JP3432854B2 - Pulse gas laser oscillator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed pulse repetition pulse gas laser oscillation apparatus using a lateral discharge excitation method such as an excimer laser. 2. Description of the Related Art FIG. 4 is a block diagram of such a pulse gas laser oscillation device. The laser tube has a pair of discharge electrodes 1,
2 are arranged facing each other. A plurality of peaking capacitors 3 and 4 are connected in parallel to the discharge electrode 1, and a plurality of spark pins 5 and 6 are connected to the discharge electrode 1. The other discharge electrode 2 is connected to opposing electrodes 7 and 8 for the respective spark pins 5 and 6. [0003] A main capacitor 9 is connected between the discharge electrodes 1 and 2, and the electric charge stored in the main capacitor 9 is turned on by the switching element 10 so that each of the discharge electrodes 1 and 2 is discharged.
The transition is between the two. Accordingly, when the electric charge of the main capacitor 9 is transferred to the respective discharge electrodes 1 and 2, the respective peaking capacitors 3 and 4
Is charged, and a gap discharge is generated in each of the spark pins 5 and 6 by this charging. The gas laser medium between the discharge electrodes 1 and 2 is pre-ionized by the ultraviolet light generated by the gap discharge. At the same time, the voltage between the discharge electrodes 1 and 2 increases, and a pulse discharge occurs in the space between the discharge electrodes 1 and 2. This pulse discharge excites the gas laser medium,
Laser oscillation starts. Thereafter, the pulse discharge is repeated and the pulse gas laser is oscillated. However, when the number of repetitions of the pulse discharge is increased or the energy supplied between the discharge electrodes 1 and 2 is increased, the discharge concentrates between the discharge electrodes 1 and 2 and the gas laser medium becomes less dense. Excitation is not performed uniformly between the discharge electrodes 1 and 2. The concentration of the discharge is because the subsequent pulse discharge occurs before the component generated by the preceding pulse discharge flows between the discharge electrodes 1 and 2, and the subsequent pulse discharge occurs at this time. In this case, a discharge occurs along a generated component of the preceding pulse discharge, and a non-uniform discharge phenomenon occurs. Therefore, in order to eliminate the concentration of discharge, it is conceivable to blow off generated components by increasing the gas flow of the gas laser medium, but this increases the size of the blower and the like. On the other hand, in order to make the pulse discharge uniform, the pre-ionization intensity is increased to secure a higher density and uniform discharge pre-ionization than the distribution density of the residual components generated by the preceding pulse discharge. Is required. In order to secure such uniform preliminary ionization, X-rays are irradiated from the back of each of the discharge electrodes 1 and 2 or the installation density of the spark pins 5 and 6 is increased to increase the preliminary ionization density. We are securing. As another method, after preionization prior to pulse discharge, a voltage called a short pulse and high voltage spiker is applied to each of the discharge electrodes 1 and 2 to increase preionization charge. . [0011] However, there is a method for making the pulse discharge uniform as described above, but there is a problem that the structure is complicated in either case. For this reason, it was difficult to secure uniform discharge preliminary ionization, and the efficiency of pulsed gas laser oscillation was low. Therefore, an object of the present invention is to provide a pulse gas laser oscillation device that can stabilize pulse gas laser oscillation and improve its efficiency. According to the first aspect of the present invention, there is provided a laser tube in which a gas laser medium is sealed, a pair of first discharge electrodes arranged to face each other in the laser tube, and a laser tube in the laser tube. A plurality of pairs of second discharge electrodes arranged to face each other so as to coincide with the optical axis direction of laser oscillation, a peaking capacitor connected to one of the first and second discharge electrodes, and a peaking capacitor. A pulse voltage is applied to the connected spark pin, a counter electrode disposed at a predetermined gap position with respect to the spark pin, and a first discharge electrode to generate a gap discharge between the spark pin and the counter electrode. between the first discharge electrode preionization, a first high-voltage pulse power source for generating a pulsed discharge between the first discharge electrode with this release pulse occurs in the first discharge electrodes Te
After a predetermined time delay from the discharge, a pulse voltage is applied to the second discharge electrode, a gap discharge is generated between the spark pin and the counter electrode, and preliminary ionization is performed between the second discharge electrodes. To generate a pulse discharge between the discharge electrodes
The predetermined time to be delayed is set in the range of 5 to 100 ns, and the first discharge electrode is set by the predetermined delay time.
