JPS62160780A - Gas circulating type gas laser - Google Patents

Abstract

PURPOSE:To improve spatial uniformity of discharge plasma as a whole, to obtain laser output at high efficiency and to implement a compact configuration, by inducing auxiliary glow discharge on the upstream side of a gas flow with respect to a cathode electrode by using divided type auxiliary electrodes. CONSTITUTION:Cathode electrodes 2 are divided into a plurality of parts and aligned along the longitudinal direction of a resonator. A plurality of auxiliary electrodes 3 are aligned along the longitudinal direction of the cathode electrodes 2. A distance l3 between the cathode electrode 2 and an anode 1 on the downstream side of the gas flow is made longer than a distance l2 between the electrodes 2 and the anode 1 on the upstream side of the gas flow. For this purpose, the end surface of the electrodes 2 are made to be a slant surface. A distance l1 between the auxiliary electrodes 3 and the anode 1 is made shorter than the distance l2 between the cathodes 2 and the anode 1. The auxiliary electrodes 3 are set in this way and the auxiliary discharge is separately generated in addition to the main discharge. Then the power density of the main discharge is increased. The uniform auxiliary discharge is performed in a space by the divided type auxiliary electrode structure. Thus the discharge plasma part in the gas flowing direction and the beam direction becomes spatially uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a gas circulation type gas laser that utilizes glow discharge.

[Technical background of the invention and its problems]

A typical example of a gas circulation type gas laser is a CO2 laser. Conventional gas circulation CO with split cathode electrode
An example of the structure of two lasers is shown in FIG.

11 is a flat anode electrode, and 12 is a cathode electrode which is divided into a plurality of pieces and arranged. Cathode electrode 1
2 is attached to an insulating support plate 13. The anode electrode 11 is connected to the positive electrode of the main power source 15, and the cathode electrode 12
is connected to the negative electrode of the main power source 15 via the discharge limiting resistor 14.

161 and 162 are resonator mirrors, and 17 indicates the direction of CO2 gas flow. As is clear from the figure, the gas flow and the discharge current direction are perpendicular to each other, and the mirrors 161 and 162 are arranged to face each other along the direction perpendicular to both the gas flow and the discharge current.

In such a conventional configuration, the spatial uniformity of the discharge plasma generated between the anode electrode 11 and the cathode electrode 12 is insufficient, the discharge power density is low, and the discharge is unstable. Therefore, there is a problem that high laser output efficiency cannot be obtained, and that the apparatus becomes large in size when attempting to obtain a large output.

[Purpose of the invention]

In view of the above points, the present invention provides a gas circulation type gas laser that improves the discharge power density and the spatial uniformity of the discharge plasma, thereby improving the laser output efficiency and making it possible to miniaturize the device. The purpose is to

[Summary of the invention]

The gas circulation type gas laser according to the present invention is basically arranged such that a split-type auxiliary electrode that induces auxiliary glow discharge between at least one of the cathode electrode and the anode bridge is arranged on the gas upstream side of the cathode electrode. . In addition, in this basic configuration, the distance between the auxiliary electrode and the anode electrode is set smaller than the distance between the cathode electrode and the anode electrode, and the distance between the cathode electrode and the anode electrode is set on the gas downstream side. It is characterized by having an end face shape that is larger than the gas upstream side.

〔Effect of the invention〕

According to the present invention, by inducing an auxiliary glow discharge on the upstream side of the gas flow with respect to the cathode electrode using a split auxiliary electrode, the spatial uniformity of the discharge plasma as a whole is improved. In addition, by setting the distance between the auxiliary electrode and the anode electrode to be smaller than the distance between the cathode electrode and the anode electrode, it becomes possible to efficiently supply the plasma generated in the auxiliary discharge to the main discharge area, thereby increasing the main discharge power. The density is increased. Further, the discharge starting voltage is also lowered, and the power supply voltage can be lowered. Furthermore, by selecting the shape of the end surface of the cathode electrode on the anode electrode side, it is possible to prevent negative glow from concentrating on the downstream side of the gas and obtain a stable wide discharge area. According to the invention, therefore:
Highly efficient laser output can be obtained, and the device can be made smaller.

