JPH02237181A - Gas laser device - Google Patents

Abstract

PURPOSE:To prevent a conductor from being sputtered, cause few unstable discharges, lengthen the lifetime, and facilitate increase of the output by forming a microwave mode having a vertical electric field component to the boundary between a first dielectric and plasma and installing a second dielectric on the wall of the conductor. CONSTITUTION:Laser gas which generates plasma by microwave discharge is enclosed in space 67 formed between a conductor wall 65 formed in a part of a microwave circuit and a first dielectric 66 formed opposite said conductor wall 65. A wall surface of a conductor in the space in which the laser gas is enclosed is covered by a second dielectric 71 and a microwave mode having vertical electric field distribution to the boundary between the first dielectric 66 and plasma is formed by the microwave circuit. Thereby spatially uniform plasma is stably maintained for a long time, the wall surface of the connector in the discharge space is protected, deterioration of the laser gas is prevented, and a high-efficiency and long-lived gas laser device is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas laser device that performs laser excitation using microwave discharge.

[Prior Art] FIG. 6 is an external view showing a conventional gas laser device described in, for example, Japanese Patent Application Laid-Open No. 188483/1983.

In the figure, (1) is a magnetron that generates microwaves, (2) is a waveguide that transmits microwaves, (3) is a horn waveguide that widens the width of this waveguide, and (4) is a microwave Coupling window, (5) is the mirror for laser oscillation, (6) is the laser head part, and Figure 7 shows the laser head part (6).
FIG. 6 is a cross-sectional view taken along the line A-A in FIG. 6 showing details. As shown in FIG. 7, the laser head section (6) has a structure of a ridge waveguide type microwave cavity, which is a type of microwave circuit.

In Fig. 7, (61) is the cavity wall following the microwave coupling window (4), (62) and (63) are the ridges formed at the center of the cross section of this cavity wall, and (64) is this cavity wall. This is a groove formed in one of the ridges (62), and (65) is a conductive wall that constitutes a part of the microwave circuit.
4) walls are used. (6B) The conductor wall (65
), and (67) is a dielectric material such as alumina, which is provided opposite to the groove (64).
A discharge space formed between the conductor wall (65) and the dielectric (6B) by covering the discharge space (B).
7) is filled with laser gas such as CO2 laser gas. Also (68) Haridge (62) and (63)
This is a cooling waterway formed in

In the conventional gas laser device configured as described above, the microwaves generated by the magnetron (1) pass through the waveguide (2) and are efficiently matched by impedance matching at the microwave coupling window (4). It is coupled to the laser head section (6). The laser head section (6) has a ridge cavity shape as shown in the cross-sectional view of FIG. 7, and the microwaves are concentrated between the microwave beams (62) and (63).

The strong electric field of these concentrated microwaves creates a discharge space (6
7) The laser gas sealed in the laser gas is destroyed by discharge to generate plasma, and the laser medium is excited. Here, the cooling channel (
68) to cool the discharge plasma, and by appropriately selecting the discharge conditions such as the pressure of the laser gas, the laser conditions are obtained, and the mirror (5) in FIG.
Laser oscillation light can be obtained by forming a laser resonator with another mirror (not shown). Furthermore, when the microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric (66) and the plasma as in the ridge cavity shown in FIG.
Since the dielectric wall (65) and the dielectric wall (65) are placed opposite each other, the dielectric wall (65) also has a vertical electric field component, creating an electric field that penetrates the plasma. At this time, even if a conductive plasma is generated, there is a conductive wall (65) that is several orders of magnitude higher in conductivity than the plasma, which faces the dielectric material (66) that is the microwave incidence window. The terminal current of the wave flows through this conductor wall (85),
The nearby electric field is forced perpendicular to the surface of the conductor wall (65) to maintain the electric field through the plasma. Therefore, the p-type mouth wave penetrates into the plasma, a current flows through the plasma, a spatially uniform discharge plasma is obtained from the continuity of the current, and efficient oscillation is performed.

[Problem to be solved by the invention] In the conventional gas laser device as described above, it is easy to obtain a uniform plasma, but the plasma directly contacts the conductor wall and the conductor is splattered, so the laser gas deteriorates. Furthermore, there was a risk that the conductor wall would be damaged and the life of the device would be shortened.

