JPH0754865B2 - 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 such as atoms and molecular ions, metal vapor, vapor from volatile liquid, among lasers. Excitation is performed using discharge,
The present invention particularly relates to an excitation circuit of a discharge-excited short-pulse laser device that generates short-pulse laser light.

[Conventional technology]

FIG. 3 is an electric circuit diagram showing a conventional discharge excitation short pulse laser device of this type, and FIGS. 2 (A), (B) and (C) are explanatory diagrams of its operation. In FIG. 3, (1) is a capacitor that stores energy for main discharge, (2) is a peaking capacitor, (3) is a charging inductance, and (4) is, for example, a thyratron (a discharge tube containing hot cathode gas). A high-voltage switch for starting discharge, consisting of, etc., (5) is arranged in the laser medium (10), the first main electrode having the laser optical axis direction as the longitudinal direction, and (6) is this first main electrode. Electrode (5)
A second one having a plurality of openings and facing each other at a predetermined interval.
Main electrode (7) is a dielectric material sandwiched between the second main electrode (6) and the auxiliary electrode (8),
(9) is a high voltage generator.

Since this kind of conventional discharge excitation short pulse laser device 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 ) Is turned on,
A circuit composed 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. Since the peaking capacitor (2) is connected in parallel with the first and second main electrodes (5) and (6), charging of the peaking capacitor (2) proceeds and the peaking capacitor When the potential difference between the main electrodes (5) and (6) becomes large, the laser medium undergoes dielectric breakdown and discharge is generated. Such a circuit is generally called a "capacitance transfer type circuit". It is widely used as a short pulse laser device together with the conventionally known "LC inversion circuit".

However, in a short pulse laser device such as a normal "TEACO ₂ laser" or an excimer laser (Excimer Laser), the operating pressure is a high pressure of several atmospheres, so the above-mentioned discharge easily converges, and the laser output decreases. As a means for coping with this, in order to generate a spatially uniform main discharge, pre-ionization is performed in advance to uniformly disperse the seeds of the electric discharge in the region where the main discharge occurs. Method is used. In the above-mentioned conventional device, the second main electrode (6) having a plurality of openings and the auxiliary electrode (8) are superposed with the dielectric (7) in a sandwich form to form a capacitor, Since the peaking capacitor (2) is connected in parallel, when the high voltage switch (4) is turned "ON", the voltage across the peaking capacitor (2), that is, the second main electrode (6),
The voltage between the auxiliary electrodes (8) rises as shown in FIG. 2 (A). Meanwhile, the peaking capacitor (2) and the second
The current of the waveform shown in FIG. 2B for charging the capacitor formed by the main electrode (6) and the auxiliary electrode (8) flows from the capacitor (1). The speed at which this current flows is determined by the combined capacitance of the capacitor formed by the capacitor (1) and the peaking capacitor (2), the second main electrode (6) and the auxiliary electrode (8),
It depends on the stray inductance in the circuit and rises in 50 to 100 ns as shown in FIG. And
In the opening of the second main electrode (6), creeping discharge occurs due to the above-mentioned charging current, and pre-ionization is performed by this discharge.

[Problems to be solved by the invention]

Since the preionization in the conventional discharge-excited short-pulse laser device depends on the circuit for performing the main discharge as described above, it is not only difficult to adjust the time when the amount of the preionization electrons becomes maximum. Since the electrons generated by the preionization disappear, the proportion of the electrons generated by the preionization that are actually used for the main discharge is small, and the preionization is performed only once. The distribution of the pre-ionized electrons is also likely to be non-uniform, resulting in poor uniformity of the main discharge and a reduction in laser output.

The present invention has been made paying attention to such a point, and not only can the timing when the amount of preionized electrons is maximized be adjusted, but also stable by repeating preionization until main discharge occurs. An object of the present invention is to provide a discharge-excited short pulse laser device that can obtain a main discharge.

[Means for solving problems]

The discharge excitation short pulse laser device according to the present invention is dedicated to preionization separately from the main discharge circuit by the auxiliary electrode, the dielectric, the second main electrode, the high voltage switch for starting the discharge, and the inductance and capacitor for setting the time constant. By constructing a circuit and appropriately setting the time constant of this circuit, the time until the amount of preionization electrons becomes maximum and the vibration cycle can be adjusted.

[Action]

In this generation, the time until the amount of preionized electrons becomes maximum and the vibration cycle can be adjusted, so that the amount of preionized electrons contributing to the occurrence of main discharge is increased and the uniformity improves the main discharge. The uniformity is remarkably improved, and as a result, the laser output can be increased and stabilized.

Example of Invention

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

(A) is a circuit dedicated to preionization for vibration period adjustment formed by a time constant setting inductance (11) and a capacitor (12) which are directly connected to each other, and (13) is the time constant setting capacitor (12) ) And the auxiliary electrode (8).

