JPH07105538B2 - Gas laser device - Google Patents

Description

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

[Prior Art] FIG. 13 is a perspective view showing a conventional gas laser device (Japanese Patent Application No. 62-225224) filed by the applicant of the present application on September 10, 1987,
FIG. 14 is a sectional view taken along line XIV-XIV in FIG. 13, and FIG. 15 is X in FIG.
It is a V-XV line sectional view.

In the figure, 2 is a laser head part having a ridge waveguide type microwave cavity structure, which is a kind of microwave circuit for generating plasma in laser gas by microwave discharge and performing laser excitation. A magnetron as a microwave oscillator, 4 is a waveguide for guiding the microwave output from the magnetron 3 to the laser head portion 2, 6 is a microwave coupling window for coupling the waveguide 4 to the laser head portion 2, and 5 is A laser oscillation total reflection mirror attached to the laser head portion 2 and a laser oscillation partial reflection mirror 7 attached to the laser head portion 2. Further, 20 is a cavity wall following the microwave coupling window 6 in the laser head portion 2, and 21 and 22 are provided in the central portion of the cavity wall 20, each constituting a part of a microwave circuit. Ridge, 23
Is a conductor wall formed on one ridge 21. In this conventional example, the bottom wall surface of the groove 28 provided on the upper surface of the ridge 21 is used. The reference numeral 24 designates a dielectric made of, for example, alumina, which is provided so as to face the conductor wall 23 and acts as a microwave entrance window.
By covering the groove 28 on the upper surface, it is a discharge space which is formed between the conductor wall 23 and the dielectric 24 and in which a laser gas such as a carbon dioxide laser gas is sealed.

Next, the operation will be described. The microwave generated by the magnetron 3 propagates through the waveguide 4 and the microwave coupling window 6
By matching the impedance with, the laser head 2 is efficiently coupled. The laser head portion 2 has a ridge cavity shape as shown in the drawing, and microwaves are concentrated near the ridges 21 and 22 to generate a very strong microwave electromagnetic field. Due to this strong microwave electromagnetic field, the laser gas enclosed in the discharge space 25 is destroyed by discharge, plasma is generated, and the laser medium is excited. Here, cooling water is flown through the cooling water passage 27 to cool the discharge plasma, and the laser oscillation conditions are obtained by appropriately selecting the discharge conditions such as the pressure of the laser gas, and the partial reflection mirror shown in FIG. Laser oscillation light is obtained by forming a laser resonator with 7 and the total reflection mirror 5 facing it.

At this time, the ridge 21 forming part of the microwave circuit
Microwave discharge is performed in the discharge space formed between the conductor wall 23 formed in and the dielectric wall 24, which is arranged so as to face the conductor wall 23 and serves as a microwave entrance window.
Since the microwave is incident only from one side of the plasma, the phenomenon that the microwave mode of the coaxial mode with the plasma as the inner conductor becomes dominant does not occur, and the desired microwave is not generated. Discharge in the wave mode can be performed. When the microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric 24 and the plasma, like the ridge cavity of the laser head portion 2 shown in the figure, the dielectric 24 and the conductor are Since it faces the wall 23, it also has an electric field component perpendicular to the conductor wall 23, and an electric field penetrating the plasma can be formed. Therefore, even if a plasma having conductivity is generated, the conductive material wall 23 having a conductivity several orders of magnitude higher than that of the plasma is arranged so as to face the dielectric 24 as the microwave incident window, so that the incident microwave The termination current flows through the conductor wall 23, and the electric field in the vicinity of the conductor wall 23 is forced to be perpendicular to the surface of the conductor wall 23, so that the electric field penetrating the generated plasma is maintained. Therefore, the microwave penetrates into the plasma and a current flows through the plasma, and a spatially uniform discharge plasma is generated due to the continuity of the current. In this way, since a spatially uniform discharge can be obtained, it becomes easy to put the entire discharge in a state suitable for laser excitation. Further, the laser head portion 2 which is a microwave circuit and the waveguide 4 which is a microwave transmission path are arranged in parallel in the direction along the laser optical axis, and a long micro-wave provided in the longitudinal direction of the laser head portion 2. Microwaves can be supplied through the wave coupling window 6 to uniformly generate a strong microwave electromagnetic field over the ridges 21 and 22 of the laser head portion 2. Therefore, it is possible to obtain a long and uniform discharge in the laser optical axis direction without increasing the size of the entire device, and it is possible to put the entire discharge in an optimum state for laser excitation.