Further, since electrons are emitted from the metal surface, there is a problem that the discharge tends to become unstable, especially when the pressure of the laser gas is high, and it is difficult to increase the power density of the discharge.

This invention was made in order to solve the above-mentioned shortcomings, and to obtain a gas laser device that does not cause the conductor to spatter, does not easily cause unstable discharge, has a long life, and can easily achieve high output. With the goal.

[Means for Solving the Problems] A gas laser device according to the present invention includes a conductor wall that constitutes a part of a microwave circuit, and a first dielectric member provided opposite to the conductor wall. A laser gas that generates plasma is sealed in the space formed between the two, and the microwave circuit is configured such that the microwave is incident from the first dielectric side, and the first dielectric and the plasma are connected to each other. forming a microwave mode with an electric field component perpendicular to the boundary of
Furthermore, a second dielectric material is provided on the conductor wall surface that comes into contact with the plasma.

[Function] In the present invention, since the second dielectric is disposed on the conductor wall surface that is in contact with the plasma, sputtering of the conductor wall is prevented. Furthermore, electron emission, which causes discharge instability, is also prevented.

[Example] Fig. 1 shows a gas one-noser device according to an embodiment of the present invention, and is a sectional view corresponding to Fig. 7, and Fig. 2 is an explanatory diagram illustrating the state of discharge in the same embodiment. .

In FIGS. 1 and 2, the parts with the same symbols as in FIGS. 6 and 7 indicate the same parts, and (71) is the second dielectric,
To prevent discharge plasma from contacting the conductor wall (65),
It is disposed so as to cover the surface of the conductor wall (B5) in a shape of -. Uniformly covering the surface of the conductor wall (65) with this second dielectric (71) can be achieved by coating it with a ceramic layer. Suitable ceramics include alumina, boron nitride, and aluminum nitride.

Alternatively, a thin plate of quartz glass or Teflon may be bonded.

Next, the operation will be explained.

According to this embodiment, the plasma generated by the microwave discharge does not come into direct contact with the conductor wall (65), and the generated plasma is transferred to the second dielectric layer (65), which is difficult to splatter and is chemically inert. 71) and the first dielectric (66
). Therefore, deterioration of the laser gas due to splatter and chemical reactions hardly occurs, and the conductive walls of the discharge space (67) are not damaged by splatter, electron emission is prevented, and the discharge is prevented. It becomes stable.

Therefore, a microwave excitation type gas laser device with high efficiency and long life can be realized.

At this time, in order to stably obtain a spatially uniform discharge, it is necessary to emit microwaves from only one side of the plasma as described above. Therefore, the second dielectric (71
) is preferably sufficiently thinner than the thickness of the first dielectric (6B). In the case of a ceramic layer, when its thickness is 1/10 or less of the thickness of alumina, which is the first dielectric (6B), a large amount of microwave energy is applied from the first dielectric (66) side of the plasma. It was confirmed that the portion was injected.

Here, consider the conditions under which the electric field penetrating the plasma (70) is maintained as shown in FIG. 2 even if the second dielectric (71) is present. In order for the penetrating electric field to be maintained, the termination impedance of the incident microwave, i.e. the second dielectric (
The impedance of the plasma (71) as a capacitance must be smaller than the resistance of the plasma (70). This condition is such that the value obtained by dividing the thickness d of the second dielectric (71) by the dielectric constant ε of the second dielectric is less than the value obtained by dividing the resistivity ρ of the plasma by the vacuum wave impedance Zo I am satisfied with small things. That is, if ε'Z0, the electric field penetrating the plasma (70) is maintained even if the second dielectric (7l) is provided, and a spatially uniform discharge can be obtained, as in the conventional device. Become.

Since the resistivity ρ of the plasma changes depending on the conditions of the filled gas and the microwave power density, it is difficult to determine it in advance so as to satisfy the condition of equation (1).

In reality, it is necessary to experimentally find the optimum values of d and ε without examining the stability and uniformity of the discharge.

