Nanoparticle driving device based on space-time modulation

Abstract

The invention provides a nano particle driving device based on space-time modulation, and relates to the technical field of optics. The nanoparticle driving device provided by the embodiment of the invention comprises a laser light source, a deflection module and a polarization modulation module, the laser source is used for emitting laser beams; the deflection module and the polarization modulation module are sequentially arranged on a light path of the laser beam; the deflection module is used for modulating the distribution mode of the laser beams in the propagation direction into discrete spiral distribution; the polarization modulation module is used for modulating the laser beam into a circularly polarized beam; the circularly polarized light beam is used for driving particles to move. According to the nanoparticle driving device provided by the embodiment of the invention, the distribution mode of the propagation direction of the laser beams is modulated into discrete spiral distribution, so that the orbital angular momentum of the particles is changed by a variable electric field of the laser beams; therefore, the circularly polarized light beam output by the nano-particle driving device can change the orbital angular momentum and the spin angular momentum of the particles at the same time, and control over two motion dimensions of the particles is achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical technologies, and in particular, to a nanoparticle driving device based on spatio-temporal modulation. Background Art

[0002] Optical manipulation technology utilizes the electromagnetic force generated by an electric field on nanoparticles at the nanoscale, enabling researchers to manipulate microparticles such as cells in an experiment in a non-contact and low-damage manner using a laser. It has broad application prospects particularly in the fields of microphysics, colloid physics, biomedicine, materials science, etc.

[0003] For the torque manipulation of nanoparticles in an optical field, it is mainly achieved by regulating the magnitudes of the Maxwell stress tensors at different positions of the particles. When the spatial electromagnetic field is non-uniform, the magnitudes of the Maxwell stress tensors at different positions of the particle are non-uniform, and inconsistent forces will be generated at different positions of the particle, resulting in the rotation of the particle. Existing technologies have achieved one-dimensional torque manipulation and rotation of the particle from the spin angular momentum carried by a circularly polarized light field, the orbital angular momentum carried by a vortex light field, a photo-thermal field, and the enhanced effect of plasmon resonance excited by light. However, for the comprehensive control of the torques in the other two dimensions of the particle, current research is not yet perfect. Summary of the Invention

[0004] An embodiment of the present invention provides a nanoparticle driving device based on spatio-temporal modulation. By modulating the distribution pattern of the propagation direction of a laser beam into a discrete spiral distribution, the changing electric field of the laser beam changes the orbital angular momentum of the particle. In addition, a polarization modulation module modulates the laser beam into a circularly polarized beam, and the circularly polarized beam can change the spin angular momentum of the particle. Thus, the circularly polarized beam output by the nanoparticle driving device can change the orbital angular momentum and the spin angular momentum of the particle simultaneously, achieving the control of two motion dimensions of the particle.

[0005] An embodiment of the present invention provides a nanoparticle driving device, including a laser light source, a deflection module, and a polarization modulation module;

[0006] The laser light source is used for emitting a laser beam;

[0007] The deflection module and the polarization modulation module are sequentially arranged on the optical path of the laser beam;

[0008] The deflection module is used for modulating the distribution pattern of the laser beam in the propagation direction into a discrete spiral distribution;

[0009] The polarization modulation module is used for modulating the laser beam into a circularly polarized beam;

[0010] The circularly polarized beam is used for driving the particle to move.

[0011] Optionally, the deflection module includes a first acousto-optic deflection unit and a second acousto-optic deflection unit, which are sequentially located on the optical path of the laser beam;

[0012] The first acousto-optic deflection unit is configured to deflect the propagation direction of the laser beam within a first plane, which is parallel to the propagation direction of the laser beam and the propagation direction of the acoustic wave in the first acousto-optic deflection unit;

[0013] The second acousto-optic deflection unit is configured to deflect the propagation direction of the laser beam within a second plane, which is parallel to the propagation direction of the laser beam and the propagation direction of the acoustic wave in the second acousto-optic deflection unit; the propagation direction of the acoustic wave in the first acousto-optic deflection unit intersects with the propagation direction of the acoustic wave in the second acousto-optic deflection unit.

[0014] Optionally, the deflection module further includes a first polarization modulation unit, which is disposed on the optical path of the laser beam before the first acousto-optic deflection unit;

[0015] The first polarization modulation unit is configured to modulate the laser beam into a linearly polarized beam.

[0016] Optionally, the deflection module further includes an acoustic wave output unit;

[0017] The acoustic wave output unit is configured to output a first acoustic wave to the first acousto-optic deflection unit and a second acoustic wave to the second acousto-optic deflection unit;

[0018] The waveform of the first acoustic wave is a sine wave with a frequency offset modulated by discrete sine, and the waveform of the second acoustic wave is a sine wave with a frequency offset modulated by discrete sine. The phase difference of the frequency offset modulation between the first acoustic wave and the second acoustic wave is .

