Design method and preparation method of high-threshold planar optical element and planar optical element

Abstract

The invention provides a high-threshold planar optical element design method, a high-threshold planar optical element preparation method and a planar optical element, and relates to the technical field of optical devices. The design method comprises the steps of determining thickness structures of two groups of regulation and control structures based on two wavelengths in target laser and target polarization conversion efficiency in combination with an optimization algorithm; determining spatial parameters of the two groups of regulation and control structures according to the two wavelengths and the phase regulation and control requirements corresponding to each wavelength; the design structure of the planar optical element comprises thickness structures and space parameters of two groups of regulation and control structures. The preparation method comprises the following steps: pretreating a base material; through a laser processing technology, based on a design structure, a matrix material is processed to obtain the planar optical element. According to the high-threshold planar optical element, two groups of regulation and control structures are processed and arranged in a base material; the first group of regulation and control structures are used for shaping the first wavelength in the target laser; and the second group of regulation and control structures are used for shaping the second wavelength in the target laser.

Description

Technical Field

[0001] The present application relates to the technical field of optical devices, and in particular to a design method and a preparation method of a high-threshold planar optical element and a planar optical element. Background Art

[0002] Laser welding is a technology that uses a high-power laser to melt the base metal to join homogeneous and heterogeneous materials. It boasts high precision, high efficiency, and high quality, making it an ideal precision joining process widely used in aerospace, marine, automotive, mechanical engineering, and power batteries. During the laser welding process, the laser-material interaction, including the base metal's absorption of laser energy and the subsequent melt pool evolution, directly determines the material's weld stability and mechanical properties, such as hardness and tensile strength.

[0003] By using dual-wavelength laser to replace the traditional single-wavelength laser and regulating its light field, the material's absorption effect on laser energy can be improved, the temperature field distribution of the molten pool can be regulated, the generation of defects such as holes, molten pool fluctuations and liquid splashing can be suppressed, and the microstructure of the weld area can be improved, thereby improving the material welding stability and the mechanical strength of the weldment.

[0004] In the field of dual-wavelength light field manipulation, in order to control different wavelengths separately, it is usually necessary to set up devices with complex structures and high processing difficulty to handle them. The current light field manipulation method based on optical path accumulation faces the problems of large size, difficult processing of complex structures, and limited control accuracy, which makes it difficult to meet the development trend of high-precision integrated optical systems. To solve this problem, in recent years, planar optical elements based on subwavelength structures can flexibly control multiple optical parameters such as phase, amplitude, and polarization, and simplify optical system design, providing a new path to solving the problem of integrated control of complex light fields.

[0005] However, current planar optical components are limited by the intrinsic threshold of the material and the structural light field coupling effect, and have a low damage threshold. They cannot withstand the action of high-power lasers in the kilowatt level and cannot meet the application requirements of high-power laser welding. Summary of the Invention

[0006] In view of this, the purpose of the embodiments of the present application is to provide a high-threshold planar optical element design method, a preparation method and a planar optical element, so as to improve the problem in the prior art that the planar optical elements cannot meet the application requirements of high-power laser welding.

[0007] In order to solve the above problems, in a first aspect, an embodiment of the present application provides a method for designing a high-threshold planar optical element, the method comprising: Based on the two wavelengths of the target laser and the target polarization conversion efficiency, the thickness structures of the two groups of control structures are determined in combination with the optimization algorithm; Determining spatial parameters of two groups of control structures according to the two wavelengths and the phase control requirements corresponding to each wavelength; Wherein, the design structure of the planar optical element includes the thickness structure and the spatial parameters of two groups of the regulating structures.

[0008] In the above implementation process, when designing the structure of a planar optical element based on the usage requirements of a high-power laser welding scenario, two sets of control structures can be set to process two wavelengths respectively. According to the two wavelengths of the target laser used in the application scenario and the required target polarization conversion efficiency, the thickness structure of the two sets of control structures is determined in combination with an optimization algorithm. And according to the two wavelengths and the phase control requirements corresponding to each wavelength, the spatial parameters of the two sets of control structures are determined to obtain a design structure of a planar optical element containing the thickness structure and spatial parameters of the two sets of control structures. The control structure can be designed from multiple perspectives of the laser requirements and phase control requirements of the actual application scenario. While regulating different wavelengths separately, the designed planar optical element can be adapted to various high-power laser application scenarios and meet the application requirements of various high-power laser welding applications.

