Multi-Airy beam generation method based on adjustable distribution

Abstract

The invention provides a multi-Airy beam generation method based on adjustable distribution. The multi-Airy beam generation method comprises the following steps: constructing basic phase distribution of a single Airy beam; designing phase shift modulation factors corresponding to the plurality of sub-beams, wherein the phase shift modulation factors are set based on the displacement characteristics of Fourier transform; superposing the phase shift modulation factor with the frequency spectrum of the single beam of Airy light to obtain composite phase distribution; and generating a multi-Airy beam array with adjustable and controllable distribution based on the composite phase distribution. The method provided by the invention can flexibly adapt to specific requirements of different scenes on beam distribution, and the application adaptability and practicability of the multi-Airy beam array in the fields of laser confrontation, laser processing, optical communication and the like are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to the technical field of light beam array generation, and in particular to a method for generating multiple Airy beams based on controllable distribution. BACKGROUND

[0002] Airy beams have broad application prospects in many fields due to their unique characteristics such as non-diffraction, self-acceleration, and self-healing. For example, in laser countermeasures, Airy beams can be used to reduce the divergence of beam transmission, and in optical tweezer technology, Airy beams can be used to accurately manipulate microparticles.

[0003] Currently, traditional methods for generating an equal-intensity spot array, such as methods based on Dammann gratings or composite phase plates, can only form regular arrays with fixed intervals between sub-beams. Existing methods for generating multiple beams have deficiencies in controllability of distribution and cannot well adapt to the needs of specific beam distribution in fields such as laser countermeasures, laser processing, and optical communication, and cannot meet the requirements of application scenarios with high flexibility in beam distribution. SUMMARY

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a method for generating multiple Airy beams based on controllable distribution to solve the above-mentioned problems.

[0005] The present application provides a method for generating multiple Airy beams based on controllable distribution, comprising: constructing a basic phase distribution of a single-beam Airy beam; designing a phase shift modulation factor corresponding to multiple sub-beams, the phase shift modulation factor being set based on the displacement property of Fourier transform; superimposing the phase shift modulation factor and the spectrum of the single-beam Airy light to obtain a composite phase distribution; generating a multiple Airy beam array with controllable distribution based on the composite phase distribution.

[0006] According to the technical scheme provided by the embodiments of the present application, the construction of the basic phase distribution of the single-beam Airy beam comprises: determining a frequency domain variable and an attenuation factor, and constructing an Airy beam phase plate function based on the frequency domain variable and the attenuation factor; generating a single-beam Airy beam by loading the phase plate function through a spatial light modulator.

[0007] According to the technical scheme provided by the embodiments of the present application, the Airy beam phase plate function contains a frequency domain x-axis coordinate and a frequency domain y-axis coordinate.

[0008] According to the technical scheme provided by the embodiments of the present application, the phase shift modulation factor includes a phase term in linear relationship with the frequency domain variable, so as to modulate the spatial distribution of the sub-beam by using the displacement property of Fourier transform.

[0009] According to the technical scheme provided in the embodiment of the present application, for the first The expression of the phase shift modulation factor is:

[0010] wherein, and represents a frequency domain displacement parameter of the first sub-beam, and represents a frequency domain variable.

[0011] According to the technical scheme provided in the embodiment of the present application, the step of superimposing the phase shift modulation factor and the frequency spectrum of the single beam Airy light comprises: multiplying the phase shift modulation factor of the first sub-beam and the frequency spectrum of the single beam Airy light to obtain a frequency spectrum with phase shift of the first sub-beam; accumulating the frequency spectrums with phase shift to obtain a complex phase distribution.

[0012] According to the technical scheme provided in the embodiment of the present application, the step of generating the multi-Airy light beam array based on the complex phase distribution comprises: loading the complex phase distribution onto a spatial light modulator so that a laser beam is incident to the spatial light modulator for phase modulation; modulating the light beam to perform inverse Fourier transform through a Fourier lens to form a multi-Airy light beam array.

[0013] According to the technical scheme provided in the embodiment of the present application, the laser beam is expanded, collimated and polarized before being incident, and the polarization processing is used to make the laser meet the liquid crystal molecule modulation requirement of the spatial light modulator.

