JPH11284253A - Ld pumped solid laser oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LD(laser diode) pumped solid laser oscillation device wherein, of simple configuration, usage efficiency of excitation light is high. SOLUTION: Pumping light 4 radiated from an LD3 is incident on a laser medium 1 of slab type through a window part 20a and a cooling medium 11, for use with laser excitation. The pumping light 4 transmitting the laser medium 1 reaches a reflection surface 21a of a reflection layer 21 through the cooling medium 11 and a transparent base material of a cooling pipe 20. The reflection layer 21 comprises a metal vapor-deposition layer, etc., with high reflectivity for the pumping light 4. The most part of the pumping light 4 is reflected on the reflection surface 21a, reversing the transparent base material of the cooling pipe 20, and made incident on a laser medium 2 again through the cooling medium 11. A part of it is absorbed in the laser medium 2 for effective use with laser pumping. The laser medium may be rod-shape. The reflection layer 21 may be set on an inner side surface 20b of the cooling pipe 20.

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 oscillation device (LD-excited solid-state laser oscillation device) using a laser diode as an excitation source, and more specifically, to efficiently supply excitation light to a laser medium. The present invention relates to an LD-pumped solid-state laser oscillation device improved in relation to the reflection means.

[0002]

2. Description of the Related Art A solid-state laser oscillating device in which a solid-state laser medium such as YAG is disposed in an optical resonator and which is laser-excited by optical energy supplied from an excitation source is a high-power and stable laser oscillation. Is widely used in laser processing devices for cutting, welding, and the like of metals and other materials. Conventionally, lamps such as a halogen lamp and a xenon lamp have been widely used as an excitation source for a solid-state laser oscillation device, but recently, an LD (Laser Diode =
Laser diode. same as below. ) Is drawing attention. L
A laser oscillation device using D as an excitation source is generally called an “LD excitation solid-state laser oscillation device”.

FIG. 4 is a cross-sectional view showing an essential structure of an example of a conventionally proposed side-pumped LD-pumped solid-state laser oscillation apparatus.

In FIG. 1, reference numeral 2 denotes a laser medium made of, for example, a rod-shaped YAG laser crystal, which is surrounded by a cooling medium 11 such as pure water flowing through a transparent cooling pipe 40, and is provided with an output mirror and a rear mirror. It is arranged between mirrors (both not shown). The cooling medium 11 suppresses a temperature rise that occurs during operation of the laser. Note that a slab-shaped laser medium is often used instead of the rod-shaped laser medium 2.

[0005] The LD 3 used as an excitation source is arranged outside the cooling pipe 40 and supplies the excitation light 4 from the side of the laser medium 2 through a converging lens 12 arranged as necessary.

A reflector 6 is provided around the cooling pipe 40 so as not to hinder the supply of the excitation light 4 by the LD 3.
The surface 6a of the reflector 6 facing the cooling tube 40 is a surface having a high reflectance with respect to the emission wavelength of the LD, and forms a gap 5 formed of an air layer between the cooling tube 40 and the outer peripheral surface.
Reference numerals 6b to 6e denote cooling medium flow paths provided at appropriate locations inside the reflector 6, and are necessary particularly when a high-output laser is formed.

In the above configuration, the excitation light 4 radiated from the LD 3 is incident on the laser medium 2 through the condensing lens 12, the cooling tube (government wall member) 40, and the cooling medium 11 flowing inside the lens. A substantial part of the excitation light incident on the laser medium 2 is absorbed by the laser medium 2 and used for laser excitation (optical pumping) of the laser medium 2, but a part is transmitted to the back side without being absorbed by the laser medium 2. , The cooling medium 11, the cooling pipe (government wall member) 40, and the air layer 5, and enters the reflecting surface 6 a inside the reflecting body 6.

Most of the light incident on the inner surface 6a having a high reflectance is reflected, and the air layer 5, the cooling pipe (government wall member) 4
0, the laser medium 2 returns to the laser medium 2 via the cooling medium 11, and a part thereof is absorbed by the laser medium 2 and used for laser excitation. As described above, in the LD-pumped solid-state laser oscillation device having the conventional configuration, the cooling medium 11 for cooling the laser medium 2 is used.
A reflector 6 separate from the cooling tube 40 is disposed outside the cooling tube 40 through which the laser beam flows, so that the utilization efficiency of the excitation light 4 (the ratio of the amount of light absorbed by the laser medium 2 to the total amount of light) is increased. .

[0009]

However, the above-described conventional LD-pumped solid-state laser oscillation device has the following problems. 1. The reflector 6 is provided outside the cooling pipe 40 separately from the cooling pipe 40.
This hinders downsizing of the entire device. Further, since the temperature of the reflector 6 also rises considerably, it is necessary to provide a room for heat radiation. In particular, in the case of a high-power laser, cooling medium channels 6b to 6e are required. Such cooling medium flow paths 6b to 6e are
It can easily cause corrosion.

[0010] 2. Since the cooling pipe 40 and the reflector 6 are arranged separately, a gap 5 composed of an air layer is interposed between the two. Therefore, a part of the excitation light 4 reflected on the reflection surface 6a of the reflector 6 causes multiple reflections in the gap 5 and causes light loss.

It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide an LD-pumped solid-state laser oscillation device capable of efficiently absorbing pumping light into a laser medium with a simple configuration.

[0012]

According to the present invention, a solid-state laser medium is arranged in an optical resonator, a cooling pipe for flowing a cooling medium for cooling the solid-state laser medium is provided, and the solid-state laser medium is laser-excited. In a solid-state laser oscillation device in which the excitation light emitted from the laser diode is supplied to the solid-state laser medium from the side through the window of the cooling tube, at least a part of the peripheral surface area excluding the window of the cooling tube In addition, a reflection layer that reflects the excitation light toward the solid-state laser medium is integrally provided.

As described above, by providing the reflection layer for increasing the utilization efficiency of the excitation light in the cooling tube itself through which the cooling medium for cooling the laser medium flows, the separate reflector 6 is arranged outside the cooling tube. It is no longer necessary to solve the above problems.

The shape of the solid-state laser medium may be either a slab shape or a rod shape. In addition, the reflective layer may be provided on the entire peripheral surface area excluding the window portion, or may be provided only on a part (for example, for half a circumference). Further, the reflection layer may be provided on either the outer peripheral surface or the inner peripheral surface of the cooling pipe.

The material of the reflection film is preferably selected in consideration of high reflectance to excitation light and chemical stability (corrosion resistance). Suitable materials include gold (Au), silver (Ag), aluminum (Al), and a dielectric material having a high reflectivity as a main component.
The film mainly composed of u) has excellent reflection characteristics and corrosion resistance. Layers composed of these films can be formed by a known film forming technique such as vacuum evaporation.

[0016]

1 and 2 are views for explaining a main structure of an LD-pumped solid-state laser oscillation device according to one embodiment of the present invention. FIG. 1 shows a longitudinal axis of an optical resonator. 2 is shown in FIG. 2, and a cross section along a plane perpendicular to the axis (see XX) is shown. In both figures, reference numeral 1 denotes an output mirror (partially reflecting mirror) 7 and a rear mirror (total reflecting mirror) 8
Represents a laser medium disposed in the optical resonator constituted by. The laser output light 9 is output from an output mirror (partial reflection mirror) 7.
Is taken out to the outside.

The laser medium 1 used in the present embodiment
Is a slab-shaped (flat bar-shaped) Nd; YAG laser crystal. Both end faces of the laser medium 1 are cut obliquely in the thickness direction at an angle satisfying the Brewster condition in order to keep the efficiency of the optical resonator high. As is well known, a zigzag optical path that repeats total reflection is formed inside the slab type laser medium 1.

