Method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge

Abstract

The present invention relates to a method for shaping a flattened laser beam, and more specifically, to a method for constructing a triangular flattened laser beam with a super-Gaussian beam falling edge. This method addresses the shortcomings of existing laser beam shaping methods in shaping triangular, irregular flattened beams, such as insufficient top homogenization, low energy utilization, and difficulty controlling beam size. The method determines corresponding target triangular and square patterns based on an incident beam and a square super-Gaussian beam, forms a triangular flattened beam through geometric superposition and adjustment, and then calculates and optimizes the diffraction phase distribution using the triangular flattened beam as the iterative target beam. This diffraction phase distribution is then input into a spatial light modulator, where it is superimposed with a Fresnel lens phase, thereby shaping the incident beam with a Gaussian-shaped spot energy spatial distribution into a triangular flattened beam with a flattened-shaped spot energy spatial distribution.

Description

Technical Field

[0001] The invention relates to a flat-top laser beam shaping method, in particular to a method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge. Background Art

[0002] Laser processing technology has been widely used in various precision machining fields. Compared to continuous lasers, pulsed lasers exhibit significant advantages in industrial processing due to their extremely high instantaneous power density. Femtosecond lasers, in particular, have extremely short pulse widths and high peak power. When the peak light intensity exceeds the material's damage threshold, the material temperature rises rapidly and vaporizes, with most of the heat being removed, effectively reducing the thermal impact on non-active areas and achieving extremely high machining accuracy. Therefore, femtosecond lasers are highly favored in precision micro-nano machining, playing a key role in machining processes that require high precision and high surface quality.

[0003] However, the laser spot output by a femtosecond laser typically exhibits a Gaussian distribution, with the energy density highest at the center and gradually decreasing at the edges. This uneven energy distribution can lead to uneven energy distribution on the workpiece surface during machining, causing problems such as surface unevenness. This phenomenon is particularly pronounced in micro-nano machining, where high surface flatness is required, further highlighting the limitations of Gaussian spot energy distribution.

[0004] To overcome this problem, researchers have proposed a technical approach to convert a Gaussian spot into a flat-top spot with uniform energy distribution by spatially shaping the laser beam. A flat-top beam has the characteristics of uniform energy distribution and steep edges, which can significantly improve the accuracy and surface quality of laser processing. In the prior art, a variety of flat-top beam shaping methods based on diffraction optics have been developed. For example, the diffraction phase distribution is generated by analytical calculation or phase recovery algorithm, and recorded on a diffraction optical element or spatial light modulator to generate the required flat-top beam at the focal plane of the lens. These methods have shown good results in achieving circular or square flat-top beam shaping.

[0005] However, when it comes to shaping triangular and other shaped beams, current technologies still have many deficiencies. Existing methods mainly achieve the shaping of shaped beams through approximate analytical calculations or pattern substitution methods. However, since analytical calculations are difficult to accurately describe beams of complex shapes, the shaping effect is poor. Specifically, the top of the triangular flat-top beam has a low degree of uniformity, and there is severe speckle in the flat-top area, which affects the processing quality. In addition, in order to meet the needs of more complex micro-nanostructure processing, in addition to circular and square beams, more and more shaped beams, such as triangular beams, have become necessary. However, existing technologies can only achieve good results in shaping circular and square beams, but are obviously insufficient in shaping triangular beams, which seriously limits the efficiency and quality of micro-nanoprocessing technology.

[0006] Currently, the methods for achieving flat-top beam shaping are mainly divided into geometric optical shaping and diffraction optical shaping. The geometric optical shaping method adjusts the shape and energy distribution of the light beam by combining optical lenses to generate a flat-top beam of a specific shape; while the diffraction optical shaping method calculates the diffraction phase distribution and records the phase information on the optical element to generate a corresponding flat-top beam at the focal plane of the lens. In comparison, the diffraction optical shaping method has become the main beam shaping method due to its small equipment size, light weight and simple structure. In addition, compared with fixed-form diffraction optical elements, spatial light modulators have been widely used in various types of complex beam shaping due to their higher flexibility and programmability.

