JPH02237183A - Gas laser device - Google Patents

Abstract

PURPOSE:To obtain high laser output with high efficiency by combining a microwave in a dielectric from the side face thereof through a combination window which is formed in a wall surface, where a microwave electric field in a microwave transmission path is almost eliminated, and extends in the direction of a laser optical axis. CONSTITUTION:A microwave transmission path 2 and a microwave circuit 6 are installed parallel along a laser optical axis and a microwave is combined from the side face 661 of a dielectric 66 through a combination window 41 which is formed in a wall surface, where a microwave electric field in the microwave transmission path 2 is almost eliminated, and extends in the direction of the laser optical axis. Therefore, while transmitted in the transmission path 2, the microwave is combined little by little from the microwave transmission path 2 to the dielectric 66 through the combination window 41 extending in the direction of the laser optical axis and through the side face 661 of the dielectric, and a microwave mode mainly including vertical electric field component to the boundary between the dielectric 66 and plasma is formed. Thereby uniform discharge in the direction of the laser optical axis is obtained to make a compact device of high laser excitation efficiency and high output.

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.

[Conventional technology]

FIG. 7 is a perspective view showing a conventional gas laser device described in, for example, Japanese Patent Application Laid-open No. 186483/1983. In the figure, (1> is a magnetron that generates microwaves, 2> is a waveguide that transmits the microwaves generated by magnetron (1), and (3> is a horn that widens the width of this waveguide. The waveguide, (4> is the microwave coupling window, (5) is the mirror for laser oscillation, and (6) is the laser head. 8th
The figure is a sectional view taken along the line B-B in FIG.
) is enlarged to show details. As shown in FIG. 8, the laser head section <<6>> has a structure of a ridge waveguide type microwave cavity, which is a type of microwave circuit. In Fig. 8, (61) is the cavity wall following the microwave coupling window (4), (62). (63) is this cavity wall 61
The ridge formed in the center of the cross section of Therefore, the wall surface of the groove (64) is used. 〈66〉 is a dielectric material such as alumina, which is provided facing the conductive wall 65〉, and 〈67〉 is a dielectric material such as alumina, which is provided opposite to the conductive wall 65〉.
By covering the conductor wall (65) and the dielectric material <66
), and a laser gas such as CO laser gas is sealed in this discharge space (67).
3) is a cooling water channel formed in

In the conventional gas laser device configured as described above, microwaves generated by the magnetron (1) pass through the waveguide (2) and are spread by the horn waveguide (3). 3) is efficiently coupled to the laser head section (6) by performing impedance matching at the microwave coupling window 41 provided on the wall surface (4) at the end of the section.

The laser head part (6) has a ridge-cavity shape as shown in Fig. 8, so the microwave beam
．． Concentrate between (63). Due to the strong electric field of the concentrated microwaves, the laser gas sealed in the discharge space (67) is destroyed by discharge to generate plasma, and the laser medium is excited. Here, the laser excitation conditions are obtained by flowing cooling water into the cooling channel (68) to cool the discharge plasma and appropriately selecting the discharge conditions such as the pressure of the laser gas. ) and another mirror (not shown) to form a laser resonator, the laser oscillation light can be returned.

In addition, when a microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric material (66) and the plasma, as in this ridge cavity, the dielectric material (66) and the conductor wall <65 ) are installed facing each other, so conductive walls (
65> also has a vertical electric field component, creating an electric field that penetrates the plasma. At this time, even if conductive plasma is generated, the dielectric material (66
Because there is a conductor wall (65) facing the conductor wall (65), which has several orders of magnitude higher conductivity than the plasma, the terminal current of the incident microwave flows through this conductor wall (65), and the current near the conductor wall (65) The electric field is forced perpendicular to the surface of the conductor wall (65), maintaining an electric field through the plasma.This allows the microwave to penetrate into the plasma, causing a current to flow through the plasma, and from the continuity of the current. A spatially uniform discharge plasma is obtained, and laser oscillation is performed.

[Problem to be solved by the invention]

In the conventional gas laser device as described above, since the coupling window (4) is provided at the end of the waveguide in the transmission direction, unless the microwave is spread uniformly by the horn waveguide (3),
Uniformity of discharge in the length direction, that is, in the direction of the laser optical axis cannot be ensured. Many microwave modes can be excited in the horn waveguide (3), and when connecting from the rectangular waveguide (2) to the horn waveguide (3), the central Microwaves tend to be stronger in certain areas.

