CN107565371A - A kind of subpulse laser generation method based on double Q-regulating techniques - Google Patents

Abstract

A sub-pulse laser generation method based on double Q-switching technology refers to the use of double Q-switching technology. In the process of modulating laser pulse output by low repetition frequency Q-switching switch, high repetition frequency Q-switching switch is used to modulate again, and then multiple sub-pulse lasers are obtained. Pulse laser output. The invention is simple in structure and easy to operate, and can be applied to the field of laser material processing. Multiple sub-pulses are applied to the workpiece, which becomes the continuous action of laser sub-pulses, which reduces or eliminates the interference of plasma on the laser processing process, and greatly improves the material efficiency. machining accuracy.

Description

A sub-pulse laser generation method based on double Q-switching technology

technical field

The invention belongs to the field of laser technology, and in particular relates to a sub-pulse laser generation method based on double Q-switching technology, and the adopted device is a solid-state laser device.

Background technique

In recent years, laser processing technology has achieved rapid development. Laser processing has the characteristics of non-contact, and also has the advantages of high processing precision, small deformation of the processing object, and low processing cost. In the process of laser processing, the plasma caused by high peak power laser greatly affects the transmission of laser energy to the workpiece: (1) The absorption and consumption of laser beam energy increases when passing through the plasma, and the effective energy transmitted to the workpiece decreases accordingly . (2) The negative lens effect of the plasma causes the laser beam to produce a deflection angle after passing through the plasma, which affects the focusing state of the laser beam on the workpiece surface.

At present, the control methods of photoinduced plasma mainly include laser swing method, external electromagnetic field control method, auxiliary gas blowing method, etc. ⁽¹⁾ . The laser swing method can obtain welds with a larger depth ratio, but this method is not easy to control in actual operation. The external electromagnetic field control method refers to controlling the plasma by using an external electromagnetic field. The method is simple and the cost is low, but it is rarely used in practice and needs further inspection. Although the method of blowing auxiliary gas can control the plasma, this method has strict requirements on the position, angle and pressure of the side blowing gas.

Contents of the invention

The invention provides a sub-pulse laser generation method based on double Q-switching technology. The method uses a double Q-switching device to Q-switch the laser, and uses a high-repetition-frequency The Q-switching switch is then modulated to modulate the laser pulse into multiple sub-pulses.

When it acts on the workpiece, it becomes a continuous action of laser sub-pulses, which can effectively reduce or eliminate the plasma phenomenon generated when a giant pulse laser acts on the workpiece.

The purpose of the present invention is to overcome the shortcomings of the plasma generated by the high peak power laser in the current laser processing process, resulting in a decrease in laser processing efficiency, and decompose a laser pulse into multiple sub-pulse sequences, which can reduce or eliminate the impact of photoinduced plasma on the laser. Interference during processing.

The technical solutions adopted are:

A sub-pulse laser generation method based on double Q-switching technology, comprising the following steps:

Firstly, a giant pulse with a wide pulse width (20-50 nanoseconds) is generated by low repetition frequency Q-switching, and then the generated giant pulse is modulated by high-repetition frequency Q-switching, and finally the laser pulse is modulated into multiple sub-pulses.

The repetition frequency of the low repetition frequency Q-switching switch is 100-1kHz, and the repetition frequency of the high repetition frequency Q-switching switch is 200MHz-500MHz.

Its advantages are:

Two Q-switching switches are used to form a double-Q-switching technology. The double-Q-switching technology double-modulates the laser light emitted by the laser rod, so as to obtain multiple sub-pulse laser outputs. The invention has simple structure, low manufacturing cost, easy operation in industrial application, and can be widely used in the field of laser processing. Multiple sub-pulses are applied to the workpiece, which becomes continuous action of laser sub-pulses, reducing or eliminating the effect of plasma on laser processing. The interference generated in the process greatly improves the processing accuracy of the material.

