JPH098385A - Solid state laser oscillator - Google Patents

Abstract

PURPOSE: To obtain a highly efficient solid state laser oscillator in which a high output TEM00 mode can be established through a compact constitution. CONSTITUTION: A laser rod 1 disposed in a condenser 4 constituting a solid state laser oscillator has optical planes at the opposite ends thereof, separated to the left and right of a plane including the axis of rod with respective planes, at the opposite ends, being paired. Since the light passes through the laser rod in the opposite directions while intersecting each other, asymmetry of the TEM00 mode due to shift in pumping intensity distribution caused by the laser rod can be relaxed and thermally induced uneven refractive index or strain can be offset. Consequently, the beam quality is improved and the high output TEM00 mode can be established while realizing compaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser oscillator, and more particularly to a solid-state laser oscillator that obtains a high power TE ₀₀ mode.

[0002]

2. Description of the Related Art Conventionally, in this type of solid-state laser oscillator,
A concentrator in which an excitation lamp and a rod-shaped solid-state laser medium (hereinafter referred to as a laser rod) are arranged in a reflecting mirror having a mono-elliptical cross section is provided, and the light emitted from the excitation lamp is condensed on the laser rod. There is a resonator configured by disposing a reflecting mirror with a laser rod interposed therebetween. However, in the laser oscillator having this configuration, the side of the laser rod that faces the excitation lamp is strongly excited, and therefore there is a problem that the TEM ₀₀ mode is biased due to the bias of the pumping intensity distribution.

Therefore, conventionally, two or more laser rods are arranged in the resonator, and the TEM in the laser medium is used.
In order to expand the mode volume of the ₀₀ mode, there is one that is composed of a long resonator. For example, as shown in FIG. 3, in two reflecting mirrors 3a and 3b each having a cross section of a single ellipse, two collecting mirrors for focusing the light emitted from the excitation lamps 2a and 2b on the laser rods 1a and 1b, respectively. Optical device 4a, 4b
Is used. The condensers 4a and 4b are connected to the output mirror 5
And a total reflection mirror 6 are arranged in series between them to form a resonator. In this configuration, in the two condensers 4a and 4b,
By arranging the pump lamps 2a and 2b and the laser rods 1a and 1b so that the positional relations thereof are opposite to each other, the bias of the pump intensity distribution can be alleviated.

Alternatively, as shown in FIG. 4, the excitation lamp 2 is arranged at the center of a reflecting mirror 3 having a bi-elliptical cross section.
The laser rods 1a and 1b are arranged on both sides of the laser rods 1a and 1b, and a condenser 4 which collects the light emitted from the excitation lamp 2 on the laser rods 1a and 1b is used, and the condenser 4 is used as an output mirror 5 and a total reflection mirror 6. It is arranged in the middle of the folding mirrors 7a and 7b to form a resonator. In this configuration, the laser rods 1a and 1b directed in opposite directions can alleviate the bias of the excitation intensity distribution.

An improved structure of the structure shown in FIG. 3 is disclosed in, for example, Japanese Patent Laid-Open No. 122522/1990. A configuration using the condenser of FIG. 4 is disclosed in Japanese Patent Laid-Open No. 2-29518.
In this case, one laser rod is used as an oscillator, another laser rod is used as an amplifier, and two laser rods are incorporated in a resonator. 4 is slightly different from the configuration of FIG.

[0006]

In such a conventional solid-state laser oscillator, the excitation lamp 2 has the configuration shown in FIG.
It has the advantage of being able to alleviate the asymmetry of the TEM ₀₀ mode due to the bias of the excitation intensity distribution, which is a problem of the mono-elliptical type condenser in which the a and 2b sides are strongly excited. Since a long resonator is formed by 4b, there is a problem that the oscillator becomes large.

Further, in the configuration of FIG. 4, the two laser rods 1a and 1b are efficiently pumped to some extent by one pump lamp, and the single resonator 4 is used to make the long resonator compact. However, in the transverse mode of the laser beam, there is a part that passes only the strongly pumped part and only the weakly pumped part of the two laser rods 1a and 1b, so that the TEM ₀₀ mode with good beam quality is obtained. There is a problem of hindering the high output of.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly efficient solid-state laser oscillator capable of obtaining a high power TEM ₀₀ mode with a compact structure.

[0009]

According to the present invention, a laser rod provided in a condenser forming a solid-state laser oscillator is
It is characterized in that light is passed through in the inside in opposite directions.

In this case, the first and second optical paths directed in opposite directions in the laser rod are made to intersect each other in the laser rod. That is, the laser rod is configured such that both end surfaces thereof are optical planes separated into right and left of a plane including the rod center axis, and the respective planes of both ends are paired and face each other. Then, the total reflection mirror and the first folding mirror are arranged on the extension of the first optical path formed by the pair of optical planes of the laser rod, and the second optical path formed by the other pair of optical planes. The output mirror and the second folding mirror are arranged on the extension of the above, and the first and second optical paths are coupled by the first and second folding mirrors.

[0011]

Since the light passes through the laser rod in opposite directions, and preferably in the intersecting state, and the laser oscillation is excited by these lights, the asymmetry of the TEM ₀₀ mode due to the deviation of the excitation intensity distribution generated in the laser rod. The properties can be relaxed, the non-uniformity of the refractive index and strain thermally induced in the laser rod can be canceled, the beam quality can be improved, and the TEM ₀₀ mode can have a high output.

