JPH01270368A - Laser device - Google Patents

Abstract

PURPOSE:To obtain a laser beam high in quality at a low cost by a method wherein a feedback mirror, whose central part is of a total reflection or a partial reflection type, is provided to a laser beam takeout side, an outlet mirror whose outside periphery is formed of a non-reflective part is installed, and a magnifying mirror is provided facing the feedback mirror. CONSTITUTION:A laser beam 23a reflected and magnified by a magnifying mirror 20 is amplified through a laser medium 3, and the peripheral part of the layer beam 23a is taken outside as a ring-shaped beam 24 through the outside periphery of a feedback mirror 22 penetrating a non-reflective coating film 5 of an outlet mirror 21. On the other hand, a laser beam 23 totally reflected by the feedback mirror 22 is amplified again by the laser medium 3 and moreover reflected and magnified by the magnifying mirror 20 to be the laser beam 23a, and thus the ringshaped laser beam 24 is projected outside at each time when the laser beam 23a is made to reciprocate inside a laser resonator composed of the magnifying mirror 20 and the outlet mirror 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laser device, and particularly to improving beam quality in a high-output laser device.

[Prior art] Figure 11 shows, for example, the Laser Handbook (Laser Handbook).
Handbook 1979', North-Holl
FIG. 2 is an explanatory diagram showing an example of a conventional laser device having an unstable resonator, as described in J.D. and Publishing Company. In the figure, (1) is a feedback mirror made of a total reflection concave mirror, (2) is a magnifying mirror made of a total reflection convex mirror located opposite the feedback mirror (1), and both mirrors (1) are
, (2) constitutes a so-called unstable resonator.

(3) is a laser medium, for example, in the case of a gas laser such as a CO2 laser, a gas medium excited by discharge etc.
In the case of a solid-state laser such as a YAG laser, the laser is a glass medium excited by a flash lamp or the like. (4) is a wind mirror, (5) is a non-reflective coat ink film provided on the surface of the wind mirror (4), and (6) is a box body that covers the periphery of the resonator.

In addition, (7) is a laser beam generated in a resonator composed of a feedback mirror (1) and a magnifying mirror (2), and (8) is a laser beam generated from the periphery of the magnifying mirror (2) to the box body (6).
This is a laser beam taken out to the outside.

Next, the operation will be explained. Feedback mirror (1
) and the magnifying mirror (2) constitute a so-called unstable resonator, and the laser beam (7) reflected and magnified by the magnifying mirror (2) is amplified by the laser medium (3), and the feedback mirror (1) ) creates a parallel beam (
7a), is reflected onto the magnifying mirror (2) and the periphery of the magnifying mirror (2), and becomes a ring-shaped laser beam (8) that is transmitted from the wind mirror (4) to the box body (
8) is taken out to the outside. The ring-shaped laser beam (8) extracted in this way is obtained with almost the same phase, so by focusing it with a lens etc., it becomes a medium-high laser beam, which can be used to efficiently cut and weld iron plates etc. I can do it. Note that the degree of convergence of this laser beam is determined by the ring shape (Magn1f'1
cation f'acter), and the laser beam with a large M value, that is, the laser beam extracted more centrally, is better focused.

[Problems to be Solved by the Invention] According to the conventional laser device configured as described above, the M value must be increased in order to obtain a laser beam with good convergence. However, to increase the M value, the magnifying mirror (2)
For example, YA
Taking the G laser as an example, the cross-sectional diameter of the laser medium (3) is about 8 mm, and the M value to obtain a laser beam (8) with sufficient quality for laser processing is 3 or more, so a magnifying mirror is used. The outer diameter of (2) is extremely small, 2.8 mm or less, and it is extremely difficult to form this with precision.

Therefore, the M value could not be increased, and the quality of the laser beam taken out of the box (6) was therefore poor.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a laser device that can generate a high-quality laser beam.

[Means for Solving the Problems] A laser device according to the present invention has a total reflection type or partial reflection type feedback mirror at the center of the inner surface, and a non-reflection portion on the outer periphery of the exit mirror. A total reflection magnifying mirror is placed on the extraction side and facing the feedback mirror.

Further, a phase difference compensating means is provided on the exit mirror or the outside thereof.

Furthermore, in each of these laser devices, the outer shape of the laser medium is formed to match the outer shape of the laser beam within the resonator.

[Function] When a total reflection type feedback mirror is used, a ring-shaped laser beam can be extracted from around the feedback mirror.

In addition, if a partially reflective feedback mirror is used, it is possible to extract the stuck laser beam.
Furthermore, by providing a phase difference compensating means, it is possible to eliminate the phase difference between the center and the outer circumference of the extracted laser beam.

Furthermore, the oscillation efficiency is improved by matching the outer shape of the laser medium of each of these laser devices to the outer shape of the laser beam within the resonator.

[Embodiment of the Invention] FIG. 1 is an explanatory diagram of an embodiment of the invention. Note that the same or equivalent parts as in the conventional example shown in FIG. 11 are given the same reference numerals, and their explanation will be omitted.

In the figure, (20) is a total reflection type magnifying mirror made of a convex mirror, and (21) is an exit mirror made of a concave mirror whose outer surface has a smaller curvature than its inner surface.

(22) is a total reflection type feedback mirror provided at the center of the inner surface of the exit mirror (21), (5) is a non-reflection coating film provided on its outer periphery, and (23) is a feedback mirror (22) and a magnifying mirror ( (20) is a laser beam generated in a resonator formed by (23a), a laser beam enlarged and reflected by a magnifying mirror (20), and (23a).
24) is a ring-shaped laser beam taken out to the outside of the box (6).

A detailed explanation of the present invention configured as above is as follows. The laser beam (23a) reflected and expanded by the magnifying mirror (20) is amplified by the laser medium (3), and the peripheral part of the laser beam (23a) extends from the outer periphery of the feedback mirror (22) to the empty space of the exit mirror (21). The laser beam is extracted to the outside as a ring-shaped laser beam (24) through the reflective coating film (5).

On the other hand, the laser beam (23) that has been totally reflected by the feedback mirror (22) is amplified again by the laser medium (3), and is further reflected and expanded by the magnifying mirror (20) to become a laser beam (23a). In this way, the laser beam (Lla) emits a ring-shaped laser beam (8) to the outside each time it reciprocates between the laser resonator consisting of the magnifying mirror (20) and the exit mirror (21).

In this embodiment, since the curvature of the outer surface of the exit mirror (21) is smaller than the curvature of the inner surface, the exit mirror (21) has a smaller curvature than the inner surface.
The laser beam (24) passing through 1) is generally parallel light that is easy to use. Therefore, the magnifying mirror (20)
Even if the magnification ratio of the magnifying mirror (20) is increased, the problems described in the conventional art shown in FIG. 11 can be solved.

FIG. 2 is an explanatory diagram showing another embodiment of the present invention. In this embodiment, the laser medium (3) of the embodiment shown in FIG. 1 is formed to have a trapezoidal cross section to match the external shape of the laser beam (23a), thereby improving the oscillation efficiency. For example, in the case of a YAG laser, such a laser medium (3a) can be formed by tapering a crystal rod.

FIG. 3 is an explanatory diagram showing still another embodiment of the present invention. In the embodiments shown in FIGS. 1 and 2, a convex mirror was used as the magnifying mirror (20), but in this embodiment, a concave magnifying mirror (20a) is used to focus and expand the laser beam within the resonator. That's how it is.

Note that the outer shape of the laser medium (3) shown in FIG. 3 can also be arranged in accordance with the outer shape of the laser beam (23b) inside the resonator, as shown in FIG. That is,
The laser medium (3) is further expanded toward the exit mirror (21), and the convergence point of the laser beam (23b) is focused on the laser medium (3).
b), or as shown in FIG.
21) side, and may have a Y-shaped cross section along the path of the laser beam (23b).

FIG. 6 is an explanatory diagram showing another embodiment of the present invention. (3
d) is a laser medium formed with a trapezoidal cross section along the path of the laser beam (23d), and (22a) is an exit mirror (22a).
1) a feedback mirror with a partial reflection function provided at the center of the inner surface; (5) a non-reflection coating film formed on the outer periphery of the feedback mirror (22a);
(24a) is a hollow laser beam emitted from the laser device.

The operation of this embodiment configured as described above will be explained as follows. The laser beam (23d) expanded by the magnifying mirror (20) is amplified by the laser medium (3d), and a part of the central part passes through the feedback mirror (22a) of the exit mirror (21), and the entire peripheral part passes through the feedback mirror (22a) of the exit mirror (21). is the non-reflection coating film (5) of the exit mirror (21)
The two are combined to form a solid high-quality laser beam (24a). On the other hand, the laser beam (23b) partially reflected by the feedback mirror (22a) is amplified again by the laser medium (3d), and further reflected and expanded by the magnifying mirror (20).

In this way, the laser beam (23b) is transmitted through the magnifying mirror (
20a) and the exit mirror (21), the high-quality laser beam (24a) is fed from the rearview mirror (22a) and its surroundings.
is emitted to the outside. In addition, in this embodiment, the exit mirror (2
Since the curvature of the outer surface of 1) is smaller than the curvature of the inner surface, the laser beam (24a) passing through the exit mirror (21)
) is parallel light that is generally easy to use.

As described above, in this embodiment, since the laser beam (24a) to be extracted is in the form of a block, the so-called M value becomes infinite, and an ideal laser beam is obtained. However, when the laser beam makes only a few round trips within the resonator, such as with a pulsed laser, the larger the M value, the more stable the laser beam will be after a shorter number of round trips. many.

In the above explanation (Fig. 6), the exit mirror (21) is coated with a partially reflective film to provide a partially reflective feedback mirror (
22a), but as shown in FIG. 7, a partially reflective feedback mirror (22b) may be formed from an uncoated portion.

FIG. 8 is an explanatory diagram showing still another embodiment of the present invention. In the embodiment of FIG. 6, between the laser beam (23b) passing through the feedback mirror (22a) on the inner surface of the exit mirror <21) and the laser beam (23d) passing through the non-reflection coating film (5), The phase difference is generally small and has not been a problem, but the effect can be further enhanced by providing a means to cancel it. As this means, a feedback mirror (22a) shown in FIG.
The laser beam (
23d) and <28b) can be canceled so that the laser beam (24a) has the same phase. In this embodiment (Fig. 8), a concave step (28) is provided on the outer surface of the exit mirror (21) to create a difference in the optical path difference within the rear mirror (2), thereby canceling out the phase difference. . Incidentally, as shown in FIG. 9, a phase compensation mirror (29) having a concave step (28a) having the same effect as the outer surface of the exit mirror (2) may be provided separately.

Further, as for the magnifying mirror, only a convex magnifying mirror is shown, but a concave mirror (20a) may also be used as shown in FIG. 1O.

In the above explanation, the case where the exit mirror and the wind mirror are integrated is shown. However, as in the past, an exit mirror made of a concave mirror or a convex mirror with partial transmittance may be provided on the wind mirror surface. good.

[Effects of the Invention] As is clear from the above description, the present invention provides a total reflection type or partial reflection type feedback mirror in the center on the laser beam extraction side, and a non-reflection part is formed on the outer periphery of the feedback mirror. Since an exit mirror is provided and a magnifying mirror is placed opposite the feedback mirror, the magnification ratio can be increased without any difficulty in manufacturing the mirror, and a high-quality laser beam can be obtained at a low cost. can.

In addition, when a partially reflective feedback mirror is used, a better quality laser beam can be obtained by providing a phase difference compensation means, and the outer shape of the laser medium of each of these laser devices can be adjusted to By matching the external shape of the laser beam, the oscillation efficiency can be improved, and the effects of implementation are significant.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing another embodiment of the invention, and FIGS. 3, 4, and 5 are further embodiments of the present invention. Explanatory diagrams showing, Figures 6 and 7
The figure is an explanatory diagram showing another embodiment of the present invention, FIGS. 8, 9, and 10 are explanatory diagrams showing still another embodiment of the present invention,
FIG. 11 is an explanatory diagram showing an example of a conventional laser device. (3), (3a), (3b), (3c), (ad)-・
・Laser medium, (5)... Non-reflection coating film, (
20), (20a)...Magnifying mirror, (21")-...
・Exit mirror, (22), (22a), (22
b) - Feedback mirror, (23), (2
3a), (23b), (23c). (23d), (24), (24a) --- Laser beam, (28), (28a) --- Stepped portion, (
29)...Phase compensation mirror. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a laser device that uses an unstable resonator consisting of a magnifying mirror and a feedback mirror and takes out a laser beam amplified by a laser medium, on the extraction side of the laser beam, there is a total reflection type or partial reflection type at the center of the inner surface. A laser device characterized in that an exit mirror having a reflective feedback mirror and a non-reflective portion formed on the outer periphery is disposed, and a total reflection magnifying mirror is disposed opposite to the feedback mirror. . (2) The laser device according to claim (1), further comprising phase difference compensating means provided on the exit mirror or outside thereof. (3) The laser device according to claim (1) or (2), wherein the outer shape of the laser medium is formed to match the outer shape of the laser beam within the resonator.