A femtosecond laser vector processing method and system based on a vortex beam

Abstract

The application discloses a kind of femtosecond laser vector processing method and system based on vortex light beam, it is related to femtosecond laser processing technical field, comprising: S1, polarized light splitting prism is divided into P light and S light by the incident femtosecond laser pulse light beam, completes preliminary polarization state regulation;S2, by the angle control of half-wave plate and quarter-wave plate, the femtosecond laser after polarization state regulation is dynamically regulated;S3, by vortex wave sheet, the femtosecond laser after dynamic regulation is pulse modulation, coupling, to convert femtosecond laser into vortex light beam with predetermined topological charge number and polarization state;S4, based on the position of the workpiece to be machined is adjusted based on preset processing path, completes vortex light beam in the vector scanning processing of workpiece surface.This application makes full use of vortex light beam with hollow annular energy distribution, to reduce the energy size of beam center region, optimize the energy distribution of beam in section, more conducive to material processing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of femtosecond laser processing. More particularly, the present application relates to a femtosecond laser vector processing method and system based on a vortex beam. BACKGROUND

[0002] With the rapid development of modern industry, the requirements for processing technology in manufacturing industry are becoming higher and higher, and the complexity and precision requirements of processing objects are constantly improving. The traditional laser processing technology gradually exposes its limitations when dealing with complex curved surfaces and high-precision processing tasks. For example, in the fields of aerospace, precision machinery and microelectronics, the processing precision of complex-shaped parts is extremely high, and the traditional laser processing technology often cannot meet these demands. When processing complex curved surfaces, problems such as insufficient processing precision, poor surface quality and low processing efficiency often occur.

[0003] At the same time, as a new type of beam with unique spiral phase structure, vortex beam is emerging in the field of micro-nano processing due to its excellent performance in light field control. The spiral phase structure of vortex beam enables precise control of the light field, including intensity distribution, phase distribution and polarization state of the beam. This precise light field control capability enables vortex beam to achieve more precise processing effects in micro-nano processing, such as in the fields of micro-nano structure manufacturing, nano material processing and biomedical micro-nano device manufacturing, the application of vortex beam shows great potential. It can achieve high-precision processing of micro-nano scale materials while maintaining high processing efficiency, bringing new development opportunities to the field of micro-nano processing.

[0004] However, although vortex beam has many advantages in micro-nano processing, there are still some problems to be solved in the current femtosecond laser vector processing system based on vortex beam. First of all, the lack of processing flexibility is a prominent problem. The existing femtosecond laser vector processing system often needs to adjust the light path and optimize the parameters when processing complex-shaped workpieces, which not only increases the preparation time and cost of processing, but also limits the processing efficiency of the system. Secondly, the complexity and cost of the equipment are also a key problem that limits the widespread use of vortex beams. In actual processing, the generation of vortex beams usually requires complex optical elements and equipment, such as spatial light modulators, laser resonators, etc., which increases the complexity and cost of the system. The existence of these problems seriously limits the application of femtosecond laser vector processing system based on vortex beam in complex processing tasks, hindering its greater role in modern manufacturing. SUMMARY

[0005] An object of the present application is to solve at least the above problems and / or deficiencies, and to provide at least the advantages described later.

[0006] To achieve these objects and other advantages and in view of its purposes, a femtosecond laser vector processing method based on vortex beams is provided, comprising:

[0007] S1, a polarization beam splitter prism divides the incident femtosecond laser pulse beam into P light and S light, and completes the preliminary polarization state regulation;

[0008] S2, the femtosecond laser after polarization state regulation is dynamically regulated by controlling the angle of half-wave plate and quarter-wave plate;

[0009] S3, the femtosecond laser after dynamic regulation is pulse modulated and coupled by vortex wave plate, so as to convert the femtosecond laser into vortex beams with predetermined topological charge number and polarization state;

[0010] S4, based on the preset processing path, the position of the workpiece to be processed is adjusted by using a three-dimensional motion system, and vector scanning processing of vortex beams on the surface of the workpiece is completed;

[0011] In S3, the cross-sectional energy of the vortex beam presents a hollow ring distribution, and the size of the hollow is positively correlated with the topological charge number.

[0012] Preferably, in S1, the polarization beam splitter prism uses an optical crystal material with a polarization beam splitting efficiency higher than 98%, and the reflectivity of the incident surface and the exit surface of the polarization beam splitter prism is less than 0.1%.

