A metasurface lens for shaping a gaussian light into parallel uniform light and a design method

Abstract

The application discloses a metasurface lens for shaping Gaussian light into parallel uniform light and a design method, and belongs to the technical field of lasers.The metasurface lens comprises a dielectric substrate layer and a metasurface microstructure; the metasurface microstructure comprises a first metasurface and a second metasurface which are respectively distributed on two sides of the dielectric substrate layer and are both formed by periodically arranging a plurality of columnar microstructure units; the distribution mode of the columnar microstructure units of the metasurface lens is optimized and designed based on the irradiance distribution of Gaussian light and target parallel uniform light, so that the emergent light beam is parallel to the optical axis and is uniformly distributed within the target range.The shaping of laser is realized, and the target light beam is obtained; meanwhile, the optical system structure is simple, the application range is wide, and the laser shaping is suitable for a plurality of lasers.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and more specifically, relates to a metasurface lens and its design method for shaping Gaussian light into parallel uniform light. Background Technology

[0002] Lasers are generally Gaussian beams, meaning their intensity follows a Gaussian distribution in space. Such beams have a very high intensity in the center, gradually decreasing outwards along a Gaussian profile. In practical applications, non-uniform energy distribution can lead to localized excessively high temperatures, affecting the interaction between the laser and matter, while simultaneously resulting in low energy at the periphery, reducing utilization and limiting laser applications. Therefore, in many laser applications, Gaussian beams need to be shaped to obtain a flat-top beam with good uniformity. A flat-top beam refers to a laser beam with a uniform energy density across its cross-section along the beam's propagation direction. Due to its uniform energy distribution, it has important applications in laser welding, laser drilling, laser ablation, laser medicine, and laser displays. A uniform spot allows for uniform laser treatment of the work surface, avoiding material damage. Furthermore, the sharp boundary of the spot clearly distinguishes treated and untreated areas. However, the intensity and shape of a flat-top beam change when propagating in free space, making it unsuitable for long-distance propagation. Parallel uniform light, on the other hand, not only possesses the characteristics of a flat-top beam but is also a set of parallel rays with minimal attenuation over a certain distance.

[0003] Currently, the main methods for achieving laser beam shaping and homogenization include aspherical lens methods and diffractive optical element methods. Aspherical lens methods are designed based on geometric optics principles and contain one or more aspherical lenses. Their disadvantages include large size, complex structure, and high cost. Diffractive optical element methods are designed based on diffractive optics principles and typically include a diffractive optical element and a focusing lens adjacent to it. However, these methods suffer from complex fabrication processes for diffractive optical elements, difficulties in integrating them with refractive lenses, challenges in reducing size, and high cost. Furthermore, due to the immaturity of multiple photolithography processes, the phase distribution requires quantitative design, making it difficult to achieve continuous phase change control for more precise wavefront modulation.

[0004] Metasurface lenses are thin, lightweight, and compact, featuring flat surfaces with nanostructures that allow for precise control of incident light through artificially designed nanostructures. Currently, metasurface lenses are also used for laser collimation or spot shaping. For example, Chinese patent CN112859206B discloses a method for fabricating an all-dielectric metalens that shapes Gaussian light into a flat-top beam. However, this method only shapes the incident light into a flat-top beam, i.e., uniformly distributed on the image plane, without achieving parallel emission of the outgoing light. This results in limitations on the working distance of the all-dielectric metalens described in this patent and certain tolerance requirements for the distance between the lens and the image plane, which is detrimental to practical assembly applications. Summary of the Invention

[0005] In view of the shortcomings of related technologies, the purpose of this invention is to provide a metasurface lens and design method for shaping Gaussian light into parallel uniform light, which aims to simplify existing optical systems, reduce the limitation on working distance, and reduce the requirements for assembly accuracy.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a metasurface lens for shaping a Gaussian beam into parallel uniform light, the metasurface lens comprising: a dielectric substrate layer and a metasurface structure.

[0007] The metasurface lens is used to shape the incident Gaussian beam into an outgoing beam that is parallel to the optical axis and uniformly distributed within the target range.

