JPS6239555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electrodes for silent discharge type gas laser devices.

First, a conventional silent discharge gas laser device will be explained using an orthogonal CO ₂ laser as an example.

FIG. 1 is a diagram showing the basic structure of a conventional device, FIG. 2 is a gas system diagram thereof, FIG. 3 is a diagram of its electrode structure, and FIG. 4 is a sectional view taken from the - line.

First, in Fig. 1, 1 and 2 are dielectric materials, 3,
4 is a metal plate whose discharge surface is covered with dielectrics 1 and 2, and 1 and 3 and 2 and 4 form one silent discharge electrode 30 and 40, respectively. 5 is a discharge space, 6 is an AC power supply, 7 is a total reflection mirror, and 8 is a partial reflection mirror.

When an AC high voltage (approximately 10KHz, 10KV) is applied to the metal plates 3 and 4 by the AC power source 6, the discharge space 5
A stable discharge called silent discharge occurs. Laser gas (for CO ₂ lasers, generally CO ₂ ,
When the gas mixture (CO, N ₂ , He) passes through the discharge space 5 , it is laser excited by this silent discharge, and is oscillated by an optical resonator composed of a total reflection mirror 7 and a partial reflection mirror 8 . The excited molecular energy is extracted from the partially reflecting mirror 8 as laser light.

Next, FIG. 2 shows the laser gas system in the conventional device, where 9 is a gas guide made of an inorganic insulator, 10 is a blower, and 11 is a heat exchanger that changes the temperature. Down, blower 10
The laser gas accelerated to high speed passes through the discharge space 5 along the gas guide 9 in a direction perpendicular to both the discharge and the laser beam (perpendicular to the plane of the paper). The gas velocity in the discharge space 5 is 30 m・
The speed is set to about S ^-1 , and the rise in gas temperature due to the thermal energy received by the discharge is suppressed to about 50℃. This is because the light absorption rate of CO ₂ increases rapidly as the gas temperature rises, reducing the laser oscillation energy efficiency, so it is necessary to keep the gas temperature low.

Figure 3 shows the electrode structure diagram of the conventional device, and Figure 4 shows the structure of the electrode of the conventional device.
The figure is a cross section taken along the line in FIG. 3, showing the direction of gas flow, the direction of discharge, and the direction of the optical axis (laser light). 5a, 5b, and 5c are the gas flow upstream side, central portion, and downstream side of the discharge space 5. 3b and 4b are portions of the metal plates 3 and 4 that are not covered with the dielectric material.

Here, the characteristics of silent discharge will be briefly explained. The silent discharge is an alternating current discharge that occurs via the dielectrics 1 and 2, and as the power supply voltage increases, the voltage in the discharge space 5 increases, and when the discharge space potential difference reaches the discharge starting voltage, a pulsed discharge occurs. When a discharge occurs, charges are deposited on the surfaces of the dielectrics 1 and 2, and as a result, the voltage in the discharge space 5 decreases and the discharge disappears. When the voltage in the discharge space 5 reaches the discharge starting voltage again due to an increase in the power supply voltage, a discharge occurs. Such discharges are repeated several to several dozen times during a half cycle of the AC power supply, and in the next half cycle, discharges of opposite polarity are similarly repeated.

By the way, silent discharge is a discharge that easily spreads along the dielectric surface of the electrode, so the distribution of discharge energy in the discharge space is not uniform in the gas flow direction, and the discharge space ends 5a and 5c are more uneven than the central part 5b. This results in a discharge with high energy density. As a result, thermal breakdown occurs in the portions of the dielectrics 1 and 2 near the discharge spaces 5a and 5c, or the temperature of the laser medium gas passing through the discharge space 5 becomes partially high, and the amount of light absorbed by _CO2 decreases. This has the disadvantage of increasing the laser oscillation efficiency and reducing the laser oscillation efficiency.

Furthermore, when the applied voltage is increased, the discharge further spreads to the parts 3b and 4b where the dielectric material is not lined (sprayed) behind the electrodes 30 and 40, and from there, a discharge is generated that travels along the surface of the dielectric material to the counter electrode. However, this causes trouble in that the dielectrics 1 and 2 and the power source 6 are destroyed.

In addition, the electrode structure of the conventional silent discharge type gas laser device is as shown in FIGS.
Since the dielectrics 1 and 2 are lined with (sprayed) the dielectrics 1 and 2, it is difficult to make the thicknesses of the dielectrics 1 and 2 uniform. For this reason, due to the characteristics of silent discharge, the capacitance per unit area increases in areas where the dielectric is thin, the discharge power concentrates, and the dielectric in that area is likely to be damaged, making it difficult to spread the dielectric uniformly. It needed lining. Conventional electrodes have been limited to simple structures because uniform lining is technically difficult for electrodes with complex shapes. Therefore, it has been difficult to create electrodes with a desired shape to maximize the efficiency of the oscillator.

Furthermore, since the laser gas needs to flow through the discharge space 5 at high speed as shown in FIG. 2, a gas guide 9 must be provided. Since a part of the gas guide 9 is exposed to electric discharge, it was necessary to be made of an insulating material that does not generate outgas.