[0012]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the overall configuration of an embodiment of the present invention. The excitation lamp 2 and the laser rod 1 are arranged in parallel in a reflecting mirror 3 having a single elliptical cross section to form a condenser 4. Then, two folding mirrors 7a and 7b are arranged facing each other on one end side of the laser rod, and an output mirror 5 and a total reflection mirror 6 are arranged facing each other on the other end side. Also, these output mirrors 5
The total reflection mirror 6 is provided with apertures 8a and 8b.

FIG. 2 shows a laser rod which constitutes the light collector.
It is shown in a perspective view and a plan view of (a) and (b). Both end faces of the laser rod 1 on one end side and the other end side are divided into two planes including a central axis and perpendicular to the excitation direction, and each end face is configured so that a cross section along the excitation direction is a triangle. ing. That is, the end surface 11 and the end surface 13 on the one end side and the end surface 12 and the end surface 14 on the other end side intersect at a required angle, respectively, and here, the end surfaces 11 and 12, 13 and 14 respectively.
Are parallel to each other.

The optical path L connecting the end faces 11 and 12
The folding mirror 7a and the total reflection mirror 6 are arranged on the extension of 1, and the folding mirror 7b and the output mirror 5 are arranged on the extension of the optical path L2 connecting the front end faces 13 and 14. The folding mirrors 7a and 7b are configured to reflect light between the optical paths L1 and L2.

In this configuration, the light emitted from the excitation lamp 2 is condensed by the laser rod 1, and the total reflection mirror 6, the folding mirrors 7a and 7b, and the output mirror 5 resonate through the optical paths L1 and L2 of the laser rod 1. Make up a container. Also,
The apertures 8a and 8b are for selecting the TEM ₀₀ mode.

In order to obtain a high-power TEM ₀₀ mode, (1) excitation intensity distribution, (2) temperature gradient gradient index distribution, and (3) for transverse modes of laser light passing through the laser rod 1. ) It is necessary to have conditions that do not affect the strain distribution due to the temperature gradient as much as possible.

Regarding the influence of the above (1), the optical path L1,
The laser light passing through L2 alternately passes through the strongly pumped portion on the side of the pumping lamp 2 and the opposite weakly pumped portion, thereby having an effect of canceling the influence of the transverse mode on the pumping intensity distribution.

Further, regarding the laser light passing through the end face 11 and the end face 12, qualitatively observing the influences of the above (2) and (3), the temperature distribution has a gradient with the central axis of the laser rod as the center. On the other hand, the laser light has an effect of passing so as to cancel the influence of the height of the temperature distribution, particularly in the excitation direction. The same applies to the laser light passing through the end faces 13 and 14.

In this way, two optical paths can be obtained by one laser rod 1, so that energy extraction in the laser rod can be efficiently performed. Since it is desirable that the laser rod is uniformly excited, the excitation light is preferably focused on the laser rod by a diffusion type reflecting mirror such as a ceramic material.

In the above embodiment, the mono-elliptical condenser 4 is used.
Although an example in which the resonator is configured by is shown, even if a bi-elliptical concentrator having two excitation lamps is used, the above (1),
The effects against the influences of (2) and (3) are obtained.

[0021]

As described above, according to the present invention, since the light passes through in the laser rod in opposite directions, the excitation intensity distribution in the laser rod,
The effects of thermally induced non-uniformity of refractive index and strain can be offset. Thereby, the asymmetry of the TEM ₀₀ mode due to the bias of the excitation intensity distribution can be relaxed,
Moreover, it is possible to improve the beam quality and increase the output power of the TEM ₀₀ mode. Further, the laser oscillator can be configured with a single condenser, and its compactness can be realized.

In particular, the first and second optical paths in the laser rod, which are directed in opposite directions to each other, are constructed so as to intersect each other in the laser rod, so that the above-mentioned excitation intensity distribution, refractive index, and distortion can be suppressed. It is possible to effectively offset the influence of non-uniformity.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a perspective view and a plan view of a laser rod used in the present invention.

FIG. 3 is a schematic perspective view of an example of a conventional solid-state laser oscillator.

FIG. 4 is a schematic perspective view of another example of a conventional solid-state laser oscillator.

[Explanation of symbols]

 1 Laser Rod 2 Excitation Lamp 3 Reflector 4 Concentrator 5 Output Mirror 6 Total Reflector 7a, 7b Folding Mirror 8a, 8b Aperture

Claims (4)

[Claims] 1. A rod-shaped solid-state laser medium, an excitation lamp arranged along the solid-state laser medium, and a reflecting mirror for concentrating the light emission of the excitation lamp on one side surface of the solid-state laser medium. 2. A solid-state laser oscillator comprising a light-collecting device configured as described in 1. above, wherein the solid-state laser medium has a structure in which light passes in mutually opposite directions. 2. The solid-state laser oscillator according to claim 1, wherein the first and second optical paths directed in opposite directions in the solid-state laser medium are arranged in an intersecting state in the solid-state laser medium. 3. The solid-state laser medium is configured such that both end faces thereof are optical planes separated from each other on the left and right of a plane including the rod center axis, and the respective planes at both ends are opposed to each other in pairs. The solid-state laser oscillator according to claim 2. 4. A total reflection mirror and a first folding mirror are arranged on an extension of a first optical path constituted by a pair of optical planes of a solid-state laser medium, and are constituted by another pair of optical planes. 4. The solid according to claim 1, wherein an output mirror and a second folding mirror are arranged on an extension of the second optical path, and the first and second optical paths are coupled by the first and second folding mirrors. Laser oscillator.