[Problems to be Solved by the Invention] In the conventional gas laser device as described above, the laser head portion 2 which is a microwave circuit and the waveguide 4 which is a microwave transmission path are arranged in parallel in the direction along the laser optical axis. Microwaves are supplied through the long microwave coupling window 6 arranged in the longitudinal direction of the laser head portion 2 to uniformly generate a strong microwave electromagnetic field over the ridges 21 and 22 of the laser head portion 2. However, the microwave coupling window 6 is provided at a position facing the dielectric 24, though it is long in the laser optical axis direction and enables uniform discharge to generate more stable and uniform plasma in the discharge space. Therefore, the coupling strength of microwaves from the microwave coupling window 6 to the dielectric 24 is strong, and therefore, when discharge is started in a part of the discharge space 25, the energy of microwaves flows into that part. The more, the energy flow into the other part is reduced.

Therefore, there is a problem in that the discharge distribution in the longitudinal direction becomes non-uniform and plasma may not be generated uniformly in the discharge space 25.

Further, since the microwave coupling window 6 is provided parallel to the axis of the waveguide 4, the degree of coupling of microwave energy from the waveguide 4 to the laser head portion 2 is constant over the length direction, The microwave energy is supplied from the side of the magnetron 3 which is a microwave generator, and is gradually coupled to and absorbed by the laser head portion 2. Therefore, the microwave energy in the conductive tube 4 is magnetron 3 which is a microwave source.
It becomes smaller as it gets further away. Therefore, the energy coupled to the laser head unit 2 is reduced, and the 15th
As shown in the figure, the length of each node of the discharge gradually shortens as the distance from the magnetron 3 increases, and from this point also the discharge space
In 25, there was a problem that plasma might not be generated uniformly.

The present invention has been made in order to solve the above-mentioned problems, and a microwave discharge plasma that is generated is stable and spatially uniform, and a gas that enables laser operation with high efficiency and high output. The purpose is to obtain a laser device.

[Means for Solving the Problems] In a gas laser device according to the present invention, a microwave transmission line and a microwave circuit are installed in parallel along a laser optical axis, and the microwave transmission line and the microwave circuit are coupled with each other. And the coupling slit is displaced from the position facing the dielectric. Further, the coupling strength of the coupling slit is gradually weakened as it approaches the microwave oscillator. Further, in order to weaken the coupling strength of the coupling slit as it gets closer to the microwave oscillator, the width of the coupling slit is made smaller as it gets closer to the microwave oscillator, or the position where the coupling slit faces the dielectric as it gets closer to the microwave oscillator. You may incline and it may be provided with respect to the axis | shaft of a microwave transmission path so that it may be distanced from it. Furthermore, the thickness of the slit wall constituting the coupling slit is configured to increase as it approaches the microwave oscillator.

[Operation] In the gas laser device according to the present invention, the microwave transmission line and the microwave circuit are installed in parallel along the laser optical axis,
Since the microwave transmission line and the microwave circuit are coupled through the coupling slit provided at a position offset from the position facing the dielectric, the microwave passing through the coupling slit does not directly reach the dielectric and is coupled. Microwave coupling from the slit to the dielectric is weakened, the phenomenon that microwave energy flows into only a part of the discharge space is weakened, and the discharge distribution due to microwave energy becomes uniform over the entire length in the discharge space. .

