JPS605578A - Output coupling mirror - Google Patents

Abstract

PURPOSE:To enable to freely alter the size of an output beam and the sectional shape only in the exchange of an output coupling mirror used for an optical resonator of a laser oscillator by forming a reflecting mirror having necessary reflecting mirror. CONSTITUTION:A laser tube 1 has at both ends a fully reflecting mirror 2 and an output coupling mirror 3, and an optical axis adjusting mechanism 4 is provided at one or both of the mirrors 2 and 3 at both ends of the tube 1 to construct to enable to adjust the optical axis, and an output beam 5 is emitted from the central hole. An output coupling mirror 31 forms a fully reflecting film 313 having substantially 100% of reflectivity on the surface of a percentage reflecting film 311 having the prescribed reflectivity, and the output beam is emitted only from the center having no film 313. The film 313 of the outer periphery formed on the inner surface of a resonator side reflects the beam in the resonator, and contributes to the amplification. Accordingly, an output higher than the conventional oscillator can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an output coupling mirror used in a laser oscillator.

Conventional Structures and Problems Generally, a resonator of a laser oscillator has two mirrors facing each other, and a laser medium and excitation means (by discharge or the like) in the mirrors. One of the two mirrors emits the laser beam';1
One is a total reflection mirror that reflects 00%, and the other is an output coupling mirror that has the optimum reflectance for the resonator (for example, 50%) and can take out a certain percentage (for example, 60%) of the 9 output. .

Conventionally, the output coupling mirror is made of a material that has a low absorption rate for the laser beam, such as Zn5e or GaAs, and the surface facing the inner surface of the optical resonator is made of, for example, PBS.

A reflective film having the necessary reflectance is formed by alternately laminating materials such as ZnS, and the outer surface is ThF'.

The antireflection film is formed of a substance such as Zn5e.

Since this output coupling mirror has a reflective film uniformly formed over the entire surface with a constant reflectance, the output beam obtained generally has a circular cross section with a thickness determined by the effective cross-sectional shape of the optical resonator. It was a target. In order to put a laser beam into practical use, it is necessary to obtain a beam outer diameter that matches the Canadian system.

For example, if the diameter of the output beam emitted from the oscillator exit is too large, the optical components and beam kite of the external optical system of the processing machine will become large.

In particular, optical components are expensive in proportion to the light-receiving area, which poses a practical problem. On the other hand, if the beam diameter is too small, the energy density per unit area will be high, which will also destroy optical components and cause problems in durability.

Another practical issue is the mode and cross-sectional shape of the obtained laser beam. The mode of the beam determines the energy distribution within the cross section, but since it is not directly related to the present invention, it will be omitted. Regarding the cross-sectional shape of the beam, the required cross-sectional shape is completely different depending on, for example, cutting and hardening. For cutting, a minute circular cross section on the surface of the workpiece is appropriate, but for hardening, it is better to have a rectangular cross section on the surface of the workpiece and a certain size to make the hardening effect more uniform. This is effective in reducing processing time.

In this way, the required beam diameter and cross-sectional shape of the beam differ depending on the configuration of the cannibal system and the processing purpose, but in the conventional configuration, the beam diameter and cross-sectional shape (circular) emitted from the laser oscillator are fixed. Therefore, the beam diameter or cross-sectional shape of the beam has to be changed using an external optical system within the processing machine. As means for deformation, combinations of concave-convex mirrors and lenses, adoption of optical parts of special shapes such as cylindrical mirrors and lenses, or combinations thereof have been invented and put into practical use.

Figure 1 shows a general configuration example of an optical resonator of a laser oscillator. ol is a laser tube, and there is a total reflection mirror section 2 and an output coupling mirror section 3 at both ends of the tube, and one or both of them has a light beam. It has an axis adjustment mechanism 4 and is configured to be able to adjust the optical axis. The figure shows an example in which the optical axis adjustment mechanism 4 is provided only in the output coupling mirror section 3. 5 indicates the output beam.

FIG. 2 is an enlarged detailed view of the conventional output coupling mirror shown in FIG. The output coupling mirror 31 is supported by the same holder 32,
An output beam 5 is emitted from the central hole. 33 and 34 are O-rings for airtightness and are pressed by nuts 35. dl is the beam diameter inside the resonator, and some percentage of this beam is obtained as the output beam 5 having a circular cross section, and the output beam diameter d2 is also configured to be equal to sod1.

FIG. 3 is an enlarged view of a conventional output coupling mirror 31.

In the figure, 310 is a base material, 311 is a reflective film having a reflectance of 8 tatami (hereinafter referred to as a percent reflective film), and 312 is an antireflection film. It is clear from this figure that the films on both sides of the conventional output coupling mirror were formed uniformly over the entire surface.

Conventionally, the cross-sectional shape of the laser beam is constant, so when changing the beam diameter or beam cross-sectional shape depending on the processing purpose, a special optical resonator is designed to match the shape. However, depending on the shape, it may be difficult to design or the output may be extremely reduced. Moreover, its biggest drawback was its lack of versatility.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention aims to reduce the burden of beam processing on the external optical system, and changes the dimensions and cross-sectional shape of the beam itself emitted from a laser oscillator using only an output coupling mirror. It provides the means.

