JPS6094786A - Q switch solid laser oscillator - Google Patents

Abstract

PURPOSE:To enable to accelerate the laser machining and to improve the machining quality by forming the outer surface except that opposed to an exciting lamp of a laser rod on the light scattering surface, thereby outputting a pulse laser stably to high frequency range. CONSTITUTION:A Q switch laser oscillator has a light collecting reflecting mirror 1 of inner elliptical shape, a laser rod 2 and an exciting lamp 3 mounted in parallel within the mirror 1, a body 4 for watertightly containing structures, a resonator mirror formed of a high reflection mirror 5 and a partial reflection mirror 6 and provided on the axis of the rod between the rods 2, a supersonic Q switch element 9 formed of a molten quartz cell 7 and a supersonic transducer 8 and provided on an axis between the mirror 6 and the rod 2. The outer surface opposed to the lamp 3 of the rod 2 is formed smoothly, but a light scattering surface is formed on the outer surface which is not opposed to the smooth surface.

Description

[Detailed description of the invention] [Technical background of the invention and its problems] Conventionally, in a solid-state laser oscillation device such as a Nd; A Q-switch was installed inside the device to obtain high-speed repeating Q-switch pulses, and it was put into practical use for cutting and heat treatment.

Widely used for drilling, scribing, trimming, etc. #f In applications using Q-switch pulses for heat treatment, it is necessary to harden the surface, form an amorphous layer, anneal the surface of the semiconductor, or form surface defects for gettering on the back surface of the semiconductor. It has many uses such as.

In these methods, the pulse output is focused and irradiated using a lens, and each irradiation point is often irradiated without overlapping each other. At this time, if the intensity of the laser pulse output varies from shot to shot, this may occur if the laser pulse output is out of the optimum condition range for the laser irradiation. In this way, for applications that require stability for each pulse, it is necessary to ensure stability of output power for each pulse. Conventionally, when the pulse repetition rate is increased, even if the switching speed of the Q switch element is kept constant, the pulse rise time differs every other pulse, and the peak output also differs every pulse, which is inconvenient for laser processing. A phenomenon occurred. In order to avoid this, it is necessary to reduce the pulse repetition rate to, for example, 104 Hz or less, and limit it to low-speed repetition conditions where output stability is good.Also, to improve stability under high-speed repetition conditions, the output waveform of the Q switch must be changed. While observing this, perform the optical axis alignment of the resonator mirror so that the output pulse becomes a constant output by removing it from the conditions that yield the maximum average output, so that the pulse output fluctuates less with each pulse. We are choosing conditions. Under such optical axis alignment, the average output is reduced by 20 to 30% from the output under alignment conditions that provide the maximum average output. This is disadvantageous because it involves a decrease in oscillation efficiency. In addition, the amount of displacement that is removed from the alignment maximum output condition must be readjusted by changing the input power of the excitation lamp.
When a device that implements this method is used industrially, there are disadvantages in terms of thread binding. Another drawback is that the laser oscillation output pattern has inconvenient characteristics when used for processing, such as an elliptical laser beam pattern being obtained from a laser rod with a circular cross section.

[Purpose of the invention]

It is an object of the present invention to provide a Q-switched solid-state laser oscillation device that stably outputs a pulsed laser up to a high frequency range and achieves faster laser processing and improved processing quality.

[Summary of the invention]

In devices that perform laser oscillation by optically exciting a laser rod from one direction, the outer surface of the laser rod is made to have different surface conditions between the surface that faces the excitation lamp and the surface that does not, especially when facing the excitation lamp. The outer surface other than the outer surface is formed as a light scattering surface to stabilize the output of the pulsed laser up to a high frequency range.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on drawings showing embodiments.

