Phase regulation and control beam shaping equipment

Abstract

The invention relates to the technical field of laser additive manufacturing, in particular to phase regulation and control beam shaping equipment which comprises a laser transmitter, a beam shaping device and a forming device. The beam shaping device comprises two metasurface structures and a moving assembly, each metasurface structure comprises a dielectric substrate and dielectric nano-columns, and the spacing distance d between every two adjacent dielectric nano-columns needs to meet the following condition: # imgabs0 # is based on the phase range of laser beams emitted by the laser emitter, acquiring an included angle theta (x, y) between a long axis of each dielectric nano-column and a first coordinate axis in a plane support coordinate system; the moving assembly is connected with the at least one metasurface structure and drives the at least one metasurface structure to move in the light path direction perpendicular to the laser light velocity. Therefore, the problems that the shaping efficiency is insufficient and the adjustment is not flexible enough when the Gaussian beam and the flat-topped beam are converted in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser additive manufacturing, and in particular to a phase-controlled beam shaping device. Background Art

[0002] Thin-walled metal parts refer to structural parts with high precision and relatively small thickness. Among various parts such as shell-shaped parts, ring parts and shaft parts, parts with a ratio of wall thickness to inner diameter and radius of curvature (or profile size) less than 1:20 are generally called thin-walled parts. Thin-walled parts are widely used in aerospace, electronic manufacturing and other industries due to their advantages such as light weight, high precision and compact structure. The traditional processing methods for thin-walled parts mainly include forging, casting and machining, but these methods are difficult to form thin walls with complex structures and cannot meet the requirements of dimensional accuracy of thin-walled parts. Laser additive manufacturing is an advanced manufacturing technology that uses laser as a heat source to melt metal materials and prepare metal parts by layer-by-layer stacking. It can realize mold-free, rapid and fully dense forming of high-performance complex metal structure metal parts. Using laser additive manufacturing for the manufacture of thin-walled parts can realize the forming of complex parts, and the material utilization rate is higher. At the same time, the defects of thin-walled parts formed by laser additive manufacturing are relatively few.

[0003] At present, the spatial intensity distribution of laser light sources used for metal printing is mostly Gaussian, that is, Gaussian beam. In practical applications, the intensity of Gaussian beam is too concentrated in the center. When forming thin-walled parts with relatively small wall thickness, the unevenly distributed beam can easily cause element segregation of thin-walled parts, which in turn causes uneven internal tissue distribution and affects the mechanical properties of the final product. The flat-top beam can evenly disperse the intensity throughout the spot size, which can greatly improve the uniformity of energy distribution. However, the laser emitted by the laser generator is mainly Gaussian, so it is necessary to be able to convert the Gaussian beam into a flat-top beam.

[0004] In the prior art, there are many methods for converting Gaussian beams into flat-top beams, but all of them have some disadvantages. In the early aperture method, a Gaussian beam can be passed through an aperture smaller than its diameter to obtain a beam with uniform light intensity distribution, but the beam energy loss is serious; in recent years, the use of liquid crystal spatial modulators to shape Gaussian beams has received widespread attention, but because the beam shaping effect is affected by the size and gap of liquid crystal pixels, and the liquid crystal damage threshold is low, it has great limitations in high-power laser beam shaping. Therefore, a new beam conversion technology solution that can overcome the above problems is needed. Summary of the invention

