JPH01270375A - Solid-state laser device - Google Patents

Abstract

PURPOSE:To improve an oscillation efficiency, facilitate the transmission of laser rays, and obtain a laser beam excellent in convergence by a method wherein a resonator is constituted in such a manner that it serves as a stable type resonator at a P plane and as an unstable type resonator at an S plane perpendicular to the P plane and concurrently an outlet mirror is composed of a central part formed of a partial reflection section and both ends formed of a non-reflective section at the P plane. CONSTITUTION:An outlet mirror 3, which is provided with a partial reflection film 30 formed on its central part and a non-reflective film 31 formed on its peripheral part, and a total reflection mirror 2 constitute a stable type resonator at a P plane 8 and an unstable type resonator at an S plane 9. And, a laser beam 101 taken out from the central part of the outlet mirror 3 and a laser beam 102 which penetrates through the non-reflective film 31 formed on the peripheral part of the mirror 3 are compounded to be a solid laser beam 10 which is taken outside. And, when the laser beams 101 and 102 are largely different from each other in a phase difference, a means which makes them equal to each other in phase is provided, for instance, a step 32 is provided to an outlet face of the outlet mirror 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the quality of a laser beam of a solid-state laser device.

[Conventional technology]

1 and 1 are, for example, Japanese Patent Publication No. 54-8179
It was shown in Publication No. 4. FIG. 1 is a perspective view and a cross-sectional configuration diagram showing a conventional slab-type solid-state laser device. In the figure, (1
) is a slab-like laser medium having an end face inclined with respect to the optical axis (6) and a substantially rectangular cross section perpendicular to the optical axis, and has optically smooth surfaces 01), (13, and end face (13, Q41). In Fig. 1, (2) is a concave total reflection mirror, ω is a flat partial reflection mirror (2), and ■ constitutes a laser resonator (4).

15) is a light source for exciting the laser medium.

Next, the operation will be explained. The laser medium (1) has a surface (ill, (1)
3, concave reflector (2), plane reflector fi
A laser beam is generated by a laser resonator consisting of 8 cm. The laser beam is reflected by a concave reflector (2) and a plane reflection@! It goes back and forth between (2) and a portion is taken out as output. Outside the laser medium (1), the optical path of the laser beam is along the optical axis (6) determined by the reflecting mirror (2) and ■ that constitute the laser resonator.
) matches. Within the laser medium +1), the laser medium t
The laser beam is refracted by entering and exiting the longitudinal end faces αj and (141 of ll), and the angle is such that total internal reflection takes place with respect to the first faces αD and α2, so the laser beam travels along the optical path (7). The plane (8) that forms the plane of reflection when the laser beam passes through the laser medium (1) is known as the P plane. The plane (9) perpendicular to 8) is known as the S-plane. - the width measured in the S-plane (9) of the slab-shaped laser medium (1);
The ratio to the thickness measured in the P plane (8) is typically 1.5 to
It is 2 or more. Therefore, it is stable within the plane (8),
By configuring a resonator that is unstable within the plane (9), the low-order transverse mode or the lowest-order transverse mode with good convergence, which has a cross section that matches the rectangular cross section of the laser medium (1), can be efficiently generated. can get. In Figure 1, the planar partial reflector (
) and the concave total reflection mirror (2) constitute a resonator that is stable in the P plane (8) and unstable in the S plane (9).

[Problem that the invention seeks to solve]

As described above, in conventional solid-state laser devices, an unstable resonator in the S plane is constructed by a flat partial reflecting mirror and a concave total reflecting mirror, so it is not a confocal unstable resonator, but a concave reflecting mirror. The reflected laser beam from the mirror becomes a focused beam instead of a parallel beam. For this reason, the excited laser medium cannot be completely filled with the laser beam, resulting in zero
Oscillation efficiency decreases. Furthermore, since it is not a parallel beam, it has problems such as being unsuitable for long-distance transmission. Furthermore, depending on the transmittance value of the planar partial reflector, there is a large phase difference between the transmitted laser beam from the planar partial reflector in the S plane and the laser beam from the surrounding area, that is, the part that does not pass through the planar partial reflector. However, there was a problem in that the spot when the lens focused the light was too small to narrow down.

The present invention has been made to solve the above-mentioned problems, and the single oscillation efficiency is improved.

The object of the present invention is to obtain a solid-state laser device that can easily transmit a laser beam and can obtain a laser beam with good convergence.

[Means to solve the problem]

The solid-state laser device according to the present invention constitutes a stable valve resonator in the P plane, and constitutes an unstable resonator in which the laser beam within the cavity is parallel in the S plane perpendicular to the P plane. Then, together (.

The exit mirror constituting the laser resonator is composed of a partially reflecting part at the center and non-reflecting parts at both ends in the S plane.Furthermore, there is a part between the partially reflecting part and the non-reflecting part between the laser beams passing through the non-reflecting part. Means for canceling the phase difference may also be provided.

[Effect]

The laser resonator according to the present invention efficiently generates a low-order transverse mode parallel beam that completely fills the laser medium, and can further reduce the phase difference, thereby improving the power concentration of the focused spot by a lens or the like.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a solid-state laser device of the present invention.

This corresponds to FIG. 6 showing the prior art, and the same reference numerals indicate the same or equivalent parts. (21 is a total reflection mirror, (3) is an exit mirror with a partially reflective film 1 in the center and a non-reflective film around the periphery.
Together with the total reflection mirror (2), the P plane (81) constitutes a stable valve resonator, and the S plane (9) constitutes an unstable resonator. Figure 2 shows the cross-sectional configuration of the solid-state laser device in the S plane (9). FIG. Anti-reflective coating applied to the outer edge and outer surface.