[0008] The metasurface microstructure is composed of multiple columnar microstructure units arranged in a periodic array of tetragonal or hexagonal lattices; the distribution of the columnar microstructure units is matched with the incident beam, so that the outgoing beam is parallel to the optical axis and uniformly distributed within the target range.

[0009] Optionally, the columnar microstructure units all have the same height and are on the order of the wavelength of the incident laser emitted by the laser, and the diameter of the columnar microstructure units is on the order of the subwavelength.

[0010]

[0011]

[0012] in, and Let A represent the phase distributions of the first and second metasurfaces, respectively, where ρ is the radial coordinate of the metasurface, R is the normalized radius, n is the maximum number of terms in the phase distribution, and A is the maximum number of terms in the phase distribution. i and B i (i = 1, 2, 3, ... n) are all polynomial coefficients.

[0013] Optionally, the diameter, period, height, and arrangement of the columnar microstructure units are determined according to the corresponding phase distribution.

[0014] Optionally, both sides of the metasurface lens are coated with anti-reflective and anti-reflective coatings.

[0015] Optionally, the refractive index of the columnar microstructure unit is greater than or equal to the refractive index of the dielectric substrate layer.

[0016] Optionally, the metasurface lens is a double-sided metasurface lens.

[0017] In a second aspect, the present invention also provides a method for designing a metasurface lens that shapes Gaussian light into parallel uniform light as described in any one of the first aspects, comprising:

[0018] S1. Calculate the phase distribution of the metasurface lens based on the operating wavelength of the laser emitter, the beam waist diameter of the emitted laser, and the shape and size of the target spot.

[0019] S2, calculate the parameters of the outgoing beam formed after the laser is shaped by the metasurface lens based on the current phase distribution of the metasurface lens. The parameters of the outgoing beam include the shape, size and uniformity of the light spot on the image plane.

[0020] S3. If the shape, size, and uniformity of the emitted beam spot on the image plane meet the design requirements, proceed to S5; otherwise, based on the working wavelength of the laser emitter and the beam waist diameter of the emitted laser, optimize and update the phase distribution parameters of the metasurface lens using the damped least squares method and a custom optimization algorithm.

[0021] S4, bring in the updated phase distribution and repeat S2-S3 until the shape, size and uniformity of the outgoing beam spot on the image plane obtained in S2 meet the design requirements;

[0022] S5, Design the size and arrangement of multiple columnar microstructure units in the metasurface lens according to the current phase distribution of the metasurface lens;

[0023] S6. The metasurface lens is prepared based on the data in S5 to construct a laser shaping optical system.

[0024] Optionally, S5 includes:

[0025] The target phase distribution of the metasurface lens is fitted with coefficients so that the discrete points of the fitted phase distribution correspond one-to-one with the columnar microstructure units of the metasurface lens.

[0026] Simulation was used to obtain the correspondence between the size, phase distribution, and transmittance of the columnar microstructure unit in the metasurface lens;

[0027] The corresponding relationship is queried based on the phase distribution after coefficient fitting to obtain the size and arrangement of multiple columnar microstructure units.

[0028] Optionally, the simulation to obtain the correspondence between the size and phase distribution of the columnar microstructure units in the metasurface lens includes:

[0029] Based on the finite-difference time-domain algorithm and rigorous coupled-wave analysis method, the dimensional parameters of the columnar microstructure unit of the metasurface lens are simulated to determine the correspondence between the height, period, and diameter of the columnar microstructure unit and the phase distribution and transmittance.

[0030] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following results.

[0031] Beneficial effects:

[0032] 1. This invention provides a metasurface lens for shaping Gaussian light into parallel and uniform light. The metasurface lens, with its ability to finely control the incident light, achieves the shaping of laser light and the parallel and uniform emission of the target beam. It has no strict requirements on the working distance and the tolerance requirements for the distance between the laser beam and the image plane are not high, thus reducing the limitation on the working distance and lowering the requirements for assembly precision. It simplifies the structure of the optical system, has a wide range of applications, and is suitable for laser shaping of various lasers.

