A holographic vacuum optical tweezers device based on circular Airy beam

Abstract

The present invention discloses a holographic vacuum optical tweezers device based on a circular Airy beam. The modulated beam generating assembly of the present invention generates a modulated beam, which is incident on a spectrometer after passing through a 4F system. The transmitted beam through the spectrometer is then reflected by a first reflector and then incident on a vacuum chamber, and then converged by a third convex lens to form a first circular Airy beam; the reflected beam through the spectrometer is reflected by a second reflector and a third reflector in turn and then incident on a vacuum chamber, and then converged by a fourth convex lens to form a second circular Airy beam. The first circular Airy beam and the second circular Airy beam are arranged opposite to each other in the vacuum chamber to form a light trap capture area. Micro-nanoparticles are captured in the light trap capture area and are stably suspended in a high vacuum environment. The present invention improves the stability of optical tweezers in capturing micro-nanoparticles in a high vacuum environment, can achieve the capture of micro-nanoparticles with larger mass, and is conducive to further improving the vacuum degree and acceleration measurement accuracy of the vacuum optical tweezers system.

Description

Technical Field

[0001] The invention relates to a holographic vacuum optical tweezers device, in particular to a holographic vacuum optical tweezers device based on a circular Airy beam. Background Art

[0002] In 1970, Ashkin et al. first observed the interaction between lasers and micron-sized objects. Using two counter-propagating light beams, they trapped a small sphere in a solution, laying the foundation for optical tweezers. In 1986, Ashkin used a single light beam to stably capture microspheres of varying sizes in three dimensions, giving rise to the technique known as optical tweezers. Ashkin was awarded the 2018 Nobel Prize in Physics for his contributions to optical tweezers. Unlike mechanical tweezers, which directly grasp and move objects, optical tweezers typically use a strongly focused light beam to generate a force gradient to capture and manipulate objects. Optical tweezers are non-contact, non-destructive, and offer high precision. They can generate forces as small as a few piconewtons and can capture and manipulate objects at the micron and nanometer scales. They have become an essential tool for capturing and manipulating mesoscopic objects and are widely used to capture and manipulate tiny objects such as cold atoms, biomacromolecules, and cells.

[0003] As a new development direction in optical tweezers technology, vacuum optical tweezers suspend micro- and nanoparticles in a vacuum environment, reducing the thermal noise generated by collisions between particles and surrounding molecules. This allows vacuum optical tweezers systems to be used for precise measurements of mechanical quantities such as weak forces, accelerations, and torques. Furthermore, vacuum optical tweezers can be applied to cutting-edge fundamental research, such as the study of macroscopic quantum states and anomalous gravitational measurements. Typically, vacuum optical tweezers systems achieve ultra-high sensitivity sensing of mechanical quantities by detecting the displacement of trapped particles. Therefore, the higher the vacuum level achieved and the lower the ambient thermal noise, the higher the measurement accuracy. To achieve stable particle capture in even higher vacuum levels, lower optical power is required to generate sufficient gradient force to prevent particle escape due to heating from the high-power beam in a high vacuum environment. Furthermore, given a constant pressure around the particle, theory shows that acceleration measurement sensitivity (the minimum measurable acceleration per unit time) is inversely proportional to particle mass. Therefore, using larger particles with greater mass can measure smaller accelerations and achieve higher acceleration measurement accuracy. However, when the particle size increases to the micrometer level, the laser's heating effect on the particle becomes more significant, making it extremely easy for large particles to escape in a vacuum. Therefore, it is necessary to maximize the rigidity of the optical trap while limiting the trapping light power.

[0004] To address the limited capture intensity and insufficient particle manipulation flexibility of Gaussian beam tweezers, holographic technology is used to manipulate the light field, achieving superior particle capture and manipulation performance. Holographic optical tweezers utilize computational holograms loaded onto devices such as optical metasurfaces or liquid crystal spatial light modulators to modulate the amplitude, phase, and polarization distribution of the incident light field, creating dynamic multi-trap arrays or specialized beam tweezers.

[0005] In 2010, Efremidis et al. proposed a special beam called a circular Airy beam, the field distribution of which on the incident plane can be expressed as: , in the above formula r represents the radius, r 0 represents the radius of the main ring of the beam, Airy is the Airy function, w 0 is the proportional coefficient, α is the attenuation coefficient.

[0006] Circular Airy beams can be generated by spatial light modulators and exhibit abrupt self-focusing properties: after propagating for a certain distance, the beam converges to its center, with the intensity suddenly increasing to a maximum at the self-focusing focal point. This means that circular Airy beams can generate a stronger intensity gradient force, resulting in a stiffer optical trap. Furthermore, the self-focusing effect of circular Airy beams can be enhanced by introducing other variables. Therefore, when using a circular Airy beam as a trapping beam, a lower optical power is required to achieve the same trapping stiffness as a Gaussian beam, thereby reducing heating effects and the probability of particle escape. This allows for the capture of micro- and nanoparticles at higher vacuum levels and improves system measurement accuracy. When the trapping optical power remains the same, using a circular Airy beam can achieve a stronger trapping stiffness, allowing for the capture of larger particles and improving measurement accuracy. Research has shown that the axial scattering force exerted by a circular Airy beam on particles is generally greater than the gradient force. Therefore, methods such as dual-beam counter-beaming must be employed to offset the axial scattering force to achieve three-dimensional particle trapping in a vacuum. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to propose a holographic vacuum optical tweezers device based on a circular Airy beam, which can achieve stable capture of micro-nanoparticles in a higher vacuum environment, further improve the vacuum degree and measurement accuracy of the vacuum optical tweezers system, and has practical application value.

[0008] In order to achieve the above objectives, the specific technical solutions adopted by the present invention are as follows:

[0009] The present invention includes a vacuum chamber, a modulated light beam generating component, a 4F system, a spectroscope, a first reflector, a second reflector, a third reflector, a third convex lens, a fourth convex lens and a detection component; the micro-nano particles, the third convex lens and the fourth convex lens are all placed in the vacuum chamber; the modulated light beam emitted by the modulated light beam generating component is incident on the spectroscope after passing through the 4F system; the transmitted light beam passing through the spectroscope is reflected by the first reflector and then incident on the vacuum chamber, and then converged by the third convex lens in the vacuum chamber to form a first circular Airy beam; the reflected light beam passing through the spectroscope is reflected by the second reflector and the third reflector in sequence and then incident on the vacuum chamber, and then converged by the fourth convex lens in the vacuum chamber to form a second circular Airy beam; the first circular Airy beam and the second circular Airy beam are arranged to face each other in the vacuum chamber and form a light trap capture area, the micro-nano particles are captured in the light trap capture area and are stably suspended in a high vacuum environment; the detection component is arranged on the side of the vacuum chamber and is used to detect the movement of the micro-nano particles.

[0010] The modulated beam generating component includes a first laser, a half-wave plate, a polarization beam splitter and a spatial light modulator; the captured laser beam emitted from the first laser is modulated along the optical axis by transmission through the half-wave plate, transmission through the polarization beam splitter and reflection from the spatial light modulator to generate a modulated beam, which carries the phase hologram information of the circular Airy beam.

[0011] The 4F system includes a first convex lens, an aperture, and a second convex lens; the modulated light beam generating component modulates the light beam along the optical axis and passes through the first convex lens, the aperture, and the second convex lens in sequence before being incident on the beam splitter; the distance between the first convex lens and the modulated light beam generating component, the distance between the first convex lens and the aperture, and the distance between the aperture and the second convex lens are all focal lengths F.

[0012] The distance traveled by the light beam converged by the second convex lens and then passing through the beam splitter and the first reflector to finally reach the front focal plane of the third convex lens is equal to the focal length F;

[0013] The distance traveled by the light beam converged by the second convex lens and finally reaching the front focal plane of the fourth convex lens after passing through the beam splitter, the second reflector and the third reflector is also equal to the focal length F.

[0014] The detection assembly includes a second laser, a fifth convex lens, a sixth convex lens and a four-quadrant detector; the detection laser beam emitted from the second laser is irradiated onto the captured micro-nanoparticles in the vacuum chamber after passing through the fifth convex lens, and the light beam scattered by the captured micro-nanoparticles is collected by the sixth convex lens and incident on the center of the four-quadrant detector.

