JPH0439974A - Pulse laser device - Google Patents

Abstract

PURPOSE:To unify the electric distribution between electrodes and extend the application range of space where glow discharge is generated. CONSTITUTION:When a switch S1 is closed, the voltage charged in a capacitor C1 is applied between main electrodes 1 and 2. During the application of the voltage, every spark discharge gap 3 is discharged within a fixed time. This spark discharge generates ultraviolet light, which preionizes laser gas between the main electrodes 1 and 2 on the opposite sides. When the spark discharge gap 3 discharges, the charge in the capacitor C1 moves to a capacitor C2. The voltage is increased between the main electrodes 1 and 2 so that the glow discharge may be ignited between the main electrodes 1 and 2. Since the surface configuration of the main electrodes 1 and 2 is adapted to comprise a plurality of functional curves, the electric distribution between the main electrodes 1 and 2 can be unified, which makes it possible to extend the application of space where glow discharge is generated and further enhance the limit value of laser output strength restricted by the current density in the central part of the electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention J (Field of Industrial Application) The present invention relates to a high-output pulse laser device with an improved electrode structure.

(Prior Art) With the remarkable technical progress in laser technology in recent years, high-output pulsed laser devices are being used in various industrial fields, and the development of their layers is required. Among such pulsed laser devices, in particular, in gas-mediated laser devices, in order to obtain good laser oscillation,
It is necessary to generate a spatially uniform discharge in the laser gas, but in pulsed laser devices that generate short pulse laser light such as TEACO2 laser and excimer laser,
The operating gas pressure is as high as several atmospheres, and furthermore, since it contains CO2 gas or halogen gas, which has strong electron adhesion, discharge tends to concentrate and cause arc discharge. In order to prevent this and generate a uniform discharge, a method is generally adopted in which preliminary ionization is performed prior to the main discharge and at the same time a high-speed pulse voltage is applied to generate the discharge in a short time. .

In addition, in order to generate a stable glow discharge in the main discharge space, the main electrode surface shape is such that the electric field strength between the main electrodes is uniformly high at the center of the main electrodes, and It has been considered that the shape gradually decreases toward the end. (For example, SprInger 5eri
es 1n 0ptical 5sciences53”
The CO2La5er, W, J, Wlttem
170, etc.) FIG. 4 shows an example of the main electrode structure of a conventional pulse laser device. That is, in the laser gas, the second main electrode 5 is disposed opposite to the first main electrode 4, and each of the main electrodes 4 and 5 has a plane in the center, and the closest one in the middle part. The electrodes are separated from each other with a gentle curvature from the center plane toward the electrode ends. and,
With such a shape, the electric field strength between the main electrodes 4 and 5 is uniform at the center and gradually decreases toward the ends.

In addition, a plurality of spark discharge gaps (not shown) are arranged near the main electrode 4.5, and the laser gas between the main electrodes is heated by ultraviolet rays emitted from the spark discharge generated between the spark discharge gaps. It is designed to pre-ionize.

Furthermore, optical resonators (not shown) are provided at both ends of the main electrodes 4 and 5 in the longitudinal direction.

In the conventional pulse laser device configured as described above, when a high-speed high voltage pulse is applied between the main electrodes 4 and 5, a spark discharge is generated between the spark discharge gap and the main electrodes 4 and 5 are After pre-ionizing, the main electrodes 4, 5
A glow discharge occurs in between.

This glow discharge excites the laser gas, and due to the action of an optical resonator (not shown), a laser beam is generated in the installation direction of the optical resonator, but the intensity distribution of this laser beam affects the current distribution of the glow discharge. be done. This point will be explained below using FIG. 5. Figure 5 shows the cross-sectional shape (a), electric field strength distribution (b), and current distribution (C) of the main electrode half surface.
is normalized by a constant Yo (1/2 of the shortest distance between the main electrodes). That is, in (a) to (C), each X axis starts from the center of the main electrode and indicates the distance (X/Yo) in the width direction from this starting point. , 1/2 of the distance between the main electrodes is indicated by Y/Yo.

Among these, Fig. 5(b) shows the distribution of the electric field strength E between the main electrodes normalized by the central electric field strength between the main electrodes (point of X/Yo = 0): Emax. /E■a
Glow discharge does not occur in the range where the value of X drops to about 99% or less. Therefore, the current distribution of glow discharge becomes a distribution as shown in FIG. 5(c). FIG. 5(C) shows the distribution of the current I between the main electrodes normalized by the central current between the main electrodes (point of X=0): l1ax.

(Problem to be Solved by the Invention) However, in the conventional pulse laser device having the above configuration, the current distribution between the main electrodes is as shown in FIG.
As shown in C), the current gradually decreases from the center to the end (the direction where X/Yo is large), so the intensity distribution of the oscillated laser light also has a shape that corresponds to the current distribution. becomes.

Therefore, when a pulsed laser device is used as an amplifier and a -like intensity distribution of laser light is required, there is a problem that the space that can be used effectively is limited and the efficiency of using glow discharge decreases. Ta. In particular, in the case of a high-output laser that requires a large volume of oscillation space, the reduction in utilization efficiency becomes large, reducing the operating efficiency of the pulsed laser device.

