JPH038381A - Gas laser device - Google Patents

Abstract

PURPOSE:To perform stabilized electric discharge between electrodes by reducing the thickness of dielectric which covers discharge electrodes on opposite sides as it approaches the center, but increasing the thickness as it approaches the ends. CONSTITUTION:When an attempt is made to apply voltage to an electrode 21 in a power supply 7 so that a space electric field reaches a breakdown valve of laser gas, electric discharge is produced in a space. The surface of a discharge section 22a of a dielectric 22 on the power supply side is designed to be curved. The thickness of the dielectric 22 is reduced as it approaches its center while the thickness is increased as it approaches its ends so that it may come into close contact with the convex surface of the electrode 21 on the discharge side. Therefore, the electric field is weaker as it covers the ends of he metal and electrode 21, which minimizes the effect of edge of the electrode 21 and makes constant the distribution of power density so that homogeneous discharge power distribution may be obtained between the discharge sections 22a of the dielectric 22. Therefore, it is possible to obtain stabilized discharge at high power density. At the same time, a total thickness B of a non-discharge section 22b of the dielectric 22 is formed to be greater than the thickness of the discharge section 22a in the central part, which reduces the capacitance of the non-discharge section 22b. On the other hand, as for the discharge region, the discharge power density is not reduced between the discharge sections 22a and 22b, which makes it possible to prevent the drop in the efficiency of laser oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrode structure in a gas laser device, particularly an AC discharge excited gas laser.

[Prior Art] Figures 4 and 5 show a three-axis orthogonal type, which is a typical system of a conventional CO2 gas laser device shown in Japanese Patent Publication No. 132-39555, that is, a laser gas flow direction, a discharge FIG. 2 is a vertical cross-sectional view and a cross-sectional view showing a CO2 gas laser device in which the laser beam direction and the laser optical axis direction are orthogonal to each other.

In the figure, (la) and (lb) are a pair of discharge electrodes arranged oppositely, (2) is a discharge gap, (3) is a laser gas circulation blower, (4) is a heat exchanger, and (5) is a Housing, (6) is bushing, (7) is AC power supply, (8)
is a total reflection mirror, (9) is a partially transmitting mirror, and (lO) is a laser beam.

Next, the operation will be explained.

A bushing (6) is placed between the discharge electrodes (la) and (lb).
) When applying an AC high voltage from AC @ i (7), a discharge called silent discharge is generated in the discharge gap (2). A laser gas consisting of Go, N, and He of several Torr to several tens of Torr is sealed in the housing (5), and the CO2 molecules in the laser gas are excited by silent discharge, causing vibrations between specific vibration orders. Population inversion (Popu
A total reflection mirror (8) is installed between the discharge gap (2) of this discharge excitation part to generate a
) and a partially transmitting mirror (9) having an appropriate transmittance are placed facing each other, the laser beam (lO
) will appear.

When the gas temperature in the discharge excitation section increases due to heat generated by discharge, the above-mentioned population inversion cannot be performed efficiently. In order to carry away this heat with the laser gas flow, the laser gas is circulated within the housing (5) via the heat exchanger (4) by a laser gas circulation blower (3). Normally, the gas flow velocity in the discharge gap (2) is several tens of meters/see.

The above is the operating principle of the gas laser device, but the discharge electrode (
The structures of la) and (lb) will be explained in detail below.

FIG. 6 is a sectional view showing the electrode structure of a conventional gas laser device.

In the figure, (11) is a metal electrode connected to an AC power source (7), and (12) is a dielectric that is in close contact with the metal electrode (11) and has a discharge part (12a) and a non-discharge part (12b). .

The discharge part (12a) of the dielectric (12) is a metal electrode (11)
The thickness of the discharge part (12a) is designed to be thinner than the thickness of the non-discharge part (12b), so that when the dielectric constant εS of the dielectric material (12) is small, has a structure that allows the discharge area to be limited to some extent.

Therefore, when the AC voltage of the AC power supply (7) is applied between the discharge electrodes (la) and (lb) to generate a discharge, the discharge occurs at the discharge part (12) of the dielectric (12) as shown in FIG. 12
a).

(12a) It occurs restricted to the region between.