Description of drawings

Fig. 1 is a schematic structural diagram of Embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of Embodiment 2 of the present invention.

Figure 3 is a low repetition frequency Q-modulated output pulse waveform diagram.

Figure 4 is a low repetition frequency and high repetition frequency dual Q-modulated output pulse waveform diagram.

detailed description

Laser Q-switching refers to the use of a certain method to make the resonator in a state of high loss and low Q value at the beginning of pumping. At this time, the threshold of laser oscillation is very high, and even if the number of particle density inversions accumulates to a high level, no oscillation will occur. . When the particle density inversion number reaches its peak value, the Q value of the cavity is suddenly increased, which will cause the gain of the laser medium to greatly exceed the threshold value, resulting in extremely rapid oscillation. At this time, the energy of the particles stored in the metastable state will be quickly converted into the energy of photons, and the photons will grow at a very high rate like an avalanche, and the laser can output a giant laser pulse with high peak power and narrow width ^{( 2)} .

Double Q-switching technology double-modulates the laser pulse. During the Q-switching output process of the low-repetition-frequency Q-switch 2, the high-repetition-frequency Q-switch 5 is used for secondary modulation, and the low-repetition-frequency Q-switch 2 modulates the output laser The pulse is subdivided, thereby modulating the laser pulse into multiple sub-pulses.

(1) Liu Kun, Liu Jinhe, Zhou Chang, et al. Control of photoplasma in laser deep penetration welding (J). Thermal Processing Technology, 2007,36(23):86-88.

(2) Zhou Bingkun. Laser Principles (M). Beijing: National Defense Industry Press, 2007.

Example 1

As shown in Figure 1, a sub-pulse laser generation method based on double Q-switching technology includes the following steps: turn on the power switch, slowly increase the pumping voltage when the double Q-switching switch is not turned on, and fine-tune the first total mirror 1 And the output mirror 6 makes the output spot in the best state.

Next, turn on the low repetition frequency Q-switch drive 7 to drive the low repetition frequency Q-switch 2. At this time, the output laser pulse shape is shown in FIG. 3 .

If at the same time, the high repetition frequency Q-switching switch drive 8 is synchronously turned on by the synchronous trigger 3 to provide a high repetition frequency driving signal to drive the high repetition frequency Q-switching switch 5, the shape of the output laser pulse is as shown in Figure 4 as a plurality of output laser beams. Pulse waveform diagram. Therefore, through the double Q-switching technology composed of low repetition frequency and high repetition frequency, that is, during the Q-switching laser pulse output process of the low repetition frequency Q switch 2, the high repetition frequency Q switch 5 is modulated again, and the laser pulse can be modulated into multiple sub-pulses, thereby obtaining multiple sub-pulse laser outputs.

A sub-pulse laser generation method based on double Q-switching technology. A sub-pulse laser based on double Q-switching technology, including a first total reflection mirror 1, a low repetition rate Q-switch 2, a high repetition rate Q-switch 5, a laser Rod 4, output mirror 6, low repetition rate Q-switch drive 7, high repetition rate Q-switch drive 8 and synchronous flip-flop 3, all of these devices are known devices.

Laser rod 4 can adopt Nd:YAG laser rod.

Low repetition frequency Q-switching and high repetition frequency Q-switching constitute double Q-switching, the first total reflection mirror 1 and output mirror 6 constitute a laser resonator, and the laser with a wavelength of 1064nm oscillates and outputs in the resonator.

The first total reflection mirror 1 is a concave reflection mirror.

The synchronous trigger 3 is connected to the low repetition frequency Q-switch drive 7 and the high repetition frequency Q-switch drive 8 to realize synchronous triggering and delay control of the low repetition frequency drive and the high repetition frequency drive.

Example 2

Embodiment 2 is basically the same as embodiment 1 in terms of specific implementation, the difference is that embodiment 2 further adopts cavity emptying technology. Turn on the low repetition frequency Q-switch drive 7 to drive the low repetition-frequency Q-switch 2 to work, so that the low repetition-frequency Q-switch 2 modulates the giant pulse laser. Simultaneously open the high repetition frequency Q-switching switch drive 8 synchronously by synchronous trigger 3 and provide the high repetition frequency driving signal to drive the high repetition frequency Q-switching switch 5, the high repetition frequency Q-switching switch 5 is in open state, the low repetition frequency Q-switching switch 2 The modulated laser pulse is subdivided, so that the laser pulse is modulated into multiple sub-pulses. Since the high repetition frequency Q-switching switch 5 will make the Q-switching crystal have Bragg diffraction effect under the high repetition frequency driving signal, all operating power basically diffracts When the first shot level is reached, the propagation direction of the multiple sub-pulse lasers obtained will change and enter the third total reflection mirror 9, and then be reflected by the third total reflection mirror 9 to the fourth reflection mirror 10 according to the incident light path, thus resulting in All the light energy in the resonant cavity formed by the second total reflection mirror 11 and the third total reflection mirror 9 is quickly poured out of the cavity from the cavity, and finally multiple sub-pulse laser outputs are obtained.

A sub-pulse laser based on double Q-switching technology adopted by the sub-pulse laser generation method based on double Q-switching technology, the laser includes a second total reflection mirror 11, a laser rod 4, a low repetition rate Q-switching switch 2, a high repetition The Q-switch 5, the third total mirror 9, the low repetition frequency Q-switch driver 7, the high repetition frequency Q-switch driver 8, the synchronous trigger 3 and the fourth total mirror 10 are all known devices.

The third total reflection mirror 9 is a concave reflection mirror with a radius of curvature of 1 meter, and the fourth reflection mirror 10 and the second reflection mirror 11 are plane reflection mirrors.

The high repetition frequency Q switch 5 is obliquely placed in the laser cavity at the Bragg diffraction angle, and the synchronous trigger 3 is connected to the low repetition frequency Q switch driver 7 and the high repetition frequency Q switch driver 8 to realize low repetition frequency drive and high repetition frequency Driven synchronous trigger and delay control.

Claims (7)

1. A sub-pulse laser generation method based on double Q-switching technology, is characterized in that comprising the following steps: first produces giant pulse by low repetition frequency Q-switching, secondly modulates the giant pulse produced by high repetition-frequency Q-switching, Finally, the laser pulse is modulated into multiple sub-pulses. 2. A sub-pulse laser generation method based on double Q-switching technology according to claim 1, characterized in that it comprises the following steps: low repetition frequency Q-switching adopts low repetition frequency Q-switching switch (2), high repetition frequency modulation Q adopts high repetition frequency Q-switching switch (5). 3. A sub-pulse laser generation method based on double Q-switching technology according to claim 1, characterized in that it includes the following steps: it also includes a resonant cavity, and the resonant cavity includes a first total reflection mirror (1) and an output mirror ( 6). 4. A sub-pulse laser generation method based on double Q-switching technology according to claim 1, characterized in that it includes the following steps: it also includes a resonant cavity, and the resonant cavity includes a third all-mirror (9) and a second all-mirror mirror (11). 5. A sub-pulse laser generation method based on double Q-switching technology according to claim 4, characterized in that it comprises the following steps: the high repetition rate Q-switching switch (5) is obliquely placed in the resonant cavity at a Bragg diffraction angle. 6. A sub-pulse laser generation method based on double Q-switching technology according to claim 1, characterized in that it comprises the following steps: low repetition rate Q-switching and high repetition rate Q-switching are controlled by a synchronous trigger (3) , to realize synchronous triggering and delay control of low repetition rate drive and high repetition rate drive. 7. A kind of sub-pulse laser generation method based on double Q-switching technology according to claim 1, it is characterized in that comprising the following steps: low repetition frequency Q-switching repetition frequency is 100-1kHz, high repetition frequency Q-switching repetition frequency is 200MHz-500MHz.