[0005] In order to solve the problems of insufficient shaping efficiency and inflexible adjustment when converting between a Gaussian beam and a flat-top beam in the prior art, the present invention provides a phase-controlled beam shaping device, comprising: a laser emitter, a beam shaping device and a shaping device; the laser emitter can emit a laser beam, and the spatial intensity distribution of the laser beam is a Gaussian distribution; the beam shaping device and the shaping device are sequentially arranged along the optical path of the laser beam, the shaping device can stack alloy powder layers layer by layer, and the laser beam can be irradiated onto the alloy powder layer through the beam shaping device; the beam shaping device comprises two meta-structure surface structures and a moving component, the meta-structure surface structure comprises a dielectric substrate and a dielectric nanocolumn, the dielectric substrate is a flat sheet structure, the dielectric substrate is arranged perpendicular to the optical path direction of the laser beam, and the dielectric nanocolumn is an elliptical column and extends in a direction perpendicular to the dielectric substrate; a plane rectangular coordinate system is arranged at the center of the dielectric substrate, a plurality of dielectric nanocolumns are distributed in a square lattice array, and are arranged on the dielectric substrate according to the plane rectangular coordinate system, and the dielectric nanocolumns on the two meta-structure surface structures are arranged relative to each other; the spacing distance d between two adjacently arranged dielectric nanocolumns must satisfy: Where R(z) is the radius of curvature of the incident light along its irradiation direction; λ is the wavelength of the incident light; ω0 is the beam waist radius of the incident light; f max is the maximum spatial frequency of the phase gradient of the incident light, n eff is the effective refractive index of the beam shaping device, θ max is the maximum deflection angle of the incident light beam; the dielectric nanocolumn adopts geometric phase control, and based on the phase range of the laser beam emitted by the laser emitter, the angle θ(x, y) between the long axis of each dielectric nanocolumn and the first coordinate axis in the plane bracket coordinate system is obtained, where (x, y) is the coordinate position of the dielectric nanocolumn; the moving component is connected to at least one metasurface structure and drives it to move along the optical path direction perpendicular to the laser light speed.

[0006] In some embodiments, the angle between the long axis of the dielectric nanorod on the first metasurface and the first coordinate axis in the plane support coordinate system is The angle between the long axis of the dielectric nanorod on the second metasurface and the second coordinate axis in the plane support coordinate system in, is the phase of the first metasurface, is the phase of the second metasurface.

[0007] In some embodiments, the dielectric substrate is made of quartz material, and the dielectric nanorods are made of titanium dioxide material.

[0008] In some embodiments, the height of the dielectric nanorod is 450-550 nm, the cross-section of the dielectric nanorod has a major axis length of 200-230 nm, and a minor axis length of 100-110 nm.

[0009] In some embodiments, the dielectric nanorods are arranged with a periodicity of 200-300 nm.

[0010] In some embodiments, the distance between two metasurface structures is 600-1000 nm.

[0011] In some embodiments, along the direction of the laser light path emitted by the laser transmitter, a half-wave plate, a polarizer and a variable-power beam expander are further arranged after the beam shaping device.

[0012] In some embodiments, the forming device includes a galvanometer system, a field lens, and a work platform; the galvanometer system is used to focus the incident laser, and irradiate the alloy powder layer arranged on the work platform after passing through the field lens.

[0013] In some embodiments, the working platform includes a supporting platform, a limiting frame and a powder distribution device. The supporting platform matches the limiting frame. The limiting frame can extend along the direction of the laser light path irradiated to the working platform. The supporting platform can move along the extension direction of the limiting frame. The powder distribution device can stack the alloy powder layers on the supporting platform in sequence according to the set thickness.

[0014] In some embodiments, the thickness of the alloy powder layer is 25-35 μm, and the material is a regular spherical AlSi 10 Mg powder, wherein the Al content is 89.75at.%, the Si content is 9.7at.%, the Fe content is 0.12at.%, the Mg content is 0.38at.%, and the Mn content is 0.01at.%; AlSi 10 The particle size distribution of Mg powder is 15-53 μm.

[0015] In order to solve the problems of insufficient shaping efficiency and inflexible adjustment when converting between Gaussian beam and flat-top beam in the prior art, the present invention has the following advantages:

[0016] In the above technical solution, a beam shaping device is formed by two relatively arranged metasurface structures. Through the above structural setting, when the Gaussian beam emitted by the laser emitter passes through the above beam shaping device, the total phase formed by the two metasurface structures can be superimposed on the Gaussian beam, so that the laser beam with Gaussian distribution can be converted into a flat-top beam after passing through the beam shaping device. Even if the laser beam is emitted by the same laser emitter, its phase distribution may change within a certain range. In order to cope with this change, the two metasurface structures are driven by a moving component, so that they can move along the optical path direction perpendicular to the laser light speed, so that the two metasurface structures are misaligned, and the total phase of the light speed shaping device composed of the two metasurface structures is adjusted within a certain range, so as to ensure that the outgoing light is a flat-top beam. The above adjustment process has a simple structure and is easy to implement. It can be quickly adjusted according to the incident laser phase distribution, so that the outgoing laser beam can quickly switch between two different spatial intensity distribution modes. In the production process, different types of beams can be used for forming processing at different positions of the same part. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a phase-controlled beam shaping device according to an embodiment is shown;

[0018] Figure 2 A schematic diagram showing a laser beam passing through a beam shaping device according to an embodiment;

[0019] Figure 3 A schematic structural diagram of a metasurface structure according to an embodiment is shown;

[0020] Figure 4 A locally enlarged structural schematic diagram of a metasurface structure of an embodiment is shown.

[0021] Figure numerals: 1-laser beam; 10-laser emitter; 20-beam shaping device; 21-first metasurface structure; 22-second metasurface structure; 23-dielectric substrate; 24-dielectric nanorod; 30-half-wave plate; 40-polarizer; 50-variable beam expander; 60-first total reflection mirror; 70-second total reflection mirror; 80-galvanometer system; 90-field mirror; 100-working platform. DETAILED DESCRIPTION

[0022] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0023] As used herein, the term "including" and its variants are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like is based on the orientation or position relationship shown in the accompanying drawings. These terms are mainly for better describing the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to being used to indicate an orientation or position relationship, some of the above terms may also be used to indicate other meanings, such as the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances. In addition, the terms "install", "set", "provided with", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0024] This embodiment discloses a phase-controlled beam shaping device, such as Figure 1-4As shown, it may include: a laser emitter 10, a beam shaping device 20 and a forming device; the laser emitter 10 can emit a laser beam 1, and the spatial intensity distribution of the laser beam 1 is Gaussian distribution; the beam shaping device 20 and the forming device are sequentially arranged along the optical path of the laser beam 1, and the forming device can stack the alloy powder layer layer by layer, and the laser beam 1 can be irradiated onto the alloy powder layer through the beam shaping device 20; the beam shaping device 20 includes two meta-structure surface structures and a moving component, the meta-structure surface structure includes a dielectric substrate 23 and a dielectric nano-column 24, the dielectric substrate 23 is a flat sheet structure, the dielectric substrate 23 is arranged perpendicular to the optical path direction of the laser beam 1, and the dielectric nano-column 24 is an elliptical column and extends in a direction perpendicular to the dielectric substrate 23; a plane rectangular coordinate system is set at the center of the dielectric substrate 23, a plurality of dielectric nano-columns 24 are distributed in a square lattice array, and are arranged on the dielectric substrate 23 according to the plane rectangular coordinate system, and the dielectric nano-columns 24 on the two meta-structure surface structures are arranged oppositely; the spacing distance d between two adjacently arranged dielectric nano-columns 24 must satisfy: d≤ Where R(z) is the radius of curvature of the incident light along its irradiation direction; λ is the wavelength of the incident light; ω0 is the beam waist radius of the incident light; f max is the maximum spatial frequency of the phase gradient of the incident light, n eff is the effective refractive index of the beam shaping device 20, θ max The dielectric nanocolumn 24 is geometrically phase-controlled, and based on the phase range of the laser beam 1 emitted by the laser emitter 10, the angle θ(x, y) between the long axis of each dielectric nanocolumn 24 and the first coordinate axis in the plane support coordinate system is obtained, where (x, y) is the coordinate position of the dielectric nanocolumn 24; the moving component is connected to at least one metasurface structure and drives it to move along the optical path direction perpendicular to the laser light speed.