[0009] Optionally, determining the thickness structures of the two groups of control structures based on the two wavelengths of the target laser and the target polarization conversion efficiency in combination with an optimization algorithm includes: Determining two groups of the control structures according to the two wavelengths in the target laser; Determining the target polarization conversion efficiency having distinctiveness at the two wavelengths in the target laser based on the regulation function requirement; Based on the optimization algorithm, the thickness structures of the two groups of the control structures are determined in combination with the wavelength data of the two wavelengths and the target polarization conversion efficiency; The optimization algorithm includes: a polarization characteristic algorithm and a heuristic algorithm; the thickness structure includes the number of layers of the multi-layer cascaded birefringence structure of the control structure and the variable spatial rotation direction.

[0010] In the above implementation process, when determining the thickness structures of the two groups of control structures, the control structure for separately controlling each wavelength can be determined based on the two different wavelengths in the target laser. On this basis, in order to realize the independent control function of the control structure for a single wavelength without affecting the other wavelength, the target polarization conversion efficiency of each wavelength can be determined according to the actual control function requirements of the wavelength, so as to carry out targeted control processing of the wavelength through the differentiated target polarization conversion efficiency. Using an optimization algorithm to combine the wavelength data of the two wavelengths and the target polarization conversion efficiency, the thickness structure of parameters such as the number of layers of the multi-layer cascade birefringence structure of the control structure and the variable spatial rotation direction is determined, which effectively improves the effectiveness and pertinence of the control structure when processing the two different wavelengths in the target laser, and realizes the independent control function of the dual-wavelength laser.

[0011] Optionally, the target polarization conversion efficiency includes: the conversion efficiency of the first group of regulatory structures for the first wavelength is greater than or equal to 99.99%, the conversion efficiency of the first group of regulatory structures for the second wavelength is less than or equal to 0.01%, and the conversion efficiency of the second group of regulatory structures for the second wavelength is greater than or equal to 99.99%, and the conversion efficiency of the second group of regulatory structures for the first wavelength is less than or equal to 0.01%.

[0012] In the above implementation process, for the case where the target laser has two different wavelengths, a first wavelength and a second wavelength, the differentiated target polarization conversion efficiency may include: the conversion efficiency of the first group of control structures designed for the first wavelength is greater than or equal to 99.99%, and the conversion efficiency for the second wavelength is less than or equal to 0.01%, that is, the first group of control structures only processes the first wavelength and does not process the second wavelength; the conversion efficiency of the second group of control structures designed for the second wavelength is greater than or equal to 99.99%, and the conversion efficiency for the first wavelength is less than or equal to 0.01%, that is, the second group of control structures only processes the second wavelength and does not process the first wavelength. Different conversion efficiencies can be set for different wavelengths in different control structures to reduce the impact of the control components on non-processed wavelengths and realize the independent control function of dual-wavelength lasers.

[0013] Optionally, determining the spatial parameters of the two groups of control structures according to the two wavelengths and the phase control requirements corresponding to each wavelength includes: Determining the control parameters of each wavelength according to the phase control requirements corresponding to each wavelength; wherein the control parameters include wavelength data, incident state, light field, and exit state of the wavelength; Determining a modulation phase of each group of the control structures based on the control parameters; Based on the modulation phase, the spatial parameters of the two groups of control structures are determined; wherein the spatial parameters include the azimuth angle of the control structure for geometrically controlling the wavelength by rotating.

[0014] In the above implementation process, when determining the spatial parameters of the two groups of control structures, the wavelength data, incident state, light field and output state and other control parameters corresponding to each wavelength can be determined according to the specific phase control requirements of each wavelength, so as to determine the modulation phase of each group of control structures according to the control parameters, thereby determining the spatial parameters such as the azimuth angle of the two groups of control structures for geometric phase control of the wavelength by rotation based on the modulation phase, and being able to independently phase modulate different wavelengths through geometric phase control to shape lasers of different wavelengths into different light beams, thereby realizing the independent control function of dual-wavelength lasers.