[0033] 2. This invention provides a metasurface lens that shapes Gaussian light into parallel uniform light. By using an optimization function algorithm with personalized settings in simulation software and a damped least squares method to optimize the normalized radius R and phase distribution polynomial coefficients of the metasurface lens, the distribution mode of the tetragonal or hexagonal lattice periodic array of the metasurface microstructure is determined. This allows for precise adjustment of the phase and amplitude distribution of the beam, achieving beam shaping and modulation functions, realizing parallel emission, and ensuring the uniformity of the emitted beam spot on the image plane. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a metasurface lens that shapes Gaussian light into parallel uniform light, provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a microstructure unit of a periodically arranged metasurface lens in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the laser shaping system in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the normalized phase abrupt change and microstructure transmittance of the columnar microstructure unit of the metasurface lens in the first optical system of the present invention at different diameters.

[0038] Figure 5(a) is a two-dimensional irradiance distribution diagram of the circular uniform parallel light emitted after the laser is shaped by the first optical system in Embodiment 1 of the present invention.

[0039] Figure 5(b) is a one-dimensional irradiance distribution diagram of the circular uniform parallel light emitted after the laser is shaped by the first optical system in Embodiment 1 of the present invention.

[0040] Figure 6 This is a schematic diagram of the normalized phase abrupt change and microstructure transmittance of the columnar microstructure unit of the metasurface lens in the second optical system of the present invention at different diameters.

[0041] Figure 7(a) is a two-dimensional irradiance distribution diagram of the circular uniform parallel light emitted after the laser is shaped by the second optical system in Embodiment 1 of the present invention.

[0042] Figure 7(b) is a one-dimensional irradiance distribution diagram of the circular uniform parallel light emitted after the laser is shaped by the second optical system in Embodiment 1 of the present invention.

[0043] Figure 8(a) is a two-dimensional irradiance distribution diagram of the elliptical uniform parallel light emitted after the laser is shaped by the third optical system in Embodiment 1 of the present invention.

[0044] Figure 8(b) is a one-dimensional (major axis direction) irradiance distribution diagram of the elliptical uniform parallel light emitted after the laser is shaped by the third optical system in Embodiment 1 of the present invention.

[0045] Figure 8(c) is a one-dimensional (short axis direction) irradiance distribution diagram of the elliptical uniform parallel light emitted after the laser is shaped by the third optical system in Embodiment 1 of the present invention.

[0046] In all the figures and tables, the same reference numerals are used to denote the same elements or structures, wherein 1, laser emitter, 2, metasurface lens, 201, first metasurface, 202, second metasurface, 203, dielectric substrate layer, and 3, image plane. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0048] Metasurface lenses are special optical elements that utilize arrays of microstructures on their surfaces to achieve optical functions, exhibiting excellent optical control capabilities. The artificially designed and arranged periodic microstructures on their surfaces can precisely adjust the phase and amplitude distribution of a light beam, enabling functions such as beam focusing, splitting, deflection, and modulation. They are characterized by their compactness, flexibility, and high efficiency.

[0049] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0050] Example 1

[0051] This invention provides a metasurface lens for shaping Gaussian beams into parallel, uniform light, such as... Figure 1 As shown, the metasurface lens includes: a dielectric substrate layer and a metasurface microstructure.

[0052] The metasurface lens is used to shape the incident Gaussian beam into an outgoing beam that is parallel to the optical axis and uniformly distributed within the target range.

[0053] Figure 2 This is a schematic diagram of a microstructure unit of a metasurface lens arranged periodically in an embodiment of the present invention. The metasurface microstructure is composed of multiple columnar microstructure units arranged in a periodic array of tetragonal or hexagonal lattices. The distribution of the columnar microstructure units is matched with the incident beam, so that the outgoing beam is parallel to the optical axis and uniformly distributed within the target range. Figure 3 This is a schematic diagram of the structure of the laser shaping system in an embodiment of the present invention. The laser shaping system includes: a laser emitter, a metasurface lens, and an image plane.