[0007] Despite this, research on direct shaping of triangular flat-top beams is still relatively scarce. Existing studies have mostly used triangular flat-top beam shaping to verify the universality of their methods, without conducting in-depth analysis of the shaping effects of triangular beams. For example, a study proposed a composite modulation algorithm that achieved good results in square beam shaping by simultaneously modulating amplitude and phase during the iterative optimization process. However, in triangular beam shaping, obvious stripe effects and low brightness appeared, which indirectly reflected the problem of insufficient energy utilization. In addition, although the dynamic amplitude limitation optimization algorithm for triangular beams can achieve good results in large-scale beam shaping, as the beam size increases, the laser energy density decreases, which is not conducive to the high-precision requirements of micro-nano processing. Although the hybrid phase grating shaping method can also achieve the shaping of various types of flat-top beams, in small-scale triangular beam shaping, the uniformity of its flat-top area is significantly reduced, and the energy utilization is low, which limits its application in micro-nano processing.

[0008] In summary, existing laser beam shaping methods for shaping triangular flat-top beams suffer from insufficient top homogenization, low energy efficiency, and difficulty controlling beam size. These issues make it difficult to simultaneously meet the demands of micro-nanofabrication for beam shape diversity, precision, and efficiency. Therefore, developing a new method for shaping triangular flat-top beams that achieves high homogenization and energy efficiency and is suitable for small-sized triangular flat-top beams is a key technical requirement for improving the efficiency and quality of micro-nanofabrication. Summary of the Invention

[0009] The purpose of the present invention is to solve the shortcomings of existing laser beam shaping methods in shaping triangular special-shaped flat-top beams, such as insufficient top homogenization, low energy utilization, and difficult control of beam size, and to provide a method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge.

[0010] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides the following technical solutions:

[0011] The method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge is special in that it includes the following steps:

[0012] Step 1, determining the parameters of the incident beam and the parameters of the square super-Gaussian beam;

[0013] Step 2: Determine a target triangular pattern and a square pattern with a side length equal to the base of the target triangle according to the cross section of the square super-Gaussian beam in step 1; the base and height of the target triangular pattern are both the side lengths of the cross section of the square super-Gaussian beam;

[0014] Step 3: Based on the square super-Gaussian beam prepared in step 1, the target triangular pattern and the square pattern prepared in step 2, geometrically superimpose and adjust the flat top region and the falling edge of the triangular flat top beam to obtain a triangular flat top beam with a falling edge of the super-Gaussian beam.

[0015] Step 4: Determine the initial quadratic phase φ(x, y) based on the parameters of the incident beam in step 1 and the parameters of the triangular flat-top beam obtained in step 3, and perform iterative optimization using a phase retrieval algorithm to obtain the optimized diffraction phase distribution;

[0016] Step 5: The optimized diffraction phase distribution obtained in step 4 is introduced into the spatial light modulator, and the Fresnel lens phase is superimposed on the spatial light modulator to complete the shaping of the triangular flat-top beam.

[0017] Furthermore, the step 3 is specifically as follows:

[0018] The center of the target triangular pattern is made to coincide with the center of the square super-Gaussian beam, with their bottom sides parallel, and the intersection area is taken as the flat-top area of ​​the triangular flat-top beam; the center of the square pattern is made to coincide with the center of the square super-Gaussian beam, with their bottom sides parallel, and the non-intersection area is retained as the falling edge of the triangular flat-top beam; the falling edge of the triangular flat-top beam is translated so that it intersects with the edge of the flat-top area of ​​the triangular flat-top beam, thereby obtaining a triangular flat-top beam with a super-Gaussian beam falling edge.

