JPH02219019A - Pulse laser device - Google Patents

Abstract

PURPOSE:To extract only pulse laser light which has light intensity within a constant range selectively by providing a photodetector on one separation optical path of a beam splitter and a light delay means on the other, selecting only a detection signal which has a prescribed output level from the photodetector, and opening and closing an optical shutter. CONSTITUTION:Part of the pulse laser from a pulse laser generation part 2 is reflected by the beam splitter 6 and photodetected by a PIN photodiode 8. The PIN photodiode 8 outputs a detection pulse having a voltage level corresponding to the light intensity of the pulse laser and the detection pulse is inputted to a level selecting circuit 16 through an amplifier 14. The level selecting circuit 16 selects and outputs only a detection pulse whose level is between an upper and a lower threshold value. Then an optical shutter driving circuit 18 is actuated with the selected detection pulse to generate driving pulses for opening and closing the optical shutter 12. Consequently, only the pulse laser light which has light intensity within the constant range can be extracted selectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a pulsed laser device that can selectively extract only pulsed laser beams having a light intensity within a certain range.

(b) Conventional technology In general, pulsed lasers obtained by exciting a laser medium with electric discharge or electron beams have higher output than continuous lasers obtained by continuous wave excitation, and their application range in the field of laser processing is limited. is expanding.

(c) Problems to be Solved by the Invention Since a pulsed laser is excited by a pulsed discharge or the like as described above, its light intensity inevitably varies by several percent or more. Therefore, such a pulsed laser
For example, when used as a light source for semiconductor lithography, etc., unevenness in chemical reactions occurs due to variations in light intensity, resulting in problems such as the inability to obtain products of desired quality.

One way to reduce the intensity variations of pulsed lasers is to stabilize the excitation operation, but currently no particularly effective means of improvement have been found, and there are limits to stabilizing the light intensity itself.

(d) Means for Solving the Problems The present invention has been made in view of the above circumstances, and although variations in the intensity of the excited and emitted pulsed laser are accepted as they are, the result is a constant variation. The purpose is to be able to selectively extract only pulsed lasers with light intensity within a range.

In order to achieve the above object, the present invention adopts the following configuration.

That is, in the pulsed laser device of the present invention, a beam splitter is arranged on the output optical path of the pulsed laser generated from the pulsed laser generator, a light receiving element is placed on one separated optical path of the beam splitter, and a light receiving element is placed on one separated optical path of the beam splitter, and An optical delay means is provided on each road, and an optical shutter is arranged on the output optical path of the optical delay means, and the output level of the detection signal from the light receiving element is compared with a threshold value to obtain a predetermined level. It includes a level selection circuit that selects and outputs only the detection signal, and an optical shutter drive circuit that generates drive pulses for opening and closing the optical shutter based on the output of this level selection circuit.

(e) Effect In the above configuration, a part of the pulsed laser generated from the pulsed laser generator is separated and extracted by a beam splitter disposed on the emission optical path. Then, some of the separated pulse lasers are received by a light receiving element, and the output level of the detection signal from this light receiving element is compared with a threshold value in a level selection circuit, and only detection signals having a predetermined level are selected. Ru. Then, the optical shutter drive circuit is activated by the detection signal having the voltage level selected by the level selection circuit, and generates a drive pulse for opening and closing the optical shutter. On the other hand, the other pulsed laser separated by the beam splitter is introduced into the optical delay means and is output after being delayed by the time that causes a propagation delay from the light receiving element to the optical shutter drive. Therefore, the output timing of the pulse laser from the optical delay means and the opening/closing timing of the optical shutter coincide. Therefore, since the optical shutter is opened and closed according to the optical intensity of the pulsed laser, only the pulsed laser having the optical intensity within a certain range passes through the optical shutter and is output.

(F) Embodiment FIG. 1 is an overall configuration diagram of a pulse laser device according to an embodiment of the present invention. In the same figure, ■ indicates the entire pulse laser device, 2 is a pulse laser generating section that generates a pulse laser such as an extrema laser, and 4 is a pulse laser generating section 2.
A light intensity selection output section selectively extracts one having a certain range of light intensities from the pulsed lasers outputted from the light source.

The light intensity selection output unit 4 includes a beam splitter 6 disposed on the output optical path of the pulsed laser generated from the pulsed laser generator 2 . A PIN photodiode 8 as a light receiving element with excellent high-speed response is arranged on the reflected optical path of the beam splitter 6, and an optical fiber 10 as an optical delay means is arranged on the transmitted optical path of the beam splitter 6. Furthermore, this optical fiber lO
There is an optical shutter consisting of a Pockels cell etc. on the output optical path! 2 is placed. On the other hand, the above-mentioned PIN photodiode 8 includes an amplifier 14 for amplifying its detection output, which compares the output level of the detection signal from the amplifier I4 with a threshold value and selects only the detection signal having a predetermined level. Output level selection circuit! 6. An optical shutter driving circuit 18 such as a thyratron, which generates driving pulses for opening and closing the optical shutter 12 based on the output of the level selection circuit 16, is connected in sequence.

Next, the operation of the pulse laser device I having the above configuration will be explained.

The pulsed laser generated from the pulsed laser generator 2 is
A portion of the light is reflected by a beam splitter 6 placed on the output optical path and is received by a PIN photodiode 8. Since the PIN photodiode 8 outputs a detection pulse having a voltage level corresponding to the light intensity of the pulsed laser, this detection pulse is input to the level selection circuit 16 via the amplifier 14.

Upper and lower thresholds are preset in the level selection circuit 16 to allow only external signals having output levels within a specific range to pass through. That is, each of the upper and lower threshold values provides a selection criterion for the laser output, and the energy width of the pulsed laser to be extracted is determined according to the width of the upper and lower threshold values. Therefore, the detection pulse from amplifier 14 is
The level selection circuit 16 compares the detected pulses with upper and lower thresholds, and only those detection pulses having a level within the range of the upper and lower thresholds are selected and output. The detection pulse that has passed through this level selection circuit 16 causes an optical gloss drive circuit 18 to
is activated to generate drive pulses for opening and closing the optical shutter 12.

On the other hand, the pulsed laser transmitted through the beam splitter 6 is
is introduced into the optical fiber IO. A propagation delay occurs in each circuit after the pulsed laser is received by the PIN photodiode 8 until the optical shutter 12 is driven.
It is delayed by multiple reflections within O. As a result, the output timing of the pulse laser from the optical fiber 10 and the opening/closing timing of the optical shutter 12 coincide.

Therefore, since the optical shutter I2 is opened and closed according to the light intensity of the pulsed laser, only the pulsed laser having a light intensity within a certain range will pass through the optical shutter 12 and be taken out.

In the above embodiment, an optical fiber IO was used as the optical delay means, but the optical delay means is not limited to this. For example, as shown in FIG. 2, two total reflection mirrors 20a
, 20b are arranged facing each other, and one total reflection mirror 20a has an entrance 22, and the other total reflection mirror 20b has an exit 24, and the incident pulse laser is multiple reflected by both total reflection mirrors 20a and 20b. It is also possible to configure the device so that it can be taken out. Further, the threshold value set in advance for the level selection circuit 16 may be set to only one of the upper and lower thresholds, so that only pulsed lasers having an energy level above or below a specific energy level are extracted.

(g) Effects According to the present invention, only pulsed lasers having light intensities within a certain range can be selectively extracted, so that as a result, pulsed lasers with less variation in intensity can be used. Therefore, excellent effects such as being able to further expand the range of application in the field of laser processing than in the past are exhibited.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 is an overall configuration diagram of a pulse laser device, and FIG. 2 is a configuration diagram showing a modification of the optical delay means. ! ...Pulse laser device, 2.. Pulse laser generator, 6.. Beam splitter, 8. Light receiving element (PIN photodiode), 10.. Optical delay means (optical fiber), 12.. Optical shutter. 16...Level selection circuit,
18... Optical shutter drive circuit.

Claims (1)

[Claims] (1) A beam splitter is placed on the output optical path of the pulsed laser generated from the pulsed laser generator, a light receiving element is placed on one separated optical path of this beam splitter, and an optical delay means is placed on the other separated optical path. An optical shutter is arranged on the output optical path of the optical delay means, and the output level of the detection signal from the light receiving element is compared with a threshold value to select only the detection signal having a predetermined level. 1. A pulsed laser device comprising: a level selection circuit that outputs an output; and an optical shutter drive circuit that generates drive pulses for opening and closing the optical shutter based on the output of the level selection circuit.