(1G is the laser beam taken out to the outside). Further, (101) is a laser beam taken out from the center of the exit mirror (3), and (102) is a laser beam taken out from around it.

Next, the operation will be explained. The laser medium (1) is excited by the excitation light sources (4) and (5) shown in FIG.

Laser beam oscillates. In the S plane, the laser beam (1OS) expanded and reflected by the partially reflecting film (to) at the center of the exit mirror (3) in Figure 2 is reflected by the laser medium (1).
The light beam is refracted by the end face α-bump, and travels in a zigzag pattern while being totally reflected within the laser medium (1) along the optical axis (6). The above laser beam emitted from the other end face (3) of the laser medium (1) is converted into a parallel beam by the total reflection mirror (2) and reflected towards the laser medium (1). The laser beam returns to the exit mirror (3) through a zigzag path due to total reflection, but a part of the laser beam that has returned to the center is enlarged and reflected again by the partial reflection film 2, and the - part becomes the laser beam (101) directed outside the resonator. ).

The laser beam (101) is combined with the laser beam (102) that has passed through the non-reflection film OD at the periphery, and is extracted to the outside as a central laser beam OQ. FIG. 4 is an example of calculation of the intensity distribution when the laser beam ql) is focused by a lens. Since most of the laser beams are concentrated near the center, it can be seen that the laser concentration has improved. In the P plane, the exit mirror (3) and the total reflection mirror (2) constitute a stable resonator, so the laser beam can oscillate in the lowest order mode, and at this time, when focused by a lens, The intensity distribution has a so-called Gaussian shape, and the light concentration is good. Therefore, the beam convergence is good in both the P plane and the S plane, and the degree of power concentration is improved.

In addition, in the above embodiment, it is used as the exit mirror (3).

A cylindrical mirror that is flat in the P plane and convex in the S plane is used as a total reflection mirror (21 has a mirror configuration with equal radii of curvature in the P and S planes, but the exit mirror (3)
, the radius of curvature of the total reflection mirror (21) may be a combination set independently for the P plane and the S plane so that it is stable in the P plane and unstable in the S plane. Stability of the resonator.

Instability can be designed using the well-known so-called g parameter.

Furthermore, in the above embodiment, it was assumed that the laser beams (101) and (102) lj passing through the exit mirror (3) are combined with almost the same phase, but the laser beam passing through the partially reflecting film (to) (101) and the laser beam (102) passing through the non-reflection film C(I), if a large phase difference occurs between the laser beam (102) and the laser beam (102) passing through the non-reflection film C(I), it is possible to provide a means to create a difference in the optical path length of the two and make the phase equal to 0. Preferably, this can be realized, for example, by providing a step on the exit surface of the exit mirror (3) as shown in FIG.

Furthermore, in the above embodiments, it is used as a solid laser medium.

Although the laser beam takes a zigzag path while undergoing total internal reflection in the laser medium, the zigzag path of the laser beam in the laser medium is not necessary to achieve the purpose of the present invention. - Of course, if the lateral ratio is large, for example 3 or more, the laser beam may pass straight through the laser medium. In this case, the P plane is a plane determined by the optical axis and the vertical vector of the end face, and the S plane is a plane perpendicular to the P plane.

〔Effect of the invention〕

As described above, according to the present invention, a stable resonator is constructed in the P plane, and an unstable resonator is constructed in which the laser beam within the resonator is parallel to the S plane perpendicular to the P plane. At the same time, since the exit mirror constituting the laser beam oscillator is configured such that the center is a partially reflective part 1 and both ends are non-reflective parts in the S plane, the low-order mode corresponding to the cross-sectional area of the laser medium is This has the effect of not only being able to efficiently obtain a laser beam, but also being able to easily transmit and obtain a laser beam with good convergence.

Further, by providing a means for canceling the phase difference between the laser beam passing through the partially reflecting section and the non-reflecting section, it is possible to obtain a laser beam with even better convergence.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a solid-state laser device according to an embodiment of the present invention, FIG. 2 is a cross-sectional configuration diagram taken on the S plane of FIG.
The figure is a cross-sectional configuration diagram on the P plane of FIG. 1, FIG. 4 is a light intensity distribution aperture showing the condensing property of a laser beam emitted from a laser device according to an embodiment of the present invention, and FIG. FIG. 7 is a sectional view showing an exit mirror according to another embodiment. 6 and 1 are a perspective view and a cross-sectional configuration diagram, respectively, showing a conventional solid-state laser device. +11... Laser medium, [2]... Total reflection mirror, (3
)...Exit mirror, +61...Optical axis, (8)...
P plane, (9)...S plane, 13. αj... end face,
Gl...partially reflective film, DI)...non-reflective film, al
. (1o1), (1o2), (1os)...laser beam, (to)...stepped portion. Note that in the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A laser resonator configured by a laser medium having an end surface inclined with respect to the optical axis and having a substantially rectangular cross section perpendicular to the optical axis, and a plurality of mirrors provided across this laser medium. In the above, the laser resonator constitutes a stable resonator in the P plane determined by the optical axis and the vertical vector of the end face, and the laser resonator constitutes a stable resonator in the S plane perpendicular to the P plane. An unstable resonator in which the laser beam is parallel is configured, and the exit mirror constituting the laser resonator is characterized in that, in the S plane, the center is a partially reflective part and both ends are non-reflective parts. Solid state laser device. (2) The solid-state laser device according to claim 1, further comprising means for canceling a phase difference between the laser beams passing through the partially reflecting section and the non-reflecting section.