[0019] Optionally, the deflection module includes a first electro-optic deflection unit and a second electro-optic deflection unit, which are sequentially located on the optical path of the laser beam;

[0020] The first electro-optic deflection unit is configured to deflect the propagation direction of the laser beam within a first plane, which is parallel to the propagation direction of the laser beam and the fast axis direction of the first electro-optic deflection unit;

[0021] The second electro-optic deflection unit is configured to deflect the propagation direction of the laser beam within a second plane, which is parallel to the propagation direction of the laser beam and the fast axis direction of the second electro-optic deflection unit;

[0022] The fast axis direction of the first electro-optic deflection unit intersects with the fast axis direction of the second electro-optic deflection unit.

[0023] Optionally, the deflection module further includes a first polarization modulation unit and a second polarization modulation unit. The first polarization modulation unit is disposed on the optical path of the laser beam before the first electro-optical deflection unit, and the second polarization modulation unit is located on the optical path of the laser beam between the first electro-optical deflection unit and the second electro-optical deflection unit;

[0024] The first polarization modulation unit is used to modulate the laser beam into a first linearly polarized beam;

[0025] The second polarization modulation unit is used to modulate the first linearly polarized beam into a second linearly polarized beam, and the polarization directions of the first linearly polarized beam and the second linearly polarized beam intersect.

[0026] Optionally, the deflection module further includes a voltage output unit;

[0027] The voltage output unit is used to output a first voltage to the first electro-optical deflection unit and a second voltage to the second electro-optical deflection unit;

[0028] The waveform of the first voltage is a discrete sine wave, the waveform of the second voltage is a discrete sine wave, and the phase difference between the first voltage and the second voltage is .

[0029] Optionally, the polarization modulation module includes a quarter-wave plate or a 90° Faraday rotator.

[0030] Optionally, the time-space modulation-based nanoparticle driving device further includes a collimating lens, a beam expanding module, and a beam shrinking module;

[0031] The collimating lens is located on the optical path of the laser beam between the laser light source and the deflection module, and is used to collimate the laser beam;

[0032] The beam expanding module is located on the optical path of the laser beam between the deflection module and the polarization modulation module, and is used to expand the beam diameter of the laser beam;

[0033] The beam shrinking module is located on the optical path of the laser beam after the polarization modulation module, and is used to shrink the beam diameter of the laser beam.

[0034] Optionally, the time-space modulation-based nanoparticle driving device further includes a dichroic mirror, an objective lens, a flow cell, and an image acquisition module;

[0035] The dichroic mirror is located on the optical path of the laser beam after the polarization modulation module, and is used to reflect the laser beam to the objective lens and transmit the image of the particles in the flow cell to the image acquisition module;

[0036] The objective lens is used to converge the laser beam into the flow cell;

[0037] The flow cell is used to hold the particles;

[0038] The image acquisition module is located on the side of the dichroic mirror away from the objective lens and is used to acquire images of the particles in the flow cell.

[0039] In the nanoparticle driving device based on spatio-temporal modulation provided by the embodiments of the present invention, by modulating the distribution mode of the propagation direction of the laser beam into a discrete spiral distribution, the propagation direction of the laser beam changes periodically with time, so that the changing electric field of the laser beam changes the orbital angular momentum of the particles. In addition, the polarization modulation module modulates the laser beam into a circularly polarized beam, and the circularly polarized beam can change the spin angular momentum of the particles, so that the circularly polarized beam output by the nanoparticle driving device can change the orbital angular momentum and the spin angular momentum of the particles at the same time, realizing the control of two motion dimensions of the particles.

[0040] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] Figure 1 is a structural block diagram of a nanoparticle driving device based on spatio-temporal modulation provided by the embodiments of the present invention;

[0043] Figure 2 is a schematic diagram of the light spot of the laser beam output by the deflection module irradiating on the incident surface of the polarization modulation module;

[0044] Figure 3 is a structural schematic diagram of a polarization module provided by the embodiments of the present invention;

[0045] Figure 4 is a structural schematic diagram of another polarization module provided by the embodiments of the present invention;

[0046] Figure 5 is a waveform diagram of a first voltage and a second voltage provided by the embodiments of the present invention;

[0047] Figure 6 is a structural block diagram of another nanoparticle driving device based on spatio-temporal modulation provided by the embodiments of the present invention;

[0048] Figure 7 is a structural block diagram of yet another nanoparticle driving device based on spatio-temporal modulation provided by the embodiments of the present invention;

[0049] Figure 8 It is a relationship diagram of the discrete spiral modulation frequency and the nutation angle of the particle;

[0050] Figures 9 - 14 It is a relationship diagram of the precession angle and the nutation angle of the gold nanorod hexagonal prism at a specific discrete spiral modulation frequency. Specific embodiments

[0051] In order to enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0052] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0053] The embodiment of the present invention provides a nanoparticle driving device based on spatio-temporal modulation, Figure 1 It is a structural block diagram of a nanoparticle driving device based on spatio-temporal modulation provided by the embodiment of the present invention. Refer to Figure 1 , the nanoparticle driving device based on spatio-temporal modulation includes a laser light source 100, a deflection module 200, and a polarization modulation module 300; the laser light source 100 is used to emit a laser beam; the deflection module 200 and the polarization modulation module 300 are sequentially arranged on the optical path of the laser beam; the deflection module 200 is used to modulate the distribution mode of the laser beam in the propagation direction into a discrete spiral distribution; the polarization modulation module 300 is used to modulate the laser beam into a circularly polarized beam; the circularly polarized beam is used to drive the particle to move.