Between the second discharge electrodes by pulse discharge
In this state, pulse discharge is generated to the second discharge electrode.
This is a pulse gas laser oscillation apparatus which achieves the above object by setting the pulse voltage applied to the second discharge electrode to be higher than the pulse voltage applied to the first discharge electrode. According to the first aspect, the first discharge electrode and the second discharge electrode arranged in the oscillation direction of the pulse gas laser are provided.
First, a pulse discharge is generated at the first discharge electrode among the electrodes.
After the predetermined time within the range of 5 to 100 ns
By generating a pulse discharge at the second discharge electrode,
The pulse laser oscillated at the first discharge electrode is the second discharge electrode
Between the second discharge electrode and the uniform preionization effect
In this state, pulse discharge is applied to the second discharge electrode.
If generated, pulse gas laser oscillation can be performed efficiently
You. Further, a pulse voltage applied to the second discharge electrode
Is set higher than the pulse voltage applied to the first discharge electrode.
Pulse energy applied to the first discharge electrode
-Pulse energy applied to the second discharge electrode rather than density
-Increased density, stabilization of pulsed gas laser oscillation and
The laser oscillation output increases and the efficiency can be further improved
it can. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a pulse gas laser oscillation device applied to an excimer laser. In a laser tube 20 in which an excimer gas laser medium is sealed, two pairs of discharge electrodes 21 to 24 are arranged.
22 are arranged to face each other, and the discharge electrodes 23 and 24 are arranged to face each other. In addition, each pair of these discharge electrodes 21,
Reference numerals 22, 23, and 24 are arranged so as to coincide with the optical axis direction of the laser oscillation. Each of the discharge electrodes 21 and 23 is connected in parallel with a respective peaking capacitor 25 and 26, respectively.
Spark pins 27 and 28 are connected to these peaking capacitors 25 and 26, respectively. Each of the other discharge electrodes 22 and 24 has a corresponding counter electrode 2 at a position corresponding to each of the spark pins 27 and 28.
9 and 30 are provided at predetermined gap positions with respect to the respective spark pins 27 and 28. The laser tube 20 is provided with a high-reflection mirror 31 and an output mirror 32 that constitute a laser resonator in the optical axis direction of the pulsed laser oscillation. On the other hand, the discharge control device 33 generates the previous pulse discharge on one of the pair of discharge electrodes 21, 22 and 23, 24, and terminates the pulse discharge. It has a function of generating a subsequent pulse discharge in the other discharge electrodes 23 and 24 within a period not to be performed. More specifically, high-voltage pulse power supplies 34 and 35 are provided, and a pulse oscillation control signal s is input to these high-voltage pulse power supplies 34 and 35 to apply pulse voltages to a pair of discharge electrodes 21, 22 and 23, respectively. 24.
The pulse oscillation control signal s is input to the high-voltage pulse power supply 35 after being delayed by the time td by the delay circuit 36. The delay time td is set to be equal to or less than the preceding pulse discharge width at each of the discharge electrodes 21 and 22. Next, the operation of the apparatus configured as described above will be described. When the pulse oscillation control signal s is generated, the pulse oscillation control signal s is input to the high voltage pulse power supply 34 and is delayed by the time td by the delay circuit 36 before being input to the other high voltage pulse power supply 35. When the pulse oscillation control signal s is input to the high-voltage pulse power supply 34 at time t1 shown in FIG. 2, a pulse voltage is output from the high-voltage pulse power supply 34, and the pulse voltage is supplied between the pair of discharge electrodes 21 and 22. Applied. When a pulse voltage is applied between these discharge electrodes 21 and 22, each peaking capacitor 25 is charged through each spark pin 27, and a gap discharge occurs in each spark pin 27 by this charging. Ultraviolet rays are generated by this gap discharge,
The excimer laser medium between the discharge electrodes 21 and 22 is preionized by the ultraviolet rays. At the same time, each discharge electrode 2
The voltage between the discharge electrodes 21 and 2 increases.
A pulse discharge is generated in the space 2. FIG. 2 shows a current waveform of the discharge current ia due to the pulse discharge. The excimer laser medium is excited by this pulse discharge, and the high reflection mirror 31 constituting the laser resonator is excited.