``Figure 3 is a sectional view showing another embodiment in which the structure of the laser head section (6) is different. In FIG. 3, (651) is a ridge-shaped conductor wall. This laser head part (6) narrows the width W of the ridge (63) to further concentrate the electric field between the ridge (63) and the ridge-shaped conductor wall (651), and discharges only in this part. However, as shown in Figure 4(a), the discharge tends to be concentrated in a filament shape (671).
Discharge tends to become unstable. This is thought to be due to electron emission from the conductor wall.

Therefore, as shown in FIG. 4(b), by disposing a second dielectric material (71) on the surface of the ridge-like conductive wall (651.), the discharge (672) spreads evenly. can do.

By the way, is it a conductor? This is similar to the embodiment shown in FIG. 1 in that (651) is protected from spatter caused by plasma and deterioration of the laser gas is prevented.

FIG. 5 is a sectional view showing still another embodiment in which the structure of the laser head section (6) is different. In this embodiment, a discharge is generated in the portion of the ridge (63) and the conductor wall (65) facing the ridge (63) and in the vicinity thereof.
As shown in the figure, the part that becomes the microwave incidence window (881)
A rectangular cylindrical dielectric body is provided, which includes a portion (711.) that covers the conductor wall (65), and portions that form side surfaces on both sides. Laser gas is sealed inside this rectangular tube.

Note that (31) is a taber portion for impedance matching.

In this example as well, if there is no (711) part of the dielectric, the discharge becomes unstable, but by providing (711),
Improved.

In addition, in this example, the portion (6 6 1) serving as the microwave incidence window corresponds to the first dielectric, and the conductor wall (6 6 1) corresponds to the first dielectric.
65) corresponds to the second dielectric. Also, the thicknesses d and d of the (861) and (711) parts of the dielectric do not necessarily have to be the same.
2 Yes.

The conductor wall (65) protects against splatter caused by plasma.
This is also the same as in the previous two embodiments in that the deterioration of the laser gas is prevented.

Furthermore, in a laser device that uses a laser gas containing highly chemically active halogen gas, such as an excimer laser device, a material that does not react with the halogen group should be used as the second dielectric (71). Needless to say.

[Effects of the Invention] As explained above, the present invention provides an electric conductor wall formed between a conductor wall formed in a part of a microwave circuit and a first dielectric body provided opposite to the conductor wall. A laser gas that generates plasma by microwave discharge is sealed in a space where the laser gas is sealed, and a conductive wall of the space in which the laser gas is sealed is covered with a second dielectric material, and a microwave circuit is used to cover the wall surface of the conductive material with the first dielectric material. Since it is configured to form a microwave mode with an electric field distribution perpendicular to the boundary with the plasma, a spatially uniform plasma can be stably maintained over a long period of time, and the walls made of conductors in the discharge space can be protected. At the same time, deterioration of the laser gas is also prevented, and a gas laser device with high efficiency and long life can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a gas laser device according to an embodiment of the present invention, and is a sectional view corresponding to FIG. 7, FIG. 2 is an explanatory diagram illustrating the state of discharge in the same embodiment, and FIG. 3 is a laser head Sectional view showing another embodiment with a different structure of the section, No. 4
Figure (a) is an explanatory diagram showing the state of discharge in the absence of the second dielectric, FIG. 4(b) is an explanatory diagram showing the state of discharge in the presence of the second dielectric, and FIG. A cross-sectional view showing still another embodiment with a different structure of the laser head part, FIG. 6 is an external view showing a conventional gas laser device, and FIG. 7 is taken along A-A in FIG. 6.
FIG. In the figure, (85) is a conductive wall forming part of the microwave circuit, (66) is the first dielectric, (67) is the discharge space, (70) is the plasma, and (71) is the second dielectric. It is a dielectric. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 1

Claims (1)

[Claims] In a gas laser device that generates plasma by microwave discharge in a microwave circuit and performs laser excitation, the gas laser device includes a conductive wall forming a part of the microwave circuit, and a first conductive wall provided opposite to the conductive wall. A laser gas that generates the plasma is sealed in a space formed between the first dielectric body and the microwave circuit, and the microwave circuit is configured such that the microwave is incident from the first dielectric side, A second dielectric is disposed on the conductor wall so that a microwave mode having an electric field component perpendicular to the boundary between the first dielectric and the plasma is formed, and the plasma does not come into contact with the conductor wall. A gas laser device characterized by: