JPH07105540B2 - Gas laser device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas laser device that performs laser excitation using microwave discharge.

[Prior Art] FIG. 3 is a perspective view showing a conventional gas laser device, FIG. 4 is a sectional view of the gas laser device, and FIG. 5 is a sectional view taken along line VV of FIG. In the figure, (1) is a magnetron that is a microwave oscillator, (2) is a waveguide that is a microwave transmission path, (3) is a horn waveguide that widens the width of the waveguide (2), and (4) Is a microwave coupling window, (5) is a partial reflection mirror for laser oscillation, (6) is a laser head portion which is a microwave circuit, and (7) is a total reflection mirror for laser oscillation.

This laser head portion (6) has a structure of a ridge waveguide type microwave cavity which is a kind of microwave circuit. In FIG. 4, (61) is a cavity wall following the microwave coupling window (4), (62) and (63) are ridges formed in the central part of the cross section of the cavity wall, and (64) is this. One ridge (6
The groove formed in 2), (65) is a conductor wall forming a part of the microwave circuit, and the wall surface of the groove (64) is used. (66) is a dielectric such as alumina provided facing the conductor wall (65), and (67) is the conductor when the dielectric (66) covers the groove (64). A discharge space is formed between the wall (65) and the dielectric (66), and a laser gas such as CO ₂ laser gas is enclosed in the discharge space (67). Further, (68) is a cooling water channel formed in the ridges (62) and (63).

In the conventional gas laser device configured as described above, the microwave generated by the magnetron (1) is spread by the horn waveguide (3) through the waveguide (2), and the microwave coupling window ( By performing impedance matching in 4), it is efficiently coupled to the laser head section (6). The laser head portion (6) has a ridge cavity shape as shown in FIG.
Concentrate during (63). The concentrated electromagnetic field of microwaves causes the discharge of the laser gas sealed in the discharge space (67) to generate plasma, which excites the laser medium. Here, cooling water is caused to flow through the cooling water passage (68) to cool the discharge plasma, and laser oscillation conditions are obtained by appropriately selecting discharge conditions such as the pressure of the laser gas, and the partial reflection mirror (5) and total reflection mirror (5) are obtained. Laser oscillation light can be obtained by forming a laser resonator with the reflection mirror (7). At this time, in the gas laser device, the conductor wall (65) forming a part of the microwave circuit and the dielectric (66) which is provided so as to face the conductor wall (65) and serves as a microwave incident window. ) And the discharge space formed between them (67)
In order to cause microwave discharge in, the microwave is incident only from one side of the plasma, and the phenomenon that the microwave mode of the coaxial mode in which the plasma is the inner conductor dominates does not occur. Discharge in microwave mode can be performed. Also the fourth
When the microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric (66) and the plasma like the ridge cavity shown in the figure, the dielectric (66) and the conductor wall (65 ) Are installed so as to face each other, so that the electric conductor wall (65) also has a vertical electric field component, and an electric field penetrating the plasma can be generated. At this time, even if conductive plasma is generated, it faces the dielectric (66) that is the microwave entrance window and has a conductive wall (65) that is several orders of magnitude more conductive than plasma.
Because of this, the terminating current of the incident microwave flows through this conductor wall (65), and the electric field in the vicinity of the conductor wall (65) is forced to be perpendicular to the surface of the conductor wall (65). The electric field passing through is maintained. Therefore, the microwave penetrates into the plasma, a current flows through the plasma, and a spatially uniform discharge plasma can be obtained from the continuity of the current.

[Problems to be Solved by the Invention] In the conventional gas laser device as described above, the conductor wall (65) forming a part of the laser head portion (6) and the conductor wall (65) facing each other are disposed. A laser gas for generating plasma by microwave discharge is enclosed in a discharge space (67) formed between the dielectric (66) and the microwave circuit (6) and the dielectric (66) and the plasma. A microwave mode having an electric field component perpendicular to the boundary with is formed so that a spatially uniform microwave discharge plasma can be generated, but the discharge space (67) is partitioned airtightly, Since the discharge space (67) needs to be cooled through the dielectric (66), it has good metal-bonding properties with the ridge (62) in which the dielectric (66) is made of metal, and has good thermal conductivity, such as alumina and aluminum nitride. Formed of a material with a relatively large dielectric constant Therefore, the effect of shortening the microwave wavelength due to the large dielectric constant is large, the length of the axial discharge node S in the discharge space (67) is short, and many discharge nodes S can be formed. There is a problem that it is difficult to uniformly couple the waves to the plasma, and the plasma is not uniformly generated in the discharge space.

The present invention has been made to solve the above-mentioned problems, and makes the microwave discharge plasma generated in the discharge space uniform and stable in the axial direction, and enables high-efficiency, high-power laser operation. The purpose of the present invention is to obtain a gas laser device.

[Means for Solving the Problems] In the gas laser device according to the present invention, the dielectric of the microwave circuit for performing laser excitation by generating plasma in the laser gas by the discharge of microwaves is a metal junction located on the discharge space side. The first ceramic material layer having good properties and the second ceramic material layer having a low dielectric constant located on the opposite side of the discharge space are formed.

