JPH0422182A - Output device of q-switched pulse laser - Google Patents

Abstract

PURPOSE:To obtain a Q-switched pulse laser beam whose energy and peak output are definite even when the repetition number of the Q-switched pulsed laser beam is changed by providing the following: a solid-state laser medium; a pumping lamp; an optical resonator; an acoustooptic Q-switch arranged inside the optical resonator; a Q-switch drive circuit; and an excitation-amount control means. CONSTITUTION:Electric power is supplied to individual pumping lamps 3, 4 from a variable power supply 30 for the pumping lamps; a solid-state laser medium 2 is exciated. At this time, while high-frequency electric power is supplied to a Q-switch 8 from a Q-switch drive circuit 10, a loss inside a resonator 5 becomes large and a laser oscillation is stopped. When a laser oscillation state is caused suddenly, the induced emission by a large population inversion inside the medium 2 is executed instantly, and a high-peak Q-switched pulsed laser beam is output from an output mirror 7. The Q-switch drive circuit 10 applies a repetition-frequency signal to the current control terminal of the variable power supply 30 through a frequency/voltage conversion circuit 21, a limiter circuit 22 and an isolating amplifier 23 in an excitation- amount control circuit 20. Thereby, the individual pumping lamps 3, 4 emit light at an excitation amount which is proportional to the repetition frequency of the Q-switch 8.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a Q-switched pulsed laser output device.

(Prior Art) FIG. 4 is a block diagram of a Q-switched pulse laser output device. A solid-state laser medium 2 of Nd:YAG is provided inside the condenser mirror 1, and two excitation lamps 3 and 4, which are krypton arc lamps, for example, are arranged in parallel to the solid-state laser medium 2. A high reflection mirror 6 and an output mirror 7, which constitute a resonator 5, are arranged in the longitudinal direction of the solid-state laser medium 2, respectively. Between these high reflection mirror 6 and output mirror 7 is an acousto-optic Q switch (hereinafter referred to as Q
(abbreviated as switch) 8 is arranged. This Q switch 8 is operated by a Q switch driving circuit 9 at an arbitrary repetition frequency. In addition, each excitation lamp 3,
4 is supplied with power from the excitation lamp power source 10 and emits light.

With such a configuration, the solid laser medium 2 is excited by each excitation lamp 3.4 emitting light.

In this state, while high frequency power is supplied from the Q switch drive circuit 9 to the Q switch 8, the loss within the resonator 5 becomes large and laser oscillation is stopped. Then, when the supply of high-frequency power from the Q-switch drive circuit 9 to the Q-switch 8 is stopped, the loss within the resonator 5 decreases rapidly, and a laser oscillation state occurs.

Even while the laser oscillation is stopped, the laser medium 2 continues to be excited, and a large population inversion occurs within the laser medium 2. Here, when a laser oscillation state suddenly occurs, stimulated emission occurs at once due to a large population inversion within the laser medium 2, and Q-switched pulsed laser light with a high peak is output from the output mirror 7. However, since the Q switch 8 performs a switching operation at an arbitrary frequency, Q switch pulse laser light with a high peak is output every cycle of the same frequency.

By the way, such a Q-switched laser output device is applied to, for example, laser processing. In this laser processing, a Q-switched laser output device outputs a Q-switched pulsed laser beam with a high peak and irradiates the workpiece, and at this time the workpiece is moved according to the machining pattern. In this case, laser processing of the workpiece includes rough adjustment machining and fine adjustment machining, and among these, coarse adjustment machining speeds up the movement of the workpiece, and fine adjustment processing slows down the movement of the workpiece. are doing.

On the other hand, it is preferable that the number of Q-switched pulsed laser beams per unit length irradiated onto the workpiece be the same regardless of rough adjustment machining or fine adjustment machining. Therefore, in order to make the number of Q-switch pulses irradiated to the workpiece the same regardless of rough adjustment machining or fine-adjustment machining, the number of repetitions of Q-switch pulses is varied. However, when the number of repetitions of the pulsed laser beam is varied, the characteristics per IQ switch pulse, that is, the energy and peak output, decrease as the repetition frequency increases. Therefore, coarse adjustment machining and fine adjustment machining cannot be performed using Q-switched pulsed laser beams having the same characteristics.

(Problems to be Solved by the Invention) As described above, when the number of repetitions of the Q-switch pulsed laser beam is varied, the energy and peak output of the Q-switched pulsed laser beam change.

