JPH05160487A - Pulse generating device for pulse laser - Google Patents

Abstract

PURPOSE:To provide a pulse generating device for pulse laser with good laser excitation efficiency. CONSTITUTION:A capacitor 4 charged from a high-voltage power source 1 is discharged by closing a switch circuit 8 consisting of numerous high-speed switching elements 9 to apply the discharge current ix to a laser beam discharge tube 7. At this configuration a conduction signal from a gate circuit 12 for closing the switch circuit 8 is set to be off state before the discharge current ix becomes zero. Therefor, wasteful current will not flow after the laser beam discharge tube emits laser beam, resulting in improved laser excitation efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse generator for a pulse laser for generating a short wavelength pulse laser by repetitive pulse discharge such as a copper vapor laser or an excimer laser.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a pulse generator for a pulse laser using a conventional copper vapor laser. In the figure, 1 is a high voltage power supply, 2 is a charging reactor connected to a high voltage power supply 1, 3 is a charging diode serially connected to the charging reactor 2, 4 is a charging / discharging capacitor serially connected to the charging diode 3, and 8 is a high-speed switching element 9 including a large number of FETs (field effect transistors) and the like. A switch circuit composed of a series-parallel circuit, which is connected between the charging diode 3 and the high-voltage power supply 1.

Reference numeral 10 is a reverse current suppressing element connected in series with the capacitor 4, and is composed of a series-parallel circuit of a plurality of diodes or magnetic saturation elements. Reference numeral 11 is a bypass resistor connected in parallel to the reverse current suppressing element 10, 7 is a laser discharge tube connected between the reverse current suppressing element 10 and the high-voltage power supply 1, and 5 is a charging connected in parallel to the laser discharge tube 7. It is resistance.

Next, the operation will be described. The high voltage is slowly charged from the high voltage power supply 1 to the capacitor 4 through the charging reactor 2, the charging diode 3, the bypass resistor 11 and the charging resistor 5. Next, when the switch circuit 8 is turned on, the high voltage of the capacitor 4 applies a pulse voltage of several hundred nanoseconds to the laser discharge tube 7 via the reverse current suppressing element 10. As a result, the laser discharge tube 7 is discharged, and its discharge current i _x flows through the path of the capacitor 4, the switch circuit 8, the laser discharge tube 7, the reverse current suppressing element 10 and the capacitor 4. At this time, the reverse current suppressing element 10 suppresses the reverse current of the oscillating current due to the inductance of the circuit.

FIG. 6 shows a typical discharge current i of a copper vapor laser.
The waveform of _{x and} the waveform of the laser beam L are shown. In FIG. 6, the discharge current i _x flowing through the laser discharge tube 7 takes several hundred nanoseconds, and the laser light L is generated in about 50 nanoseconds in the first half of the discharge current i _x . In the case of a copper vapor laser, the life of the laser upper level is extremely shorter than that of the lower level, so that the current waveform flowing through the laser discharge tube 7 is required to have steepness. Therefore, only the first half of the current flowing through the laser discharge tube 7 is used for laser excitation, and the latter half of the shaded area in FIG. 6 flows after the laser light has ended. On the contrary, the energy not used for the laser excitation increases the gas temperature in the laser discharge tube 7 and increases the amount of the laser lower level. As a result, the laser excitation efficiency is reduced.

[0006]

Since the conventional pulse generator for pulsed lasers is constructed as described above, the current flowing through the laser discharge tube 7 cannot be effectively utilized, and conversely the laser excitation efficiency is lowered. There was a problem that it would end up.

The present invention was made in order to solve the above-mentioned problems, and it is possible to improve the laser excitation efficiency by not supplying unnecessary current to the laser discharge tube 7 after the end of laser oscillation. It is an object of the present invention to obtain a pulse generator for a pulsed laser that can be designed.

[0008]

A pulse generator for a pulse laser according to the present invention is configured so that a conduction signal from a gate circuit which drives the switch circuit is turned off before the discharge current becomes zero. It is a thing.

[0009]

Since the conduction signal from the gate circuit according to the present invention is turned off before the discharge current reaches zero, the current flowing through the laser discharge tube 7 can be interrupted midway, and as a result, the laser light is emitted. After the laser discharge tube 7
It is possible to prevent the discharge current from flowing through.

[0010]

EXAMPLES Example 1. In FIG. 1, parts corresponding to those in FIG. In FIG. 1, reference numeral 12 is a gate circuit for driving the switch circuit 8. The gate circuit G has a common gate terminal G and a common source terminal S in each parallel circuit stage of the high-speed switching elements 9 such as FETs forming the switch circuit 8. It is connected between them and is adapted to apply a conduction signal to the gate terminal G.

