JPH088386B2 - Discharge excited short pulse laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to various gases such as single or mixed gas of, for example, atoms, molecules and ions, metal vapor, vapor from volatile liquid, among lasers. The present invention relates to a discharge-excited short-pulse laser device that generates short-pulse laser light by performing excitation using the discharge of.

[Conventional technology]

FIG. 3 is an electric circuit diagram showing a conventional discharge-pumped short pulse laser device of this type. (1) is a capacitor for storing energy for main discharge, (2) is a peaking capacitor, and (3) is for charging. Inductance, (4) is a high voltage switch for starting discharge, such as a thyratron (a discharge tube containing hot cathode gas), (5) is the first main electrode arranged in the laser medium, and (6) is A second main electrode facing the first main electrode (5) at a predetermined interval,
(7) is the main discharge generated between both main electrodes (5) and (6),
(8) is a discharge gap for pre-ionization connected in series to the peaking capacitor (2), (9) is ultraviolet rays generated in the discharge gear (8), and (10) is a high voltage generator.

Since the conventional discharge-excited short pulse laser device of this type is constructed as described above, first, the capacitor (1) is charged with a high voltage through the inductance (3) for charging, and then the high voltage switch (4) is used. ) Is turned on,
A circuit including the capacitor (1), the peaking capacitor (2) and the high voltage switch (4) is formed, and the peaking capacitor (2) is pulse-charged at a high speed. And this peaking capacitor (2) is
And the second main electrodes (5) and (6) are connected in parallel, the charging of the peaking capacitor (2) proceeds and the first and second main electrodes (5) and (6) are connected. When the potential difference increases, the laser medium breaks down and the main discharge (7) occurs. Such a circuit is generally called a "capacitance transfer type circuit", and is well known as "LC inversion circuit". Widely used as a short-pulse laser device together with a "type circuit".

However, in a short pulse laser device such as a normal "TEACO ₂ laser" or an excimer laser (Excimer Laser), since the operating pressure is a high pressure of several atmospheres, the above-mentioned discharge is easily converged, and the laser output It tends to cause a decline. Therefore, in order to generate a spatially uniform main discharge as a means for coping with this, a method of performing preionization for evenly distributing the seeds of discharge by electrons in a region where the main discharge is generated in advance is used. Has been. In the above-mentioned conventional apparatus, the discharge gear (8) is inserted in series with the peaking capacitor (2), and pre-ionization is performed by the ultraviolet rays (9) generated in the discharge gear (8).

[Problems to be solved by the invention]

Since the amount of preionization in the conventional discharge-excited short-pulse laser device depends on the circuit for performing the main discharge as described above, it is difficult to adjust the time when the amount of preionization electrons becomes maximum. However, since a large amount of electric charge for generating the main discharge between the two main electrodes passes through the discharge gear, the discharge generated in this discharge gear becomes a strong spark discharge, which consumes energy and wears the electrode and impure gas. There is a drawback that causes the occurrence of.

The present invention has been made paying attention to the points according to the present invention, and provides a discharge-excited short pulse laser device that efficiently performs pre-ionization by a discharge gear and withstands long-term use.

[Means for solving problems]

The discharge-excited short-pulse laser device according to the present invention is provided with a preionization-dedicated circuit composed of a discharge gear for preionization, a high-voltage switch, a capacitor, and an inductance. The amount of current flowing can be adjusted.

[Action]

In the present invention, since the time when the amount of preionization electrons is maximized and the vibration cycle can be adjusted by the additional dedicated circuit for preionization, the amount of preionization electrons contributing to the occurrence of main discharge can be increased. , The uniformity can be improved, and only the minimum amount of electrons necessary for the main discharge to be generated is supplied, so that the efficiency of preionization is significantly improved, and the electrons passing through the discharge gap for preionization are not only significantly improved. Since the amount is small, long-term use is possible.

Example of Invention

FIG. 1 shows an embodiment of the present invention. However, the same reference numerals as those of the conventional one (FIG. 3) described above indicate the same constituent members, and the description thereof will be omitted.

(A) is a capacitor (12) for setting a time constant and an inductance (11) connected in series between the discharge gear (8) and the high voltage side, and an inductance (13) for charging the capacitor (12). It is a circuit for exclusive use of preionization for adjusting the vibration period formed by and.

