JPH02116183A - Pulse laser oscillator - Google Patents

Abstract

PURPOSE:To enable stable laser oscillation by changing the size of a circuit element of a magnetic compression circuit in accordance with a peripheral temperature. CONSTITUTION:In a capacitor which constitutes a magnetic compression circuit, capacitors C3', C3'', and C4', C4'', and C5', C5'' are connected in series, respectively. The capacity of capacitors C3' to C5' increases together with the temperature in the same manner as the temperature characteristic 19'. The capacity of capacitors C3'' to C5'' reduces together with the capacity in the same manner as the temperature characteristic 19''. According to this constitution, even if a peripheral temperature rises, a capacitor capacity does not change equivalently in each loop; therefore, a frequency of each loop at operation time does not change, thus enabling operation at constantly the same state. Operation state of a laser becomes fixed continuously and stable laser oscillation can be acquired in this way.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a high-output pulse laser oscillation device, and in particular, to stabilizing the operation of its magnetic pulse compression circuit and stabilizing the laser output. This is what we aim to do.

(Prior technology) In recent years, high output TEA, TEMA-CO2 laser, etc.
Various types of pulsed lasers, such as excimer lasers and copper vapor lasers, are being considered for industrial use.

These lasers are now required to have high speed, large current, and pulsed power. In such a power supply, the power burden of the switch element that opens and closes a large current is extremely large, so in many cases, the switch elements currently used, such as thyratrons and thyristors, are unable to open and close the power supply. Also,
Pulsed lasers have a small operation delay time (several tens of n5eC
(below) and long life (approximately 108 shots or more), there are almost no switching elements that are of practical use.

Therefore, recently, by adding a pulse compression circuit to reduce the power burden on the switching element, high speed, large current,
Attempts have been made to realize a high-output pulse power source, and a magnetic pulse compression circuit is a typical example. This magnetic pulse compression circuit utilizes the saturation of magnetization of a ferromagnetic material such as an iron core. (For example, Japanese
Journal of Applied Physics
Vol, Na1l, 1985. ppL855-
L857゜"Pulsed CO2La5er P
pumped by an All 5 solid
Figure 6 shows an example of such a magnetic pulse compression circuit.

In FIG. 6, a charging power source 1 is connected to a first capacitor 3 via a charging resistor 2, and a second capacitor 3 is connected to the first capacitor 3. A third capacitor 4.5 is connected in parallel. 1st. A first saturable reactor 6 is connected in series between the second capacitor 3 and the second capacitor. A second saturable reactor 7 is connected in series between the third capacitors 4 and 5. A third saturable reactor 8 is connected in series to the third capacitor 5, and a laser discharge section 9 is connected in parallel through this. With the above configuration, the first stage loop from the first capacitor 3 to the second capacitor 4 via the first saturable reactor 6, and the loop from the second capacitor 4 to the second saturable reactor 7 A second stage loop leading from the third capacitor 5 to the third capacitor 5 and a third stage loop leading from the third capacitor 5 to the laser discharge section 9 through the third saturable reactor 8 are formed. There is. Further, a switch 10 is provided between the first capacitor 3 and the first saturable reactor 6 so that it can be opened and closed. The operation of the circuit of FIG. 6 having such a configuration is as follows.

First, the first capacitor 3 is charged from the charging power source 1 via the charging resistor 2. When the switch 10 is turned on here, the voltage between the electrodes of the first capacitor 3 is applied to the series circuit of the first saturable reactor 6 and the second capacitor 4. At this time, no charge is stored in the second capacitor 4;
Since the voltage between the electrodes of the second capacitor 4 is almost zero, almost the entire voltage between the electrodes of the first capacitor 3 is applied between the electrodes of the first saturable reactor 6, and as a result, the voltage between the electrodes of the first saturable reactor 6 A small current 12 flows between the poles of 6.

This current 12 excites the first saturable reactor 6,
Above a certain value, the magnetic flux density in the iron core of the first saturable reactor 6 exceeds the saturation magnetic flux density, and the first saturable reactor 6 becomes saturated. Then, since the inductance of the first saturable reactor 6 rapidly decreases, a current 12 flows from the first capacitor 3 through the saturated first saturable reactor 6, charging the second capacitor 4. .

Here, the frequency of the current 12 flowing through the first stage loop is:
It is almost determined by the capacitance value of the first capacitor 3, the inductance value of the first saturable reactor 6 at saturation, and the capacitance value of the second capacitor 4. Next, the second capacitor 4
As the voltage between the electrodes increases, a voltage is applied between the electrodes of the second saturable reactor 7, and the current 13 flows through the second saturable reactor 7, reaching saturation. At this time, the charge on the second capacitor 4 is transferred to the third capacitor 5. Third
The operation of the saturable reactor 8 is also similar.

