[0094] In specific implementation, the right-handed circularly polarized Laguerre-Gaussian beam is configured with a weight coefficient of the first orthogonal polarization component, and the left-handed circularly polarized Laguerre-Gaussian beam is configured with a weight coefficient of the second orthogonal polarization component. Based on the method of Embodiment 1, it can be known that the values of A and B are determined by the fast axis angle α of the half-wave plate 4. Therefore, by adjusting the fast axis angle α of the half-wave plate 4, the numerical values of the weight coefficient A of the first orthogonal polarization component and the weight coefficient B of the second orthogonal polarization component can be accurately controlled, and further, the total orbital angular momentum of the optical field can be modulated. During this process, the spot size can be kept unchanged. In this way, the accuracy and flexibility of manipulating the micro-nano particles 11 can be improved.

[0095] In specific implementation, the beam expander and collimator device includes a first convex lens 2 and a second convex lens 3 that are arranged at intervals along the coaxial (such as Figure 2 the z-axis shown) direction. Preferably, the focal lengths of the first convex lens 2 and the second convex lens 3 are both 50 mm - 250 mm. Among them, the focal length of the first convex lens 2 is smaller than that of the second convex lens 3, and it is arranged closer to the laser 1 in terms of spatial position. In the test example, the focal length of the first convex lens 2 is 150 mm, and the focal length of the second convex lens 3 is 250 mm.

[0096] To improve the adjustability of the sample, the sample stage 10 is provided with a three-dimensional adjustable mechanism, which is configured to make the position of the micro-nano particles 11 in the vector light field adjustable along the x-y-z directions, facilitating the realization of self-assembled structures of different shapes. To facilitate the penetration of the illumination light source and the vector light field, the support surface of the sample stage for placing the sample is made of a transparent material.

[0097] As Figure 2 shown, the light guiding component includes a mirror 7 and a first objective lens 9;

[0098] The vector light field is reflected by the mirror 7 and then directly enters the first objective lens 9, and then is focused on the micro-nano particles 11 through the first objective lens 9.

[0099] In specific implementation, the mirror 7 and the first objective lens 9 are arranged in sequence along the Figure 2 shown y-axis direction, and the first objective lens 9 is a high-power objective lens. In specific implementation, an oil immersion objective lens with a magnification of 100 times is adopted.

[0100] In some embodiments, the light guiding component further includes a semi-transmissive and semi-reflective mirror 8 disposed between the mirror 7 and the first objective lens 9. Through the reflection of the mirror 7, the collimated vector light field enters the first objective lens 9 through the semi-transmissive and semi-reflective mirror 8 with a high transmittance;

[0101] The imaging component includes an illumination light source 13, a second objective lens 12, a light focusing device, and a CCD camera 15;

[0102] The second objective lens 12 is disposed above the sample stage 10. The second objective lens 12 is used to focus the illumination light source 13 on the micro-nano particles 11. In specific implementation, as Figure 2 shown, the second objective lens 12 and the illumination light source 13 are sequentially disposed in the y-axis direction of the first objective lens 9. The illumination light source 13 passes through the micro-nano particles 11 and then penetrates the sample stage 10 and enters the first objective lens 9, and then is reflected by the semi-transmissive and semi-reflective mirror 8 to the light focusing device, and then imaged on the CCD camera 15. Among them, the CCD camera 15 is connected to a computer 16. In specific implementation, the semi-transmissive and semi-reflective mirror 8 adopts an optical lens that forms an angle of 45° with both the incident direction of the vector light field and the incident direction of the illumination light source 13. The transmittance and reflectance of this optical lens for different wavelengths are different, so that the vector light can be directly transmitted to the first objective lens for focusing, and at the same time, the upper illumination light source 13 can be reflected to the CCD camera 15 for imaging.

[0103] Among them, to obtain clear imaging, the micro-nano particles 11 are placed at the focal plane of the first objective lens 9. In this way, it is also convenient to efficiently control the self-assembly and movement of the micro-nano particles 11.

