JP2996706B2 - Pulse laser oscillation device - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to a pulse laser oscillation device, and more particularly to a pulse laser oscillation device having an improved discharge section and power supply configuration. is there.

(Prior art) In a discharge-excitation type gas laser device, a laser oscillation is obtained by generating a spatially uniform glow discharge in a laser gas. However, a pulse such as a transverse excitation pulse CO ₂ laser or an excimer laser is used. In the laser oscillation device, since the laser gas pressure is equal to or higher than the atmospheric pressure and further contains a gas component having a strong electron-adhering property, it is difficult to uniformly turn on the glow discharge. For this reason, it is general that pre-ionization is performed prior to glow discharge ignition, and a high-speed pulse voltage is applied to the discharge unit to form a glow discharge.

FIG. 3 is a diagram showing an example of a discharge section configuration and an excitation power supply circuit of a conventional pulse laser oscillation device. That is, a pair of main electrodes 1 and 2 are arranged to face each other, and a space surrounded by the main electrodes 1 and 2 is filled with a laser gas. The main electrode 2 is grounded. On the other hand, a preionization electrode 3a is connected to the main electrode 1, and both are electrically at the same potential. The preliminary ionization electrode 3a and the preliminary ionization electrode 3b are disposed to face each other in the laser gas via the gap 4. Further, the preliminary ionization electrode 3b is electrically insulated from the conductor that mechanically supports the main electrode 1, is extracted from the laser gas, and is connected to the capacitor Cs5. Further, one end of the charging inductance 6 is commonly connected to the preliminary ionization electrode 3b and the capacitor Cs5, and the other end is grounded. Also, the capacitor Cs5
Are grounded via a switch 7 and connected to a high voltage power supply HV9 via a charging resistor 8. In addition, the main electrode
A capacitor Cb10 is connected between 1 and 2. One or more of these capacitors and inductances are connected in parallel. An optical resonator (not shown) is provided in a direction perpendicular to the plane of the drawing.

The conventional pulsed laser oscillator configured as above is
It operates as described below. That is, in the initial state, the switch 7 is open, and the capacitor Cs5 is charged through the path of the high voltage power supply HV9, the charging resistor 8, the capacitor Cs5, the charging inductance 6, and the ground. On the other hand, since the capacitor Cb10 is not charged, the main electrode 1 is at the ground potential. Next, when the switch 7 is closed,
Since the potential of the capacitor Cs5 on the switch 7 side is the ground potential, the potential of the capacitor Cs5 on the side of the pre-ionization electrode 3b is applied to the pre-ionization electrode 3b with a polarity opposite to the polarity charged in the capacitor Cs5. On the other hand, since the preliminary ionization electrode 3a is at the ground potential, a high potential is applied to the gap 4, and a spark discharge occurs in the gap 4. The laser gas between the main electrodes 1 and 2 is pre-ionized by the ultraviolet light generated by the spark discharge. Further, the electric charge stored in the capacitor Cs5 flows through a path of the switch 7, the capacitor Cs5, the preliminary ionization electrode 3b, the gap 4, the preliminary ionization electrode 3a, the main electrode 1 and the capacitor Cb10, and the capacitor Cb10 is charged. When the voltage of the capacitor Cb10 increases in this way and the voltage applied between the main electrodes 1 and 2 reaches or exceeds the discharge breakdown voltage of the laser gas,
A glow discharge 11 is formed between the main electrodes 1 and 2, the laser gas is excited, and a laser beam is emitted in a direction perpendicular to the plane of the drawing by the action of an optical resonator (not shown).

(Problems to be Solved by the Invention) In the conventional pulse laser oscillation device as described above, the charging voltage of the capacitor Cs5 is set to several tens of kV or more, and the speed of charging the capacitor Cb10 is increased. It is necessary to shorten the time interval between the time when the preionization discharge is formed and the time when the glow discharge 11 is formed. For this reason, the maximum value of the current flowing through the switch 7 and the rate of change with time are extremely large, and not only are the types of switches that can be used limited, but also the life of the switch 7 is shortened. Also, the charging voltage could not be increased beyond the maximum allowable current and the allowable current change rate determined by the characteristics of the switch 7.