Here, in order to sequentially increase the frequency of the current 12-14 in each stage flowing through each saturable reactor 6-7, first, second, and so on are used. A method is used to sequentially reduce the inductance of the third saturable reactor 6-8 during non-saturation and saturation. Furthermore, in order to efficiently transmit the energy stored in each capacitor to the subsequent capacitor, a method is used in which the capacitance of each stage is made equal and the values of the saturable reactors 12-14 are successively reduced. In this method, the voltage of the loop in each stage is constant, and the peak value of the current 12-14 flowing through the loop in each stage is sequentially amplified as shown in FIGS. 7(A) to 7(C), and the frequency is raised. I'm getting beaten up. and,
The current 14 of the final stage loop compressed by the magnetic pulse flows to the laser discharge section 9, which is a load, and causes laser oscillation. The operation process of saturation and non-saturation of the saturable reactor described above will now be explained with reference to FIG. In addition, FIG. 8 is a graph showing the magnetization curve of the iron core that constitutes the saturable reactor.

First, when an exciting current flows from the capacitor at the front stage of the saturable reactor, the operating point of the iron core of the saturable reactor moves from the center point 0 in FIG. 8 toward the 0 point. When the operating point reaches zero due to the excitation current, the magnetic flux density within the iron core of the saturable reactor becomes equal to or higher than the saturation magnetic flux density, and the saturable reactor enters a saturated state. At this time, since the inductance of the saturable reactor rapidly decreases, current flows from the preceding stage capacitor through the saturated saturable reactor to the succeeding stage capacitor, charging it. In this way, when the saturable reactor is saturated, the operating point of the iron core is at a point where the magnetizing force H is much larger than the 0 point, but as the current decreases, it moves to the side where the magnetizing force H is small, and reaches point ■. The iron core changes from a saturated state to an unsaturated state. At this time, since the inductance of the saturable reactor increases rapidly, the current flowing through the saturable reactor decreases rapidly. When the current becomes zero after half a cycle, the operating point becomes point ■, where it stops and residual magnetism remains.

By the way, if the switch 10 is turned on again with the operating point of the iron core at point ■, the operating point of the iron core moves in the direction from ■ to ■, but since the amount of change in magnetic flux in this case is small, The inductance of the saturation reactor becomes sufficiently large that magnetic pulse compression becomes almost impossible. Therefore, after magnetic pulse compression has been performed, a so-called magnetic reset is performed in which the operating point of the iron core is returned from the 0 point in Figure 8 to the center point 0 point again through the fish, and the same level of magnetic field is restored again. It allows for pulse compression. That is, the conventional circuit is provided with a reset device for performing the above-described magnetic reset, as shown at 16-1.8 in FIG. There are several methods for magnetic reset, but the simplest one is to flow a direct current in the opposite direction so that the operating point of the iron core becomes zero. According to this method of flowing direct current, the operating point of the iron core becomes ■ after performing the magnetic pulse compression operation, but if you perform the next magnetic pulse compression operation in this state, the magnetic flux change can be larger than when starting from 0 point. This method is used because it can achieve a high compression ratio.

(Problems to be Solved by the Invention) Generally, elements constituting an electric circuit experience a small amount of power loss during operation. The magnetic pulse compression circuit of a pulsed laser is no exception, and there is some power loss, which may result in a rise in the temperature of the circuit elements themselves. When the temperature rises, the dielectric constant of some of the dielectric materials used in the capacitor changes, which may cause the following problems.

For example, if the capacitance of a capacitor decreases as the temperature rises, the current frequency of each loop in the magnetic pulse compression circuit will increase as described above, causing the circuit state to differ from the initial state. There was a risk that the operation timing of the saturation reactor would be shifted. Furthermore, if the degree of temperature rise differs from stage to stage, energy transmission loss becomes large, which may impede the operation of the laser.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly stable, high-output pulse laser oscillation device that is equipped with a magnetic pulse compression circuit that does not cause the problems caused by temperature increases as described above.

[Structure of the invention]

(Means and actions for solving the problems) As a result of analyzing the technical problems described above, in order to solve these problems, it is necessary to prevent changes in the values of circuit elements due to temperature rise caused by power loss in the magnetic pulse compression circuit. Should we suppress the value, compensate for the change in value with changes in other elements, or change the operating conditions of the circuit?

It has also been found that it is necessary to suppress the temperature rise itself.

(Example) Specific examples of the present invention will be described below.

FIG. 1(A) is a circuit diagram of the example, and FIG. 1(B) is a chart explaining the temperature characteristics of the capacitor used in the example. In this embodiment, the capacitors used in each part of the device in FIG. As shown in Figure 1 (B), the capacity increases with temperature 19', and the other 3'
, 4', and 5' are a combination of 19' whose capacity decreases with temperature. Since the circuit operation itself is basically the same as that described in the description of the prior art, details will be omitted here.

When the magnetic pulse compression circuit is configured in this way, the capacitor capacity in each loop does not change even if the surrounding temperature rises, so the frequency of each loop when the magnetic pulse compression circuit operates is set to the initially set value. It is possible to always operate in the same state without changing.

Therefore, it can be seen that the operating condition of the laser is always constant and stable laser oscillation can be obtained.

Figure 2 (A) is a circuit diagram of the second example, Figure 2 (B) is a chart explaining the temperature characteristics of the inductance element used in the example, and Figure 2 (C) is a diagram of a specific inductance element. In this embodiment, which is an example of a configuration example, Fig. 2 (A)
The saturable reactor used in each part of the device has variable inductances additionally connected in series, and the inductances 6', 7', and 8' are the second
As shown in Figure (B), the value increases with temperature (20). Since the circuit operation itself is basically the same as that described in the description of the prior art, details will be omitted here. The specific structure of the inductance element shown in FIG. 2(C) is that both ends of an inductance element 21 made to be expandable and contractible are fixed by members 22 made of, for example, a bimetal-like material that expands and contracts depending on the temperature. The length of can be freely changed depending on the temperature. When the length of the inductance changes, the cross magnetic flux of the coils forming the inductance changes, and the value of the inductance changes.

If the magnetic pulse compression circuit is configured in this way, even if the surrounding temperature rises, the inductance value will change in each loop by the portion where the capacitance changes, and as a result, when the magnetic pulse compression circuit operates, The frequency of each loop remains at the initially set value and does not change, making it possible to always operate in the same state.

Therefore, it can be seen that the operating condition of the laser is always constant and stable laser oscillation can be obtained.

FIG. 3(A) is a circuit diagram of the third embodiment, and FIG. 3(B) is a graph showing the magnetization characteristic curve of the iron core constituting the saturable reactor used in the embodiment. In this example, the circuits 16, 17, and 18 for resetting the saturable reactors used in each part of the device in Fig. 3 (A) can vary the output current and increase the current value in accordance with the rise in ambient temperature. It is configured to do so. Since the circuit operation itself is basically the same as that described in the description of the prior art, details will be omitted here.

In FIG. 3(B), when the reset current 12 increases and becomes the reset current 12', the operating point of the saturable reactor becomes ■
Move from to ■′. During the operation of the magnetic pulse compression circuit, the saturable reactor is saturated after passing from ■ to ■ and operates, but by changing the starting ■ to ■', the operation time can be slowed down. When configuring a magnetic pulse compression circuit in this way, the surrounding temperature rises and the capacitance of each loop decreases, causing the operation time of the loops to change significantly, but it can be operated by adjusting the reset current. It turns out that you can adjust the time. As a result, the operating time of each loop during operation of the magnetic pulse compression circuit remains at the initially set value and does not change, making it possible to always operate in the same state.

Therefore, it can be seen that the operating condition of the laser is always constant and stable laser oscillation can be obtained.

A fourth embodiment is shown in FIG. In this embodiment, the entire magnetic pulse compression circuit is housed in a tank 24 filled with cooling insulating oil 23. The insulating oil 23 is forcibly circulated by an oil circulation pump 25, and the heat generated in the magnetic pulse compression circuit is processed by a heat exchanger 26 to cool the insulating oil. Since the circuit operation itself is basically the same as that described in the description of the prior art, details will be omitted here.

Further, in the fifth specific embodiment of the present invention, the effect of the present invention can be further ensured by taking out the lead-out terminal from the tank 24 with a bushing 27 as shown in FIG.

If the magnetic pulse compression circuit is placed in oil and cooled in this way, even if the temperature rises due to power loss, it will be cooled down immediately, so there will be no change in the capacitor capacity etc. in each loop. The loop frequency remains at the initially set value and does not change, making it possible to always operate in the same state.

Therefore, it can be seen that the operating condition of the laser is always constant and stable laser oscillation can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, in a pulsed laser oscillation device, the operation of the magnetic pulse compression circuit can be stabilized, and the laser output can be stabilized.

[Brief explanation of the drawing]

FIG. 1(A) is a circuit diagram of the first embodiment, FIG. 1(B) is a chart explaining the temperature characteristics of the capacitor used in the first embodiment, and FIG. 2(A) is a diagram of the second embodiment. Example circuit diagram,
FIG. 2(B) is a chart explaining the temperature characteristics of the inductance element used in the second embodiment, FIG. 2(C) is a perspective view showing an example of a specific inductance configuration,
FIG. 3(A) is a circuit diagram of the third embodiment, FIG. 3(B) is a graph showing the magnetization characteristic curve of the iron core constituting the saturable reactor used in the third embodiment, and FIG. 4 is a front view showing the fifth embodiment, FIG. 5 is a front view showing the fifth embodiment, and FIG. 6 → is a front view showing the conventional magnetic pulse compression circuit.
（＾）、 （９ん、こC）Route map, No.→Fig.←h→→
〒-〒 is a characteristic diagram showing the operation of the magnetic pulse compression circuit, and 〒-〇 is a graph showing the magnetization curve of the iron core constituting the saturable reactor. 1... Charging power source 2... Charging resistor 3... First capacitor 4... Second capacitor 5... Third capacitor 6... First saturable reactor 7... Second saturable reactor 8...Third saturable reactor 9...Laser discharge section 10...Switches 12, 13.14...Current

Claims (1)

[Claims] A capacitor and the current input from this capacitor,
A pulsed laser oscillator having a magnetic pulse compression circuit comprising a saturable reactor that compresses the time width and outputs the pulse, characterized in that the size of the circuit elements of the magnetic compression circuit is changed according to the surrounding temperature. Pulsed laser oscillation device.