Reference numeral 20 denotes a cooling pipe provided to prevent the temperature of the laser medium 1 from rising.
3, a cooling medium 11 such as pure water is circulated. The laser medium 1 is arranged so as to be in direct contact with the cooling medium 11 as in the related art. The cooling pipe 20 has a window 20 a for taking in the excitation light 4 radiated from the LD 3 arranged on the side, while the outer peripheral surface of the part except the window 20 a is almost entirely covered with the reflective layer 21. ing. Note that the area covered by the reflection layer 21 is from the LD 3 to the excitation light 4.
May be only a part of the outer peripheral surface of the portion excluding the window portion 20a (for example, a half circumference indicated by ABC).

The reflection surface 21a provided on the inner side (the side facing the laser medium 1) by the reflection layer 21 is not provided by an external reflector as in the prior art (see FIG. 4), but is made of a transparent material. The cooling pipe 20 is provided integrally with the base material of the cooling pipe 20 so that the cooling pipe 20 itself has a reflection function. In that sense, the reflective layer 21 may be formed on the inner surface 20b of the cooling pipe 20. A region where the reflective layer 21 is provided on the outer peripheral surface and a region where the reflective layer 21 is provided on the inner peripheral surface may coexist.

The characteristics desired for the reflective layer 21 are high reflectance to excitation light and chemical stability (corrosion resistance). Suitable materials include those containing gold (Au), silver (Ag), aluminum (Al), or the like as a main component. Among them, a film containing gold (Au) as a main component has both reflection characteristics and corrosion resistance. Are better. Gold-based films can be used for vacuum deposition, etc.
The cooling tube 20 can be formed to have a desired thickness on a transparent substrate (for example, optical glass or heat-resistant transparent plastic) by a well-known film forming technique.

It goes without saying that the reflection layer 21 may be formed on the outer surface or the inner surface of the cooling tube 20 by a known film forming technique such as vacuum deposition of a material other than gold, such as silver or aluminum. A dielectric having a high reflectance (for example, MgF ₂ ) may be used other than the metal. In addition, a technique other than vacuum deposition (eg, plating, printing, foil fixing using an optical adhesive, or the like) may be used for forming the layer.

In the configuration of the present embodiment, the excitation light 4 emitted from the LD 3 enters the slab-shaped laser medium 1 via the window 20a and the cooling medium 11. A substantial part of the excitation light incident on the laser medium 1 is absorbed by the laser medium 1 and used for laser excitation (optical pumping) of the laser medium 1, but a part of the excitation light is transmitted to the back side without being absorbed by the laser medium 1. Then, the light enters the cooling pipe (government wall member) 20 through the cooling medium 11 from inside. The excitation light that has entered the transparent base material (for example, optical glass) of the cooling pipe 20 does not pass through the air layer (gap),
The light reaches the reflection surface 21a of the reflection layer 21.

Most of the excitation light 4 incident on the light reflection surface 21a having a high reflectance with respect to the excitation light 4 is reflected and travels backward through the transparent base material (for example, optical glass) of the cooling pipe 20, The laser medium 2 returns to the laser medium 2 via the cooling medium 11, and a part thereof is absorbed by the laser medium 2 and is effectively used for laser excitation.

The reflection layer 21 is provided on the inner surface 20 of the cooling pipe 20.
In the case where the excitation light 4 is provided on the laser medium 1, the excitation light 4 transmitted through the laser medium 1 is immediately reflected by the inner reflection surface of the reflection layer after passing through the cooling medium 11, and reenters the laser medium 2 through the cooling medium 11.

As described above, in the LD-pumped solid-state laser oscillation device of the present embodiment, the cooling pipe 20 itself through which the cooling medium 11 for cooling the laser medium 1 forms a reflection layer for improving the utilization efficiency of the excitation light 4. Have. Therefore, there is no need to dispose a separate reflector 6 outside the cooling pipe 40 as in the conventional structure, and the apparatus can be made compact. Further, an additional cooling medium flow path for cooling the reflector 6 (see 6b to 6e in FIG. 4) is not required. Of course, the problem of corrosion of the reflector due to the provision of the cooling medium flow path does not occur.

Reflective layer 2 provided in place of conventional reflector
It is considered that the temperature rising phenomenon naturally occurs in the case of No. 1. But,
The cooling action of the cooling medium 11 flowing through the cooling pipe 20 is performed via the transparent base material of the cooling pipe 40 or directly (by the cooling pipe 2).
(In the case where a reflective layer is provided on the inner surface 20b), it is easy to secure a space for promoting heat radiation from the back surface side of the reflective layer 21. Therefore, even in the case of a high-power laser, the need for a special configuration for preventing the temperature rise of the reflection layer 21 is reduced.

Although the embodiment using the slab-shaped laser medium 1 has been described above, the present invention can of course be applied to an LD-excited solid-state laser oscillation device using a rod-shaped laser medium. FIG. 3 is a cross-sectional view showing the example in the same format as that of FIG.

In FIG. 3, except that a rod-shaped laser medium 2 is used and excitation light is supplied through a converging lens 12, the embodiment described with reference to FIGS. There is no particular difference from the form. That is, the cooling pipe 30 through which the cooling medium 11 for preventing the temperature rise of the rod-shaped laser medium 2 flows is provided with a window for taking in the excitation light 4 radiated from the LD 3 arranged on the side through the lens 12. While having the portion 30a, the outer peripheral surface of the portion other than the window portion 30a is almost entirely covered with the reflective layer 31. In addition,
The area covered by the reflective layer 31 is a part of the outer peripheral surface of a portion excluding the window 30a for taking in the excitation light 4 from the LD 3 via the lens 12 (for example, a half circumference indicated by ABC).
It may be only.

The reflection surface 21a inside the reflection layer 31 is provided integrally with the base material of the cooling pipe 30 made of a transparent material.
This is for providing the cooling function to the cooling pipe 30 itself. The reflection layer 31 may be formed on the inner side surface 30b of the cooling pipe 30. The material and forming method of the reflective layer 31 are the same as those of the reflective layer 21 in the above-described embodiment.

The excitation light 4 emitted from the LD 3 enters the rod-shaped laser medium 2 through the lens 12, the window 30a, and the cooling medium 11. A substantial part of the excitation light incident on the laser medium 2 is absorbed by the laser medium 2 and used for laser excitation (optical pumping) of the laser medium 2, but a part of the excitation light is transmitted to the back side without being absorbed by the laser medium 2. Then, the light enters the cooling pipe (government wall member) 30a through the cooling medium 11 from the inside.

The excitation light that has entered the transparent substrate (for example, optical glass) of the cooling pipe 30 is reflected by the reflection surface 31 a of the reflection layer 31.
To reach. Most of the excitation light 4 incident on the light reflecting surface 31a having a high reflectance with respect to the excitation light 4 is reflected and travels backward in the transparent base material (for example, optical glass) of the cooling pipe 30 to form the cooling medium 11. Through the laser medium 2 again, a part of which is absorbed by the laser medium 2 and is effectively used for laser excitation.

The reflection layer 31 is provided on the inner surface 2 of the cooling pipe 40a.
In a case where the excitation light 4 is provided on the laser medium 2, the excitation light 4 transmitted through the laser medium 2 is immediately reflected by the inner reflection surface of the reflection layer after passing through the cooling medium 11, and reenters the laser medium 2 through the cooling medium 11.

As described above, also in the LD-pumped solid-state laser oscillation device of this embodiment, the cooling pipe 30 through which the cooling medium 11 for cooling the laser medium 2 flows is formed by the reflection layer 31 for improving the efficiency of using the pumping light 4. It has. Therefore, unlike the conventional structure, there is no need to arrange a separate reflector outside the cooling pipe, and the apparatus can be made compact. Also, an additional cooling medium flow path for cooling the reflector is not required.

[0034]

According to the present invention, the cooling pipe for passing the cooling medium for cooling the laser medium of the LD-excited solid-state laser oscillation device has a high reflection function for reusing the transmitted light of the laser medium. An LD-pumped solid-state laser oscillation device capable of efficiently absorbing pumping light into a laser medium with a simple configuration as compared with the related art is realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view taken along a longitudinal axis of an optical resonator showing a main structure of an LD-pumped solid-state laser oscillation device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a principal part of the LD-pumped solid-state laser oscillation device shown in FIG.
-X) in a cross-sectional view.

FIG. 3 is a cross-sectional view illustrating a main part structure of an LD-pumped solid-state laser oscillation device according to an embodiment using a rod-shaped laser medium in the same manner as in FIG.

FIG. 4 is a cross-sectional view perpendicular to a longitudinal axis of an optical resonator, showing a main structure of a conventional side-pumped LD-pumped solid-state laser oscillation device using a slab-shaped laser medium.

[Explanation of symbols]

 Reference Signs List 1 slab type laser medium 2 rod type laser medium 3 LD (laser diode) 4 excitation light (arrow group) 5 air layer (gap) 6 reflector 6a reflection surface 6b-6e cooling medium flow path 7 output mirror 8 rear mirror 9 laser Output light 11 Cooling medium 12 Lens 20, 30, 40 Cooling tube 20a, 30a Window 20b, 30b Inner surface of cooling tube 21, 31 Reflective layer 21a, 31a, 40a Reflective surface

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hisadachu Machida 3580 Kobaba, Oshino-mura, Oshino-mura, Minamitsuru-gun Yamanashi Prefecture Inside FANUC CORPORATION Inside FANUC CORPORATION

Claims (7)

[Claims] 1. A solid-state laser medium is disposed in an optical resonator,
A cooling pipe for flowing a cooling medium for cooling the solid-state laser medium is provided, and the excitation light emitted from a laser diode for laser-exciting the solid-state laser medium is passed through a window of the cooling pipe from a side of the solid-state laser medium. In the solid-state laser oscillation device, a reflection layer that reflects excitation light toward the solid-state laser medium is integrally formed on at least a part of the peripheral surface area excluding the window of the cooling pipe. The solid-state laser oscillation device provided. 2. A slab-shaped solid laser medium is disposed in an optical resonator, a cooling pipe for flowing a cooling medium for cooling the solid laser medium is provided, and a laser diode is provided to excite the solid laser medium by laser. In the solid-state laser oscillation device configured to supply the emitted excitation light to the solid-state laser medium from the side through the window of the cooling pipe, at least a part of a peripheral surface area excluding the window of the cooling pipe. The solid-state laser oscillator according to claim 1, wherein a reflection layer that reflects the excitation light toward the solid-state laser medium is provided integrally. 3. A solid-state laser medium having a rod shape is disposed in an optical resonator, a cooling pipe is provided for flowing a cooling medium for cooling the solid-state laser medium, and a laser diode is provided to excite the solid-state laser medium with a laser. In the solid-state laser oscillation device configured to supply the emitted excitation light to the solid-state laser medium from the side through the window of the cooling pipe, at least a part of a peripheral surface area excluding the window of the cooling pipe. The solid-state laser oscillator according to claim 1, wherein a reflection layer that reflects the excitation light toward the solid-state laser medium is provided integrally. 4. The solid-state laser according to claim 1, wherein the reflection layer is provided on an entire peripheral surface area of the cooling pipe excluding the window. Oscillator. 5. The solid-state laser oscillation device according to claim 1, wherein the reflection layer is provided on an outer peripheral surface of the cooling pipe. 6. The solid-state laser oscillation device according to claim 1, wherein the reflection layer is provided on an inner peripheral surface of the cooling pipe. 7. The solid-state laser oscillation device according to claim 1, wherein the reflection layer includes a reflection film containing gold as a main component.