JP2001007427A - Sold-state laser light propagation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solid-state laser light propagation device by which a beam diameter and diverging angle that is all the same as those at the outputting point can be precisely transferred to the incident point even if the thermal lens effect varies with oscillation output of the laser light. SOLUTION: In the solid-state laser light propagation device in which the laser light is propagated from an output point toward an incident point, there are provided a first concave lens 7 and a second concave lens 8, respectively, having the same focal length (f) and placed between the output point and the incident point, which are composed in such a way that the first concave lens 7 is placed in a position separated from the output point by a distance equal to the focal length (f), the second concave lens 8 is placed in a position separated from the first concave lens 7 by a distance twice as long as the focal length (f) and the incident point is separated by a distance equal to the focal length (f) from the second concave lens 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state laser light propagation device.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a general laser oscillation device. Solid laser media 4 and 4 (which form a laser resonator between a transmission mirror 2 and a reflection mirror 3 forming an optical resonator 1) are shown. For example, Nd: YAG laser rod) are arranged in series,
The solid-state laser media 4 and 4 are excited by an excitation source (not shown) such as a krypton lamp to emit light, and the light is reciprocated between the transmission mirror 2 and the reflection mirror 3 to be transmitted to the solid-state laser media 4 and 4. By repeating input and output, optical resonance is caused to amplify light energy, and laser light can be oscillated through the transmission mirror 2.

Further, the solid-state laser mediums 5, 5 forming a laser amplifying section are compared with the solid-state laser mediums 4, 4 forming a laser resonator.
Are arranged in series on the same optical axis, and the laser light oscillated from the laser resonator side via the transmission mirror 2 is further amplified by passing through the respective solid-state laser media 5 and 5 which are excited by an excitation source (not shown). Thus, a high output laser beam can be obtained.

Then, the laser beam oscillating while expanding the diameter at a required beam divergence angle toward the laser amplifying section with the laser beam condensing position of the laser output of the laser resonating section (the surface on the opposite side of the transmission mirror 2) as the emission point. In order to transfer the same beam diameter as the emission point to the incidence point set on the entrance side of the laser amplifying section and to make the same incident, the convex lens 6 having the focal length f forming the laser beam propagation device is connected to the geometrical optics. It is arranged at an intermediate position at a distance of twice the focal length f from both the exit point and the entrance point based on the image formula.

[0005]

However, in the solid-state laser, the solid-state laser mediums 4, 4 and 5, 5 are heated by the excitation light from the excitation source and cooled by the cooling water.
Of the solid-state laser medium 4, 4, 5, 5 have the same effect as the convex lens, and this thermal lens effect changes according to the oscillation output of the laser light. Therefore, in the propagation optical system that simply transfers the beam diameter from the emission point to the incidence point as described above, the beam diameter is transferred when the thermal lens effect changes and the transverse mode of the laser beam changes. However, there is a problem that the beam divergence angle cannot be transferred.

That is, as shown in FIG. 2, when the thermal lens effect appears strongly, a laser beam having a small beam diameter and a large beam divergence angle at the emission point is oscillated, and is based on the imaging formula of geometrical optics. Even if one-to-one image transfer is performed, as shown in FIG. 3, when the oscillation output of the laser beam is low and the thermal lens effect is weak, a laser having a large beam diameter at the emission point and a small beam divergence angle is used. As a result of the light being oscillated, the condensing position after the lens is in front (convex lens 6 side)
, So even if the beam diameter is kept the same,
The beam divergence angles will be significantly different.

On the laser resonator side, since light passes through all the cross sections of the solid-state laser media 4 and 4, only the beam diameter is transferred from the emission point to the incidence point, and the beam divergence angle is not transferred. In such a case, the laser light incident on the side of the laser amplifying section having the same thermal lens effect always impinges on the side surfaces of the solid-state laser media 5 and 5, causing a decrease in beam quality. It has to be made smaller and the outside of the beam must be cut, causing waste.

The present invention has been made in view of the above-described circumstances, and even if the thermal lens effect changes according to the oscillation output of laser light, the same beam diameter and beam divergence angle as the exit point are set with respect to the incident point. It is an object of the present invention to provide a solid-state laser light propagation device capable of accurately transferring.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a solid-state laser light propagation device for propagating laser light from an emission point to an incidence point. Consisting of an equal first convex lens and a second convex lens, the first convex lens is arranged at a position away from the emission point by a focal length, and at a position away from the first convex lens by a double focal length. A second convex lens is arranged, and an incident point is arranged at a position away from the second convex lens by a focal length.