[0054] The calculation standard for the uniformity of the light spot is as follows: For a light spot with a centrally symmetrical distribution, the illuminance uniformity within the range [-R, R] is... in E0 is the average illuminance value within the light spot, and E0 is the peak illuminance value. A larger u indicates that the area of ​​illuminance within the light spot is closer to the area of ​​the illuminance peak within the light spot, and the better the uniformity of illuminance. Obviously, u < 1. Therefore, the size of u can be used to measure the quality of illuminance uniformity within the light spot.

[0055] This invention provides a metasurface lens that shapes a Gaussian beam into parallel and uniform light. By using metasurface elements to control the incident light, the incident light is shaped, ultimately ensuring that the outgoing beam is parallel to the optical axis and uniformly distributed within the target range.

[0056] The metasurface lens has antireflection and anti-reflection coatings for the target wavelength on both its front and back sides. The metasurface of the metasurface lens is composed of columnar microstructure units arranged in a periodic array of tetragonal or hexagonal lattices, forming a planar structure. The height of each columnar microstructure unit is uniform and within the order of the wavelength of the incident laser emitted by the laser. The diameter of each columnar microstructure unit is within the order of subwavelength. The refractive index of the material of the columnar microstructure unit is greater than or equal to the refractive index of the material of the dielectric substrate. The specific combination of the materials is related to the target wavelength. For example, the columnar structure unit material is silicon and titanium dioxide, and the dielectric substrate material is silicon and silicon dioxide.

[0057] Based on the operating wavelength of the laser emitter, the beam waist diameter of the emitted laser, and the shape and size of the target spot, the irradiance distribution of the incident Gaussian beam and the irradiance distribution of the emitted beam spot on the image plane are discretized and matched. The emitted beam is discretized to make it exit parallel to the optical axis. Furthermore, the normalized radius R and phase distribution polynomial coefficients of the metasurface lens are optimized using a personalized optimization function algorithm and damped least squares method in simulation software, thereby determining the arrangement of the metasurface microstructure periodic array.

[0058] Phase distribution of the periodic array of columnar microstructure units Satisfy the following expression:

[0059]

[0060]

[0061] in, and Let ρ be the phase distribution of the first metasurface and the second metasurface, respectively, where ρ is the radial coordinate of the metasurface, R is the normalized radius, and n is the maximum number of terms in the phase distribution.

[0062] A i (i = 1, 2, 3, ..., n) are the coefficients of the quadratic, quartic, hexatic...2n-th degree terms of the phase distribution parameters of the columnar microstructure unit of the first metasurface, B i (i = 1, 2, 3, ..., n) are the coefficients of the quadratic, quartic, hexatic, ..., 2nth order terms of the phase distribution parameters of the columnar microstructure unit of the second metasurface. The phase distribution of the metasurface microstructure adopts the form of a high-order even polynomial, which expands the optimization solution space and increases the number of optimization parameters to achieve the design goal.

[0063] Optionally, the diameter, period, height, and arrangement of the columnar microstructure units are determined according to the corresponding phase distribution.

[0064] The size and phase distribution of columnar microstructure units have a corresponding relationship. Once the phase distribution is determined, the diameter of the columnar microstructure unit can be obtained based on the corresponding relationship.

[0065] Using the finite-difference time-domain algorithm and rigorous coupled-wave analysis, the dimensional parameters of the columnar microstructure units on a metasurface are simulated to determine the correspondence between the height, period, and diameter of the microstructure and the resulting phase abrupt change. Based on the correspondence between the microstructure diameter and the resulting phase abrupt change, and combined with the phase distribution of the hexagonal lattice periodic array of the metasurface, the diameter of the microstructure at the corresponding position of the metasurface lens is determined. The period, height, and diameter of the columnar microstructure units all affect the phase delay and even the transmittance of the metasurface microstructure. In the simulation process, a suitable period and height range is selected according to the target wavelength. Then, the relationship between the diameter and phase delay of the columnar microstructure units within the selected height and period range is calculated through simulation. This set of period and height is selected while ensuring high transmittance.

[0066] In one specific embodiment, the incident laser wavelength is 10.6 micrometers, the beam waist diameter is 3.5 mm, the microstructure of the metasurface lens is a cylindrical structure with a period P of 3 μm, a height H of 12 μm, and a diameter D ranging from 2 to 2.8 μm; based on the phase-dispersion distribution, the metasurface microstructures that are near the same dispersion level and can cover the entire 2π phase are identified as the required microstructure units. Figure 4 This diagram illustrates the normalized phase abrupt change and microstructure transmittance of the columnar microstructure unit of the metasurface lens in the first optical system of Embodiment 1 of the present invention at different diameters. Within this diameter range and at a fixed height, microstructure units with higher transmittance and more uniform dispersion are preferred.

[0067] More specifically, the specific parameter values ​​in the optical system provided in the embodiments of the present invention are shown in Tables 1 and 2.

[0068] Table 1. Parameters of the First Metasurface Lens

[0069]

[0070] Table 2 Optical structure parameters of the first optical system

[0071]

[0072]

[0073] Using the uniformity definition formula, the shaping effect of the optical system provided in this embodiment for a 10.6-micron wavelength laser is shown in Table 3. The angle between the emitted beam and the optical axis is less than 3.41 × 10⁻⁶. -4The beam parallelism is good, the target spot is circular with a spot radius of 1 mm, the irradiance distribution of the spot on the image plane is shown in Figure 5(a), and the radial irradiance distribution of the spot on the image plane is shown in Figure 5(b).

[0074] Table 3 Uniformity parameters of the first optical system

[0075]

[0076] In another specific embodiment, the incident laser wavelength is 1.31 micrometers, the beam waist diameter is 3.5 mm, the microstructure of the metasurface lens is a cylindrical structure with a period P of 300 nm, a height H of 1300 nm, and a diameter D ranging from 0 to 280 nm; based on the phase-dispersion distribution, the metasurface microstructure that is near the same dispersion level and can cover the entire 2π phase is identified as the required microstructure unit. Figure 6 This diagram illustrates the normalized phase abrupt change and microstructure transmittance of the columnar microstructure unit of the metasurface lens in the second optical system of Embodiment 1 of the present invention at different diameters. Within this diameter range and at a fixed height, microstructure units with higher transmittance and more uniform dispersion are preferred.

[0077] In another embodiment, the specific parameter values ​​are shown in Tables 4 and 5.

[0078] Table 4. Parameters of the Second Metasurface Lens

[0079]

[0080]

[0081] Table 5 Optical structure parameters of the second optical system

[0082]

[0083] Using the uniformity definition formula, the shaping effect of the optical system provided in this embodiment for a 1.31-micron wavelength laser is shown in Table 6. The angle between the emitted beam and the optical axis is less than 3.51 × 10⁻⁶. -4 The beam parallelism is good, the target spot is circular with a spot radius of 1 mm, the irradiance distribution of the spot on the image plane is shown in Figure 7(a), and the radial irradiance distribution of the spot on the image plane is shown in Figure 7(b).

[0084] Table 6 Uniformity parameters of the second optical system

[0085]

[0086] The above embodiments analyze double-sided metasurface lenses with different operating wavelengths and materials, demonstrating that this optical system structure is suitable for shaping various lasers with different operating wavelengths. Furthermore, changing the distance between the double-sided metasurface lens and the image plane does not significantly alter the calculated uniformity.

[0087] In another embodiment, the incident laser wavelength is 10.6 micrometers, the beam waist diameter is 3.5 mm, and the metasurface lens microstructure is cylindrical with a period P of 3 μm, a height H of 12 μm, and a diameter D ranging from 2 to 2.8 μm. The cylindrical lens is positioned 5 mm away from the metasurface lens along the optical axis. Based on the phase-dispersion distribution, the metasurface microstructures that are near the same dispersion level and can cover the entire 2π phase are identified as the desired microstructure units. Within this diameter range and fixed height, microstructure units with high transmittance and uniform dispersion are preferred.

[0088] Specific parameter values ​​are shown in Tables 7 and 8.