[0013] Preferably, in S2, the phase delay accuracy of the half-wave plate and the quarter-wave plate is better than 0.1 degree, and the material of the half-wave plate and the quarter-wave plate is selected as a crystal material with high optical transmittance and low absorption.

[0014] Preferably, in S2, the polarization state of the femtosecond laser is combined and regulated by adjusting the angle of the half-wave plate and the quarter-wave plate.

[0015] The combination regulation includes linear polarization, circular polarization, elliptical polarization, and phase regulation.

[0016] Preferably, in S3, the conversion efficiency of the vortex wave plate is higher than 90%, and the topological charge number m of the vortex wave plate is any one of 1, 2, 3, and 4.

[0017] Preferably, in S4, the positioning accuracy of the three-dimensional motion system is ±500 nm, and the repeat positioning accuracy is ±50 nm.

[0018] A system is applied to the femtosecond laser vector processing method based on vortex beams, comprising:

[0019] A laser source module for providing femtosecond laser pulse beams is provided;

[0020] A beam control module for regulating the polarization state and phase of femtosecond laser pulse beams;

[0021] A femtosecond laser pulse modulation module for modulating femtosecond laser pulses into vortex beams with predetermined topological charges and polarization states;

[0022] A light path transmission module for outputting the generated vector vortex beams to a machining site along a predetermined light path;

[0023] A vector scanning module for realizing the machining action of vortex beams on the surface of a workpiece according to a preset machining path;

[0024] Preferably, the vortex beam generation module is a vortex wave plate.

[0025] Preferably, the beam control module comprises:

[0026] A polarization beam splitter prism for regulating the polarization characteristics of laser beams;

[0027] A half-wave plate and a quarter-wave plate for changing the polarization state and phase of beams by dynamically adjusting the angle.

[0028] Preferably, the light path transmission module comprises:

[0029] A mirror I for preliminarily guiding the light path of the vector vortex beam;

[0030] A light wedge for separating part of the light beam transmitted by the mirror I to a power meter;

[0031] Mirrors II and III for guiding the main light path output by the light wedge to a focusing objective lens.

[0032] The present application at least has the following advantages: the present application provides a machining system which does not need complex optical elements and devices, so it has the advantages of low device complexity and controllable cost, and through beam regulation and high-precision scanning technology, it realizes efficient, fast and high-quality femtosecond laser machining.

[0033] The application provides a processing method, which is obviously different from a traditional Gaussian beam, in that a complex amplitude distribution in a cross section of the vortex beam presents a characteristic spiral phase wave front, and a phase value presents a periodical change related to an azimuth angle around an optical axis. The topological phase structure produces a certain phase singularity, and a physical manifestation is that an optical field intensity at a position of the optical axis has a zero-value singularity. According to the spiral phase distribution, a far-field or near-field intensity distribution of the vortex beam generally presents a clear annular structure feature. Specifically, along a radial direction, the beam intensity presents a zero value at the center of the optical axis; with an increasing radial coordinate distance, the intensity experiences a monotonous increasing process, reaches a peak intensity at a certain radius, and then presents a non-monotonous decreasing trend with a further increase of the radial distance. The vortex beam has a hollow annular energy distribution, which is fully utilized to obviously reduce the energy size of a central region of the beam, optimize the energy distribution of the beam in the cross section, and be more beneficial to material processing.

[0034] Other advantages, objects, and features of the application will be understood by those skilled in the art from the following description, and will be appreciated by those skilled in the art upon reading and understanding the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic diagram of an overall architecture of a femtosecond laser vector processing system based on a vortex beam in the application.

[0036] The femtosecond laser-1, the polarizing beam splitter prism-2, the half-wave plate-3, the quarter-wave plate-4, the vortex wave plate-5, the mirror I-6, the power meter-7, the beam splitter wedge-8, the mirror II-9, the mirror III-10, the focusing objective-11, and the three-dimensional motion platform-12. DETAILED DESCRIPTION

[0037] The application will be further described in detail below with reference to the drawings, so that those skilled in the art can implement the application according to the description.

[0038] A femtosecond laser vector processing system and method based on a vortex beam, comprising the following steps:

[0039] Step one, the femtosecond laser pulse beam is guided to the polarizing beam splitter prism. When the femtosecond laser pulse beam is incident on the polarizing beam splitter prism, the prism will divide the light into two beams according to the polarization direction of the light: one is linearly polarized light (P light) parallel to the incident plane, and the other is linearly polarized light (S light) perpendicular to the incident plane. By reasonably designing the optical path, it is ensured that the P light is effectively transmitted to the subsequent optical system, and the S light is ignored or guided to other directions. This process realizes the preliminary regulation of the polarization state of the laser, ensures that the subsequent optical path can receive and process linearly polarized light, and lays a foundation for the subsequent dynamic regulation of the polarization state and beam modulation;

[0040] In practical applications, the polarization beam splitter in this step uses high-precision optical crystal materials, with a polarization splitting efficiency higher than 98%. The entrance and exit surfaces of the polarization beam splitter are treated with special anti-reflection coating, with a reflectivity less than 0.1%.

[0041] Step two, after the initial polarization state control is completed, further dynamic control of the polarization state of the laser is performed through rotating half-wave plates and quarter-wave plates. Half-wave plates and quarter-wave plates are common optical phase retarders that can control the polarization state of the light beam by changing their relative rotation angle. Half-wave plates can convert linearly polarized light into linearly polarized light in any direction, while quarter-wave plates can convert linearly polarized light into circularly or elliptically polarized light. By precisely controlling the rotation angle of the half-wave plate and the quarter-wave plate, continuous control of the polarization state of the light beam can be achieved, such as switching from linearly polarized light to circularly polarized light, or from right-handed circularly polarized light to left-handed circularly polarized light. In addition, this dynamic control can also fine-tune the phase of the light beam, thereby achieving comprehensive control of the polarization state and phase of the light beam.

[0042] In practical applications, the rotating half-wave plate and quarter-wave plate combination in this step controls the polarization state of the laser, achieving various polarizations such as linear polarization, circular polarization, and elliptical polarization. Therefore, the materials of the half-wave plate and the quarter-wave plate are selected to be crystal materials with high optical transmittance and low absorption. The rotating half-wave plate and quarter-wave plate are manufactured using high-precision optical processing technology, with a phase delay accuracy better than 0.1 degrees.

[0043] Step three, the femtosecond laser pulse is modulated using a vortex wave plate to convert it into a vortex light beam with a specific topological charge and polarization state. By selecting an appropriate vortex wave plate, the topological charge (i.e., the helicity of the light beam) of the vortex light beam can be precisely controlled, thereby achieving complex modulation of the light beam. In combination with the polarization state controlled in the previous step, the characteristics of the vortex light beam can be further optimized to play a greater role in subsequent processing. This step is the core of the entire patent technology, and through the modulation of the vortex wave plate, it realizes the transformation from an ordinary femtosecond laser pulse beam to a vortex light beam with special physical properties, providing a key beam form for subsequent vector scanning processing.

[0044] In practical applications, the polarization vortex light beam in this step is generated by coupling the polarization state controlled in step two and the topological charge of the vortex wave plate. The topological charge of the vortex wave plate is one of m = 1, 2, 3, 4, and the conversion efficiency of the vortex wave plate is higher than 90%. In addition, the surface of the vortex wave plate is covered with a special protective film that has high optical transmittance and good scratch resistance, effectively extending the service life of the vortex wave plate and reducing the problem of beam quality degradation caused by surface damage.

[0045] Step four, through the high-precision three-dimensional motion system, according to the preset processing path, realize the vector scanning of the vortex light beam on the workpiece surface. The three-dimensional motion system is usually composed of high-precision motor drive device and precise positioning platform, which can realize the accurate control of the light beam in three-dimensional space. In the processing process, according to the shape of the workpiece and the processing requirements, the processing path is designed in advance and input into the motion control system. The motion system moves the workpiece or the light beam according to the preset path, so that the vortex light beam scans the workpiece surface according to the predetermined track. Because the vortex light beam has unique phase distribution and polarization state, it can produce special processing effect in the processing process, such as higher processing precision, more complex structure processing ability or more uniform energy distribution. Through vector scanning processing, high-precision and high-efficiency processing of workpiece surface can be realized, which meets the strict requirements of micro-nano manufacturing, precision machining and other fields on processing quality;

[0046] In actual application, the positioning accuracy of the high-precision three-dimensional motion system in this step is ±500nm, and the repeat positioning accuracy is ±50nm.