[0014] According to the technical scheme provided in the embodiment of the present application, a CCD camera is placed at the back focal plane of the Fourier lens to receive and record the light field distribution image of the sub-beam.

[0015] According to the technical scheme provided in the embodiment of the present application, the spatial light modulator is a reflective phase type liquid crystal spatial light modulator.

[0016] Compared with the prior art, the application has the beneficial effects that: by constructing the basic phase distribution of a single beam Airy beam, a stable original light field basis is provided for multi-beam generation; based on the displacement characteristics of Fourier transform, a phase shift modulation factor is designed, which breaks through the bottleneck that the position adjustment of sub-beams is limited in the traditional multi-beam generation method, and makes the distribution regulation of sub-beams have theoretical support and accuracy; by superimposing the phase shift modulation factor and the spectrum of the single beam Airy light to form a composite phase distribution, the generation process of the multi-beam array is simplified without relying on complex optical element combination; finally, based on the composite phase distribution, a multi-Airy beam array with adjustable distribution can be generated, which gets rid of the limitations of regular array and fixed sub-beam interval in the traditional method, can flexibly adapt to the specific needs of beam distribution in different scenes, and significantly improves the application adaptability and practicability of the multi-Airy beam array in the fields of laser countermeasure, laser processing, optical communication and the like. BRIEF DESCRIPTION OF DRAWINGS

[0017] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the drawings: Figure 1 A step flow chart of the multi-Airy beam generation method based on adjustable distribution provided by the application is provided. Figure 2 A schematic diagram of an Airy beam phase plate is provided. Figure 3 A schematic diagram of a composite phase plate is provided. Figure 4 A structural schematic diagram of an optical system for beam modulation experiment is provided. Figure 5 An experimental result diagram of Airy beam splitting is provided. Figure 6 A spot flip diagram of the experimental result of Airy beam splitting is provided. Figure 7 A result diagram of the diffraction grating splitting experiment is provided.

[0018] Reference signs: 10, CCD camera; 20, spatial light modulator; 30, beam splitter; 40, baffle; 50, polarizer; 60, beam expander system; 70, laser; 80, Fourier lens. DETAILED DESCRIPTION

[0019] The application will be further described in detail below in combination with the drawings and examples. It can be understood that the specific examples described herein are only used to explain the related application, and not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings.

[0020] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other in the case of no conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0021] Please refer to Figure 1 The present application provides a multi-Airy beam generation method based on a controllable distribution, comprising: S100: constructing a basic phase distribution of a single-Airy beam.

[0022] Specifically, in step S100, for the step of constructing a basic phase distribution of a single-Airy beam, the basic phase feature of the Airy beam needs to be determined based on its inherent characteristics. The basic phase distribution needs to accurately reflect the wavefront structure of the single-Airy beam, providing a unified original phase template for the subsequent generation of multiple beams.

[0023] Further, step S100 specifically comprises: S110: determining a frequency domain variable and an attenuation factor, and constructing an Airy beam phase plate function based on the frequency domain variable and the attenuation factor.

[0024] Specifically, in step S110, the key parameters required for a single-Airy beam are first constructed, including a frequency domain variable and an attenuation factor. The frequency domain variable is used to describe the coordinate information of the Airy beam in the frequency space, and is a basic variable for constructing the phase distribution; the attenuation factor is set to adapt to the actual application scenario, and is used to reasonably constrain the energy of the ideal Airy beam. Then, based on the above-determined frequency domain variable and attenuation factor, an Airy beam phase plate function is constructed. The function is a mathematical expression of the phase feature of the single-Airy beam, and its form needs to accurately reflect the wavefront structure of the Airy beam, and the influence of the frequency domain variable and the attenuation factor is integrated into it to form a phase plate that can be used for optical modulation, as shown in Figure 2 .

[0025] Further, the Airy beam phase plate function contains a frequency domain x-axis coordinate and a frequency domain y-axis coordinate.

[0026] Specifically, the frequency domain variable mainly includes a frequency domain x-axis coordinate and a frequency domain y-axis coordinate, which are used to locate the phase feature of the Airy beam in a two-dimensional frequency domain space. Through these two coordinate variables, the phase plate function can completely map the wavefront change of the Airy beam in the frequency domain, ensuring that the subsequent generated light field conforms to the inherent characteristics of the Airy beam in terms of spatial distribution.