[0015] Optionally, the target laser includes circularly polarized light and linearly polarized light; The target laser includes at least one of a continuous laser with dual wavelengths, a millisecond laser, a nanosecond laser, a picosecond laser, and a femtosecond laser.

[0016] In the above implementation process, the target laser can include multiple types of polarized light, and the target laser can also be various types of high-power lasers such as continuous laser with dual wavelength, millisecond laser, nanosecond laser, picosecond laser and femtosecond laser, which can meet the control requirements of various dual-wavelength and high-power application scenarios.

[0017] In a second aspect, an embodiment of the present application further provides a method for preparing a high-threshold planar optical element, the method comprising: Pre-treating the base material; By using laser processing technology, based on the design structure determined by the planar optical element design method described in any one of the first aspects above, the base material is processed to obtain a planar optical element.

[0018] In the above implementation process, laser processing technology can be used to process the pretreated base material based on the design structure of the designed planar optical element to prepare the corresponding planar optical element. The prepared planar optical element can regulate different wavelengths separately, and adapt to the application scenarios of various high-power lasers, meeting the application requirements of various high-power laser welding.

[0019] In a third aspect, an embodiment of the present application further provides a high-threshold planar optical element, the planar optical element comprising: a base material; wherein the planar optical element is prepared based on the above-mentioned planar optical element preparation method; The base material is internally processed and provided with two sets of regulating structures; The first group of control structures is used to shape the first wavelength in the target laser; The second group of control structures is used to shape the second wavelength of the target laser.

[0020] In the above implementation process, the specific material of the prepared planar optical element is provided with a first group of control structures and a second group of control structures. The first group of control structures is used to shape the first wavelength of the target laser corresponding to the application scenario, and the second group of control structures is used to shape the second wavelength of the target laser. Different wavelengths can be regulated separately, and it is suitable for the application scenarios of various high-power lasers and meets the application requirements of various high-power laser welding.

[0021] Optionally, the two groups of control structures are coaxially arranged based on the transmission direction of the laser.

[0022] In the above implementation process, the two sets of control structures are coaxially arranged inside the base material based on the transmission direction of the laser to improve the consistency of the beam position during laser processing.

[0023] Optionally, the matrix material includes: optical glass or optical material with a high damage threshold; The damage threshold of the matrix material is determined based on the usage requirements of the target laser.

[0024] In the above implementation process, the matrix material of the planar optical element is set to optical glass or other types of optical materials with a high damage threshold. The matrix material with the corresponding damage threshold can be selected according to the actual usage requirements of the target laser in the application scenario; the control structure prepared inside the matrix material has a laser damage threshold close to that of the matrix material, which can improve the anti-laser damage ability of the planar optical element and meet the application requirements of high-power laser welding.

[0025] Optionally, each group of the regulating structures comprises multiple layers of cascaded birefringence structures, and the spatial orientation of the birefringence structures within the layers is variable.

[0026] In the above implementation process, each group of control structures has a multi-layer cascaded birefringence structure, and the spatial orientation of the birefringence structure within the layer is variable, which can independently realize the spatial phase control of the light field of a specific wavelength, thereby realizing the decoupling modulation of the dual-wavelength laser light field.

[0027] In summary, the embodiments of the present application provide a high-threshold planar optical element design method, preparation method and planar optical element, which can design the control structure from multiple perspectives of the laser requirements and phase control requirements of actual application scenarios. While regulating different wavelengths separately, the designed and prepared planar optical elements can adapt to various high-power laser application scenarios and meet the application requirements of various high-power laser welding applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A schematic flow chart of a high-threshold planar optical element design method provided in an embodiment of the present application; Figure 2 A detailed flowchart of step S100 provided in an embodiment of the present application; Figure 3 A detailed flowchart of step S200 provided in an embodiment of the present application; Figure 4 A schematic flow chart of a method for preparing a high-threshold planar optical element provided in an embodiment of the present application; Figure 5 A schematic structural diagram of a high-threshold planar optical element provided in an embodiment of the present application.

[0030] Icons: 410-matrix material; 421-first group of regulatory structures; 422-second group of regulatory structures; A-transmission direction. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the embodiments of the present application.

