JPS5846688A - Gas laser oscillator - Google Patents

Abstract

PURPOSE:To obtain a compact, high pulse frequency and high pulse output laser oscillator by stabilizing grow discharge through the use of silent discharge as the preliminary ionization means and by utilizing change of discharge characteristic of grow discharge of main discharge due to preliminary ionization. CONSTITUTION:A gradual discharge called silent discharge occurs between the dielectric electrode 9 and anode 1 and cathode 2 when a high current high voltage power source 13 is operated. This discharged current is as low as 1/20 of grow discharge current of the main discharge. In case a DC high current high voltage power source is operated under this condition, grow discharge occurs between the anode 1 and cathode 2 and thereby the discharge portion 6 is generated. When a large pulse discharge power is input by utilizing the characteristic that the grow discharge characteristic changes largely when silent discharge is preliminarily ionized, a high pulse laser output can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas laser oscillator, and particularly to a device for generating pulsed laser oscillation.

A typical laser of this type is the laser optical axis, WL
Since this is a three-axis orthogonal type CO2 laser in which the gas flow directions in the flow discharge path are substantially perpendicular to each other, a conventional example will be described.

Figure 1 is a vertical cross-sectional view of the S-axis orthogonal laser;
It is a sectional view taken along the line in FIG. 1-1. In the figure, (1) is an anode, (2) is a cathode, (3) is a cathode substrate, (4) is a stabilizing resistor, (5) is a DC high voltage power supply, (6) is a discharge excitation part, (
)) is a total reflection mirror, and (8) is a partial reflection mirror.

Next, the operation will be explained. Between the anode (1) and the cathode (2), 002, 12. A laser gas consisting of a mixed gas of He was flowed in the direction of the arrow at a flow rate of several tens of meters per second.

When a DC high voltage (5) is applied, a discharge occurs between the electrodes or a current flows through the stabilizing resistor (4).

The discharge does not shift to an arc, and a gentle glow discharge is maintained. Discharge starter caused by glow discharge (6)
In this case, population inversion occurs between specific vibrational units of 002 molecules in the laser gas, and a total reflection bell (7) occurs between the discharge excitation part (6).
When a partially reflective mirror (8) having an appropriate reflectance is placed facing each other, laser oscillation occurs and a laser beam is emitted from the nine partially reflective mirror (8). Although the laser output increases as the discharge power increases, if the number of cathodes (2) is constant in the case shown in FIG. 1, for example, an increase in the discharge power is equivalent to an increase in the discharge density. From the viewpoint of making the device more compact and lowering costs, it is desirable to increase the discharge density, but if the discharge power is increased beyond a certain level, a high temperature area will be generated locally in the discharge area, and the stabilizing resistor (4) will be damaged. Even if it exists, the discharge will transition to an arc. When the discharge transitions to an arc, laser output is no longer obtained and the degradation of the laser gas increases significantly. For this reason, in laser oscillators.

In order to make the oscillator more compact and to ensure reliability, it is constructed so that the maximum output can be obtained before the discharge transitions to an arc.

By the way, it is a material that has high thermal conductivity when used with laser light.

For example, when performing metal 0 row, thermal energy passes through the material and escapes to the outside, so if the average output is the same, the laser output will vary over 9 hours.

Laser output with a large peak pulse provides better machining energy, machining accuracy, etc.

For this reason, the conventional configuration was as shown in Figure 1.

The output of the DC high voltage power supply (5) was set as the pulse output shown in FIG. 3(a), and the pulsed laser output shown in FIG. 3(b) was obtained.

However, with such a pulsed laser oscillator.

The peak laser output does not exceed the maximum output when the laser output is constant over an hour (continuous oscillation), and if you try to obtain the same average output as in the latter case, increase the number of @poles (2). Therefore, it is necessary to make the 9 oscillator larger.

For example, as shown in FIG. 3(a), if the voltage is applied for half of the pulse power cycle.

