CN116551195A - Femtosecond vortex laser processing device and method - Google Patents

Abstract

The invention provides a femtosecond vortex laser processing device and method, which relate to the field of femtosecond laser processing, including a fixture, a focusing mechanism, an adjustment mechanism, and a laser for outputting vortex laser. The output end of the laser is facing the input end of the adjustment mechanism, and the adjustment The output end of the mechanism faces the input end of the focusing mechanism, and there is a spiral-shaped processing area between the output end of the focusing mechanism and the fixture; the fixture is connected with a driving mechanism, which can drive the fixture to reciprocate axially along the processing area; for the current workpiece The problem of low efficiency and difficult to control the precision of laser surface treatment, using vortex laser for surface treatment of cylindrical workpiece, collimating and focusing the vortex laser to form a vortex linear processing area, the workpiece is set in Axial movement is carried out in the processing area, and the burrs and other structures on the outer peripheral surface are scraped by using the vortex-shaped vortex laser, so as to achieve the effect of surface leveling and improve the surface quality of the workpiece material.

Description

A femtosecond vortex laser processing device and method

technical field

The invention relates to the field of femtosecond laser processing, in particular to a femtosecond vortex laser processing device and method.

Background technique

The surface roughness of the workpiece will have varying degrees of influence on the material's coating, thermal conductivity and contact resistance, reflection and radiation performance, resistance to liquid and gas flow, and current flow on the conductor surface.

Laser processing is non-contact processing, and the energy and moving speed of the high-energy laser beam can be adjusted, so a variety of processing purposes can be achieved. It can process a variety of metals and non-metals, especially materials with high hardness, high brittleness and high melting point, such as processing cylindrical single crystal optical fibers from several microns to tens of microns. Laser processing has great flexibility and is mainly used for cutting, surface treatment, welding, marking and drilling. Laser surface treatment includes laser trimming, laser phase transformation hardening, laser cladding, laser surface alloying and laser surface fusion. Among them, when the laser is used to treat the surface of the workpiece to improve the surface roughness, due to the small range of action of the laser after focusing, the efficiency of large-area surface treatment is low; when adjusting the position of the workpiece or the laser source, to When adjusting the action position, limited by the adjustment accuracy of the position change, the working position and the focus position are offset, resulting in deviations in processing. Unlike cutting in the laser cutting process, the relative position accuracy of the focus point and the workpiece during surface treatment requires high accuracy. This also leads to the need for a high-precision position adjustment structure when performing surface treatment by laser, and it is difficult to effectively guarantee the efficiency and accuracy of laser surface treatment.

Contents of the invention

The purpose of the present invention is to provide a femtosecond vortex laser processing device and method for the defects in the prior art. The vortex laser is used to process the surface of a cylindrical workpiece, and the vortex laser is collimated and focused to form a vortex. In the spiral-shaped processing area, the workpiece is nested in the processing area to move axially, and the burrs and other structures on the outer peripheral surface are scraped by using the spiral-shaped vortex laser, so as to achieve the effect of surface leveling and improve the workpiece material. Surface Quality.

The first object of the present invention is to provide a femtosecond vortex laser processing device, which adopts the following scheme:

It includes a fixture, a focus mechanism, an adjustment mechanism and a laser for outputting vortex lasers. The output end of the laser faces the input end of the adjustment mechanism, the output end of the adjustment mechanism faces the input end of the focus mechanism, and a vortex line is arranged between the output end of the focus mechanism and the fixture. Shaped processing area; the clamp is connected with a driving mechanism, which can drive the clamp to reciprocate axially along the processing area.

Further, the focusing mechanism includes a focusing lens, and the focusing lens is coaxially distributed with the processing area.

Further, the processing area coincides with the trajectory of the vortex laser emitted by the focusing lens, the axis of the processing area is coaxial or parallel to the axis of the clamping part of the fixture, and the axial projection of the processing area is circular.

Further, the driving mechanism includes a piezoelectric platform, the clamp is mounted on the piezoelectric platform, and the piezoelectric platform has at least one degree of freedom along the axial direction of the processing area.

Further, the adjustment mechanism includes a half-wave plate, a polarization splitter prism, a collimator lens group and a plane mirror arranged in sequence along the propagation path of the vortex laser, and the plane mirror is arranged at an angle with the propagation path of the vortex laser to change the propagation path of the vortex laser. direction.