Therefore, in the present invention, by making the distance from the emission point to the first convex lens equal to the focal length, the beam divergence angle is infinite at a position equidistant from the rear focal length of the first convex lens. Further, since the same lens system composed of the second convex lens is constructed behind the first convex lens so as to be symmetrical with respect to this position as a base point, it is completely symmetrical from the exit point to the entrance point. A beam trajectory is formed, and the same beam diameter and beam divergence angle as the exit point are transferred at the entrance point whose distance from the exit point is four times the focal length.

[0011]

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

FIG. 1 shows an example of an embodiment of the present invention, and portions denoted by the same reference numerals as those in FIG. 2 represent the same components.

In this embodiment, the first and second convex lenses 7 and 8 having the same focal length f are replaced by the exit point instead of the above-described propagation optical system comprising one convex lens 6 in FIG. It is arranged as follows between the incident point.

That is, the first convex lens 7 is arranged at a position away from the emission point by the focal length f, and the second convex lens 8 is placed at a position twice the focal length f from the first convex lens 7. Are disposed, and the focal length f is set from the second convex lens 8.
The mutual positional relationship is set so that the incident points are arranged at positions separated by a distance.

Thus, by making the distance from the emission point to the first convex lens 7 equal to the focal length f, the rear focal length f of the first convex lens 7 can be reduced.
The same lens system consisting of the second convex lens 8 is constructed behind the first convex lens 7 so that the beam divergence angle becomes infinite at a position equidistant from the first convex lens 7 and symmetrical with respect to this position. Therefore, a completely symmetric beam trajectory is formed between the exit point and the entrance point, and the beam diameter at the entrance point where the distance from the exit point is four times the focal length f is exactly the same as the exit point. And the beam divergence angle is transferred.

That is, in the case of a Gaussian beam such as a laser beam (a light beam whose amplitude distribution of a wave in a cross section perpendicular to the propagation direction is represented by a Gaussian function), when the beam passes through a convex lens, the beam has a focal length after the lens. There is a property that the radius of curvature of the wavefront is uniquely determined, and this radius of curvature changes depending on the position of the focal position before the lens, and the distance between the focal position before the lens and the convex lens is particularly the focal length. Since it is known that infinity (parallel light) is obtained when the focal length f is equal to the distance from the emission point to the first convex lens 7 as shown in FIG. The beam divergence angle becomes infinite at a position equidistant from the rear focal length f of the convex lens 7 of FIG.

Therefore, according to the above embodiment, even if the thermal lens effect changes in accordance with the oscillation output of the laser beam, the exact same beam diameter and beam divergence angle at the emission point can be accurately transferred to the incidence point. Therefore, the laser beam incident on the laser amplifying unit side, which has the same thermal lens effect as the laser resonator unit side, is transmitted through the solid-state laser media 5, 5 without any trouble, and the oscillation output of the laser beam Irrespective of the above, the beam quality can be maintained well and stably.

It should be noted that the solid-state laser light propagation device of the present invention is not limited to the above-described embodiment, and may be used for other than the propagation of laser light from the laser resonator to the laser amplifier. In addition, it goes without saying that various changes can be made without departing from the spirit of the present invention.

[0019]

According to the solid-state laser light propagation apparatus of the present invention described above, even if the thermal lens effect changes in accordance with the oscillation output of the laser light, the same beam diameter and beam divergence angle as the emission point are obtained. An excellent effect that accurate transfer can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment for implementing the present invention.

FIG. 2 is a schematic diagram showing a conventional example.

3 is a schematic diagram showing a case where the thermal lens effect of each solid-state laser medium of FIG. 2 is weak.

[Explanation of symbols]

 7 First convex lens 8 Second convex lens f Focal length

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Yoshihisa Yamauchi 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima-Harima Heavy Industries Co., Ltd. Toji Technical Center (72) Inventor Akihiro Nishimi Toyosu, Koto-ku, Tokyo No. 1-115, Ishikawajima-Harima Heavy Industries, Ltd., Toji Technical Center (72) Inventor Yutaka Kanazawa 3-1-1, Toyosu, Koto-ku, Tokyo Ishikawajima-Harima Heavy Industries, Ltd. ) 5F072 AB02 AK01 JJ05 KK01 KK30 MM20 PP01 YY17

Claims (1)

[Claims] 1. A solid-state laser light propagation device for propagating laser light from an emission point to an incidence point, comprising: a first convex lens disposed between the emission point and the incidence point and having the same focal length and a second convex lens. The first convex lens is disposed at a position away from the emission point by the focal length, and the second convex lens is disposed at a position away from the first convex lens by a double focal length, A solid-state laser light propagation device, wherein an incident point is arranged at a position apart from the second convex lens by a focal length.