In other words, the duty factor is 77 kuta (Dqty Factor).
) = 50%, in order to obtain the same average output as in the case of constant (continuous oscillation) laser output for 9 hours, twice the size and twice the power supply capacity are required. moreover,
In laser excitation using only glow discharge K as shown in Figure 1,
If the rise time of the pulse voltage is short, thermal diffusion is difficult to occur inside the glow discharge, resulting in thermal imbalance and arcing even when the arcing current is below.

For this reason, limitations are placed on the current rise time in such pulsed output laser oscillators.

The frequency of the pulse output was at most several tens of Hg.

On the other hand, in the field of laser processing, the higher the pulse frequency, the better the processing accuracy, processing speed, etc.
Even higher frequencies can be obtained.

Moreover, there was a desire to develop a compact laser device with good operability.

This invention was made in view of the above request.

By using silent discharge as a pre-ionization means, glow discharge is stabilized, and by utilizing changes in the discharge characteristics of glow discharge of main discharge due to pre-ionization, compact, high pulse frequency, and The aim is to provide a pulse output laser oscillator.

This invention was born from deep consideration of the discharge characteristics of a glow discharge as a main discharge when a silent discharge is used as preliminary ionization, so the invention will be described in detail while explaining these discharge characteristics.

FIG. 4 is a vertical sectional view of one embodiment of the present invention, and FIG.
In the cross-sectional view taken from line IV-4 in Figure IV-4, (9) is the dielectric electrode, 0 is the cooling water inlet for cooling this electrode, αD is the cooling water outlet, a is the high voltage terminal, and α is the hot water. This is an AC high voltage power supply for producing silent discharge. Figure 6 is a cross-sectional view of the dielectric electrode (9), (9-1) is an iron pipe, (
9-2) is a dielectric material and glass is usually used. In such a configuration, when the Island High Voltage Power Supply @3 is operated, a gentle discharge called a silent discharge occurs between the dielectric electrode (9) and the anode (11 and cathode (2)). The discharge current is /2G of the glow discharge current of the main discharge explained next.
It is. When the DC high voltage power supply (5) is operated in this state, a glow discharge occurs between the anode +11 and the cathode (2), and a discharge portion (6) as shown in FIG. 5 is generated. When preliminary ionization is performed by silent discharge, the so-called V-1 characteristics of the current and voltage of the glow discharge change greatly.

An example of its characteristics is shown in FIG. The vertical axis is the discharge sustaining voltage V of glow discharge, and the horizontal axis is the glow discharge current 1. The characteristic curve curve in the figure is the v-i characteristic when silent discharge is not performed, and the characteristic curve ■ is when silent discharge is performed steadily ((
'V- when 11 AC high voltage is always applied)
This is one characteristic.

The flat part (constant current characteristic) of characteristic curve 1.1 indicates that a glow discharge is formed, and the part where V rapidly drops as 1 increases indicates that the curve has transitioned to an arc discharge. In the laser device, the maximum operating point is just before the transition to the arc. Characteristic curve I, characteristic curve ■
Comparing these, we can express a silent discharge, and when we pre-ionize it,
It can be seen that the current until it transfers to the arc increases several times, and the sustaining voltage of the glow discharge decreases. By the way, as mentioned earlier, the electric current flows through the glow discharge current stabilizing resistor (4), and its electrical circuit is shown in FIG. In the figure, E is the output voltage of the DC high voltage power supply (5), and 1 is the current flowing in the glow discharge.

(2) represents the discharge sustaining voltage of glow discharge.

It is easy to understand that the following equation holds true for this circuit system.

V==1e-1R The characteristic curve V of this equation is drawn as a broken line in Fig. 7, and the intersection of the characteristic curve ■ and the characteristic curve I is the operating point P1 when silent discharge is not performed. Become. The voltage x current at this operating point P1 becomes the glow discharge power P1,
A laser output corresponding to a power of P1=6KVX2A=+12KW is obtained. However, when silent discharge is performed using the same device (same resistance value R), the operating point follows the characteristic curve ■
and the characteristic curve l intersect at point P2. Discharge power P2B at this time, P2: 5.5KV x 6.
The power of 25A and 634KW, approximately 29 times that of P1, is obtained, and the laser output is also larger than this. Discharge power P
An example of the relationship between and laser output is shown in Figure 8, where at operating point P1, the discharge power is 0.7
A laser output of KW is obtained, and the tri operation is performed at the operating point P2.
A laser output of 5.3 KW is obtained for a discharge power of 34 KW.