The second object of the present invention is to provide a femtosecond vortex laser processing method, using the femtosecond vortex laser processing device as described above, comprising the following steps:

Adjust the focus mechanism, adjustment mechanism and laser, so that the vortex laser output by the laser passes through the adjustment mechanism, focus mechanism and forms a processing area in sequence;

The fixture clamps the workpiece and drives the workpiece to move, so that the processing area is coaxially sleeved outside the workpiece, and the vortex laser forms a vortex linear processing area on the outer ring of the workpiece;

The workpiece reciprocates along the axial direction of the processing area to remove the part of the outer circumference of the workpiece that is in contact with the vortex laser.

Further, after the workpiece is clamped by the fixture, the workpiece is driven to move by the driving mechanism, so that the workpiece is arranged coaxially with the processing area.

Further, the parameters of the laser, adjustment mechanism and focus mechanism are changed to adjust the diameter and axial length of the processing area.

Further, the focusing mechanism focuses the vortex laser on the processing area, and the clamp drives the workpiece to reciprocate relative to the processing area.

Further, the fixture is arranged at a distance from the processing area, and the workpiece is cylindrical.

Compared with prior art, the advantages and positive effects that the present invention has are:

(1) In view of the low efficiency and difficult control of the precision of the surface treatment of the workpiece by laser, the surface treatment of the cylindrical workpiece is carried out by using the vortex laser, and the vortex laser is collimated and focused to form a vortex line In the processing area, the workpiece is nested in the processing area to move axially, and the burrs and other structures on the outer peripheral surface are scraped off by using the vortex-shaped vortex laser, so as to achieve the effect of surface leveling and improve the surface quality of the workpiece material.

(2) Use the focusing mechanism to form a processing area between the focusing mechanism and the fixture. The processing area is in the same vortex line shape as the vortex laser path, that is, a vortex line-shaped cutting action area is formed. Contact this vortex line-shaped processing The workpiece in the area will be removed by the vortex laser to remove the surface structure of the workpiece and improve the surface accuracy.

(3) The processing area is in the shape of a spiral line, which can be set on the outer ring of the cylindrical workpiece. When the workpiece and the processing area move axially relative to each other, the processing area can form a cutting line, and the cutting surface is formed under the action of the movement. On the outer ring of the workpiece, the structure outside the processing area is cut off to achieve leveling of the workpiece surface.

(4) Compared with the traditional laser surface treatment method, the process of forming the traditional action point into the action surface, using the vortex laser to form the vortex-shaped action line, and the process of forming the action surface again during the processing process, using the workpiece The movement forms contact with the vortex laser, which improves the surface treatment efficiency of the workpiece. During the entire processing process, there is no need to adjust the laser source and optical path structure, only the position of the workpiece needs to be adjusted to keep the vortex laser active area stable and improve the processing efficiency. precision.

(5) Targeted surface processing of cylindrical workpiece materials. When adjusting the parameters of the same batch of workpieces, it is enough to adjust the parameters of the corresponding adjustment mechanism, laser, and focus mechanism without changing the structure of the device in a large range. Guarantee the working accuracy before and after adjustment.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is the schematic diagram of the optical path principle of the laser in the embodiment 1 or 2 of the present invention;

Fig. 2 is a schematic diagram of the principle of a femtosecond vortex laser processing device in Embodiment 1 or 2 of the present invention.

In the figure, 1. Laser; 2. Adjustment mechanism; 3. Focusing mechanism; 4. Fixture; 5. Processing area; 6. Workpiece.

Detailed ways

Example 1

In a typical embodiment of the present invention, as shown in FIGS. 1-2 , a femtosecond vortex laser processing device is provided.

The femtosecond vortex laser processing device shown in Figure 2 can use the laser 1, the adjustment mechanism 2 and the focusing mechanism 3 to output the vortex laser, and focus it in a certain area to form a vortex linear processing area 5, and the workpiece 6 moves To the processing area 5 and form a relative movement with the processing area 5, the contact position between the workpiece 6 and the processing area 5 is affected by the vortex laser, and thus is cut by the vortex laser, so as to remove the raised part of the surface of the workpiece 6 and reduce the workpiece. 6 Surface roughness, the purpose of improving the surface quality of workpiece 6.