[0019] Furthermore, the step 4 is specifically as follows:

[0020] Step 4.1: The initial quadratic phase φ(x, y) is expressed as follows:

[0021] φ(x, y)=a(x-x0) 2 +b(y-y0) 2 +c

[0022] Where a and b are coefficients; the center of the phase distribution (x0, y0) coincides with the center of the triangular flat-top beam; c is a constant term representing the phase offset of the entire beam;

[0023] Step 4.2: Substitute the amplitude distribution function u of the incident beam in step 1 in , Step 4.1 Initial quadratic phase φ(x, y) as initial input, Step 3 Amplitude distribution u of triangular flat-top beam target As a constraint condition, the phase retrieval algorithm is used for iterative optimization to obtain the optimized diffraction phase distribution.

[0024] Furthermore, the step 4.2 is specifically as follows:

[0025] Step 4.2.1. Substitute the amplitude distribution function u of the incident beam in step 1 into in Step 4.1: Take the initial quadratic phase φ(x, y) as the initial input and calculate the initial complex amplitude U0(x, y);

[0026] Step 4.2.2: Perform a two-dimensional Fourier transform on the complex amplitude U0(x, y) to obtain the complex amplitude U in the frequency domain. f (f x , f y );

[0027] Step 4.2.3: In the frequency domain, transform the amplitude distribution u of the triangular flat-top beam into target As a constraint, the complex amplitude U in the frequency domain f (f x , f y ) is adjusted to retain only the target amplitude distribution, and the updated complex amplitude U′ in the frequency domain is obtained. f (f x , fy );

[0028] Step 4.2.4: Update the complex amplitude U′ in the frequency domain f (f x , f y ) performs an inverse Fourier transform to obtain the complex amplitude U1(x, y) in the spatial domain;

[0029] U1(x,y)=|U1(x,y)|·exp[iφ1(x,y)]

[0030] Among them, φ1(x, y) is the current phase distribution;

[0031] Step 4.2.5: Replace the amplitude |U1(x, y)| in the target area on the reconstruction surface with the amplitude distribution u of the triangular flat-top beam target , the amplitude in the non-target area remains unchanged, and the current phase distribution φ1(x, y) remains unchanged, and a new complex amplitude U′1(x, y) is obtained;

[0032] Step 4.2.6: Calculate the average light intensity of the target area on the reconstruction surface Top homogenization degree γ and energy utilization rate ρ;

[0033] Step 4.2.7: Determine whether the top homogenization degree γ meets the requirements or whether the number of iterations reaches the maximum value. If so, stop the iteration and output the current phase distribution as the optimized diffraction phase distribution. Otherwise, perform iterative optimization according to steps 4.2.2 to 4.2.7.

[0034] Furthermore, in step 4.2.6, the average light intensity of the target area on the reconstruction surface is The top homogenization degree γ and energy utilization rate ρ are as follows:

[0035]

[0036] Where W represents the target area on the reconstruction surface; I(ε, η) represents the light intensity distribution at the coordinate (ε, η) on the reconstruction surface; and n represents the total number of samples of discrete points in the target area.

[0037] Furthermore, in step 1, the parameters of the incident light beam include the wavelength λ of the incident light beam, the beam waist radius w1 and the amplitude distribution function u in The parameters of the square super-Gaussian beam include the side length d of the square super-Gaussian beam and the amplitude distribution function u t .

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention provides a method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge. The method determines corresponding target triangular and square patterns based on an incident beam and a square super-Gaussian beam, forms a triangular flat-top beam through geometric superposition and adjustment, and then uses the triangular flat-top beam as an iterative target beam to calculate and optimize the diffraction phase distribution. This is then input into a spatial light modulator, and the Fresnel lens phase is superimposed to reshape the incident beam with a Gaussian spot energy spatial distribution into a triangular flat-top beam with a flat-top spot energy spatial distribution.