[Embodiments of the invention]

The present invention will be explained in detail below.

FIG. 1 is a cross-sectional view of a gas circulation type C02 laser according to an embodiment, viewed from the resonator length direction, and FIG. 2 is a cross-sectional view similarly viewed from the gas flow direction. 1 is a flat anode electrode, and 2 is a cathode electrode. The cathode electrode 2 is divided into a plurality of pieces and arranged along the length direction of the resonator. A plurality of auxiliary electrodes 3 are also arranged along the resonator length direction on the downstream side of the gas flow with respect to the cathode electrode 2 . These cathode electrode 2 and auxiliary electrode 3 are attached to an insulating support plate 4. The cathode electrode 2 is connected to the main power source 6 via a discharge limiting resistor 51. The auxiliary electrode 3 is selectively connected to the main power source 6, an auxiliary DC power source 71 or an auxiliary AC power source 72, or grounded via a discharge limiting resistor 52 and a switch. Reference numerals 81 and 82 are mirrors constituting the resonator, and 9 indicates the gas flow direction.

The end surface of the cathode electrode 2 on the anode electrode 1 side is formed with a predetermined width in the gas flow direction.

As shown in FIG. 1, the distance a3 between the cathode electrode 2 and the anode electrode 1 on the downstream side of the gas flow is equal to the distance between the anode electrode 1 on the upstream side of the gas flow! The end surface thereof is an inclined surface so that the diameter is larger than 22. In addition, 1 ton of assistance
! ! Distance I between 3 and anode bridge 1! Iiλ1 is set to be smaller than the distance j22 between the cathode electrode 2 and the anode electrode 1.

The characteristics of the CO2 laser configured in this way will be explained below. Generally, in a gas circulation type CO2 laser, in a certain electrode structure, once the gas composition, pressure, gas flow rate, etc. are determined, the upper limit value of the glow discharge power density is determined in accordance with these parameters. However, Fig. 1.

When the auxiliary electrode 3 is provided as shown in FIG. 2 and the auxiliary discharge is generated separately from the main discharge, the main discharge power density increases. Although detailed data will be listed later, it has been experimentally confirmed that the main discharge power density increases by three to four times by generating an auxiliary discharge.

Moreover, when auxiliary discharge is performed at the same pressure and the same gas mixture ratio, the discharge sustaining voltage Vo decreases compared to when no auxiliary discharge is performed, but the discharge current IQ increases by about 5 times, and the laser oscillation output increases. do. Further, by performing a spatially uniform auxiliary discharge using the split type auxiliary electrode configuration, the discharge plasma portion in the gas flow direction and the beam direction becomes spatially uniform.

These effects are thought to be due to the plasma generated on the upstream side of the gas flow being directly supplied to the main discharge region by the auxiliary discharge, thereby increasing the ionization efficiency. These effects reduce the distance 21 between the auxiliary electrode 3 and the anode electrode 1 to the distance 21 between the auxiliary electrode 3 and the anode electrode 1.
This is doubled by making the distance between the anode electrode 1 and the anode electrode 1 smaller than the distance 22.

Furthermore, by making the end face of the cathode electrode 2 an inclined surface and making the distance 12s' to the anode electrode 1 on the downstream side larger than the distance λ2 to the anode electrode 1 on the upstream side,
Efforts are being made to improve the stability of discharge. That is, in general, the negative glow region on the surface of the cathode electrode tends to become unstable in a flowing gas of a certain number + torr or more, whereas a gas circulation type laser discharge has a certain width along the gas flow direction depending on the resonator mirror. A separate discharge area is required. Therefore, the split cathode electrode requires a certain width in the gas flow direction, but even if you simply secure the width, when observing the actual discharge, the negative glow region will flow in the gas flow direction and will be concentrated on the downstream side. and become unstable. On the other hand, by designing the end surface shape of the cathode electrode 2 as shown in FIG. 1, a negative glow region stably exists over the entire end surface of the divided cathode electrode, and the discharge region is expanded.

Next, specific characteristic data of the CO2 laser of this example will be explained.