[0054] Refer to Figure 1, the laser light source 100 emits a laser beam, and the deflection module 200 modulates the distribution mode of the laser beam in the propagation direction into a discrete spiral distribution. The propagation direction of the laser beam changes periodically with time, and the propagation directions of the laser beam are discontinuous between different periods of change. Figure 2 is a schematic diagram of the spot where the laser beam output by the deflection module irradiates on the incident surface of the polarization modulation module. Refer to Figure 2 , the spot position where the laser beam irradiates on the incident surface of the polarization modulation module 300 depends on the propagation direction of the laser beam. Within a period of change, the spots where the laser beam irradiates on the incident surface of the polarization modulation module 300 form an ellipse. The laser beam output by the deflection module 200 will be incident on the polarization modulation module 300, and the polarization modulation module 300 modulates the laser beam into a circularly polarized beam. Subsequently, the circularly polarized beam irradiates near the particle, and the changing electric field of the circularly polarized beam will drive the particle to move. The change in the electric field of the circularly polarized beam comes from two aspects: the polarization state and the propagation direction. The change in the electric field caused by the polarization state of the circularly polarized beam will change the spin angular momentum of the particle, and the change in the propagation direction of the circularly polarized beam with time will also cause a change in the electric field around the particle. The change in the electric field caused by the propagation direction of the circularly polarized beam will change the orbital angular momentum of the particle. Thus, the circularly polarized beam can drive the particle to generate various modes of rotational motion.

[0055] Next, the relationship between the motion state of the particle and the electric field is introduced. The optical torque received by the Lorenz-Mie particle can be expressed as:

[0056]

[0057] where is the gradient operator, is the position vector of the particle, is the Maxwell stress tensor, which can be expressed as:

[0058]

[0059] where is the electric field distribution, is the conjugate of the electric displacement vector, is the magnetic induction intensity, is the magnetic field intensity. is the unit tensor, is to take the real part, is the dyadic symbol. According to the above formula, the three-dimensional torque distribution in the laboratory coordinate system received by the nanoparticle at different positions from the center of the laser beam waist and different rotation angles under a given electric field can be solved by numerical calculation methods. Using the ZXZ three-dimensional Euler rotation transformation, the particle coordinate system Three-dimensional torque distribution under is shown as follows:

[0060]

[0061] where is the precession angle, is the nutation angle, is the spin angle. From this, the relationship between the torque distribution of the particle and the electric field can be obtained. For disk-shaped nanoparticles with a relatively high aspect ratio, the geometric anisotropy of its disk plane (i.e., the plane) is not obvious, and the torque distribution will degenerate into . By applying the periodic extension law of the torque during particle rotation , the computational workload of numerical calculations can be reduced.

[0062] After obtaining the torque distribution of the particle, according to the kinematic formula and the rigid body rotation law, the differential equations for the three-dimensional position and rotation angle of the particle as a function of time can be written as follows:

[0063]

[0064] where is the Brownian force, is the inertia tensor, is the angular displacement vector, where the translational drag torque , the rotational drag torque , and are the dynamic viscosity resistance and the viscosity resistance torque coefficient respectively. When the Brownian force is small enough, using this formula to construct the finite difference time domain method for simulation, the motion pattern of the particle as a function of time can be calculated. Among them, the angular displacement vector of the particle needs to be transformed with the Euler angles indexing the three-dimensional torque, and the transformation formula is shown as follows:

[0065]

[0066] where is the rotation matrix for Euler rotation in the x direction, is the rotation matrix for Euler rotation in the y direction, is the rotation matrix for ZXZ Euler rotation. The Euler angles of the latest time step are obtained by superimposing the three-dimensional angular displacements of all previous time steps. According to the above formula, the relationship between the electric field of the laser beam and the motion state of the particle can be obtained.

[0067] The nanoparticle driving device based on spatio-temporal modulation provided by the embodiments of the present invention modulates the distribution mode of the laser beam in the propagation direction into a discrete spiral distribution, so that the propagation direction of the laser beam changes periodically with time, and thus the changing electric field of the laser beam changes the orbital angular momentum of the particle. In addition, the polarization modulation module modulates the laser beam into a circularly polarized beam, and the circularly polarized beam can change the spin angular momentum of the particle, so that the circularly polarized beam output by the nanoparticle driving device can change the orbital angular momentum and the spin angular momentum of the particle at the same time, realizing the control of two motion dimensions of the particle.