Combining Figure 2 and Figure 1, the femtosecond vortex laser processing device mainly includes a laser 1, an adjustment mechanism 2, a focusing mechanism 3 and a fixture 4. The laser 1 outputs a vortex laser, and the vortex laser passes through the adjustment mechanism 2 and the focusing mechanism 3 in turn. , a processing area 5 is formed between the clamp 4 and the focusing mechanism 3. The processing area 5 is in the shape of a vortex line formed during the propagation of the vortex laser. The clamp 4 and the processing area 5 can move relatively, so that the clamped on the clamp 4 The workpiece 6 held and the processing area 5 form a relative movement, and the vortex laser is used to act on the workpiece 6 to remove the circumferential material to meet the needs of the processing process.

For the propagation path of the vortex laser, as shown in Figure 2, the output end of the laser 1 faces the input end of the adjustment mechanism 2, and the output end of the adjustment mechanism 2 faces the input end of the focusing mechanism 3. Under the action of the focusing mechanism 3, the vortex laser flows from the focusing mechanism 3 is output from the output end, and a processing area 5 is formed in the area between the focusing mechanism 3 and the clamp 4, and the processing area 5 is in the shape of a spiral line.

As shown in Figure 1, the laser 1 is used to output a vortex laser. The vortex laser is a beam with a helical wavefront structure, which has a cylindrically symmetric propagation property. The vortex center of the beam is a dark nucleus, and in the propagation process Also keep the center light intensity at 0.

The vortex beam has the characteristics of a ring-shaped distribution of light intensity, and the center light intensity is zero. When capturing particles, the particles can be imprisoned in the central area of the beam with zero light intensity. At this time, the particles will not be irradiated by light, so that they can Maintain the activity of microparticles (cells). In this embodiment, the femtosecond vortex laser is used to process the cylindrical material with rough surface by utilizing the ring-shaped distribution of light intensity of the vortex laser and the unique property that the central intensity is 0, while removing the surface material of the workpiece 6 without destroy the internal structure.

As shown in Figure 1, the laser 1 is a femtosecond vortex beam laser 1, and the steps of generating femtosecond vortex laser are: using LD pump source, Tm:YLF crystal as gain medium, and SESAM as mode-locking element to build folded The cavity, and the femtosecond Hermitian Gaussian beam is obtained by rotating the output mirror by the off-axis pumping method, and the femtosecond vortex laser is obtained by the cylindrical lens converter.

In this embodiment, a set of relevant parameters of laser 1 is given for processing a cylindrical single crystal fiber of several microns to tens of microns, the pump source is LD with a wavelength of 792nm, and the Tm:YLF crystal size is 3*3* 7mm ³ , the doping concentration is 3at.%, the modulation depth of the SESAM modulation element is 1.2%, and the saturation flux is 70μJ/cm ² .

Meanwhile, in this embodiment, the wavelength of the femtosecond vortex laser is 1.9 μm, the pulse width is 650 fs, and the laser power used in the experiment is 1 W.

In addition, in other embodiments, the parameters of the femtosecond vortex laser can be adjusted according to the configuration of the propagation optical path, the material of the workpiece 6, etc., such as adjusting the laser power, pulse width, wavelength, etc., to meet actual processing needs.

As shown in Figure 2, the adjustment mechanism includes a half-wave plate, a polarizing beamsplitter prism, a collimator lens group, and a plane mirror arranged in sequence along the propagation path of the vortex laser. The plane mirror is arranged at an angle with the propagation path of the vortex laser to change the direction of propagation.

Among them, the half-wave plate and the polarization beam splitter are used to adjust the output femtosecond vortex laser power; the collimator lens group is used as a collimating and focusing system, which can collimate the output femtosecond vortex laser; the plane mirror can choose a 45° mirror , which can control the movement of the femtosecond vortex laser on the X-Y plane.

During the processing of the workpiece 6 , since the positions of the fixture 4 and the workpiece 6 need to be adjusted, the fixture 4 is also connected with a driving mechanism, which can drive the fixture 4 to reciprocate axially along the processing area 5 . Wherein, the clamp 4 can be a chuck, the driving mechanism includes a piezoelectric platform, the clamp 4 is installed on the piezoelectric platform, and the piezoelectric platform has at least one degree of freedom along the axial direction of the processing area 5 . The focusing mechanism 3 includes a focusing lens, which is coaxially distributed with the processing area 5, and is used to focus the femtosecond vortex laser so that the femtosecond vortex laser focuses on the processing area 5; in this embodiment, the focal length of the focusing lens is 100mm.

Combined with Figure 2, the laser power of the femtosecond vortex laser is adjusted after passing through the half-wave plate and the polarization beam splitter; then the laser beam is shaped by the collimation and focusing system; after that, it is focused to the rough surface after passing through the 45° mirror and the focusing lens On the cylindrical material, the 45° mirror is used to control the movement of the femtosecond vortex laser on the X-Y plane, and then focus the laser through the focusing lens. The cylindrical workpiece 6 is fixed on the piezoelectric table through the chuck, and on the piezoelectric platform Driven by the material to move up and down.

As shown in Figure 2, the processing area 5 coincides with the vortex laser trajectory emitted by the focusing lens, the axis of the processing area 5 is coaxial or parallel to the axis of the clamping part of the fixture 4, and the projection of the processing area 5 along the axial direction is circular. The processing area 5 has the same vortex line shape as the vortex laser path, that is, forms a vortex line-shaped cutting action area, and the workpiece 6 that touches the vortex line-shaped processing area 5 will be removed by the vortex laser to achieve workpiece removal. 6 The surface structure can improve the surface precision.

It should be pointed out that the projection of the vortex line in the axial direction is circular, which is suitable for the size of the workpiece 6. The processing area 5 is in the shape of a vortex line and can be sleeved on the outer ring of the cylindrical workpiece 6. When the area 5 moves relative to the axial direction, the processing area 5 can form a cutting line, and form a cutting surface under the action of the movement, acting on the outer ring of the workpiece 6, cutting off the structure outside the processing area 5, and realizing the leveling of the surface of the workpiece 6 .

In the traditional laser surface treatment method, the laser is projected on the surface of the workpiece 6, the action line is formed by relative movement, and then the action surface is formed by superimposing the action line, the processing efficiency is low; in this embodiment, the vortex line is formed by using the vortex laser In the process of re-forming the action surface in the processing process, the movement of the workpiece 6 is used to form contact with the vortex laser, which improves the surface treatment efficiency of the workpiece 6. During the entire processing process, no laser source and optical path structure are required. For adjustment, it is only necessary to adjust the position of the workpiece 6 to keep the vortex laser action area stable and improve the processing accuracy.

Example 2

In another typical embodiment of the present invention, as shown in FIGS. 1-2 , a femtosecond vortex laser processing method is provided.

As shown in Figure 1 and Figure 2, using the femtosecond vortex laser processing device as in Example 1, comprises the following steps:

Adjust the focus mechanism 3, the adjustment mechanism 2 and the laser 1, so that the vortex laser output from the laser 1 passes through the adjustment mechanism 2, the focus mechanism 3 in sequence and forms the processing area 5;

The fixture 4 and the processing area 5 are arranged at intervals, and the workpiece 6 is cylindrical. The fixture 4 clamps the workpiece 6 and drives the workpiece 6 to move, so that the processing area 5 is coaxially sleeved outside the workpiece 6, and the driving mechanism drives the workpiece 6 to move, so that The workpiece 6 is coaxially arranged with the processing area 5;

The focusing mechanism 3 focuses the vortex laser on the processing area 5, and the vortex laser forms a vortex linear processing area 5 on the outer ring of the workpiece 6, and the fixture 4 drives the workpiece 6 to reciprocate relative to the processing area 5;

Change the parameters of the laser 1, the adjustment mechanism 2 and the focus mechanism 3 to adjust the diameter and axial length of the processing area 5;

The workpiece 6 reciprocates axially along the processing area 5 to remove the part of the outer circumference of the workpiece 6 that is in contact with the vortex laser.

In this embodiment, the working process of the laser 1 is as follows: using a LD pump source with a wavelength of 792nm, using a Tm:YLF crystal with a doping concentration of 3at.% and a size of 3*3* ^7mm3 as the gain medium, and using a radius of curvature 100mm input mirror, M ₂ and M ₃ cavity mirrors with a radius of curvature of 200mm, flat mirror output mirror and SESAM mode-locking element to build a folded cavity, use the off-axis pumping method to obtain a femtosecond Hermitian Gaussian beam by rotating the output mirror, and then Using a pair of cylindrical lenses with a focal length of 25mm and a distance of 35.35mm to obtain a femtosecond vortex laser;

After the femtosecond vortex laser passes through the half-wave plate and the polarization beam splitter, the laser power is adjusted; then the laser beam is shaped by the collimation and focusing system; after that, it is focused on the cylindrical material with rough surface after passing through the 45° mirror and the focusing lens in turn , where the 45° mirror is used to regulate the movement of the femtosecond vortex laser on the X-Y plane, and then focus the laser through the focusing lens. The cylindrical workpiece 6 is fixed on the piezoelectric table through the chuck, and is realized under the drive of the piezoelectric platform. Up and down movement of material.