[0032] In the field of dual-wavelength light field control, in order to control different wavelengths separately, it is usually necessary to set up devices with complex structures and high processing difficulty for processing. The current light field control method based on optical path accumulation faces the problems of large size, difficult processing of complex structures and limited control accuracy, which makes it difficult to meet the development trend of high-precision optical system integration. In order to solve this problem, in recent years, planar optical elements based on subwavelength structures can flexibly control multiple optical parameters such as phase, amplitude, polarization, etc. and simplify the design of optical systems, bringing a new path to solving the problem of integrated control of complex light fields. However, current planar optical elements are limited by the intrinsic threshold of the material and the structural light field coupling effect, and have a low damage threshold. They cannot withstand the action of high-power lasers in the kilowatt level and cannot meet the application requirements of high-power laser welding.

[0033] In order to solve the above problems, the embodiments of the present application provide a high-threshold planar optical element design method, a preparation method and a planar optical element, which can design the control structure from multiple perspectives of the laser requirements and phase control requirements of actual application scenarios. While regulating different wavelengths separately, the designed and prepared planar optical elements can adapt to various high-power laser application scenarios and meet the application requirements of various high-power laser welding.

[0034] See also Figure 1 , Figure 1 A schematic flow chart of a high-threshold planar optical element design method provided in an embodiment of the present application, the method may include steps S100-S200.

[0035] Step S100 , based on the two wavelengths of the target laser and the target polarization conversion efficiency, combined with an optimization algorithm, determines the thickness structures of the two groups of control structures.

[0036] Among them, when designing the structure of the planar optical element according to the use requirements of high-power laser welding scenarios, it is taken into account that the dual-wavelength laser can improve the welding stability of the material and the mechanical strength of the weldment compared with the single-wavelength laser. Therefore, the corresponding target laser in the welding scenario can be set to a dual-wavelength polarized laser. For two different wavelengths, two sets of control structures can be set to perform shaping and other control processing on each wavelength respectively. Therefore, the thickness structure of the two sets of control structures can be determined according to the target polarization conversion efficiency corresponding to the two wavelengths in combination with the optimization algorithm.

[0037] Optionally, taking the two wavelengths in the target laser as the first wavelength and the second wavelength as an example, and the two groups of control structures set as the first group of control structures and the second group of control structures as an example, the target polarization conversion efficiency may include the two conversion efficiencies of the first group of control structures for the first wavelength and the second wavelength, and the two conversion efficiencies of the second group of control structures for the first wavelength and the second wavelength.

[0038] It should be noted that each group of control structures may be provided with a multi-layer cascaded birefringent structure, such as a multi-layer cascaded birefringent nanostructure, to improve the control effect of the planar optical element on shaping the laser.

[0039] Step S200: determining the spatial parameters of two groups of control structures according to the two wavelengths and the phase control requirements corresponding to each wavelength.

[0040] Among them, the spatial parameters of the two sets of control structures can be determined according to the two wavelengths and the phase control requirements corresponding to each wavelength, so as to obtain the design structure of the planar optical element including the thickness structure and spatial parameters of the two sets of control structures.

[0041] For example, the thickness structure of the control structure may include various types of data such as the number of layers of the birefringence structure in the laser transmission direction, and the spatial parameters of the control structure may be data such as the angle of geometric phase control for different light fields.

[0042] It should be noted that the target laser can include various types of polarized lasers such as circularly polarized light and linearly polarized light, and the target laser can include various types of high-power lasers such as continuous laser with dual wavelength, millisecond laser, nanosecond laser, picosecond laser and femtosecond laser, which can meet the control needs of various dual-wavelength and high-power application scenarios.

[0043] exist Figure 1 In the embodiment shown, the control structure can be designed from multiple perspectives of the laser requirements and phase control requirements of actual application scenarios. While regulating different wavelengths separately, the designed planar optical element can adapt to various high-power laser application scenarios and meet the application requirements of various high-power laser welding.

[0044] Optionally, see Figure 2 , Figure 2 A detailed flowchart of step S100 is provided in an embodiment of the present application. Step S100 may include steps S110-S130.

[0045] Step S110 , determining two groups of control structures according to two wavelengths of the target laser.

[0046] When determining the thickness structures of the two groups of control structures, the control structure for individually controlling each wavelength can be determined based on the two different wavelengths in the target laser.