[0068] Figure 3 is a schematic structural diagram of a polarization module provided by the embodiments of the present invention. Refer to Figure 3 , the deflection module includes a first acousto-optic deflection unit 201 and a second acousto-optic deflection unit 202, and the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202 are sequentially located on the optical path of the laser beam; the first acousto-optic deflection unit 201 is used to deflect the propagation direction of the laser beam in a first plane, and the first plane is parallel to the propagation direction S1 of the laser beam and the acoustic wave propagation direction S4 of the first acousto-optic deflection unit; the second acousto-optic deflection unit 202 is used to deflect the propagation direction of the laser beam in a second plane, and the second plane is parallel to the propagation direction of the second laser beam S2 and the acoustic wave propagation direction S5 of the second acousto-optic deflection unit; the acoustic wave propagation direction S4 of the first acousto-optic deflection unit 201 intersects with the acoustic wave propagation direction S5 of the second acousto-optic deflection unit 202.

[0069] Refer to Figure 3 , the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202 include acousto-optic crystals. By applying acoustic waves to the acousto-optic crystals, the refractive index of the acousto-optic crystals can be changed. Therefore, by controlling the acoustic waves applied to the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202, the refractive indices of the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202 can be controlled, so as to control the propagation direction of the laser beam passing through the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202. Figure 3In the first acousto-optic deflection unit 201, the first laser beam S1 can be deflected within a first plane. The first plane can be determined by the propagation direction of the first laser beam S1 and the acoustic wave propagation direction S4 of the first acousto-optic deflection unit. After passing through the first acousto-optic deflection unit 201, the first laser beam S1 becomes the second laser beam S2. With different acoustic wave intensities applied to the first acousto-optic deflection unit 201, the degree of deflection of the propagation direction of the first laser beam S1 after passing through the first acousto-optic deflection unit 201 is also different. The propagation direction of the second laser beam S2 includes multiple propagation directions. By controlling the acoustic wave intensity applied to the first acousto-optic deflection unit 201, the propagation direction of the laser beam can be deflected to any of the propagation directions included in the propagation direction of the second laser beam S2. Then, after the second laser beam S2 passes through the second acousto-optic deflection unit 202, it becomes the third laser beam S3. The second acousto-optic deflection unit 202 can deflect the propagation direction of the second laser beam S2 within a second plane. The second plane can be determined by the propagation direction of the second laser beam S2 and the acoustic wave propagation direction S5 of the second acousto-optic deflection unit 202. Similarly, with different acoustic wave intensities applied to the second acousto-optic deflection unit 202, the degree of deflection of the propagation direction of the second laser beam S2 after passing through the second acousto-optic deflection unit 202 is also different. The propagation direction of the third laser beam S3 includes all possible propagation directions of the first laser beam S1 after passing through the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202. To enable the deflection module to modulate the propagation direction of the laser beam in two directions, the acoustic wave propagation direction S4 of the first acousto-optic deflection unit 201 and the acoustic wave propagation direction S5 of the second acousto-optic deflection unit 202 need to intersect.

[0070] To simplify the control logic of the acoustic waves applied to the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202, the acoustic wave propagation direction S4 of the first acousto-optic deflection unit 201 and the acoustic wave propagation direction S5 of the second acousto-optic deflection unit 202 can be set to be perpendicular. Thus, the first plane and the second plane are also perpendicular to each other, and the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202 respectively deflect the propagation direction of the laser beam in two mutually perpendicular directions. By controlling the acoustic wave waveforms applied to the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202, the distribution pattern of the laser beam in the propagation direction can be modulated into a discrete spiral distribution in the time domain. Then, the third laser beam S3 is modulated into a circularly polarized beam by the polarization modulation module 300.

[0071] Reference Figure 3, the deflection module further includes a first polarization modulation unit 203, and the first polarization modulation unit 203 is disposed on the optical path of the laser beam before the first acousto-optic deflection unit 201; the first polarization modulation unit 203 is configured to modulate the laser beam into a linearly polarized beam. The principle of deflecting the propagation direction of the laser beam by the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202 is based on the acousto-optic effect, that is, the acoustic wave causes a periodic change in the refractive index of the acousto-optic crystal, thereby forming a Bragg grating. Modulating the laser beam into a linearly polarized light can improve the diffraction efficiency of the Bragg grating, thereby improving the deflection efficiency of the first acousto-optic deflection unit 201 and the second acousto-optic deflection unit 202 for the propagation direction of the laser beam.

[0072] Optionally, the deflection module further includes an acoustic wave output unit; the acoustic wave output unit is configured to output a first acoustic wave to the first acousto-optic deflection unit and a second acoustic wave to the second acousto-optic deflection unit; the waveform of the first acoustic wave is a sine wave whose frequency offset is discretely sinusoidally modulated, and the waveform of the second acoustic wave is a sine wave whose frequency offset is discretely sinusoidally modulated. The phase difference of the frequency offset modulation between the first acoustic wave and the second acoustic wave is .

[0073] The sampling frequencies of the frequency offset modulations of the first acoustic wave and the second acoustic wave are both , T is the period of the frequency offset modulations of the first acoustic wave and the second acoustic wave, and the periods of the frequency offset modulations of the first acoustic wave and the second acoustic wave are equal. The higher the frequency of the first acoustic wave, the greater the degree of deflection of the propagation direction of the laser beam by the first acousto-optic deflection unit. The higher the frequency of the second acoustic wave, the greater the degree of deflection of the propagation direction of the laser beam by the second acousto-optic deflection unit. Therefore, when the phase difference of the frequency offset modulations between the first acoustic wave and the second acoustic wave is , when the frequency of the first acoustic wave reaches the peak value, the frequency of the second acoustic wave reaches the valley value; when the frequency of the second acoustic wave reaches the peak value, the frequency of the first acoustic wave reaches the valley value. Thus, the change trend of the propagation direction of the laser beam output by the deflection module is a spiral distribution, and the light spots of the laser beam irradiated on the incident surface of the polarization modulation module form an ellipse. When the peak intensities of the first acoustic wave and the second acoustic wave are equal, the light spots of the laser beam irradiated on the incident surface of the polarization modulation module form a circle.

[0074] Figure 4 is a schematic structural diagram of another polarization module provided by an embodiment of the present invention. Refer to Figure 4, the deflection module includes a first electro-optic deflection unit 204 and a second electro-optic deflection unit 205. The first electro-optic deflection unit 204 and the second electro-optic deflection unit 205 are sequentially located on the optical path of the laser beam. The first electro-optic deflection unit 204 is configured to deflect the propagation direction of the laser beam within a first plane, and the first plane is parallel to the propagation direction of the laser beam and the fast axis direction S6 of the first electro-optic deflection unit. The second electro-optic deflection unit 205 is configured to deflect the propagation direction of the laser beam within a second plane, and the second plane is parallel to the propagation direction of the laser beam and the fast axis direction S7 of the second electro-optic deflection unit. The fast axis direction S6 of the first electro-optic deflection unit 204 intersects with the fast axis direction S7 of the second electro-optic deflection unit 205.

[0075] Reference Figure 4 , the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205 include electro-optic crystals. By applying a voltage to the electro-optic crystals, the electro-optic crystals can exhibit the birefringence effect, changing the refractive index of the electro-optic crystals, thereby deflecting the propagation direction of the laser beam in the electro-optic crystals. Thus, by controlling the voltages applied to the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205, the refractive indices of the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205 can be controlled, thereby controlling the propagation direction of the laser beam passing through the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205. Figure 4 In [reference], the first electro-optic deflection unit 204 can deflect the propagation direction of the laser beam within a first plane. When the laser beam irradiates on the incident surface of the second electro-optic deflection unit 205, there is an offset of Δx in the x direction of the laser beam spot. The first plane can be determined by the propagation direction of the laser beam at this time and the fast axis direction S6 of the first electro-optic deflection unit. Different voltage intensities are applied to the first electro-optic deflection unit 204, and the deflection degree of the propagation direction of the laser beam after passing through the first electro-optic deflection unit 204 is also different. The second electro-optic deflection unit 205 can deflect the propagation direction of the laser beam within a second plane, so that the projection of the laser beam spot on the x-y plane has an offset of Δy in the y direction. The second plane can be determined by the propagation direction of the laser beam at this time and the fast axis direction S7 of the second electro-optic deflection unit 205. Similarly, different voltage intensities are applied to the second electro-optic deflection unit 205, and the deflection degree of the propagation direction of the laser beam after passing through the second electro-optic deflection unit 205 is also different. To enable the deflection module to modulate the propagation direction of the laser beam in two directions, the fast axis direction S6 of the first electro-optic deflection unit 204 and the fast axis direction S7 of the second electro-optic deflection unit 205 need to intersect.

[0076] To simplify the control logic of the voltages applied to the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205, the fast-axis direction S6 of the first electro-optic deflection unit 204 and the fast-axis direction S7 of the second electro-optic deflection unit 205 can be set to be perpendicular. Thus, the first plane and the second plane are also perpendicular to each other, and the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205 respectively deflect the propagation direction of the laser beam in two mutually perpendicular directions. By controlling the voltage waveforms applied to the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205, the distribution pattern of the laser beam in the propagation direction can be modulated into a discrete spiral distribution in the time domain. Then, the laser beam is modulated into a circularly polarized beam by the polarization modulation module 300.