Furthermore, when the current density of glow discharge is increased to increase the laser oscillation intensity, the current density in the center exceeds the allowable current density for stable glow discharge, the glow discharge contracts and becomes arc discharge, causing laser oscillation. There was a problem in that the maximum output of light was limited by the current density between the main electrodes.

As described above, in conventional pulsed laser devices, the current flowing between the main electrodes is maximum at the center of the main electrodes and decreases as it moves away from the center. There is a problem in that not only the unusable glow discharge space increases and the utilization efficiency of glow discharge decreases, but also the upper limit of the laser oscillation output is limited by the current density at the center of the main electrode.

The present invention was proposed in order to solve the problems of the prior art as described above, and its purpose is to make the current distribution between the main electrodes uniform, improve the utilization efficiency of glow discharge, and to The object of the present invention is to provide a high-output pulse laser device that can improve the limit value of the output intensity, which was limited by the current density of .

[Configuration of the Invention (Means for Solving the Problems) The pulse laser device of the present invention includes a spark discharge gap array arranged near a pair of opposing main electrodes, and pre-ionizes the main discharge space between the main electrodes. In a pulse laser device that
A feature is that the surface shape of the main electrode is composed of a plurality of function curves.

(Function) According to the pulsed laser device of the present invention, the surface shape of the main electrode is composed of a plurality of function curves, so that the current distribution between the main electrodes can be made uniform, so that the usage range of the glow discharge generation space is is expanded, and the limit value of the laser output intensity, which was limited by the current density at the center of the electrode, can be improved.

(Example) Hereinafter, one example of the pulse laser device according to the present invention will be described as a first example.
This will be explained in detail with reference to FIGS. 3 to 3.

First, FIG. 1 is an enlarged view showing the main electrode structure of the pulsed laser device of this embodiment. As shown in FIG. 1, a second main electrode 2 is disposed facing the first main electrode 1 in the laser gas, and the surface of each main electrode 1.2 is
According to the present invention, it is composed of two function curve shapes A and B. In this case, A and B are symmetrical with respect to the axis Y at the center of the main electrodes 1 and 2, and the main electrodes 1 and 2 have a gentle curvature from the center to the end of the electrode, and once After coming close to each other, the electrodes separate with a gentle curvature toward the end of the electrode.

Next, FIG. 2 is a circuit diagram showing the electrode part structure and excitation power supply circuit of a pulse laser device including the main electrode part of FIG. 1.

That is, the discharge part a is arranged in the laser gas, and a plurality of spark discharge gaps 3 are arranged on both sides of the first and second main electrodes 1 and 2, which are arranged opposite to each other, in a direction perpendicular to the plane of the paper.

Next, the configuration of the excitation power supply circuit shown in FIG. 2 will be explained below. First, a capacitor C2 is connected between the main electrodes 1 and 2 via a spark discharge gap 3. Also,
A capacitor C1 and a switch SI are connected to the discharge part a via a circuit inductance Ld including a residual inductance, and one end of this capacitor C1 is connected to a high voltage power supply Vc (not shown) via a resistor R, and the other end is connected to a high voltage power supply Vc (not shown) via a resistor R. The end is grounded via an inductance L.

Further, in FIG. 2, optical resonators (not shown) are provided at both ends of the main electrodes 1 and 2 in the longitudinal direction (perpendicular to the plane of the paper).
is installed.

The operation of the pulse laser device of this embodiment configured in this way will be described below. That is, the capacitor C1 is charged through the path of high voltage power supply Vc-resistance knee capacitor-inductance L.

Then, when switch S1 is closed, capacitor C1
A charged voltage is applied between the main electrodes 1.2. Moreover, since the voltage of the capacitor C1 is applied to the spark discharge gap 3 at this time, a part of the spark discharge gap 3 is discharged. Thereafter, all the spark discharge gaps 3 are discharged within a certain period of time, and the laser gas between the opposing main electrodes 1 and 2 is pre-ionized by the ultraviolet rays generated by this spark discharge.

When the spark discharge gap 3 is discharged in this way,
The charge on capacitor C1 moves to capacitor c2. As the voltage across the capacitor C2 rises, the voltage between the main electrodes 1 and 2 increases, and a glow discharge is ignited between the main electrodes 1 and 2.

Below, the generation situation of glow discharge will be explained with reference to FIG.

FIGS. 3(a) to 3(c) each show the cross-sectional shape, electric field strength distribution, and current distribution of the main electrode halves normalized by a constant Yo (1/2 of the shortest distance between the main electrodes). That is, in (a) to (C), each X axis starts from the center of the main electrode, and the distance in the width direction from this starting point (X
/Yo), and FIG. 3(a) shows 1/2 of the distance between the main electrodes as Y/Yo. In this example, the cross-sectional shapes on both the plus and minus sides in the X/Yo axis direction, that is, the left and right cross-sectional shapes centering on the Y/Yo axis, are symmetrical as described above, and the main electrode 1
, 2 have a gentle curvature from the center (X/Yo=0) toward the electrode end, and are once close to each other, and after being closest, have a gentle curvature toward the electrode end. and separated.