[0025] In the above technical solution, a beam shaping device 20 is formed by two relatively arranged metasurface structures. Through the above structural setting, when the Gaussian beam emitted by the laser emitter 10 passes through the above beam shaping device 20, the total phase formed by the two metasurface structures can be superimposed on the Gaussian beam, so that the laser beam 1 with Gaussian distribution can be converted into a flat-top beam after passing through the beam shaping device 20. Even if the laser beam 1 emitted by the same laser emitter 10 has a phase distribution that may change within a certain range, in order to cope with such changes, the two metasurface structures are driven by a moving component, so that they can move along the optical path direction perpendicular to the laser light speed, so that the two metasurface structures are misaligned, and the total phase of the light speed shaping device composed of the two metasurface structures is adjusted within a certain range, so as to ensure that the outgoing light is a flat-top beam. The above adjustment process has a simple structure and is easy to implement. It can be quickly adjusted according to the incident laser phase distribution, so that the outgoing laser beam 1 can quickly switch between two different spatial intensity distribution modes. In the production process, different types of beams can be used for forming processing at different positions of the same part.

[0026] It should be noted that the dielectric nanocolumns 24 have anisotropic characteristics. Specifically, anisotropy refers to the different relative angles between the long axes of the nanocolumns, while the size, shape, length and other parameters of the nanocolumns are the same. The offset angle is set to accurately control the propagation path, intensity distribution and diffraction behavior of the light beam to achieve the desired beam shaping effect. For the shaping of a Gaussian beam into a flat-top beam in laser additive manufacturing, it can be arranged in a way that the long axis of the cross section of the nanocolumn is a gradient angle, that is, the angle of the nanocolumn gradually changes along the radial or circumferential direction of the beam, usually increasing from the center to the edge. This method can accurately control the bending of the beam as needed to ensure the uniformity of the beam and the stability of the intensity distribution.

[0027] In order to accurately achieve the required phase distribution, the nanorod arrangement period needs to meet the sampling requirements of the phase gradient of the shaped beam. According to the Nyquist sampling theorem and the phase gradient sampling limit theorem, the spacing between two adjacent dielectric nanorods 24 along the coordinate axis is d, which should satisfy: d≤ Among them, f max is the maximum spatial frequency of the phase gradient of the incident light, n eff is the effective refractive index of the beam shaping device, θ max is the maximum deflection angle of the incident light beam.

[0028] The incident Gaussian beam should irradiate the center of the metasurface structure, that is, the intersection of the coordinate axes of the plane rectangular coordinate system set on the dielectric substrate 23. At this time, the phase distribution of the Gaussian beam is It can be expressed as:

[0029]

[0030] Where r represents the radial distance from the center of the beam to any point; R(z) is the radius of curvature of the Gaussian beam in the z direction (the direction perpendicular to the dielectric substrate 23); ζ(z) is the valley-to-tower phase of the Gaussian beam, which is usually related to the beam waist and wavelength. The phase gradient / phase change rate of the Gaussian beam with spatial position is: Maximum phase gradient / rate of phase change with spatial position |f Gauss | max Occurs at the beam waist r = ω0, that is, In summary, the final arrangement period d should satisfy:

[0031] It should be noted that in the above content, the coordinate system of the dielectric nanocolumns 24 provided on the metasurface structure is consistent with the coordinate system of the light beam. The light beam is incident vertically on the metasurface in the forward direction, and the origin of the coordinate is the exact center of the light beam. When calculating, the light beam can be converted into a polar coordinate system to make the expression concise, and for a symmetrical light beam, only the radial coordinate r is needed to represent it, and the formula is simpler. The Gutta-Pertuan phase and curvature radius of a Gaussian beam can be directly calculated using the wavelength and the beam waist radius. The beam waist radius is one of the important parameters that describe the characteristics of a Gaussian beam. It defines the time at which the light intensity of the light beam decays to a maximum value of 1 / e at the focus (or the narrowest position). 2 The radius at is the size description of the narrowest cross section of the Gaussian beam. The above formula shows that the spacing distance d between two adjacent dielectric nanorods 24 along the coordinate axis is designed according to the beam waist radius and wavelength of the light beam. As long as these two parameters of the incident light do not change, there is no need to change the arrangement of the dielectric nanorods 24 on the metasurface structure.