[0089] Table 7 Parameters of the Third Metasurface Lens

[0090]

[0091] Table 8 Optical Structure Parameters of the Third Optical System

[0092]

[0093]

[0094] Using the uniformity definition formula, the shaping effect of the optical system provided in this embodiment for a 10.6-micron wavelength laser is shown in Table 9. The angle between the emitted beam and the optical axis is less than 2.6 × 10⁻⁶. -3 The beam parallelism is good, and the target spot is elliptical with a major axis of 1.3 mm and a minor axis of 1 mm. The irradiance distribution of the spot on the image plane is shown in Figure 8(a). The irradiance distribution of the spot along the X and Y directions on the image plane is shown in Figure 8(a). Figure 8(b) , 8(c) As shown.

[0095] Table 9 Uniformity parameters of the third optical system

[0096]

[0097] The above embodiments, analyzing the combination of a double-sided metasurface lens and a refractive lens, demonstrate that this optical system structure is suitable for shaping different target light spots. Furthermore, changing the distance between the cylindrical lens and the image plane does not significantly alter the calculated uniformity.

[0098] This invention provides a metasurface lens for shaping a Gaussian beam into parallel and uniform light. It only uses a metasurface lens, and by leveraging the precise control of the incident light by the metasurface lens, it achieves laser shaping, ensuring that the outgoing light is parallel and has high uniformity. This design only uses a metasurface lens, the optical system structure is simple, and it has a wide range of applications, suitable for laser shaping of various lasers.

[0099] Example 2

[0100] The present invention also provides a method for designing a metasurface lens for shaping a Gaussian beam into parallel uniform light as described in any one of Embodiment 1, comprising:

[0101] S1. Calculate the phase distribution of the metasurface lens based on the operating wavelength of the laser emitter, the beam waist diameter of the emitted laser, and the shape and size of the target spot.

[0102] S2, calculate the parameters of the outgoing beam formed after the laser is shaped by the metasurface lens based on the current phase distribution of the metasurface lens. The parameters of the outgoing beam include the shape, size and uniformity of the light spot on the image plane.

[0103] S3. If the shape, size, and uniformity of the emitted beam spot on the image plane meet the design requirements, proceed to S5; otherwise, based on the working wavelength of the laser emitter and the beam waist diameter of the emitted laser, optimize and update the phase distribution parameters of the metasurface lens using the damped least squares method and a custom optimization algorithm.

[0104] S4, bring in the updated phase distribution and repeat S2-S3 until the shape, size and uniformity of the outgoing beam spot on the image plane obtained in S2 meet the design requirements;

[0105] S5, Design the size and arrangement of multiple columnar microstructure units in the metasurface lens according to the current phase distribution of the metasurface lens;

[0106] S6. The metasurface lens is prepared based on the data in S5 to construct a laser shaping optical system.

[0107] Optionally, S5 includes:

[0108] The target phase distribution of the metasurface lens is fitted with coefficients so that the discrete points of the fitted phase distribution correspond one-to-one with the columnar microstructure units of the metasurface lens.

[0109] Simulation was used to obtain the correspondence between the size, phase distribution, and transmittance of the columnar microstructure unit in the metasurface lens;

[0110] The corresponding relationship is queried based on the phase distribution after coefficient fitting to obtain the size and arrangement of multiple columnar microstructure units.

[0111] Optionally, the simulation to obtain the correspondence between the size and phase distribution of the columnar microstructure units in the metasurface lens includes:

[0112] Based on the finite-difference time-domain algorithm and rigorous coupled-wave analysis method, the dimensional parameters of the columnar microstructure unit of the metasurface lens are simulated to determine the correspondence between the height, period, and diameter of the columnar microstructure unit and the phase distribution and transmittance.

[0113] In the calculation of S1, the optimization function and the built-in optimization algorithm in the simulation software were used. The built-in optimization algorithm in the simulation software is the damped least squares method.

[0114] In the simulation software, a customized optimization function divides the incident and outgoing light into n concentric circles based on different field of view angles. At the same field of view angle, the concentric circles formed by the incident and outgoing light rays correspond one-to-one. The actual radial coordinates of the corresponding outgoing light rays on the image plane are calculated based on the irradiance distribution of the incident and outgoing light rays. Simultaneously, the outgoing light is discretized to ensure it exits parallel to the optical axis. Then, the phase distribution of the metasurface microstructure is calculated based on the above relationships.