[0077] Reference Figure 4 , the deflection module further includes a first polarization modulation unit 203 and a second polarization modulation unit 206. The first polarization modulation unit 203 is disposed on the optical path of the laser beam before the first electro-optic deflection unit 204, and the second polarization modulation unit 206 is located on the optical path of the laser beam between the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205; the first polarization modulation unit 203 is used to modulate the laser beam into a first linearly polarized beam S8; the second polarization modulation unit 206 is used to modulate the first linearly polarized beam S8 into a second linearly polarized beam S9, and the polarization directions of the first linearly polarized beam S8 and the second linearly polarized beam S9 intersect.

[0078] Reference Figure 4 , since the first electro-optic deflection unit 204 and the second electro-optic deflection unit 205 have a birefringence effect, in order to ensure that the refractive indices of the polarization components of the laser beam in the first electro-optic deflection unit 204 are consistent, and the refractive indices of the polarization components of the laser beam in the second electro-optic deflection unit 205 are consistent, it is necessary to ensure that the first linearly polarized beam S8 and the second linearly polarized beam S9 are linearly polarized beams, and the first linearly polarized beam S8 is parallel to the fast-axis direction S6 of the first electro-optic deflection unit 204, and the polarization direction of the second linearly polarized beam S9 is parallel to the fast-axis direction S7 of the second electro-optic deflection unit 205. The laser beam is incident on the first polarization modulation unit 203 and becomes the first linearly polarized beam S8. The polarization direction of the first linearly polarized beam S8 is parallel to the fast-axis direction S6 of the first electro-optic deflection unit. After the first linearly polarized beam S8 is incident on the second polarization modulation unit 206, it becomes the second linearly polarized beam S9. The polarization direction of the second linearly polarized beam S9 is parallel to the fast-axis direction S7 of the second electro-optic deflection unit 205. Thus, there is no birefringence effect of the first linearly polarized beam S8 in the first electro-optic deflection unit 204, and there is no birefringence effect of the second linearly polarized beam S9 in the second electro-optic deflection unit 205.

[0079] Optionally, the deflection module further includes a voltage output unit; the voltage output unit is used to output a first voltage to the first electro-optical deflection unit and output a second voltage to the second electro-optical deflection unit; the waveform of the first voltage is a discrete sine wave, the waveform of the second voltage is a discrete sine wave, and the phase difference between the first voltage and the second voltage is .

[0080] Figure 5 is a waveform diagram of a first voltage and a second voltage provided by an embodiment of the present invention, with reference to Figure 5 , the first voltage V x and the second voltage V y The sampling frequencies are , where T is the first voltage V x and the second voltage V y cycle, the first voltage V x and the second voltage V y The period of the second voltage V y The phase ratio of the first voltage V x The phase is advanced The first voltage V x The greater the intensity of the first acousto-optic deflection unit, the greater the degree of deflection of the laser beam propagation direction, and the second voltage V y The greater the intensity, the greater the degree of deflection of the propagation direction of the laser beam by the second acousto-optic deflection unit. Figure 5 The first voltage V x When the intensity of the second voltage V y The intensity of the second voltage V y When the intensity reaches the peak value, the first voltage V x The intensity is 0. Therefore, the change trend of the propagation direction of the laser beam output by the deflection module is spiral distribution, and the spot of the laser beam irradiated on the incident surface of the polarization modulation module forms an ellipse. x and the second voltage V y When the peak intensities are equal, the spot of the laser beam irradiated on the incident surface of the polarization modulation module forms a circle.

[0081] refer to Figure 1 , Figure 3 and Figure 4 , the polarization modulation module includes a quarter wave plate or a 90° Faraday rotator. Figure 3 The third laser beam S3 and Figure 4 The third linear polarized beam S10 in the image is a linear polarized beam. When the fast axis of the quarter wave plate forms a 45° angle with the polarization direction of the linear polarized beam, the quarter wave plate can output a circularly polarized beam. The 90° Faraday rotator can also Figure 3 The third laser beam S3 in Figure 4The third linearly polarized light beam S10 in is modulated into a circularly polarized light beam.

[0082] Figure 6 It is a structural block diagram of another nano-particle driving device based on spatio-temporal modulation provided by an embodiment of the present invention. Refer to Figure 6 , the nano-particle driving device based on spatio-temporal modulation further includes a collimating lens 400, a beam expanding module 501 and a beam shrinking module 502; the collimating lens 400 is located on the optical path of the laser beam between the laser light source 100 and the deflection module 200, and is used for collimating the laser beam; the beam expanding module 501 is located on the optical path of the laser beam between the deflection module 200 and the polarization modulation module 300, and is used for expanding the beam diameter of the laser beam; the beam shrinking module 502 is located on the optical path of the laser beam after the polarization modulation module 300, and is used for shrinking the beam diameter of the laser beam.

[0083] Refer to Figure 6 , the collimating lens 400 can modulate the laser beam into a parallel beam to ensure that the laser beam does not diverge during propagation. The beam expanding module 501 can expand the beam diameter of the laser beam to a size suitable for the polarization modulation module 300, reduce the power density of the laser beam, and avoid damaging the device. The beam shrinking module 502 can shrink the beam diameter of the laser beam. The beam expanding module 501 and the beam shrinking module 502 can improve the scalability of the device and facilitate the insertion of other devices.