Since the discharge excitation short pulse laser device of the present invention is configured as described above, first, the capacitor (1) is charged with a high voltage through the charging inductance (3), and then the high voltage switch (4). When "ON" is operated, a circuit consisting of the capacitor (1), the peaking capacitor (2) and the high voltage switch (4) is formed, and the peaking capacitor (2) is pulse-charged at a high speed.
At the same time that the voltage between the first and second main electrodes (5), (6) rises, the high voltage switch (4), the capacitor (12),
A circuit composed of an inductance (11) and a discharge gear (8), that is, a circuit for preionization (A) is formed,
The charge accumulated in the capacitor (12) causes discharge in the discharge gear (8) and also ultraviolet rays (9) to perform preionization.

Next, FIGS. 2 (A), (B), and (C) are explanatory diagrams of the operation of the apparatus. First, FIG. 2 (A) shows changes in voltage between the main electrodes (5) and (6). However, the voltage rises in about 100 ns, and then the voltage drops sharply due to the dielectric breakdown of the laser medium. Further, FIG. 2 (B) shows a change in current flowing through the peaking capacitor (2), which shows a state in which a current of 10 KA flows when the capacitor is charged and a current of 20 to 30 KA flows in the opposite direction when the capacitor is discharged. In the case of the conventional device, this current flows through the discharge gap (8) for pre-ionization as it is, so that the above-mentioned problem occurs. Furthermore, FIG. 2 (C)
Indicates the change in the current flowing through the discharge gear (8). By reducing the capacity of the capacitor (12),
Compared with the waveform shown in FIG. 2 (A), the oscillation cycle is shorter and the peak value of the current can be suppressed to a low level. Even if the peak value of the current becomes 1/3 or less, sufficient preionization is performed. Therefore, a uniform main discharge can be generated.

In addition, in the above-described embodiment, the case where the strong discharge is generated in the vicinity of the main discharge to perform the pre-ionization has been described. However, if another capacitor is connected in series to the discharge gear (8). Further, the peak value of the current can be further reduced, which is further effective. In the above-described embodiment, the case where the capacitor (12) and the inductance (11) connected in series are inserted between the discharge gear (8) and the high voltage side has been described. If (8) and the high voltage side are connected by a pulse forming line such as a coaxial cable, the current rises sharply and the time until the current rises can be set arbitrarily. The efficiency of preliminary ionization is further improved.

〔The invention's effect〕

As described above, according to the present invention, the preionization-dedicated circuit including the preionization discharge gear, the high-voltage switch, the capacitor, and the inductance is added to the discharge excitation short pulse laser device. Since the time until the amount of preionized electrons becomes maximum and the vibration cycle can be adjusted, the amount of preionized electrons contributing to the occurrence of main discharge can be increased and the uniformity can be improved. Also, since only the minimum amount of electrons required to generate the main discharge is supplied, not only the efficiency of preionization is significantly improved, but also the amount of electrons passing through the discharge gap for performing preionization is reduced, which results in long-term use. It has a possible excellent effect.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2 (A), (B), and (C) are explanatory diagrams of its operation, and FIG. 3 is an electric diagram showing a conventional discharge-pumped short-pulse laser device. It is a circuit diagram. In the figure, (1) is a capacitor for storing the energy of main discharge, (2) is a peaking capacitor, (4) is a high voltage switch for starting discharge, (5) is a first main electrode,
(6) is the second main electrode, (7) is the main discharge, (8) is the discharge gear, (11) is the inductance for setting the time constant,
(12) is a capacitor for setting the time constant. The same reference numerals in the drawings indicate the same or corresponding parts.

Front page continuation (72) Inventor Takeo Haruta 8-1-1 Tsukaguchihonmachi, Amagasaki City, Hyogo Sanryo Electric Co., Ltd. Applied Equipment Research Laboratory (72) Inventor Haruhiko Nagai 8-1-1 Tsukaguchihonmachi, Amagasaki City, Hyogo Prefecture No. Sanryo Electric Co., Ltd. Applied Equipment Laboratory (56) Reference JP-A-61-31893 (JP, A)

Claims (2)

[Claims] 1. A first device facing each other in a laser medium.
In a discharge-excited short-pulse laser device having a main discharge circuit including a second main electrode, a capacitor for storing energy for main discharge, a peaking capacitor, and a high-voltage switch for starting discharge, Separately from the circuit, a dedicated ionization circuit for preionization consisting of a discharge gap for preionization, the high-voltage switch, a capacitor, and an inductance is added so that the time constant of this circuit and the amount of current flowing through it can be adjusted. Discharge-pumped short pulse laser device characterized in that 2. The high voltage side of the discharge starting switch and the auxiliary electrode are connected by a pulse forming line such as a coaxial cable whose length can be selected. The discharge-excited short pulse laser device described.