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

Abstract

The invention relates to a method for shaping a flat-topped laser beam, in particular to a method for constructing a triangular flat-topped laser beam with a super Gaussian beam falling edge. The method is used for solving the problems of insufficient top uniformity, low energy utilization rate, difficulty in controlling the size of the light beam and the like in the shaping aspect of the triangular special-shaped flat-topped light beam in the existing laser beam shaping method. According to the method for constructing the triangular flat-topped laser beam with the super Gaussian beam falling edge, a corresponding target triangular pattern and a corresponding square pattern are determined according to an incident beam and a square super Gaussian beam, a triangular flat-topped beam is formed through geometric superposition and adjustment, and then the triangular flat-topped beam is used as an iterative target beam to form the triangular flat-topped laser beam with the super Gaussian beam falling edge. And calculating the optimized diffraction phase distribution, inputting the optimized diffraction phase distribution into a spatial light modulator, superposing a Fresnel lens phase, and shaping an incident beam with Gaussian light spot energy space distribution into a triangular flat-topped beam with flat-topped light spot energy space 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 processing fields. Compared with continuous lasers, pulsed lasers have significant advantages in industrial processing due to their extremely high instantaneous power density. Especially for femtosecond lasers, due to their extremely short pulse width and high peak power, when the peak light intensity exceeds the damage threshold of the material, the material temperature will rise rapidly and vaporize, and most of the heat will be taken away, thereby effectively reducing the thermal impact on non-active areas and achieving extremely high processing accuracy. Therefore, femtosecond lasers are highly favored in precision micro-nano processing, especially in processing processes that require high precision and high surface quality, playing a key role.

[0003] However, the laser spot output by a femtosecond laser usually presents a Gaussian distribution, that is, the energy density at the center of the spot is the highest, while the energy at the edge gradually decreases. This uneven energy distribution will lead to uneven energy distribution on the workpiece surface during processing, thus causing problems such as surface unevenness. This phenomenon is particularly obvious in micro-nano processing that requires high surface flatness, further highlighting the limitations of Gaussian spot energy distribution.

[0004] To overcome this problem, researchers have proposed a technical means to convert the Gaussian spot into a flat-top spot with uniform energy distribution by spatially shaping the laser beam. The 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 a spatial light modulator to generate the required flat-top beam in the focal plane of the lens. These methods have shown good results in achieving circular or square flat-top beam shaping.

[0005] However, the current technology still has many shortcomings in shaping triangular and other shaped beams. 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 not good. Specifically, the uniformity of the top of the triangular flat-top beam is low, and there is serious speckle in the flat-top area, which affects the processing quality. In addition, in order to meet the needs of more complex micro-nano structure processing, in addition to circular and square beams, more and more shaped beams, such as triangular beams, have become necessary. However, the existing technology can only achieve good results in shaping circular and square beams, but the effect is obviously insufficient in shaping triangular beams, which seriously limits the efficiency and quality of micro-nano processing technology.

[0006] At present, 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 the corresponding flat-top beam in the focal plane of the lens. In contrast, the diffraction optical shaping method has become the main beam shaping method due to its small 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, direct shaping research on 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, but have not conducted in-depth analysis of the shaping effect of triangular beams. For example, a study proposed a composite modulation algorithm that simultaneously modulated the amplitude and phase during the iterative optimization process, achieving good results in square beam shaping, but an obvious stripe effect and low brightness appeared in triangular beam shaping, 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-size 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 realize the shaping of various types of flat-top beams, in the shaping of small-size triangular beams, the homogenization degree of the flat-top area is significantly reduced, and the energy utilization is low, which limits its application in micro-nano processing.

[0008] In summary, the existing laser beam shaping methods have problems such as insufficient top homogenization, low energy utilization, and difficult control of beam size in the shaping of triangular special-shaped flat-top beams, which makes it difficult to simultaneously meet the requirements of micro-nano processing for beam shape diversity, precision, and efficiency. Therefore, developing a new method that can achieve high homogenization, high energy utilization, and is suitable for small-sized triangular flat-top beam shaping has become a key technical requirement for improving micro-nano processing efficiency and quality. Summary of the invention

[0009] The purpose of the present invention is to solve the shortcomings of the existing laser beam shaping methods in the shaping of 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 whose side length is 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, according to the square super-Gaussian beam in step 1, the target triangular pattern and the square pattern in step 2, through geometric superposition and adjustment, the flat top area and the falling edge of the triangular flat top beam are formed, and a triangular flat top beam with a super-Gaussian beam falling edge is obtained;

[0015] Step 4, determining the initial quadratic phase φ(x, y) according to the parameters of the incident light beam in step 1 and the parameters of the triangular flat-top light beam obtained in step 3, and performing iterative optimization using a phase recovery algorithm to obtain an optimized diffraction phase distribution;

[0016] Step 5: Import the optimized diffraction phase distribution obtained in step 4 into the spatial light modulator, and superimpose the Fresnel lens phase 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 overlapped with the center of the square super-Gaussian beam, and the bottom sides are 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 overlapped with the center of the square super-Gaussian beam, and the bottom sides are 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, and a triangular flat top beam with a super Gaussian beam falling edge is obtained.

