JPH0464196B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a gas laser generator, and particularly to a gas laser that uses glow discharge as a laser oscillation excitation source.

Configuration of Conventional Example and Problems Therewith In a laser generator using a gas substance as a laser medium, it is generally practiced to utilize glow discharge as an excitation source in order to generate a negative temperature distribution in the medium.

In this case, in order to increase the laser output, it is important to increase the electrical input injected as a glow discharge.

On the other hand, as the electrical input increases during glow discharge, the medium temperature increases, which prevents the generation of negative temperature distribution.

However, in order to increase the laser output, it is important to prevent the medium temperature from rising and to increase the glow discharge input. In order to prevent the temperature of the medium from rising, it is well known to create a flow of medium gas in the glow discharge region (inside the discharge tube) and forcibly cool the medium itself.

However, if the medium gas flow is small, it is possible to fill the discharge tube with glow discharge almost uniformly, but as the flow rate increases, the discharge path becomes narrower and the discharge only occurs in a portion of the discharge tube. It becomes impossible for this to occur. As a result, the effective discharge volume that contributes to laser oscillation within the discharge tube decreases, leading to a decrease in laser output. This tendency tends to become stronger as the glow discharge electrical input increases, and an increase in the electrical input does not necessarily increase the laser output.

Moreover, as the electrical input increases, a local rapid increase in the current density of glow discharge is observed, and in this case, the discharge becomes unstable and eventually shifts to arc discharge, which inhibits laser generation. Ru.

An example of a conventional device developed for the purpose of eliminating the above-mentioned drawbacks is shown in FIG. FIG. 1 is a configuration diagram of a carbon dioxide laser generator.

Two discharge tubes 1 made of an insulating material such as glass for generating a glow discharge for laser amplification are shown in this figure. An anode section 2 is common to both discharge tubes 1, 1, and cathode sections 3, 3 are arranged opposite to the anode section 2. Gas inlets 4, 4 are connected to the cathode parts 3, 3, and the anode part 2
A gas exhaust port 5 is provided at the.

Reflecting mirrors 6 and 7 are arranged to sandwich the discharge tubes 1 and 1, forming an optical resonator. The reflecting mirror 6 that takes out the laser output is called an output mirror, and the other reflecting mirrors 7 are generally concave reflecting mirrors.

The laser medium gas is circulated by a blower 9 or the like through the circulation paths 8, 8 to form a flow in the discharge tubes 1, 1. The positive output terminal of the DC power supply 10 is connected to the anode section 3, and the negative output terminal is connected to the cathode sections 3, 3 via stabilizing resistors 11, 11, etc. It goes without saying that configuring a constant current circuit using a vacuum tube or the like instead of the stabilizing resistors 11, 11 to maintain a constant discharge current is effective in improving the stability of glow discharge. .

The above configuration is a triaxial coaxial laser generator in which the gas flow, discharge direction, and optical cavity center axis are the same, and it is well known that it has the characteristic that it is easy to obtain the fundamental mode TEM ₀₀ mode.

However, with the above method, it is not possible to directly control the discharge itself, and there are limits to the effects that can be obtained.

In other words, the conventional method aims to stabilize the positive column in glow discharge by gas flow, but what mainly controls glow discharge is
It is a form of discharge at the cathode and not a gas stream.

Generally, in normal glow discharge, there is a current density specific to the electrode material and gas, and an increase in discharge current is achieved by increasing the surface area of the cathode where discharge occurs. On the other hand, if there is a gas flow or the gas pressure is high, it becomes impossible to increase the effective surface area where the discharge occurs as much as necessary.In order to increase the laser output, the current must be increased by increasing the current density, that is, by locally concentrating the discharge. In this case, the discharge becomes unstable and shifts to arc discharge, which impedes laser generation.

One factor that makes glow discharge unstable is the nature of the cathode. In conventional gas laser generators, the cathode is coaxially inserted into the discharge tube and has a cylindrical shape.
The vertical cross-sectional shape was rectangular. Such a cathode was provided with a gap between it and the inner peripheral surface of the discharge tube.

This cathode has a rectangular longitudinal section, so it has 90-degree corners at both ends in the axial direction, but the electric field tends to concentrate at the corners, which makes it easy for arc discharge to occur. In addition, gas flow was disturbed at both end faces in the axial direction, especially at the end face on the anode side, and the discharge from these end faces became unstable and easily turned into arc discharge. Disturbances may also occur in the gas flow in the gap between the cathode and the discharge tube, and discharge from the outer circumferential surface of the cathode facing this gap has also been a cause of transition to arc discharge.