[0040] The present invention overcomes the problems of low top homogeneity and severe speckle in the shaped flat-top beam caused by iterative optimization using a triangular pattern as the target beam and a random phase as the initial value of the diffraction phase distribution in the traditional phase retrieval algorithm. At the same time, the superimposed Fresnel lens phase can also effectively solve the problem of zero-order diffraction spot generated by the pixel spacing area of ​​the spatial light modulator in the flat-top beam shaping experiment, thereby obtaining a triangular flat-top beam with high top homogeneity, high energy utilization, small size and no zero-order diffraction spot. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Flowchart of an embodiment of a method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge according to the present invention;

[0042] Figure 2 is a two-dimensional diagram of the energy distribution of the circular Gaussian beam in step 1 of an embodiment of the present invention;

[0043] Figure 3 is a three-dimensional diagram of the energy distribution of the circular Gaussian beam in step 1 of an embodiment of the present invention;

[0044] Figure 4 is a two-dimensional diagram of the energy distribution of the square super-Gaussian beam in step 1 of an embodiment of the present invention;

[0045] Figure 5 is a three-dimensional diagram of the energy distribution of the square super-Gaussian beam in step 1 of an embodiment of the present invention;

[0046] Figure 6 3 is a schematic diagram of the process of forming the flat top region and falling edge of a triangular flat top beam by geometric superposition and adjustment in step 3 of an embodiment of the present invention;

[0047] Figure 7 is a distribution diagram of the initial secondary phase in step 4.1 of the embodiment of the present invention;

[0048] Figure 8 is the optimized diffraction phase distribution in step 4.2.7 of the embodiment of the present invention;

[0049] Figure 9is a two-dimensional diagram of the energy distribution of the triangular flat-top beam in step 5 of an embodiment of the present invention;

[0050] Figure 10 is a three-dimensional diagram of the energy distribution of the triangular flat-top beam in step 5 of an embodiment of the present invention;

[0051] Figure 11 is the diffraction phase distribution of a triangular flat-top beam generated directly using the triangular pattern as the target flat-top beam;

[0052] Figure 12 It is a two-dimensional diagram of the energy distribution of a triangular flat-top beam generated by directly using the triangular pattern as the target flat-top beam;

[0053] Figure 13 This is a 3D diagram of the energy distribution of a triangular flat-top beam generated by directly using a triangular pattern as the target flat-top beam. DETAILED DESCRIPTION

[0054] The present invention will be further described below with reference to the accompanying drawings and exemplary embodiments.

[0055] Reference Figures 1 to 7 A method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge comprises the following steps:

[0056] Step 1, determining the parameters of the incident beam and the parameters of the square super-Gaussian beam;

[0057] Step 1.1. The parameters of the incident beam are determined by the laboratory instrument, including the wavelength λ, the beam waist radius w1 and the amplitude distribution function u in Specifically, the incident beam has a wavelength of λ1053nm and a beam waist radius (measured by a beam quality analyzer, the light intensity drops to 1 / e 2 A circular Gaussian beam with a Gaussian spot energy distribution of 13.6 mm (radius at the center);

[0058] The focal length f of the lens is 150 mm, and the amplitude distribution function u of the circular Gaussian beam with Gaussian spot energy spatial distribution is in satisfy:

[0059]

[0060] Wherein, A is the amplitude of the incident light beam, which is normalized and set to 1; x and y represent the horizontal and vertical coordinates on the spatial light modulator, respectively; Figure 2 、 Figure 3 2D and 3D diagrams showing the energy distribution of a circular Gaussian beam;

[0061] Step 1.2: The parameters of the square super-Gaussian beam include the side length d and the amplitude distribution function u of the square super-Gaussian beam. t ;

[0062] Amplitude distribution function u of a square super-Gaussian beam t satisfy:

[0063]

[0064] Where B is the amplitude of the square super-Gaussian beam, which is normalized and set to 1. ε and η represent the horizontal and vertical coordinates of the reconstruction surface, respectively. The exponent 20 determines the steepness of the beam edge. Figure 4 、 Figure 5 Two-dimensional and three-dimensional diagrams showing the energy distribution of a square super-Gaussian beam;

