JPH05110182A - Laser oscillator - Google Patents

Abstract

PURPOSE:To provide a laser oscillator, generating a pulse using an acousto- optical element used in the field of high precision processing, which ensures a variety of application in the field requiring the processing with less effect of heat by obtaining the pulse having shorter duration. CONSTITUTION:A first acousto-optical element 1 and a second acousto-optical element 2 are provided and modulation timings of respective RF signal inputs are deviated by about 100 ns. Thereby, the skirt of laser output pulse can be cut to make short the pulse duration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser oscillator used in the fields of laser processing, measurement, analysis and the like.

[0002]

2. Description of the Related Art In recent years, laser oscillators have come to be used in the field of precision processing as well as processing such as cutting and welding. In particular, a continuous wave Nd: YAG laser using an acousto-optic element as a Q switch element has a feature that a laser output with high peak power can be obtained, and is therefore applied to a wide range of applications such as trimming, scribing and repairing.

A continuous wave Nd: YAG laser using a conventional acousto-optic device will be described below.

FIG. 4 is a diagram showing the structure of a continuous wave Nd: YAG laser using a conventional acoustooptic device. In FIG. 4, reference numeral 1 is an acousto-optic device, and RF from an external drive circuit.
The signal is applied. A laser house 3 houses a YAG laser crystal, an excitation lamp, an excitation light focusing mirror, and the like. Reference numeral 4 is a rear mirror, 5 is an output mirror, and 4 and 5 constitute an optical resonator. Reference numeral 6 is a shutter, and 7 is a laser beam.

The relative positional relationship between the rear mirror 4 and the output mirror 5 is appropriately adjusted, and the excitation lamp in the laser house is continuously lit while the shutter 6 is open, and Y
When the excitation energy exceeding the threshold of laser oscillation is supplied to the AG laser crystal, laser oscillation continuously starts inside the resonator, and a part of the laser oscillation is extracted from the output mirror 5 as laser light.

The continuous laser oscillation described above changes to pulsed oscillation when the modulated RF signal is applied to the acousto-optic element. The process will be described with reference to FIG. Figure 5
(A) shows the modulated RF signal, where the vertical axis is amplitude and the horizontal axis is time. Reference numeral 8 is a portion where the RF signal is applied, and 9 is a portion where the RF signal is OFF. FIG. 5C shows the timing at which pulsed laser oscillation occurs, where the vertical axis represents laser intensity and the horizontal axis represents time. Reference numeral 11 indicates a pulsed laser oscillation. When an RF signal is applied, an ultrasonic diffraction grating is formed in the acousto-optic element, the internal loss of the resonator increases, the Q value decreases, and the laser oscillation stops. When the RF signal is turned off, the internal loss of the resonator disappears, the Q value increases, and the laser oscillation starts again, so that the laser oscillation is pulsed by so-called Q switching. The pulsed laser oscillation has a high peak power because the excitation energy accumulated in the YAG laser crystal while the laser oscillation is stopped is emitted in a short time due to the rapid switching of the Q value. It becomes a so-called giant pulse.

FIG. 6 shows the time axis of the pulsed laser oscillation 11 extended. Pulse width is full width at half maximum of 10
About 0 to 200 ns, the rise is relatively quick, but the fall is tailed.

[0008]

Recently, in the field of precision machining by laser, there are an increasing number of applications that require machining with less influence of heat by using a laser having a shorter pulse width.
Even in a continuous wave Nd: YAG laser using an acousto-optic device, further shortening of the pulse is required as compared with the conventional one.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a laser oscillator having a shorter pulse width in pulsing using an acoustooptic device.

[0010]

In order to achieve this object, a laser oscillator of the present invention comprises a plurality of acousto-optic elements, and the modulation timing of RF signal input applied to each acousto-optic element is 1 μs. It has a configuration of shifting within the following range.

[0011]

With this configuration, the RF signal applied to the first acousto-optic element is turned off to cause pulsed laser oscillation, and thereafter the RF signal is applied to the second and subsequent acousto-optic elements within a range of 1 μs or less. By applying with a delayed timing, the bottom of the laser pulse can be cut and the pulse width can be shortened.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a first acousto-optic device, 2 is a second acousto-optic device, 3 is a laser house, 4 is a rear mirror, 5 is an output mirror, and 6 Is a shutter, and 7 is a laser beam.

The operation of the laser oscillator configured as described above will be described with reference to FIG. FIG. 2A shows the modulated RF signal applied to the first acousto-optic element, and FIG. 2B shows the modulated RF signal applied to the second acousto-optic element. FIG. 3C shows the timing of pulsed laser oscillation. 8
Indicates a state where an RF signal is applied, 9 indicates a state where the RF signal is OFF, and 10 indicates a laser pulse. The laser oscillation is started by turning off the RF signal to the first acousto-optic element and stopped by applying the RF signal to the second acousto-optic element. RF signal OFF to this first acousto-optic element
By shifting the timing of applying the RF signal to the second acoustooptic device by about 100 ns, the trailing edge of the pulsed laser output can be cut as shown in FIG.

As described above, according to the present embodiment, by using the first and second acousto-optic elements and shifting the timing of modulation of each RF signal input by about 100 ns, the tail of the laser output pulse is changed. The pulse width can be shortened by cutting.

[0016]

As described above, according to the present invention, a plurality of acousto-optic elements are provided and RF applied to each acousto-optic element.
By shifting the modulation timing of the signal input within the range of 1 μs or less, it is possible to realize an excellent laser oscillator that can obtain a laser output with a short pulse width.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a laser oscillator according to an embodiment of the present invention.

FIG. 2 (a) is a modulated R to the first acousto-optic device.
Waveform diagram of F signal (b) Waveform diagram of modulated RF signal to second acousto-optic device (c) Timing diagram of pulsed laser oscillation

FIG. 3 is a diagram showing a pulsed laser output with a trailing edge cut off.

FIG. 4 is a continuous oscillation Nd: Y using a conventional acousto-optic device.
Diagram showing the configuration of the AG laser

5A shows a modulated RF signal. FIG. 5B shows a timing at which pulsed laser oscillation occurs.

FIG. 6 is a diagram showing a pulsed laser oscillation output.

[Explanation of symbols]

 1 1st acousto-optic element 2 2nd acousto-optic element 3 Laser house

[Procedure amendment]

[Submission date] November 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The continuous laser oscillation described above changes to pulsed oscillation when the modulated RF signal is applied to the acousto-optic element. The process will be described with reference to FIG. Figure 5
(A) shows the modulated RF signal, where the vertical axis is amplitude and the horizontal axis is time. Reference numeral 8 is a portion where the RF signal is applied, and 9 is a portion where the RF signal is OFF. FIG. 5B shows the timing at which pulsed laser oscillation occurs, where the vertical axis represents laser intensity and the horizontal axis represents time. Reference numeral 11 indicates a pulsed laser oscillation. When an RF signal is applied, an ultrasonic diffraction grating is formed in the acousto-optic element, the internal loss of the resonator increases, the Q value decreases, and the laser oscillation stops. When the RF signal is turned off, the internal loss of the resonator disappears, the Q value increases, and the laser oscillation starts again, so that the laser oscillation is pulsed by so-called Q switching. The pulsed laser oscillation has a high peak power because the excitation energy accumulated in the YAG laser crystal while the laser oscillation is stopped is emitted in a short time due to the rapid switching of the Q value. It becomes a so-called giant pulse.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

FIG. 2 is a diagram showing a timing of pulsed laser oscillation generated by applying a modulated RF signal in the laser oscillator.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

FIG. 5 is a diagram showing the timing of a pallet-like laser oscillation that occurs when a modulated RF signal is applied in a conventional laser oscillator.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (1)

[Claims] 1. A laser oscillator comprising a plurality of acousto-optic elements, wherein the timing of modulation of an RF signal input applied to each acousto-optic element is shifted within a range of 1 μs or less.