[0104] To ensure the accuracy and stability of the manipulation, the CCD camera 15 can record the rotation state and motion parameters of the microspheres in real time, and the computer 16 can perform data processing to provide real-time feedback. The optical force on the microspheres in the high-order Poincaré optical field is calculated through a mathematical model, and combined with the electromagnetic field distribution and hydrodynamic analysis, the rotation speed of the self-assembled structure is predicted.

[0105] Preferably, the optical focusing device uses the third convex lens 14, and the third convex lens 14 is located in front of the CCD camera 15. In some embodiments, the focal length of the third convex lens 14 is 50 mm - 250 mm. In the test example, the focal length of the third convex lens 14 is 100 mm, and the second objective lens 12 uses a low-magnification objective lens with a magnification of 10 times.

[0106] Test example

[0107] Figure 3 Showing the use of the formula in Example 1

[0108] The calculated normalized light intensity distribution and the corresponding total orbital angular momentum distribution of the high-order Poincaré optical field under different component weights are shown. The results show that the intensity and orbital angular momentum of the high-order Poincaré vector optical field can be regulated by adjusting the fast-axis angle α of the half-wave plate 4. Among them, Figure 3 The upper row of images shows the light intensity distribution at the focal plane under different weight combinations of the weight coefficient A of the first orthogonally polarized component and the weight coefficient B of the second orthogonally polarized component, and the lower row of images is the total orbital angular momentum distribution under the corresponding conditions. It can be seen from the figure that when the values of the weight coefficient A of the first orthogonally polarized component and the weight coefficient B of the second orthogonally polarized component change, the intensity distribution of the optical field remains relatively stable, showing an annular structure, but the value and direction of the total orbital angular momentum distribution change with the relative magnitudes of the weight coefficient A of the first orthogonally polarized component and the weight coefficient B of the second orthogonally polarized component. Specifically, when α < 22.5°, A > B, and the total orbital angular momentum is negative; when α > 22.5°, A < B, and the total orbital angular momentum is positive; when α = 22.5°, A = B, and the total orbital angular momentum is zero.

[0109] To verify the feasibility of the present invention, the following experimental verification is carried out:

[0110] Reference Figure 4 , in this test example, the micro-nano particles 11 are specifically prepared using a polystyrene solution with a diameter of 2.5 μm and a concentration of 0.125%. In addition, the wavelength of the horizontally polarized Gaussian beam is set to 1064 nm, and the topological charge number m of the vortex half-wave plate 6 is 2.

[0111] First, adjust the fast axis angle α of the half-wave plate 4 to 22.5°, so that the weights A = B, that is, the total orbital angular momentum of the light beam is zero, and the particles self-assemble into a stable propeller structure.

[0112] Furthermore, according to the different number of particles, the propeller structure can be assembled into two-, three-, and four-blade structures and remain stable, without separating or deforming during rotation. Among them, the two-blade structure and the four-blade structure have two-axis rotational symmetry, and the three-blade structure has three-axis rotational symmetry.

[0113] Furthermore, by changing the fast axis angle α to regulate the total orbital angular momentum of the light beam, the rotation direction and rotation speed of the propeller can be controlled. When the total orbital angular momentum is negative, the propeller rotates counterclockwise around its center of symmetry; when the total orbital angular momentum is zero, the propeller does not rotate; when the total orbital angular momentum is positive, the propeller rotates clockwise around its center of symmetry.