[0084] Figure 7 It is a structural block diagram of another nano-particle driving device based on spatio-temporal modulation provided by an embodiment of the present invention. Refer to Figure 7 , the nano-particle driving device based on spatio-temporal modulation further includes a dichroic mirror 600, an objective lens 700, a flow cell 800 and an image acquisition module 900; the dichroic mirror 600 is located on the optical path of the laser beam after the polarization modulation module 300, and is used for reflecting the laser beam to the objective lens 700 and transmitting the image of the particles in the flow cell 800 to the image acquisition module 900; the objective lens 700 is used for converging the laser beam into the flow cell 800; the flow cell 800 is used for accommodating particles; the image acquisition module 900 is located on the side of the dichroic mirror 600 away from the objective lens, and is used for acquiring the image of the particles in the flow cell 800.

[0085] Refer to Figure 7 , the dichroic mirror 600 has a high reflectivity characteristic for the laser beam and can reflect the laser beam to the objective lens 700. After the objective lens 700 converges the laser beam, the laser beam enters the flow cell 800. The particles are located in the flow cell, and the electric field of the laser beam can change the motion state of the particles. The dichroic mirror 600 has a high transmittance characteristic for the image of the particles, and the image acquisition module 900 can receive and display the image of the particles.

[0086] For example, a nano-gold hexagonal prism with a side length of 100 nm and a height of 20 nm (diameter of 200 nm) is used as the driven particle. When the power of the laser beam incident on the flow cell is 3 mW, the discrete spiral modulation frequency of the left-handed circularly polarized light is Under this condition, the nanogold hexagonal prism will rotate periodically along different rotation modes. It is the inverse of the period of change of the propagation direction of the laser beam. Figure 8 is the relationship between the discrete spiral modulation frequency and the particle's nutation angle, Figures 9 - 14 This is the relationship between the precession angle and the nutation angle of the nanogold hexagonal prism at a specific discrete spiral modulation frequency. Figures 8 to 14 , Figure 8 The horizontal axis is the discrete spiral modulation frequency , the ordinate is the nutation angle of the particle, the purple curve is the minimum nutation angle, the blue curve is the average nutation angle, and the green curve is the maximum nutation angle. Figures 9 - 14 The number in the middle and lower part is the discrete spiral modulation frequency , the radial coordinate is the precession angle of the particle, and the circumferential coordinate is the nutation angle of the particle. When the nanogold hexagonal prism is in an upright horizontal state, it is equivalent to Figures 9 - 14 The origin position in the particle; when the nutation angle of the particle is When the nanogold hexagonal prism is in an inverted state. Figures 9 - 14 The coloring of each position on the middle line segment reflects the spin rotation rate of the particle at each time. , blue represents reverse spin, and orange represents forward spin. When the modulation frequency of the laser is low, that is, When RPS <33.4, the nanogold hexagonal prism will rotate at a fixed angle. When the laser modulation frequency is high, that is, When RPS>33.4, the nano-gold hexagonal prism will The interval near it oscillates periodically and maintains a positive spin speed to spin, where is the precession angle, is the nutation angle. When the discrete spiral modulation frequency When in the range of 33.4RPS-121RPS, the nano-gold hexagonal prisms will undergo more complex periodic changes and follow the discrete spiral modulation frequency. With the change of , its rotation state will undergo a more complex pattern change.

[0087] In addition, the discrete spiral modulation frequency of left-handed circularly polarized light can be adjusted To control the nutation angle The period variation range. In the discrete spiral modulation frequency When it is less than 33.4 RPS, we can control the discrete spiral modulation frequency to adjust the minimum nutation angle of the periodic motion of the gold nanorod hexagonal prism . When the discrete spiral modulation frequency increases, it increases steadily. When the discrete spiral modulation frequency is greater than 121 RPS, we can control the discrete spiral modulation frequency to adjust the maximum nutation angle of the periodic motion of the gold nanorod hexagonal prism , and when it increases, it decreases steadily. Thus, the three-dimensional multimodal torque of the disk-shaped nanoparticles at the center of the discrete spiral circularly polarized light can be realized.

[0088] The above specific implementation manners do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A nanoparticle driving device based on spatio-temporal modulation, characterized in that, It includes a laser light source, a deflection module, and a polarization modulation module; The laser light source is used to emit a laser beam; The deflection module and the polarization modulation module are sequentially arranged on the optical path of the laser beam; The deflection module is used to modulate the distribution mode of the laser beam in the propagation direction into a discrete spiral distribution; The polarization modulation module is used to modulate the laser beam into a circularly polarized beam; The circularly polarized beam is used to drive the movement of the particles.

