JP2002111100A - Gas laser oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gas laser oscillator in which the design margin of a discharge electrode is widened and the product is stabilized. SOLUTION: The gas laser oscillator comprises a gas laser housing for encapsulating laser gas, means for circulating the encapsulated laser gas in the gas laser housing, a pair of electrodes for discharging the gas by applying a voltage to the laser gas at a specified position of the circulating laser gas, and a discharge power supply connected with the pair of discharge electrodes and feeding the discharge electrodes with a voltage for discharging the laser gas, wherein the wall material constituting the housing is composed of a dielectric material at at least a part corresponding to a specified position and the pair of discharge electrodes are buried in the wall material composed of the dielectric material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a discharge electrode of a gas laser oscillator.

[0002]

2. Description of the Related Art FIG.
1 shows a configuration of a conventional gas laser oscillator disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-15095. In the figure, reference numeral 1 denotes an upper metal electrode, and 2 denotes a lower metal electrode, which are opposed to each other with a laser gas flow G therebetween. Reference numeral 3 denotes an upper first dielectric, and 4 denotes a lower first dielectric, which shields the upper metal electrode 1 and the lower metal electrode 2 from the laser gas flow G. Reference numeral 5 denotes an upper second dielectric, and reference numeral 6 denotes a lower second dielectric, which is filled between the left and right end surfaces of the upper and lower metal electrodes 1 and 2 and the upper and lower first dielectrics 3 and 4.
Reference numeral 7 denotes an upper cooling water passage provided in the upper metal electrode 1, and reference numeral 8 denotes a lower cooling water passage provided in the lower metal electrode 2. Next, the operation will be described. When a laser gas flow G is generated and a voltage is applied to the upper and lower metal electrodes 1 and 2 from a high-frequency power supply (not shown), a discharge occurs between the upper first dielectric 3 and the lower first dielectric 4. This discharge excites the laser gas molecules and causes optical amplification between several resonator mirrors (not shown) to cause laser oscillation. The discharge electrodes of the conventional gas laser oscillator cover the upper and lower metal electrodes 1 and 2 by covering the surfaces of the upper and lower metal electrodes 1 and 2 with upper and lower dielectrics 3 and 4 having a dielectric constant of about 2 to 200. High-frequency discharge is generated while preventing wear of the upper and lower metal electrodes 1, 2 and the upper and lower first dielectrics 3, 4.
The upper and lower second dielectrics 5 and 6 having a dielectric constant of about 2 to 20 are filled in the gap between the upper and lower metal electrodes 1 and 2 to reduce the concentration of the electric field and to obtain a uniform discharge. ing.

[0003]

In a discharge electrode of a conventional gas laser oscillator, an upper and lower second dielectric 5 is provided between upper and lower first dielectrics 3 and 4 and upper and lower metal electrodes 1 and 2. , 6 were filled. In such a configuration, the surface properties of the upper and lower first dielectrics 3, 4 and the upper and lower metal electrodes 1, 2 and the upper and lower second dielectrics 5, 6 are different from each other, and the difference in their thermal expansion coefficients is different. As a result, the residual stress increases, so that their adhesion is likely to be incomplete, and voids are generated at the interface and the like. In some cases, the electric field is concentrated in the portion where the void is generated, causing a problem such as partial discharge. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In a discharge electrode of a gas laser oscillator, the life of a metal electrode is extended, and partial discharge due to generation of voids and the like hardly occurs. It is an object of the present invention to realize a highly reliable gas laser oscillator capable of obtaining a stable discharge therein and a stable laser output.

[0004]

SUMMARY OF THE INVENTION A gas laser oscillator according to the present invention comprises a gas laser casing for enclosing a laser gas therein, a gas circulating means for circulating the enclosed laser gas inside the gas laser casing, and a circulating laser gas. A pair of discharge electrodes for applying a voltage to the laser gas at a predetermined position to cause gas discharge, and a discharge power supply connected to the pair of discharge electrodes and supplying a voltage for gas discharge of the laser gas to the discharge electrodes; Of the wall materials that make up the body,
At least a wall material of a member corresponding to a predetermined position is made of a dielectric material, and a pair of discharge electrodes is embedded in the wall material made of the dielectric material.

[0005] In the gas laser oscillator according to the present invention, the discharge electrode may be arranged closer to the discharge portion than the center of the thickness of the dielectric.

[0006] The gas laser oscillator according to the present invention comprises a CO
_It may be a _two- laser oscillator.

In the gas laser oscillator according to the present invention, the discharge power value may be 1 kW or more, and the thickness of the dielectric material on the non-discharge side across the discharge electrode may be 5 mm or more.

[0008]

FIG. 5 shows an example of a configuration of a gas laser oscillator according to the present invention, and FIG. 1 shows a configuration of a discharge electrode section of the gas laser oscillator according to the present invention. An example is shown enlarged. In the figure, 1 is an upper metal electrode and 2 is a lower metal electrode, which are respectively buried in a non-discharge-side dielectric 31 and a discharge-side dielectric 41 made of a single dielectric material. Reference numeral 7 denotes an upper cooling water passage, which is provided in the upper cooling body 11. Reference numeral 8 denotes a lower cooling water passage, which is provided in the lower cooling body 12. Case 9
Upper dielectric 31 and lower dielectric 4 provided as part of
Upper electrode 1 and lower metal electrode 2 embedded in 1
When a voltage is applied from the discharge power supply 10 to the upper dielectric 3
1, a discharge-side portion of the metal electrode 1 and a discharge-side portion of the lower metal electrode 2 in the lower dielectric 41 contribute to discharge as capacitance, and the discharge excites a laser gas, thereby causing laser oscillation. Happens. The laser gas forms a gas flow G so as to circulate between the upper dielectric material 31 and the lower dielectric material 41 by the fan 13 and cools the gas flow by the heat exchanger 14 to enable large output oscillation. The gas laser discharge electrode portion according to the present invention is configured such that the upper and lower metal electrodes 1 and 2 are embedded in two or more different dielectrics made of the same type of dielectric material.
There is no damage to the metal electrode due to the discharge, and there is no local discharge etc. due to void generation at the interface, which has been a problem in joining different kinds of dielectrics in the dielectric part covering the metal electrode, A highly reliable discharge electrode can be obtained.

Next, a method of designing the thickness of the lower dielectric and the upper dielectric will be described. The thickness of these dielectrics on the discharge side of the metal electrode is determined from the discharge characteristics of the gas laser. The amount of power (discharge power) input to the gas laser is determined by the following equation (1). W = π · f · C _g · V _op ^* · {(V _op ) ² − (V _op ^* ) ² }
^1/2 -------- (1) where f is the frequency of the discharge voltage, C _g
Is the capacitance of the dielectric (the upper and lower sides of the electrode), V _op ^* is the voltage applied to the discharge part regarded as resistance, and V _op is the peak value of the discharge voltage. C _g is determined by the following equation (2). C _g = 1/2 · ε · S / d Here, ε is the dielectric constant of the dielectric, S is the area of the dielectric, and d is the thickness of the discharge side portion of the dielectric. V _op ^* is
A value that varies depending on the gas type, gas pressure, and discharge gap length, and is determined experimentally. For example, if the gas type is CO
₂ : a mixed gas of CO: N ₂ : He = 8: 4: 60: 28,
Assuming a pressure of 60 Torr and a discharge gap length of 40 mm,
V _op ^* = 5 kV is obtained. Note that the details of the equation (1) are
For example, it is disclosed in “Transmission of CO ₂ laser by high-frequency silent discharge”, Transactions of the Institute of Electrical Engineers of Japan, A, 104, 4, 217 (1984), Tanaka, Yagi, and Tabata.

The thickness of the portion of the dielectric on the non-discharge side with respect to the metal electrode is designed to be strong enough to withstand the difference between the external atmospheric pressure and the pressure inside the housing. The inside of the housing is evacuated to vacuum because it is necessary to replace the atmosphere with laser gas. Therefore, the difference between the atmospheric pressure and the maximum pressure in the housing is 1 atm. The maximum value σmax of the bending stress generated by the pressure difference of 1 atm is calculated assuming that the load is equally distributed on the rectangular plate as follows. Assuming that the shape of the dielectric is a rectangular body having a short side a, a long side b, and a thickness h, and the pressure is p, σmax = β1 · p · a ² / h ² ----------- -(2). Here, β1 is a coefficient determined by b / a. For example, if a = 300 mm and b = 600 mm, β
1 = 0.62. p at atmospheric pressure (1.03 × 10 ^-2 k
gf / mm ² ) and the calculation of equation (2), σmax = 574.7 / h ² [kgf / mm ² ]. If the dielectric is made of alumina ceramic and the withstanding bending strength is 30 kgf / mm ² , h> 4.4 mm. In the case of using alumina ceramic, the discharge electrode used for a CO2 laser having a discharge power value exceeding 1 KW is used. If the size of the corresponding dielectric material is about 600 mm × 300 mm, and the thickness of the non-discharge side portion of the dielectric with the metal electrode interposed therebetween is about 5 mm, it can function as a housing. You can see that.

As described above, of the dielectric of the discharge electrode in the gas laser oscillator according to the present invention, the thickness of the portion on the discharge side across the metal electrode is determined from the discharge characteristics of the gas laser oscillator. The thickness of the discharge side portion is determined from the strength of the gas laser oscillator as a housing, and the thickness of the non-discharge side portion is generally larger than the thickness of the discharge side portion.

Next, an example of a method for manufacturing a discharge electrode of a laser oscillator according to the present invention will be described with reference to FIG. In FIG. 3A, first, a ceramic sheet such as alumina ceramic is kneaded with a binder to prepare a green sheet 22 in a semi-dry state.
A green sheet 23 having a predetermined discharge-side thickness is formed on the transfer table 21 by using the method described above. Next, as shown in FIG. 3B, the metal electrode 1 is placed on the green sheet 23, pre-fired in a firing furnace 24, and an appropriate amount of binder contained in the green sheet is removed by heating. Gives strength as an object. This preliminary firing ensures the surface accuracy of the dielectric. Next, the non-discharge side dielectric green sheet 25
3A is adjusted to a predetermined thickness in the same manner as in FIG. 3A, and as shown in FIG. The main firing is performed. By this firing, the green sheets 23 and 25 are formed by heating.
Together, one of the discharge electrodes is formed. The other of the discharge electrodes is formed in the same manner.

In this embodiment, alumina ceramic is used as the dielectric material. However, the dielectric material is not limited to this, and may be a material such as silicon oxide or silicon nitride. If it is, there is no particular limitation.

In this embodiment, a green sheet is used as a dielectric material before firing, but is not particularly limited as long as the dielectric material has a predetermined thickness.
The ceramics dissolved in the binder may be formed by a method of applying by a roll coating method, or the dielectric formed by the roll coating method and the green sheet-shaped dielectric may be formed by a discharge side dielectric, It may be mixed as a discharge-side dielectric, and other forms may be used as long as they are made of the same dielectric material.

Further, in this embodiment, after the discharge-side dielectric is pre-fired, the non-discharge-side dielectric is laminated. However, the non-discharge-side dielectric is not fired and the discharge-side dielectric is not fired. Laminated,
The discharge-side dielectric and the non-discharge-side dielectric can be simultaneously heated and molded at the same time as the metal electrode. In this case, there is an advantage that the number of firing steps can be reduced.

The metal electrode may be a plate-like metal, or the metal electrode may be formed by lining the metal on the lower dielectric green sheet. In addition, the conductor is not limited to a metal, and is not particularly limited as long as it has conductivity. For example, a conductor such as a metallized ceramic surface or a conductive material such as a transparent conductor formed on a ceramic surface may be used. It doesn't matter.

As described above, in the laser oscillator according to the present invention, the thickness of the dielectric material covering the discharge electrode is designed to be different between the discharge side and the non-discharge side. Since the side can have a sufficient thickness as the mechanical strength of the housing, the dielectric material covering the discharge electrodes can be used as a wall material of the housing and used as a flange for confining the discharge gas in the housing. However, it goes without saying that the discharge electrode and the dielectric material need not be provided on the inner wall of the housing and used as a flange for containing the discharge gas.

Embodiment 2 FIG. 2 is a view showing another configuration example of the discharge electrode of the gas laser oscillator according to the present invention. In the discharge electrode of FIG. 2, the above-mentioned electrode is a dielectric plate having a metal layer adhered to one side,
The metal layer side is used as a bonding surface and bonded to a dielectric of the same dielectric material. In FIG. 2, components denoted by the same reference numerals as those in FIG. 1 are the same or corresponding components. Reference numeral 31 denotes an upper dielectric plate having a metal layer 1 adhered on one side, and reference numeral 41 denotes a lower dielectric plate having a metal layer 2 adhered to one side, each of which is an upper second dielectric made of the same kind of dielectric material. 32, lower second dielectric material 42
Is joined to. As described above, after preparing the upper dielectric plate 31 and the lower dielectric plate 41 in advance, by arranging the metal electrodes, it is easy to make the thickness of the dielectric uniform,
From the viewpoint of the power input to the discharge, since the capacitance in contact with the discharge side from the upper and lower metal electrodes 1 and 2 is spatially uniform, the spatial distribution of the input discharge power is also uniform, Uniformization of the laser medium and stabilization of the laser output are easily realized.

Third Embodiment FIG. 4 shows another method of manufacturing a discharge electrode of a laser oscillator according to the present invention. In the present embodiment, first, as shown in FIG. 4A, a non-discharge-side dielectric provided with a groove for inserting a metal electrode is formed by cutting a die or a block-shaped dielectric. Next, as shown in FIG. 4B, a metal electrode is embedded in this groove. And FIG.
As shown in (c), the discharge electrodes are formed by laminating the discharge-side dielectrics and performing heat molding in the firing furnace 27.

As an example of a structure in which an electrode that performs discharge between opposed electrodes is covered with a dielectric, an example of an ozone generator or the like is as follows.
A structure in which a discharge electrode for silent discharge is coated with a glass lining is known. However, as in the present invention, in a discharge electrode used for a gas laser electrode to which high power is applied, discharge of a dielectric material constituting the discharge electrode is performed. The thickness of the discharge side and the thickness of the non-discharge side sandwiching the electrodes are respectively designed for discharge,
It is not specified from the viewpoint of mechanical design and is not adjusted to the optimum thickness.

[0021]

As described above, according to the present invention, in a gas laser oscillator in which a laser gas is sealed in a housing and a discharge is generated between opposed discharge electrodes to cause laser oscillation, a single discharge electrode is used. Since the conductor layer is embedded in the dielectric made of the above dielectric material, local discharge occurs at the interface formed by joining different kinds of dielectrics due to voids, etc. And a highly reliable discharge electrode can be obtained.

Further, the thickness of the dielectric in contact with the discharge side of the metal electrode is determined from the viewpoint of a power supply specification for injecting required power into the discharge space, and the thickness of the dielectric in contact with the non-discharge side of the metal electrode is determined as follows. By determining from the structural specifications, it is possible to obtain a gas laser discharge electrode having an optimum dielectric thickness that separately satisfies the electrical requirements and the structural requirements.

In addition, according to the present invention, the electrode is formed by integrating the dielectric plate having the metal layer adhered on one side to the dielectric of the same dielectric material with the metal layer side as the bonding surface. , The thickness of the dielectric plate is easy to manufacture uniformly, and from the viewpoint of power supply to the discharge, the spatial distribution of the capacitance from the metal electrode to the discharge side becomes uniform, and the spatial distribution of the discharge power applied is also uniform Thus, the laser medium can be made uniform and the laser output can be stabilized.

Further, according to the present invention, since the cooling body for cooling the discharge part and the metal electrode for discharge are not electrically connected, the conductivity of the cooling water can be easily managed.

[Brief description of the drawings]

FIG. 1 is a view showing a discharge electrode of a gas laser oscillator according to the present invention.

FIG. 2 is a view showing a discharge electrode of the gas laser oscillator according to the present invention.

FIG. 3 is a view showing a method of manufacturing a discharge electrode of a gas laser oscillator according to the present invention.

FIG. 4 is a view showing a method of manufacturing a discharge electrode of a gas laser oscillator according to the present invention.

FIG. 5 is a diagram showing a configuration of a gas laser oscillator according to the present invention.

FIG. 6 is a view showing a discharge electrode of a conventional gas laser oscillator.

[Explanation of symbols]

1 upper metal electrode, 2 lower metal electrode, 3 upper first dielectric, 4 lower first dielectric, 5 upper second dielectric, 6
Lower second dielectric, 7 upper cooling water passage, 8 lower cooling water passage, 9 housing, 10 discharge power, 11 upper cooling body, 1
2 lower cooling body, 13 fan, 14 heat exchanger, 20
Feed roll, 21 conveyor, 22 green sheet,
23 green sheet for discharge side dielectric, 24 firing furnace,
25 Non-discharge side dielectric green sheet, 26 Firing furnace, 27 Firing furnace, 31 Upper dielectric plate, 32 Upper second dielectric, 41 Lower dielectric plate, 42 Lower second dielectric, G Laser gas flow

Continued on the front page (72) Inventor Kazuhiko Fukushima 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Yasushi Hisaoka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. In-house F term (reference) 5F071 AA05 CC07 EE02 FF04 JJ05 JJ09

Claims (4)

[Claims] 1. A gas laser casing for enclosing a laser gas therein, gas circulating means for circulating the enclosed laser gas inside the gas laser casing, and applying a voltage to the laser gas at a predetermined position of the circulating laser gas. A pair of discharge electrodes for applying and discharging gas; and a discharge power supply connected to the pair of discharge electrodes and supplying a voltage for discharging the laser gas to the discharge electrodes to form the housing. A gas laser oscillator wherein at least a wall material of a member corresponding to the predetermined position among the wall materials is made of a dielectric material, and the pair of discharge electrodes are embedded in the wall material made of the dielectric material. 2. The gas laser oscillator according to claim 1, wherein the discharge electrode is disposed closer to a discharge portion than a center of a thickness of the dielectric. 3. The gas laser oscillator according to claim 1, wherein the gas laser oscillator is a CO ₂ laser oscillator. 4. A discharge power value of said gas laser oscillator is 1
2. The kW or more, and the thickness of the dielectric material on the non-discharge side sandwiching the discharge electrode is 5 mm or more.
4. The gas laser oscillator according to any one of items 1 to 3.