Further, in the gas laser device according to another invention, a microwave transmission line and a microwave transmission line are installed in parallel along the laser optical axis, and the microwave transmission line and the microwave circuit are coupled via a coupling slit. , The coupling strength of each part in the longitudinal direction of the coupling slit, the width of the coupling slit is changed, the coupling slit is inclined with respect to the axis of the microwave transmission line, or the thickness of the slit wall constituting the coupling slit is changed. Since the microwave energy becomes weaker as it gets closer to the microwave oscillator, on the microwave generation source side where the microwave energy in the microwave transmission line is strong, the coupling strength of the coupling slit is weak and the microwave energy is weakened and the microwave circuit Is introduced into the microwave transmission line and the microwave energy in the microwave transmission line is far from the microwave source, Strongly bond strength bets is the degree to which microwave energy is weakened is introduced into the microwave circuit becomes small. Therefore, the microwave energy introduced into the laser head portion, which is a microwave circuit, becomes uniform, and the discharge distribution by the microwave energy becomes uniform over the entire longitudinal direction in the discharge space.

[Embodiment] 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 II-II in FIG. 1, and FIG. 3 is a line III-III in FIG. FIG. In the figure, the same configurations as those of the conventional example are denoted by the same reference numerals as those of the conventional example, and the description of the duplicated configurations is omitted.

Reference numeral 60 is a slit wall having a coupling slit 61 for coupling the waveguide 5 to the laser head portion 2. The coupling slit 61 is provided so as to be displaced from the position facing the dielectric 24.

In the gas laser device configured as described above, the waveguide 4 that is a microwave transmission line and the laser head portion 2 that is a microwave circuit are arranged in parallel in the direction along the laser optical axis, and the waveguide 4 Since the laser head section 2 and the laser head section 2 are coupled to each other through a coupling slit 61 provided so as to be displaced from the position facing the dielectric body 24, the microwave from the magnetron 3 which is a microwave oscillator passes through the waveguide 4 and the laser. Microwaves that have passed through the coupling slit 61 when being transmitted to the head unit 2 do not directly reach the dielectric 24, and the coupling slit 61
Microwave coupling from 61 to dielectric 24 is weakened. Therefore, the phenomenon that the microwave energy largely flows into only a part of the discharge space 25 is weakened, and as shown in FIG. 3, the discharge distribution due to the microwave energy becomes uniform over the entire longitudinal direction in the discharge space. The nodes become uniform in length, stable and uniform plasma is generated in the discharge space, and the laser output can be obtained with high efficiency and high output laser.

4 is a perspective view showing another embodiment of the present invention, FIG. 5 is a sectional view taken along line VV of FIG. 4, and FIG. 6 is a sectional view taken along line VI-VI of FIG. In this embodiment, the structure of the coupling slit 611 is different from that of the above embodiment. That is, the coupling slit of this embodiment
611 is formed so that its width becomes gradually smaller as it approaches the magnetron 3.

Therefore, the coupling strength of the coupling slit 611 is equal to that of the magnetron 3.
Is getting weaker as it gets closer to. Therefore, the coupling strength of the coupling slit 611 is weak at the position on the magnetron 3 side where the microwave energy in the waveguide 4 is strong, and the microwave energy is weakened by the coupling slit 611 and introduced into the laser head portion 2, while the microwave energy is guided. At a position farther from the magnetron 3 side where the microwave energy in the wave tube 4 becomes weaker, the coupling strength of the coupling slit 611 is strong, and the microwave energy is weakened to a lesser degree than the magnetron 3 side and introduced into the laser head portion 2. To be done.
Therefore, the microwave energy introduced into each part of the laser head portion 2 extending in the longitudinal direction becomes uniform, the discharge distribution by the microwave energy becomes uniform over the entire longitudinal direction in the discharge space, and the discharge space becomes stable, and A uniform plasma is generated.