[0027] The phase plate function of the single-Airy beam is as follows: Formula (I); wherein, and represent the coordinates of the frequency domain x-axis and y-axis, denotes an attenuation factor.

[0028] S120: loading the phase plate function to generate a single beam of Airy beam by spatial light modulator 20.

[0029] Specifically, in step S120, based on the parameters and expressions of S110, the phase plate is loaded into the optical system by spatial light modulator 20, and a single beam of Airy beam is generated by laser light source irradiation and phase modulation.

[0030] S200: design the phase shift modulation factor corresponding to the multi-beam sub-beam, which is set based on the displacement characteristics of Fourier transform.

[0031] Specifically, in step S200, the phase shift modulation factor corresponding to the multi-beam sub-beam is based on the displacement characteristics of Fourier transform. By introducing a specific phase modulation in the frequency domain, the expected position movement of the light beam in the spatial domain can be achieved. Based on this, the phase shift modulation factor is designed for each sub-beam to be generated, and each modulation factor corresponds to the target distribution position of the sub-beam. Through the preset phase change rule, the spatial position of the sub-beam is controlled.

[0032] Further, the phase shift modulation factor includes a phase term in linear relationship with the frequency domain variable, so as to modulate the spatial distribution of the sub-beam by the displacement characteristics of Fourier transform.

[0033] Specifically, the design basis of the phase shift modulation factor is: If the Fourier transform of the light field is , then the Fourier transform of the light field after applying the phase shift corresponds to the displacement of the spatial light field, where is the displacement parameter.

[0034] Specifically, if the Fourier transform of a certain light field is a basic frequency domain distribution, then when a certain displacement is needed in the spatial domain, a phase shift related to a unique parameter needs to be applied to its Fourier transform in the frequency domain. The displacement parameter determines the size and direction of the phase shift, and by adjusting the displacement parameter, the displacement distance and direction of the spatial light field can be accurately controlled.

[0035] Based on the displacement characteristics of Fourier transform, i.e. changing the phase shift factor can cause the displacement of the light beam distribution in the spatial field, the expression of the light field can be obtained.

[0036] Specifically, first, the basic form of the displacement light field is given as follows: Formula (II); Here, introduce and As a frequency shift factor, its function is to change the deflection of the light beam in the spatial field, and the intensity of the light field can be observed by taking the real part.

[0037] For frequency domain signals The applied phase shift is , During operation, the phase-shifted frequency domain signal From the formula (III) Determining: Formula (3) in, As a phase shift factor, its phase change directly affects The frequency components. Based on Fourier optics theory, the data expression can be derived: Formula (IV); Furthermore, for the first For each sub-beam, the expression for the phase shift modulation factor is as follows: Formula (V): Formula (5); in, and Indicates the first Frequency domain shift parameters of individual beams and This represents a frequency domain variable.

[0038] S300: The phase shift modulation factor is superimposed with the spectrum of a single beam of Airy light to obtain a composite phase distribution.

[0039] Specifically, in step S300, when superimposing the phase-shift modulation factor with the spectrum of a single Airy beam to obtain a composite phase distribution, the phase-shift modulation factor corresponding to each sub-beam needs to be fused with the spectrum of the single Airy beam separately, so that the basic spectral information of the single Airy beam is combined with the phase modulation information of each sub-beam. The superposition process must ensure that the phase information of each sub-beam does not interfere with each other and is completely preserved in the composite distribution. The final composite phase distribution must contain the phase characteristics of all sub-beams, providing a complete phase modulation basis for the subsequent generation of a multi-beam array.

[0040] Further, the superposition of the phase shift modulation factor with the spectrum of a single beam of Airy light includes: The first Multiplying the phase shift modulation factor of each sub-beam by the spectrum of a single Airy beam yields the first... The phase-shifted spectrum of individual beams; Will The composite phase distribution is obtained by accumulating the phase-shifted spectra of each band.

[0041] Specifically, after obtaining the phase shift modulation factor, the phase shift factor is combined with the Airy beam spectrum to obtain the expression for the composite beam with the phase shift factor. The phase-shift spectrum of the individual beams is shown in Formula (VI): Formula (VI); get After the phase shift spectrum of each sub-beam, The phase shift spectra of the individual beams are superimposed to obtain a composite spectrum, i.e., a composite phase plate, such as... Figure 3 As shown; the composite spectrum is shown in formula (VII): Formula (VII).

[0042] S400: Generate a tunable distribution of multi-Airy beam array based on the composite phase distribution.

[0043] Specifically, in step S400, when generating a tunable multi-Airy beam array based on the composite phase distribution, the composite phase distribution needs to be converted into an actual light field distribution through a beam modulation experimental optical system.

[0044] like Figure 4 As shown, the optical system for beam modulation experiments provided in this embodiment includes: a CCD camera 10, a spatial light modulator 20, a beam splitter 30, a baffle 40, a polarizer 50, a beam expander 60, a laser 70, and a Fourier lens 80. The laser 70 emits a laser of a set wavelength to the spatial light modulator 20; in this embodiment, a 532nm laser source is used. The spatial light modulator 20 is a reflective phase-type liquid crystal spatial light modulator, loaded with a special binary phase plate combining cubic and translational phases. This phase plate is designed based on the traditional Airy beam phase plate formula and displacement function, enabling modulation of the laser phase to generate multiple arbitrarily distributed Airy beams. The beam expander 60, polarizer 50, and beam splitter 30 are positioned on the laser path between the laser 70 and the spatial light modulator 20, and arranged sequentially along the laser transmission direction. The function of the beam expander 60 is to enlarge the diameter of the original beam emitted by the laser source, giving the beam a more suitable spot size during subsequent transmission and modulation to fit the effective working area of ​​the spatial light modulator 20. Fourier lens 80 and baffle 40 are respectively disposed on both sides of beam splitter 30. Fourier lens 80 is used to perform inverse Fourier transform on the modulated beam, and baffle 40 is used to prevent this path of light from being reflected back to CCD camera 10, thus preventing optical path interference. CCD camera 10 is disposed on the back focal plane of Fourier lens 80 and is used to receive and record the light field distribution image of sub-beams.

[0045] Before the laser beam is incident, it undergoes beam expansion, collimation, and polarization processing. The polarization processing is used to ensure that the laser beam meets the modulation requirements of the liquid crystal molecules in the spatial light modulator 20.

[0046] Specifically, the polarization processing is performed by the polarizer 50.

[0047] Further, the step S400 specifically comprises: S410: loading the complex phase distribution onto the spatial light modulator 20 to make the laser beam incident to the spatial light modulator 20 for phase modulation; S420: the modulated light beam is subjected to inverse Fourier transform by the Fourier lens 80 to form an array of Airy beams.

[0048] Working principle: a laser light source with a wavelength of 532 nm is used. The laser light is first processed by the polarizer 50 and then incident to a reflective spatial light modulator 20 with a resolution of 1920x1080 pixels and a pixel pitch of 4.5 μm. A designed phase plate is loaded onto the spatial light modulator 20. The exiting light passes through the beam splitter 30 and then through the Fourier lens 80 to be incident to the CCD camera 10. The CCD camera 10 records the generated Airy beam intensity part. By adjusting the movement and flipping factor of the light beam, the beam splitting and turning of the Airy beam array are realized.

[0049] Specifically, by loading the complex phase distribution onto an optical device with phase modulation function, the phase of the incident light beam is modulated by the complex phase distribution when passing through the device. Then, through the Fourier transform of the optical system, the frequency domain complex phase information is converted into the spatial domain light field distribution. Finally, an array composed of multiple Airy sub-beams is formed at the output end. Since the phase shift modulation factor of each sub-beam can be independently designed, the distribution position of each sub-beam in the generated multi-Airy beam array can be flexibly adjusted according to actual needs without relying on fixed array structure.

[0050] The following provides a specific embodiment: Parameter setting: determine the frequency domain variable and so that it is uniformly distributed in the interval (the phase modulation depth is ), is 0.05, the number of sampling points =1080, the deflection scale is -30, is -15; is -15, is 30.

[0051] The complex phase plate is calculated by the step S300. Taking two sub-beams as an example: The frequency domain signal of the sub-beam 1 is shown in the following formula (eight): Formula (eight); The frequency domain signal of the sub-beam 2 is shown in the following formula (IX) : Formula (IX) ; The composite frequency spectrum is shown in the following formula (X) : Formula (X) ; Load the phase plate shown in Figure 3 on the spatial light modulator 20, the laser beam is split and modulated into the upper left and lower left distribution, as shown in Figure 5 .