[0047] Optionally, taking the target laser as a high-power incident circularly polarized laser as an example, the first wavelength can be λ1=450nm, and the second wavelength can be λ2=1070nm. In the two groups of control structures, the first group of control structures processes the first wavelength, and the second group of control structures processes the second wavelength.

[0048] Step S120 : determining target polarization conversion efficiencies having distinctive characteristics at two wavelengths in the target laser based on the control function requirement.

[0049] Among them, in order to realize the independent control function of the control structure to perform single control on a certain wavelength without affecting other wavelengths, different target polarization conversion efficiencies can be determined for each wavelength according to the actual control function requirements of the wavelength, so that a certain wavelength can be targetedly controlled through the differentiated target polarization conversion efficiency.

[0050] Optionally, the regulation function requirement is a processing requirement that the first group of regulation structures regulate the first wavelength and the second group of regulation structures regulate the second wavelength.

[0051] Step S130 : Based on the optimization algorithm, the thickness structures of the two groups of control structures are determined in combination with the wavelength data of the two wavelengths and the target polarization conversion efficiency.

[0052] Among them, an optimization algorithm can be used to combine the wavelength data of the two wavelengths and the target polarization conversion efficiency to determine the thickness structure of parameters such as the number of layers of the multi-layer cascade birefringence structure including the regulatory structure and the variable spatial rotation direction.

[0053] Optionally, the optimization algorithm may include: a polarization characteristic algorithm and a heuristic algorithm. The heuristic algorithm may include various types of algorithms such as a particle swarm algorithm, a genetic algorithm or a simulated annealing algorithm. The thickness structure may include a multi-layer cascade of birefringence structures to regulate the number of layers and the variable spatial rotation direction.

[0054] For example, when designing a multi-layer cascaded birefringent nanostructure, the Stokes + Mueller matrix method can be used, and the particle swarm algorithm can be used to optimize the number of layers and the variable spatial rotation direction of the multi-layer cascaded birefringent structure of each group of control structures, and finally obtain a thickness structure that can independently control different wavelengths.

[0055] exist Figure 2 In the embodiment shown, the effectiveness and pertinence of the control structure in processing two different wavelengths in the target laser are effectively improved, thereby realizing the independent control function of the dual-wavelength laser.

[0056] It should be noted that the target polarization conversion efficiency includes: the conversion efficiency of the first group of control structures for the first wavelength is greater than or equal to 99.99%, and the conversion efficiency of the first group of control structures for the second wavelength is less than or equal to 0.01%, that is, the first group of control structures processes only the first wavelength and does not process the second wavelength. Furthermore, the conversion efficiency of the second group of control structures for the second wavelength is greater than or equal to 99.99%, and the conversion efficiency of the second group of control structures for the first wavelength is less than or equal to 0.01%, that is, the second group of control structures processes only the second wavelength and does not process the first wavelength. Different conversion efficiencies can be set for different wavelengths in different control structures to reduce the impact of the control components on non-processed wavelengths and achieve independent control of dual-wavelength lasers.

[0057] Optionally, for the birefringent nanostructure set in the control structure, when the target laser is a circularly polarized laser incident, the outgoing light field contains unmodulated co-polarized circular polarization and phase-modulated cross-polarized circular polarization, and the cross-polarized circular polarization has a modulation phase of ±2α (where ± corresponds to right-handed / left-handed incident circularly polarized light, and α represents the azimuth angle of the birefringent structure), and the conversion efficiency is: η=sin 2 (γ / 2), where γ represents the birefringence retardation. Therefore, during the design process, by optimizing the multi-layer cascaded birefringence structure within each set of control structures, the conversion efficiency can be close to 100% for one wavelength (e.g., λ1 / λ2) and close to 0% for the other wavelength (e.g., λ2 / λ1), thus achieving independent control of both wavelengths.

[0058] For example, when the first wavelength λ1 is 450nm and the second wavelength λ2 is 1070nm, the conversion efficiency of the first group of control structures for λ1 is greater than 99.99%, and the conversion efficiency for λ2 is less than 0.01%; the conversion efficiency of the second group of control structures for λ1 is less than 0.01%, and the conversion efficiency for λ2 is greater than 99.99%, which can meet the needs of independent decoupling control.

[0059] Optionally, see Figure 3 , Figure 3 A detailed flow chart of step S200 is provided in an embodiment of the present application. Step S200 may include steps S210-S230.