Excimer laser oscillation rises between the output mirror 32 and the output mirror 32. The raised excimer laser has light energy for ionizing the excimer laser medium between the laser resonators. Accordingly, the excimer laser reciprocates between the high-reflection mirror 31 and the output mirror 32 to perform a uniform preionization action in the optical axis direction of the excimer laser reciprocation. Thereby, each of the other discharge electrodes 2
The excimer gas laser medium between 3 and 24 is uniformly preionized. On the other hand, when the delayed pulse oscillation control signal s is input to the high-voltage pulse power supply 35 during the oscillation of the excimer laser, a pulse voltage is output from the high-voltage pulse power supply 35, and the pulse voltage is output from the other pair. Discharge electrode 23, 2
4 is applied. When a pulse voltage is applied between these discharge electrodes 23 and 24, each peaking capacitor 2
6 is charged through each spark pin 28, and this charging causes a gap discharge to occur in each spark pin 28. Ultraviolet rays are generated by the gap discharge, and the ultraviolet rays preliminarily ionize the excimer laser medium between the discharge electrodes 23 and 24. In this case, the excimer laser medium between the discharge electrodes 23 and 24 is already preionized uniformly by the oscillation of the excimer laser, and is preionized by being superimposed on the preionization. Therefore, a higher preliminary ionization density and uniformity are secured between the discharge electrodes 23 and 24 than in the case where only the gap discharge is generated at each spark pin 28. As a result, a pulse discharge having a higher uniformity than the previous pulse discharge between the respective discharge electrodes 21 and 22 is generated between the respective discharge electrodes 23 and 24 following the previous pulse discharge. FIG. 2 shows the waveform of the discharge current ib at this time. In this case, even if the arrangement pitch of the spark pins 28 varies, a pulse discharge with good uniformity is generated due to the high uniformity of the preliminary ionization density. In the laser resonator, since laser oscillation has already occurred due to pulse discharge at one of the discharge electrodes 21 and 22, energy conversion into laser oscillation by pulse discharge at the other discharge electrodes 23 and 24 has occurred. Is performed early and the conversion efficiency is high. In this case, the time difference (delay time td) between the pulse discharge firstly generated on the discharge electrodes 21 and 22 and the pulse discharge subsequently generated on the discharge electrodes 23 and 24 depends on the width of the discharge pulse. Setting within the range of 5 to 100 ns provides the highest oscillation efficiency. Thereafter, each pulse voltage from each of the high-voltage pulse power supplies 34 and 35 is 1 respectively.
The excimer laser is applied to a pair of discharge electrodes and output at a high repetition rate. As described above, in the above-described embodiment, a pulse discharge is generated at one of the discharge electrodes 21 and 22 by the discharge control device 33, and after the time td within the pulse discharge width, the other discharge electrodes 23 and 24 are generated. Since a pulse discharge is generated, the pre-ionization between the other discharge electrodes 23 and 24 can be uniformly pre-ionized by the oscillation of the excimer laser, thereby ensuring a high pre-ionization density and uniformity between the discharge electrodes 23 and 24. It is possible to obtain high conversion efficiency of the excimer laser even when operated at a high repetition rate. In addition, even if the previously generated pulse discharge becomes unstable, the subsequent pulse discharge can be generated in the stabilized region by setting the timing of the subsequent pulse discharge within the previous pulse discharge width. An excimer laser can be output with stable operation. Note that the present invention is not limited to the above-described embodiment, and may be modified without departing from the scope of the invention. For example, the pulse voltage of the high-voltage pulse power supply 35 is set higher than the pulse voltage of the high-voltage pulse power supply 34, and the pulse energy density is applied first to the discharge electrodes 21 and 22 for generating the pulse discharge. The pulse energy density applied to the generated discharge electrodes 23 and 24 may be increased. As a result, the pulse discharge current becomes the preceding pulse discharge current is and the subsequent pulse discharge current ip as shown in FIG. 3, and the pulse gas laser oscillation is stabilized and the laser oscillation output is increased, thereby further increasing the efficiency. Can be. Further, in order to stabilize the pulsed gas laser oscillation and increase the efficiency of the laser oscillation, the area of the discharge electrodes 21 and 22 for generating the pulse discharge first is reduced by the discharge electrodes 23 and 24 for generating the subsequent pulse discharge. May be formed to have a large area. Further, the generation timing of the previous pulse discharge and the subsequent pulse discharge may be controlled within the previous pulse discharge width as shown in FIG. This allows