[0032] Based on the metasurface set up by the above technical solution, the phase distribution of the two metasurface structures is:

[0033]

[0034] in, represents the phase distribution of the metasurface structure close to the laser emitter 10, represents the phase distribution of the metasurface structure on the side away from the laser emitter 10, (x, y) represents the position of the dielectric nanocolumn 24 on the dielectric substrate 23 according to the Cartesian coordinate system, θ(x, y) is the rotation angle of the nanocolumn at each (x, y) position, and a is the correction coefficient of the polarization direction of the incident light. When the incident light is left-handed circularly polarized light, a=1, and when the incident light is right-handed circularly polarized light, a=-1.

[0035] According to the phase distribution of the two metasurface structures, when one of the metasurface structures moves relative to the other metasurface structure, the movement can be expressed as follows: after a position change (Δx, Δy) occurs along the plane rectangular coordinate system set on the dielectric substrate 23 of one of the metasurfaces, the total output phase distribution of the beam shaping device 20 is It can be expressed as:

[0036]

[0037] in, represents the total output phase distribution of the beam shaping device 20, k x and k y is the wave vector component of light (related to spatial frequency). This formula shows that the total phase can be dynamically controlled by adjusting the displacement (Δx, Δy) of the metasurface distribution, therefore, when the laser emitter 10 that emits the laser causes a relatively small phase change in the emitted laser beam 1 due to factors such as aging, or when the laser emitter 10 is damaged and replaced, causing the emitted laser beam 1 to undergo a phase change within the design range, adjustment and correction can be performed by adjusting the beam shaping device 20.

[0038] The complex amplitude E of the output light field of the beam shaping device 20 is thus out (x,y) is:

[0039]

[0040] Among them, E in (x, y) is the complex amplitude of the input light field (incident Gaussian beam) of the beam shaping device 20, that is,

[0041] The intensity distribution of the output beam is then:

[0042]

[0043] Through the above calculation process, it can be seen that the intensity distribution of the output light beam can be dynamically controlled by adjusting the displacement (Δx, Δy) of the metasurface.

[0044] Specifically, in is the amplitude term, which is used to describe the intensity distribution of the Gaussian beam in the plane constructed by the dielectric substrate of the metasurface; -ikz is the propagation phase term, which is used to describe the propagation phase change of the beam along the z direction; is the spherical wavefront phase term, which describes the spherical curvature of the beam wavefront, and its curvature is determined by R(z); iζ(z) is the valley-to-tower phase term, which describes the additional phase delay accumulated by the beam during propagation; E0 is the peak amplitude of the incident Gaussian beam, ω0 is the waist radius of the incident Gaussian beam; k is the wave number, which is related to the wavelength, z is the propagation distance of the light wave, and kz is used to represent the phase accumulation in the direction of wave propagation. Every time the light wave propagates a distance z, a phase change of kz will be introduced. In physical terms, it describes the linear change of the phase of the wavefront with the propagation distance during the propagation of the light wave.

[0045] Regarding the distance setting between the two metasurface structures, during the process of the light beam propagating from the first metasurface structure 21 to the second metasurface structure 22, the light field will continue to accumulate phase, and the radius of curvature R(z) of the wavefront will change with the propagation distance z. Therefore: if the distance between the two metasurfaces is too large, the wavefront will change significantly, resulting in the phase design of the second layer no longer being applicable to the output light field of the first layer. The design of the distance between the two metasurfaces needs to ensure that the wavefront of the output light field of the first layer can still be effectively compensated by the second layer. Usually, the distance between the two metasurfaces is much smaller than R(z). For Gaussian beam shaping, it is recommended to set the distance between the two metasurfaces to be less than or equal to 0.01R(z), generally between 500nm-1000nm. Preferably, the spacing between the two metasurface structures is 600-1000nm.

[0046] As a specific embodiment, the angle between the long axis of the dielectric nanorod 24 on the first metasurface and the first coordinate axis in the plane support coordinate system is

[0047] The angle between the long axis of the dielectric nanorod 24 on the second metasurface and the second coordinate axis in the plane support coordinate system is

[0048] in, is the phase of the first metasurface, is the phase of the second metasurface.