[0060] Step S210: determining a control parameter for each wavelength according to a phase control requirement corresponding to each wavelength.

[0061] Among them, when determining the spatial parameters of the two sets of control structures, the control parameters corresponding to each wavelength can be determined according to the specific phase control requirements of each wavelength. The control parameters may include wavelength data, incident state, light field and output state, and other data related to light field control.

[0062] Optionally, the phase control requirement may include requirements for the output light field, such as the output light field including phase-modulated cross-polarization circular polarization. The incident state may include the laser state of the target laser incident on it, such as circular polarization. The light field may include various types of light fields, such as a focused beam. The output state may include the laser state of the target laser after passing through a planar optical element, such as cross-polarization circular polarization.

[0063] Step S220: determining the modulation phase of each group of control structures based on the control parameters.

[0064] Step S230: determining the spatial parameters of the two groups of control structures based on the modulation phase.

[0065] The modulation phase of each group of control structures can be determined according to the control parameters, thereby determining the spatial parameters such as the azimuth angle of the two groups of control structures for geometric phase control of the wavelength by rotation based on the modulation phase.

[0066] For example, for a high-power incident circularly polarized laser with λ1=450nm, its light field is designed to be a focused beam, and the first group of control structures is responsible for phase θ1 modulation, and by rotating the azimuth angle of the first group of control structures For geometric phase control; for high-power incident circularly polarized laser with λ2=1070nm, the light field is designed to be a focused vortex beam, and the second group of control structures is responsible for phase θ2 modulation, and by rotating the azimuth angle of the second group of structures Perform geometric phase control.

[0067] ; ; ; ; Among them, f1 and f2 are the focal lengths of the corresponding incident light, is the topological charge of the vortex beam, is the spatial azimuth, and For example, in the calculation result of the lens focusing phase, λ1=450nm, f1=200mm, in the calculation result of the focused vortex phase, λ2=1070nm, f2=200mm, =1.

[0068] exist Figure 3 In the illustrated embodiment, different wavelengths can be independently phase modulated by geometric phase control to shape lasers of different wavelengths into different beams, thereby achieving dual-wavelength laser independent control functionality.

[0069] See also Figure 4 , Figure 4 A schematic flow chart of a method for preparing a high-threshold planar optical element provided in an embodiment of the present application, the method may include steps S310-S320.

[0070] Step S310: pre-treating the base material.

[0071] In order to reduce the adverse effects of impurities on processing and preparation, the base material can be pretreated first.

[0072] For example, the matrix material can be various types of transparent materials, such as quartz glass, and the pretreatment can include various treatments such as cleaning and drying. For example, the quartz glass sample is cleaned by ultrasonic cleaning in anhydrous ethanol, deionized water and acetone for 15 minutes respectively, and then dried with nitrogen after cleaning. The quartz glass is placed on the three-dimensional high-precision translation stage of the femtosecond processing system and fixed for processing.

[0073] Step S320 , using laser processing technology, based on the determined design structure, the base material is processed to obtain a planar optical element.

[0074] Among them, laser processing technology can be used to process the pre-treated base material based on the design structure of the designed planar optical element, and the base material can be modified to prepare the corresponding planar optical element.

[0075] For example, a grayscale image of the design structure of a planar optical component can be imported into the control software of a femtosecond laser processing system. Using a bottom-up, layer-by-layer scanning approach, the nanostructure with spatially distributed orientation can be fabricated by real-time control of the laser polarization direction during high-speed processing. Operating parameters in the femtosecond laser processing system can include a laser processing speed of 1-20 mm / s and a layer spacing of 50-200 μm. After processing is complete, the laser processing system is shut down and the sample removed to obtain the desired planar optical component.

[0076] exist Figure 4 In the illustrated embodiment, the prepared planar optical element can regulate different wavelengths separately, and is adaptable to various application scenarios of high-power lasers, meeting the application requirements of various high-power laser welding applications.

[0077] See also Figure 5 , Figure 5 This is a schematic structural diagram of a high-threshold planar optical element provided in an embodiment of the present application, wherein the planar optical element is manufactured based on the above-mentioned planar optical element manufacturing method. The planar optical element may include: a base material 410.