Furthermore, since the spread of microwaves is affected by the shape of the horn and the load impedance at its tip, the manner in which the microwaves spread changes due to the interaction between the discharge and the microwaves, and it is important to find conditions that spread the microwaves uniformly. difficult. Therefore, it has been difficult to ensure uniformity of discharge in the direction of the laser optical axis, and it has been difficult to further increase the efficiency of laser oscillation.

Along with this, there is a problem that power is easily concentrated in one part, so large amounts of power cannot be input and high output cannot be returned.This invention was made to solve the above problems. , the uniformity of the discharge in the direction of the optical axis of the laser is easy to calculate.
The aim is to create a high-efficiency, high-output gas laser device.

[Means to solve the problem]

The gas laser device according to the present invention has a microwave transmission line and a microwave circuit arranged in parallel along the laser optical axis, and a laser beam provided on a wall surface where the microwave electric field in the microwave transmission line becomes almost zero. Microwaves are coupled from the sides of the dielectric through a coupling window extending in the axial direction.

[Effect]

The gas laser device of the present invention gradually couples the microwaves from the microwave transmission path to the dielectric material through the coupling window extending in the direction of the laser optical axis and the side surface of the dielectric material while the microwaves are transmitted through the transmission path. , a microwave mode dominated by an electric field component directly at the boundary between the dielectric and the plasma is formed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a perspective view showing a gas laser device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1. In this example, a rectangular waveguide (2), which is a microwave transmission path, and a laser head (6), which is a microwave circuit, are arranged in parallel along the laser optical axis, and the coupling window <4l> is used to guide the waveguide. Pipe (2
>> It is installed on the wall surface where the microwave electric field inside is almost zero, and is configured to extend in a long and narrow direction in the direction of the laser optical axis. Therefore, microwaves are coupled from the side surface of the dielectric through the microwave coupling window (41) provided on the side of the waveguide (2).

With such a structure, an electric field is generated in the waveguide (2) as indicated by arrow E in FIG. That is,
TEII! The mode is excited and the microwave coupling window (41
) consists of an elongated slit provided on the wall surface (4) parallel to the electric field E in the waveguide (2>, that is, the wall surface where the electric field is zero).A coupling window (41) provided at such a position
In order to couple microwaves into the laser head <6>, an electric field component parallel to this end face (661) is dominant on the end face (661) of the dielectric body <66> that extends in a direction perpendicular to the plane of the paper. Microwaves are excited, and a vertical electric field is generated at the boundary between the dielectric (66) and the discharge space (67). Microwaves are supplied to the discharge space 67 through this dielectric (66) to generate a discharge. Even if a discharge occurs and a plasma is generated, the electric field that penetrates the plasma is maintained and a uniform discharge is maintained. Since the transmission direction of the microwave in the waveguide (2) is parallel to the optical axis direction of the laser head 6〉, that is, parallel to the longitudinal force direction of the discharge space, the microwaves in the waveguide (2) are It is gradually coupled to the laser head (6) through a coupling window (4l) provided in the laser head (6). Unlike the horn waveguide, the microwave mode in the waveguide (2) is only the T E I9 mode, and the manner of coupling can be freely adjusted by changing the shape of the coupling window (41).

Therefore, if the width of the coupling window (41) is configured appropriately,
It can be easily and uniformly coupled in the direction of the laser optical axis.
The distribution of discharge in this direction can be made uniform. In this way, the discharge becomes uniform both in the depth direction and in the optical axis direction, making it easy to bring the entire discharge space into a state suitable for excitation of the laser. Furthermore, laser oscillation mirrors <<5>> and (51)
Efficient laser oscillation can be performed by the laser resonator configured by the following. In addition, the discharge space (67
) If the discharge power density increases too much, the efficiency of laser emission may decrease. Therefore, if discharge is uneven and power concentration occurs even in a part, the upper limit of the input power is determined by the discharge power density in this part, and the power that can be input into the discharge space as a whole becomes smaller. On the other hand, in the case of uniform discharge without power concentration as obtained by the present invention, the power that can be input becomes large. Therefore, with the device of the present invention, a large oscillation output can be obtained.

FIG. 3 is a sectional view perpendicular to the laser optical axis showing a gas laser device according to another embodiment of the invention.