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional ones, and aims to provide a silent discharge type gas laser device that has a simple structure and high reliability by improving the electrode structure. .

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is an electrode structure diagram showing an embodiment of the present invention, FIG. 6 is a sectional view taken from the - line, and FIG.
The figure shows the gas system diagram, and 1-1 and 2-1 have concave grooves dug on the opposite surface of the discharge surface. Electrode 3
Inorganic dielectric plate which is the main constituent of 0.40, 1-
1b and 2-1b are the discharge locations (where the thickness of the concave portion is thin), and 3-1 and 4-1 are the metals provided in the concave portions of the inorganic dielectric plates 1-1 and 2-1. The gas flow direction, discharge direction, and optical axis direction are shown in FIG. In this way, the electrodes 30, 40
, the discharge is caused by the inorganic dielectric plate 1- which has a large capacitance per unit due to the characteristics of silent discharge.
1, 2-1 thinner parts 1-1b, 2-1b
As a result, a discharge without energy concentration occurs in the discharge space 5, and the temperature of the laser medium gas passing through the discharge space 5 does not become high locally, and Since the dielectric creepage distance is long even if the metal plate 3-1 and 4 are increased,
Since no discharge occurs from -1 to the counter electrode, there is almost no risk of damage to the dielectric and the power source.

Further, since the concave grooves of the inorganic dielectric plates 1-1 and 2-1 can be made by mechanical grinding, etc., the dielectric thickness of the discharge parts 1-1b and 2-1b can be made uniform. (For example, if the inorganic dielectric plate is made of easy-to-cut glass ceramics, accuracy: ±0.05
mm can be easily achieved). Therefore, the capacitance per unit area of electrode discharge portions 1-1b and 2-1b becomes uniform, and the power density of the discharge becomes even more uniform, thereby eliminating damage to the dielectric. Furthermore, the positions of the concave grooves on the inorganic dielectric plates 1-1 and 2-1 and the positions of the metal plates 3-1 and 4-1 can be freely set, making it possible to create electrodes with the optimal shape for oscillation. can.

In addition, as shown in FIG. 7, in this electrode structure, the inorganic dielectric plates 1-1 and 2-1 also serve as gas guides, and the gas guide 9 and each electrode 30, 40 shown in FIG. Since there is no joint between the blower 10 and the gas flow, the turbulence in the gas flow that conventionally occurs at the joint can be eliminated, and a structure with minimal resistance to the gas flow can be obtained, so the blower 10 does not require a special and expensive item. I won't.

As described above, according to the present invention, an electrode excellent in terms of both laser oscillation efficiency and practical reliability can be realized.

Several other examples will be shown below.

FIG. 8 shows the metal plates 3-1 and 4 of the embodiment shown in FIG.
Electrode configuration diagram of an embodiment in which -1 is replaced with conductive thin films 3-2 and 4-2, and the concave portions of inorganic dielectric plates 1-1 and 2-1 are coated or metallized,
FIG. 9 is a cross-sectional view taken from the - line, and it is possible to obtain the same effect as the above embodiment, and also to connect the conductive thin films 3-2, 4-2 and the inorganic dielectric plate 1-.
There is an advantage that the 1, 2-1 contact is perfect.

FIG. 10 shows the conductive thin film 3 of one embodiment of FIG.
-2, 4-2 and inorganic dielectric plate 1-1, 2-
Figure 11 is an electrode configuration diagram of an example in which an insulating refrigerant is cooled by flowing into the concave portion of No. 1.
This is a sectional view taken along a line, and 12 and 13 are refrigerant jacket plates made of inorganic insulators for flowing an insulating refrigerant, and the recessed portions of inorganic dielectric plates 1-1 and 2-1 and the refrigerant jacket plate 12 are shown. , 13 to cool the electrode by flowing an insulating refrigerant (deionized water or insulating oil) into the gap between the electrodes and the inorganic dielectric. Thermal damage to the body plates 1-1 and 2-1 can be prevented. Therefore, this electrode structure can be used to increase the discharge power and realize a high power laser.

FIG. 12 shows the concave portions of the inorganic dielectric plates 1-1 and 2-1 and the metal plates 3-1 and 4- of the embodiment shown in FIG.
1 is installed along the resonator optical path and is applied to a "folded laser".
7-6 is a total reflection mirror, 1-2, 2-2 are inorganic dielectric plates, and along the resonator optical path, a plurality of concave grooves are formed on the surface opposite to the discharge surface. 3-3, 4-3 is a metal plate with dielectric plates 1-2 and 2-2 along the resonator optical path.
It is provided in a concave groove formed in the groove, so that the same effect as shown in FIG. 6 of the embodiment can be obtained, and a discharge excitation space with a more complicated shape can be freely formed in accordance with the request for improving laser oscillation efficiency. Now I can do it.

