JPH07122806A - Microwave-excited gas laser device - Google Patents

Abstract

PURPOSE:To realize uniformity of electric field distribution in a wave guide which is generated by microwaves regarding a microwave-excited gas laser device of large output which carries out excitation of laser medium by gas discharge by the use of microwaves. CONSTITUTION:This microwave-excited gas laser device carries out laser oscillation by discharging and exciting laser medium gas in a discharge tube 14 provided inside a wave guide 12 by microwave introduced to the wave guide 12. In the device, a plurality of electrodes 18 are arranged on the periphery of a discharge tube and a plurality of electrodes 18 electrically float to at least an inside wall of the wave guide 12 regarding microwaves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser device, and more particularly to a high power microwave pumped gas laser device for pumping a laser medium by a gas discharge by microwaves.

[0002]

2. Description of the Related Art Generally, a discharge-excited gas laser device is required to generate a spatially uniform glow discharge in a laser medium gas.

This is because the non-uniformity of the discharge induces an arc discharge that is not suitable for excitation, causes partial abnormal heating of the gas, and causes spatial non-uniformity of the laser amplification factor. As a result, the laser oscillation efficiency and the maximum output are reduced as a whole.

Particularly, in the discharge excitation by microwaves, since the microwave wavelength is as short as ten and several centimeters, a uniform electric field strength distribution cannot be obtained in a wide range, and there is a problem that the discharge becomes spatially non-uniform. It is especially difficult to make the discharge spatially uniform.

As a measure against this, for example, Japanese Patent Laid-Open No. 2-130
According to the '975 publication, an insulator is inserted inside the microwave waveguide to improve the spatial uniformity of discharge.

[0006] However, this proposal is merely an improvement in that the range of the discharge region is limited by an insulator and a portion having relatively good electric field uniformity is used, and an essentially uniform electric field distribution is obtained. It's not a suggestion to create.

Further, as another example of measures, Japanese Patent Laid-Open No. 3-3
According to Japanese Patent Laid-Open No. 382, a raised portion (usually called a ridge, which is a structure that is electrically connected to the inner wall of the waveguide when viewed from the microwave) is formed by a conductor on the inner wall surface of the microwave waveguide. Methods have also been devised to improve the spatial uniformity of the discharge.

However, this method has a problem in that the region through which the microwave passes inside the waveguide is narrowed by the ridge, and the propagation of the microwave is hindered.

[0009]

That is, in the conventional configuration, since the microwave wavelength is short, the spatial electric field strength distribution is not uniform and the discharge is not uniform, and the overall efficiency and output of laser oscillation are improved. Had a problem of decreasing.

Further, the uniformization of the electric field by the ridge has a problem of hindering the propagation of microwaves.

The present invention solves the above-mentioned problems of the prior art, does not hinder the propagation of microwaves in the waveguide, makes the electric field strength distribution in the discharge region uniform, and increases the efficiency and output of laser oscillation. An object is to provide a microwave excitation gas laser device.

[0012]

In order to achieve this object, in a microwave excited gas laser device of the present invention, a plurality of electrodes are arranged around a discharge tube provided in a waveguide and introduced into the waveguide. The electrodes have a configuration in which they are electrically floating with respect to the inner wall of the waveguide when viewed from the microwave.

[0013]

With the above structure, the electric field distribution inside the discharge tube is made uniform by optimizing the shape and arrangement of the plurality of electrodes around the discharge tube, and the electrodes are positioned relative to the inner wall of the waveguide when viewed from the microwave. Since it is electrically floating, it hardly interferes with microwave propagation.

In general, an obstacle whose potential is not fixed (electrically floating) is an obstacle whose electric potential is electrically fixed to the inner wall of the waveguide (ridge has a fixed potential). Is less likely to interfere with microwave propagation.

[0015]

(Embodiment 1) A first embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing a first embodiment of the present invention. In FIG. 1, 11 is a magnetron, 12 is a waveguide, 13 is a stub tuner, 14 is a discharge tube, 15 is a total reflection mirror, 16 is an output mirror, 17 is a laser beam, 18 is an electrode, 19 is a plunger, 20 is I am a fan.

FIG. 2 is a cross-sectional view showing the AA 'cross section of FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, but 21 is an insulator and 22 is a gas cooler.

FIG. 3 is a sectional view showing a BB 'section in FIG. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same numbers, but 31 is a magnetron output electrode, 32 is a magnetron side plunger, and 33 is a standing wave.

Here, the four electrodes 18a to 18d are
These electrodes 1 are arranged inside the waveguide 12 and around the discharge tube 14, and are physically held by an insulator 21 having a small loss with respect to microwaves as shown in FIG.
8a to 18d have a state in which the electric potential is not fixed with respect to the inner wall of the waveguide 12 when viewed from the microwave, and is electrically floating.

