Femtosecond laser vector processing method and system based on vortex beam

Abstract

The invention discloses a femtosecond laser vector processing method and system based on a vortex beam, and relates to the technical field of femtosecond laser processing, and the method comprises the steps that S1, a polarization splitting prism divides an incident femtosecond laser pulse beam into P light and S light, and preliminary polarization state regulation and control are completed; s2, dynamically regulating and controlling the femtosecond laser of which the polarization state is regulated and controlled by controlling the angles of the half-wave plate and the quarter-wave plate; s3, pulse modulation and coupling are carried out on the dynamically regulated femtosecond laser through a vortex wave plate, so that the femtosecond laser is converted into a vortex light beam with a preset topological charge number and a polarization state; and S4, the position of the workpiece to be machined is adjusted based on a preset machining path, and vector scanning machining of the vortex light beams on the surface of the workpiece is completed. Hollow annular energy distribution of the vortex light beam is fully utilized, so that the energy of a light beam central area is reduced, the energy distribution of the light beam on the cross section is optimized, and material processing is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of femtosecond laser processing, and more particularly to a femtosecond laser vector processing method and system based on a vortex beam. Background Art

[0002] With the rapid development of modern industry, the manufacturing industry is placing increasingly higher demands on processing technology, and the complexity and precision requirements for processing objects are constantly increasing. Traditional laser processing technology is gradually exposing its limitations when it comes to complex surfaces and high-precision processing tasks. For example, in fields such as aerospace, precision machinery, and microelectronics, the processing accuracy requirements for complex shaped parts are extremely high, and traditional laser processing technology often struggles to meet these demands. When processing complex surfaces, problems such as insufficient processing accuracy, poor surface quality, and low processing efficiency are prone to occur.

[0003] At the same time, vortex beams, a new type of beam with a unique spiral phase structure, are emerging in the field of micro-nanofabrication due to their superior performance in light field manipulation. The spiral phase structure of vortex beams enables precise control of the light field, including the beam's intensity distribution, phase distribution, and polarization state. This precise light field manipulation capability enables vortex beams to achieve more refined processing effects in micro-nanofabrication. For example, in the fields of micro-nanostructure manufacturing, nanomaterial processing, and biomedical micro-nanodevice manufacturing, vortex beams have shown great potential. They can achieve high-precision processing of micro-nanoscale materials while maintaining high processing efficiency, bringing new development opportunities to the field of micro-nanofabrication.

[0004] However, despite the many advantages of vortex beams in the field of micro-nano processing, there are still some problems that need to be solved in the current femtosecond laser vector processing systems based on vortex beams. First, the lack of processing flexibility is a prominent problem. Existing femtosecond laser vector processing systems often require tedious optical path adjustments and parameter optimization when processing workpieces with complex shapes, which not only increases the preparation time and cost of processing, but also limits the processing efficiency of the system. Secondly, equipment complexity and cost are also key issues that limit 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 systems based on vortex beams in complex processing tasks, and hinders them from playing a greater role in modern manufacturing. Summary of the Invention

[0005] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0006] In order to achieve these objectives and other advantages of the present invention, a femtosecond laser vector processing method based on a vortex beam is provided, comprising: S1, polarization beam splitter prism splits the incident femtosecond laser pulse beam into P light and S light, completing the preliminary polarization state control; S2, by controlling the angles of the half-wave plate and the quarter-wave plate, the femtosecond laser after polarization state control is dynamically controlled; S3, pulse modulating and coupling the dynamically controlled femtosecond laser through a vortex wave plate to convert the femtosecond laser into a vortex beam with a predetermined topological charge and polarization state; S4. Based on the preset processing path, the position of the workpiece is adjusted using a three-dimensional motion system to complete the vector scanning processing of the vortex beam on the workpiece surface; Among them, 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.