[Problem to be solved by the invention] In the conventional gas laser device as described above, the discharge electrode (l
a), the discharge part (12) of the dielectric (12) covering part of the discharge side surface and side surface of the metal electrode (11) of (lb);
Although the thickness of a) is uniform to make the power density uniform, the electric field concentration at the edge part of the metal electrode (11) is significant, and the power density distribution in the metal electrode (1) is as shown in Figure 7. It has been found through observation that it is high at the ends of the metal electrode (1) and low at the center.

Therefore, the discharge part (12a) of the dielectric (12), (
There was a problem that a homogeneous discharge power density could not be obtained between the discharge electrodes (la) and (lb), and a homogeneous and stable discharge could not be obtained between the discharge electrodes (la) and (lb).

Further, when the dielectric (12) is formed of a high dielectric constant material having a large relative permittivity εS, such as titanium oxide TlO2 having a relative permittivity εs of 90, the dielectric (12) ) of the non-discharge part (jL2b) (41
) increases, the discharge spreads over the entire area including the non-discharge portion (12b) of the dielectric (12), making it impossible to limit the discharge area, reducing the discharge power density and reducing laser oscillation efficiency. There were also points.

This invention was made in order to solve the above-mentioned problems, and it is possible to obtain a uniform discharge power density between the discharge parts of the dielectric, and the dielectric is made of a high-permittivity material with a large relative permittivity. An object of the present invention is to obtain a gas laser device in which the laser oscillation efficiency does not decrease even when the laser oscillation efficiency is reduced.

[Means for Solving the Problems] In the gas laser device according to the present invention, the discharge side surfaces of the discharge part and the non-discharge part of the dielectric that constitute a part of the discharge electrode are flat, and the power supply side of the discharge part of the dielectric is flat. The surface is curved, and the thickness of the discharge part is thinner in the center and thicker toward the ends, and the thickness of the entire non-discharge part or the boundary area with the discharge part is the thickness of the central part of the discharge part. It is made to be thinner.

[Function] In the present invention, the discharge side surface of the dielectric that constitutes a part of the discharge electrode is a flat surface, the power feeding side surface of the discharge part is a curved surface, and the thickness of the discharge part is made thinner in the center and thinner in the ends. Since the metal electrode is formed so that it becomes thicker as it goes, the electric field becomes weaker at the edge of the metal electrode, so the electric field concentration at the edge part decreases, and the power density distribution in the metal electrode becomes uniform, and the electric field becomes weaker at the edge of the metal electrode. A homogeneous discharge power density is obtained, resulting in stable discharge between the discharge electrodes.

In addition, since the thickness of the entire non-discharge portion of the dielectric material or the boundary area with the discharge portion is made thinner than the thickness of the central portion of the discharge portion, the capacitance of the non-discharge portion other than the discharge portion is reduced.
The discharge area is limited to the discharge part. Therefore, the discharge power density between the discharge parts does not decrease, and a decrease in laser oscillation efficiency is prevented.

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

FIG. 1 is a sectional view showing a discharge electrode according to an embodiment of the present invention. In the figure, (la) and (lb) are discharge electrodes, (2) is a discharge gap, (7) is an AC power supply, and (21)
is a metal electrode with a convex surface on the discharge side connected to the AC power source (7), and (22) is a dielectric material that is in close contact with the discharge side of the metal electrode (21) - a part of the surface and side part. (22a) and a non-discharge part (22b), the discharge side surfaces of the discharge part (22a) and the non-discharge part (22b) are formed flat, and the discharge part (22b) has a flat surface.
The power feeding side surface of 2a) is formed into a curved surface. Discharge part (
22a) is formed so that its thickness is thinner in the center and thicker toward the ends. The non-discharge portion (22b) has a thickness B that is thinner than the thickness A of the central portion of the discharge portion (22a). (30) is an insulating member for preventing creeping discharge that is adhered to the power feeding side surface of the non-discharge portion (22b) of the dielectric (22), and the material used is a material whose dielectric constant is smaller than that of the dielectric (22). It is being said.

In the gas laser device configured as described above, an AC voltage is applied to the metal electrode (11) from the AC power source (7).