In the microwave-excited gas laser device configured as described above, CO ₂ which requires particularly high output
The operation will be described below assuming a laser device, but it can be applied to other types of gas lasers because it can function as other types of gas lasers by changing the laser medium gas.

That is, a rare gas laser, a metal vapor laser,
It can also be applied to configurations such as a He-Ne laser and an ion laser.

The microwave (2.45 GHz) generated from the magnetron 11 propagates through the waveguide 12, is matched by the stub tuner 13, and the laser medium gas (CO ₂ , A mixed gas of Ne and He excites discharge at a ratio of 1: 2: 20 at a pressure of about 30 Torr), and laser light 17 is output from an optical resonator including a total reflection mirror 15 and an output mirror 16.

At this time, the gas cooled by the fan 20 and the gas cooler 22 circulates in the discharge tube 14.

Regarding microwaves, as shown in FIG. 3, the plungers 19 and 32 are adjusted so that the portion of the discharge tube 14 becomes a sinusoidal standing wave 33 located at the antinode position.

Further, the stub tuner 13 is adjusted so that the output of the magnetron 11 can be optimally matched with the load of the discharge tube 14.

Next, FIG. 4 (a) is an enlarged view of the vicinity of the discharge tube 14 of FIG. 3, and FIGS. 4 (b) to 4 (c) are views showing the polarization states of the electrodes 18a to 18d. Is.

In FIGS. 4 (a) to 4 (d), 41
Is a central portion inside the discharge tube 14, 42 is a side portion thereof, and 43a
Is the position between the electrodes 18a and 18b, and 43b is the electrode 18
The position between the electrodes of c and 18d, 44 is the direction of the electric field, and 45 is the space between the electrode 18 and the inner wall of the waveguide 12.

Now, the microwave 33 inside the discharge tube 14
Considering that the electric field of the microwave 33 is equal to the vibration direction of the electric field, the electric field of the microwave 33 is examined. Even when vibrating upward, the discharge tube 14
The central portion 41 is strong and the side portions 42 are weak.

For this reason, the central portion 41 is strongly discharged, resulting in nonuniform discharge. On the other hand, the electrodes 18a to 18d are
As shown in FIG. 4B and FIG. 4C, the microwaves 33 are vertically polarized at a frequency corresponding to the vibration direction of the electric field.

Due to this effect, the electric field is strengthened at the positions 43a and 43b between the electrodes, and the side portion 42 near 43a and 43b.
The electric field of is also increased.

As a result, since the weak electric field of the side portion 42 when the electrode 18 is not provided is reinforced, it can be made substantially equal to the electric field of the central portion 41, and the electric field in the discharge tube 14 can be improved. Discharge intensity becomes uniform.

The control of such electric field distribution is performed by the electrode 18a.
Can be changed by changing the width W from 18 to 18d, the position of the electrode, the inclination, etc. Specifically, since it changes depending on the dimensions of the discharge tube 14, the waveguide 12, etc. It is realistic to experimentally determine the position and shape of the electrode 18 at which the discharge is uniform and the discharge is uniform.

However, when the uniformity of the electric field is required, the electrodes 18a to 18d are symmetrically arranged with respect to the discharge tube 14 to enhance the symmetry of the electric field distribution inside the discharge tube 14. It is suitable.

Further, in this embodiment, as shown in FIG. 2, the electrodes 18a to 18d do not change their shapes in the lengthwise direction of the discharge tube 14, but the electric field distribution in the lengthwise direction is also the electrode 18.
It is also possible to make the electric field distribution in that direction uniform and control it by changing the shape of (1) in the length direction (for example, the change of the width W or the twist of the electrode).

Since the electrodes 18a to 18d are held in an electrically floating state as described above, they are unlikely to hinder the propagation of microwaves. However, between the electrodes 18a to 18d and the inner wall of the waveguide 12, it is more difficult. Since the spaces 45a and 45b are secured, microwaves can easily pass therethrough, and obstacles are further reduced.

Since the insulator has little influence on the propagation of microwaves, the spaces 45a and 45b have
An insulating holding member may be provided to hold the electrodes 18a to 18d.

(Embodiment 2) A second embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 5 is a sectional view corresponding to FIG. 2 of the first embodiment of the present invention. In FIG. 5, the same parts as those in FIG. 2 are denoted by the same reference numerals, but 51 is a connecting part of the electrode 18, and 52 is a standing wave of microwave.

In the first embodiment, as shown in FIG. 2, the electrode 18 is mechanically held by the insulator 21,
More specifically, as shown in FIG. 5, the microwaves are standing waves 52 also in the length direction of the discharge tube 14.