2. The nanoparticle driving device based on spatio-temporal modulation according to claim 1, wherein The deflection module includes a first acousto-optic deflection unit and a second acousto-optic deflection unit, and the first acousto-optic deflection unit and the second acousto-optic deflection unit are sequentially located on the optical path of the laser beam; The first acousto-optic deflection unit is used to deflect the propagation direction of the laser beam in a first plane, and the first plane is parallel to the propagation direction of the laser beam and the acoustic wave propagation direction in the first acousto-optic deflection unit; The second acousto-optic deflection unit is used to deflect the propagation direction of the laser beam in a second plane, and the second plane is parallel to the propagation direction of the laser beam and the acoustic wave propagation direction in the second acousto-optic deflection unit; the acoustic wave propagation direction in the first acousto-optic deflection unit intersects with the acoustic wave propagation direction in the second acousto-optic deflection unit.

3. The nanoparticle driving device based on spatio-temporal modulation according to claim 2, wherein, The deflection module further includes a first polarization modulation unit, and the first polarization modulation unit is arranged on the optical path of the laser beam before the first acousto-optic deflection unit; The first polarization modulation unit is used to modulate the laser beam into a linearly polarized beam.

4. The nanoparticle driving device based on spatio-temporal modulation according to claim 2, wherein The deflection module further includes an acoustic wave output unit; The acoustic wave output unit is used to output a first acoustic wave to the first acousto-optic deflection unit and a second acoustic wave to the second acousto-optic deflection unit; The waveform of the first acoustic wave is a sine wave with a frequency offset modulated by discrete sine waves, the waveform of the second acoustic wave is a sine wave with a frequency offset modulated by discrete sine waves, and the phase difference of the frequency offset modulation between the first acoustic wave and the second acoustic wave is .

5. The nanoparticle driving device based on spatio-temporal modulation according to claim 1, characterized in that The deflection module includes a first electro-optic deflection unit and a second electro-optic deflection unit, and the first electro-optic deflection unit and the second electro-optic deflection unit are sequentially located on the optical path of the laser beam; The first electro-optic deflection unit is used to deflect the propagation direction of the laser beam in a first plane, and the first plane is parallel to the propagation direction of the laser beam and the fast axis direction of the first electro-optic deflection unit; The second electro-optic deflection unit is used to deflect the propagation direction of the laser beam in a second plane, and the second plane is parallel to the propagation direction of the laser beam and the fast axis direction of the second electro-optic deflection unit; The fast axis direction of the first electro-optic deflection unit intersects with the fast axis direction of the second electro-optic deflection unit.

6. The nanoparticle driving device based on spatio-temporal modulation according to claim 5, wherein The deflection module further includes a first polarization modulation unit and a second polarization modulation unit. The first polarization modulation unit is arranged on the optical path of the laser beam before the first electro-optic deflection unit, and the second polarization modulation unit is located on the optical path of the laser beam between the first electro-optic deflection unit and the second electro-optic deflection unit; The first polarization modulation unit is used to modulate the laser beam into a first linearly polarized beam; The second polarization modulation unit is used to modulate the first linearly polarized beam into a second linearly polarized beam, and the polarization direction of the first linearly polarized beam intersects with the polarization direction of the second linearly polarized beam.

7. The nanoparticle driving device based on spatio-temporal modulation according to claim 5, characterized in that The deflection module further includes a voltage output unit; The voltage output unit is configured to output a first voltage to the first electro-optical deflection unit and a second voltage to the second electro-optical deflection unit; The waveform of the first voltage is a discrete sine wave, the waveform of the second voltage is a discrete sine wave, and the phase difference between the first voltage and the second voltage is .

8. The nanoparticle driving device based on spatio-temporal modulation according to claim 1, wherein, The polarization modulation module includes a quarter-wave plate or a 90° Faraday rotator.

9. The nanoparticle driving device based on spatio-temporal modulation according to claim 1, wherein The time-space modulation-based nanoparticle driving device further includes a collimating lens, a beam expanding module, and a beam shrinking module; The collimating lens is located on the optical path of the laser beam between the laser light source and the deflection module, and is configured to collimate the laser beam; The beam expanding module is located on the optical path of the laser beam between the deflection module and the polarization modulation module, and is configured to expand the beam diameter of the laser beam; The beam shrinking module is located on the optical path of the laser beam after the polarization modulation module, and is configured to shrink the beam diameter of the laser beam.

10. The nanoparticle driving device based on spatio-temporal modulation according to claim 1, characterized in that, The time-space modulation-based nanoparticle driving device further includes a dichroic mirror, an objective lens, a flow cell, and an image acquisition module; The dichroic mirror is located on the optical path of the laser beam after the polarization modulation module, and is configured to reflect the laser beam to the objective lens and transmit the image of the particles in the flow cell to the image acquisition module; The objective lens is configured to converge the laser beam into the flow cell; The flow cell is configured to accommodate particles; The image acquisition module is located on the side of the dichroic mirror away from the objective lens, and is configured to acquire the image of the particles in the flow cell.

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