JPH02294084A - Gas laser oscillating equipment - Google Patents

Abstract

PURPOSE:To output high quality laser light excellent in symmetric properties by installing discharge electrodes in the manner in which the opening angle becomes smaller along gas flow as it goes down-stream. CONSTITUTION:On both sides of a discharge tube 1 filled with gas being laser medium, a pair of discharge electrodes 2a, 2b are arranged so as to put the discharge tube 1 between them With respect to the axis of the discharge tube 1, the opening angle thetad at the lower part of gas flow is set smaller than the opening angle thetau at the upper part of the gas flow. The opening angle is made gradually small as the gas flow goes down-stream. The opening angle thetad at the lower part of gas flow, where the temperature rise of gas becomes remarkable, is made small, thereby increasing the distance between end-portion of electrodes and preventing the discharge concentration at the end-portions of electrodes. Hence spatially uniform discharge in the whole part of the discharge tube 1 is realized, and laser excellent in symmetric properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a gas laser oscillation device, and particularly to a discharge electrode structure for obtaining uniform discharge.

(Prior Art) In general, a laser device has discharge electrodes disposed opposite to each other in the circumferential direction of a discharge tube having a dielectric material and filled with gas as a laser medium, and a voltage is applied to the discharge electrodes. By doing so, the gas that is the laser medium is excited and discharged, and laser oscillation is performed.

In recent years, advances in laser technology development have led to the practical use of compact, high-output gas laser oscillation devices.In such gas laser oscillation devices, the heated laser medium is In order to cool the gas that is, the gas is forcibly supplied from the outside,! I'm trying to put out X and circulate it.

FIG. 3 shows the discharge tube and discharge electrode structure of such a gas laser oscillation device. In FIG. 3, a pair of discharge electrodes 2a and 2b are placed on both sides of a discharge tube 1 filled with gas as a laser medium, facing each other with the discharge tube 1 in between. These discharge electrodes 2a, 2b are connected to an external high frequency? IS source 3
When a high frequency voltage is applied between the discharge electrodes 2a and 2b from the high frequency power source 3, the gas serving as the laser medium within the discharge tube 1 generates a high frequency discharge.

In addition, each discharge electrode 2a, 2b is connected to the axis of the discharge tube 1.
It is provided so that the width dimension of a constant opening angle θ is H. In order to widen the discharge lighting area, it is better to have the above-mentioned opening angle θ larger, and it has been found from experimental results that at θ-120°, about 9,496 high-frequency discharges in the entire discharge tube 1 are lit.

(Problem to be Solved by the Invention) By the way, as shown in FIG. 3, gas, which is a laser medium, is supplied to the discharge tube by injecting the gas 4 from one end of the discharge tube 1 and discharging the gas 5 from the other end. Due to the high-frequency discharge generated in the discharge tube 1, the heated laser medium gas is forced to circulate in order to cool it down. There is a reason why it expands. Therefore, the gas density becomes thinner as it goes downstream, and as a result, the discharge resistance becomes smaller and the discharge becomes unstable.

FIG. 4 shows how the high-frequency discharge emits light.

Here, the opening angle of the discharge electrodes is about 120°. In the figure, (a) shows the overall light emission from upstream to downstream of the gas flow, (l) shows the upstream of the gas flow, and (C) shows the downstream of the gas flow. The region where the emission intensity of the high-frequency discharge is strong is the region where ionization has progressed, so the number of gas molecules that are the laser medium that are excited by the laser upper quasi-depletion is large, and the number of gas molecules passing through that region is increased and the laser becomes stronger. Become. Therefore,
If the intensity distribution of hk electricity is non-uniform, the quality of the obtained laser light will be poor. In other words,
If a more uniform discharge is obtained, it becomes possible to obtain high quality laser light.

Now, in the upstream of the gas flow, as shown in Figure 4(b), in the high-frequency discharge, the hk current is somewhat strong near the discharge γ hypopoles 2a and 2b, and the distance between the electrodes is short and the local impedance is low. The discharge between the electrode ends is also somewhat strong, but the discharge is generally symmetrical about the discharge tube axis. This is because, as mentioned above, the opening angle of the discharge electrodes 2a, 2b is set to a large value of nearly 120'.

