Petal-shaped homogeneous phase nonlinear rotating beam generation method based on phase regulation and control

Abstract

The invention provides a petal-shaped homogeneous phase nonlinear rotating beam generation method based on phase regulation and control. By designing a phase distribution function with spiral symmetry and combining dynamic regulation and control of morphological parameters and transmission distance, petal-shaped light beams with different petal numbers, rotation angles and energy distribution can be generated. The light beam shows a homogeneous phase characteristic, high directivity and a stable vortex structure in propagation, is especially suitable for the field of optical tweezers, forms a high-intensity focusing area by adjusting spiral symmetrical phase distribution, and can stably capture micron-sized particles.

Description

Technical Field

[0001] The present invention relates to the field of optical phase modulation, and specifically to a method for generating a petal-shaped homogeneous-phase nonlinear rotating beam and its innovative research on propagation characteristics, energy distribution, and vortex stability. Background Art

[0002] The phase and intensity distribution characteristics of light beams have important application values in the fields of optical manipulation, communication, imaging, etc. Traditional light beam generation technologies (such as Gaussian beams, Laguerre-Gaussian beams) can achieve basic vortex structures through simple optical elements (such as spiral phase plates, cylindrical lenses), but their shapes and phase characteristics are limited by geometric optical designs and it is difficult to flexibly control complex light fields. In recent years, the dynamic phase modulation technology based on spatial light modulators has gradually become the mainstream means for generating complex light beams. For example, by loading a spiral phase distribution, a vortex beam carrying orbital angular momentum can be generated, and its topological charge l determines the annular structure and rotation characteristics of the light beam. However, there are still some problems in the existing technologies: First, although the annular intensity distribution of traditional vortex beams has rotational symmetry, its energy is dispersed in the annular region, resulting in low energy utilization rate. In applications that require high energy density (such as optical tweezer particle trapping), it is difficult to achieve efficient manipulation with such light beams; Second, existing methods mostly rely on single topological charge l regulation, and the generated light beams can only achieve fixed petal numbers or simple rotation modes, lacking the ability to dynamically control complex symmetries (such as multi-petal petal-shaped structures); Third, the phase distributions of complex light fields generated by most phase modulation methods are prone to distortion during propagation and it is difficult to maintain homogeneous-phase characteristics, which limits their applications in long-distance transmission or precision interferometric measurements. In addition, traditional optical trapping technologies mainly rely on Gaussian beams or simple vortex beams, and their trapping capabilities are limited by the energy distribution and phase stability of the light beams. For the trapping and manipulation of micron-sized particles, it is difficult to synergistically optimize the phase stability and energy distribution of light beams in the existing technologies, and there are still significant challenges in achieving stable and high-precision optical potential wells in complex light fields.

[0003] The present invention proposes a method for generating a petal-shaped rotating beam based on a homogeneous-phase distribution function. By introducing a dynamic coupling model of morphological parameters θ and propagation distance z , the problems in traditional technologies that are difficult to balance symmetry, energy utilization rate, and phase stability are solved, providing a high-precision light field tool for applications such as optical manipulation and encrypted communication. Summary of the Invention

[0004] To solve the above-mentioned defects in the existing technologies, the present invention proposes a method for generating a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation and its characteristic analysis. By designing a phase distribution function with strict mathematical symmetry and combining morphological parametersθ Dynamic coupling regulation with the transmission distance z Realize the controllable generation of the number of lobes, rotation direction and energy distribution of the light beam.

[0005] The above object is achieved by the following technical solutions: Step 1: According to the light field equation of the target petal-shaped homogeneous phase non-linear rotating light beam, design the corresponding phase distribution map, and load the designed phase distribution map onto the spatial light modulator; Step 2: Use a continuous solid-state laser as the excitation light source, filter out the inhomogeneous components in the laser beam through a spatial filter, expand and collimate it through a lens, filter the Gaussian beam through a polarizer, generate the target structured light field under the action of the spatial light modulator, adjust the beam diameter through a convex lens group, and then incident it into the digital acquisition camera for imaging, and observe the number of petals, rotation direction and light intensity distribution of the light beam; Further, in Step 1, the light field equation is: E(r,\varnothing,z)={J}_{l}(r{k}_{r1})[cos(θ / 2)exp(il(\varnothing +mod({x}^{5}+{y}^{5},2n)))+sin(θ / 2)exp(-il(\varnothing +mod({x}^{5}+{y}^{5},2n)))]exp(i{k}_{z1}z)+{J}_{l}(r{k}_{r2})[sin(θ / 2)exp(il(\varnothing +mod({x}^{5}+{y}^{5},2n)))+cos(θ / 2)exp(-il(\varnothing +mod({x}^{5}+{y}^{5},2n)))]exp(i{k}_{z2}z). Where: and are the amplitude coefficients of the light beam; is the azimuth angle; l is the topological charge number; and are the phase velocities; is the homogeneous phase. Due to the character set limitation of the formula editor of the patent client, the symbol n is used to replace the pi in the formula. The two have exactly the same mathematical meaning. This is hereby declared; z is the transmission distance; θ is the morphological parameter, which determines the morphology of the optical vortex on the beam axis.

[0006] Further, in Step 1, the spatial light modulator is a transmissive liquid crystal spatial light modulator.

[0007] Further, in Step 2, the digital acquisition camera is a CCD camera or a CMOS camera.

[0008] Further, in Step 2, the number of petals of the light beam is twice the topological charge l .

[0009] Further, in Step 2, the rotation direction of the light beam exhibits a dynamic switching characteristic with the value range of the morphological parameter θ and the propagation distance z changing: When θ ∈[0, π / 2): During the propagation of the light beam ( z from 0 to the maximum value), its rotation direction is clockwise; When θ ∈(π / 2, π]: During the propagation of the light beam ( z from 0 to the maximum value), its rotation direction is counterclockwise; When θ ∈[π, 3π / 2): During the propagation of the light beam ( z from 0 to the maximum value), its rotation direction is counterclockwise; When θ ∈(3π / 2, 2π]: During the propagation of the light beam ( z from 0 to the maximum value), its rotation direction is clockwise; Further, in Step 2, the main lobe light intensity distribution of the light beam changes dynamically with the propagation distance z : When the morphological parameter θ ∈(0,π), the main lobe light intensity gradually decreases with the increase of the distance z ; when the morphological parameter θ ∈(π,2π), the main lobe light intensity gradually decreases with the increase of the distance z .

[0010] Compared with the prior art, the beneficial effects of the present invention include: (1) First, by introducing a homogeneous phase term with fifth-order symmetry , the light beam exhibits significant phase stability during propagation. Experiments show that after propagating 1.6 m in free space, the light front distribution can still maintain a clear petal-like structure, solving the problem of unstable propagation of traditional vortex beams caused by phase distortion.

[0011] (2) Second, through the continuous dynamic regulation (in the range of 0-2π) of the morphological parameter θ and the synergistic effect of the propagation distance z , the present invention realizes the dynamic switching characteristic of the rotation direction of the light beam. Whenθ When varying in different intervals, during the propagation process of the light beam ( z from 0 to the maximum value), the rotation direction shows regular reversals (such as clockwise rotation from 0° to 90°, counterclockwise rotation from 90° to 180°, counterclockwise rotation from 180° to 270°, and clockwise rotation from 270° to 360°). This dynamic regulation ability provides a new technical means for particle manipulation.

[0012] (3) In terms of energy distribution, through the optimization of the homogeneous phase design, the present invention significantly improves the energy concentration.

[0013] (4) The petal-shaped light beam of the present invention exhibits unique advantages in optical trapping: by regulating the topological charge number l and the morphological parameters θ , multiple optical potential wells with high energy density can be formed to achieve effective trapping of microparticles. Preliminary experiments show that when l = 3 and θ = π / 6, using orange fluorescent polystyrene microspheres (diameter 2 μm), it can be observed that the microparticles are stably trapped in the high-intensity region of the light beam, verifying the application potential of this light beam in optical manipulation. Description of the Drawings

[0014] Figure 1 is a schematic structural diagram of the experimental system device of a method for generating a petal-shaped homogeneous phase nonlinear rotating light beam based on phase modulation provided by the present invention.

[0015] Among them, 1 is a continuous laser, 2 is an attenuation sheet, 3 is a spatial filter, 4 is a first convex lens, 5 is an aperture stop, 6 is a first polarizer, 7 is a spatial light modulator, 8 is a second polarizer, 9 is a second convex lens, 10 is a third convex lens, and 11 is a CMOS camera.

[0016] Figure 2 is the phase distribution diagram of a petal-shaped homogeneous phase nonlinear rotating light beam based on phase modulation according to the present invention (taking the topological charge number l = 3 as an example, the morphological parameter θ = π / 6, and the propagation distance z = 0.16 m).

[0017] Figure 3 is the light intensity distribution diagram of a petal-shaped homogeneous phase nonlinear rotating light beam based on phase modulation according to the present invention (taking the topological charge number l = 3 as an example, the morphological parameter θ = π / 6, and the propagation distance z = 0.16 m).

[0018] Figure 4It is the intensity variation diagram of a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation obtained by using the method of the present invention with respect to the morphological parameter θ and the propagation distance z (taking the morphological parameter θ ∈ [0, π / 2] as an example).

[0019] Figure 5 It is the intensity distribution diagram of the light field of a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation obtained by using the method of the present invention after gray-scale image processing (taking the topological charge number l = 3, the morphological parameter θ = π / 6, and the propagation distance z = 0.16 m as an example).

[0020] Figure 6 It is the experimental result diagram of a petal-shaped beam (topological charge number l = 3, morphological parameter θ = π / 6) generated by using the method of the present invention capturing orange fluorescent polystyrene microspheres (diameter 2 μm), showing that the microparticles are stably captured in the high-intensity region of the beam. Specific embodiments

[0021] The technical solution of the present invention is elaborated in detail through specific implementation cases below for easy understanding of its implementation manner. It should be noted that the protection scope of the present invention is not limited to the specific forms of the cases. Any adjustment, equivalent change or optimization scheme based on the core idea and technical framework of the present invention is regarded as falling within the protection scope defined by the claims of this patent.