[0015] An optical window for light beams to pass through is provided on the wall of the vacuum chamber, and an anti-reflection film is coated in the optical window.

[0016] The shapes of the micro-nano particles include sphere, ellipsoid, rod and dumbbell.

[0017] The size of the micro-nanoparticles in three dimensions of space ranges from several nanometers to hundreds of micrometers.

[0018] The spatial light modulator also applies phase hologram information of other special light beams, which are one of the following: Airy beam, vortex beam, Bessel beam, radially polarized beam, angularly polarized beam, and special light field distribution beam derived from the above beams.

[0019] In the present invention, the device outputs a capture laser beam through a first laser, which is modulated by a linear polarization state and a spatial light modulator and then split into two by a spectroscope. After being Fourier transformed by a convex lens, two circular Airy beams are obtained, which are self-focused in a vacuum cavity to form opposing double-beam vacuum holographic optical tweezers; a support device for micro-nanoparticles is located in the vacuum cavity and is used to provide captured particles; a second laser outputs a detection laser beam, and the wavelength of the detection laser is usually different from that of the capture laser. After being focused by a convex lens, it is irradiated on the captured micro-nanoparticles. After being scattered by the particles, the light beam is collected by another convex lens and incident on a four-quadrant detector, forming a particle displacement detection module; the particle displacement is calculated by the detection result of the four-quadrant detector, and the mechanical sensing quantities such as the three-axis stiffness and acceleration of the light trap can be obtained through calibration.

[0020] Compared with the prior art, the beneficial effects of the present invention include at least:

[0021] 1. The present invention adopts a dual-beam horizontal opposing structure to offset the axial scattering force on micro-nanoparticles, eliminating the defect of circular Airy beams that cannot achieve stable capture due to the axial scattering force being greater than the gradient force. By constructing a three-dimensional light trap using only the gradient force, it can capture micro-nanoparticles with larger mass and improve the accuracy of acceleration detection.

[0022] 2. The present invention proposes for the first time a holographic vacuum optical tweezers device based on a circular Airy beam. Compared with traditional vacuum optical tweezers using Gaussian beams, vacuum optical tweezers using a circular Airy beam can generate a greater gradient force at the same power, increase the stiffness of the optical trap, improve the stability of the optical tweezers in capturing micro-nanoparticles in a high vacuum environment, reduce the escape probability of micro-nanoparticles, and achieve the capture of micro-nanoparticles with larger mass, which is conducive to further improving the vacuum degree and measurement accuracy of the vacuum optical tweezers system.

[0023] Therefore, the present invention has practical application value and can improve the capture stability, intracavity vacuum degree and acceleration measurement accuracy of the vacuum optical tweezers system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the optical path of the device of the present invention.

[0025] Figure 2 is the intensity distribution diagram of the circular Airy beam.

[0026] In the figure: first laser 1, half-wave plate 2, polarization beam splitter 3, spatial light modulator 4, first convex lens 5, aperture 6, second convex lens 7, beam splitter 8, first reflector 9, third reflector 10, second reflector 11, third convex lens 12, fourth convex lens 13, micro-nanoparticles 14, second laser 15, fifth convex lens 16, sixth convex lens 17, four-quadrant detector 18, vacuum chamber 19. DETAILED DESCRIPTION

[0027] The following embodiments will further illustrate the present invention with reference to the accompanying drawings:

[0028] Example 1

[0029] like Figure 1 and Figure 2 As shown, the present invention includes a vacuum chamber 19, a modulated light beam generating component, a 4F system, a spectroscope 8, a first reflector 9, a second reflector 11, a third reflector 10, a third convex lens 12, a fourth convex lens 13 and a detection component; the modulated light beam generating component, the 4F system and the spectroscope 8 are arranged in sequence along the optical axis, the micro-nanoparticles 14, the third convex lens 12 and the fourth convex lens 13 are all placed in the vacuum chamber 19, and an optical window for light beam transmission is opened on the cavity wall of the vacuum chamber 19, and the optical window is coated with an anti-reflection film of the corresponding wavelength. The modulated light beam emitted by the modulated light beam generating component carries the phase hologram information of the circular Airy beam. After passing through the 4F system, it is incident on the beam splitter 8. The transmitted light beam through the beam splitter 8 is then reflected by the first reflector 9 and passes through the anti-reflection film on the optical window before entering the vacuum chamber 19. It is then converged by the third convex lens 12 in the vacuum chamber 19 to form a first circular Airy beam. The reflected light beam through the beam splitter 8 is then reflected by the second reflector 11 and the third reflector 10 in sequence and passes through the anti-reflection film on the optical window before entering the vacuum chamber 19. It is then converged by the fourth convex lens 13 in the vacuum chamber 19 to form a second circular Airy beam. Figure 2 As shown in a, Figure 2 a is a circular Airy beam on the rear focal plane of the convex lens. The first circular Airy beam and the second circular Airy beam are arranged opposite to each other in the vacuum chamber and form a light trap capture area. The focal points formed by the self-focusing of the two coincide with each other, as shown in Figure 2 As shown in b, Figure 2 b is the focal spot of the self-focusing position, Figure 2c is the light intensity distribution along the cross section of the optical axis during the propagation of the circular Airy beam. The micro-nanoparticle 14 is captured in the light trap capture area and stably suspended in a high vacuum environment. The detection component is set on the side of the vacuum chamber 19 to detect the movement of the micro-nanoparticle 14. After the two circular Airy beams are aligned, the two beams propagate in opposite directions on the same straight line, and the focal points generated by their self-focusing coincide. This method can offset the axial scattering forces of the two circular Airy beams on the micro-nanoparticle 14, thereby achieving stable capture in the axial direction.

[0030] The modulated beam generating assembly includes a first laser 1, a half-wave plate 2, a polarization beam splitter 3, and a spatial light modulator 4. The captured laser beam emitted from the first laser 1 is sequentially transmitted along the optical axis through the half-wave plate 2, transmitted through the polarization beam splitter 3, and reflected and modulated by the spatial light modulator 4 to generate a modulated beam. The spatial light modulator 4 applies the phase hologram information of the circular Airy beam, so that the modulated beam carries the phase hologram information of the circular Airy beam. The half-wave plate 2 and the beam splitter 3 are configured to convert the captured laser beam into linearly polarized light that conforms to the modulation direction of the spatial light modulator 4. Specifically, the orientation of the half-wave plate 2 is adjusted to change the linear polarization direction of the emitted laser beam. After being reflected and modulated by the spatial light modulator 4, the modulated beam carries the phase hologram information of the circular Airy beam.

[0031] The 4F system comprises a first convex lens 5, a pinhole diaphragm 6, and a second convex lens 7. The modulated light beam emitted from the spatial light modulator 4 of the modulated beam generating assembly passes through the first convex lens 5, the pinhole diaphragm 6, and the second convex lens 7 along the optical axis before being incident on the beam splitter 8. The distances between the first convex lens 5 and the spatial light modulator 4 of the modulated beam generating assembly, the distance between the first convex lens 5 and the pinhole diaphragm 6, and the distance between the pinhole diaphragm 6 and the second convex lens 7 are all focal lengths F. The function of the pinhole diaphragm 6 is to filter out stray light generated by the modulation of the spatial light modulator 4. In actual optical paths, the focal lengths of the first convex lens 5 and the second convex lens 7 are typically tens of centimeters to several meters. The spatial light modulator 4 is a reflective pure phase liquid crystal spatial light modulator, which modulates the light beam in the form of a complex amplitude-encoded pure phase hologram. The special beam is then Fourier transformed by the third convex lens 12 and the fourth convex lens 13 to produce the special beam.

[0032] The distance traveled by the light beam converged by the second convex lens 7 and finally reaching the front focal plane of the third convex lens 12 after passing through the beam splitter 8 and the first reflector 9 in sequence is equal to the focal length F; the distance traveled by the light beam converged by the second convex lens 7 and finally reaching the front focal plane of the fourth convex lens 13 after passing through the beam splitter 8, the second reflector 11 and the third reflector 10 is also equal to the focal length F.