Therefore, the electric field is weak at both ends of the electrode 18, and even if these both ends are directly connected to the inner wall of the waveguide 12, the electric potential of the electrode 18 is not fixed when viewed from the microwave. It will be possible to maintain a floating state.

Therefore, in this embodiment, the end which is a part of the electrode 18 is directly connected to the inner wall of the waveguide 12 to mechanically hold the electrode 18 to realize a simpler structure. .

(Third Embodiment) A third embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 6A shows the second embodiment of FIG.
6 is a cross-sectional view corresponding to FIG. 5 in the embodiment of FIG. 6, and a partially enlarged perspective view thereof is FIG. 6 (b).

FIG. 6 shows a sectional view of a modified embodiment of the portion corresponding to FIG. However, the lower part of FIG. 6 is a partially enlarged perspective view.

In FIGS. 6A and 6B, the same parts as those in FIGS. 2 and 5 are designated by the same reference numerals, and 61 is a connecting part.

As in FIG. 5, the electric field is weak at the end portions of the electrodes 18, and even if the electrodes 18 are connected to each other by the metal connecting member 61 in this portion, the potential of the electrodes 18 is fixed as seen from the microwave. Instead, the electrically floating state can be maintained.

Therefore, the electrodes 18 are connected to each other by the connecting member 61 and are further connected to the discharge tube 14 to hold the electrodes 18 mechanically.

In this case, the four electrodes 18 are integral with each other in terms of direct current and electrical power, but each of them operates independently with the microwave of alternating current.

This structure realizes a simple structure in which the electrode 18 can be integrated with the discharge tube 14. (Embodiment 4) A fourth embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 7 is a perspective view showing a fourth embodiment of the present invention. In FIG. 7, 11 is a magnetron, 12 is a waveguide, 13 is a stub tuner, 14 is a discharge tube, 15 is a total reflection mirror, 16 is an output mirror, 17 is a laser beam, 19 is a plunger, 20 is a fan, 71 is 71 It is an electrode.

FIG. 8 is a sectional view showing a section taken along the line AA 'of FIG. 8, the same parts as those in FIG. 7 are denoted by the same reference numerals, and 81 is an insulator.

FIG. 9 is a sectional view showing a section taken along the line BB ′ of FIG. 7, which is a sectional view in the vicinity of the discharge tube 14.

In FIG. 9, the same parts as those in FIG. 7 are denoted by the same reference numerals, 33 is a standing wave, 41 is a central part inside the discharge tube 14, 42 is a side part of the discharge tube 14, and 91a and 91b are electrodes. 7
The positions between the electrodes at the ends of 1a and 71b are shown.

The operation of the microwave excitation gas laser device of the present embodiment constructed as above is the same as that of the above-mentioned embodiment.

The present embodiment is different from the first embodiment in the structure of the electrodes. In contrast to the four electrodes 18 in the first embodiment, two electrodes 71a and 71b are used. That is the point.

As shown in FIG. 9, the electrodes 71a and 71b are curved so as to face each other, and each end is
As shown in FIG. 8, it is mechanically held by the insulator 81.

By constructing the electrode 71 in this way, the central portion 41 inside the discharge tube 14 is located at the side portion 4 because of the microwave 33.
The electric field distribution in a state where the electric field is stronger than 2 can be made uniform, and the electric fields in the central portion 41 and the side portions 42 can be made substantially equal.

Specifically, since the electric field is directed in the vertical direction in FIG. 9, the curved electrodes 71a and 71b are
The electrode ends are polarized with respect to the electrode center.

Therefore, the inter-electrode end positions 91a and 91b are formed.
The electric field is strengthened. Due to this effect, the weak electric field of the side portion 42 inside the discharge tube 14 is reinforced, the difference from the central portion 41 is eliminated, and the uniformity of the electric field and the uniformity of the discharge are realized.

The electric field distribution is changed by changing the width of the electrode 71, the position of the electrode, the curvature, etc.
Since it also changes depending on the dimensions of the waveguide 12 and the like, it is realistic to experimentally determine the position and shape of the electrode 71 where the electric field distribution is most uniform and the discharge is uniform.

In this case, the electrodes 71a and 71b are arranged symmetrically with respect to the discharge tube 14 so that
The symmetry of the electric field distribution inside is increased, and the uniformity of the electric field is further improved.

Further, in the present embodiment, as shown in FIG. 8, the shape of the electrode 71 does not change in the length direction of the discharge tube 14, but the shape of the electrode 71 changes in the length direction ( For example, the electric field distribution in the length direction can be made uniform and controlled by changing the width and position, changing the curvature of the electrode, and the like.

Since the electrode 71 is electrically floating, it is less likely to obstruct the propagation of microwaves, but since there is a space 92 between the electrode 71 and the inner wall of the waveguide 12, microwaves can pass therethrough. It is easy and has few obstacles.

Further, even if an insulator is present in the spaces 92a and 92b, it does not substantially affect the propagation of microwaves, so that an insulator can be inserted to hold the electrodes 92a and 92b. is there.

Similarly, the electric field is weak at the end of the electrode 71 in the length direction of the discharge tube 14, and instead of being held by the insulator 81 as shown in FIG. Electrode 7
Similar to the previous example, the one end may be connected.

Similarly, it is possible to adopt a structure in which the ends of the two electrodes 71 are connected to each other by a metal connecting member and are connected to and held by the discharge tube 14.

It should be noted that the electrodes 18 and the like in all of the above embodiments can be made of a conductor or a dielectric. When the electrodes are made of a dielectric material, it is possible to have a simple structure that also serves as a holding member for the electrodes.

[0068]

As described above, according to the present invention, a plurality of electrodes are arranged around the discharge tube, and the electrodes are electrically floating with respect to the inner wall of the waveguide when viewed from the microwave. It is possible to realize an excellent microwave-excited gas laser device which hardly interferes with the propagation of microwaves in a tube and also makes the electric field intensity distribution in the discharge region uniform, thereby enhancing the efficiency and output of laser oscillation.

[Brief description of drawings]

FIG. 1 is a perspective view of a configuration according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the A-A ′ cross section of FIG.

FIG. 3 is a cross-sectional view showing a B-B ′ cross section of FIG. 1.

FIG. 4 is an enlarged view of the vicinity of the discharge tube 14 in FIG.

FIG. 5 is a sectional view of the configuration of the second embodiment of the present invention.

FIG. 6 is a cross-sectional view of the configuration according to the third embodiment of the present invention.

FIG. 7 is a perspective view of a configuration according to a fourth embodiment of the present invention.

8 is a cross-sectional view showing a cross section taken along the line A-A ′ of FIG. 7.

9 is a cross-sectional view of the discharge tube 14 and its vicinity in a B-B ′ cross section of FIG. 7.

[Explanation of symbols]

 11 Magnetron 12 Waveguide 13 Stub Tuner 14 Discharge Tube 17 Laser Light 18 Electrode 21 Insulator 33 Standing Wave 51 Connection Part 52 Standing Wave 61 Connection Part 71 Electrode 81 Insulator

Claims (10)

[Claims] 1. A microwave-excited gas laser device for laser-oscillating by exciting a laser medium gas in a discharge tube provided in a waveguide with a microwave introduced into the waveguide to perform laser oscillation. A microwave-excited gas laser device having electric field control means for making the distribution of an electric field generated by waves uniform. 2. A microwave-excited gas laser device for performing laser oscillation by exciting a laser medium gas in a discharge tube provided in a waveguide by a microwave introduced into the waveguide to perform laser oscillation. A microwave excited gas laser device for realizing a final electric field distribution by superimposing a second electric field distribution generated by an electric field generating means on a first electric field distribution generated by a wave. 3. A microwave-excited gas laser device for exciting a laser medium gas in a discharge tube provided in a waveguide by a microwave introduced into the waveguide to oscillate the laser, the discharge comprising: A microwave-excited gas laser device in which a polarization means that polarizes corresponding to the frequency of the microwave is arranged around the tube. 4. A microwave-excited gas laser device for performing laser oscillation by exciting a laser medium gas in a discharge tube provided in a waveguide by microwaves introduced into the waveguide, the discharge comprising: A microwave-excited gas laser device in which a plurality of electrodes are arranged around a tube, and the plurality of electrodes are electrically suspended with respect to the microwave with respect to at least an inner wall of the waveguide. 5. The microwave excited gas laser device according to claim 4, wherein a plurality of electrodes are arranged symmetrically around the discharge tube. 6. The electrode according to claim 4, wherein the plurality of electrodes are electrically floated with respect to microwaves, and therefore the plurality of electrodes are held by holding means formed of an insulating material having a small loss with respect to microwaves. Microwave excited gas laser device described. 7. The method according to claim 4, wherein the plurality of electrodes are directly connected to at least the inner wall of the waveguide at a portion of the electrodes that does not prevent electrically floating from microwaves. The microwave excited gas laser device according to any one of claims 1. 8. A plurality of electrodes are connected by a holding means to a discharge tube while coupling the electrodes to each other at portions of the electrodes that do not prevent electrically floating with respect to microwaves. The microwave excited gas laser device according to claim 4, 9. The microwave excited gas laser device according to claim 4, wherein the plurality of electrodes are formed of a dielectric material and are integrated with the holding means. 10. The microwave excited gas laser device according to claim 1, wherein the laser medium gas contains CO ₂ gas.