[0022] As Figure 1 shown, a method for generating a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation, the experimental system used specifically includes: Laser - 1, attenuation sheet - 2, spatial filter - 3, first convex lens - 4, aperture stop - 5, first polarizer - 6, spatial light modulator - 7, second polarizer - 8, second convex lens - 9, third convex lens - 10, CMOS camera - 11, where: the continuous solid-state laser - 1 emits a laser light source, the attenuation sheet - 2 is used to adjust the intensity of the incident laser, after being expanded by the spatial filter - 3 and collimated by the first convex lens - 4, the aperture stop - 5 eliminates stray light, the first polarizer - 6 is a polarizer, the spatial light modulator - 7 is used to generate the target structured light field, the second polarizer - 8 is an analyzer, the focal lengths of the second convex lens - 9 and the third convex lens - 10 are 15 cm and 5 cm respectively, used for beam shrinking, and the CMOS camera - 11 is used to observe the beam image.

[0023] The laser used in this embodiment is a single transverse mode (TEM00) continuous solid-state laser, with an excitation wavelength of 532 nm, an output power of 100 mW, and a beam waist diameter of 1.2 mm.

[0024] The spatial light modulator used in this embodiment is a transmissive liquid crystal spatial light modulator.

[0025] A method for generating a petal-shaped homogeneous phase nonlinear rotating beam based on phase modulation, the specific steps are as follows: Step 1: According to the optical field equation of the target petal-shaped homogeneous phase nonlinear rotating beam, design the corresponding phase distribution map, and load the designed phase distribution map onto the spatial light modulator; Step 2: Use a single transverse mode (TEM00) continuous solid-state laser as the excitation light source, filter out the inhomogeneous components in the laser beam through a spatial filter, and after beam expansion and collimation by a lens, filter the Gaussian beam through a polarizer, generate the target structured light field under the action of the spatial light modulator, adjust the beam diameter through a convex lens group, and then incident on a digital acquisition camera for imaging to observe the light field distribution carrying phase information; Step 3: Based on the dynamic regulation of θ the morphological parameters z and the propagation distance

[0026] To verify the effect of the beam of the present invention in optical trapping, on the basis of the original experimental system, an inverted microscope system (high numerical aperture objective lens NA = 0.55) and a fluorescence imaging module are added to construct an optical trapping observation platform. Use orange fluorescent polystyrene microspheres with a diameter of 2 μm dispersed in deionized water as tracer particles to observe the particle trapping phenomenon.

Claims

1. A method for generating a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation, characterized in that Including the following steps: Step 1: According to the optical field equation of the target petal-shaped homogeneous phase non-linear rotating beam, design the corresponding phase distribution diagram, and load the designed phase distribution diagram onto the spatial light modulator; Step 2: Use a continuous solid-state laser as the excitation light source. Filter out the inhomogeneous components in the laser beam through a spatial filter, expand and collimate the laser beam through a lens, filter the Gaussian beam through a polarizer, generate the target structured light field under the action of the spatial light modulator, adjust the beam diameter through a convex lens group, and then incident it into the digital acquisition camera for imaging to observe the light field distribution carrying phase information; Step 3: Based on the morphological parameters θ and the transmission distance z for dynamic regulation, analyze the rotation direction of the light beam and the characteristics of the light intensity distribution.

2. A method for generating a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation according to claim 1, characterized in that The optical field equation is:

3. Wherein: and are the amplitude coefficients of the light beam; is the azimuth angle; l is the topological charge number; and are the phase velocities; is the homogeneous phase. In the formula, the symbol n is used to replace the pi (π). The two have exactly the same mathematical meaning. This is hereby declared; z is the transmission distance; θ is the morphological parameter, which determines the morphology of the optical vortex on the beam axis.

4. A method for generating a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation according to claim 1, characterized in that The spatial light modulator is a transmissive liquid crystal spatial light modulator.

5. A method for generating a petal-shaped homogeneous-phase nonlinear rotating beam based on phase modulation according to claim 1, characterized in that The digital acquisition camera is a CCD camera or a CMOS camera.

6. The method according to claim 1, characterized in that, The rotation direction of the light beam presents periodic switching with the change of the morphological parameter θ : When θ ∈[0, π / 2), the light beam rotates clockwise; When θ ∈(π / 2, π], the light beam rotates counterclockwise; When θ ∈[π, 3π / 2), the light beam rotates counterclockwise; When θ ∈(3π / 2, 2π], the light beam rotates clockwise.

7. The method according to claim 1, wherein The main lobe light intensity distribution of the said light beam changes dynamically with the propagation distance z as follows: when the shape parameter θ ∈(0,π), the main lobe light intensity gradually decreases with the increase of the distance z ; when the shape parameter θ ∈(π,2π), the main lobe light intensity gradually decreases with the increase of the distance z .

8. The method according to claim 1, wherein The petal-shaped homogeneous phase non-linear rotating beam can achieve optical trapping of microparticles.

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