JPS6232672A - Laser oscillator - Google Patents

Abstract

PURPOSE:To improve the reliability of the device and to elongate the life, by providing hollow conductors, in which refrigerant flows, at the back surface of a first main electrode having many holes so as to contact with the surface, and performing preliminary ionization discharge between a preliminary electrode and the hollow conductors. CONSTITUTION:Preliminary ionization discharge 6 is carried out not between a preliminary ionization electrode 4 and a first main electrode 5, but between a preliminary ionization electrode 6 and hollow conductors 16. Therefore, the problem of the damage of the first main electrode 5 due to the preliminary discharge is eliminated. The first main electrode 5 is always cooled indirectly with refrigerant 17 flowing in the hollow conductors 16. Heating of the electrodes at the time of highly repeated operations is eliminated. Therefore, the main discharge is not transformed into arc discharge and is always stable. thus the laser output becomes stable. The problem of the damage of the main electrode pair 5 and 7 due to the arc discharge transformed from the main discharge is eliminated.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to improvements in laser oscillators.

[Conventional technology]

Figure 6 shows a typical horizontally pumped Hals laser of this kind, with a 1% excitation laser (e.g. ArF).
, KrF e XeF , , (1) is a high voltage power supply, (2) is a pulse charging circuit,
, 3) is the inductance for measuring current uniformity, (
4) is a preliminary separation electrode, and (5) is a electrode with many holes.
.

Lord t4. (6) is a preliminary ionization discharge performed before the main discharge, (7) is the second main electrode facing the first king 11E electrode, and (8) is the peaking capacitor for causing the main discharge, and the main electrode is the peaking capacitor for causing the main discharge. +51 and (7) are connected in parallel. (9) is the discharge excitation part where the laser is excited by the main discharge, αQ is the laser oscillation optical axis, (b) is the laser gas, (2) is the V-laser housing that encloses the laser gas, aa is the total reflection mirror, and αQ is the laser oscillation axis. is a partially transmitting mirror, and α valley is a laser beam.

Next, the operation will be explained. As an example, the case of a KrF laser will be explained. Enclosed in the laser housing (a),
1j of cooled Kr, F2, and He (or Ar or Ne) is poured between the first main electrode [5] and the second main electrode (1) from the direction of the arrow. ing.

Pulse charging circuit (2) driven by high voltage power supply (1)
charges the peaking capacitor (8) in a pulsed manner.

At this time, since the gap between the pre-ionization electrode (4) and the first main electrode (5) forms part of the charging path, a pre-ionization discharge (6) is performed during the charging period. Since this pre-ionization discharge (6) is an arc discharge, it generates a large amount of ultraviolet light. The generated ultraviolet light spreads throughout the discharge excitation part (9) through a large number of holes provided in the first main electrode (5).

Thereby, the vicinity of the first main electrode.

In addition, the laser gas (
b) is in a weakly ionized state (T & electron density ne = 10'-10
・ko/cd). By charging the peaking capacitor (8).

When the voltage between the first main electrode (5) and the main electrode (1) of wJ2 reaches the discharge starting voltage, the peaking capacitor (
The charges stored in 8) flow between the first main electrode (5) and the main electrode (7) of 82, and a pulse discharge is formed in the discharge excitation part (9).

This is because the discharge excitation part (9) is brought into a uniform preliminary ionization state by ultraviolet light in advance, resulting in a uniform glow discharge.

In the discharge excitation part (9) formed by this discharge, KrF in an excited state is generated, and one population inversion is formed.

Laser oscillation is generated by an optical resonator consisting of a total reflection mirror @ and a partial reflection mirror α, which are arranged opposite to each other with the discharge excitation part (9) in between, and a laser beam (T) is emitted from the partial reflection mirror α4.

By the way, as shown in Fig. 6, one of the two poles has a structure with a large number of holes, and ultraviolet light for pre-ionization is applied to it.
The method of irradiating from the back side of the electrode is an extremely effective method when a uniform main discharge is required over a large cross section.

On the other hand, in actual applications, this type of pulsed laser performs high repetition oscillation of several tens to hundreds of pp3 per second.
What is important is that an average output of several tens to several hundred W can be obtained.

[Problem that the invention seeks to solve]

However, since the conventional device is configured as described above, the pre-ionization discharge (6), which is an arc discharge, causes
The first main electrode (5) is severely damaged.

Moreover, the heat capacity of the main electrode (5) of fal is the same as that of the second main electrode (
7), it is easily heated by the preliminary separation discharge (6) and the main discharge during high repetition oscillation, and the heat cannot be easily removed by the laser gas (b). This heating of the wcl main electrode (5) tends to cause the main discharge to become an arc discharge, making the laser output unstable, and the main electrode of the heat removal 1 is also significantly damaged.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a reliable high repetition rate laser oscillator.

(Means for solving the problem) A laser oscillator according to the present invention has an 8g laser oscillator having a large number of holes.
A hollow conductor through which a refrigerant flows is installed behind the main electrode 1, and pre-ionization discharge is performed between the pre-ionization electrode and the hollow conductor.

[For production]

The first main discharge electrode of the present invention has an indirect cooling effect due to the hollow conductor through which the coolant flows, so that it does not get heated even during high repetition oscillation operation, and pre-ionization discharge does not occur directly on its surface. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be explained with reference to the drawings.
The figure shows -'=1! of the laser oscillator of this invention! A vertical sectional view showing the example, and Figure 2 is a cross-sectional view of Figure 1 taken from the line ■-■.
σ0 is a refrigerant flowing through a hollow conductor that is fixed to the first main electrode (5) by welding or the like and has good thermal contact.

Next, the operation of this invention will be explained. The basic operation is the same as the conventional example, but the pre-ionization discharge (6) is not between the pre-ionization electrode (4) and the first main electrode (5), but between the pre-ionization electrode (6) and the hollow conductor αQ. It is held between.

Therefore, the first main electrode [
5) The problem of damage is fl (becomes).

Furthermore, the first main electrode (5) is always indirectly cooled by the coolant αη flowing through the hollow conductor α0.

The problem of electrode heating during high repetition operation is also eliminated. From this point on, the main discharge always becomes stable without shifting to arc discharge, and therefore the laser output becomes stable. Furthermore, due to the arc discharge of the main discharge, the royal release @1 pole pair f51,
(7) There is also the problem of damage.

rjIn the above embodiment, preliminary ionizing discharge is applied to the hollow conductor αQ only from one direction, but as shown in FIG. Pre-ionization discharge may be performed from the beginning, and in this case, uniform pre-ionization is promoted and stable excited discharge is performed.

Further, as shown in FIG. 4, a protrusion may be provided on the surface of the hollow conductor αe, and in this case, the pre-ionization electrode (4)
The electric field strength between and protrusion 4 increases, and each pre-ionization electrode (
The pre-ionization discharge (6) in step 4) is now performed reliably.

Furthermore, as shown in Fig. 5, the shape of the hollow conductor α may be a pipe with a triangular cross section. In this case, in addition to the effect of the protrusion shown above, the pre-ionization discharge (6) This allows the ultraviolet light to penetrate into the discharge excitation part (9) more easily than in the previous structure, and stable discharge excitation is promoted.

Furthermore, although the first main electrode (5) is generally made of a metal mesh, a punching board with a large heat capacity may also be used. It is smaller and the reliability of the device is improved.

In addition, the coolant ση flowing into the hollow conductor αψ is water.

In addition to insulating oil, fluorinated halogenated hydrocarbon refrigerants such as ammonia and chlorofluorocarbons, mixtures of two or more of the above, and the like are used.

〔Effect of the invention〕

As described above, according to the present invention, a hollow conductor through which a refrigerant flows is installed on the back surface of a first main electrode having a large number of holes so as to be in contact with the first main electrode, and pre-ionization discharge is caused between the pre-ionization electrode and the hollow conductor. Since the configuration is such that the operation is carried out between 1 and 2, the reliability of the device is improved and the life of the device is extended.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a pulsed laser oscillator according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG.
3 to 5 are longitudinal sectional views showing the main parts of a pulsed laser oscillator according to another embodiment of the present invention, FIG. 6 is a longitudinal sectional view showing the main parts of a conventional pulsed laser oscillator, and FIG. 7 is a longitudinal sectional view showing the main parts of a conventional pulsed laser oscillator. A cross-sectional view taken along the line ■-■ in FIG. 6. In Figure 2, (4) is a pre-ionization electrode, (5) is a first main electrode, (6) is a pre-ionization discharge, (7) is a second main electrode,
(8) is the peaking capacitor, 0υ is the laser gas,
GQ is a hollow conductor, qη is a refrigerant, and a decoy is a protrusion. 2. The same reference numerals in the figures indicate the same or equivalent parts.

Claims (5)

[Claims] (1) A first main electrode having a large number of holes and a second main electrode having no holes, arranged facing each other in the laser gas, and a plurality of main electrodes arranged on the back surface of the first main electrode. A laser oscillator comprising a pre-ionization electrode and a capacitor connected in parallel between the first main electrodes, wherein a hollow conductor is disposed in contact with the back surface of the first main electrode and a refrigerant flows therein; A laser oscillator characterized in that, prior to the discharge between the main electrodes, a preliminary ionization discharge is performed between the preliminary ionization electrode and the hollow conductor. (2) Claim 1, wherein the refrigerant flowing through the hollow conductor is water, insulating oil, ammonia, fluorohalogenated hydrocarbon refrigerant, or a mixture of two or more of these refrigerants. Laser oscillator described. (3) The laser oscillator according to claim 1 or 2, wherein the first main electrode is composed of a metal mesh or a punching board. (4) The laser oscillator according to claim 1, 2, or 3, wherein the hollow conductor has a protrusion on its surface. (5) The laser oscillator according to claim 1, 2 or 3, wherein the hollow conductor is a pipe having a triangular cross section.