Reference numeral 13 is an optical oscillator for generating an optical pulse, and 14
Is an optical pulse generated by the optical oscillator 13 for each gate circuit 12
It is an optical fiber for giving to the photoelectric conversion element inside.

The gate circuit 12 and the optical oscillator 13 constitute a driving means.

FIG. 2 shows an embodiment of the gate circuit 12, 17 is a photoelectric conversion element for converting the optical pulse transmitted through the optical fiber 14 into an electric pulse signal, 15
Is a bias resistor connected to the output side of the photoelectric conversion element 17, and 16 is a waveform shaping circuit for shaping the pulse signal output from the photoelectric conversion element 17 into a conduction signal and applying it to the gate terminal G.

FIG. 3 shows an embodiment of the optical oscillator 13, in which 18 is an astable multivibrator which generates a repetitive pulse signal x ₁ having a predetermined cycle, and 19 is the pulse signal x.
₁ is a capacitor for differentiating, 20 is a diode for removing the negative differential pulse, 21 is a variable resistor for adjusting the width of the positive differential pulse, 22 is a waveform for shaping the differential pulse into a narrow pulse signal x ₂ A shaping circuit 23 is an electro-optical conversion element that converts the pulse signal x ₂ into an optical pulse and sends it to the optical fiber 14.

Next, the operation will be described. In FIG. 3, the output from the astable multivibrator 18 shown in FIG.
The repetitive pulse signal x ₁ shown in ( ₁₎ is differentiated by the differentiating circuit including the capacitor 19, the diode 20 and the variable resistor 21 to obtain a positive differential pulse and set its pulse width. The waveform of this positive differential pulse is shaped by the waveform shaping circuit 22 to become the narrow pulse signal x ₂ shown in FIG.

This pulse signal x ₂ is converted into the electro-optical conversion element 23.
Is converted into an optical pulse by the optical fiber 14
Through the gate circuit 12.

In FIG. 2, the optical pulse sent through the optical fiber 14 is converted into an electric pulse signal by the photoelectric conversion element 17. This pulse signal is subjected to waveform shaping by the waveform shaping circuit 16 so that each FE becomes a conduction signal composed of a pulse signal equivalent to the pulse signal x _{2 of} FIG.
The entire switch circuit 8 is made conductive by adding each FET to the common gate terminal G of the T parallel circuit stage and making each FET conductive.

According to the above, as shown in FIG. 4, the pulse width of the pulse signal x ₂ is shorter than the width of the discharge current i _x including the portion shown by the dotted line. Since the laser beam L becomes zero in the middle of the discharge current i _x , the current after time t ₁ is unnecessary. By setting the conduction signal by the pulse signal x ₂ off time of the high-speed switching element 9 to t _1, the discharge current i _x becomes zero at t _1, t ₁ and later will not be supplied current to the laser discharge tube 7. As a result, only energy effective for laser excitation is supplied to the laser discharge tube 7, and an efficient pulse laser can be obtained.

[0019]

As described above, according to the present invention, since the conduction signal from the gate circuit is turned off before the discharge current becomes zero, the laser discharge tube is useless for laser excitation. There is an effect that the current is not supplied and the laser excitation efficiency is significantly increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a pulse generator for a pulse laser according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a gate circuit in the device.

FIG. 3 is a configuration diagram of an optical oscillator in the same device.

FIG. 4 is a timing chart showing the operation of the device.

FIG. 5 is a configuration diagram of a conventional pulse generator for a pulse laser.

FIG. 6 is a waveform diagram of a discharge current of a laser discharge tube and laser light in the same device.

[Explanation of symbols]

 4 condenser 7 laser discharge tube 8 switch circuit 12 gate circuit (driving means) 13 optical oscillator (driving means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H03K 3/57 A 7328-5J 17/10 9184-5J (72) Inventor Kazuhiko Hara Tsukaguchi Honcho, Amagasaki 8-1-1, Central Research Laboratory, Mitsubishi Electric Corporation

Claims (1)

[Claims] 1. A pulse generator for pulsed laser, wherein a switch circuit is turned on by a turn-on signal output from a driving means to discharge a capacitor, and the discharge current is supplied to a laser discharge tube. A pulse generator for a pulse laser, comprising drive means for generating a conduction signal for bringing the switch circuit into an off state before 0 becomes zero.