[0007] Preferably, in S1, the polarization beam splitter prism is made of an optical crystal material with a polarization beam splitting efficiency higher than 98%, and the reflectivity of the incident surface and the output surface of the polarization beam splitter prism is less than 0.1%.

[0008] 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 materials of the half-wave plate and the quarter-wave plate are selected to be crystal materials with high optical transmittance and low absorption.

[0009] Preferably, in S2, the polarization state of the femtosecond laser is controlled by adjusting the angles of the half-wave plate and the quarter-wave plate; The combined control includes linear polarization, circular polarization, elliptical polarization and phase control.

[0010] 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.

[0011] Preferably, in S4, the positioning accuracy of the three-dimensional motion system is ±500 nm, and the repeat positioning accuracy is ±50 nm.

[0012] A system, applied to the femtosecond laser vector processing method based on a vortex beam, comprising: A laser light source module that provides a femtosecond laser pulse beam; A beam control module for controlling the polarization state and phase of a femtosecond laser pulse beam; A vortex beam generation module is formed by modulating a femtosecond laser pulse into a vortex beam with a predetermined topological charge and polarization state; Outputting the generated vector vortex light beam to the optical path transmission module of the processing position along a predetermined optical path; A vector scanning module that realizes the processing action of the vortex beam on the workpiece surface according to the preset processing path; Wherein, the vortex beam generating module is a vortex wave plate.

[0013] Preferably, the beam control module includes: Polarization beam splitter prism for regulating laser polarization characteristics; Half-wave plates and quarter-wave plates can change the polarization state and phase of the light beam by dynamically adjusting the angle.

[0014] Preferably, the optical transmission module includes: Reflector I for initially guiding the optical path of the vector vortex beam; Split the beam transmitted by reflector I into the beam splitter wedge of the power meter; The main light path output by the beam splitter wedge is guided to the reflector II and reflector III of the focusing objective lens.

[0015] The present invention includes at least the following beneficial effects: The present invention aims to provide a processing system that does not require complex optical elements and equipment, so it has the advantages of low equipment complexity and controllable costs, and through beam control and high-precision scanning technology, it can achieve efficient, fast and high-quality femtosecond laser processing.

[0016] The present invention provides a processing method, which is significantly different from a traditional Gaussian beam in that, within the cross section of the vortex beam, its complex amplitude distribution presents a characteristic spiral phase wavefront, and the phase value presents an azimuth-related periodic variation around the optical axis. This topological phase structure produces a definite phase singularity, and its physical manifestation is that the light field intensity at the optical axis position has a zero-value singularity. Determined by this spiral phase distribution, a distinct annular structure feature is generally observed in the far-field or near-field intensity distribution of the vortex beam. Specifically, along the radial direction, the beam intensity presents a zero value at the center of the optical axis; as the radial coordinate distance increases, the intensity undergoes a monotonically increasing process, reaches a peak intensity at a certain radius, and then presents a non-monotonic decreasing trend as the radial distance further increases. The hollow annular energy distribution of the vortex beam is fully utilized to significantly reduce the energy size in the central area of the beam, optimize the energy distribution of the beam in the cross section, and is more conducive to material processing.

[0017] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1Schematic diagram of the overall architecture of the femtosecond laser vector processing system based on vortex beam in the present invention; Among them, there are femtosecond laser-1, polarization beam splitter prism-2, half-wave plate-3, quarter-wave plate-4, vortex wave plate-5, reflector I-6, power meter-7, spectroscopic wedge-8, reflector II-9, reflector III-10, focusing objective lens-11, and three-dimensional motion platform-12. DETAILED DESCRIPTION

