JPH07105545B2 - Laser equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device, and more particularly to a resonator thereof.

[0002]

2. Description of the Related Art FIG. 6 shows a laser handbook (La, for example).
ser Handbook 1979. North-
Holland Publishing Compan
It is a schematic diagram of the laser device which has the conventional unstable resonator described in y). In the figure, reference numeral 1 is a collimating mirror made of a concave mirror, 2 is a magnifying mirror made of a convex mirror arranged to face the collimating mirror 1, and both mirrors 1 and 2 are constituted by total reflection mirrors. Reference numeral 3 denotes a laser medium, which is a gas medium excited by discharge or the like in the case of a gas laser such as a CO ₂ laser, and a glass medium excited by a flash lamp or the like in the case of a fixed laser such as a YAG laser. Reference numeral 4 is a wind mirror, 5 is a non-reflective coating film applied on the surface of the wind mirror 4, 6 is a box covering the surroundings, and 7 is generated in a resonator constituted by the collimating mirror 1 and the magnifying mirror 2. A laser beam 8 is a laser beam extracted from the peripheral portion of the magnifying mirror 2.

In the above laser device, the collimating 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 collimated. The collimated beam 7a is collimated by the mirror 1, is reflected on the magnifying mirror 2 and the peripheral portion of the magnifying mirror 2, and is taken out from the wind mirror 4 as a ring-shaped beam. Extracted ring-shaped laser beam 8
Are obtained in almost the same phase, so that they are focused by a lens or the like to form a middle-high laser beam 8, and cutting and welding of an iron plate or the like can be efficiently performed.

The degree of focusing is determined by the ratio of the inner diameter and the outer shape of the extracted ring-shaped laser beam 8 (M value (M value (M
Therefore, the larger the M value, that is, the more the beam taken out in the middle, the better the focus. However, when the M value is increased, the oscillation efficiency is significantly deteriorated. Therefore, the upper limit of the M value that is industrially practically used is about 2.

[0005]

Since the conventional laser device is constructed as described above, if the M value is increased to improve the condensing characteristics, the oscillation efficiency is deteriorated. Therefore, the M value is practically used. However, there was a problem that it could not be raised to near infinity at which the maximum condensing performance was obtained. Further, since the wind mirror 4 is non-uniformly overheated by the ring-shaped laser beam 8, uneven internal stress is generated and the phase distribution of the passing laser beam 8 is destroyed, and the condensing performance is deteriorated. was there. The present invention has been made to solve the above problems, and an object of the present invention is to obtain a laser device that can extract a high-quality laser beam with a cheaper configuration.

[0006]

According to another aspect of the present invention, there is provided a laser device having an exit mirror having a partially transmissive portion in the center and a non-reflective portion in the peripheral portion, and an outer surface having a radius of curvature smaller than that of an inner surface. And a resonator provided with the exit mirror, which is provided so as to face the exit mirror and expands the laser beam reflected by the partial transmission part of the exit mirror and reflects the expanded laser beam to the partial transmission part of the exit mirror and its periphery. is there.

[0007]

In the laser device of the present invention, a part of the laser beam is transmitted by the exit mirror so that the beam shape is extracted from the conventional ring-shaped laser beam. Further, by making the exit mirror a mirror whose outer surface has a radius of curvature smaller than that of the inner surface, the divergent laser beam inside the resonator is converted into a parallel state by the refraction effect on the outer surface of the exit mirror. Taken out.

[0008]

1 is a sectional view of an embodiment of the present invention.
In the figure, 1a is a magnifying total reflection mirror consisting of a convex mirror,
3 is a laser medium, 4a is an exit mirror composed of a concave mirror, 5
Is a non-reflective coating film provided on the inner surface and the outer surface of the exit mirror 4a, and 20 is a partial reflection film provided on the central portion of the inner surface of the exit mirror 4a. 6 is a box, and 7 and 7a and 8 are laser beams.

Next, the operation will be described. The laser beam 7a expanded by the magnifying total reflection mirror 1a is amplified by the laser medium 3, and a part of the central portion thereof is exit mirror 4
The partial reflection film 20 of "a" and the entire peripheral portion thereof are taken out to the outside through the non-reflection coating film 5 of the exit mirror 4a, and both are combined to form a high quality laser beam 8 with a hollow inside. On the other hand, the laser beam 7 partially reflected by the partial reflection film 20 is again amplified by the laser medium 3 and further reflected and expanded by the expanding total reflection mirror 1a.

In this way, the laser beam 7 is emitted to the outside as a high quality laser beam 8 with a hollow inside each time the laser beam is reciprocated between the laser resonator composed of the expanded total reflection mirror 1a and the exit mirror 4a. Further, in this embodiment, since the radius of curvature of the outer surface of the exit mirror 4a is smaller than the radius of curvature of the inner surface, the laser beam 8 that has passed through the exit mirror 4a.
Is a collimated light that is generally easy to use due to the refraction effect on the outer surface of the exit mirror 4a. The inner surface of the exit mirror 4a is the surface on the inner side of the resonator as can be seen from FIG.
Further, the outer surface means a surface outside the resonator.

Further, in addition to the partial reflection film 20 provided on the exit mirror 4a to give the partial reflection property, the uncoated part 21 may be provided as shown in FIG. 2 to realize the partial reflection property. Further, in the above embodiment, the phase difference between the laser beam 7 passing through the partial reflection film 20 on the inner surface of the exit mirror 4a and the laser beam 7a passing through the non-reflection coating film 5 is generally small, so it is not a problem. The effect can be further enhanced by providing a means for canceling this.

As a means for this, as shown in FIG. 1, the partial reflection film 20 is made thick so as to cancel the phase difference between the laser beams 7a, 7 passing through the non-reflection coating film 5 and the partial reflection film 20. 8 to have the same phase, or a step 22 is provided on the outer surface of the exit mirror 4a as shown in FIG. 3 so that the optical path difference in the exit mirror 4a with respect to the two laser beams 7 and 7a is varied. You may cancel the phase difference. Further, as shown in FIG. 4, a phase compensation mirror 9 having a step 22 having the same function as the outer surface of the exit mirror 4a may be separately arranged. Although only the convex mirror is shown for the magnifying total reflection mirror, a concave mirror 1b may be used as shown in FIG.

In each of the above embodiments, the exit mirror and the wind mirror are integrated with each other. However, as in the conventional case, the exit mirror is a concave or convex mirror having a partial transmittance on the wind mirror surface. It may be provided.

[0014]

According to the present invention, since there is an exit mirror having a partially transmissive portion in the center and a non-reflective portion in the periphery and having an exit mirror whose radius of curvature of the outer surface is smaller than that of the inner surface, a laser is used as the exit mirror. A part of the beam can be transmitted and the laser beam diverging inside the resonator can be converted into a parallel state by the refraction action on the outer surface of the exit mirror and taken out to the outside. Therefore, the size of the magnifying mirror forming the resonator together with the exit mirror can be reduced, so that the laser beam in the middle can be extracted from the exit mirror while contributing to the cost reduction of the entire laser apparatus.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a schematic view of an embodiment of the present invention.

FIG. 3 is a schematic view of an embodiment of the present invention.

FIG. 4 is a schematic view of an embodiment of the present invention.

FIG. 5 is a schematic view of an embodiment of the present invention.

FIG. 6 is a schematic view showing an example of a conventional laser device.

[Explanation of symbols]

 1a, 1b Enlarged total reflection mirror 3 Laser medium 4a Exit mirror 5 Non-reflection coating film 7, 7a, 8 Laser beam 9 Phase compensation mirror 20 Partial reflection film

Claims (2)

[Claims] 1. A central has a nonreflective portion of the partial transmission part also in the peripheral portion, and the small radius of curvature of the outer surface than the radius of curvature of the inner surface
The exit mirror and the laser beam, which is arranged to face the exit mirror and is reflected by the partially transmissive portion of the exit mirror, is expanded and reflected to the partially transmissive portion of the exit mirror and its peripheral portion .
A laser device comprising a resonator having a magnifying mirror. 2. The laser device according to claim 1, wherein the magnifying mirror is a concave or convex mirror.