[0033] The detection assembly includes a second laser 15, a fifth convex lens 16, a sixth convex lens 17, and a four-quadrant detector 18. The detection laser beam emitted from the second laser 15 passes through the fifth convex lens 16 and the anti-reflection coating on the optical window before irradiating the trapped micro-nanoparticle 14 in the vacuum chamber 19. The light beam scattered by the trapped micro-nanoparticle 14 is collected by the sixth convex lens 17, passes through the anti-reflection coating on the optical window, and is incident on the center of the four-quadrant detector 18. The four-quadrant detector 18 can detect the disturbance caused by the movement of the micro-nanoparticle 14, thereby calculating the displacement information of the micro-nanoparticle 14.

[0034] The shapes of the micro-nanoparticles 14 include sphere, ellipsoid, rod and dumbbell.

[0035] The three-dimensional size of the micro-nanoparticles 14 ranges from a few nanometers to hundreds of micrometers.

[0036] Finally, in the equivalent optical path, the front focal planes of the third convex lens 12 and the fourth convex lens 13 are roughly coincident with the rear focal plane of the second convex lens 7 to achieve the effect of relaying the light field; the capture position of the micro-nano particles is determined to be the geometric center of the vacuum chamber, and a particle support device is installed near it; the relative positions of the third convex lens 12 and the fourth convex lens 13 are adjusted so that their optical axes coincide, and the distance between their rear focal planes and the particle capture position is equal to the focal length of the circular Airy beam self-focusing; the position of the fifth convex lens 16 is adjusted so that the detection laser beam is focused on the particle capture position; the positions of the sixth convex lens 17 and the four-quadrant detector 18 are adjusted so that the detection laser beam can be aligned with the center of its optical axis.

[0037] The specific implementation process of the present invention is as follows:

[0038] 1) applying a phase hologram of a circular Airy beam to the spatial light modulator 4, turning on the first laser 1, and capturing the beam to form an opposing dual-beam light trap capture area in the vacuum cavity;

[0039] 2) Activate the support device to release a micro-nano particle 14 and make it fall into the optical trap formed by the two opposing light beams. The micro-nano particle 14 is subjected to the optical force of the light beams and is stably captured.

[0040] 3) Turning on the vacuum pump system of the vacuum chamber 19 to ensure that the vacuum level in the vacuum chamber reaches the desired value. During this process, the micro-nanoparticles 14 are still in a stable captured state.

[0041] 4) Turn on the second laser 15 so that the detection laser beam is irradiated on the captured micro-nanoparticle 14, and fine-tune the position of the sixth convex lens 17 to collect as much scattered detection laser beam as possible;

[0042] 5) The scattered detection laser beam is collected by the sixth convex lens 17 and incident on the position of the four-quadrant detector 18, thereby detecting the displacement signal of the micro-nano particle 14;

[0043] 6) Based on the displacement signal of the micro-nanoparticle 14, the stiffness of the optical trap in different axial directions is calculated to evaluate the stability of the capture;

[0044] 7) Gradually increase the vacuum degree of the vacuum chamber 19 and continuously repeat the above steps 1) to 6) to obtain the capture stability under different vacuum degrees.

[0045] This embodiment realizes the three-dimensional capture of micro-nanoparticles in a vacuum using a circular Airy beam. It has a greater optical trap stiffness under the same capture light power, improves the stability of capturing micro-nanoparticles in a high vacuum environment, and can achieve the capture of micro-nanoparticles with larger mass, which is conducive to further improving the vacuum degree and measurement accuracy of the vacuum optical tweezers system.

[0046] Example 2

[0047] The same as Example 1, except that the spatial light modulator 4 is applied with phase holograms of other special light beams, including other Airy beams, vortex beams, Bessel beams, radially polarized beams, angularly polarized beams and their derived special light field distribution beams; by simply adjusting the parameters and relative positions of the third convex lens 12 and the fourth convex lens 13, these special light beams can also form a dual-beam opposing light trap capture area in the vacuum cavity, thereby capturing micro-nanoparticles.

