JPS6034278B2 - Laterally pumped gas laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lateral excitation type gas laser device, and particularly to a pre-ionization method using silent discharge.

A typical example of this type of laser is a triple orthogonal C02 laser in which the laser optical axis, DC glow discharge path, and gas flow direction are substantially perpendicular to each other, so a conventional example will be described.

Figure 1 is a vertical cross-sectional view of the 3-Wing orthogonal laser, and Figure 2 is the 1st cross-sectional view.
In the figure, 1 is an anode, 2 is a cathode, and 3 is a cross-sectional view seen from the 0 line.
is a cathode substrate, 4 is a stabilizing resistor, 5 is a DC high voltage power supply, 6
7 is a total reflection mirror, and 8 is a partial reflection mirror.
Next, the operation will be explained.

A laser gas consisting of a mixed gas of CO2, N2, and He is flowed between the anode 1 and the cathode 2 in the direction of the arrow at a flow rate of several tens of meters per second, and when a DC high voltage 5 is applied, a discharge occurs between the electrodes, but it stabilizes. Since the crab current flows through the resistor 4, the discharge does not change to an arc, and a gentle glow discharge is maintained.
In the discharge excitation part 6 generated by the glow discharge, a population inversion occurs between specific vibrational levels of CO2 molecules in the laser gas, and a total reflection mirror 7 and a partial reflection mirror having an appropriate reflectance are formed with the discharge excitation part 6 in between. 8 are placed facing each other, laser oscillation occurs, and a laser beam indicated by a broken arrow is emitted from the partially reflecting mirror 8. The laser output increases as the discharge power increases, or, for example, as shown in FIG. 1, increasing the discharge power when the number of cathodes 2 is constant is equivalent to increasing the discharge density. It is desirable to increase the discharge density from the viewpoint of making the device more compact and lowering costs, 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 increase.
Even if there is, the discharge will transition to an arc. When the discharge shifts to an arc, laser output can no longer be obtained and the deterioration of the laser gas increases significantly. In order to overcome these difficulties, attempts have been made to increase the discharge density while maintaining the glow discharge by performing preliminary ionization near the glow discharge to help the glow of the main discharge become uniform and stable. ing.

Pre-ionization methods include electron beam, ultraviolet irradiation by pulse discharge, and silent discharge. This invention relates to an improvement in a preliminary ionization method using silent discharge.

First, a conventional example of this method will be explained.

Fig. 3 is a longitudinal cross-sectional view of a horizontally excited gas laser device using a pre-ionization method using silent discharge, and Fig. 4 is a cross-sectional view taken from the line W-W in Fig. 3. 11 is a cooling water inlet for cooling the electrodes, 11 is a cooling water outlet, 12 is a high voltage terminal, and 13 is an AC high voltage power source for producing silent discharge.

FIG. 5 is a cross-sectional view of the dielectric electrode 9, where 9-1 is an iron pipe;
Reference numeral 9-2 is a dielectric material (for example, glass) formed so as to be in close contact with the iron pipe, and is a so-called "housing" electrode. Next, the operation will be explained.

When an AC high voltage is applied to the dielectric electrode 9, a silent discharge occurs between the dielectric electrode 9, the cathode 2, and the anode 1. When an AC high voltage is applied between the anode 1 and the cathode 2 in this state, a glow discharge occurs and a discharge excitation part 6 is formed. It is possible to input ~3 times the power density. According to experiments, it has been found that the power of silent discharge is only about 1/20 of the power of main discharge (glow). In the conventional silent discharge pre-ionization method configured in this way, the cross-sectional shape of the discharge excitation section 6 in the laser gas flow direction is not necessarily optimal for laser oscillation, and efficient oscillation conditions cannot be obtained. Has no drawbacks.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by appropriately connecting a capacitor or coil in a silent discharge circuit, a silent discharge is formed in a desired direction, and thereby the main discharge The shape of the cross section of the discharge excitation part by the glow discharge is optimized for laser oscillation.

FIG. 6 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG.
Figure W - Cross-sectional view seen from the side line, 14 is a metal ground electrode, 1
5 is a capacitor.

Next, the operation will be explained. When a high voltage is applied to the dielectric electrode 9 from the AC high voltage power supply 13, the silent discharge tends to discharge toward the metal parts facing the anode 1, the cathode 2, and the metal ground electrode 14. When an AC high voltage is applied to the anode 1 by the AC high voltage power supply 5, the DC glow discharge tends to discharge toward the opposing metal parts, that is, the cathode 2 and the metal ground electrode 14. Here, the reason why the DC glow discharge does not discharge toward the dielectric electrode 9 is because the dielectric 9-2 exists on the surface and has infinite impedance with respect to the AC voltage. Similarly, in this embodiment, a capacitor 15 is connected between the metal ground electrode 14 and the ground point, and the metal ground electrode 14 when viewed from the anode 1 has infinite impedance to direct current. ing. Therefore, the current flow of the DC glow discharge is formed from the anode 1 to the cathode 2. A silent discharge current is formed from the dielectric electrode 9 toward the anode 1, cathode 2, and metal ground electrode 14. As shown in FIG. 4, when a silent discharge is formed, the direct current glow discharge spreads to that area. Because it discharges even between
The glow discharge spreads to this portion, and a discharge excitation portion 6 is formed that extends to the metal ground electrode 14 as shown in FIG. When such a discharge excitation section 6 is formed, the discharge density becomes uniform in the direction of the discharge gap, and therefore uniform excitation can be obtained, so that the excitation efficiency of laser oscillation is improved compared to the conventional one. As explained above, the main point of this invention is to form a silent discharge between the dielectric electrode 9 and the metal ground electrode 14, but when the value of the resistor 4 is large or the impedance of the AC power source 5 is high, Sometimes, when the voltage becomes small, a strong silent discharge occurs only between the anode 1 and the anode 1. In this case, the coil 16 may be connected between the anode 1 and the ground point as shown in FIG.