Here, the reason why the discharge near the discharge tube 1 on the electrode is somewhat strong is because
Secondary electrons generated by ion collision with the discharge tube 1 are accelerated by the ion sheath near the discharge tube 1, causing further ionization. (Literature=rD.He et a
l,,J,Appl. Phys. ．． 55 (11), 1
984J) By the way, in the downstream of the gas flow, as shown in Fig. 4 (c
), it is easy to concentrate between the opposing ends of the discharge electrodes 2a and 2b. This is because, as mentioned above, the temperature of the gas increases significantly downstream of the gas flow, and the gas expands.
The gas density becomes thinner as it goes downstream, and the discharge resistance decreases accordingly, so the discharge current tends to increase as it goes downstream. In addition, the distance between the electrodes is short and the discharge current is large at the end of the electrode where the local impedance is low and the discharge is concentrated.

If you look at the entire gas flow from upstream to downstream, it will look as shown in Figure 4(a), and both ffs facing each other downstream of the gas flow
The concentration of discharge between the three extreme parts is large, resulting in non-uniform discharge.

For this reason, there is a problem in that the laser output from the gas laser oscillation device having the above-described discharge tube and electrode structure has poor axial symmetry.

Therefore, in view of the above-mentioned problems, an eleventh object of the present invention is to provide a gas laser oscillation device having an electrode structure that enables spatially uniform discharge in the entire discharge tube and obtains a laser beam with good symmetry. .

[Details of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a discharge tube having an outer shell made of a dielectric material, and the inside of which is filled with a laser medium;
A discharge electrode provided in the χ·1 direction on both sides of the discharge tube in the circumferential direction, a high frequency power source connected between the discharge electrodes,
In the gas laser oscillator device 61, which includes a circulating means for causing the laser medium in the discharge tube to flow in a fixed direction, the discharge electrode 7i is arranged such that the opening angle of the discharge electrode becomes smaller toward the downstream side with respect to the flow of the laser medium. Deliver the installed gas laser oscillation device.

(Function) In the device configured as described above, a high frequency voltage is applied to the pole of the discharge 7 by the high frequency source 7d, a high frequency discharge is generated in the gas which is the laser medium, and the temperature of the gas is increased. At this time, since the gas serving as the laser medium flows in one direction within the discharge tube due to the circulation means, the temperature thereof increases more significantly as it moves downstream in the gas flow. As the temperature of the gas increases, the impedance of high-frequency discharge decreases, and the discharge tends to concentrate especially at the electrode ends where the distance between the electrodes is short and the local impedance is low.
By changing the opening angle of the discharge electrodes upstream and downstream and making the downstream opening angle smaller, the distance between the ends of the electrodes can be increased, so that concentration of discharge at the ends of the electrodes can be prevented. However, simply reducing the opening angle of the electrodes overall will reduce the discharge lighting area and impede the uniformity of the discharge, but by leaving a large opening angle of the electrodes upstream of the gas flow where it is difficult to concentrate the discharge. In the upstream part of the gas flow, the discharge near the electrodes and between the opposite ends of the electrodes is somewhat strong, and as a whole, high-frequency discharge can be uniformly generated within the discharge tube.

(Example) Hereinafter, an example of the present invention will be described with reference to FIG. Note that the same parts as those in the prior art described above are given the same reference numerals.

In FIG. 1, the inside of an hk electric tube 1 is filled with gas, which is a laser medium. -λ・ on both sides of discharge tube 1
1 discharge t-L poles 2a and 2b are arranged facing each other so as to sandwich the discharge shield 1. This b-i'a electrode 2a,
A high frequency power source 3 is connected to 2b, and when a high frequency voltage is applied between the hk electrodes 2a and 2b by the high frequency power source 3, the gas that is the laser medium in the discharge tube 1 generates a high frequency discharge. It's starting to happen.

The 6 discharge electrodes 2a and 2b are respectively connected to the hk electric tube 1.
has a certain opening angle with respect to the axis of the gas flow, but the opening angle θU upstream of the gas flow and the opening angle θd downstream are set,
The downstream opening angle θd is set smaller than the upstream opening angle θU.

In this embodiment, the discharge electrode 2 is arranged so that the opening angle thereof gradually decreases as the gas flow moves from upstream to downstream.
This is an example in which a and 2b are provided.

The operation of this embodiment having the above configuration is as follows.

FIG. 2 shows how high-frequency discharge occurs. In the same figure (a
) shows the overall occurrence of the gas flow from upstream to downstream; (b) is the upstream gas flow, and (C) is the downstream.

Now, upstream of the gas flow, as shown in FIG. 2(b), the high-frequency discharge occurs near the discharge electrode, as in the conventional example described above.
Although the discharge is somewhat strong between opposing electrode ends where the distance between the electrodes is short and the local impedance is low, the discharge is nearly symmetrical about the discharge tube axis.

Next, in the downstream of the gas flow, as shown in FIG. 2(c), is the gas released? By reducing the scissor angle of the Li electrode, the distance between the opposing ends of the discharge electrodes, where the gas temperature rises and discharge tends to concentrate, has increased, unlike the conventional example described above, the discharge concentrates at the electrode ends. can be suppressed, and the discharge lights up in the center between the discharge electrodes.

If you look at the entire gas flow from upstream to downstream, the second
As shown in Figure (a), the gas flow is strong upstream at both ends of the discharge electrode, and the gas flow downstream is strong at the center, so that a uniform discharge can be produced throughout the discharge tube.

As described above, in the example, the uniformity of discharge can be improved by a factor of 11'' compared to when the scissor angle of the discharge electrodes is constant, so that high-quality laser light with good symmetry can be output.

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, the opening angle of the discharge electrode may not be changed gradually, but may be changed discontinuously.

Furthermore, even if the opening angle of the discharge electrode is gradually increased from upstream to downstream of the gas flow, and then further reduced, the same result will occur if the opening angle of the discharge electrode downstream of the gas flow is smaller than that upstream. You can get the effect of

Furthermore, if the opening angle of the discharge electrode is made smaller toward the downstream side of the gas flow, the same effect can be achieved even when the entire discharge has a spiral shape, and the present invention can be fully applied.

[Effects of the Invention] As explained above, according to the gas laser oscillation device of the present invention, the discharge electrode is provided with respect to the gas flow so that its opening angle decreases as it goes downstream. A roughly uniform discharge can be obtained, and a high quality laser beam with good symmetry can be output, making it extremely suitable for nails.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a gas laser oscillation device that is an embodiment of the present invention, FIG. 2 is a diagram showing the state of high-frequency discharge of the gas laser oscillation device shown in FIG. 1, and FIG. , a schematic configuration diagram showing a conventional gas laser oscillation device, FIG.
FIG. 2 is a diagram showing a state of high-frequency discharge of the gas laser oscillation device shown in the figure. In FIGS. 2 and 4, (a) is a diagram showing the entire discharge from upstream to downstream of the gas flow, (b) is a diagram showing the discharge in the upstream part of the gas flow, and (c) is a diagram showing the discharge in the upstream part of the gas flow. It is a figure which shows the electric discharge downstream of a gas flow. l...discharge 7u tube, 2a, 2b...discharge 7 is pole, 3...high frequency power supply, θU...upstream opening angle,
θd...Downstream opening angle, 4...Gas inflow. 5.
...gas υ [out

Claims (1)

[Claims] A discharge tube having an outer shell made of a dielectric material and filled with a laser medium, discharge electrodes provided on opposite sides of the discharge tube in the circumferential direction, and a high-frequency power source connected between the discharge electrodes. and a circulation means for flowing the laser medium in a fixed direction within the discharge tube,
The opening angle of the discharge electrode is relative to the flow of the laser medium,
A gas laser oscillation device characterized in that the discharge electrode is provided so as to become smaller toward the downstream side.