FIGS. 3 and 4 show the results of measuring the relationship between gas flow rate and maximum glow discharge power under various auxiliary discharge conditions. FIG. 5 shows the results of measuring the relationship between input power and laser output power under various auxiliary discharge conditions. Note that the maximum glow discharge power is the power at which glow discharge becomes unstable and arc discharge begins to occur. In Figure 3, the gas pressure is PT -60torr, and in Figure 4, it is the same <Pt = 90
This is the case for torr. The distance between each electrode is λ1#50j
lllI.

Q2=60m, Q3-70m. The DC auxiliary discharge between the auxiliary electrode and the cathode electrode is caused by the auxiliary electrode 3 in FIG.
This was done by grounding via the limiting resistor 52 (that is, setting it to the same potential as the anode electrode 1). These figures also show data when the auxiliary electrode 3 is kept floating and no auxiliary discharge is performed.

From these data, the following can be said.

(1) When there is an auxiliary discharge, the maximum glow discharge power is 2 to 4 times greater than when there is no auxiliary discharge.

(2) When auxiliary discharge is performed, the maximum glow discharge power tends to increase as the gas flow rate increases.

(3) Regarding the form of auxiliary discharge, when the gas pressure is high, AC discharge is more advantageous than DC discharge.

At low pressures, the difference is hardly visible.

(4) When the pressure is high, the effect will be sufficiently increased if the auxiliary discharge is caused at both the anode electrode and the cathode electrode, regardless of whether the method is AC discharge or DC discharge.

If the pressure is low, it will be effective if it is applied to either the anode electrode or the cathode electrode.

(5) It has been found that when auxiliary discharge is performed, the discharge sustaining voltage decreases, and the discharge power density becomes approximately 8 W/aa2 or more, which is 2 to 4 times that of the conventional discharge power density. This result leads to an increase in laser output as shown in FIG.

The present invention is not limited to the above embodiments.

For example, when using the AC auxiliary power supply 72 in FIG.
A capacitor can be used instead of the limiting resistor °52. The Ikensui invention can be implemented with various modifications without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view in the resonator length direction showing a CO2 laser according to an embodiment of the present invention, FIG. 2 is a cross-sectional view in the gas flow direction,
Figures 3 and 4 are diagrams showing the relationship between the gas flow velocity and maximum glow discharge power of the CO2 laser, Figure 5 is a diagram showing the relationship between discharge input and laser output, and Figure 6 is a diagram showing the relationship between the gas flow rate and maximum glow discharge power of the CO2 laser.
It is a figure showing the composition of two lasers. 1... Anode electrode, 2... Cathode electrode, 3...
- Auxiliary electrode, 4... Insulating support plate, 51.52... Discharge limiting resistor, 6... Main power supply, 71... Auxiliary DC power supply, 72... Auxiliary AC power supply, 81.82... - Resonator mirror, 9... gas flow direction.

Claims (5)

[Claims] (1) In a gas circulation type gas laser having an anode electrode and a split cathode electrode for inducing glow discharge, an auxiliary glow is provided between the gas upstream side of the cathode electrode and at least one of the cathode electrode and the anode electrode. A split-type auxiliary electrode for inducing discharge is arranged, a distance between the auxiliary electrode and the anode electrode is set smaller than a distance between the cathode electrode and the anode electrode, and the cathode electrode is set to be smaller than the distance between the anode electrode and the anode electrode. A gas circulation type gas laser characterized by having an end face shape in which the distance between the two gases is larger on the downstream side than on the upstream side. (2) The auxiliary electrode is connected via a discharge limiting element to an auxiliary DC power supply provided separately from the main power supply for inducing glow discharge between the anode electrode and the cathode electrode. The gas circulation type gas laser according to item 1. (3) The auxiliary electrode is connected via a discharge limiting element to an auxiliary AC power source provided separately from the main power source for inducing glow discharge between the anode electrode and the cathode electrode. The gas circulation type gas laser according to item 1. (4) The gas circulation type gas laser according to claim 1, wherein the auxiliary electrode is connected to a main power source via a discharge limiting element for inducing glow discharge between the anode electrode and the cathode electrode. . (5) The gas circulation type gas laser according to claim 1, wherein the auxiliary electrode is grounded via a discharge limiting element.