Among these, Fig. 3(b) shows the distribution of the electric field strength E between the main electrodes normalized by the electric field strength at the center between the main electrodes (point of X/Yo = 0): ll, gax. , unlike the conventional example shown in FIG.

The electric field strength is not maximum at the =00 point. That is,
In this example, as shown in FIG. 3(a), the closest point in the cross-sectional shape of the main electrode is not at the center, but at both sides of the center in the X/Y o-axis direction (the minus side is not shown). ), corresponding to the closest point between the main electrodes, there are two
Since the maximum electric field strength points exist at the two locations, glow discharge will occur around the two maximum electric field strength points. In this case, the current distribution of glow discharge becomes a distribution as shown in FIG. 3(C). FIG. 3(C) shows the distribution of the current I between the main electrodes normalized by the maximum current value: Imax. As shown in FIG. 3(C), the current reaches its maximum at the point where X/Yo=0, but when
．． It is held at almost the same high level up to point 5, after which
It will continue to decrease.

Similarly, on the negative side of the X/Yo-axis direction (not shown), from the point of X/Yo-0, almost X/Yo=
It is maintained at almost the same high level up to the points -1 and 5, and then decreases.

From the above, the electric field strength distribution is as shown in Figure 3(b).
It can be seen that the current does not reach its maximum at the point where /Yo=0, but the current reaches its maximum at the point where X/Yo=0, as shown in FIG. 3(c). The reason for this will be explained below. That is, since glow discharge generally occurs in a range where the value of E decreases to about 99%, from FIG. 3(b), X/Yo=
A gross discharge centered around 1 or around X/Yo=-1 will occur. Therefore, the positive side of the X axis (X
/ Y o≧O) and the negative side (X / Y.

≦0), so that each glow discharge generated centering around X/Yo=1 and X/Yo=-1 spreads to X/Yo<0 and X/Yo>0, respectively. If set to , at the center of the main electrode where X/Yo=0,
Since the glow discharge spreads from both the positive and negative sides of /Yo, the current can reach its maximum at the center of the main electrode.

In addition, since the intensity distribution of the oscillated laser light has a shape that corresponds to the current distribution, the central part of the electrode (where -1,5≦X
/ Yo≦1.5), the intensity distribution of the laser beam becomes flat at the center of the electrode. Therefore, when the pulsed laser device is used as an amplifier, a uniform intensity distribution of laser light can be obtained, the glow discharge space can be used effectively, and the usage efficiency can be increased. In particular, for high-output lasers that require a large volume of oscillation space, the improvement in utilization efficiency is remarkable.

Furthermore, even when the current density of glow discharge is increased to increase the laser oscillation intensity, in the device of this example, the current density at the center of the main electrode is flat, so that stable glow discharge can be generated. Since the glow discharge space can be used almost uniformly up to the current density, the allowable current density can be improved when evaluated as a whole. Therefore, the maximum output of laser light can be increased compared to the conventional example.

As described above, according to this embodiment, the current distribution flowing between the main electrodes becomes flat at the center of the main electrodes, and an oscillation region of various intensities can be obtained, so the glow discharge space used increases and the glow discharge This not only improves the efficiency of laser oscillation, but also increases the upper limit of laser oscillation output.

[Effects of the Invention] In the pulsed laser oscillation device of the present invention, the surface shape of the main electrode is composed of a plurality of function curves, so that the current distribution between the main electrodes can be made uniform, so that glow discharge does not occur. It is possible to provide an excellent high-output pulsed laser device that can expand the range of space available for use, and improve the limit value of laser output intensity that was limited by the current density at the center of the electrode.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional perspective view showing the main electrode structure in an embodiment of the pulse laser device of the present invention, and FIG. 2 is a circuit diagram showing the electrode structure and excitation power supply circuit of the pulse laser device in the same embodiment. Figures 3 (a) to (c) are curve diagrams showing the characteristics of the pulsed laser device of the same example, where (a) is the cross-sectional shape of the main electrode half surface, (b) is the electric field intensity distribution, and (C) is Current distribution, Fig. 4 is an enlarged cross-sectional perspective view showing the main electrode structure of a conventional pulsed laser device, and Fig. 5 is a curve diagram showing the characteristics of the conventional pulsed laser device. The cross-sectional shape, (b) shows the electric field strength distribution, and (C) shows the current distribution. 1.4... First main electrode, 2.5... Second main electrode, 3... Spark discharge gap. Fig. 71 First main telephone line xn. To N: Figure 3 Figure 3 Figure 3

Claims (1)

[Claims] A pulse laser device in which a spark discharge gap array is arranged near a pair of opposing main electrodes to pre-ionize a main discharge space between the main electrodes, wherein the main electrodes are formed from a plurality of function curves. 1. A pulsed laser device characterized by having a surface shape made up of: