CN111618453A - Ultrafast laser cutting method and device for transparent material - Google Patents

Abstract

The invention discloses an ultrafast laser cutting method and device for transparent materials. A semiconductor laser is modulated to provide a pulse train seed laser, which is amplified by a fiber amplifier and then converted into green light by a frequency-doubling crystal. The cutting head focuses on the position to be processed of the transparent material, and forms more than three focusing points inside the material to be processed. By moving the focusing position, the cutting of the transparent material is realized; each laser pulse train includes at least four laser pulses, The pulse width is between 50 and 60 ps, the peak power is greater than 1 MW, and the time between adjacent laser pulses is 10 to 20 ns; the interval between adjacent pulse trains is greater than 100 ns; the broadening and compression of the laser pulse width does not exceed that of the seed laser. 20% of the pulse width. The invention ensures the reliability of the cutting beam, effectively utilizes the residual heat of the previous pulse, ensures the quality of the cutting process, and realizes the cutting of straight lines and various special shapes of materials.

Description

Ultrafast laser cutting method and device for transparent materials

technical field

The invention relates to a laser processing method, in particular to an ultrafast laser cutting method and a device for cutting transparent materials.

Background technique

Glass and sapphire transparent materials have become an indispensable part of people's daily life. With the development of economy, the demand for glass products is increasing day by day. In the production industry of glass and sapphire, glass and sapphire processing is a very important part.

Generally speaking, glass and sapphire processing (cold working) mainly includes polishing, cutting, drilling, engraving, edging, etc. In order to realize the purpose of processing the above-mentioned glass and sapphire industrially, the processing methods used in the prior art mainly include mechanical processing methods, chemical processing methods (mainly used for polishing and etching), and high-pressure water jet processing methods (mainly used for cutting and drilling). holes) and laser processing methods. Among them, the laser processing method is far superior to other methods in terms of processing speed and degree of automation.

Usually, the laser processing of glass and sapphire uses a CO ₂ laser with a wavelength of around 10.6μm, and its output power generally needs to reach more than 100W. The processing of glass and sapphire with _CO2 lasers is achieved by the fact that the glass is heated and fractured by the incidence of laser light. Taking the cutting of flat glass as an example, the laser beam emitted by the CO ₂ laser is focused on the flat glass, and the high-power laser causes the glass to be heated and fractured at the focal position of the laser, and the cracks extend to the upper and lower surfaces of the glass to complete the cutting. In the process of thermal cutting, it is usually necessary to use a quenching nozzle to spray cold water or cold air on the cutting track to crack the glass. This method has low cutting accuracy and is difficult to process complex graphics.

Glass and sapphire can be laser processed using nanosecond pulsed lasers to achieve better processing results than _CO lasers. Unlike conventional CO ₂ lasers, this nanosecond laser uses micro-blasting to achieve glass processing. Also taking the cutting of flat glass as an example, the 3D scanning galvanometer can make the focus of the laser move in the vertical direction. Where the laser focus passes, the glass will be blasted in the order of microns, and this tiny damage is in the vertical direction. Superimposed on top to achieve higher precision cutting. This nanosecond laser also has some drawbacks in glass and sapphire processing. The chipping after nanosecond laser processing is generally larger than 50 microns, but in many applications, the chipping is required to be less than 20 microns.

To achieve laser processing levels of less than 20 microns, ultrafast laser processing can be employed. The picosecond laser pulse is focused to the position to be processed of the transparent material, and the processing of the transparent material is realized by moving the focusing position. During processing, the laser beam is focused on the lower surface of the transparent material to be processed, and the processing is carried out according to the set trajectory and the focusing point is gradually raised to realize the processing of the transparent material from bottom to top. The moving focus position can be realized by scanning galvanometer, and the output laser is focused by the focusing lens to the position to be processed of the transparent material after the scanning galvanometer, so that the transparent material is removed in the order of microns, and the focal point is moved by the scanning galvanometer. position, so that the removal point is superimposed on the area to be processed to achieve processing. During the specific processing, the laser beam is focused on the lower surface of the transparent material to be processed, and the processing is carried out according to the set trajectory and the focusing point is gradually raised to realize the processing of the transparent material from bottom to top. Such ultrafast laser processing has no bevels. However, the processing speed of this processing method is relatively slow.

The fastest processing speed is the ultrafast laser Bessel cutting method. However, picosecond free-space solid-state lasers are generally used for Bessel cutting. Picosecond free-space solid-state lasers are inconvenient to manufacture, have poor reliability, poor beam quality and high prices.

Therefore, it is very meaningful to find a new ultrafast picosecond laser for fast and low-cost processing of transparent materials.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an ultrafast laser cutting method for transparent materials, so as to overcome the problem of limited processing in the prior art and improve the precision and speed of laser transparent material processing.

Another object of the present invention is to provide a transparent material cutting device for realizing the processing method.

In order to achieve the above purpose of the invention, the technical solution adopted in the present invention is: an ultrafast laser cutting method for transparent materials, which is modulated by a semiconductor laser to provide a pulse train seed laser with a wavelength between 1020 nm and 1090 nm, and the seed laser is output. The energy of the laser is amplified by a fiber amplifier. After the laser is output from the fiber, it is converted into a green light with a wavelength between 510 and 545 nanometers by a frequency-doubling crystal. In the processing position, more than three focal points are formed inside the material to be processed, and the transparent material can be cut by moving the focal position;

Wherein, each laser pulse train includes at least four laser pulses, the pulse width of each laser pulse is between 50 and 60ps, the peak power of the pulse is greater than 1MW, and the time between adjacent laser pulses in the pulse train is 10～20ns; the interval time between adjacent pulse trains is greater than 100ns;

The ultrafast laser beam output by the laser only uses a fiber amplifier for energy amplification. From the seed light to the fiber output, the laser pulse width broadening and compression does not exceed 20% of the seed laser pulse width.

In the above technical solution, the pulse output laser is an ultrafast green laser with a wavelength between 510 and 545 nanometers. The output pulse train, each pulse train includes at least four laser pulses, the pulse width is between 50 ~ 60ps, the peak power of the pulse is greater than 1MW, and the time between each laser pulse in each pulse train is 10 ~ 20ns, The interval time between bursts is greater than 100ns. The first pulse acts on the material to microcrack the material and increase the temperature of the surrounding material. The second pulse arrives and further rapidly increases the temperature of the surrounding material, increasing the length of the microcracks, before the heat of the surrounding material is diffused. The third pulse can use the residual heat of the previous two pulses to effectively increase the length of the microcrack, and so on, this pulse train can greatly increase the length of the microcrack. At the same time, the Bezier cutting head can generate multiple focal points in the material, for example more than three focal points. When the microcracks at different focal points are connected together, the processed material will produce microcracks from top to bottom, thereby realizing cutting.

During laser processing, thermal diffusion takes time levels of microseconds, but subsequent pulses typically arrive in the tens of nanoseconds. A typical pulse interval for a pulse train is on the order of ten nanoseconds, much less than the microsecond time required for thermal diffusion. Therefore, the residual heat from the previous pulse can be used efficiently.

In a preferred technical solution, the number of laser pulses in each laser pulse train is 4-50.

More preferably, the number of laser pulses in each laser pulse train is 4-15.

In the above technical solution, the transparent material is one of glass, crystal material, semiconductor and plastic.

In the above technical solution, the cutting may be vertical cutting or angled cutting.

In order to achieve another purpose of the present invention, the present invention provides an ultrafast laser cutting device for transparent materials, including a laser generating device, a light steering assembly, an optical head, and a working platform, and a three-dimensional motion mechanism is arranged between the optical head and the working platform. , the laser generating device is an ultrafast pulse train laser, the ultrafast pulse train laser is mainly composed of a semiconductor laser, a fiber amplifier, a collimator and a frequency doubling crystal, and the semiconductor laser provides a wavelength between 1020 nanometers and 1090 nanometers. The pulse train seed laser between the two parts; the optical head is a Bessel cutting head; the pulse train seed laser emitted by the semiconductor laser is amplified by the fiber amplifier, and then enters the collimator to output an ultrafast pulse train laser, which is then multiplied by a multiplier. The frequency crystal is converted into green light, which is guided into the Bessel cutting head by the light steering component, and more than three focal points are formed inside the processed material on the working platform.

In the above technical solution, a frame is fixed above the working platform, the plane where the working platform is located is the X-Y plane, the Z-axis is perpendicular to the X-Y plane, the laser generating device is located on the frame, and the front side of the frame is provided with an X-axis. The movement module, the moving part of the X-axis movement module is provided with a Z-axis movement module, the Bessel cutting head is fixed on the movement part of the Z-axis movement module, and the working platform has a Y-axis movement mechanism; The assembly consists of 4 total reflection mirrors, of which the first mirror and the second mirror are fixed on the frame to guide the laser beam to the top of the Bessel cutting head, and the third mirror and the fourth mirror are arranged on the Z-axis motion module. On the moving part, turn the laser beam into a vertical downward direction and enter the Bezier cutting head. Thus, the third lens, the fourth lens, the Bessel cutting head,

In the above technical solution, each laser pulse train includes at least four laser pulses, the pulse width of each laser pulse is between 50 and 60ps, the peak power of the pulse is greater than 1MW, and the interval between adjacent laser pulses in the pulse train is between 50 and 60ps. The time between adjacent pulse trains is 10-20ns; the interval time between adjacent pulse trains is greater than 100ns.

Due to the application of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art:

1. The present invention uses a fiber amplifier to cooperate with a Bessel cutting head to ensure the reliability of the cutting beam. At the same time, by limiting the time between adjacent laser pulses in the pulse train, the waste heat of the previous pulse is effectively utilized, thereby ensuring the quality of the cutting process;

2. The laser output wavelength of the present invention is 510nm-545nm, so the diameter of the focused spot is small, which can achieve more precise laser processing;

3. The present invention forms a three-dimensional processing space through the reasonable cooperation of the light steering component and the motion mechanism, and realizes the cutting of straight lines and various special-shaped shapes of the material through the combined motion of the three axes.

Description of drawings

1 is a schematic diagram of a structural framework of an ultrafast pulse train laser in an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of an embodiment of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and embodiment, the present invention is further described:

Embodiment 1: Referring to Figure 2, an ultrafast laser cutting device for transparent materials includes an ultrafast pulse train laser, a light steering assembly, a Bessel cutting head, and a working platform. The transparent material to be processed is placed on the working platform. superior.

As shown in Figure 1, in the ultrafast pulse train laser, the ultrafast pulse train seed laser is composed of a semiconductor laser, a multi-stage or single-stage fiber amplifier, a collimator, and a frequency-doubling crystal are provided. The pulse train seed laser between 1090 nanometers is amplified by a fiber amplifier and then enters the collimator, and then converted into green light with a wavelength between 510 and 545 nanometers by a frequency-doubling crystal, and outputs an ultrafast pulse train laser. Wherein, each laser pulse train includes at least four laser pulses, the pulse width of each laser pulse is between 50 and 60ps, the peak power of the pulse is greater than 1MW, and the time between each laser pulse in each pulse train is It is 10-20ns, the interval time between pulse trains is greater than 100ns, and the number of laser pulses in each laser pulse train is 4-50. The ultrafast laser beam output by the laser only uses a fiber amplifier for energy amplification. From the seed light to the fiber output, the laser pulse width broadening and compression does not exceed 20% of the seed laser pulse width.

In this embodiment, a three-dimensional motion mechanism is provided, which is structured as follows: a frame is fixed above the working platform, the plane where the working platform is located is the X-Y plane, the Z axis is perpendicular to the X-Y plane, and the ultrafast pulse train laser is located on the frame. , the direction of the laser light is the side of the frame.

There is an X-axis motion module on the front side of the frame, a Z-axis motion module is arranged on the moving part of the X-axis motion module, the Bessel cutting head is fixed on the moving part of the Z-axis motion module, and the working platform has Y-axis motion mechanism.

The light steering assembly consists of 4 45° total reflection mirrors, of which the first mirror 1 and the second mirror 2 are fixed on the frame to guide the laser beam emitted from the side to the horizontal front of the laser, the third mirror 3 and the second mirror are fixed on the frame. The four mirrors 4 are arranged on the moving parts of the Z-axis motion module, wherein the third mirror 3 converts the horizontal leftward laser beam into a forward beam, and the fourth mirror 4 is located just above the Bessel cutting head, so that the laser The beam turns straight down and enters the Bezier cutting head.

The pulse train laser beam passes through the Bessel cutting head to form more than three focal points inside the processed material on the working platform, and realizes the straight line and various special-shaped cutting of the material through the combined motion of the three axes.

Claims (8)

1. An ultrafast laser cutting method for transparent materials, which is modulated by a semiconductor laser to provide a pulse train seed laser with a wavelength between 1020 nanometers and 1090 nanometers, and the laser output from the seed laser is energy-amplified by a fiber amplifier. It is characterized in that: after the laser is output from the optical fiber, it is converted into green light with a wavelength between 510 and 545 nanometers by a frequency-doubling crystal, and the above-mentioned green laser pulse train is focused by the Bessel cutting head to the position to be processed of the transparent material. More than three focus points are formed inside the material, and the transparent material can be cut by moving the focus position; Wherein, each laser pulse train includes at least four laser pulses, the pulse width of each laser pulse is between 50 and 60ps, the peak power of the pulse is greater than 1MW, and the time between adjacent laser pulses in the pulse train is 10～20ns; the interval time between adjacent pulse trains is greater than 100ns; The ultrafast laser beam output by the laser only uses a fiber amplifier for energy amplification. From the seed light to the fiber output, the laser pulse width broadening and compression does not exceed 20% of the seed laser pulse width. 2 . The ultrafast laser cutting method for transparent materials according to claim 1 , wherein the number of laser pulses in each laser pulse train is 4-50. 3 . 3 . The ultrafast laser cutting method for transparent materials according to claim 2 , wherein the number of laser pulses in each laser pulse train is 4-15. 4 . 4. The ultrafast laser cutting method for transparent material according to claim 1, wherein the transparent material is one of glass, crystal material, semiconductor and plastic. 5. An ultrafast laser cutting device for transparent materials, comprising a laser generating device, a light steering assembly, an optical head, and a working platform, and a three-dimensional motion mechanism is arranged between the optical head and the working platform, and is characterized in that: the laser generating The device is an ultrafast pulse train laser. The ultrafast pulse train laser is mainly composed of a semiconductor laser, a fiber amplifier, a collimator and a frequency doubling crystal. The semiconductor laser provides a pulse train with a wavelength between 1020 nanometers and 1090 nanometers. Seed laser; the optical head is a Bessel cutting head; the pulse train seed laser emitted by the semiconductor laser is amplified by a fiber amplifier, and then enters a collimator to output an ultrafast pulse train laser, which is then converted into green by a frequency-doubling crystal The light is guided into the Bessel cutting head by the light turning component, and forms more than three focal points inside the processed material on the working platform. 6. The ultrafast laser cutting device for transparent materials according to claim 5, wherein a frame is fixedly arranged above the working platform, and the plane where the working platform is located is the X-Y plane, and the Z axis is perpendicular to the X-Y plane , the laser generating device is located on the frame, the front side of the frame is provided with an X-axis motion module, the moving part of the X-axis motion module is provided with a Z-axis motion module, and the Bessel cutting head is fixed on the Z-axis motion On the moving parts of the module, the working platform has a Y-axis motion mechanism; the light steering assembly consists of 4 total reflection mirrors, of which the first mirror and the second mirror are fixed on the frame to guide the laser beam to the Bessel Above the cutting head, the third lens and the fourth lens are arranged on the moving parts of the Z-axis motion module, so that the laser beam turns to a vertical downward direction and enters the Bessel cutting head. 7 . The ultrafast laser cutting device for transparent materials according to claim 5 , wherein each laser pulse train includes at least four laser pulses, and the pulse width of each laser pulse is 50-60 ps. 8 . In between, the peak power of the pulse is greater than 1MW, the time between adjacent laser pulses in the pulse train is 10-20ns, and the interval time between adjacent pulse trains is greater than 100ns. 8 . The ultrafast laser cutting device for transparent materials according to claim 5 , wherein the number of laser pulses in each laser pulse train is 4-50. 9 .

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