[Operation] In the present invention, the dielectric of the microwave circuit is the second ceramic layer located on the discharge space side and having a good metal-bonding property and the second ceramic layer located on the opposite side to the discharge space and having a low dielectric constant.
Since it is formed from the ceramic material layer, the average dielectric constant of the entire dielectric is reduced, the wavelength shortening effect of the microwave can be reduced, and the length of the axial discharge node in the discharge space is lengthened to increase the It becomes easier to couple the waves into the plasma uniformly, and the discharge volume increases,
Plasma is uniformly generated in the discharge space.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view of a microwave circuit. In the figure, the same components as those of the conventional example are designated by the same reference numerals, and the description of the duplicate components is omitted. (661) is a dielectric (6
1) Thin thickness consisting of alumina that forms part of 6)
The ceramic material layer is located on the discharge space (67) side and is joined to the metal ridge (62) by, for example, an adhesive. (662) is a second thick ceramic material layer made of boron nitride that constitutes a part of the dielectric (66), and is located on the opposite side of the discharge space (67).

In the gas laser device configured as described above, the dielectric (6
6) is a first ceramic material layer (661) made of alumina located on the discharge space (67) side and a second ceramic material layer (662) made of boron nitride located on the opposite side of the discharge space (67). The alumina of the first ceramic material layer (661) has good metal bondability and a relative permittivity of about 10, and is made of the second ceramic material layer (66).
The boron nitride of 2) has poor metal-bonding property, but since the relative dielectric constant is about 3.5, the average dielectric constant of the whole dielectric (66) is smaller than that of the dielectric (6) made of alumina alone. , The effect of shortening the microwave wavelength is reduced. Therefore, as shown in FIG. 2, the length of the axial discharge node S in the discharge space (67) becomes longer, which makes it easier to uniformly bond the microwave to the plasma and also increases the discharge volume. As a result, stable and uniform plasma is generated in the discharge space (67), and laser output can be obtained with high efficiency and large output.

Further, the thickness of the first ceramic material layer (661) of alumina is thin, and the thickness of the second ceramic material layer (662) of boron nitride is thick. This is because the average dielectric constant of the entire dielectric (66) composed of (661) and (662) is set to be as small as possible. Further, the first ceramic material layer (661) is located on the discharge space (67) side, and the second ceramic material layer (662) is located on the opposite side to the discharge space (67). Ceramic material layer (66
Alumina of 1) has a good metal bonding property, and boron nitride of the second ceramics material layer (661) has a poor metal bonding property, so that the discharge space (67) is kept airtight. This is because the part which is one surface is required to have a good metal bondability capable of airtightly bonding to the metal ridge (62), that is, the first ceramic material layer (661) of alumina.

In this example, the first ceramic material layer (66
Although 1) is made of alumina, any material having good metal bonding property such as alumina nitride may be used. Not only can alumina and aluminum nitride be bonded to a metal with an adhesive, but the surface of a portion that comes into contact with the metal can be metalized to perform metal bonding such as soldering or brazing with the metal. Although the second ceramic material layer (662) is made of boron nitride, any material such as a boron nitride composite material having a small dielectric constant may be used.

Further, in this embodiment, the gas laser device in which the waveguide (2), the horn waveguide (3), and the laser head portion (6) are arranged in the direction orthogonal to the laser optical axis will be described. However, it goes without saying that the present invention can be applied to a gas laser device in which a waveguide and a laser head part are arranged in parallel in a direction along the laser optical axis.

EFFECTS OF THE INVENTION As described above, according to the present invention, the dielectric of the microwave circuit has the dielectric constant located on the opposite side of the discharge space and the first ceramic material layer located on the discharge space side and having good metal bonding property. Since it is formed of a low second ceramics material layer to reduce the average dielectric constant of the entire dielectric to reduce the effect of shortening the wavelength of the microwave, the node of the axial discharge in the discharge space is reduced. As the length becomes longer, it becomes easier to bond microwaves to plasma uniformly, and the discharge volume also increases. Plasma is generated stably and uniformly in the discharge space in the longitudinal direction, and laser output is highly efficient and large output. There is an effect that can be obtained in.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view of a microwave circuit, FIG. 3 is a perspective view showing a conventional gas laser device, and FIG. 4 is a sectional view of a gas laser device. , Fifth
The drawing is a sectional view taken along line VV of FIG. In the figure, (6) is a laser head portion (microwave circuit), (66) is a dielectric, (661) is a first ceramic material layer, and (662) is a second ceramic material layer. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A microwave oscillator that oscillates microwaves, a microwave transmission line that transmits microwaves, and a discharge of the microwaves transmitted by the microwave transmission line,
A microwave circuit for generating plasma in a laser gas for laser excitation is provided, and the laser gas is sealed in a discharge space provided in the microwave circuit and having a dielectric serving as a microwave entrance window on one surface. A microwave excitation type gas laser device configured to form a microwave mode having an electric field component perpendicular to a boundary between the dielectric and plasma generated in the laser gas by the microwave circuit, Is characterized in that it is formed of a first ceramics material layer located on the discharge space side and having good metal bonding properties, and a second ceramics material layer located on the opposite side of the discharge space and having a low dielectric constant. Gas laser device.