[0049] In this embodiment, The calculation of can be performed as follows. First, based on the median value of the phase distribution range of the laser beam 1 emitted by the laser transmitter 10 Obtaining the total phase distribution of two metasurfaces

[0050]

[0051] The beam shaping device 20 includes a first metasurface structure 21 disposed near the laser emitter 10 and a second metasurface structure 22 disposed away from the laser emitter 10. The phase of the first metasurface structure 21 is Phase of the second metasurface structure 22

[0052] A Gaussian beam has an energy distribution that is strong at the center and weak at the edge, while a flat-top beam requires that the energy be evenly distributed across the entire cross section. By setting different α values, the two-layer metasurface has specific functions: the first metasurface structure 21 expands the edge energy of the beam through phase modulation to compensate for the attenuation of the edge. The second metasurface structure 22 performs laser phase compensation (similar to uniformizing energy distribution) so that the energy distribution after the two layers are superimposed tends to be uniform. The optimal α value can be determined by numerical simulation before beam shaping.

[0053] In some embodiments, the dielectric substrate 23 is made of quartz material, and the dielectric nanocolumns 24 are made of titanium dioxide material. In order to allow light to penetrate the metasurface structure, the dielectric substrate 23 is made of a light-transmitting quartz material. The quartz material has very good transparency, which enables it to effectively transmit the laser beam 1 without significant absorption or scattering of the beam; quartz has high thermal stability and low thermal expansion coefficient, which is crucial for high-energy-density laser beam transmission that may be involved in the laser additive manufacturing process. It can withstand high temperature changes and will not have much impact on beam transmission. Titanium dioxide has a high refractive index, which enables it to well change the propagation characteristics of light in the metasurface, and titanium dioxide has good machinability. Through nano-machining technology, titanium dioxide can be made into various forms. Such nano-scale processing to form microstructures can finely control the phase and propagation direction of the laser, thereby achieving efficient beam shaping.

[0054] As a specific implementation, the height of the dielectric nanorod 24 is 450-550nm, the major axis length of the cross section of the dielectric nanorod 24 is 200-230nm, and the minor axis length is 100-110nm. In addition, for the convenience of setting and streamlining the calculation process, the arrangement period d of the dielectric nanorod 24 is 200-300nm. As an embodiment: wavelength λ = 1064nm (1.064μm), material refractive index neff = 1.5 (usually neff is 1.5-2); wavefront curvature R (z = 1mm) = 8.08mm; beam waist radius ω0 = 30μm; maximum deflection angle θmax: assumed to be 30° (common beam shaping target); the calculation result is: d≤min (0.709μm, 45.63μm), the arrangement period d of the metasurface should not exceed 0.709μm to ensure that the Nyquist sampling condition is met and phase control errors are avoided. It is recommended to select a common micro-nano processing period, such as d = 300nm (0.3μm), which is a commonly used size for current optical nanostructure processing and can accurately meet the control requirements of high phase gradients.

[0055] As an embodiment: the light beam emitted by the laser emitter 10 is a Gaussian light beam, the laser emitter 10 used is a Nd:YAG fiber laser, the wavelength of the emitted Gaussian light beam λ=1064nm, the beam waist radius ω0 is 30μm, the metasurface array period d is 300nm, α is 0.6, and the distance between the metasurface and the laser emitter 10 is 1mm. It can be calculated that:

[0056]

[0057] According to the calculation formula of the geometric phase principle, the rotation angle between the long axis of the dielectric nanorods 24 on the two-layer metasurface structure and the Y axis of the coordinate system is:

[0058]

[0059] The angle is calculated based on the position coordinates of the dielectric nanorod 24: i =i·d,y j =j·d, Taking the dielectric nanorod 24 at the coordinate (0.6 μm, 0.9 μm) as an example, the angle of the dielectric nanorod 24 at this position on the first metasurface structure 21 is θ GEM1 =-1.15×10 3 rad, the angle of the dielectric nanorod 24 at this position on the second metasurface structure 22 is θ2 = -0.77×10 3 rad, where where z R is the Rayleigh length, and the calculation formula is

[0060] In some embodiments, Figure 1 As shown, along the direction of the laser light path emitted by the laser transmitter 10 , a half-wave plate 30 , a polarizer 40 and a variable-power beam expander 50 are further arranged after the beam shaping device 20 .

[0061] Specifically, the half-wave plate 30 is an optical element that can rotate the polarization direction of the light passing through, usually rotating the vibration direction of the linear polarized light by 90 degrees. Its function is to adjust the polarization state of the laser beam so that the laser can obtain the best transmission and processing effect when passing through other optical elements. The polarizer 40 is a device for controlling the polarization state of light. It can convert unpolarized light into linear polarized light, or control the direction and intensity of polarized light. In additive manufacturing, the polarizer 40 can be used to adjust the polarization characteristics of the laser to optimize the interaction between the laser and the material and improve the processing accuracy and effect. The variable-power beam expander 50 is used to adjust the diameter of the laser beam, expand the beam or focus the beam. In additive manufacturing equipment, it can be used to change the size of the laser beam so that the laser energy is evenly distributed in different areas, thereby improving the processing quality and efficiency. By adjusting the magnification of the beam expander, the system can adapt to the size and requirements of different workpieces.

[0062] As a specific implementation method, Figure 1 As shown, the forming device includes a galvanometer system 80, a field lens 90 and a working platform 100; the galvanometer system 80 is used to focus the incident laser, and after passing through the field lens 90, it is irradiated to the alloy powder layer set on the working platform 100. Among them, the field lens 90 is used to correct the beam offset to ensure that the focus point remains on the same plane, thereby improving the processing accuracy. At the same time, by cooperating with the galvanometer, the working area of ​​the laser scanning is expanded. In addition, the field lens 90 can also reduce the field curvature effect and ensure that the light spot is uniform within the working range. The galvanometer system 80 is usually composed of a pair of high-speed rotating lenses to quickly change the propagation direction of the laser beam. It can accurately control the scanning path of the laser and can be used to achieve precise beam positioning and dynamic control in additive manufacturing.

[0063] In addition, the working platform 100 includes a supporting platform, a limiting frame and a powder distribution device. The supporting platform matches the limiting frame. The limiting frame can extend along the direction of the laser light path irradiated to the working platform 100. The supporting platform can move along the extension direction of the limiting frame. The powder distribution device can sequentially stack the alloy powder layers on the supporting platform according to the set thickness. Using the above structure, the alloy powder can be matched with the laser light path, and the alloy powder can be sequentially stacked on the supporting platform according to the setting, thereby completing the processing. In addition, in the laser light path, in order to change the path of the laser, a total reflection lens can also be set, for example Figure 1As shown in FIG. 1 , a first total reflection mirror 60 and a second total reflection mirror 70 are provided to change the optical path, thereby facilitating the device setting.

[0064] Specifically, the setting of alloy powder will also affect the accuracy and effect of additive processing. The thickness of the alloy powder layer is 25-35μm, and the material is regular spherical AlSi 10 Mg powder, wherein the Al content is 89.75at.%, the Si content is 9.7at.%, the Fe content is 0.12at.%, the Mg content is 0.38at.%, and the Mn content is 0.01at.%; AlSi 10 The particle size of Mg powder is distributed in the range of 15-53μm. Specifically, the alloy powder material may also contain elements such as Mn, Pb, Ti, Zn, Sn, etc. These elements are impurities and the content is extremely low. The smaller particle size of the material powder can be quickly melted and then solidified under the action of the laser to complete the metal printing, and the smaller particle size of the material powder can effectively improve the printing accuracy of the product.

[0065] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present disclosure, and in actual applications, various changes may be made thereto in form and detail without departing from the scope of the present disclosure.