FIG. 10 is a cross-sectional view of another embodiment of the present invention, 14-
1 is a metal ground electrode installed upstream of Caesar gas, 14
12 is a metal ground electrode installed downstream, and both are electrically at the same potential. 9-1 is a dielectric electrode installed upstream of the Caesar gas, and 9-2 is a dielectric electrode installed downstream, both of which are at the same potential.

Similar to the embodiment of the invention shown above, a capacitor 5 is connected between the metal ground electrodes 14-1, 14-2 and the ground point, and acts as an infinite impedance to direct current, and prevents direct current glow. It prevents the discharge from flying toward the metal ground electrodes 14--, 14-2, acts as an impedance for alternating current, and acts as a counter electrode for silent discharge. If the silent discharge electrodes are arranged as in this embodiment, as shown in FIG. In some cases, the silent discharge occurs mainly between the dielectric electrode 9 and the cathode 2, and in this case, the effect of the metal ground electrode 14 disappears, and a discharge area of the same shape as the discharge area shown in FIG. A glow discharge is formed. Therefore, the shape of the discharge region is no longer optimal for laser oscillation. When such an electric circuit constant is generated, a coil 16 is connected between the cathode 2 and the ground point as shown in FIG. Since the coil 16 can have a large impedance with respect to AC, that is, the AC high voltage power supply 13, silent discharge mainly occurs between the dielectric electrode 9 and the metal ground electrode 14, as shown in FIG. The same shape of the discharge region as in the above can be obtained, and one suitable for laser oscillation can be obtained. Similarly, for example, if the inductance for wiring in the electric circuit of the cathode 2 is relatively large, the impedance for silent discharge between the dielectric electrode 9 and the anode 1 is more sufficiently surrounded by the discharge path than other parts. Since a spatially uniform discharge density can be obtained in both the gap direction and the laser gas flow direction, laser oscillation can be performed efficiently.

In this case as well, by inserting the coil 16 into the silent discharge circuit as shown in Figures 7 and 8, the distribution of the silent discharge can be adjusted, making the glow discharge uniform and ultimately increasing the laser output. Needless to say, efficiency can be improved.

This invention includes an anode and a cathode which are arranged to face each other across an airflow of Caesar gas and to which an AC high voltage is applied to generate a glow discharge; The device is equipped with a thunder body electrode that generates a silent discharge between both electrodes, and is configured to preliminarily ionize the Caesar gas by the startling discharge and emit a laser by the glow discharge, It is characterized by comprising a metal ground electrode that is grounded via a capacitor disposed near the cathode and generates a silent discharge between it and the dielectric electrode to enlarge the discharge excitation part, This has the effect of expanding the range of the discharge excitation part, making the discharge density uniform, and ultimately improving the laser output.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional horizontally pumped gas laser device, Figure 2 is a cross-sectional view taken from the line 0-B in Figure 1, and Figure 3 is a horizontal cross-sectional view of a conventional silent discharge pre-ionization method. FIG. 4 is a cross-sectional view taken from line W-W in Figure 3, FIG. 5 is a cross-sectional view of the dielectric electrode, and FIG. 6 is a vertical cross-sectional view of an embodiment of the present invention. Figures 7 and 7 are cross-sectional views taken from the skin line in Figure 6, and Figures 8 to 10 are cross-sectional views of other embodiments of the present invention, respectively. In the figure, 1 is an anode, 2 is a cathode, 4 is a DC high voltage power supply,
6 is a discharge excitation part, 9 is a dielectric electrode, 13 is an AC high voltage power supply, 14 is a metal ground electrode, 15 is a capacitor, and 16 is a coil. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Scope of Claims] 1. An anode and a cathode to which a direct current high voltage is applied to generate a glow discharge, which are arranged to face each other across a laser gas airflow, and an alternating current high voltage which is arranged in the laser gas airflow and generate a glow discharge. A device comprising a dielectric electrode that generates a silent discharge between the two electrodes when a voltage is applied thereto, and configured to preliminarily ionize the laser gas by the silent discharge and emit a laser by the glow discharge. In the lateral excitation type, a silent discharge is generated between a metal ground electrode grounded via a capacitor and installed near the cathode and the dielectric electrode to enlarge a discharge excitation part. Gas laser equipment. 2. The horizontally excited gas laser device according to claim 1, wherein metal ground electrodes are disposed on the upstream side and the downstream side of the cathode. 3 Equipped with a chiyoke coil inserted in a silent discharge circuit,
A laterally excited gas laser device according to claim 1 or 2, wherein the distribution ratio of silent discharge to each electrode is adjusted.