Since the center light intensity of the vortex laser is 0, the light intensity tends to increase first and then decrease to both sides, so the radius of the circle with the strongest light intensity on the intercepted cross section is taken as the spot radius of the vortex beam. Derivation of the light intensity distribution expression of the beam:

Among them, l is the topological charge of the beam, σ is the radius of the spot, which can be considered to represent the Gaussian spot size on the observation plane, r, θ are the polar coordinates of the observation plane, z is the transmission distance, where

After derivation, take the extremum to get the new spot size expression as:

It can be seen from formula (2) that the spot size is related to the size of the topological charge and the transmission distance. Since the collimation system is added after the generated femtosecond vortex laser and the position of the cylindrical workpiece 6 is close to the place where the vortex light is generated, it can be approximately considered here that σ'=σ. Therefore, after the parameters of the resonant cavity are determined, it can be obtained The spot radius at z=0 can be used to calculate the spot size of the vortex beam by using different topological charge values obtained. According to the size of the cylindrical material with rough surface, the parameters of the resonant cavity are constantly adjusted to facilitate the processing of the material.

Targeted surface processing of cylindrical workpiece 6 materials, the same batch of workpieces 6, when parameter adjustment is performed, the parameters of the corresponding adjustment mechanism 2, laser 1, and focus mechanism 3 can be adjusted, and there is no need to change the device on a large scale The structure ensures the working accuracy before and after adjustment.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. The femtosecond vortex laser processing device is characterized by comprising a clamp, a focusing mechanism, an adjusting mechanism and a laser used for outputting vortex laser, wherein the output end of the laser faces to the input end of the adjusting mechanism, the output end of the adjusting mechanism faces to the input end of the focusing mechanism, and a vortex linear processing area is arranged between the output end of the focusing mechanism and the clamp; the fixture is connected with a driving mechanism, and the driving mechanism can drive the fixture to axially reciprocate along the processing area.

2. The femtosecond vortex laser processing apparatus of claim 1 wherein the focusing mechanism comprises a focusing lens coaxially distributed with the processing region.

3. The femtosecond vortex laser processing device as set forth in claim 1, wherein the processing area coincides with the vortex laser track emitted by the focusing lens, the axis of the processing area is coaxial or parallel to the axis of the clamping part of the clamp, and the projection of the processing area along the axial direction is circular.

4. The femtosecond vortex laser processing apparatus of claim 1 wherein the drive mechanism comprises a piezoelectric platform to which the fixture is mounted, the piezoelectric platform having at least one degree of freedom along an axial direction of the processing region.

5. The femtosecond vortex laser processing apparatus according to claim 1, wherein the adjustment mechanism comprises a half wave plate, a polarization splitting prism, a collimating lens group and a plane mirror which are sequentially arranged along a vortex laser propagation path, and the plane mirror is arranged at an angle with the vortex laser propagation path to change the vortex laser propagation direction.

6. A femtosecond vortex laser processing method using the femtosecond vortex laser processing apparatus according to any one of claims 1 to 5, comprising the steps of:

adjusting the focusing mechanism, the adjusting mechanism and the laser to enable vortex laser output by the laser to sequentially pass through the adjusting mechanism and the focusing mechanism and form a processing area;

the clamp clamps the workpiece and drives the workpiece to move, so that the processing area is coaxially sleeved outside the workpiece, and vortex laser forms a vortex linear processing area on the outer ring of the workpiece;

the workpiece axially reciprocates along the processing area, and the part of the outer circumference of the workpiece contacting the vortex laser is removed.

7. The femtosecond vortex laser processing method of claim 6 wherein the workpiece is moved by the driving mechanism after the workpiece is clamped by the clamp so that the workpiece is coaxially arranged with the processing area.

8. The method of claim 6, wherein the laser, adjustment mechanism and focusing mechanism parameters are varied to adjust the diameter and axial length of the processing zone.

9. The method of claim 6, wherein the focusing mechanism focuses the swirling laser light on the processing region and the fixture reciprocates the workpiece relative to the processing region.

10. The method of claim 6, wherein the fixture is spaced from the processing region and the workpiece is cylindrical.