As explained above, when silent discharge is used as preliminary ionization, the glow discharge characteristics change greatly, but this invention utilizes this characteristic to input large pulsed discharge power and obtain large pulsed laser output. It is something.

Fig. 10 is a waveform diagram for explaining one embodiment of the present invention, Fig. 10 (-) is an output voltage waveform diagram when the AC high voltage power supply I is pulsed, and Fig. 10 (b) is an output voltage waveform diagram when the AC high voltage power supply I is pulsed. (C) is a waveform diagram of the laser output.

An AC high voltage for producing silent discharge is applied for a certain period of time, paused for a certain period of time, and then fp = frequency is repeated. As mentioned earlier, silent discharge power line main discharge (
The waveform can be easily controlled because the number of glows is small.

When such a voltage is applied, a silent discharge occurs only when a voltage is applied corresponding to the original fp. Therefore, the transition from the operating point P1 to P2 shown in FIG.
If the DC high-voltage power supply is a constant voltage type, the power input changes as shown in Figure 10 (effect), and as a result, the pulsed laser output shown in Figure 10 (C) is obtained.This method Since preliminary ionization is performed by silent discharge, thermal diffusion becomes active and no thermal imbalance occurs inside the glow discharge, so an extremely stable glow can be maintained even if the glow discharge current changes. According to experiments, 9 for example 200
)−le laser gas pressure, the pulse repetition frequency f
p can be up to about 10 KHg.

The example shown in FIG. 10 shows a case where a laser output of about 0.7 KW is obtained even when the silent discharge is at rest, but it depends on the value of the resistor (4).

Since the operating points P1 and P2 in Fig. 7 move, the combination of Figs. 7 and 9 shows that the laser output during this rest period can be adjusted arbitrarily (it can even be set to zero). There is no need to say that.

The above explanation was for the case where the DC high voltage power supply (5) is a constant voltage type, but in another embodiment of the present invention shown in FIG. What I used,
a◆ is a capacitor connected in parallel to the DC high voltage power supply (5).

In a laser oscillator configured in this way.

When a silent discharge is not formed, the terminal voltage of the capacitor I is El, but when a silent discharge is formed, a large glow discharge current flows, so the DC high voltage power supply (5
) alone can no longer supply it (because it is a constant current source),
It is also supplied from the capacitor α4, and a pulsed laser output similar to that shown in FIG. 10(C) can be obtained. Also,
If the capacitance of the capacitor 114 at this time is sufficiently large.

A large current can be supplied during silent discharge formation without any drop in the terminal voltage.

In this embodiment, since the DC power supply (5) is a constant current type, the capacitors 64), ! By the combination of :′.

The maximum current capacity of the DC high voltage power supply (5) may be the average current value of the glow discharge current.

On the other hand, even if the DC high voltage power supply (5) is a constant voltage type, the first
As shown in Figure 2, by connecting between the output side of the choke coil α field and the capacitor ◆, the maximum current capacity of the DC high voltage power supply (5) can be made the value of the glow discharge current. The equipment capacity of the power source can be reduced.

As explained above, if a silent discharge is used as a pre-ionization source in a DC glow discharge, a pulsed laser output can be obtained by using a pulse output as the power source for the silent discharge, and this output is higher than that in the case of glow discharge alone. It becomes 2, -3 times. Moreover, since the silent discharge only needs about 20 times the current of the glow discharge of the main discharge, it is extremely easy to control the silent discharge and the laser pulse output can be easily controlled. Furthermore, since silent discharge is used as preliminary ionization, a stable glow is formed even if the rise of the glow discharge current is accelerated, and the frequency of the laser pulse can be increased by several kilobytes.

