JP2925024B2 - Discharge excitation method and discharge excitation device for laser oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a discharge excitation method for a laser oscillator such as a gas laser oscillator.

(Prior Art) In a gas laser oscillator using a gas such as CO ₂ gas as a laser medium, the laser medium is often excited by electric discharge.

There are two types of discharge excitation: continuous excitation by continuous waves (CW excitation) and pulse excitation by pulse waves. It is known that pulse excitation has a higher saturation value for laser output discharge power (discharge current) than continuous excitation. Have been. Therefore, usually, when the pulse peak of the laser output is set to be high, the discharge power, that is, the injection power is increased.

(Problems to be Solved by the Invention) The pulse peak of the laser output is increased by the increase of the discharge power. However, the laser output is increased even if the discharge power is increased to a predetermined value or more due to thermal saturation of the discharge part. Only increasing the trigger-like peak value tends to reduce the average output value. In the case of a pulse wave having a laser output having only a high peak value, an effect due to a high pulse peak does not occur due to a shortage of energy of a laser beam in metal processing, and the processing time cannot be reduced.

The present inventors conducted an experimental study in view of the above-mentioned problems, and found that the laser output was changed under the influence of the discharge length, and the discharge length was changed by the discharge power and the discharge tube of the laser gas as the laser medium. Within an appropriate range determined by the flow velocity at the flow rate, the required laser output, etc., the longer the discharge length, the greater the tendency of thermal laser output saturation at high discharge power, but the higher the efficiency of laser oscillation becomes. In contrast, it was found that the shorter the discharge length, the smaller the maximum efficiency of laser oscillation, but the smaller the tendency of thermal laser output saturation at high discharge power.

The present invention provides a discharge excitation method for a laser oscillator that enables efficient laser oscillation over a wide discharge power width based on the above-described viewpoint.

[Constitution of the Invention] (Means for Solving the Problems) In view of the above problems, the present invention relates to a method for exciting a laser medium, which discharges a laser medium, using a laser having a high peak pulse waveform. This is a discharge excitation method for a laser oscillator that increases the discharge length when output is required as compared to when continuous waveform laser output is required.

(Operation) In the discharge excitation method of the laser oscillator according to the present invention,
When high peak pulse waveform laser output is required,
As the discharge length is longer than when a continuous waveform laser output is required, the maximum efficiency of laser oscillation increases,
In response to this, a laser output of a high peak pulse is obtained, and for example, when a laser output of a continuous waveform is required, the maximum discharge power of thermal laser output saturation increases due to the short discharge length, When a laser output with a normal pulse waveform is required or during CW oscillation, a high average laser output can be obtained.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a discharge excitation device for a laser oscillator according to the present invention. The laser oscillator has a laser discharge tube 1 composed of a glass tube or the like, and a total reflection mirror 3 as an optical resonator is provided at one end of the laser discharge tube 1.
The other end is provided with an output mirror 5 constituted by a semi-reflective mirror.

The laser discharge tube 1 constitutes a laser gas chamber 7 extending in the axial direction, that is, in the left-right direction in the drawing.
A laser gas inlet 9 is provided at one end, and a laser gas outlet 11 is provided at the other end.

A needle-shaped anode electrode 13 is provided at the laser gas inlet 9 of the laser discharge tube 1. Laser discharge tube 1
A ring-shaped cathode electrode 15 is provided at a position separated by a first predetermined value with respect to the anode electrode 13, and a second predetermined value larger than the first predetermined value with respect to the anode electrode 13 is provided. A ring-shaped second cathode electrode 17 is provided at a separated position. The anode electrode 13 is always conductively connected to a power supply device 19 for discharging, whereas the first cathode electrode 15 and the second cathode electrode 17 are connected to a switching circuit.
21 allows one of them to be selectively conductively connected to the power supply 19.

The switching circuit 21 is switched by the control device 23, and when a laser output having a high peak pulse waveform is required, the switching position is switched to a switching position where the second cathode electrode 17 is electrically connected to the power supply device 19, At times, for example, when a laser output of a normal pulse waveform or a continuous wave is required, the first cathode electrode 15 is switched to a switching position where it is electrically connected to the power supply device 19.

According to the above-described configuration, when a laser output having a high peak pulse waveform is required, a discharge is performed between the anode electrode 13 and the second cathode electrode 17, and the discharge length in this case is the anode electrode 13 And the first cathode electrode 15 is longer than in the case where a discharge is performed, and accordingly, the maximum efficiency of laser oscillation is increased.

On the other hand, when a laser output of a normal pulse waveform is required or a continuous wave laser output, that is, at the time of CW oscillation, discharge is performed between the anode electrode 13 and the first cathode electrode 15, and the discharge in this case is performed. The length is shorter than when the discharge is performed between the anode electrode 13 and the second cathode electrode 17, and the maximum efficiency of the laser oscillation is correspondingly reduced. , The maximum power of laser output saturation increases, and a high average laser output can be obtained.

FIG. 2 shows the case where the discharge length is short, that is, the anode electrode 13
And when the discharge is performed between the first cathode electrode 15 and the discharge power when the discharge length is long, that is, when the discharge is performed between the anode electrode 13 and the second cathode electrode 17. The relationship with the laser output is shown for each of continuous excitation and pulse excitation. In the graph of FIG. 2, the solid line shows the characteristic at the time of continuous excitation, and the broken line shows the characteristic at the time of pulse excitation. The characteristics at the time of pulse excitation indicate the peak value (peak value) of the laser output.

As can be seen from the graph shown in FIG. 2, when the discharge length is long, the tendency of thermal laser output saturation at a large discharge power is large, but the maximum efficiency of laser oscillation is high. On the other hand, when the discharge length is short, the maximum efficiency of laser oscillation is small, but it can be understood that the tendency of thermal laser output saturation at a large discharge power is small.

When the discharge length is long, the laser output at high power decreases during continuous excitation, but the peak value of the laser output during pulse excitation increases. Since the output is less likely to saturate, the maximum efficiency of laser oscillation is low.However, continuous excitation produces a higher laser output than when the discharge length is longer, and pulse excitation has a rectangular normal pulse waveform. It will be appreciated that the output is obtained.

Therefore, at the time of laser output of a normal pulse that does not require a laser output of a high peak pulse, or at the time of CW oscillation, it is only necessary to perform a discharge with a short discharge length, thereby, for example, as shown in FIG. A laser output that does not include the peak value of the high peak pulse over the discharge power width is obtained.

On the other hand, when a pulse output with a high peak pulse waveform is required, the discharge may be performed with a long discharge length. In this case, a high peak pulse waveform having a high peak output as shown in FIG. Laser output can be obtained. A laser output with a high peak pulse waveform can reduce the piercing time during laser processing, which is a significant reduction in the total processing time because the piercing time accounts for a large percentage of the total processing time. become. This is even more effective, especially in the case of pulse excitation using a high-frequency pulse with a short duty ratio, because a laser output having a high pulse peak waveform is continuously obtained at short intervals.

In pulse excitation, a laser output having a high peak pulse waveform when the discharge power is large is obtained.
It is considered that the average discharge energy in the pulse discharge is lower than that in the case of the continuous discharge, so that the laser gas temperature does not become high.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to this, and various embodiments can be made within the scope of the present invention. It will be clear to those skilled in the art.

[Effects of the Invention] As can be understood from the above description of the embodiment, according to the discharge excitation method of the laser oscillator according to the present invention, when a laser output having a high peak pulse waveform is required, a laser output having a continuous waveform is required. When the discharge length is longer than required, the maximum efficiency of laser oscillation is increased and a laser output with a high peak pulse is obtained. The maximum discharge power of typical laser output saturation increases, and when a laser output with a normal pulse waveform is required, or a high average laser output can be obtained during CW oscillation, a wide discharge power width can be obtained from these facts. Efficient laser oscillation is performed over the entire area.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a discharge excitation device for a laser oscillator according to the present invention, and FIG. 2 shows the relationship between discharge power and laser output when the discharge length is short and long. FIG. 3 is a waveform diagram showing a laser output waveform at the time of pulse excitation when the discharge length is short, and FIG. 4 is a waveform diagram showing a laser output waveform at the time of pulse excitation when the discharge length is long. DESCRIPTION OF SYMBOLS 1 ... Laser discharge tube, 7 ... Laser gas chamber 13 ... Anode electrode 15 ... First cathode electrode 17 ... Second cathode electrode 19 ... Power supply device, 21 ... Switching circuit 23 ... Control device

Claims (1)

(57) [Claims] In a discharge excitation method of a laser oscillator for exciting a laser medium by discharge, when a laser output having a high peak pulse waveform is required, a discharge is performed as compared with a case where a continuous waveform laser output is required. A discharge excitation method for a laser oscillator, characterized by increasing the length.