[0048] In addition, it should be noted that the specific embodiments described in this specification may be named differently, and the above content described in this specification is merely an example of the structure of the present invention. Any equivalent changes or simple changes made based on the structure, features and principles of the present invention are included in the protection scope of the present invention. Those skilled in the art of the present invention may make various modifications or supplements to the specific examples described or adopt similar methods, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A holographic vacuum optical tweezers device based on a circular Airy beam, characterized in that: The invention comprises a vacuum cavity (19), a modulated light beam generating component, a 4F system, a spectroscope (8), a first reflector (9), a second reflector (11), a third reflector (10), a third convex lens (12), a fourth convex lens (13) and a detection component; the micro-nano particles (14), the third convex lens (12) and the fourth convex lens (13) are all placed in the vacuum cavity (19); the modulated light beam emitted by the modulated light beam generating component is incident on the spectroscope (8) after passing through the 4F system; the modulated light beam carries the phase hologram information of the circular Airy beam; the transmitted light beam through the spectroscope (8) is reflected by the first reflector (9) and then incident on the vacuum cavity (19); and then passes through the vacuum cavity (19) to generate a light beam. The third convex lens (12) in the cavity (19) converges to form a first circular Airy beam; the reflected light beam from the spectroscope (8) is then reflected by the second reflector (11) and the third reflector (10) in sequence and then enters the vacuum cavity (19), and then converges through the fourth convex lens (13) in the vacuum cavity (19) to form a second circular Airy beam. The first circular Airy beam and the second circular Airy beam are arranged in opposition to each other in the vacuum cavity and form a light trap capture area. The micro-nano particle (14) is captured in the light trap capture area and is stably suspended in a high vacuum environment. The detection component is arranged on the side of the vacuum cavity (19) for detecting the movement of the micro-nano particle (14).

2. A holographic vacuum optical tweezers device based on a circular Airy beam according to claim 1, characterized in that: The modulated light beam generating component comprises a first laser (1), a half-wave plate (2), a polarization beam splitter (3) and a spatial light modulator (4); a captured laser beam emitted from the first laser (1) is sequentially transmitted along an optical axis through the half-wave plate (2), transmitted through the polarization beam splitter (3) and reflected and modulated by the spatial light modulator (4) to generate a modulated light beam.

3. The holographic vacuum optical tweezers device based on a circular Airy beam according to claim 1, characterized in that: The 4F system comprises a first convex lens (5), an aperture (6) and a second convex lens (7); the modulated light beam of the modulated light beam generating component passes through the first convex lens (5), the aperture (6) and the second convex lens (7) in sequence along the optical axis and is incident on the beam splitter (8); the distance between the first convex lens (5) and the modulated light beam generating component, the distance between the first convex lens (5) and the aperture (6), and the distance between the aperture (6) and the second convex lens (7) are all focal lengths F; The distance traveled by the light beam converged by the second convex lens (7) and finally reaching the front focal plane of the third convex lens (12) after passing through the beam splitter (8) and the first reflector (9) in sequence is equal to the focal length F; The distance traveled by the light beam converged by the second convex lens (7) and finally reaching the front focal plane of the fourth convex lens (13) after passing through the beam splitter (8), the second reflector (11) and the third reflector (10) is also equal to the focal length F.

4. The holographic vacuum optical tweezers device based on a circular Airy beam according to claim 1, characterized in that: The detection assembly comprises a second laser (15), a fifth convex lens (16), a sixth convex lens (17) and a four-quadrant detector (18); the detection laser beam emitted from the second laser (15) is irradiated onto the captured micro-nano particles (14) in the vacuum chamber (19) after passing through the fifth convex lens (16); the light beam scattered by the captured micro-nano particles (14) is collected by the sixth convex lens (17) and then incident on the center of the four-quadrant detector (18).

5. The holographic vacuum optical tweezers device based on a circular Airy beam according to claim 1, characterized in that: An optical window for light beam transmission is provided on the wall of the vacuum cavity (19), and an anti-reflection film is plated in the optical window.

6. The holographic vacuum optical tweezers device based on a circular Airy beam according to claim 1, characterized in that: The shapes of the micro-nano particles (14) include sphere, ellipsoid, rod and dumbbell.

7. The holographic vacuum optical tweezers device based on a circular Airy beam according to claim 1, characterized in that: The size of the micro-nanoparticles (14) in three dimensions of space is between several nanometers and hundreds of micrometers.

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