[0078] It should be noted that base material 410 can include optical glass or other optical materials with a high damage threshold. The damage threshold of base material 410 is determined based on the target laser's usage requirements. The base material 410 of the planar optical element is configured as optical glass or other optical materials with a high damage threshold. Base material 410 with a corresponding damage threshold can be selected based on the actual usage requirements of the target laser in the application scenario. The control structure fabricated within base material 410 has a laser damage threshold close to that of base material 410, thereby improving the planar optical element's resistance to laser damage and meeting the application requirements of high-power laser welding.

[0079] For example, the matrix material 410 can be set to be quartz glass, K9 glass, sapphire and other optical glasses with a high damage threshold or other types of optical materials.

[0080] Two sets of control structures are machined into base material 410: a first set of control structures 421 for shaping the first wavelength of the target laser, and a second set of control structures 422 for shaping the second wavelength of the target laser. The first set of control structures 421 shapes the first wavelength of the target laser for the application scenario, while the second set of control structures 422 shapes the second wavelength of the target laser. This allows for separate control of different wavelengths, adapting to various high-power laser application scenarios and meeting various high-power laser welding application requirements.

[0081] Optionally, after the first group of regulating structures 421 and the second group of regulating structures 422 perform phase modulation on the dual wavelengths respectively, the lasers of two different wavelengths can be shaped into different beams, and the spatial position of the shaped beams can also be freely customized according to actual usage requirements.

[0082] It should be noted that the two sets of control structures are coaxially arranged based on the transmission direction of the laser. The two sets of control structures are coaxially arranged inside the base material 410 based on the transmission direction A of the laser to improve the consistency of the beam position during laser processing.

[0083] Optionally, each group of control structures comprises multiple layers of cascaded birefringent structures, with the spatial orientation of the birefringent structures within the layers being variable. Each group of control structures comprises multiple layers of cascaded birefringent structures, with the spatial orientation of the birefringent structures within the layers being variable, enabling independent spatial phase control of a light field at a specific wavelength, thereby achieving decoupled modulation of a dual-wavelength laser light field.

[0084] Optionally, for a multi-layer cascade structure, the spatial rotation direction of the birefringent structure between layers is variable, so that each group of control structures can only perform beam shaping for one wavelength without affecting the laser propagation of another wavelength. The spatial orientation of the birefringent structure within the layer is variable to achieve independent control of the spatial phase of the light field, including but not limited to focusing, annular beam, Bessel beam, and flat-top beam. The azimuth angle corresponding to the spatial orientation of the birefringent structure within the layer The value range is [0,π], which is consistent with the modulation phase of the phase distribution. The relationship satisfies: =±2 , ± corresponds to right-handed / left-handed incident circularly polarized light.

[0085] Optionally, the birefringent structures in the first group of regulating structures 421 and the second group of regulating structures 422 have a high damage threshold close to that of the matrix material 410 itself.

[0086] The present application can be based on a single-piece base material, and can use femtosecond laser to prepare two groups of control structures with multi-layer cascaded birefringence structures, thereby realizing independent light field control of dual-wavelength high-power lasers. When the dual-wavelength circularly polarized laser is irradiated onto the planar structure, the lasers of different transmission wavelengths will be independently controlled to achieve different light fields to meet the needs of laser welding. The technical effects of the present application include: 1. The planar optical element has the ability to independently design and control dual-wavelength control, and the shaping phase of each wavelength can be independently designed without the need for complex achromatic design. 2. The planar optical element is prepared in the body of the base material using a femtosecond laser, and has the characteristics of planarization and integration, which matches the development trend of high-precision optical system integration. 3. The laser damage threshold of the control structure inside the base material is close to the intrinsic threshold of the base material, has a high laser damage threshold, exhibits good resistance to laser damage, and can adapt to the working scene of kilowatt-level high-power laser welding. 4. The structural transmittance of the planar optical element reaches over 95% in the visible-near-infrared band and exceeds 99% in the near-infrared band. Its high transmittance enables efficient modulation of high-power lasers and improves laser energy utilization. 5. The control structure of the planar optical element is fabricated within the base material, making it extremely resistant to mechanical damage. Compared with the nanopillar structure of traditional metasurfaces, it has higher mechanical stability. Furthermore, the control structure is protected by the material itself, making it less susceptible to environmental influences and having better environmental adaptability.