SUMMARY OF THE INVENTION An object of the present invention is to provide a Q-switch pulse laser output device that can output Q-switch pulse laser light with constant energy and peak output even if the number of repetitions of the Q-switch pulse laser light changes.

C. Configuration of the Invention (Means for Solving the Problems) The present invention provides a solid-state laser medium, an excitation lamp that excites the solid-state laser medium, and an optical resonator disposed facing each other with the solid-state laser medium in between. an acousto-optic Q-switch disposed within the optical resonator, a Q-switch drive circuit that switches the acousto-optic Q-switch at an arbitrary repetition frequency, and a repeating frequency output from the Q-switch drive circuit. This is a Q-switch pulse laser output device that attempts to achieve the above object by including excitation amount control means that receives a signal and causes an excitation lamp to emit light at an excitation amount that corresponds to the repetition frequency.

(Function) By providing such a means, the acousto-optic Q
When the switch is operated at an arbitrary repetition frequency, Q-switch pulsed laser light is output from the optical resonator every time the supply of high-frequency power to the acousto-optic Q-switch is stopped. At this time, the excitation amount control means receives a signal of the repetition frequency of the acousto-optic Q switch and causes the excitation lamp to emit light with an excitation amount corresponding to the repetition frequency.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Note that the same parts as in FIG. 4 are given the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 is a configuration diagram of a Q-switched laser output device. Q
The switch driving port circuit 10 causes the Q switch 8 to perform a switching operation and sends out a repetition frequency signal of this switching operation to the excitation amount control circuit 20.

The excitation amount control circuit 20 has a function of receiving a repetition frequency signal of the switching operation of the Q switch 8 and controlling the excitation lamp 34 to be lit at an excitation amount corresponding to the repetition frequency. Specifically, frequency/voltage conversion circuit 2
1. It has a limiter circuit 22 and an isolation amplifier 23. The frequency/voltage conversion circuit 21 has a function of receiving a repetitive frequency signal and converting the repetitive frequency signal into a voltage signal having a level proportional to the frequency.

The voltage signal output from this conversion circuit 21 is sent to a limiter circuit 22. This limiter circuit 22 has a function of limiting the voltage signal using upper and lower limit values. Here, when the repetition frequency of the Q-switched pulsed laser beam becomes less than the fluorescence lifetime (approximately 250 μs) of the solid-state laser medium 2, that is, approximately 4 kHz or less, the energy and peak value hardly change.

Therefore, the voltage signal is limited to a constant voltage lower limit value at a frequency of 4 kHz or less. Furthermore, since each excitation lamp 3.4 has a maximum rated current, it is necessary to limit the voltage signal to an upper voltage limit that does not exceed this rated current. Therefore, the voltage signal is limited to a certain voltage upper limit value at a repetition frequency considering the maximum rated current. The voltage signal limited by this limiter circuit 22 is passed through an insulating amplifier 23 to a variable power supply 30 for an excitation lamp.
is being sent to. This insulation amplifier 23 has its output terminal connected to the current control terminal of the excitation lamp variable power supply 30, and inputs a voltage signal to the current control terminal in a floating manner.

The excitation lamp variable power supply 30 has a function of receiving a voltage signal at a current control terminal and supplying a current proportional to the voltage signal to each excitation lamp 3.4.

Next, the operation of the apparatus configured as described above will be explained.

Power is supplied from the excitation lamp variable power supply 30 to each excitation lamp 3.
4, each excitation lamp light causes Nd:YA
The G solid-state laser medium 2 is excited. When in this state,
While high frequency power is supplied from the Q switch drive circuit 10 to the Q switch 8, the loss within the resonator 5 increases,
Laser oscillation stops. And Q switch drive circuit 1
When the supply of high frequency power from 0 to Q switch 8 is stopped,
The loss within the resonator 5 decreases rapidly and a laser oscillation state is achieved. Even while laser oscillation is stopped, the solid-state laser medium 2 continues to be excited, and a large population inversion occurs within the solid-state laser medium 2. Here, when the laser oscillation state suddenly occurs, stimulated emission occurs at once due to a large population inversion within the solid-state laser medium 2, and Q-switched pulsed laser light with a high peak is output from the output mirror 7. However, Q-switched pulsed laser light with a high peak is output at an arbitrary repetition frequency.