[0019] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0020] A femtosecond laser vector processing system and method based on a vortex beam comprises the following steps: Step 1: Guide the femtosecond laser pulse beam to the polarization beam splitter prism. When the femtosecond laser pulse beam is incident on the polarization beam splitter prism, the prism will split it into two beams according to the polarization direction of the light: one beam is linearly polarized light (P light) parallel to the incident plane, and the other beam is linearly polarized light (S light) perpendicular to the incident plane. By rationally designing the optical path, it is ensured that the P light is effectively transmitted to the subsequent optical path system, while the S light is ignored or guided to other directions. This process realizes the preliminary control of the laser polarization state, ensuring that the subsequent optical path can receive and process linearly polarized light, laying the foundation for subsequent dynamic control of the polarization state and beam modulation; In actual applications, the polarization beam splitter prism in this step uses high-precision optical crystal materials, and its polarization beam splitting efficiency is higher than 98%. The incident and exit surfaces of the polarization beam splitter prism are treated with special anti-reflection coatings, and the reflectivity is less than 0.1%.

[0021] Step 2. After completing the preliminary polarization state control, the polarization state of the laser is further dynamically controlled by rotating half-wave plates and quarter-wave plates. Half-wave plates and quarter-wave plates are common optical phase delay plates that can control the polarization state of the light beam by changing their relative rotation angles. A half-wave plate can convert linear polarization into linear polarization in any direction, while a quarter-wave plate can convert linear polarization into circular polarization or elliptically polarized light. By precisely controlling the rotation angles 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 linear polarization to circular polarization, or from right-handed circular polarization to left-handed circular polarization. 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; In actual applications, the rotating half-wave plate and quarter-wave plate in this step are combined to control the polarization state of the laser to achieve multiple polarizations such as linear polarization, circular polarization and elliptical polarization. Therefore, the materials of the half-wave plate and quarter-wave plate are selected to be crystal materials with high optical transmittance and low absorption rate, and the rotating half-wave plate and quarter-wave plate are both manufactured using high-precision optical processing technology, and their phase delay accuracy is better than 0.1 degree.

[0022] Step three: Use a vortex wave plate to modulate the femtosecond laser pulse and convert it into a vortex beam with a specific topological charge and polarization state. By selecting a suitable vortex wave plate, the topological charge of the vortex beam (i.e., the helicity of the beam) can be precisely controlled, thereby achieving complex modulation of the beam. At the same time, combined with the polarization state regulated in the previous step, the characteristics of the vortex beam can be further optimized, allowing it to play a greater role in subsequent processing. This step is the core link of the entire patented technology. Through the modulation of the vortex wave plate, the transformation from an ordinary femtosecond laser pulse beam to a vortex beam with special physical properties is achieved, providing a key beam form for subsequent vector scanning processing; In practical applications, the polarization state of the vortex beam in this step is generated by coupling the polarization state controlled in step 2 and the topological charge of the vortex wave plate, wherein the topological charge of the vortex wave plate is one of 1, 2, 3, and 4, and the conversion efficiency of the vortex wave plate is higher than 90%. In addition, the surface of the vortex wave plate is also covered with a special protective film, which has high optical transmittance and good scratch resistance, and can effectively extend the service life of the vortex wave plate while reducing the problem of beam quality degradation caused by surface damage.

[0023] Step 4. Use a high-precision three-dimensional motion system to achieve vector scanning of the vortex light beam on the surface of the workpiece according to the preset processing path. The three-dimensional motion system is usually composed of a high-precision motor drive device and a precise positioning platform, which can achieve precise control of the light beam in three-dimensional space. During the processing, the processing path is pre-designed according to the shape of the workpiece and the processing requirements, and it is input into the motion control system. The motion system accurately moves the workpiece or the light beam according to the preset path, so that the vortex light beam is scanned on the surface of the workpiece according to the predetermined trajectory. Since the vortex light beam has a unique phase distribution and polarization state, it can produce special processing effects during the processing process, such as higher processing accuracy, more complex structure processing capabilities or more uniform energy distribution. Through vector scanning processing, high-precision and high-efficiency processing of the workpiece surface can be achieved, meeting the strict requirements for processing quality in the fields of micro-nano manufacturing and precision processing; In actual applications, the positioning accuracy of the high-precision three-dimensional motion system in this step is ±500nm, and the repeatability is ±50nm.