Structure of the Invention In order to achieve the above object, the output coupling mirror of the present invention comprises an anti-reflection film provided on one surface of the base material, a reflective film having a necessary reflectance provided on the ground surface of the scent material, and the entire surface of the base material. With this configuration, which is composed of a combination of a reflective film having the necessary reflectance and a total reflection film to obtain the desired beam size and shape, it is possible to use a general purpose laser oscillator. A high output beam with the required dimensions and cross-sectional shape can be easily obtained by simply replacing the output coupling mirror.

DESCRIPTION OF THE EMBODIMENT FIG. 4 shows an output coupling mirror in an embodiment of the present invention,
A total reflection film 313 having a reflectance of R100 is formed on the surface of a percent reflection film 3110 having a predetermined reflectance, and the output beam is emitted only from the central portion where the total reflection film 313 is not provided. Total reflection film 3 on the outer periphery formed on the inner surface on the resonator side
13 reflects the intra-cavity beam and contributes to amplification, so a higher output than a conventional oscillator can be obtained. (In the conventional oscillator, the part on the outer periphery where the total reflection film 313 is provided is simply used as an output coupling mirror receiving part by the output coupling mirror holder 3, and is a surface unrelated to oscillation amplification.) FIG. 5 is a diagram showing a state in which the output coupling mirror of the present invention is attached to a resonator. The same parts as in FIG. 1 are given the same numbers and their explanations are omitted.

In this configuration, a total reflection film 313 is provided on the outer periphery of the laser tube side surface of the output coupling mirror 31, and this part is also designed to harm the laser oscillation, and in addition to obtaining a beam of the desired size and shape, The inner diameter d3 can be made larger than the conventional inner diameter d1, and the reflective surface can be used effectively. Further, when the output beam 5 having the same dimension d2 as the conventional one is taken out, high output can be generated. Furthermore, such a configuration has the advantage that the resonator can be designed with sufficient margin.

FIG. 6 shows another embodiment of the present invention, which is a preferred embodiment for obtaining a beam 314 with a rectangular cross section that is convenient for hardening. This is the same as the previous embodiment except that a total reflection film 313 is provided except for the central rectangular portion. Assuming that the length of the long side of this beam 314 is l, by scanning the workpiece or the beam 314 in the direction X perpendicular to the long side, hardening of the width β can be performed in one scan, so the processing time is shortened. Since the beam is dispersed, uniform hardening is possible.

FIG. 7 shows an example in which the percent reflection film 311 below the total reflection film 311 is removed and the percent reflection film 311 is formed only in the area through which the output beam passes, reducing manufacturing costs and increasing the adhesion strength of the total reflection film 313 and cooling efficiency. It helps to increase.

Effects of the Invention As described above, the present invention provides an output coupling mirror for use in an optical resonator of a laser oscillator, in which a reflective film having a necessary reflectance has a desired size and shape, and the rest is covered with a total reflection film. You will get the following advantages:

■ The dimensions and cross-sectional shape of the output beam from the laser oscillator can be freely changed to match the cutting system and processing purpose simply by replacing the output coupling mirror.

■ High output can be obtained.

■ The cost of the device can be reduced because the external optical system outside the laser oscillator can be simplified.

■ The versatility of the laser oscillator increases and its applications can be expanded.

■ There is a total reflection film on the inner surface, so even beginners are less likely to confuse the inner and outer surfaces.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a general example of an optical resonator, Fig. 2 is an enlarged sectional view of its output coupling mirror, and Fig. 3 is a conventional output coupling mirror, where a is a front view and b is a sectional view. , C is a rear view. FIG. 4 shows an output coupling mirror in one embodiment of the present invention, in which a is a front view and b is a front view. FIG. 6 is a cross-sectional view showing the output coupling mirror of the present invention attached to a holder.
The figures show an output coupling mirror according to another embodiment of the present invention, in which a is a front view, b is a sectional view, and C is a diagram showing an output beam. FIG. 7 is a sectional view showing another embodiment of the output coupling mirror of the present invention. 1... Laser tube, 2... Total reflection mirror section, 3
...Output coupling mirror section, 4...Optical axis adjustment mechanism, 5...Output beam, 31...Output coupling mirror, 32... Output coupling mirror holder, 33.34
...O-ring for airtightness, 310...Base material,
311... Percent reflective film, 312...
・Anti-reflection film, 313... Total reflection film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 31 /& J (1> ) βl (c) (α2 immersion/3 (b+ Figure 5 6 Figure 2) Figure 7 57 no ρ5 King (C) 7/?

Claims (3)

[Claims] (1) Consisting of a base material, an anti-reflection film provided on one surface of the base material, a reflective film with a necessary reflectance and a total reflection film provided on the ground surface of the moon, and the necessary reflection 1. An output coupling mirror comprising a combination of a reflective film having a reflection ratio and a total reflection film so as to obtain a desired beam size and shape. (2) A total reflection mirror is formed by leaving a desired beam size and shape on a reflective film having a necessary reflectance formed on the entire ground surface of the base material.
Output coupling mirror as described in section. (3) A reflective film having a necessary reflectance for a desired beam size and shape is formed on the ground surface of the base material, and the other base material surface is covered with a total reflection mirror. Output coupling mirror 0 described in section