In this state, the Q switch drive circuit 10 sends out a switching operation repetition frequency signal. This repetition frequency signal is transmitted to the frequency/voltage conversion circuit 21 of the excitation amount control circuit 20.
sent to. This frequency/voltage conversion circuit 21 converts the repetitive frequency signal into a voltage signal corresponding to the frequency and outputs the voltage signal. This voltage signal is sent to a limiter circuit 22, and this limiter circuit 22 limits the voltage signal by each voltage upper and lower limit value and sends it out. The voltage signal that has passed through the limiter circuit 22 is applied to the current control terminal of the excitation lamp variable power supply 30 through the insulation amplifier 23. This results in
Each excitation lamp 3, 4 is supplied with a current proportional to the repetition frequency of the Q-switch 8. Thus, each excitation lamp 3, 4 emits light with an excitation amount proportional to the repetition frequency of the Q switch 8.

Here, as shown in FIG. 2, the excitation amount of these excitation lamps 3 and 4 is limited to a constant Q+ amount when the repetition frequency of the Q switch 8 is 4 kHz or less;
to XkHz is proportional to the repetition frequency, and above the repetition frequency XkHz, it is limited to a certain amount by Q2.

As a result, even if the repetition frequency of the Q-switched pulsed laser beam outputted from the output mirror 7 changes, the energy and peak output of one pulsed laser beam remain almost the same. Figure 3 (a), (b), and (c) each have a repetition frequency of 1.
The peaks of one-pulse laser light at kHz, 5kHz'z, and 10kHz are shown.

It can be seen from the figure that even if the repetition frequency changes, the energy of the one-pulse laser beam does not change. Above Nd:YA
When a solid-state laser medium 2 of G is used, its fluorescence lifetime is approximately 2
It is 50 μs. Therefore, the repetition frequency is 250 μs
If it is shorter than , the peak of the 1-pulse laser will decrease, but
By increasing the excitation amount of each excitation lamp 3, 4 as described above, the peak of the one-pulse laser becomes almost the same regardless of the repetition frequency.

In this way, in the above embodiment, when the Q switch is operated at an arbitrary repetition frequency to output a high peak pulse laser, the repetition frequency of the switching operation of the Q switch 8 is received, and the excitation amount is adjusted according to this repetition frequency. Since each of the excitation lamps 3 and 4 is made to emit light, pulsed laser light having the same peak and the same energy can be output even if the repetition frequency changes. Therefore, if applied to laser processing, even if the moving speed of the workpiece changes due to rough adjustment machining and fine adjustment machining, the number of pulsed laser beams irradiated per unit length can be made the same, and the energy of one pulsed laser beam can be kept the same. , the peak output can be made the same.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, Y
It can be applied not only to AG relays but also to glass lasers.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a Q-switched pulsed laser output device that can output a pulsed laser beam with a thermally constant energy peak output even if the number of repetitions of the pulsed laser beam changes. .

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining an embodiment of a Q-switched pulse laser output device according to the present invention,
FIG. 1 is a diagram showing the configuration, FIG. 2 is a diagram showing the excitation amount with respect to the number of repetitions, FIG. 3 is a diagram showing the peak of the pulsed laser for each number of repetitions, and FIG. 4 is a diagram showing the configuration of a conventional device. 1... Concentrating mirror, 2... Solid laser medium, 3, 4...
・Excitation lamp, 5... Resonator, 6... High reflection mirror 7
...Output mirror 10...Q switch drive circuit, 2
0... Excitation amount control circuit, 21... Frequency/voltage conversion circuit, 22... Limiter circuit, 23... Insulated amplifier, 30... Variable power supply for excitation lamp. Figure (a) ＃'ノML Question 1;Sa([. Figure (b) (c) Figure

Claims (1)

[Claims] A solid-state laser medium, an excitation lamp that excites the solid-state laser medium, an optical resonator arranged to face each other with the solid-state laser medium in between, and an acousto-optic Q switch arranged within the optical resonator. , a Q-switch drive circuit that switches this acousto-optic Q-switch at an arbitrary repetition frequency, and an excitation that receives a signal of a repetition frequency from this Q-switch drive circuit and causes the excitation lamp to emit light with an excitation amount corresponding to the repetition frequency. 1. A Q-switch pulse laser output device characterized by comprising: quantity control means.