[0115] The metasurface lens designed and manufactured according to the method for shaping a Gaussian beam into parallel uniform light provided in this embodiment has the corresponding beneficial effects as described in the above embodiment.

[0116] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing a metasurface lens that shapes Gaussian light into parallel, uniform light, characterized in that, Metasurface lenses consist of a dielectric substrate layer and metasurface microstructures; The metasurface microstructure includes a first metasurface and a second metasurface respectively distributed on both sides of the dielectric substrate layer. Each metasurface includes multiple columnar microstructure units, which are arranged in a periodic array of tetragonal or hexagonal lattices, and each columnar microstructure unit has the same height. The distribution of the multiple columnar microstructure units is matched with the incident beam, so that the shaped incident beam forms an outgoing beam that is parallel to the optical axis and uniformly distributed within the target range. Design methods include: S1. Calculate the phase distribution of the metasurface lens based on the operating wavelength and beam waist diameter of the incident beam, as well as the shape and size of the target spot. S2, calculate the parameters of the outgoing beam formed after the incident beam is shaped by the metasurface lens based on the current phase distribution of the metasurface lens. The parameters of the outgoing beam include the shape, size and uniformity of the light spot on the image plane. S3, if the shape, size, and uniformity of the emitted beam spot on the image plane meet the design requirements, proceed to S5; otherwise, based on the working wavelength and beam waist diameter of the incident beam, optimize and update the phase distribution parameters of the metasurface lens using the damped least squares method and a custom optimization algorithm; the custom optimization algorithm includes: dividing the incident beam and the emitted beam into multiple concentric circles according to different field of view angles, with the concentric circles formed by the incident beam and the emitted beam corresponding one-to-one under the same field of view angle; calculating the actual radial coordinates of the corresponding emitted beam on the image plane based on the irradiance distribution of the incident beam and the irradiance distribution of the emitted beam; and simultaneously discretizing the emitted beam to make it emitted parallel to the optical axis. S4, bring in the updated phase distribution and repeat S2-S3 until the shape, size and uniformity of the outgoing beam spot on the image plane obtained in S2 meet the design requirements; S5, Design the size and arrangement of multiple columnar microstructure units in the metasurface lens according to the current phase distribution of the metasurface lens; S6. The metasurface lens is prepared based on the data in S5 to construct a laser shaping optical system.

2. The design method as described in claim 1, characterized in that, The height of the columnar microstructure unit is on the order of the wavelength of the incident light beam, and the diameter is on the order of the subwavelength; the phase is distributed according to a periodic array, and the phase distribution of the first metasurface is... Phase distribution of the second metasurface They respectively satisfy the following expressions: in, For the radial coordinates of the metasurface lens, For the normalized radius, The maximum number of terms in the phase distribution. and For polynomial coefficients, .

3. The design method as described in claim 1, characterized in that, The metasurface lens is coated with anti-reflective and anti-reflective coatings on both sides.

4. The design method as described in claim 1, characterized in that, The refractive index of the columnar microstructure unit is greater than or equal to the refractive index of the dielectric substrate layer.

5. The design method as described in claim 1, characterized in that, S5 includes: The target phase distribution of the metasurface lens is fitted with coefficients so that the discrete points of the fitted phase distribution correspond one-to-one with the columnar microstructure units of the metasurface lens. Simulation was used to obtain the correspondence between the size, phase distribution, and transmittance of the columnar microstructure unit in the metasurface lens; The corresponding relationship is queried based on the phase distribution after coefficient fitting to obtain the size and arrangement of multiple columnar microstructure units.

6. The design method as described in claim 5, characterized in that, The simulation obtains the correspondence between the size, phase distribution, and transmittance of the columnar microstructure units in the metasurface lens, including: Based on the finite-difference time-domain algorithm and rigorous coupled-wave analysis method, the dimensional parameters of the columnar microstructure unit of the metasurface lens are simulated to determine the correspondence between the height, period, and diameter of the columnar microstructure unit and the phase distribution and transmittance.

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