JPH0340476A - Gas laser exciting method and gas laser device - Google Patents

Abstract

PURPOSE:To enhance a laser device in output by a method wherein an auxiliary electrode is arranged in a discharge space, a certain discharge voltage is applied to a primary electrode, and then a pulse voltage whose polarity is opposite to that of the discharge voltage is applied to the auxiliary electrode so as to temporarily enhance the electric field of the discharge space in intensity. CONSTITUTION:When the discharge voltage of a discharge capacitor 13 rises and a voltage between primary electrodes 4a and 4b reaches to a constant voltage Vc close to the withstand voltage of a discharge space C, a pulse voltage Vp of reverse polarity is applied to an auxiliary electrode 16 from a pulse generator 14 through the intermediary of an ionizing gap 15. Then, an electric field gradient of spaces C1 and C2 becomes larger than that when the pulse voltage Vp is not applied. By this setup, the discharge gap 15 starts discharging, the voltage Vp of reverse polarity is applied to the auxiliary electrode 16, and ionized electrons are generated through ultraviolet rays generated with the discharge of the gap 15. The electrons concerned are multiplied in the discharge spaces C1 and C2 through the intermediary of an avalanche mechanism, a spacer between the primary electrodes 4a and 4b becomes conductive, and a large discharge current flows through the spaces C1 and C2 from the capacitor 13. By this constitution, a gas laser of this design can be enhanced in laser output.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an improvement of a pulse discharge excited gas laser, and involves switching the main discharge using a medium gas in the discharge space, thereby increasing the speed of the main discharge circuit. The present invention relates to a gas laser excitation method that makes it possible to eliminate the need for a large current switch and increase the laser output by increasing the ionization density in the discharge space, and to a gas laser device using the same.

(Prior art) In pulse discharge excited gas lasers such as excimer lasers, CO2 lasers, N2 lasers, etc., in order to stabilize the discharge and improve the beam pattern, the discharge space is Discharge circuits of the so-called pre-ionization method, which ionize the particles in advance, are widely used.

FIG. 5 shows an example of the pre-ionization type discharge circuit, in which a high-voltage pulse generating circuit A consisting of a charging resistor 1, a capacitor 2, a cyrotron 3, etc., and main electrodes 4a and 4b are shown.
- The main part of the discharge circuit is constituted by an automatic pre-ionization discharge circuit B consisting of a buffer capacitor 5, a pre-ionization gap 6, etc., and when the voltage of the capacitor 2 rises to a certain value by charging from the high-voltage power supply 7, Thyratron 3
operates, a discharge voltage is applied between the main electrodes 4a and 4b, and a discharge is generated in the pre-ionization gap 6, causing the sealed container 8
The medium gas inside is automatically pre-ionized, thereby generating a stable main discharge in the main discharge space C between the main electrodes 4a and 4b.

Therefore, in the pre-ionization type discharge circuit as described above, in order to increase the output efficiency of the laser output, the main electrodes 4a, 4b are
Hou 1 joins in between! It is necessary to make the voltage rise as steep as possible. This is because the main discharge space C is already pre-ionized at the same time as the discharge voltage is applied, so if the voltage rises slowly, the main discharge will start at a low discharge voltage, resulting in wasted input energy. This is because it is consumed.

Therefore, in the conventional pre-ionization type discharge circuit, a high-speed, large-current switch mechanism such as a thyratron or a spark gap is used in the main discharge circuit, and the inductance of the discharge circuit is made as small as possible to reduce the discharge voltage. The rise of the voltage is made steep, so that the voltage at the start of the main discharge is increased.

However, thyratrons, which switch large currents at high speeds, are expensive and have a relatively short operating life.

When the laser device is used industrially, it is extremely uneconomical. Further, if an attempt is made to lower the inductance of one circuit, significant restrictions will be placed on the shape of the circuit, and various problems will arise in manufacturing.

On the other hand, the applicant of this patent has developed a delayed ionization type discharge circuit having a configuration as shown in FIG. 6 in order to solve the problems inherent in the discharge circuit as shown in FIG. are doing.

That is, the delay l! In the mold release discharge circuit, an ionization capacitor 9, a delay gap 10, and ionization electrodes 11a and 1l are used.
A delayed ionization mill HD formed by connecting b-fJi separation discharge gaps 12 in series is the main electrode 4a.

4b, and by adjusting the gap length of the delay gap 10, the main, i! The time from when a discharge voltage is applied to the poles 4a and 4b until a discharge occurs in the ionization discharge gap 12 is delayed.

That is, in the delayed ionization type discharge circuit, the main type i4a.

Even if the rise of the discharge voltage applied to 4b is slow,
This prevents the main discharge from starting when the voltage between the main electrodes 4a and 4b is low, and the main discharge circuit is equipped with a high-speed, large-current switch such as a thyratron or spark gap, as shown in the discharge circuit shown in FIG. Even if the inductance is not provided, or even if the inductance of other parts except the buffer capacitor 5 and the vicinity of the main electrodes 4a and 4b increases somewhat, the loss of input energy will not increase significantly.

However, in the delayed ionization type discharge circuit, the main electrode 4
Since it is not possible to apply a discharge voltage higher than the withstand voltage of the discharge space C to a and 4b, the electric field strength in the discharge space C is relatively weak and the ionization density due to the streamer mechanism is difficult to increase, and as a result, the laser The problem is that the output cannot be sufficiently increased.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problems in conventional pulse discharge excited gas lasers, namely: (1) Is there a backup? Gas lasers equipped with lft-type discharge circuits require a high-speed, large-current switch mechanism such as a thyratron at the main discharge port, and the inductance of the circuit also needs to be reduced, which greatly affects the shape and life of the circuit and switch mechanism. This is an attempt to solve the problems such as; ■ gas lasers equipped with delayed ionization discharge circuits tend to have insufficient ionization density in the discharge space C, making it impossible to obtain high laser output; To provide a gas laser excitation method that does not require a switch mechanism such as a large-capacity thyratron or a spark gap, and that can obtain high laser output by ionizing the discharge space at high density, and a gas laser device using the same. It is something to do.

(Means for Solving the Problems) In order to solve the above problems, in the present method invention, in a gas laser excitation method that excites a medium gas by electric discharge, after applying a voltage between the main electrodes, 'R' is applied by a pulse voltage. ，
At the same time as a discharge is generated in the separation gap, a pulse voltage of opposite polarity to the voltage of the main electrode is applied to an auxiliary electrode provided in the discharge space to temporarily strengthen the electric field strength in the discharge space, thereby preventing ionization of the discharge space by the streamer mechanism. The basic configuration of the invention is to generate the main discharge in a state of increased density and to switch the main discharge using a medium gas in the discharge space.

Further, in the present device invention, in a gas laser device that excites a medium gas by electric discharge, a pair of main electrodes, an auxiliary electrode provided in a discharge space, and an ionization gap are arranged in a closed container in which a medium gas is sealed. A voltage is applied from a high voltage power source to the main electrode and the main discharge capacitor connected in parallel thereto, and a pulse voltage of opposite polarity to the voltage of the main electrode is applied to the auxiliary electrode, thereby increasing the electric field strength in the discharge space. The basic structure of the invention is to increase the ionization density and generate the main discharge under high ionization density.

(Function) The main discharge capacitor is charged from the high voltage power supply through the charging resistor, and the charging voltage of the main discharge capacitor is applied between the pair of main electrodes. After the charging voltage reaches a constant voltage value within a range that does not exceed the withstand voltage of the discharge space in a direct current or pulsed manner, a pulse voltage of opposite polarity is applied from a pulse generator to the auxiliary electrode interposed between the main electrodes. applied to the gap.

When the pulse voltage of the opposite polarity is applied to the ionization gap, a discharge occurs in the ionization gap.

Due to the conduction of the gap, a pulse voltage of opposite polarity is applied to the auxiliary electrode, and the electric field gradient of the discharge space divided into two via the auxiliary electrode top 6 temporarily increases sharply.

As a result, the ionized electrons generated in the discharge space by the ultraviolet rays accompanying the discharge in the ionization gap are effectively multiplied by the so-called streamer mechanism or electron avalanche mechanism under the high electric field gradient, resulting in a high density in the discharge space. It becomes an ionized state.

The discharge space has a high density of 1! When separated, the space functions as a conductor, and the energy of the charge stored in the main discharge capacitor is efficiently injected into the discharge space, thereby significantly increasing the laser output.

On the other hand, the energy supplied from the pulse generator to the auxiliary electrode is small enough to ionize the discharge space of the ionization gap, and is almost negligible compared to the energy of the main discharge circuit. It is the amount of energy. As a result, the laser output efficiency of the discharge circuit is not affected at all by this, and even if a thyratron or the like is used as a switch mechanism in the pulse generator, its capacity can be extremely small, and its lifespan is a problem. There's no way it's going to happen.

(Example) Hereinafter, the present invention will be described in detail based on the drawings.

The first drawing is the first drawing of a gas laser device to which the method invention is applied.
This shows an example, and in Figure 1, 1 is a charging resistor, and 4 is a charging resistor.
a, 4b are main discharge electrodes, 7 is a high voltage power supply, 8 is a sealed container, 13 is a main discharge capacitor, 14 is a pulse generator, 1
5 is an ionization gap, 16 is an auxiliary electrode, and C is a discharge space.

The sealed container 8 has a predetermined length determined by the oscillation output, and has a total reflection mirror and an output mirror (not shown) at both ends.
A gas serving as an oscillation medium is sealed inside.

Further, the auxiliary electrode 16 is arranged approximately in the center between the main electrodes 4a and 4b, and is a so-called mesh-like plate electrode.

The charging voltage of the main discharge capacitor 13 increases, and the main electrode 4
A voltage value V where the voltage between a and 4b is close to the # voltage of discharge space C
c, a pulse voltage Vp of opposite polarity is applied from the pulse generator 14 to the auxiliary electrode 6 through the ionization gap 15.

FIG. 2 shows that the pulse voltage Vp of the opposite polarity is applied to the auxiliary electrode 16.
This shows the state of the electric field gradient in the discharge spaces C□, C2 when the voltage is applied to the discharge spaces C, C, and the electric field gradient in the spaces C, C, temporarily becomes a straight line E, E3, and the pulse voltage Vp
The electric field strength is higher than the electric field strength Eo before being applied.

When the pulse voltage Vp is applied from the pulse generator 14,
As described above, a discharge first occurs in the ionization gap 15, a pulse voltage Vp of opposite polarity is applied to the auxiliary electrode 16, and ionization electrons are generated by the ultraviolet rays generated as a result of the discharge in the gap. Further, the generated ionized electrons are multiplied through a so-called streamer mechanism or electron avalanche mechanism in the discharge spaces C1 and C2 where the electric field strength is increased, and a higher density ionized state is created in the discharge spaces Ci and C2. appear within. As a result, conduction occurs between the main electrodes 4a and 4b, and a large discharge current from the main discharge capacitor 13 flows into the discharge spaces C□ and C2.

In this embodiment, the auxiliary electrode 16 is a single mesh-like plate electrode, but the auxiliary electrode may be a plurality of mesh plates arranged in parallel at regular intervals. By using the auxiliary electrode 16 made up of a plurality of mesh plates, the discharge space C can be made larger.

Further, in this embodiment, the ionization gap 15 and the auxiliary electrode 16 are connected in series, and the pulse voltage Vp is applied from the pulse generator 14 to the auxiliary electrode 16 through the discharge on the ionization gap 5. Gap 15 and auxiliary electrode 1
6 may be separated from each other, and a pulse voltage may be applied to each separately from the same or separate power source.

Furthermore, although this embodiment does not specifically describe adjustment of the time difference between the application of the voltage Vc to the main electrodes 4a and 4b and the application of the pulse voltage Vp to the auxiliary electrode 6 and the ionization gap 15, Of course, a mechanism for arbitrarily adjusting the time difference may be provided.

In addition, in this embodiment, the main discharge capacitor 13 is arranged inside the closed container 8, but it is of course possible to arrange the main discharge capacitor 13 outside.

3 and 4 show second and third embodiments of the gas laser apparatus to which the present method invention is applied.

In the embodiment shown in FIG. 3, the auxiliary electrode 16 is formed by two auxiliary electrode plates 16a and 16b that are combined in a face-to-face configuration.
A pulse voltage Vp is applied to each of a and ↓6b.

On the other hand, in the embodiment shown in FIG. 4, a pair of main electrodes 4a,
Auxiliary electrode plates 1.6a, 1.4b are arranged in a line at intervals, and are disposed opposite to each main electrode 4a, 4b.
The auxiliary electrode 16 is formed by connecting the electrodes 6b in series. In addition, the pulse voltage VP is ionization gap 1
5 to the picture electrode plates 16a and 16b.

In the embodiments shown in FIGS. 3 and 4, the discharge from the main discharge capacitor 3 is caused by the main electrodes 4a,
The surface discharge section S□js2 may be used as an oscillator or an amplifier separately, or one discharge section S□ may be used as an oscillator and the other discharge section S2 may be used as an oscillator or an amplifier. It is also possible to use it as an amplifier.

In the embodiment shown in FIG. 1, the auxiliary electrode 16 is located within the discharge space C, which may have a negative effect on the mode pattern when forming a laser resonator.
In the case of FIGS. 3 and 4, there is no adverse effect on the mode pattern.

(Effect of the invention) In the present invention, an auxiliary electrode is disposed within the discharge space,
After applying a constant discharge voltage to the main electrode, a pulse voltage of opposite polarity to the discharge voltage is applied to the auxiliary electrode to temporarily increase the electric field strength in the discharge space. The multiplication of ionized electrons by the streamer mechanism or electron avalanche mechanism generated in the space becomes extremely large, and the ionization density in the discharge space becomes extremely high. As a result, a large discharge current is more smoothly supplied from the discharge capacitor into the discharge space, and the laser output is significantly increased.

Further, in the present invention, after the discharge voltage Vc between the main electrodes 4a and 4b reaches a predetermined voltage value, a discharge is generated in the ionization gap, and a pulse voltage of opposite polarity is applied to the auxiliary electrode. Because of this structure, the energy of one circuit is input into the discharge space without wastage, and the energy input from the pulse generator to the auxiliary electrode is also extremely small. As a result, laser output efficiency is significantly improved, and
Even if a thyratron is used as a pulse generator, the capacity is extremely small, so there is no problem with its lifespan or the like.

Furthermore, in the present invention, the medium gas itself in the discharge space is used as a switching mechanism for high speed and large current to switch the main discharge, so unlike the conventional pre-ionization type discharge circuit, There is no need for a switch mechanism such as a thyratron or spark gap for high-speed, large-current use in the main discharge circuit, and there are no major restrictions on the shape of the circuit due to inductance. As a result, it becomes possible to extend the life of the laser device and significantly reduce manufacturing costs.

Furthermore, by changing the form of the auxiliary electrodes, it is possible to completely differentiate the discharge portions for each main electrode. As a result, it is possible to form an oscillator and an amplifier in one sealed container, which is extremely convenient in practice, and since the auxiliary electrode is located outside the discharge part, it is possible to form a mode pattern when constructing a laser resonator. There is no negative effect on the.

As mentioned above, the present invention has excellent practical utility.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a gas laser device to which the present method invention is applied. FIG. 2 is an explanatory diagram of the electric field gradient in the discharge space of FIG. 1. FIG. 3 is a circuit diagram showing a second embodiment of the laser device. FIG. 4 is a circuit diagram showing a third embodiment of the laser device. FIG. 5 shows a pre-ionization type discharge circuit of a conventional pulse discharge excited type gas laser device. FIG. 6 shows a delayed ionization type discharge circuit previously developed by the inventor of the present invention. 4a and 4b are main electrodes, 7 is a high voltage power supply, 8 is a sealed container,
13 is a main discharge capacitor, 14 is a pulse generator, 15
16 is an ionization gap, 16 is an auxiliary electrode, and 16a. 16b is an auxiliary electrode plate, Vc is a discharge voltage, Vp is a pulse voltage, S + Sa is a discharge part, and C is a discharge space. Figure 2, Figure 4, Figure 4, Figure 6

Claims (9)

[Claims] (1) In a gas laser excitation method in which a medium gas is excited by discharge, a voltage is applied between the main electrodes, and then a pulse voltage is used to cause a discharge in the ionization gap, and the voltage of the main electrode is applied to the auxiliary electrode provided in the discharge space. A pulse voltage of opposite polarity is applied to temporarily strengthen the electric field strength in the discharge space, and a main discharge is generated with the streamer mechanism increasing the density of ionization in the discharge space. A gas laser excitation method characterized in that the switching is performed. (2) Claim (1) in which the time difference between the application of the voltage between the main electrodes and the application of the pulse voltage to the auxiliary electrodes is adjustable.
).The gas laser excitation method described in ). (3) The gas laser excitation method according to claim (1), wherein an ionization gap is discharged by a pulse voltage having a polarity opposite to that of the main electrode voltage, and the pulse voltage is applied to the auxiliary electrode through the ionization gap. (4) A claim in which the main discharge in the discharge space is made into two separate discharges between a pair of main electrodes and an auxiliary electrode.
The gas laser excitation method described in 1). (5) In a gas laser device configured to excite a medium gas by electric discharge, a pair of main electrodes, an auxiliary electrode provided in a discharge space, and an ionization gap are arranged in a closed container filled with a medium gas, and the A voltage is applied from a high-voltage power source to the main electrode and the main discharge capacitor connected in parallel to the main electrode, and a pulse voltage of opposite polarity to the voltage of the main electrode is applied to the auxiliary electrode to increase the electric field strength in the discharge space. A gas laser device configured to generate a main discharge under ionization density. (6) The gas laser device according to claim (5), wherein the discharge space is provided with an auxiliary electrode formed by a plurality of mesh plates arranged in parallel at regular intervals. (7) The gas laser device according to claim (5), wherein the ionization gap and the auxiliary electrode are connected in series, and the ionization gap is discharged by a pulse voltage to apply the pulse voltage to the auxiliary electrode. (8) A pair of main electrodes are arranged facing each other, and an auxiliary electrode consisting of two auxiliary electrode plates are inserted in the center of both, and between each main electrode and the auxiliary electrode plate. The gas laser device according to claim 5, wherein the gas laser device is configured to form two separate discharge portions. (9) A pair of main electrodes are arranged in a straight line at a constant interval, and each main electrode and an auxiliary electrode plate arranged opposite to each other are connected in series to form an auxiliary electrode. The gas laser device according to claim 5, wherein the gas laser device is configured to form two separate discharge portions between the gas laser device and the plate.