FIG. 1 shows a schematic configuration of a Q-switched laser oscillation device according to the present invention, which is composed of the following elements. That is, a condensing reflector (1) whose inner surface is shaped like an elliptical cylinder, and a laser rod (2) installed in parallel inside this condensing reflector.
and an excitation lamp (3), a main body (4) that watertightly houses each of the components mentioned above, a high-intensity mirror (5), and a partial reflector (6). 2) between and on the axis of this laser rod, and a fused silica cell (force and ultrasonic transducer (8)).
) and a high reflection fJ8 (61) and an ultrasonic Q-switch element (9) provided on the axis between the laser rod (2) and the laser rod (2).

(10a) and (10b) are glass pipes surrounding the laser rod (2) and the excitation lamp (3);
), (tlb) connects the laser rod (2) with the O ring (1
The holding cylinder supported via the cylinder 7J, (L tank, α tank) are the supply port and drain port for guiding and discharging the cooling liquid from the main body (4) to the condensing reflector (1). A driver (L) that controls the operation of the ultrasonic Q-switch element (9)
is the laser output.

By the way, the outer surface of the laser rod (2) is not formed into a uniform surface, but is formed into the following surface. That is, the outer surface facing the two excitation tubes (3) is a smooth surface, but the light scattering surface a0 is formed on the outer surface that is not facing the two excitation tubes (3).

In the above configuration, under the circulation of coolant.

While optically exciting the laser rod (2), turn on high frequency power to the ultrasonic transducer (8) using the driver t+S.

The laser pulse output is produced by turning off and performing a high-speed repetitive Q-switch pulse oscillation operation.

When the stability (S) of this pulse output is measured by changing the frequency of the above-mentioned high-frequency power, the result is a curve A in FIG. 2. Note that curve B in the same figure shows the stability achieved by the conventional oscillation device. This stability (S) is determined by oscillating the drive high frequency output (17...) from the drive power (Pup) of the transducer with a period T, as shown in Figure 3 (a) and (b), and outputting High peak value (Pl) of pulses (18...) and low output pulses (19...).

It is expressed from the ratio (P/P1) to the peak value (P, ). As mentioned above, conventionally P! I observed the oscillation output waveform in order to bring /P1 closer to 1, so I manipulated one or both of the resonator mirrors and adjusted it to deviate from the conditions that yielded the maximum average output, but the average output was 20. This resulted in a condition that was ~30% lower, resulting in a decrease in oscillation efficiency. On the other hand, regarding the pulse output that forms the basis of the above curved line, it has been found that the alignment of the resonator mirror is a condition that allows the average output to reach its maximum value.

In the above example, the light reflecting mirror has an elliptical cylindrical inner surface, but it is not limited to this, and may be a spheroid (prolate type condensing reflector) or a spherical reflecting mirror. The present invention may be applied to a device such as a mirror that performs optical excitation asymmetrically with respect to the axis of the laser rod to constitute an oscillator.

〔Effect of the invention〕

Q-switched pulses with high frequency operation can be obtained as a stable output for welding laser light.

When applied to various types of processing such as heat treatment, the finished product is stabilized and the processing speed is also improved. Furthermore, laser beam alignment can be done simply by adjusting the alignment of the resonator mirror to the maximum output power while measuring the average output power with a power meter without observing the output waveform.
A practically advantageous oscillation device was realized.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the present invention, Fig. 2 is a graph showing measurement results of pulse stability against frequency changes, Fig. 3(a) is a pulse waveform diagram, b) is a waveform diagram of the peak output. (1)...Condensing reflector, (2)...Laser rod. (3)...excitation lamp, (4)...main body. (5)... Partially reflective mirror, (6)... Highly reflective mirror. (9)...Ultrasonic Q-switch element, IIG)...Light scattering surface.

Claims (1)

[Claims] A condensing reflector surrounding a laser rod installed in parallel and an excitation lamp for exciting the laser rod, a cooling means for cooling at least the laser rod, and a Q switch provided on an axial extension of the laser rod. A Q-switch solid-state laser oscillation device comprising a Q-switch and a resonator mirror provided between the laser rod,
The laser rod is characterized in that an outer surface other than the surface facing the excitation lamp is formed as a light scattering surface.
Switched solid-state laser oscillator.