As described above, since the operation range and types of switches that can be used are limited, it has been difficult to realize an operation operation required for industrial applications such as a repetitive operation and a long life operation. The discharge starting voltage of the glow discharge 11 is
Since it is determined by the charging rate and voltage of Cb10, it was practically impossible to control the discharge injection energy by the discharge starting voltage. In particular, in the case of an excimer laser, since the discharge impedance is low and only the energy stored in the capacitor Cb10 can be used for oscillation, the oscillation efficiency is increased by controlling the discharge starting voltage, and the entire energy stored in the capacitor Ca5 is effectively used. The development of a pulsed laser oscillation device capable of performing the above has been eagerly desired.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned drawbacks of the prior art, and its object is to greatly reduce the operation duty of a switch, widen the selection range of a switch, and increase the laser oscillation efficiency. To provide a highly efficient, long-life pulsed laser oscillation device.

[Structure of the Invention] (Means for Solving the Problems) The pulse laser oscillation device of the present invention divides a capacitor connected between main electrodes into a first capacitor and a second capacitor of equal capacity. And connect them in series,
In addition, the connection point is grounded, and the first capacitor and the second capacitor are respectively connected to the secondary windings of two series of transformers having opposite polarities, and a third winding is connected to the primary winding of the transformer. A device for connecting a capacitor and a switch to form a closed circuit, connecting the third capacitor to a DC power supply, and further irradiating short-wavelength light between the main electrodes whose voltage is gradually raised. Is provided outside between the main electrodes.

(Operation) According to the pulse laser oscillation device of the present invention, the energy to be supplied to the glow discharge can be supplied from the capacitor charged by the low-speed pulse, so that the operation duty of the switch element can be greatly reduced. In addition, since the voltage applied to the discharge portion has the opposite polarity of positive and negative, the discharge breakdown voltage increases, and the discharge start time can be controlled by the action of the short wavelength light source installed outside the main electrode. Glow discharge can be generated in a stable state by the low-speed charging voltage pulse, and the oscillation efficiency can be improved.

(Embodiment) An embodiment of the present invention will be specifically described below with reference to FIGS. 1 and 2. The same members as those of the conventional type shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, as shown in FIG. 1, the pair of main electrodes 1 and 2 are disposed to face each other in an airtight container filled with laser gas, and the surfaces of the main electrodes 1 and 2 that are in contact with the laser gas. Have the same shape. The main electrode 1 is formed in a U-shaped cross section, and a device 20 (for example, an X-ray source) for irradiating short-wavelength light is provided between the main electrodes on the back side. Further, a first capacitor having an equal capacity is provided between the main electrodes 1 and 2.
The capacitor Cpa22 and the second capacitor Cpb23 are connected in series, and a connection point between both capacitors is provided. On the other hand, the high-voltage power supply HVA12 is connected to the third capacitor Cd24 via the charging resistor 8, and the third capacitor Cd24 forms a closed circuit from the switch 7 and the primary winding 26 of the transformer 25. The secondary winding of the transformer 25 is composed of a first secondary winding 27a and a second secondary winding 27b having opposite polarities, and a connection point between the two is grounded. The first capacitor Cpa22 and the first secondary winding 27a and the second capacitor Cpb23 and the second secondary winding 27b form a closed circuit via the ground. One or more of the above-mentioned capacitors, resistors and inductances are connected in parallel.

The pulse laser oscillation device of this embodiment having such a structure operates as described below. That is, in the initial state, the switch 7 is open, and the high voltage power supply HVA12-the charging resistor 8
-Third capacitor Cd24-In the path of ground, the third capacitor Cd24 is charged. On the other hand, the first capacitor Cp
Since a22 and the second capacitor Cpb23 are not charged in the initial state, the main electrodes 1 and 2 are at the ground potential. Next, when the switch 7 is closed by a signal from a control device (not shown), the charge stored in the third capacitor Cd24 is transferred through the path of the third capacitor Cd24, the switch 7 and the primary winding 26 of the transformer 25. As a result, voltages having opposite polarities are generated in the first secondary winding 27a and the second secondary winding 27b of the transformer 25, respectively. At this time, the first capacitor Cpa2
The voltage Va generated at 2 and the voltage Vb generated at the second capacitor Cpb23 have symmetrical voltage waveforms of opposite polarities, respectively, as shown in FIG. As a result, the voltages Va and Vb are applied between the main electrodes 1 and 2 and the ground potential, respectively, and the sum voltage of Va and Vb is applied to the laser gas between the main electrodes 1 and 2. Then, at time t _1, the X-ray source 20 provided on the back of the main electrode 1, between the main electrodes 1 and 2 pulsed X-ray 21 shown in Figure 2 in which X is transmitted through the main electrodes 1 When irradiated with the laser gas, the laser gas between the main electrodes 1 and 2 is pre-ionized, and the electron density between the main electrodes increases. Voltage between main electrodes 1 and 2 (V
When a + Vb) reaches the discharge breakdown voltage of the laser gas between the main electrodes 1 and ₂ at time t2, a glow discharge 11 is formed between the main electrodes 1 and 2 to excite the laser gas and cause an optical resonance (not shown). Laser light is emitted in the direction perpendicular to the plane of the drawing by the action of the container.