[0052] In the phase expression of the light field frequency domain, when the negative sign in the cubic phase term acts on the x variable (such as ), the phase distribution characteristics in the x direction will be changed, and according to the Fourier optics principle, the generated sub-beam spot in the x direction presents the flip effect; similarly, if the negative sign acts on the y variable, the sub-beam spot in the y direction will be flipped, as shown in Figure 6 .

[0053] Use the Dammann grating to generate an array of Airy beams for comparison, as shown in Figure 7 .

[0054] From Figure 7 , it can be seen that the Airy beam splitting method generated by the present application has high degree of freedom, and can design any distribution instead of matrix form. Only need to superimpose displacement information on the basis of the original phase plate information, the splitting and modulation function of a single phase plate can be realized, and low cost, miniaturization design is realized.

[0055] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features disclosed in the present application (but not limited to) having similar functions to form a technical solution.

Claims

1. A method for generating multiple Airy beams based on adjustable distribution, characterized in that, include: Construct the basic phase distribution of a single Airy beam; Design the phase shift modulation factor corresponding to the multi-beam sub-beam, wherein the phase shift modulation factor is set based on the displacement characteristics of the Fourier transform; The phase shift modulation factor is superimposed with the spectrum of a single-beam Airy beam to obtain a composite phase distribution; Based on the composite phase distribution, a multi-Airy beam array with adjustable distribution is generated.

2. The method for generating multiple Airy beams based on adjustable distribution according to claim 1, characterized in that, The basic phase distribution for constructing a single-beam Airy beam includes: Determine the frequency domain variables and attenuation factor, and construct the Airy beam phase plate function based on the frequency domain variables and attenuation factor; A single Airy beam is generated by loading the phase plate function through a spatial light modulator (20).

3. The method for generating multiple Airy beams based on adjustable distribution according to claim 2, characterized in that, The Airy beam phase plate function includes frequency domain x-axis coordinates and frequency domain y-axis coordinates.

4. The method for generating multiple Airy beams based on adjustable distribution according to claim 3, characterized in that, The phase shift modulation factor includes a phase term that is linearly related to the frequency domain variable, so as to modulate the spatial distribution of the sub-beam using the displacement characteristics of the Fourier transform.

5. The method for generating multiple Airy beams based on adjustable distribution according to claim 4, characterized in that, For the For each sub-beam, the expression for the phase shift modulation factor is: in, and Indicates the first Frequency domain shift parameters of individual beams and This represents a frequency domain variable.

6. The method for generating multiple Airy beams based on adjustable distribution according to claim 5, characterized in that, The superposition of the phase-shift modulation factor with the spectrum of a single-beam Airy light includes: The first Multiplying the phase shift modulation factor of each sub-beam by the spectrum of a single Airy beam yields the first... The phase-shifted spectrum of individual beams; Will The composite phase distribution is obtained by accumulating the phase-shifted spectra of each band.

7. The method for generating multiple Airy beams based on adjustable distribution according to claim 6, characterized in that, The multi-Airy beam array generated based on composite phase distribution includes: The composite phase distribution is loaded onto the spatial light modulator (20), and the laser beam is incident on the spatial light modulator (20) for phase modulation; The modulated beam undergoes inverse Fourier transform via a Fourier lens (80) to form a multi-Airy beam array.

8. The method for generating multiple Airy beams based on adjustable distribution according to claim 7, characterized in that, Before the laser beam is incident, it undergoes beam expansion, collimation, and polarization treatment. The polarization treatment is used to make the laser meet the liquid crystal molecule modulation requirements of the spatial light modulator (20).

9. The method for generating multiple Airy beams based on adjustable distribution according to claim 8, characterized in that, A CCD camera (10) is placed on the back focal plane of the Fourier lens (80) to receive and record the light field distribution image of the sub-beam.

10. The method for generating multiple Airy beams based on adjustable distribution according to claim 9, characterized in that, The spatial light modulator (20) is a reflective phase-type liquid crystal spatial light modulator.

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