[0065] Step 2: determining a target triangle pattern and a square pattern having a side length equal to the base of the target triangle according to the cross section of the square super-Gaussian beam in Step 1;

[0066] The base and height of the target triangle pattern are both 760 μm, and the side length of the square pattern is 760 μm;

[0067] Step 3: Based on the square super-Gaussian beam prepared in step 1, the target triangular pattern and the square pattern prepared in step 2, geometrically superimpose and adjust the flat top region and the falling edge of the triangular flat top beam to obtain a triangular flat top beam with a falling edge of the super-Gaussian beam.

[0068] Reference Figure 6 , the center of the target triangular pattern is overlapped with the center of the square super-Gaussian beam, and the bases are parallel, and the intersection area (triangular area) is taken as the flat top area of ​​the triangular flat top beam; the center of the square pattern is overlapped with the center of the square super-Gaussian beam, and the bases are parallel, and the non-intersection area is retained as the falling edge of the triangular flat top beam; the non-intersection area is retained as the falling edge of the triangular flat top beam; the falling edge of the triangular flat top beam is translated so that it intersects with the edge of the flat top area of ​​the triangular flat top beam, and a triangular flat top beam with a super-Gaussian beam falling edge is obtained;

[0069] Step 4: Determine the initial quadratic phase based on the parameters of the incident beam in step 1 and the parameters of the triangular flat-top beam obtained in step 3, and perform iterative optimization using a phase retrieval algorithm to obtain an optimized diffraction phase distribution;

[0070] Step 4.1, reference Figure 7 , the initial quadratic phase φ(x, y) is expressed as follows:

[0071] φ(x, y)=a(x-x0) 2 +b(y-y0) 2 +c

[0072] Where a and b are coefficients; the center of the phase distribution (x0, y0) coincides with the center of the triangular flat-top beam; c is a constant term representing the phase offset of the entire beam;

[0073] Step 4.2: Substitute the amplitude distribution function u of the incident beam in step 1 in , Step 4.1 Initial quadratic phase φ(x, y) as initial input, Step 3 Amplitude distribution u of triangular flat-top beam target As a constraint condition, the phase retrieval algorithm is used for iterative optimization to obtain the optimized diffraction phase distribution;

[0074] Step 4.2.1. Substitute the amplitude distribution function u of the incident beam in step 1 into in Step 4.1: Take the initial quadratic phase φ(x, y) as the initial input and calculate the initial complex amplitude U0(x, y);

[0075] Step 4.2.2: Perform a two-dimensional Fourier transform on the complex amplitude U0(x, y) to obtain the complex amplitude U in the frequency domain. f (f x , f y );

[0076] Step 4.2.3: In the frequency domain, transform the amplitude distribution u of the triangular flat-top beam into target As a constraint, the complex amplitude U in the frequency domain f (f x , f y ) is adjusted to retain only the target amplitude distribution, and the updated complex amplitude U′ in the frequency domain is obtained. f (f x , f y );

[0077] Step 4.2.4: Update the complex amplitude U′ in the frequency domain f (f x , f y ) performs an inverse Fourier transform to obtain the complex amplitude U1(x, y) in the spatial domain;

[0078] U1(x,y)=|U1(x,y)|·exp[iφ1(x,y)]

[0079] Among them, φ1(x, y) is the current phase distribution;

[0080] Step 4.2.5. Replace the amplitude |U1(x, y)| in the target area on the reconstruction surface (the triangular flat-top area, i.e., the actual projection area of ​​the triangular flat-top beam on the reconstruction surface) with the amplitude distribution u of the triangular flat-top beam. target, the amplitude in the non-target area remains unchanged, and the current phase distribution φ1(x, y) is kept unchanged, and a new complex amplitude U′1(x, y) is obtained, which is used for Fourier transform in the next iteration to further optimize the beam shape;