[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 shift 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 The initial quadratic phase φ(x, y) is used as the initial input to 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 obtain the updated complex amplitude U′ in the frequency domain f (f x , fy );

[0028] Step 4.2.4: Update the complex amplitude U′ in the frequency domain f (f x , f y ) performs 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] Wherein, W represents the target area on the reconstruction surface; I(ε, η) represents the light intensity distribution of the coordinates (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 invention discloses a method for constructing a triangular flat-top laser beam with a descending edge of a super-Gaussian beam. The method determines the corresponding target triangular pattern and square pattern according to the incident beam and the square super-Gaussian beam, forms a triangular flat-top beam through geometric superposition and adjustment, and then uses the triangular flat-top beam as the iterative target beam to calculate the optimized diffraction phase distribution, which is then input into a spatial light modulator, and then superimposed with the phase of a Fresnel lens to shape the incident beam with a Gaussian-type spot energy spatial distribution into a triangular flat-top beam with a flat-top-type spot energy spatial distribution.

[0040] The present invention overcomes the problems of low top homogenization and severe speckle of the shaped flat-top beam caused by iterative optimization using a triangular pattern as a target beam and a random phase as an initial value of the diffraction phase distribution in a traditional phase recovery 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, and obtains a triangular flat-top beam with high top homogenization, high energy utilization, small size and no zero-order diffraction spot. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart 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 energy distribution of a circular Gaussian beam in step 1 of an embodiment of the present invention;

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

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

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

[0046] Figure 6 It is a schematic diagram of the process of forming the flat top area and the falling edge of the triangular flat top beam by geometric superposition and adjustment in step 3 of the 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] Fig. 9is a two-dimensional diagram of energy distribution of the triangular flat-top beam in step 5 of the embodiment of the present invention;

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

[0051] Fig.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] Fig.12 It is a two-dimensional diagram of the energy distribution of a triangular flat-top beam generated directly using the triangular pattern as the target flat-top beam;

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

[0054] The present invention will be further described below in conjunction with 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 of the incident beam. 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 of the central light intensity 2 A circular Gaussian beam with a Gaussian spot energy distribution of 13.6 mm (radius at 13.6 mm);

[0058] The focal length 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 index 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 whose side length is 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, according to the square super-Gaussian beam in step 1, the target triangular pattern and the square pattern in step 2, through geometric superposition and adjustment, the flat top area and the falling edge of the triangular flat top beam are formed, and a triangular flat top beam with a super-Gaussian beam falling edge is obtained;

[0068] Reference Figure 6 , the center of the target triangular pattern is overlapped with the center of the square super-Gaussian beam, and the bottom sides 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 bottom sides 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 falling edge of a super-Gaussian beam is obtained;

[0069] Step 4, determining the initial quadratic phase according to the parameters of the incident light beam in step 1 and the parameters of the triangular flat-top light beam obtained in step 3, and performing iterative optimization using a phase recovery 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 shift 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 The initial quadratic phase φ(x, y) is used as the initial input to 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 obtain the updated complex amplitude U′ in the frequency domain 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 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 As shown; 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, such as Fig. 9 , Fig.10 shown.

[0086] When the incident light beam in step 1 irradiates 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, such as 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 directly using a triangular pattern as the target flat-top beam, and the same initial secondary 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, the obtained diffraction phase has many singular points, and the triangular flat-top beam obtained with this phase has serious speckles, and its top homogenization degree is only 0.829.

[0088] In summary, the present invention constructs a triangular flat-top beam with a falling edge of a super-Gaussian beam by confirming the parameters of the incident beam and the square super-Gaussian beam, introduces the initial quadratic phase as the initial phase for iterative optimization, obtains the optimized diffraction phase distribution, imports the optimized diffraction phase distribution into the spatial light modulator, and superimposes 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, small size and no zero-order diffraction spot, and meets 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 whose side length is 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, according to the square super-Gaussian beam in step 1, the target triangular pattern and the square pattern in step 2, through geometric superposition and adjustment, the flat top area and the falling edge of the triangular flat top beam are formed, and a triangular flat top beam with a super-Gaussian beam falling edge is obtained; Step 4, determining the initial quadratic phase φ(x, y) according to the parameters of the incident light beam in step 1 and the parameters of the triangular flat-top light beam obtained in step 3, and performing iterative optimization using a phase recovery algorithm to obtain an optimized diffraction phase distribution; Step 5: Import the optimized diffraction phase distribution obtained in step 4 into the spatial light modulator, and superimpose the Fresnel lens phase 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 overlapped with the center of the square super-Gaussian beam, and the bottom sides are 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 overlapped with the center of the square super-Gaussian beam, and the bottom sides are 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, and a triangular flat top beam with a super Gaussian beam falling edge is obtained.

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 shift 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 The initial quadratic phase φ(x, y) is used as the initial input to 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 obtain the updated complex amplitude U′ in the frequency domain f (f x , f y ); Step 4.2.4: Update the complex amplitude U′ in the frequency domain f (f x , f y ) performs 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: Wherein, W represents the target area on the reconstruction surface; I(ε, η) represents the light intensity distribution of the coordinates (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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