(11) is applied, and when the spatial electric field reaches the destruction value of the laser gas, a discharge occurs in the discharge space. In this case, the power feeding side surface of the discharge part (22a) of the dielectric (22) is made into a curved surface, the thickness of the discharge part (22a) is thinner in the center and thicker toward the ends, and the metal electrode ( The metal electrode (21) is in close contact with the convex discharge side surface of the metal electrode (21).
Since the electric field is weaker at the edge of the metal electrode (1), the influence of the edge part of the metal electrode (1) is small and the power density distribution in the metal electrode (21) becomes uniform, and the electric field at the discharge part (2) of the dielectric (22) becomes uniform.
A homogeneous discharge power density is obtained between 2a) and (22a), and stable discharge is achieved between the discharge parts even at high power density.

Furthermore, since the overall thickness B of the non-discharge portion (22b) of the dielectric (22) is formed to be thinner than the thickness of the central portion A of the discharge portion (22a), the capacitance of the non-discharge portion (22b) is reduced. The influence of the capacitance component becomes smaller, and the discharge area becomes the discharge part (
22a). Therefore, the discharge part (22a),
The discharge power density between (22b) does not decrease, and a decrease in laser oscillation efficiency is prevented.

FIGS. 2 and 3 are cross-sectional views showing discharge electrodes according to other embodiments of the present invention. In the embodiment shown in FIG. 1, the thickness of the non-discharge portion (22b) of the dielectric (22) is uniformly thin, but in another embodiment shown in FIG.
A groove (23) is provided in the boundary area between the non-discharge part (22b) and the discharge part (22a), and the thickness of the boundary area is made thinner.

By doing this, the capacitance in the boundary area decreases, and the electric field in other areas becomes weaker as they move away from the metal electrode (21), and the discharge area is limited to the discharge part (22a). This embodiment has the same functions and effects as the embodiment shown in FIG.

Furthermore, as in the embodiment shown in FIG.
) If the bottom of the groove (24) provided in the groove (24) is made into a curved surface, the power density distribution will be made more homogeneous.

[Effects of the Invention] As explained above, the present invention has a curved surface on the power supply side of the discharge part of the dielectric, the thickness of the discharge part is thinner in the center part and becomes thicker toward the ends, and the thickness of the metal electrode is made thinner. Since the electric field is weaker at the edges and the influence of the edges is reduced, the power density distribution in the metal electrode is uniform, resulting in stable discharge due to homogeneous discharge power density between the discharge parts of the dielectric material. Furthermore, by forming the entire non-discharge area of the dielectric material or the thickness of the boundary area with the discharge area to be thinner than the thickness of the central part of the discharge area, the capacitance of the non-discharge area is reduced. Since the influence of the capacitance component is reduced and the discharge area is limited to the discharge area, the discharge power density does not decrease.
A decrease in laser oscillation efficiency is prevented, and a homogeneous, high-density, stable discharge with good laser oscillation efficiency is obtained in the discharge space, which has the effect of increasing the quality of the laser beam and making the device more compact.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a discharge electrode according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view showing a discharge electrode according to another embodiment of the present invention, FIG. 3 is a cross-sectional view showing a discharge electrode according to still another embodiment of the present invention, and FIG. 4 is a longitudinal cross-sectional view showing a conventional gas laser device. 5 is a cross-sectional view showing the same gas laser device, FIG. 6 is a sectional view showing the electrode structure of the same gas laser device, and FIG. 7 is a cross-sectional view showing the electrode structure of the same gas laser device. A diagram showing the power density, and FIG. 8 is a cross-sectional view showing an electrode structure using a dielectric material of a high permittivity material. In the figure, (la) and (lb) are discharge electrodes, (7)
is an AC power supply, (21) is a metal electrode, (22) is a dielectric,
(22a) is the discharge part, (22b) is the non-discharge part, A is the thickness of the central part of the discharge part, and B is the thickness of the non-discharge part. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] Discharge electrodes formed by covering the surface of a metal electrode with a dielectric consisting of a discharge part and a non-discharge part are made to face each other to constitute a discharge space, and an alternating current voltage is applied between the pair of discharge electrodes. In the gas laser apparatus, the discharge side surfaces of the discharge part and the non-discharge part of the dielectric are flat, and the discharge side surfaces of the discharge part and the non-discharge part of the dielectric are flat, and The power feeding side surface of the discharge part is a curved surface, the thickness of the discharge part is thinner in the center part and becomes thicker toward the ends, and the thickness of the entire non-discharge part or the boundary area with the discharge part is reduced. A gas laser device characterized in that the thickness of the discharge part is thinner than that of the central part of the discharge part.