[0047] As shown in Figure 1 A femtosecond laser vector processing system based on vortex light beam, comprising: a laser light source module, a beam control module, an optical path transmission module, a vortex light beam generation module and a vector scanning module;

[0048] The laser light source module adopts femtosecond laser 1, which is used to provide stable femtosecond laser pulses to provide energy basis for subsequent processing;

[0049] The beam control module adjusts the polarization state of the laser by introducing a rotating polarization beam splitter prism 2, a half-wave plate 3 and a quarter-wave plate 4 to realize dynamic adjustment of the polarization state and phase of the light beam;

[0050] The vortex light beam generation module uses vortex plate 5 to modulate the femtosecond laser pulses into vortex light beam with specific topological charge number and polarization state;

[0051] The optical path transmission module comprises:

[0052] The mirror I 6 preliminarily guides the optical path of the vector vortex light beam;

[0053] The light wedge 8 of the power meter 7 separates part of the light beam transmitted by the mirror I;

[0054] The mirror II 9 and mirror III 10 of the mirror I output the main light path to the focusing objective 11;

[0055] The vector scanning module adopts high-precision three-dimensional motion system, according to the preset processing path, realize the vector scanning of the vortex light beam on the workpiece surface.

[0056] Embodiment:

[0057] The femtosecond laser 1 serves as the core light source, which can provide high-stability femtosecond laser pulses, laying a solid energy foundation for subsequent processing. In order to accurately regulate the polarization characteristics of the laser, a polarization beam splitter prism 2 is introduced, which mainly functions to convert the incident laser pulses into linearly polarized light (P light) and guide it to the subsequent optical system. In order to realize dynamic regulation of the beam polarization state and phase, a rotating half-wave plate 3 and a quarter-wave plate 4 are introduced. By accurately controlling the rotation angles of these two wave plates, the polarization state of the beam can be flexibly changed, thereby realizing the conversion of various polarization states from linear polarization to circular polarization and elliptical polarization. This dynamic regulation capability provides high flexibility and adaptability for the experiment, which can meet the precise requirements of polarization state under different processing needs.

[0058] Further, by adjusting the topological charge number of the vortex wave plate 5, vector beams with different polarization characteristics can be generated. When the incident light is linearly polarized light, the system can output vector polarized beams in multiple states. Taking the vortex wave plate with a topological charge number m = 1 as an example, by accurately regulating the relative angle between the direction of the incident linearly polarized light and the fast axis direction of the vortex wave plate surface, the output of radial polarization state and angular polarization state can be realized. Specifically, when the direction of the incident linearly polarized light is parallel to the 0° fast axis direction of the vortex wave plate, the system will output a vector beam with radial polarization state. This polarization state of the beam has a symmetrical polarization direction distribution in the radial direction, and the polarization direction always points to the central axis of the beam. On the contrary, when the direction of the incident linearly polarized light is perpendicular to the 0° fast axis direction of the vortex wave plate, the system will output a vector beam with angular polarization state. In this case, the polarization direction is distributed in rotation along the propagation direction of the beam, and the polarization direction always remains perpendicular to the central axis of the beam. In this way, the experimental device can flexibly generate vector beams with specific polarization characteristics, providing diversified choices for subsequent optical processing and manipulation.

[0059] Further, after the generation of the vector beam, the beam is first guided by the mirror 6 for the initial guidance of the optical path. Then, the main light path enters the light splitting wedge 8, which separates part of the beam in the main light path and guides it to the power meter 7. The function of the power meter 7 is to monitor the laser power in real time, providing key data support for power control and stability analysis in the experimental process. After passing through the light splitting wedge 8, the main light path continues to propagate along the established path, passing through the mirrors 9 and 10 in turn. The functions of the two mirrors are to further adjust the propagation direction of the beam, ensuring that the beam can accurately and correctly reach the focusing objective 11. The focusing objective 11, as a key element in the optical system, its main function is to focus the incident vector beam to a very small focal point, so as to realize the output of high energy density beam. Finally, the focused beam is guided to the three-dimensional motion platform 12. The three-dimensional motion platform 12 plays an important role in this experiment, which can accurately control the position and motion trajectory of the beam in three-dimensional space, so as to realize the precise machining and manipulation of the target material or sample. Through the cooperation of the optical path layout and the optical elements, the experimental system can efficiently complete the whole process from the generation of the vector beam to the focusing and application.