[0114] As a demonstration, Figure 5 shows the rotation of the "propeller" with four blades at different fast axis angles α of the half-wave plate 4, verifying that the precise control of the rotation direction of the micro-nano particles 11 can be achieved by regulating the orbital angular momentum of the light field. Specifically, when the fast axis angle α of the half-wave plate 4 is less than 22.5°, as shown in Figure 5 the (a) row, the total orbital angular momentum of the light field is negative, and the propeller rotates clockwise; when the fast axis angle α of the half-wave plate 4 is equal to 22.5°, as shown in Figure 5 the (b) row, the total orbital angular momentum is approximately zero, and the propeller structure remains stationary; when the fast axis angle α of the half-wave plate 4 is greater than 22.5°, as shown in Figure 5 the (c) row, the total orbital angular momentum of the light field is positive, and the propeller rotates counterclockwise. The experimental results show that the magnitude and direction of the total orbital angular momentum of the light field are determined by the numerical values of the weight coefficient A of the first orthogonally polarized component and the weight coefficient B of the second orthogonally polarized component, and can be continuously adjusted by adjusting the fast axis angle of the half-wave plate 4. This result further proves that the method proposed in the present invention can accurately control the rotation direction of the self-assembled structure of micro-nano particles 11 without changing the spot size, providing an efficient and adjustable control means for optical micro-manipulation.

[0115] Furthermore, the experimental results show that the propeller structures with different numbers of blades have different rotation speeds, as shown in Figure 6 shown. Figure 6 shows the rotation of the "propellers" with different numbers of blades self-assembled from 2, 3, and 4 polystyrene microspheres as the fast axis angle α of the half-wave plate 4 changes. Among them, the two-blade propeller has the highest rotation speed, the four-blade structure is the second, and the three-blade structure has the slowest rotation speed. This phenomenon is closely related to the self-assembled structure. The three-blade propeller has a higher stability and the smallest moment arm, so its rotation speed is the slowest.

[0116] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.< / m> < / oam> < / m> < / oam>

Claims

1. A method for self-assembly and optical manipulation of micro-nano particles based on vector optical fields, characterized in that It includes the following steps: S01. Jointly regulate the orbital angular momentum and polarization state of the linearly polarized Gaussian beam through the optical field regulation component, so as to convert the linearly polarized Gaussian beam into a high-order Poincaré vector optical field with a spatial polarization distribution characteristic. The vector optical field is composed of a left-handed circularly polarized Laguerre-Gaussian beam and a right-handed circularly polarized Laguerre-Gaussian beam with opposite topological charge numbers and orthogonally conjugate polarization states. Among them, the right-handed circularly polarized Laguerre-Gaussian beam is configured with a first orthogonal polarization component weight coefficient, and the left-handed circularly polarized Laguerre-Gaussian beam is configured with a second orthogonal polarization component weight coefficient; S02. Collimate, reflect and focus the vector optical field through the optical guiding component, so that the vector optical field acts on the micro-nano particles and makes the micro-nano particles self-assemble to form a self-assembled structure; S03. Adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient through the optical field regulation component to control the rotation direction and rotation speed of the self-assembled structure.

2. The method according to claim 1, characterized in that, The optical field regulation component at least includes a beam expander-collimator, a half-wave plate, a quarter-wave plate and a vortex half-wave plate that are coaxially arranged and spaced in sequence; The joint regulation of the orbital angular momentum and polarization state of the linearly polarized Gaussian beam through the optical field regulation component includes: S11. After the linearly polarized Gaussian beam passes through the beam expander-collimator, the half-wave plate and the quarter-wave plate in sequence, it is converted into a first optical field in which a left-handed circularly polarized light without carrying orbital angular momentum and a right-handed circularly polarized light without carrying orbital angular momentum are orthogonally superposed; S12. After the first optical field passes through the vortex half-wave plate, the left-handed circularly polarized light without carrying orbital angular momentum is converted into a right-handed circularly polarized Laguerre-Gaussian beam carrying orbital angular momentum, and the right-handed circularly polarized light without carrying orbital angular momentum is converted into a left-handed circularly polarized Laguerre-Gaussian beam carrying orbital angular momentum.

3. The method according to claim 2, characterized in that In step S11, the optical field is transformed as follows, Among them, the linearly polarized Gaussian beam adopts a horizontally polarized Gaussian beam represents a left-handed circularly polarized light without carrying orbital angular momentum, represents a right-handed circularly polarized light without carrying orbital angular momentum, r represents the radial coordinate, represents the azimuth angle, i represents the imaginary unit, and α represents the fast axis angle of the half-wave plate; In step S12, the optical field is transformed as follows, Among them, the topological charge number m represents the orbital angular momentum quantum number carried by the right-handed circularly polarized Laguerre-Gaussian beam, and -m represents the orbital angular momentum quantum number carried by the left-handed circularly polarized Laguerre-Gaussian beam; Definition Define the weight coefficient A of the first orthogonally polarized component as the weight coefficient B of the second orthogonally polarized component. The total orbital angular momentum of the vector optical field <oam>∝(|A| - |B|)· <m> 。< / m> < / oam> 4. The method according to claim 2, characterized in that, In step S3, the adjustment of the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient through the optical field regulation component includes: Adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient by adjusting the fast axis angle of the half-wave plate.

5. The method according to any one of claims 1-4, characterized in that, The micro-nano particles are transparent dielectric micro-nano particles, and / or; The particle size range of the micro-nano particles is 50nm - 10μm; and / or, The wavelength of the linearly polarized Gaussian beam is 780 - 1650nm.

6. The method according to claim 3, wherein The value range of m is 1 - 128.

7. A micro-nano particle self-assembly and optical manipulation device based on vector optical fields, characterized in that It includes: A sample stage for placing micro-nano particles; A light source component for emitting a linearly polarized Gaussian beam; A light field modulation component is used to modulate the orbital angular momentum and polarization state of a linearly polarized Gaussian beam emitted by a light source component, so as to convert the linearly polarized Gaussian beam into a high-order Poincaré vector light field with a spatial polarization distribution characteristic. The vector light field is composed of a left-handed circularly polarized Laguerre-Gaussian beam and a right-handed circularly polarized Laguerre-Gaussian beam with opposite topological charges and orthogonally conjugate polarization states. Among them, the right-handed circularly polarized Laguerre-Gaussian beam is configured with a first orthogonal polarization component weight coefficient, and the left-handed circularly polarized Laguerre-Gaussian beam is configured with a second orthogonal polarization component weight coefficient; A light guiding component is used to collimate, reflect and focus the vector light field onto micro-nano particles, and cause the micro-nano particles to self-assemble to form a self-assembled structure. The light field modulation component is also used to adjust the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient to control the rotation direction and rotation speed of the self-assembled structure; An imaging component is used to image the micro-nano particles and / or the motion process of the micro-nano particles.

8. The device according to claim 7, characterized in that, The light field modulation component includes a beam expander-collimator, a half-wave plate, a quarter-wave plate and a vortex half-wave plate that are coaxially and sequentially arranged at intervals. The linearly polarized Gaussian beam emitted by the light source component passes through the beam expander-collimator, the half-wave plate, the quarter-wave plate and the vortex half-wave plate in sequence. Among them, the first orthogonal polarization component weight coefficient and the second orthogonal polarization component weight coefficient are adjusted by adjusting the fast axis angle of the half-wave plate; and / or, The sample stage is provided with a three-dimensional adjustable mechanism, and the three-dimensional adjustable mechanism is configured to make the position of the micro-nano particles in the vector light field adjustable along the x-y-z directions.

9. The device according to claim 7 or 8, characterized in that, The light guiding component includes a mirror and a first objective lens; The vector light field adjusts its propagation direction through the mirror and is incident on the first objective lens, and then penetrates the sample stage through the first objective lens and is focused on the micro-nano particles.

10. The device according to claim 9, characterized in that, The light guiding component further includes a beam splitter disposed between the mirror and the first objective lens, and the vector light field reflected by the mirror is transmitted to the first objective lens through the beam splitter; The imaging component includes an illumination light source, a second objective lens, a light focusing device and a CCD camera. The second objective lens is disposed above the sample stage. The second objective lens focuses the illumination light source on the micro-nano particles. The illumination light source is transmitted through the micro-nano particles, penetrates the sample stage and is incident on the first objective lens, and then is reflected by the beam splitter to the light focusing device, and then imaged on the CCD camera. Among them, the CCD camera is connected to a computer.

Images