[0081] Step 4.2.6: Calculate the average light intensity of the target area on the reconstruction surface Top homogenization degree γ and energy utilization rate ρ;

[0082] Step 4.2.7: Determine whether the top homogenization degree γ meets the requirement or whether the number of iterations reaches the maximum value. If so, stop the iteration and output the current phase distribution as the optimized diffraction phase distribution, such as Figure 8 Otherwise, perform iterative optimization according to steps 4.2.2 to 4.2.7;

[0083]

[0084] Where W represents the target area on the reconstruction surface; I(ε, η) represents the light intensity distribution at the coordinate (ε, η) on the reconstruction surface; n represents the total number of samples of discrete points in the target area;

[0085] Step 5: The optimized diffraction phase distribution obtained in step 4 is introduced into the spatial light modulator, and the phase of the Fresnel lens with a focal length of 500 mm is superimposed on the spatial light modulator to achieve a triangular flat-top beam with high top homogenization, high energy utilization, small size and no zero-order diffraction spot, as shown in FIG. Figure 9 、 Figure 10 shown.

[0086] When the incident light beam in step 1 illuminates the spatial light modulator, a triangular flat-top beam with a bottom side length and a height of 760 μm is generated on the reconstruction surface, as shown in Figures 8 to 10 As shown, the theoretical value of its top homogenization is as high as 0.998, and the energy utilization rate is also maintained at 75.5%. This triangular flat-top beam has high top homogenization, high energy utilization rate, small size and no zero-order diffraction spot.

[0087] The embodiment of the present invention is compared with the direct use of a triangular pattern as the target flat-top beam, and the same initial quadratic phase is introduced as the initial phase, and the phase recovery algorithm is used to calculate the shaping phase required for shaping. Figures 11 to 13 As shown in FIG, there are many singular points in the obtained diffraction phase. The triangular flat-top beam obtained with this phase has severe speckles, and its top homogenization is only 0.829.

[0088] In summary, the present invention constructs a triangular flat-top beam with a super-Gaussian beam trailing edge by confirming the parameters of the incident beam and the square super-Gaussian beam. It then introduces an initial quadratic phase as the initial phase for iterative optimization, obtaining an optimized diffraction phase distribution. This optimized diffraction phase distribution is then introduced into a spatial light modulator and superimposed with the Fresnel lens phase to generate a triangular flat-top beam on the reconstruction surface of the rear lens. The present invention can simultaneously achieve a triangular flat-top beam with high top homogenization, high energy utilization, a small size, and no zero-order diffraction spot, meeting the processing requirements for special-shaped beams in actual micro-nano processing scenarios. Therefore, the present invention has broad application prospects.

Claims

1. A method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge, characterized in that: The steps include: Step 1, determining the parameters of the incident beam and the parameters of the square super-Gaussian beam; Step 2: Determine a target triangular pattern and a square pattern with a side length equal to the base of the target triangle according to the cross section of the square super-Gaussian beam in step 1; the base and height of the target triangular pattern are both the side lengths of the cross section of the square super-Gaussian beam; Step 3: Based on the square super-Gaussian beam prepared in step 1, the target triangular pattern and the square pattern prepared in step 2, geometrically superimpose and adjust the flat top region and the falling edge of the triangular flat top beam to obtain a triangular flat top beam with a falling edge of the super-Gaussian beam. Step 4: Determine the initial quadratic phase φ(x, y) based on the parameters of the incident beam in step 1 and the parameters of the triangular flat-top beam obtained in step 3, and perform iterative optimization using a phase retrieval algorithm to obtain the optimized diffraction phase distribution; Step 5: The optimized diffraction phase distribution obtained in step 4 is introduced into the spatial light modulator, and the Fresnel lens phase is superimposed on the spatial light modulator to complete the shaping of the triangular flat-top beam.

2. The method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge according to claim 1, characterized in that: The step 3 is specifically as follows: The center of the target triangular pattern is made to coincide with the center of the square super-Gaussian beam, with their bottom sides parallel, and the intersection area is taken as the flat-top area of ​​the triangular flat-top beam; the center of the square pattern is made to coincide with the center of the square super-Gaussian beam, with their bottom sides parallel, and the non-intersection area is retained as the falling edge of the triangular flat-top beam; the falling edge of the triangular flat-top beam is translated so that it intersects with the edge of the flat-top area of ​​the triangular flat-top beam, thereby obtaining a triangular flat-top beam with a super-Gaussian beam falling edge.

3. The method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge according to claim 1 or 2, characterized in that: The step 4 is specifically as follows: Step 4.1: The initial quadratic phase φ(x, y) is expressed as follows: φ(x,y)=a(x-x0) 2 +b(y-y0) 2 +c Where a and b are coefficients; the center of the phase distribution (x0, y0) coincides with the center of the triangular flat-top beam; c is a constant term representing the phase offset of the entire beam; Step 4.2: Substitute the amplitude distribution function u of the incident beam in step 1 in , Step 4.1 Initial quadratic phase φ(x, y) as initial input, Step 3 Amplitude distribution u of triangular flat-top beam target As a constraint condition, the phase retrieval algorithm is used for iterative optimization to obtain the optimized diffraction phase distribution.

4. The method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge according to claim 3, characterized in that: The step 4.2 is specifically as follows: Step 4.2.

1. Substitute the amplitude distribution function u of the incident beam in step 1 into in Step 4.1: Take the initial quadratic phase φ(x, y) as the initial input and calculate the initial complex amplitude U0(x, y); Step 4.2.2: Perform a two-dimensional Fourier transform on the complex amplitude U0(x, y) to obtain the complex amplitude U in the frequency domain. f (f x , f y ); Step 4.2.3: In the frequency domain, transform the amplitude distribution u of the triangular flat-top beam into target As a constraint, the complex amplitude U in the frequency domain f (f x , f y ) is adjusted to retain only the target amplitude distribution, and the updated complex amplitude U′ in the frequency domain is obtained. f (f x , f y ); Step 4.2.4: Update the complex amplitude U′ in the frequency domain f (f x , f y ) performs an inverse Fourier transform to obtain the complex amplitude U1(x, y) in the spatial domain; U1(x,y)=|U1(x,y)|·exp[iφ1(x,y)] Among them, φ1(x, y) is the current phase distribution; Step 4.2.5: Replace the amplitude |U1(x, y)| in the target area on the reconstruction surface with the amplitude distribution u of the triangular flat-top beam target , the amplitude in the non-target area remains unchanged, and the current phase distribution φ1(x, y) remains unchanged, and a new complex amplitude U′1(x, y) is obtained; Step 4.2.6: Calculate the average light intensity of the target area on the reconstruction surface Top homogenization degree γ and energy utilization rate ρ; Step 4.2.7: Determine whether the top homogenization degree γ meets the requirements or whether the number of iterations reaches the maximum value. If so, stop the iteration and output the current phase distribution as the optimized diffraction phase distribution. Otherwise, perform iterative optimization according to steps 4.2.2 to 4.2.

7.

5. The method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge according to claim 4, characterized in that: In step 4.2.6, the average light intensity of the target area on the reconstruction surface The top homogenization degree γ and energy utilization rate ρ are as follows: Where W represents the target area on the reconstruction surface; I(ε, η) represents the light intensity distribution at the coordinate (ε, η) on the reconstruction surface; and n represents the total number of samples of discrete points in the target area.

6. The method for constructing a triangular flat-top laser beam with a super-Gaussian beam falling edge according to claim 1, characterized in that: In step 1, the parameters of the incident light beam include the wavelength λ of the incident light beam, the beam waist radius w1 and the amplitude distribution function u in The parameters of the square super-Gaussian beam include the side length d of the square super-Gaussian beam and the amplitude distribution function u t .

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