In the above process, the pulse-shaped voltages applied to the main electrodes 1 and 2 always have positive and negative symmetric waveforms with respect to the ground potential, and the shape of the surface of the main electrodes 1 and 2 that is in contact with the laser gas is Since they have the same shape, when the voltage applied between the main electrodes 1 and 2 increases, a discharge breakdown phenomenon hardly occurs between the main electrode and the ground potential or between the main electrodes. Furthermore, the main electrode 1
The X-ray source 20 is installed on the back side of the device, and the preliminary ionization electrode is not installed near the main electrode as in the past, so that the electric field distribution between the main electrodes 1 and 2 becomes uniform, and the discharge breakdown electrode becomes To rise. Further, since the discharge start time can be controlled by the action of the X-ray 21 generated from the X-ray source 20, even if the first capacitor Cpa22 and the second capacitor Cpb23 are charged with a low-speed pulse, the discharge breakdown voltage can be controlled. And glow discharge can be generated in a stable state at an optimal time.
As a result, after all the charges stored in the third capacitor Cd24 are transferred to the first capacitor Cpa22 and the second capacitor Cpb23, the glow discharge 11 can be generated, so that the energy transfer efficiency can be increased. In addition, since the discharge breakdown voltage can be increased, the oscillation efficiency can be increased even in the case of an excimer laser. Further, the first capacitor Cpa2
Since the pulse voltage for charging the second and second capacitors Cpb23 may be a low-speed pulse waveform, the transformer 25 can be used, and the charging voltage for the third capacitor Cd24 is
Can be reduced according to the turns ratio of the primary winding and the secondary winding.

As described above, according to the present embodiment, the current pulse flowing through the switch 7 becomes slow, and the voltage applied to the switch 7 is also reduced, so that the duty of operation of the switch 7 is greatly reduced. Therefore, a semiconductor switch such as a thyristor can be used, which is advantageous for increasing the repetition rate and extending the life of the pulse laser oscillation device.

[Effects of the Invention] As described above, according to the present invention, a capacitor connected between main electrodes is divided into a first capacitor and a second capacitor having the same capacitance, and both are connected in series. Connect to
In addition, the connection point is grounded, and the first capacitor and the second capacitor are respectively connected to the secondary windings of two series of transformers having opposite polarities, and a third winding is connected to the primary winding of the transformer. A closed circuit is formed by connecting a capacitor and a switch, and the third capacitor is connected to a DC power supply, and a device for irradiating short-wavelength light between the main electrodes is provided outside the main electrodes. This greatly reduces the duty of operation of the switch, widens the selection range of the switch, increases the oscillation efficiency of the laser, and provides a pulse laser oscillation device with high efficiency and long life.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the pulse laser oscillation device of the present invention, FIG. 2 is an explanatory view of the operation of one embodiment of the present invention, and FIG. 3 is a configuration showing one example of a conventional pulse laser oscillation device. FIG. 1, 2 ... main electrode, 3a, 3b ... preliminary ionization electrode, 4 ... gap, 5 ... capacitor Cs, 6 ... charging inductance, 7 ... switch, 8 ... charging resistance, 9 ... high voltage Power supply
HV, 10 Capacitor Cb, 11 Glow discharge, 12 High voltage power supply HVA, 20 X-ray source, 21 X-ray, 22 First capacitor Cpa, 23 Second capacitor Cpb, 24 ... third capacitor Cd, 25 ... transformer, 26 ... primary winding,
27a: first secondary winding; 27b: second secondary winding.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-130978 (JP, A) JP-A-1-274485 (JP, A) JP-A-1-128482 (JP, A) JP-A-63- 217678 (JP, A)

Claims (1)

(57) [Claims] 1. A pulse laser oscillation device comprising a pair of main electrodes arranged opposite to each other in a container hermetically filled with a laser gas, and a capacitor connected between the main electrodes. The capacitor is divided into two parts, a capacitor and a second capacitor, and both are connected in series.
In addition, the connection point is grounded, and the first capacitor and the second capacitor are respectively connected to the secondary windings of two series of transformers having opposite polarities, and a third winding is connected to the primary winding of the transformer. A device for connecting a capacitor and a switch to form a closed circuit, connecting the third capacitor to a DC power supply, and further irradiating short-wavelength light between the main electrodes whose voltage is gradually raised. A pulse laser oscillation device, which is provided between the main electrodes.