JPH04209580A - Pulse laser oscillator - Google Patents

Abstract

PURPOSE:To remarkably reduce the operating duty of a switch and to improve energy density to be injected to a glow discharge by setting the opposed length between main electrodes to a predetermined length, and emitting a short wavelength light between the main electrodes from a predetermined direction. CONSTITUTION:When opposed length of main electrodes 1, 2 is so set to the surface length B of the same direction as that of laser gas flow of the electrodes 1, 2 as to be A<1/2.B, a discharge length between the electrodes 1 and 2 is shortened to improve stability of a glow discharge. The electrodes 1, 2 are preliminarily ionized by emitting an X ray 12 of a direction perpendicular to the longitudinal direction of the electrodes 1, 2 from an X-ray source, uniformity of the discharge is enhanced, and energy density to be injected to the discharge is enhanced. On the other hand, a discharge starting time is controlled by the X-ray 12 to enhance a discharge breakdown voltage per unit length is enhanced, and a discharge impedance can be enhanced. The X-ray source is provided externally to remarkably reduce the operating duty of a switch 7. Thus, a pulse laser oscillator having a high efficiency, a long life is provided.

Description

[Detailed description of the invention]

[Object of the invention 1 [00011

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulsed laser oscillation device, and more particularly to a pulsed laser oscillation device in which the discharge section and power supply configuration have been improved. [0002] [0002] In a discharge excitation type gas laser device, laser oscillation is obtained by generating a spatially uniform glow discharge in a laser gas. In a pulsed laser oscillation device that uses a laser gas, the pressure of the laser gas is higher than atmospheric pressure, and furthermore, it contains a gas component with strong electron adhesion, so it is difficult to uniformly ignite the glow discharge. For this reason, it is common to perform preliminary ionization prior to glow discharge ignition and to apply a high-speed pulse voltage to the discharge portion to form a glow discharge. [0003] FIG. 2 is a diagram showing an example of a discharge section configuration and an excitation@source circuit of a conventional pulsed laser oscillation device. That is, a pair of main electrodes 1 and 2 are arranged facing each other, and the main electrodes 1.
The space surrounded by 2 is filled with laser gas. Further, the main electrode 2 is grounded. On the other hand, the pre-ionization@pole 3a is connected to the main electrode 1, and both are electrically at the same potential. The pre-ionization electrode 3a and the pre-ionization electrode 3b are disposed facing each other in the laser gas with a gap 4 interposed therebetween. Further, the pre-ionization electrode 3b is electrically insulated from the conductor that mechanically supports the main electrode 1, drawn out from the laser gas, and connected to the capacitor Cs5. Roughly speaking, one end of the charging inductance 6 is connected to the pre-ionization electrode 3.
b and the capacitor Cs5, and the other end is grounded. Further, the capacitor Cs5 is grounded via the switch 7, and is also connected to the high voltage power supply HV9 via the charging resistor 8.
It is connected to the. Furthermore, a capacitor CblO is connected between the main electrodes 1 and 2. One or more of these capacitors and inductances are connected in parallel. Further, an optical resonator (not shown) is arranged in a direction perpendicular to the plane of the paper. [0004] The conventional pulse laser oscillation device configured in this manner operates as described below. That is, in the initial state, the switch 7 is open and the high voltage @HHv
The capacitor Cs5 is charged through the path 9-charging resistor 8-capacitor Cs5-charging inductance 6-ground. On the other hand, since the capacitor CblO is not charged, the main electrode 1 is at ground potential. Next, when the switch 7 is closed, the potential on the switch 7 side of the capacitor Cs5 becomes the ground potential, so the potential on the pre-ionization electrode 3b side of the capacitor Cs5 is pre-ionized with the opposite polarity to the polarity with which the capacitor Cs5 is charged. It is added to the electrode 3b. on the other hand,
Since the pre-ionization electrode 3a is at ground potential, a high voltage 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 rays generated by this spark discharge. In addition, the charge stored in the capacitor Cs5 flows through the path of switch 7 - capacitor Cs5 - pre-ionization electrode 3b - gap 4 - secondary electrode 3a - main electrode 1 - capacitor CblO, and capacitor CblO 9 is charged. . In this way, when the voltage of the capacitor CblO increases and the voltage applied between the main electrodes 1 and 2 reaches the discharge breakdown voltage of the laser gas or higher, a glow discharge 11 is formed between the main electrodes 1 and 2, and the laser gas is excited. The laser beam is emitted in a direction perpendicular to the plane of the paper by the action of an optical resonator (not shown). [0005]

[Problems to be Solved by the Invention] By the way, in the conventional pulse laser oscillation device as described above, the capacitor C
It is possible to increase the charging voltage of 85 to several tens of kV or higher, and to increase the rate of charging the capacitor CblO, thereby shortening the time interval between the occurrence of the pre-ionization discharge formed in the gap 4 and the time interval between the formation of the glow discharge 11. is necessary. Therefore, the maximum value and time rate of change of the current flowing through the switch 7 are extremely large, which not only limits the types of usable switches but also shortens the life of the switch 7. Furthermore, it was not possible to increase the charging voltage above the maximum allowable current value and allowable current change rate determined by the characteristics of the switch 7. [0006] As described above, since the operating range and types of available switches are limited, it has been difficult to realize operating operations necessary for industrial applications such as repeated operation and long-life operation. In addition, in the case of conventional excimer lasers, the discharge breakdown voltage is determined by the rate of change in the terminal voltage of the capacitor cbio, and cannot be controlled externally, so it is not possible to increase the discharge starting voltage, and the discharge injection energy density cannot be increased. I couldn't raise it. Furthermore, since the discharge impedance is very low, the discharge length in the opposite direction of the main electrodes of the glow discharge @11 is increased to increase the discharge impedance, and the discharge impedance of the excitation power supply circuit is determined by the capacitor Cs5, the capacitor CblO, and the residual inductance of the circuit. I have tried to make it consistent. However, in this case, the discharge stability of the glow discharge @11 decreases as the discharge gap length increases, and the energy density that can be injected into the glow discharge 11 is kept low, so the upper limit of the laser oscillation efficiency is low. There were problems such as the intensity of the laser beam becoming unstable due to the unstable discharge. [00071] The present invention was proposed in order to eliminate the drawbacks of the prior art as described above, and its purpose is to significantly reduce the operating duty of the switch and increase the energy density that can be injected into the glow discharge. The object of the present invention is to provide a pulsed laser oscillation device with high efficiency and long life by increasing the oscillation efficiency of a laser. [Configuration of the invention 1 [0008]

[Means for Solving the Problems] The present invention provides a method for disposing a pair of main electrodes facing each other in a container hermetically filled with laser gas, and connecting a capacitor between the main electrodes in a direction perpendicular to the direction in which the main electrodes face each other. In a pulsed laser oscillation device that emits a laser beam in the direction of The device is characterized in that a device for irradiating short wavelength light between the main electrodes from a direction orthogonal to the main electrodes is provided outside the main electrodes. [0009]

[Function] According to the pulsed laser oscillation device of the present invention, the peak value of the pulse voltage applied between the main electrodes can be significantly reduced, and the operational responsibility of the switching element can be reduced.
It is possible to improve the discharge stability of glow discharge and increase the injectable energy density. [00101

[Embodiment] An embodiment of the present invention will be specifically described below with reference to FIG. Note that the same members as those of the conventional type shown in FIG. 2 are given the same reference numerals, and explanations thereof will be omitted. [00111 In this example, as shown in FIG.
The opposing length A between the main electrodes 1 and 2 is set to be 1/2 or less of the surface length B of the main electrodes 1 and 2 in the same direction as the laser gas flow. Further, the high voltage power supply HV9 is connected to a capacitor Cs5 via a charging resistor 8, and the other end of the capacitor Cs5 is connected to a capacitor CblO and grounded by a charging inductance 6. Further, a switch 7 is connected between the connection point between the charging resistor 8 and the capacitor Cs5 and the ground. Also, capacitor cb1
0 is connected between the main electrodes 1 and 2 via the ground potential. Furthermore, a device (not shown) that irradiates short wavelength light between the main electrodes from a direction perpendicular to the longitudinal direction of the main electrodes 1 and 2 is provided.
It is provided outside the main electrode. As a device for irradiating this short wavelength light, an X-ray source or the like can be used. Furthermore, one or more of the above capacitors, resistors, and inductances are connected in parallel. [0012] As mentioned above, the opposing length A between the main electrodes 1 and 2 is A<1/ with respect to the surface length B of the main electrode 1.2.
2.B was chosen based on the discharge impedance between the main electrodes and the energy density that can be injected into the glow discharge.
This is based on the results of intensive studies by the inventors. [0013] The pulse laser oscillation device of this embodiment having such a configuration operates as described below. That is, in the initial state, switch 7 is open and high voltage °1 source HV9
The capacitor Cs5 is charged through a path of charging resistor 8 - capacitor Cs5 - charging inductance 6 - ground. On the other hand, since capacitor CblO is not charged,
The main electrode 1 is at ground potential. Next, switch 7
When closed, the potential on the switch 7 side of the capacitor Cs5 becomes the ground potential, and the high voltage power supply H is connected to the capacitor CblO.
A voltage of opposite polarity to V9 is applied. Also, capacitor Cs
The charge stored in switch 7 - capacitor C85
- flows in the path of capacitor CblO and capacitor Cbl
O is being charged. [0014] Then, when a certain period of time has passed and the charge of the capacitor Cs5 is transferred to the capacitor CblO,
When X-rays 12 are irradiated from the sides of the main electrodes 1 and 2 from an X-ray source (not shown), the laser gas between the main electrodes 1 and 2 is pre-ionized, and the electron density between the main electrodes increases. . When the voltage between the main electrodes 1 and 2 reaches the discharge breakdown voltage of the laser gas between the main electrodes 1 and 2, the main electrodes 1. A glow discharge is formed between the two, the laser gas is excited, and a laser beam 13 is emitted by the action of an optical resonator (not shown). In this case, the cross-sectional shape of the laser beam 13 is such that the opposing length A between the main electrodes 1 and 2 is relative to the surface length B of the main electrodes 1 and 2 in the same direction as the laser gas flow. , A<1/2・
B, the discharge length between the main electrodes] and 2 is shortened, and the discharge stability of the glow discharge 11 is greatly improved. Further, since the main electrodes 1 and 2 are uniformly pre-ionized by the X-rays 12, the discharge uniformity of the glow discharge is very high, and the energy density that can be injected into the glow discharge is also greatly improved. As a result, especially in the excimer laser, laser oscillation efficiency is improved. On the other hand, the discharge impedance decreases because the discharge length between the main electrodes is shortened, but since the discharge start time can be controlled by the action of the X-rays 12 irradiated from the X-ray source, the discharge per unit length Breakdown voltage can be made higher than before, and discharge impedance can be made higher. Also, capacitor C8
Since glow discharge can be generated after all the charges stored in the capacitor CblO are transferred to the capacitor CblO, the energy transfer efficiency is also improved. Furthermore, the capacitor CblO and the main electrode 1.
By reducing the residual inductance of the discharge circuit formed from 2 and 2, the discharge impedance and the impedance of the excitation power supply circuit are matched. [0015] As described above, according to this embodiment, since the discharge breakdown voltage can be reduced, the voltage applied to the switch 7 is also reduced, making it possible to use a semiconductor switch, and increasing the repetition rate of the pulsed laser oscillation device. , which is advantageous for extending life. [0016] [Effects of the Invention] As described above, according to the present invention, the opposing length between the main electrodes is set to be 1/2 or less of the surface length of the main electrodes in the same direction as the laser gas flow. In addition, by installing a device outside the main electrodes that irradiates short wavelength light between the main electrodes from a direction perpendicular to the longitudinal direction of the main electrodes, the operational responsibility of the switch can be significantly reduced and it can be injected into the glow discharge. By increasing the energy density and increasing the laser oscillation efficiency, it is possible to provide a highly efficient and long-life pulsed laser oscillation device.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a pulse laser oscillation device of the present invention.

FIG. 2 is a configuration diagram showing an example of a conventional pulsed laser oscillation device.

[Explanation of symbols]

1 Main electrode 2 Main electrode 3a Pre-ionization electrode 3b Pre-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 X-ray 13 Laser light A Opposing length between main electrodes B Surface length of main electrode

Claims (1)

[Claims] 1. A pulsed laser in which a pair of main electrodes are arranged facing each other in a container hermetically filled with laser gas, a capacitor is connected between the main electrodes, and a laser beam is emitted in a direction perpendicular to the direction in which the main electrodes face each other. In the oscillation device, the length of the main electrodes facing each other is set to be 1/2 or less of the surface length of the main electrodes in the same direction as the laser gas flow, and the length of the main electrodes facing each other is set to be 1/2 or less of the surface length of the main electrodes in the same direction as the laser gas flow, and A pulsed laser oscillation device characterized in that a device for irradiating short wavelength light between the main electrodes is provided outside the main electrodes.