Even if the previous pulse discharge is unstable, the timing of the subsequent pulse discharge can be varied in the stabilization region within the previous pulse discharge width, and the discharge stabilization region can be made large. Therefore,
The stable operation region of laser oscillation as the whole device can be expanded. In addition, since the generation timing of the subsequent pulse discharge can be varied, the duration of laser oscillation can be extended. As described above, the energy of the subsequent pulse discharge can be increased and the timing of generation can be varied. For example, when applied to laser material processing or the like,
The pulse width and pulse waveform can be controlled in accordance with the characteristics of the processing material, which has a great effect on practical use. In the above-described embodiment, the case where two pairs of discharge electrodes are arranged has been described. However, the present invention is not limited to two pairs, and a plurality of pairs of discharge electrodes may be arranged. In this case, a pulse discharge is generated before any one of the plurality of pairs of discharge electrodes, and then a subsequent pulse discharge is generated on each of the other discharge electrodes. The timing at which the pulse discharge occurs is not limited to the delay circuit 36, and a magnetic pulse compression circuit may be connected to the high-voltage pulse power supply to delay the application timing of the pulse voltage. Further, the present invention is not limited to the excimer laser, but can be applied to other gas lasers. [0047] According to the present invention as Shoki according to the present invention above, the
Pre-ionization uniformly between the second discharge electrodes by the first discharge electrode
High preionization density between the second discharge electrodes.
And uniformity.
High conversion efficiency of the Kisima laser can be obtained.
The pulse discharge generated by the first discharge electrode is unstable
, The timing of the pulse discharge of the second discharge electrode
Is set within the pulse discharge width of the first discharge electrode.
The pulse discharge of the second discharge electrode is generated in the stabilized region.
Excimer laser can be output with stable operation.
Stabilization of pulsed gas laser oscillation and laser oscillation output
It is possible to provide a pulse gas laser oscillating device which can be increased in size to further increase the efficiency .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing one embodiment of a pulse gas laser oscillation device according to the present invention. FIG. 2 is a diagram showing generation timing of pulse discharge in the device. FIG. 3 is a diagram showing a variable energy of pulse discharge in the device. FIG. 4 is a configuration diagram of a conventional device. [Description of Signs] 20: laser tube, 21 to 24: discharge electrode, 25, 26 ...
Peaking capacitors, 27, 28 ... spark pins, 2
9, 30: counter electrode, 31: high reflection mirror, 32: output mirror, 33: discharge control device, 34, 35: high voltage pulse power supply, 36: delay circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-246981 (JP, A) JP-A-1-241188 (JP, A) JP-A-5-102579 (JP, A) JP-A-61- 14785 (JP, A) JP-A-61-107778 (JP, A) JP-A-63-98172 (JP, A) JP-A-63-92073 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) H01S 3/00-3/30

Claims (1)

(57) [Claim 1] A laser tube in which a gas laser medium is sealed, a pair of first discharge electrodes opposed to each other in the laser tube, and laser oscillation light in the laser tube. A plurality of pairs of second discharge electrodes arranged to face each other so as to match in the axial direction; a peaking capacitor connected to one of the first and second discharge electrodes; and a peaking capacitor connected to the peaking capacitor. A spark pin, a counter electrode disposed at a predetermined gap position with respect to the spark pin, and a pulse voltage applied to the first discharge electrode to generate a gap discharge between the spark pin and the counter electrode. It is allowed to preionization between the first discharge electrode, a first high-voltage pulse power source for generating a pulsed discharge between the first discharge electrodes therewith, generated in the first discharge electrode That the pulse discharge was delayed Tokoro <br/> constant time than the pulse voltage is applied to the second discharge electrodes, the spark pins and the second by generating gap discharge between the counter electrode A second high-voltage pulse power supply for pre-ionizing between the discharge electrodes and generating a pulse discharge between the second discharge electrodes together with the second discharge electrode, wherein the predetermined time to be delayed is 5 to 100 ns. And the first discharge electrode is set by the predetermined delay time.
Between the second discharge electrodes by pulse discharge
Preionization is performed, and the pulse is applied to the second discharge electrode in this state.
Scan discharge is generated, and wherein the pulse voltage applied to the second discharge electrode, the high is set from the pulse voltage applied to the first discharge electrode, pulsed gas laser oscillator, characterized in that .