JPS61226985A - Gas laser oscillator - Google Patents

Abstract

PURPOSE:To obtain laser beams having high focusing properties without using a coupling mirror by mounting an optical resonator in which a shape acquired by turning one-side cross section on the same side containing the central axes of a concave mirror and a convex mirror while employing the tangent of a concave-mirror side cross section on the side reverse to the side being in contact with the central axes as the axis of rotation is constituted as a reflecting mirror. CONSTITUTION:A confocal type unstable type resonator is constituted by a concave mirror 14 and a convex mirror 15, reflecting surfaces thereof are faced oppositely and optical axes thereof are conformed to an axis 13, having a diameter smaller than the concave mirror. The concave mirror 14 uses a point 01 on the axis 13 as the center of curvature, and employs a distance R1 up to the point O1 from the center of the reflecting surface as the radius of curvature, and the convex mirror 15 uses a point O2 on the axis 13 as the center of curvature, and employs a distance R2 up to the point O2 from the center of the reflecting surface as the radius of curvature. The concave mirror 14 and the convex mirror 15 are arranged while using a point F on the axis as a confocal point. All of beams proceeding toward the convex mirror 15 from the concave mirror 14 in beams in an optical resonator move forward in parallel with the axis 13, and all of beams reflected by the convex mirror 15 return to the concave mirror 14 on a straight line passing through the confocal point F. Consequently, beams gradually get away from the axis, and beams are amplified during that time and outputted as laser beams La at an annular mode from the outside of the convex mirror. Accordingly, a reflecting mirror need not be fitted.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a gas laser oscillation device.

[Technical background of the invention and its problems]

Among gas laser oscillation devices, many devices with a relatively high output of IKW or higher use an unstable resonator. As is well known, as shown in Figure 7, this unstable resonator consists of a concave mirror (1), which is a total reflection mirror, and a convex mirror (2), which is also a total reflection mirror and has a smaller diameter than the concave mirror (1), on the same axis. They are constructed with their reflective surfaces facing each other. Near the convex mirror (2) between these, a coupling mirror (4) with a passage hole (3) in the center has its reflecting surface facing the concave mirror (1) side (c), so that the light from the concave mirror (1) The transmission hole (3) has a size that allows almost all of the light from the convex mirror (2) to pass through, and in the above arrangement, the resonance The hole is circular when viewed from the axial direction.As can be seen from the above structure, this type of unstable resonator emits a laser beam (L) in a mode with an annular cross-sectional intensity distribution. is output.The convergence of this laser beam (L) is determined by the magnification rate M (laser beam (L)
The value of b/a when the inner diameter is a and the outer diameter is b). The intensity distribution in the far field (sufficiently far away or at the focal point of the condensing lens) depending on the value of magnification M is as shown in Figure 8, M-■, that is, when the cross section is circular, the intensity is highest in the center and the focus is good. is good. However, as mentioned above, only an annular laser beam can be obtained from an unstable resonator, and the value of the magnification factor M is limited by the gain of the laser medium, etc., and in reality, the limit is about M = 3. It had become. Furthermore, since the coupling mirror (4) is essential, the structure becomes somewhat complicated.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned disadvantages, and it is possible to obtain a laser beam that is output from a circular aperture with a wavefront of the same phase and has a high focusing property in the far field without using a coupling mirror. The purpose is to provide a laser oscillation device.

[Summary of the Invention] One side cross section of the concave mirror and the convex mirror constituting the optical resonator are rotated on the same side including the central axis, with the tangent of the side in contact with the central axis and the concave mirror side cross section on the opposite side as the rotation axis. Each of the obtained shapes is provided with an optical resonator configured as a reflecting mirror.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on drawings showing examples. In FIG. 1, Ql) is an annular mirror having a circular passage hole (1), and is provided on the mirror 00 with its reflective surfaces coaxially facing each other. and annular mirror 0
An optical resonator is constituted by the sides, and the arrangement of each and the formation of each reflective surface will be explained below with reference to FIGS. 2 and 3.

That is, FIG. 2 shows a confocal unstable resonator, in which a concave mirror fi4) and a concave mirror fi4) are provided with their reflective surfaces facing each other and their optical axes aligned with the axis 03).
1 and a convex mirror 09 with a diameter smaller than 1. Concave mirror O
a has the center of curvature at point 01 on the axis (■■, and the radius of curvature is the distance R1 from the center of the reflecting surface to point 01. On the other hand, the convex mirror 051 has the center of curvature at point 02 on the axis) , the distance R2 from the center of the reflecting surface to point 02 is the radius of curvature.These concave mirror αa and convex mirror (c)
are arranged with point F on the axis as a confocal point. The light inside the optical resonator with such a configuration is transmitted from the concave mirror a to the convex mirror Q.
All light directed toward 51 travels parallel to the axis 0th floor, and all light reflected by convex mirror a returns toward concave mirror α on a straight line passing through confocal F.

Therefore, the light gradually moves away from the axis 0 fathom, but during this time the light is amplified and output from the outside of the convex mirror housing 9 as annular mode laser light (La).

Based on the above confocal optical resonator, the reflecting surface of the embodiment shown in FIG. 1 is fabricated as follows.

That is, in FIG. 3, aO1αη is the cross section of, for example, the lower half concave mirror I and convex mirror (IQ) in the figure from the axis line in FIG. ), the concave mirror OQ and the annular convex mirror side are formed in the positional relationship shown in FIG.

In the optical resonator shown in FIG. 1 above, all the light directed from the mirror a1 to the ring-shaped convex mirror 0υ is directed along the axis α in this configuration.
It moves parallel to l (that is, axis α). and,
These lights are reflected on the annular convex mirror side and return to the concave mirror α0 on a straight line passing through the point Fl or F2 corresponding to the confocal F. Therefore, the light gradually approaches the axis (11), but during this time the light is amplified and is finally output as a circular laser beam (Lb) from the passage hole a21 of the annular convex mirror ([1). Figure 4 shows the intensity distributions of the light (Lb) and the ring-shaped laser beam (L) after focusing.As is clear from this figure, the intensity distribution of the ring-shaped laser beam (L) ), it can be seen that the laser beam (Lb) with a higher intensity shows better convergence than the laser beam (Lb).

In the above embodiment, the optical resonator is constructed with two mirrors, but it may also be constructed with one or more folding mirrors Qη provided between them as shown in FIGS. 5 and 6. .

〔Effect of the invention〕

As detailed above, it is now possible to output a circular laser beam with good focusing, and for example, when cutting or cutting out various patterns, the cutting width becomes smaller.
In addition to improving accuracy and yield, it is now possible to process thicker materials with the same output. However, in the welding process, it was possible to weld deep into the weld, further improving weld strength. In addition to obtaining great practical advantages in laser processing, the optical valve oscillator itself has a simple structure as a coupling mirror is not required, and the output is shifted 90 degrees from the resonance axis like a coupling mirror. Therefore, there is no need to install a reflecting mirror coaxially or parallel to the resonant axis as in the conventional case.

[Brief explanation of drawings]

4 is an energy distribution diagram of a laser beam, FIGS. 5 and 6 are sectional views of main parts showing other embodiments of the present invention, FIG. 7 is a sectional view of main parts showing a conventional example, and FIG. The figure is a diagram showing changes in intensity distribution depending on the magnification ratio M. 0 [...Concave mirror, (11)...Annular convex mirror, α
One...passing hole, u! J... Axis line. Agent Patent attorney Kensuke Chika (and 1 other person) Figure 5 Figure 7 Angle φ between upper A (Relative A 1)

Claims (1)

[Claims] All or part of a one-sided figure whose side is the central axis in a cross section including the central axis of the concave mirror that forms one side of the unstable resonator, with a straight line passing through a part of the above figure and parallel to the central axis as the rotation axis. A reflecting mirror whose reflecting surface corresponds to the reflecting surface of the concave mirror which has a three-dimensional shape obtained when it rotates once, and a convex mirror which forms the other side of the resonator and is located at a position constituting an unstable resonator. The side corresponding to the reflective surface of the convex mirror of the three-dimensional shape obtained when all or part of the one-sided figure whose side is the central axis in a cross section including the central axis is rotated once around the rotation axis. A gas laser oscillator characterized by comprising an optical resonator configured with an annular reflecting mirror whose surface is a reflective surface.