The gas laser device according to this embodiment uses a cylindrical waveguide as the waveguide (2l), and has laser heads (6) arranged in parallel on the side surface of the waveguide (2l). In addition, a wall surface that is approximately parallel to the electric field direction at the center of the waveguide, indicated by arrow E in the figure,
That is, an elongated coupling window (42) is provided in the direction perpendicular to the plane of the paper on the plane where the electric field in the waveguide (21) is almost zero. Therefore, the same microwave coupling as in the above embodiment is performed, and the discharge in the direction of the laser optical axis can be easily made uniform.

FIG. 4 is a sectional view showing a laser head according to still another embodiment of the invention. In this example, the discharge space (
67) is composed of a flat and elongated dielectric tube (662) inserted into the groove of the ridge (62), so that the microwave is mainly transmitted from the side surface (663) of the dielectric tube (662) to the dielectric tube (662). is bonded to a dielectric portion that constitutes the upper wall surface of. In this way, the microwave is coupled to the discharge space (67) in substantially the same manner as in the above embodiment, and a uniform discharge can be generated across the discharge space in the direction of the laser optical axis. In addition, a dielectric tube with a closed periphery (
662), it has the advantage that the discharge gas can be easily sealed.

FIG. 5 is a sectional view showing still another embodiment of the invention. In this example, from the waveguide (2〉) to the coupling window (
41> to the dielectric body (66>) is performed in the same manner as in the above embodiment, and a uniform discharge can be easily generated in the direction of the laser optical axis.Furthermore, the discharge space (671).
Since <672> is provided on both sides of the dielectric (66), more power can be injected into the entire discharge space in total, and a beam with high output can be obtained with the two laser beams.

FIG. 6 is a perspective view showing still another embodiment of the invention. In this example, the combining windows (43), (44) . 《
45) was divided and provided. In this way, by dividing the elongated coupling window into a plurality of parts and, for example, appropriately setting the shape of each coupling window, it is possible to improve the uniformity of the discharge in the direction of the laser optical axis.

In the above embodiments, a rectangular waveguide or a circular waveguide is used as the microwave transmission line, but it goes without saying that other transmission lines such as a ridge waveguide may also be used.

〔Effect of the invention〕

As described above, according to the present invention, microwaves from a microwave oscillator are transmitted to a microwave circuit through a microwave transmission line, and the microwave is transmitted to a space in which at least one side of the microwave circuit is partitioned by a dielectric material. In a gas laser device that uses waves to generate plasma and excite the laser, the microwave transmission line and the microwave circuit are arranged in parallel along the laser optical axis, and the microwave electric field in the microwave transmission line is almost zero. By coupling microwaves into the dielectric from the side of the dielectric through a coupling window extending in the direction of the laser optical axis, which is provided on a wall surface, uniform discharge is achieved in the direction of the laser optical axis, resulting in a compact configuration. This has the effect of providing a gas laser device with high laser oscillation efficiency and large output.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a gas laser device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is a laser head according to another embodiment of the invention. cross section,
4 and 5 are cross-sectional views showing a laser head according to still another embodiment of the present invention, FIG. 6 is a perspective view showing still another embodiment of the present invention, and FIG. 7 is a conventional gas laser head. A perspective view showing the laser device, FIG. 8 {and FIG. 7 B-Bm
FIG. (1)... Magnetron, (2)... Urn waveguide, (4
1). (42). (43). (44),<45)●−φ
microwave coupling window, (6)...laser hesid,
(66). (682)...dielectric, (681
), (883)...Side surface of dielectric material, (67)...
・Number discharge space. Note that the same reference numerals in each figure indicate the same or equivalent parts. Deputy Masuo Iwa, Jindai University

Claims (1)

[Claims] Microwaves from a microwave oscillator are transmitted to a microwave circuit through a microwave transmission line, and a plasma is generated by the microwaves in a discharge space in which at least one side of the microwave circuit is partitioned by a dielectric material, and laser excitation is performed. In the gas laser device, the microwave transmission path and the microwave circuit are arranged in parallel along the laser optical axis, and the laser is provided on a wall surface where the microwave electric field in the microwave transmission path becomes almost zero. A gas laser device characterized in that the microwave is coupled into the dielectric from a side surface of the dielectric through a coupling window extending in the optical axis direction.