In the above embodiment, a DC high voltage that does not generate a glow discharge by itself is applied between the anode and the cathode, and a nozzle-like AC high voltage is applied to the dielectric electrode to generate a silent discharge. We have shown a configuration that uses this as a trigger to generate a glow discharge and output a laser pulse.
Even if it is applied, a similarly large laser output can be emitted in a spiral shape. This state can be understood as corresponding to the state of transition from operating point P1 to P2 in the characteristic diagram of FIG. An anode and a cathode to which a high voltage is applied are arranged in the laser gas flow, and a pulsed AC high voltage is applied to generate a pulsed silent discharge between the anode and the cathode. This device is equipped with a dielectric electrode that generates a glow discharge in a lasing pattern and emits a pulsed laser output between the cathode and the cathode, making it possible to control high-output, high-frequency pulsed laser output with small power control. It has a great effect.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional horizontal gas laser oscillator.
Figure 2 is a cross-sectional view taken along the line ``G'' in Figure 1, Figure 3 (a)
, (b) is a power supply voltage waveform and laser output waveform diagram when a DC high voltage power supply is used as a pulse output, and FIG. 4 is a longitudinal cross-sectional view of an embodiment of the present invention. Figure 5 is a cross-sectional view taken along line ■-v in Figure 4, Figure 6 is a cross-sectional view of the dielectric electrode, Figure 7 is a diagram showing the glow discharge characteristics of this example, and Figure 8 is a diagram of DC glow discharge. An equivalent circuit diagram, FIG. S is a characteristic diagram showing the relationship between discharge power and laser output of this embodiment, and FIG. 10 (,) is an output voltage waveform diagram of the AC high voltage power supply. Figure (b) is a glow discharge power waveform diagram, figure (C) is a laser output waveform diagram, Figure 11 is a circuit diagram of another embodiment of the present invention, and Figure 12 is a circuit diagram of still another embodiment. It is. In the figure, (I) is an Fi anode, (2) is a cathode, (5) is a DC high voltage power supply, (6) is a discharge excitation part, and (9) is a dielectric electrode. (11-1) is an iron pipe, (9-2) is glass, and 1 is an AC high voltage power supply. Note that the same reference numerals in FIG. 9 indicate the same or corresponding parts. Agent Shin Kuzuno - (1 other person) Figure 1 ■ Figure 2 Figure 3 41!1 jl151!1 116I! 1 7th r! IA glow breakdown tA Otsu [A] wi8r! IJ Otsudai el! 1 Discharge power P [to W] Figure 10 i! 111 Figure 5312 Procedural Amendment (Voluntary) Mr. Commissioner of the Patent Office], Indication of Case Patent Application Sho! 16-145679 No. 2, Title of the invention Gas laser generator 3, Relationship to the amended person case Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Representative of Mitsubishi Electric Corporation Hitoshi Katayama Hachibe 4, Agent address: 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo, [Detailed description of the invention in the original subject specification 6, the content of the amendment is] in the second page of the specification. , in lines 17 to 18, ``Does a discharge occur?'' t Corrected ``A discharge occurs, but.'' (2) Same, page 5, line 9, corrected to read ``several tens of HfJ warehouses ``several tens of Hx''. (3) Same, page 10, line 14 r 1oKufJ1r
1oKz,” he corrected. +41 Same, E] Page 2 - Line 219 fJ r Number KH1
J frloKHz,” he corrected. that's all

Claims (3)

[Claims] (1) An anode and a cathode, which are arranged to face each other across the laser gas airflow and to which a high DC voltage is applied; A pulsed silent discharge is generated between the cathode and the cathode. A gas laser oscillator comprising a dielectric electrode that generates a glow discharge of a large current in a pulsed manner between the anode and the cathode to emit a laser output of a large output in a pulsed manner. (2) The gas laser oscillator according to claim 1, comprising a capacitor connected in parallel to the output end of a constant current type high voltage power supply. (3) A gas laser oscillator according to claim 1, comprising a coil connected in series to the output end of a constant voltage type high-voltage power supply, and a capacitor that grounds the output side of this coil.