Purpose of the invention The purpose of the present invention is to solve the conventional problems,
An object of the present invention is to provide a gas laser generator capable of sustaining stable glow discharge.

Structure of the Invention The gas laser generator of the present invention includes a discharge tube, a cylindrical cathode inserted into the discharge tube coaxially with the discharge tube, and an anode side end surface of the cathode and an anode on an inner peripheral surface of the cathode. It is provided with an insulating layer that continuously covers a partial region continuous to the side end surface.

The effect of this configuration is as follows. In other words, since the anode side end face of the cathode and a part of the inner peripheral surface of the cathode connected to the anode side end face are continuously coated with an insulating layer, the anode side corner of the cathode where electric field concentration is most likely to occur and the gas flow are It is possible to prevent discharge from the anode side end face of the cathode, where disturbance is most likely to occur, and to reliably prevent arc discharge transfer due to electric field concentration and turbulence. Therefore, the transition of cathode discharge to arc discharge is suppressed,
Glow discharge is maintained with good stability. This also makes it possible to increase the laser output.

In addition, when the cathode is installed with a gap between it and the inner peripheral surface of the discharge tube, not only the above-mentioned part of the cathode, but also the entire outer peripheral surface of the cathode and the end surface of the cathode opposite to the anode side. By covering the side end face and a partial region of the inner circumferential surface of the cathode that is continuous with the end face on the opposite side to the anode side end face, the same effect as described above is exerted.

However, when the cathode is in close contact with the inner peripheral surface of the discharge tube (insulator), the entire outer peripheral surface of the cathode, the end surface of the cathode opposite to the anode end surface, and the anode end surface of the inner peripheral surface of the cathode There are cases where it is not necessary to cover a part of the region continuous to the end surface on the opposite side, and this is especially true for the outer circumferential surface.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. 2 shows the vicinity of the discharge tube in the carbon dioxide laser generator.

At the end of each discharge tube 1 on the cathode section 3 side, a cathode 12 having a cylindrical shape and a rectangular vertical cross section as shown in FIG.
is inserted coaxially with the discharge tube 1. Both end surfaces a, a and both corner portions b, b in the axial direction of this cathode 12
In addition, the outer peripheral surface c is tightly covered with an insulating layer 13. Therefore, the discharge surface of this cathode 12 is only the inner circumferential surface d excluding both corner portions b, b.

The rest is the same as the conventional example (Fig. 1), so
Identical parts are given the same reference numerals, and their explanations are omitted.

Corners b, b where electric field concentration tends to occur, end faces a, a, and outer circumferential surface c where gas flow is likely to be disturbed are covered with an insulating layer 13 to prevent discharge from these parts. That is, since the discharge surface is limited to only the inner circumferential surface d where the above-mentioned disadvantages are unlikely to occur, transition to arc discharge is prevented and glow discharge is maintained in good condition. Therefore, it is also possible to increase the laser output.

Effects of the Invention According to the gas laser generator of the present invention, the anode-side end surface of the cathode and a partial region of the inner circumferential surface of the cathode connected to the anode-side end surface are continuously covered with an insulating layer, so that electric field concentration is likely to occur. It can prevent discharge from the corner of the anode side of the cathode and the end face of the anode side of the cathode that tends to cause turbulence in the gas flow, reliably prevent arc discharge transfer due to electric field concentration and turbulence, and transform glow discharge into a large electric current. It becomes possible to maintain the input power, and it is possible to stably increase the laser output. Further, in order to stably increase the laser output, it is sufficient to simply cover a part of the cathode with an insulating layer, and the structure is simple and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a conventional example, FIG. 2 is a configuration diagram of a portion near a discharge tube according to an embodiment of the present invention, and FIG. 3 is a sectional view of a cathode. DESCRIPTION OF SYMBOLS 1... Discharge tube, 12... Cathode, 13... Insulating layer, a... End surface, b... Corner, c... Outer peripheral surface.

Claims (1)

[Scope of Claims] 1. A discharge tube, a cylindrical cathode inserted into the discharge tube coaxially with the discharge tube, and an anode side end surface of the cathode and an inner peripheral surface of the cathode connected to the anode side end surface. A gas laser generator comprising: a partial region; and an insulating layer continuously covering a partial region. 2. The cathode is provided with a gap between it and the inner peripheral surface of the discharge tube, and the insulating layer covers the entire outer peripheral surface of the cathode, the end surface of the cathode opposite to the anode side end surface, and the insulating layer. 2. The gas laser generator according to claim 1, wherein a partial region of the inner circumferential surface of the cathode that is continuous with the end surface on the anode side and the end surface on the opposite side is coated.