[0024] like Figure 1As shown, a femtosecond laser vector processing system based on vortex beam includes: a laser light source module, a beam control module, an optical path transmission module, a vortex beam generation module and a vector scanning module; The laser light source module uses a femtosecond laser 1 to provide stable femtosecond laser pulses, providing an energy basis for subsequent processing; The beam control module controls the polarization state of the laser by introducing a rotating polarization beam splitter prism 2, a half-wave plate 3, and a quarter-glass 4, thereby achieving dynamic control of the polarization state and phase of the beam. The vortex beam generation module uses a vortex glass slide 5 to modulate the femtosecond laser pulse into a vortex beam with a specific topological charge and polarization state; The optical transmission module includes: A reflector I6 for initially guiding the optical path of the vector vortex beam; Split the light beam transmitted by the reflector I into the beam splitter wedge 8 of the power meter 7; Guide the main light path output by the beam splitter wedge to the reflector II 9 and reflector III 10 of the focusing objective lens 11; The vector scanning module adopts a high-precision three-dimensional motion system to realize vector scanning of the vortex beam on the workpiece surface according to the preset processing path.

[0025] Example: As the core light source, the femtosecond laser 1 provides highly stable femtosecond laser pulses, laying a solid energy foundation for subsequent processing. To precisely control the polarization properties of the laser, a polarization beam splitter 2 is introduced. Its primary function is to convert the incident laser pulse into linearly polarized light (P light) and direct it to the subsequent optical path system. To dynamically control the polarization state and phase of the light beam, a rotating half-wave plate 3 and a quarter-wave plate 4 are introduced. By precisely controlling the rotation angles of these two wave plates, the polarization state of the light beam can be flexibly changed, enabling conversions from linear polarization to circular polarization, to elliptical polarization, and other polarization states. This dynamic control capability provides a high degree of flexibility and adaptability for experiments, and can meet the precise polarization state requirements for different processing needs.

[0026] Furthermore, by adjusting the topological charge 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 a vortex wave plate with a topological charge of m=1 as an example, by precisely controlling the relative angle between the direction of the incident linear polarized light and the fast axis direction of the vortex wave plate surface, the output of radial polarization and angular polarization states can be achieved. Specifically, when the direction of the incident linear polarization light is parallel to the 0° fast axis direction of the vortex wave plate, the system will output a vector beam in a radial polarization state. This polarization state 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 linear polarization light is perpendicular to the 0° fast axis direction of the vortex wave plate, the system will output a vector beam in an angular polarization state. In this case, the polarization direction is distributed in a rotational manner 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 a variety of options for subsequent optical processing and manipulation.

[0027] Furthermore, after the vector beam is generated, it first passes through reflector 6 for preliminary guidance. The main optical path then enters beam splitter wedge 8, which separates a portion of the beam from the main path and guides it to power meter 7. Power meter 7 monitors laser power in real time, providing critical data support for power control and stability analysis during the experiment. After passing through beam splitter wedge 8, the main optical path continues along its predetermined path, passing through reflectors 9 and 10. These two reflectors further adjust the beam's propagation direction, ensuring that it accurately reaches focusing objective lens 11. Focusing objective lens 11, a key component in the optical system, primarily focuses the incoming vector beam to a very small focal point, thereby achieving a high-energy-density beam output. Finally, the focused beam is guided to a three-dimensional motion platform 12. The three-dimensional motion platform 12 plays a crucial role in this experiment, precisely controlling the beam's position and trajectory in three-dimensional space, enabling precise processing and manipulation of the target material or sample. Through the synergy of optical path layout and optical elements, the experimental system can efficiently complete the entire process from vector beam generation to focusing and application.