[0087] The planar optical elements prepared by femtosecond laser processing technology in this application have the advantages of high damage threshold and high structure / device transmittance, which solves the problem of integrated modulation of high-power dual-wavelength laser optical systems. It has important application value in the field of high-power laser welding and can greatly improve the stability and strength of laser welding, thereby promoting the application of laser welding in various fields such as aerospace, marine ships, automobile manufacturing, mechanical engineering, and power batteries.

[0088] The foregoing is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures.

[0089] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

[0090] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, the elements defined by the phrase "comprising..." do not exclude the presence of other identical elements in the process, method, article, or device comprising the elements.

Claims

1. A method for designing a high-threshold planar optical element, characterized in that: The method comprises: Based on the two wavelengths of the target laser and the target polarization conversion efficiency, the thickness structures of the two groups of control structures are determined in combination with the optimization algorithm; Determining spatial parameters of two groups of control structures according to the two wavelengths and the phase control requirements corresponding to each wavelength; Wherein, the design structure of the planar optical element includes the thickness structure and the spatial parameters of two groups of the regulating structures.

2. The method according to claim 1, characterized in that The method of determining the thickness structures of the two groups of control structures based on the two wavelengths of the target laser and the target polarization conversion efficiency in combination with the optimization algorithm includes: Determining two groups of the control structures according to the two wavelengths in the target laser; Determining the target polarization conversion efficiency having distinctiveness at the two wavelengths in the target laser based on the regulation function requirement; Based on the optimization algorithm, the thickness structures of the two groups of the control structures are determined in combination with the wavelength data of the two wavelengths and the target polarization conversion efficiency; The optimization algorithm includes: a polarization characteristic algorithm and a heuristic algorithm; the thickness structure includes the number of layers of the multi-layer cascaded birefringence structure of the control structure and the variable spatial rotation direction.

3. The method according to claim 2, characterized in that in, The target polarization conversion efficiency includes: the conversion efficiency of the first group of control structures for the first wavelength is greater than or equal to 99.99%, the conversion efficiency of the first group of control structures for the second wavelength is less than or equal to 0.01%, and the conversion efficiency of the second group of control structures for the second wavelength is greater than or equal to 99.99%, and the conversion efficiency of the second group of control structures for the first wavelength is less than or equal to 0.01%.

4. The method according to claim 1, wherein Determining the spatial parameters of the two groups of control structures according to the two wavelengths and the phase control requirements corresponding to each wavelength includes: Determining the control parameters of each wavelength according to the phase control requirements corresponding to each wavelength; wherein the control parameters include wavelength data, incident state, light field, and exit state of the wavelength; Determining a modulation phase of each group of the control structures based on the control parameters; Based on the modulation phase, the spatial parameters of the two groups of control structures are determined; wherein the spatial parameters include the azimuth angle of the control structure for geometrically controlling the wavelength by rotating.

5. The method according to any one of claims 1 to 4, characterized in that in, The target laser includes circularly polarized light and linearly polarized light; The target laser includes at least one of a continuous laser with dual wavelengths, a millisecond laser, a nanosecond laser, a picosecond laser, and a femtosecond laser.

6. A method for preparing a high-threshold planar optical element, characterized in that: The method comprises: Pre-treating the base material; The planar optical element is obtained by processing the base material using laser processing technology based on the design structure determined by the planar optical element design method according to any one of claims 1 to 5.

7. A high-threshold planar optical element, characterized in that: The planar optical element comprises: a base material; wherein the planar optical element is prepared based on the planar optical element preparation method according to claim 6; The base material is internally processed and provided with two sets of regulating structures; The first group of control structures is used to shape the first wavelength in the target laser; The second group of control structures is used to shape the second wavelength of the target laser.

8. The planar optical element according to claim 7, wherein in, The two groups of control structures are coaxially arranged based on the transmission direction of the laser.

9. The planar optical element according to claim 7, wherein: in, The matrix material includes: optical glass or optical material with a high damage threshold; The damage threshold of the matrix material is determined based on the usage requirements of the target laser.

10. The planar optical element according to claim 7, wherein in, Each group of the regulating structures has multiple layers of cascaded birefringence structures, and the spatial orientation of the birefringence structures within the layers is variable.

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