[0060] From the perspective of the optical path structure, the application only adds two devices (a quarter-wave plate and a vortex wave plate) to the traditional Gaussian femtosecond machining system to realize vector machining, so as to output a vector beam coupled by different polarization states and topological charges at the machining end, which is simple and efficient.

[0061] From the perspective of the principle of vortex light, the modulation of the vector beam is introduced into the laser machining system, and the characteristics (different polarization and phase) of the vector beam are used to bring new understanding to femtosecond laser material machining.

[0062] From the perspective of laser machining, the hollow annular energy distribution of the vortex beam is fully utilized to reduce the energy size of the central region of the beam. Compared with the traditional Gaussian femtosecond machining, the hollow annular energy distribution of the vortex beam is beneficial to reduce the internal stress of the machined material substrate.

[0063] The above scheme is only a description of a preferred example, but is not limited thereto. In the implementation of the application, appropriate replacement and / or modification can be made according to the needs of the user.

[0064] Although the embodiments of the application have been disclosed as above, they are not limited to the applications listed in the specification and the embodiments. They can be fully applied to various fields suitable for the application. Additional modifications can be easily realized by those skilled in the art. Therefore, the application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A femtosecond laser vector processing method based on a vortex beam, characterized in that, The application relates to a femtosecond laser vector processing system and a processing method thereof. S1, a polarization beam splitter divides the incident femtosecond laser pulse beam into P light and S light, and completes preliminary polarization state regulation; S2, the polarization state of the femtosecond laser is dynamically regulated by controlling the angles of a half-wave plate and a quarter-wave plate; S3, the femtosecond laser is pulse-modulated and coupled by a vortex wave plate to convert the femtosecond laser into a vortex beam with a predetermined topological charge and polarization state; S4, based on a preset processing path, a three-dimensional motion system is used to adjust the position of a workpiece to be processed, and vector scanning processing of the vortex beam on the surface of the workpiece is completed; In S3, the cross-sectional energy of the vortex beam presents a hollow ring distribution, and the size of the hollow is related to the topological charge; In S3, the conversion efficiency of the vortex wave plate is higher than 90%, and the topological charge of the vortex wave plate is any one of 1, 2, 3 and 4; In S2, the phase delay accuracy of the half-wave plate and the quarter-wave plate is better than 0.1 degrees, and the material of the half-wave plate and the quarter-wave plate is a crystal material with high optical transmittance and low absorption; In S2, the polarization state of the femtosecond laser is combined and regulated by adjusting the angles of the half-wave plate and the quarter-wave plate; The combination regulation includes linear polarization, circular polarization, elliptical polarization and phase regulation. The application further relates to a femtosecond laser vector processing system, which comprises: A laser light source module for providing a femtosecond laser pulse beam; A beam regulation module for regulating the polarization state and phase of the femtosecond laser pulse beam; A vortex beam generation module for pulse-modulating the femtosecond laser into a vortex beam with a predetermined topological charge and polarization state; An optical path transmission module for outputting the generated vector vortex beam to a processing position according to a predetermined light path; A vector scanning module for realizing the vector scanning of the vortex beam on the surface of a workpiece according to a preset processing path; The vortex beam generation module is a vortex wave plate. The beam regulation module comprises: A polarization beam splitter for regulating the polarization characteristics of laser light; A half-wave plate and a quarter-wave plate for dynamically adjusting the angles to change the polarization state and phase of the beam; By accurately regulating the relative angle between the direction of the incident linearly polarized light and the fast axis direction of the vortex wave plate, radial polarization and angular polarization can be realized. In S1, the polarization beam splitter is made of an optical crystal material with a polarization splitting efficiency higher than 98%, and the reflectivity of the incident surface and the exit surface of the polarization beam splitter is less than 0.1%; The optical path transmission module comprises: A mirror I for initially guiding the optical path of the vector vortex beam; A beam splitter wedge for separating part of the light beam transmitted by the mirror I to a power meter; A mirror II and a mirror III for guiding the main light path output by the beam splitter wedge to a focusing objective lens; In S4, the positioning accuracy of the three-dimensional motion system is + / - 500 nm, and the repeat positioning accuracy is + / - 50 nm.

Images