FIG. 7 is a perspective view showing still another embodiment of the present invention, FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 7, and FIG. 9 is I of FIG.
It is an X-IX line sectional view. Also in this embodiment, the coupling strength of the coupling slit 612 is similar to that of the embodiment shown in FIG.
It is formed so that it gradually weakens as it approaches, and its configuration is different from that of FIG. That is, the coupling slit 612 of this embodiment is formed so as to be inclined with respect to the axis of the waveguide 4 so as to gradually move away from the position facing the dielectric 24 as it approaches the magnetron 3. Therefore, the coupling strength is weak at the position of the coupling slit 612 on the magnetron 3 side because it is far from the dielectric 24, and the coupling strength is weak at the position of the coupling slit 612 farther from the magnetron 3 side because it is closer to the dielectric 24. strong. Therefore,
The microwave energy introduced into each part of the laser head portion 2 extending in the longitudinal direction is uniform as in the embodiment shown in FIG.

FIG. 10 is a perspective view showing still another embodiment of the present invention, FIG. 11 is a sectional view taken along line XI-XI of FIG. 10, and FIG. 12 is a sectional view taken along line XII-XII of FIG. . Similar to the embodiment shown in FIG. 6, this embodiment is also formed so that the coupling strength of the coupling slit 613 becomes gradually weaker as it approaches the magnetron 3, and its configuration is different from that of FIG. That is,
In this embodiment, the slit wall 6 forming the coupling slit 613
The thickness of 01 gradually increases as it approaches the magnetron 3. Further, the coupling slit 613 is provided at a position facing the dielectric 24. In this way, the coupling strength of the coupling slit 613 differs depending on the difference in the thickness of the slit wall 601 because microwaves are transmitted through the slit wall 601 as well, and when the slit wall 601 becomes thicker, the microwave energy passing through it is attenuated. This is because it is considered that the amount increases and the coupling strength of the coupling slit 613 weakens accordingly.

Therefore, on the magnetron 3 side of the coupling slit 613, the slit wall 601 is thickened to weaken the coupling strength, and the coupling slit 6
At a position away from the magnetron 3 side of 13, the slit wall 603 is thinned to increase the coupling strength and uniformize the microwave energy introduced into each part of the laser head portion 2 extending in the longitudinal direction.

In all of the embodiments shown in FIGS. 4 to 10, the coupling strength of the coupling slits 611 to 613 is continuously changed in the longitudinal direction, but it may be changed stepwise. Of course. Further, it goes without saying that the structure of the coupling slit 61 may be any combination of the embodiments shown in FIGS. 4 to 10.

In the above embodiment, the conductor wall 23 is described as being in contact with plasma.However, even if a dielectric layer that is thinner than the wavelength of microwaves, such as a dielectric coating layer, is provided on the surface of the conductor, this dielectric layer is It goes without saying that the above effect is not impaired because it works only as a low impedance against microwaves and does not significantly affect the electric field distribution of microwaves.

EFFECTS OF THE INVENTION As described above, according to the present invention, the microwave transmission line and the microwave circuit are installed in parallel along the laser optical axis, and the microwave transmission line and the microwave circuit are disposed from the position facing the dielectric. Since the microwaves that have been coupled through the coupling slits that are staggered do not reach the dielectric directly through the coupling slits, the coupling of the microwaves from the coupling slits to the dielectric is weakened. The phenomenon that a large amount of gas flows into only a part of the discharge space is weakened, the discharge distribution by the microwave energy becomes uniform over the entire longitudinal direction in the discharge space, and stable and uniform plasma is generated in the discharge space to increase the laser output. It has an effect that it can be obtained with high efficiency and high output.