[0028] From the perspective of optical path structure, the present invention achieves vector processing by adding only two devices (a quarter-wave plate and a vortex wave plate) to the traditional Gaussian laser femtosecond processing system, thereby outputting vector beams with different polarization states and coupled topological charges at the processing end. The structure is simple and efficient.

[0029] From the perspective of vortex light principles, the present invention introduces vector light beam modulation into the laser processing system and utilizes the characteristics of vector light beams (differences in polarization and phase) to bring new insights into femtosecond laser material processing.

[0030] From a laser processing perspective, this invention leverages the hollow annular energy distribution of the vortex beam to reduce the energy in the beam's center. Compared to traditional Gaussian laser femtosecond processing, this hollow annular energy distribution helps reduce internal stress in the substrate being processed.

[0031] The above solution is only an illustration of a preferred embodiment, but is not limited thereto. When implementing the present invention, appropriate replacements and / or modifications can be made according to user needs.

[0032] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the present invention. Further modifications will be readily apparent to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims

1. A femtosecond laser vector processing method based on vortex beam, characterized in that: include: S1, polarization beam splitter prism splits the incident femtosecond laser pulse beam into P light and S light, completing the initial polarization state control; S2, dynamically controlling the polarization-controlled femtosecond laser by controlling the angles of the half-wave plate and the quarter-wave plate; S3, pulse modulating and coupling the dynamically controlled femtosecond laser through a vortex wave plate to convert the femtosecond laser into a vortex beam with a predetermined topological charge and polarization state; S4. Based on the preset processing path, the position of the workpiece is adjusted using a three-dimensional motion system to complete the vector scanning processing of the vortex beam on the workpiece surface; Among them, 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 number.

2. The femtosecond laser vector processing method based on vortex beam according to claim 1, characterized in that: In S1, the polarization beam splitter prism is made of an optical crystal material with a polarization beam splitting efficiency higher than 98%, and the reflectivity of the incident surface and the output surface of the polarization beam splitter prism is less than 0.1%.

3. The femtosecond laser vector processing method based on vortex beam according to claim 1, characterized in that: In S2, the phase delay accuracy of the half-wave plate and the quarter-wave plate is better than 0.1 degree, and 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.

4. The femtosecond laser vector processing method based on vortex beam according to claim 1, characterized in that: In S2, the polarization state of the femtosecond laser is controlled by adjusting the angles of the half-wave plate and the quarter-wave plate; The combined control includes linear polarization, circular polarization, elliptical polarization and phase control.

5. The femtosecond laser vector processing method based on vortex beam according to claim 1, characterized in that: 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.

6. The femtosecond laser vector processing method based on vortex beam according to claim 1, characterized in that: In S4, the positioning accuracy of the three-dimensional motion system is ±500 nm, and the repeat positioning accuracy is ±50 nm.

7. A system, applied to the femtosecond laser vector processing method based on vortex beam according to any one of claims 1 to 6, characterized in that: include: A laser light source module that provides a femtosecond laser pulse beam; A beam control module for controlling the polarization state and phase of a femtosecond laser pulse beam; A vortex beam generation module is formed by modulating a femtosecond laser pulse into a vortex beam with a predetermined topological charge and polarization state; Outputting the generated vector vortex light beam to the optical path transmission module of the processing position along a predetermined optical path; A vector scanning module that realizes the processing action of the vortex beam on the workpiece surface according to the preset processing path; Wherein, the vortex beam generating module is a vortex wave plate.

8. The system according to claim 7, wherein: The beam control module includes: Polarization beam splitter prism for regulating laser polarization characteristics; Half-wave plates and quarter-wave plates can change the polarization state and phase of the light beam by dynamically adjusting the angle.

9. The system according to claim 7, wherein: The optical path transmission module includes: Reflector I for initially guiding the optical path of the vector vortex beam; Split the beam transmitted by reflector I into the beam splitter wedge of the power meter; The main light path output by the beam splitter wedge is guided to the reflector II and reflector III of the focusing objective lens.

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