JP2673301B2 - Solid-state laser device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid-state laser device capable of obtaining a high-quality laser beam with a large cross-sectional area and a large output.

[Conventional technology]

FIG. 10 is a sectional view showing an example of a conventional solid-state laser device disclosed in, for example, the Laser Handbook (Ohm Co., published in 1982). In the figure, (1) is a solid-state element, for example, Y _3-x , N _dx , Al ₅ O _{12 in the} case of a YAG laser.
It consists of a rod with the composition (2) is a total reflection mirror, and (3) is an exit mirror, which constitute a so-called stable resonator. (4) and (5) are non-reflective films made of SiO ₂ provided on the outer surface of the exit mirror (3) and both end surfaces of the solid state element (L), (6) is an aperture, and (7) is an exit mirror ( TiO _{2 on} the inner surface of 3)
Partial reflection films (8) and (9) are laser beams generated inside and outside the resonator, respectively. (10) is a light source for exciting the solid-state element (1) such as a flash lamp, (11) is a support portion of the light source (10), and (12) is a light source (10).
Plate that reflects the light of the above and guides it to the solid state element (2), (13)
Is the outer frame of the solid-state laser device.

Next, the operation will be described. The solid-state element (1) is excited by the direct light from the light source (10) and the reflected light from the reflector (12) to form a laser medium. Then, the laser beam (8) is resonated and amplified in the laser medium, and a part of the laser beam (8) is taken out to the outside of the solid-state laser device as a laser beam (9). By the way, the laser beam (8) that reciprocates between the exit mirror (3) and the total reflection mirror (2) includes those having various phase distributions in the cross-sectional direction of the laser beam (8). Of these, the most suitable one for laser processing is a so-called TEM ₀₀ mode laser beam whose phase is aligned in the cross-sectional direction. This laser beam has a small divergence angle and is therefore narrowed down by a lens or the like to have a high power density, which enables efficient processing. Since this TEM ₀₀ beam has the smallest cross-sectional area among various laser beams, an aperture (6) having a small aperture can be inserted in the passage of the laser beam (8) to select only this laser beam. is necessary. In the case of a YAG laser, the wavelength is 1.06 μm, so the curvature of the total reflection mirror (2) and the exit mirror (3) that make up the resonator is 20 m, and the optical length between both mirrors (2) and (3) If the length is 1 m, the diameter of the TEM ₀₀ beam inside the resonator is about 1.8 mm. Conventionally, laser processing has been performed with a laser beam having such a small diameter.

[Problems to be solved by the invention]

According to the conventional solid-state laser device configured as described above, a high-quality laser beam can be obtained only with a small diameter of several mm, and the diameter of the solid-state element including the YAG rod is 1
Although it is possible to manufacture up to about 0 to 15 mm, the laser output cannot be sufficiently extracted from this solid-state element in the conventional device. Also, since the extracted laser beam has a small diameter,
Increasing the output increases the strength within the solid-state element, distorts the solid-state element itself, thereby degrading the beam quality, and in extreme cases, a so-called multi-mode having a disordered phase may occur. Therefore, the maximum power of the beam TEM ₀₀ beam of the solid-state laser device currently on the market is 10 W to 20 W.
W is the upper limit.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a solid-state laser device capable of obtaining a high-quality laser beam with a large cross-sectional area and thus a large output.

[Means for solving the problem]

A solid-state laser device according to the present invention comprises a solid-state element, a light source for irradiating the solid-state element with light, a resonator for resonating a laser beam, and the like, and resonates the laser beam in a laser medium formed in the resonator, In a fixed laser device configured to take out a part thereof to the outside, in the resonator, a magnifying mirror having a partial reflection portion provided in the center of the inner surface of an exit mirror, and a total reflection collimator arranged to face the magnifying mirror. It uses an unstable resonator composed of a mirror.

[Action]

The solid-state element is optically excited and resonated by an unstable resonator consisting of a magnifying mirror having a partial reflection part provided in the center of the inner surface of the exit mirror and a total reflection collimating mirror to generate a laser beam with a large cross-sectional area in the form of a jam. Take it out.

(Example of the invention)

FIG. 1 is a sectional view showing an embodiment of the present invention. In addition,
The same or corresponding parts as those of the conventional device shown in FIG. 10 are designated by the same reference numerals, and the description thereof will be omitted. In the figure, (2a) is a total reflection collimating mirror made of a total reflection film deposited on one end face of the solid state element (1). (3a) is a convex exit mirror, (4) is a non-reflective film made of, for example, SiO ₂ provided on the inner and outer surfaces of the exit mirror (3a), and (5) is the other end surface of the solid-state element (1). Is a non-reflective film made of, for example, SiO ₂ . Reference numeral (30) is an expansion mirror provided at the center of the inner surface of the exit mirror (3a) and made of a partial reflection film such as SiO ₂ and constitutes an unstable resonator together with the total reflection collimating mirror (2a). (8a) and (9a) are laser beams generated inside and outside the resonator, and (10) is a light source for exciting the solid state element (1) such as a flash lamp or a semiconductor laser.

The operation of the present invention configured as described above will be described below. First, the solid-state element (1) is excited by the direct light from the light source (10) and the reflected light from the reflector (12) to form a laser medium. On the other hand, the laser beam (8a) expanded and reflected by the magnifying mirror (30) is amplified in this laser medium, and the total reflection collimating mirror (2a) causes the non-reflection film (4) on the inner surface of the exit mirror (3a) and A collimated parallel laser beam (9a) is taken out of the solid-state laser device through a magnifying mirror (30) made of a partially reflective film. At this time, since the laser beam is expanded in each reciprocation in the resonator composed of the expanding mirror (30) and the total reflection collimating mirror (2a), the TEM shown in the conventional example in which the phases generated inside the resonator are uniform A laser beam corresponding to the ₀₀ beam will be obtained with an extremely large cross section.

2 (a) and 2 (b) are diagrams showing the shape of an example of the laser beam obtained by the present invention, respectively, when the magnifying power is 3 and the transmittance of the magnifying mirror (30) is 50%. A beam shape on the inner surface of the exit mirror (3a) (Fig. (A)) and a beam shape on the exit (Fig. (B)) are shown.

Further, FIG. 3 is a diagram showing an example of a focused beam pattern when a laser beam under the conditions shown in FIG. 2 is focused by a lens having a focal length f = 2.5 m. As shown in the figure, it can be seen that the condensing pattern is Gaussian.
By the way, in FIG. 3, the total divergence angle defined at the point where the central intensity becomes 1 / e ² was calculated to be about 0.2 mrad. This total divergence value is the same as the beam diameter of the present invention that is commercially available.
Comparing with the total divergence angle of a 10 mm YAG laser, it can be seen that in the present invention, a high-quality laser beam with an extremely good converging property, which is about 1/50 of the conventional emission beam diameter, can be obtained. Further, the beam diameter of the present invention is about 5 times the conventional beam diameter, and therefore the cross-sectional area is about 25 times, so that the solid state element (1) will not be deformed even with a large output, and the beam diameter of the conventional 10 A doubled output of about 100 W was easily obtained.

In the above description, the phase difference between the respective laser beams passing through the non-reflection film (4) provided on the inner surface of the exit mirror (3a) and the magnifying mirror (30) made of a partially reflective film is small, Although not a problem, a large phase difference may occur depending on the structure of the film, and the light condensing characteristics may deteriorate. At this time, for example, as shown in FIG.
In order to give an optical path difference between the two laser beams, a gap (31) may be provided on the outer surface of the exit mirror (3a) to cancel the generated phase difference, and the laser beam is expanded in the resonator. For this purpose, for example, a concave exit mirror (3b) may be provided as shown in FIG.

Further, the resonator mirror may be formed by directly providing the exit mirror (3c) (that is, the non-reflection film (4)) on the exit side end face of the solid-state element (1) as shown in FIG. As shown in FIG. 7, both mirrors (3c) and (2a) may be provided on both end faces of the solid-state device (1). When the resonator mirror is formed on the end face of the solid-state element (1) in this way, the device can be stabilized and the cost can be reduced. Of course, as usual, both resonator mirrors may be provided outside the solid-state element (1) as shown in FIG.

In addition, as shown in FIG. 9, Q such as Pockels element is used.
If the switch element (50) is also provided in the resonator to perform Q-switch pulse oscillation, a laser beam with a larger peak output can be obtained and efficient processing can be performed. If the element (50) shown in FIG. 9 is a wavelength conversion element such as a KTP element,
Efficient wavelength conversion can be realized by using the coherent beams. The element (50) may be a combination of a Q switch element and a wavelength conversion element.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the resonator has a magnifying mirror having a partial reflection portion provided at the center of the inner surface of the exit mirror, and a total reflection collimating mirror arranged to face the magnifying mirror. Since the unstable resonator configured by is used, it becomes a razor beam with a jam,
It is possible to obtain a laser beam with a large cross-sectional area, a large output, and high quality.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 (a),
(B) and FIG. 3 are diagrams showing the operation of FIG. 1, respectively.
FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9 and FIG. 9 are sectional views showing another embodiment of the present invention, and FIG. FIG. (1) …… Solid state element, (2), (2a) …… Total reflection collimating mirror, (3a), (3b), (3c) …… Exit mirror,
(4), (5) ... non-reflective film, (8a), (9a) ... laser beam, (10) ... light source, (12) ... reflector, (30)
…… Magnifying mirror, (31) …… Step. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A solid-state device, an optical device for irradiating the solid-state device with light, a resonator for resonating a laser beam, and the like. The laser beam resonates in a laser medium formed in the resonator, and a part thereof In the fixed laser device configured to take out to the outside, in the resonator, a magnifying mirror having a partial reflection portion provided at the center of the inner surface of the exit mirror, and a total reflection collimating mirror arranged to face the magnifying mirror. A solid-state laser device characterized by the use of an unstable resonator configured as described above.