Claims

1. A phase-controlled beam shaping device, characterized in that: The phase-controlled beam shaping device comprises: Laser emitters, beam shapers, and forming devices; The laser emitter is capable of emitting a laser beam, and the spatial intensity distribution of the laser beam is Gaussian distribution; The beam shaping device and the forming device are sequentially arranged at intervals along the optical path of the laser beam, the forming device can stack alloy powder layers layer by layer, and the laser beam can be irradiated onto the alloy powder layer through the beam shaping device; The beam shaping device comprises two metasurface structures and a moving component, wherein the metasurface structure comprises a dielectric substrate and a dielectric nanocolumn, wherein the dielectric substrate is a flat sheet structure, and the dielectric substrate is arranged perpendicular to the optical path direction of the laser beam, and the dielectric nanocolumn is an elliptical column and extends in a direction perpendicular to the dielectric substrate; A plane rectangular coordinate system is set at the center of the dielectric substrate, a plurality of the dielectric nanocolumns are distributed in a square lattice array and are arranged on the dielectric substrate according to the plane rectangular coordinate system, and the dielectric nanocolumns on the two metasurface structures are arranged opposite to each other; The spacing distance d between two adjacent dielectric nanorods must satisfy: Where R(z) is the radius of curvature of the incident light along its irradiation direction; λ is the wavelength of the incident light; ω0 is the beam waist radius of the incident light; f max is the maximum spatial frequency of the phase gradient of the incident light, n eff is the effective refractive index of the beam shaping device, θ max is the maximum deflection angle of the incident light beam; The dielectric nanocolumn is geometrically phase controlled, and based on the phase range of the laser beam emitted by the laser emitter, an angle θ(x, y) between the long axis of each dielectric nanocolumn and the first coordinate axis in the plane support coordinate system is obtained, wherein (x, y) is the coordinate position of the dielectric nanocolumn; The moving component is connected to at least one of the metasurface structures and drives the metasurface structure to move along a light path direction perpendicular to the light speed of the laser.

2. A phase-controlled beam shaping device according to claim 1, characterized in that: The angle between the long axis of the dielectric nanorod on the first metasurface and the first coordinate axis in the plane support coordinate system The angle between the long axis of the dielectric nanorod on the second metasurface and the second coordinate axis in the plane support coordinate system is in, is the phase of the first metasurface, is the phase of the second metasurface.

3. The phase-controlled beam shaping device according to claim 1, characterized in that: The dielectric substrate is made of quartz material, and the dielectric nanocolumns are made of titanium dioxide material.

4. The phase-controlled beam shaping device according to claim 1, characterized in that: The height of the dielectric nanocolumn is 450-550 nm, the major axis length of the cross section of the dielectric nanocolumn is 200-230 nm, and the minor axis length is 100-110 nm.

5. The phase-controlled beam shaping device according to claim 4, characterized in that: The arrangement period of the dielectric nanorods is 200-300nm.

6. The phase-controlled beam shaping device according to claim 5, characterized in that: The distance between the two metasurface structures is 600-1000 nm.

7. The phase-controlled beam shaping device according to claim 1, characterized in that: Along the direction of the laser light path emitted by the laser transmitter, a half-wave plate, a polarizer and a variable-power beam expander are arranged behind the beam shaping device.

8. The phase-controlled beam shaping device according to claim 1, characterized in that: The molding device includes a galvanometer system, a field mirror and a working platform; The galvanometer system is used to focus the incident laser light, and irradiate the alloy powder layer arranged on the working platform after passing through the field lens.

9. The phase-controlled beam shaping device according to claim 8, characterized in that: The working platform includes a supporting platform, a limiting frame and a powder distribution device. The supporting platform matches the limiting frame. The limiting frame can extend along the direction of the laser light path irradiated to the working platform. The supporting platform can move along the extension direction of the limiting frame. The powder distribution device can stack the alloy powder layers on the supporting platform in sequence according to the set thickness.

10. The phase-controlled beam shaping device according to claim 1, characterized in that: The thickness of the alloy powder layer is 25-35 μm, and the material is regular spherical AlSi 10 Mg powder, wherein the Al content is 89.75 at.%, the Si content is 9.7 at.%, the Fe content is 0.12 at.%, the Mg content is 0.38 at.%, and the Mn content is 0.01 at.%; AlSi 10 The particle size distribution of Mg powder is 15-53 μm.

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