Further, another invention is that a microwave transmission line and a microwave circuit are installed in parallel along a laser optical axis, and the microwave transmission line and the microwave circuit are coupled via a coupling slit, and the longitudinal direction of the coupling slit. Microwave generator by changing the width of the coupling slit, inclining the coupling slit with respect to the axis of the microwave transmission path, or changing the thickness of the slit wall constituting the coupling slit. Since it becomes weaker as it approaches, the coupling strength of the coupling slit is weak at the position on the microwave generation source side where the microwave energy in the microwave transmission line is strong, and the microwave energy is weakened and introduced into the microwave circuit. , The microwave energy in the microwave transmission line is weak, and the coupling strength of the coupling slit is strong at the position far from the microwave source side. , The microwave energy is weakened to a lesser extent and is introduced into the microwave circuit, and the microwave energy introduced into the microwave circuit is uniform in the longitudinal direction, so that the microwave energy is distributed over the entire longitudinal direction in the discharge space. The discharge distribution due to energy becomes uniform, and stable and uniform plasma is generated in the discharge space, so that the laser output can be obtained with high efficiency and large output.

[Brief description of drawings]

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 line II-II of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG. 4 is a perspective view showing another embodiment of the present invention, FIG. 5 is a sectional view taken along line VV of FIG. 4,
6 is a sectional view taken along line VI-VI in FIG. 4, FIG. 7 is a perspective view showing still another embodiment of the present invention, and FIG. 8 is VIII in FIG.
-VIII line sectional view, FIG. 9 is the IX-IX line sectional view of FIG. 7, 10
The drawing is a perspective view showing still another embodiment of the present invention,
11 is a sectional view taken along line XI-XI in FIG. 10, and FIG. 12 is XII-X in FIG.
II sectional view, FIG. 13 is a perspective view showing a conventional gas laser device, FIG. 14 is a sectional view taken along line XIV-XIV of FIG. 13, and FIG.
It is the XV-XV sectional view taken on the line of FIG. 2 ... Laser head (microwave circuit), 3 ... Magnetron (microwave oscillator), 4 ... Waveguide (microwave transmission line), 60 ... Slit wall, 61 ... Coupling slit. In the figure, the same reference numeral 2 indicates the same or a corresponding portion.

Claims (5)

[Claims] 1. A microwave oscillator that oscillates microwaves, a microwave transmission line that transmits microwaves, and a plasma generated in a laser gas by the discharge of the microwaves transmitted by the microwave transmission line to excite the laser. A microwave circuit for performing the microwave circuit, and the laser gas is sealed in a discharge space provided in the microwave circuit and having a dielectric that serves as a microwave entrance window on one surface, and the dielectric circuit and the laser are provided by the microwave circuit. In a microwave excitation type gas laser device configured to form a microwave mode having an electric field component perpendicular to a boundary with plasma generated in a gas, a microwave transmission line and a microwave circuit are arranged along a laser optical axis. Installed in parallel, the microwave transmission line and the microwave circuit are coupled via a coupling slit, and the coupling slit faces the dielectric. A gas laser device, which is provided so as to be displaced from a position. 2. A microwave oscillator that oscillates microwaves, a microwave transmission line that transmits microwaves, and a microwave that is transmitted through the microwave transmission line to generate plasma in the laser gas for laser excitation. And a microwave circuit for performing the microwave circuit, and enclosing the laser gas in a discharge space formed between the microwave circuit and a dielectric that serves as a microwave entrance window. In a microwave-excitation type gas laser device for forming a microwave mode having an electric field component perpendicular to the boundary between the body and plasma generated in the laser gas, a microwave transmission line and a microwave circuit are used for laser light Installed in parallel along the axis, connect the microwave transmission line and the microwave circuit through the coupling slit, and connect them in the longitudinal direction of the coupling slit. A gas laser device, wherein the coupling strength of each part in the gas laser device is weakened as it approaches the microwave oscillator. 3. The gas laser device according to claim 1, wherein the coupling slit is formed so that its width becomes smaller as it gets closer to the microwave oscillator. 4. The coupling slit is provided so as to be inclined with respect to the axis of the microwave transmission line so as to move away from the position facing the dielectric as it approaches the microwave oscillator. 2. The gas laser device according to 2. 5. The gas laser device according to claim 1 or 2, wherein the slit wall forming the coupling slit is formed so that the thickness thereof becomes thicker as it approaches the microwave oscillator.