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 composed 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 as the voltage between the two main electrodes (5) and (6) rises, the inductance (11) and capacitor (12) for setting the time constant, the auxiliary electrode (8), the dielectric (7),
A circuit composed of the second main electrode (6) and the high-voltage switch (4), that is, a circuit for exclusive use of preionization (A) is also formed, and a time constant setting capacitor (12) and the second main electrode (6). −
The charges accumulated in the capacitor composed of the dielectric (7) -auxiliary electrode (8) are discharged to cause creeping discharge in the plurality of openings of the second main electrode (6), resulting in pre-ionization. Has been done.

Now, assuming that the capacitance accumulated in the dedicated circuit for preionization (A) is C and the total of the inductances is L, the vibration period thereof is 2π ▲ √ ▼.

Generally, the amount of charge required for preionization may be about 1% of the amount of charge required for main discharge, so C can be selected small, and the oscillation cycle of the dedicated preionization circuit (A) is the same as that of the main discharge circuit. It is also possible to set it to 1/10 or less of the vibration period. In the above-described embodiment, as shown in FIG. 2 (C), the preliminary ionization is performed twice before the main discharge occurs, By improving the uniformity, the transfer of the main discharge to the arc is suppressed, and a uniform main discharge is generated.

In the above-described embodiment, the time for setting the time constant setting inductance (11) and the capacitor (12) in the preionization-dedicated circuit (A) until the preionization electron amount becomes maximum, and the vibration. The case where the period is adjusted has been described, but as shown in FIG. 4, the high voltage switch (4)
If the pulse forming line (14) such as a coaxial cable is connected between the high-voltage side of the electrode and the auxiliary electrode (8), the same can be achieved by selecting the length of the pulse forming line (14). Can be adjusted to obtain a sharp rising current pulse. further,
If, for example, a magnetic saturation switch is used as the inductance (11) for setting the time constant, the timing at which preionization starts due to a large inductance before saturation can be adjusted, and the creeping discharge current begins to increase. Then, the maximum value of the amount of preionization electrons can be increased in order to saturate and reduce the inductance and promote the increase in current. Furthermore, if the intermediate point (13) between the time constant setting capacitor (12) and the auxiliary electrode (8) and the ground are connected with high resistance or high inductance, the auxiliary electrode (8 ) And the second
It is possible to apply only the voltage changing portion between the main electrodes (6), and the same effect can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the auxiliary ionization dedicated circuit is provided separately from the main discharge circuit by the auxiliary electrode, the dielectric, the second main electrode, the high voltage switch for starting the discharge, and the inductance and the capacitor for setting the time constant. Since I configured
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 is increased, and the uniformity of main discharge is significantly improved by improving the uniformity. However, the laser output can be increased and stabilized, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is an electric 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 circuit showing a conventional discharge excitation short pulse laser device. 4 and 5 are electric circuit diagrams showing another embodiment of the present invention. In the figure, (1) is a capacitor for storing 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 dielectric, (8) is the auxiliary electrode, (10) is the laser medium, (11) is the inductance for setting the time constant, and (12) is for setting the time constant. Capacitors,
(14) is a pulse forming line. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeo Haruta, 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Sanryu Electric Co., Ltd. Applied Equipment Research Laboratory (72) Haruhiko Nagai 8-chome, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. 1-1 Sanryo Electric Co., Ltd. Applied Equipment Research Laboratory

Claims (4)

[Claims] 1. A first device facing each other in a laser medium.
And a second main electrode, an auxiliary electrode superposed on the second main electrode via a dielectric, a capacitor for storing energy for main discharge, one end of the capacitor and the other end of the second main electrode. A discharge starting high voltage switch connected to the main electrode of the above, and a time constant setting inductance and time constant setting capacitor connected between the auxiliary electrode and the one end of the high voltage switch. The auxiliary electrode, the dielectric, the second main electrode, the high voltage switch, the inductance for setting the time constant and the capacitor for setting the time constant constitute a dedicated preionization circuit separately from the main discharge circuit, and the preionization electron amount A discharge-excited short pulse laser device characterized in that the time until the maximum value and the oscillation period can be adjusted. 2. A discharge excitation short pulse laser device according to claim 1, wherein a magnetic saturation switch is used as an inductance for setting a time constant. 3. The high voltage side of the high voltage switch for starting the discharge 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 according to the item 1. 4. An intermediate point between a capacitor for setting a time constant and an auxiliary electrode and a ground are connected with a high resistance or a high inductance, and a change amount of a voltage between the auxiliary electrode and the second main electrode is connected. The discharge-excited short-pulse laser device according to claim 1, characterized in that it is applied only.