FIG. 14 is a diagram of an electrode configuration of an embodiment in which gas in a plasma state is used instead of the metal plates 3-1 and 4-1 in FIG. 6, and FIG. 15 is a sectional view taken along the - line. 3-4, 4-4 is a plasma discharge space filled with low pressure inert gas; 14;
15 is a conductive power supply plate, and by applying an AC high voltage to the power supply plates 14 and 15, the low-pressure inert gas becomes plasma and becomes conductive, and the silent discharge generated in the discharge space 5 is This is the same as the embodiment shown in FIG. In this example, the depth of the grooves in the concave portions of the inorganic dielectric plates 1-1 and 2-1 was 5 mm, and Ar gas was sealed as an inert gas at a pressure of several torr. The potential drop in the plasma discharge spaces 3-4, 4-4 is 200V, which is much smaller than the voltage of 10KV applied between the electrodes, and the inert gas essentially acts as a "plasma electrode." In this embodiment, the degree of freedom in the shape of the electrode is greater than in the embodiment shown in FIG.

Although all of the above embodiments have the same structure on the high voltage side and the low voltage side, it goes without saying that the effects of the present invention can also be obtained when the electrode on one side is a metal plate or a metal rod.

As explained above, the present invention provides a pair of electrodes 3 forming a silent discharge space 5 serving as a laser excitation section.
At least one of the electrode structures of 0 and 40 is formed of an inorganic dielectric material close to a flat plate as a main component and a conductive material provided on a part of the back surface thereof,
In addition, the thickness of the dielectric plate at the position where the conductive material is provided is thinner than at other parts where the conductive material is not provided, which makes the power distribution in the discharge space uniform. The present invention provides an electrode structure that can improve the end insulation of the electrode, increase the reliability of the electrode, and lower the resistance to gas flow all at once.

Furthermore, by cooling the back surface of the inorganic dielectric material with an insulating coolant, thermal damage to the electrodes can be prevented, and it is possible to increase the output power of the laser.

Furthermore, since the concave grooves provided on the back surface of the plate-shaped inorganic dielectric material can be placed in any position, complex-shaped discharge excitation spaces can be freely formed, making them ideal for folded resonators. effective.

As described above, the present invention has made it possible to realize a highly reliable, highly efficient, high-output silent discharge gas laser device with a simple electrode structure.

[Brief explanation of the drawing]

Figure 1 is a principle diagram showing the configuration of the main parts of a conventional orthogonal gas laser device, Figure 2 is its gas system diagram, Figure 3 is a front view showing its electrode configuration, and Figure 4 is the
5 is a front view showing the configuration of the electrode in the embodiment of the present invention, FIG. 6 is a sectional view taken from the line in FIG. 5, and FIG. 7 is a gas system diagram thereof. 8, 10, 12, and 14 are front views showing the electrode structure of one embodiment of the present invention, and FIGS. 9, 11, 13, and 15 are respectively 8 Figure-Line, 1st
Figure 0 XI-XI line, Figure 12- line and 1st
FIG. 4 is a sectional view taken along the line. In the figure, 1 and 2 are dielectric materials, 1-1, 1-
2, 2-1, 2-2 are inorganic dielectric plates, 1-1
b, 2-1b is the thin part of the dielectric plate, 3, 4, 3
-1, 3-3, 4-1, 4-3 are metal plates, 3b,
4b is the back of the electrode, 3-2, 4-2 are conductive thin films, 3-4, 4-4 are plasma discharge spaces, 5, 5
a, 5b, 5c are discharge spaces, 6 is an AC power source, 7,
7-1 to 7-6 are total reflection mirrors, 8 is a partial reflection mirror, 9
is a gas guide, 10 is a blower, 11 is a heat exchanger,
12 and 13 are refrigerant jacket plates, and 14 and 15 are power supply plates. In addition, one code|symbol in a figure each shows the same or equivalent part.

Claims (1)

[Claims] 1. A discharge space is formed by facing electrodes whose conductor surfaces are covered with a dielectric material, and a high-frequency voltage is applied between the two electrodes while a laser medium is flowing in the discharge space. In a device configured to generate a silent discharge within the discharge space and excite a laser medium within the discharge space to generate a laser,
At least one of the above electrodes is made of a conductor whose surface constituting the discharge space is flat, and the part that covers this flat surface is thinner than the part that covers the other area and has a uniform thickness. 1. A gas laser device comprising: a dielectric material; 2. A dielectric material having a flat portion facing the discharge space and a groove formed to leave a uniform thin layer between the flat surface, and a dielectric material formed so as to be in contact with the surface of the groove of this dielectric material that faces the flat surface. 2. The gas laser device according to claim 1, further comprising an electrode made up of a conductor and a conductor. 3. A power supply plate made of a dielectric material having a flat portion facing the discharge space and a groove formed to leave a uniform thin layer between the flat surface and a conductor covering the opening surface of the groove of this dielectric material. 2. The gas laser device according to claim 1, further comprising an electrode comprising: a plasma discharge medium gas filled in the groove; and a plasma discharge medium gas filled in the groove. 4. A structure in which a groove that is folded multiple times is formed in a dielectric material, a conductor is disposed within this groove, and a total reflection mirror that constitutes an optical resonator is disposed near each folded portion of the groove. A gas laser device according to claim 2 or 3. 5. Claim 2, characterized by having a configuration for passing an insulating coolant through a groove formed in a dielectric material.
The gas laser device according to any one of items 1 to 4.