JPH057035A - Laser beam generating apparatus - Google Patents

Abstract

PURPOSE:To effectively generate high power laser beam without enlarging an apparatus, by installing laser medium which generates laser beam in a light emission pattern of a higher order transversal mode, and a plurality of pumping means giving pumping energy. CONSTITUTION:An equipment generating laser beam for pumping which equipment is constuted of, e.g. a laser diode is accommodated in an excitation light source 1. A fiber array 2 is constituted of a plurality of optical fibers 2a-2c. A concave mirror 4 is constituted so as to transmit the greater part of laser light for pumping and reflect the greater part of fundamental wave laser light generated by laser medium 5. A concave mirror 6 transmits laser beam generated by laser medium in the several percent to several ten's percent range and reflects the residual part. When a plurality of optical fibers are arranged so as to correspond with a plurality of light emission patterns, higher output laser light can be generated without increasing the size of a resonator 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light generator suitable for use in the case of generating high power laser light.

[0002]

2. Description of the Related Art There is known a stable resonator capable of irradiating a laser medium arranged between two resonant mirrors with a pumping laser beam to generate a laser beam having a higher output than the laser medium. .. In order to further increase the output of this stable resonator, the pumping sources may be arranged in parallel and a large amount of pumping laser light may be incident on the laser medium. Therefore, in the past, the basic transverse mode (TEM00)
In order to efficiently oscillate the laser, a pumping source for generating a laser beam for pumping was arranged along the oscillation axis direction so as to be within the size of the fundamental transverse mode.

For example, as shown in FIG. 8, in order to concentrate more pumping energy for one light emission pattern, it is necessary to concentrate and irradiate as much laser light as possible. Therefore, in this example, 7
The optical fibers of the book are arranged in a concentrated manner with respect to one light emitting pattern. Then, seven pumping laser lights are generated from the seven optical fibers to irradiate one light emission pattern.

[0004]

However, when the excitation sources are parallelized in this way, there is a problem that the size of the excitation source becomes large due to the parallelization and the fundamental transverse mode size is exceeded, thus deteriorating the efficiency. To prevent this, the basic transverse mode size should be increased. However, if the basic transverse mode size is increased, it becomes necessary to lengthen the resonator length in proportion to the square of the basic transverse mode size. come. As a result, there arises a problem that the device becomes large.

Further, since the excitation source is concentrated, there arises a problem that the efficiency is deteriorated due to the thermal lens effect, thermal aberration and the like.

The present invention has been made in view of such circumstances, and it is an object of the present invention to efficiently generate a laser beam of higher output without increasing the size of the device.

[0007]

A laser light generator of the present invention comprises a laser medium that emits laser light in a high-order transverse mode emission pattern, and a plurality of, for example, a plurality of laser mediums corresponding to the emission patterns. And a pumping means for applying pumping energy composed of laser light.

In the embodiment, this pumping means comprises an excitation light source 1, a fiber array 2 and a lens 3.

[0009]

In the laser light generator having the above structure, a plurality of pumping energies are applied to the laser medium so as to correspond to the emission pattern of the higher-order transverse mode. Therefore, it is not necessary to increase the size of the basic transverse mode, and it is possible to efficiently generate high-power laser light without increasing the size of the device.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the laser light generator of the present invention. The pumping light source 1 accommodates therein a device for generating pumping laser light, such as a laser diode. The fiber array 2 is composed of a plurality of optical fibers 2a to 2i (only three optical fibers 2a to 2c are shown in FIG. 1, but in the case of this embodiment, there are nine optical fibers 2a to 2c). The optical fibers 2a to 2i are arranged at a total of nine points, each vertex of the square, the midpoint of each side, and the central point of the square (see FIG. 2)).

The lens 3 makes the laser light for pumping incident from the fiber array 2 incident on the laser medium 5 via the concave mirror 4. In this embodiment, the pumping light source 1, the fiber array 2 and the lens 3 constitute pumping means, but the pumping laser light constitutes an array of laser diodes, which is arranged close to the concave mirror 4. Then, the laser light for pumping can be made to enter without passing through the lens. As the energy for pumping, it is possible to use energy other than laser light, such as electron beam, current injection, and discharge, which is an example source that causes population inversion and can be selectively excited.

The concave mirror 4 is arranged on the side of the laser medium 5 on which the pumping laser light is incident, and the concave mirror 6 is arranged on the opposite side. The concave mirror 4, the laser medium 5 and The concave mirror 6 constitutes a laser optical resonator 7.

The concave mirror 4 transmits most of the pumping laser light and reflects most of the fundamental laser light generated by the laser medium 5. Also,
The concave mirror 6 transmits a few percent to a dozen percent of the laser light generated by the laser medium 5 and reflects the rest.

In this embodiment, the laser medium 5 is
The TEM22 mode of Hermitian Gaussian distribution or Laguerre Gaussian distribution is oscillated. In the TEM22 mode, as shown in FIG. 2, the emission patterns 5a to 5i in the laser medium 5 are arranged at the center, the four corners, and the midpoints of the four sides of the square when viewed from the direction in which the laser light travels. .. Therefore, the optical fibers 2a to 2i are connected to the light emitting patterns 5a to 5i.
Are arranged at the center of the square, at the four corners, and at the midpoints of the four sides. As a result, the optical fibers 2a to 2
The pumping laser light emitted from i is incident on the corresponding light emitting patterns 5a to 5i. As described above, by pumping laser light from nine optical fibers corresponding to the nine light emitting patterns and exciting the laser light along the oscillation axis direction, the T
The EM22 mode can be oscillated.

In the laser medium 5, the light emission pattern 5a
9i to 5i, nine fundamental wave laser beams are generated. These fundamental-wave laser lights are high-power laser lights that repeat the reciprocating motion between the concave mirrors 6 and 4. And
Part of the laser light passes through the concave mirror 6 and is output to the outside.

In this embodiment, the light emitting pattern 5 is used.
The optical fibers 2a to 2i are arranged one by one corresponding to a to 5i, but the four-sided light emitting patterns 5a, 5c, 5g and 5i have higher energy than other light emitting patterns. There is. Therefore, stronger pumping laser light may be incident on these light emission patterns. This can be realized by, for example, making the diameters of the optical fibers 2a, 2c, 2g, 2i thicker than the other optical fibers 2b, 2d, 2e, 2f, 2h, or increasing the number.

By arranging a plurality of optical fibers corresponding to a plurality of light emission patterns in this way, the mode size can be increased without increasing the size of the resonator 7, so that a laser beam of higher output can be emitted. Can occur. Further, in the above-described embodiment, the oscillation is performed in the TEM22 mode, but it is possible to use any TEMmn mode such as TEM11 and TEM33.

By the way, it has been found that only the higher-order single transverse mode can be efficiently excited, but the higher-order mode has a phase inversion of 180 degrees between adjacent peaks (between emission patterns). For this reason, there is a drawback that the central intensity is low and a minute spot with a diffraction limit cannot be formed. Therefore, for example, as shown in FIG. 3, the spatial phase compensating plate 11 can be arranged close to the resonator 7. This spatial phase compensator 11
Of the light emitting patterns 5a to 5i, as shown in FIG. 4, every other light emitting pattern 5a, 5c, 5e, 5g,
A film 11a having a thickness d is formed at a position corresponding to 5i. This thickness d is set so as to satisfy the following equation. (N-1) d = λ / 2 + mλ

The film 11a can be formed by vapor deposition, etching, ion diffusion or the like.

Here, n represents the refractive index of the spatial phase compensator 11, λ represents the wavelength of the laser beam, and m represents an integer. That is, the phase of the laser light is delayed by ½ wavelength (180 degrees) by the film 11a. As a result, the phases of the laser light emitted from the spatial phase compensation plate 11 and corresponding to the light emission patterns 5a to 5i are all in phase. As a result, in FIG.
If is not inserted, a far-field image as shown in FIG. 5 (a) is obtained, but by inserting the spatial phase compensating plate 11, the far-field image is shown in FIG. 5 (b). Like That is, it is possible to obtain laser light having a high single-peak central intensity.

In the embodiment of FIG. 3, the near-field image immediately after the spatial phase compensating plate 11 is Fourier-transformed in the optical path to become a far-field image, and a single-peaked laser beam can be obtained. Therefore, as shown in FIG. 6, a single-peaked near-field image can be obtained by compensating the phase of the far-field image with the spatial phase compensating plate 11 and then performing an inverse Fourier transform with the convex lens 21.

The same thing can be realized by arranging the spatial phase compensating plate 11 in the far field and arranging a convex lens 21 immediately after that to focus the laser beam as shown in FIG. 6, for example. Can be done. That is, in this way, the near-field image of the laser light emitted from the convex lens 21 is shown in FIG.
It is a monomodal one as shown in (b).

Further, in the embodiment shown in FIG. 3, the far-field pattern is as shown in FIG. 5 (b).
As shown in (b), side peaks occur in this far-field image. Depending on the application of laser light, this side peak may be an obstacle. Therefore, in such a case, as shown in FIG.
Is arranged, and the convex lens 21 is arranged immediately after that, after removing the side peaks by the aperture 31,
It is possible to obtain only the laser light with high central intensity. As a result, a minute spot with a diffraction limit can be formed.

By arranging the spatial phase compensating plate 11 in this way, a monomodal laser beam can be obtained.
Alternatively, for example, a nonlinear optical crystal element (KTiOPO ₄ ) may be arranged in the latter stage of the resonator 7 to generate the second harmonic laser light, thereby obtaining a single-phase laser light.

[0025]

As described above, according to the laser light generator of the present invention, a plurality of pumping energies are applied to the laser medium so as to correspond to the light emission pattern, so that the device is not enlarged. It is possible to efficiently generate a high-power laser beam.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a laser light generator of the present invention.

FIG. 2 is a diagram for explaining an emission pattern and an arrangement of optical fibers in the laser medium 5 of the embodiment of FIG.

FIG. 3 is a diagram showing a configuration of a second embodiment of a laser light generator of the present invention.

FIG. 4 is a diagram showing a configuration of a spatial phase compensation plate 11 in the embodiment of FIG.

FIG. 5 is a diagram illustrating a far-field image in the embodiment of FIG.

FIG. 6 is a diagram showing the configuration of a third embodiment of the laser light generator of the present invention.

FIG. 7 is a diagram showing the configuration of a fourth embodiment of the laser light generator of the present invention.

FIG. 8 is a diagram for explaining an arrangement state of light emitting patterns and optical fibers in a conventional laser light generator.

[Explanation of symbols]

 1 Excitation Light Source 2 Optical Fiber Array 2a to 2i Optical Fiber 3 Lens 4 Concave Mirror 5 Laser Medium 6 Concave Mirror 7 Resonator 5a to 5i Emission Pattern 11 Spatial Phase Compensation Plate 11a Film

Claims (1)

Claim: What is claimed is: 1. A laser medium to which a plurality of pumping energies are applied to generate laser light in a light emission pattern of a higher-order transverse mode, and a plurality of laser mediums corresponding to the light emission pattern. And a pumping means for applying pumping energy of the laser light.