JPH09232652A - Solid-state laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a solid-state laser device which is made stable in laser characteristics by a method wherein a flow of cooling medium is set uniform around a laser medium. SOLUTION: A laser medium 1 is held by a laser medium holder 3 inside an oscillator structure. Cooling medium for cooling the laser medium 1 is introduced into an inlet path 12 with an inlet 12a provided to the side of the oscillator structure near its one edge and discharged out through an outlet path 13 passing through a flow path 11 formed around the laser medium 1 in the axial direction of the laser medium 1. An axial impeller 10 is provided in the flow path of coolant medium at the upstream part of the laser medium 1 on the same axis with the laser medium 1.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a solid-state laser device,
In particular, the present invention relates to a solid-state laser apparatus suitable for irradiating a workpiece with laser light to perform processing such as melting, joining, boring, annealing, and the like of metals, and marking processing of semiconductor packages.

[0002]

2. Description of the Related Art A high-power solid-state laser device such as a YAG laser or a glass laser is composed of a solid-state laser medium for emitting a laser beam, a pumping lamp for exciting the solid-state laser medium, and the like. In the excitation by the lamp, the ratio of energy that can be taken out as laser light is low with respect to the electric power that is applied to the lamp, and most of the applied power is converted into heat. In particular, since the laser medium has a risk of being destroyed by the temperature distribution generated by the heat generated by photoexcitation, the cooling medium is brought into direct contact with the laser medium to cool the laser medium.

FIG. 5 shows a sectional view of a conventional solid-state laser device. In FIG. 5, a laser medium 101 is fixed inside a oscillator body 102, which is a tubular body, with both ends thereof being held by a laser medium holder 103. Further, a reflecting mirror 105 for concentrating the pumping light from a pumping lamp (not shown) arranged in parallel with the laser medium 101 on the laser medium 101 is arranged inside the oscillator structure, and is used for pumping. The laser medium 101 performs laser oscillation by absorbing the excitation light from the lamp.

A glass tube 10 is provided around the laser medium 101.
4 is arranged, and a flow path through which the cooling medium passes is formed between the glass tube 104 and the laser medium 101. The flow path is formed along the axial direction of the laser medium, and the laser medium 101 is cooled by flowing a cooling medium through this flow path. Here, since it is necessary to emit laser light from the end surface of the laser medium 101 and in order to reduce the structure of the oscillator assembly 102, the introduction path 1 for introducing the cooling medium into the flow path.
12 and a discharge path 11 for discharging the cooling medium from the flow path
3 are provided substantially perpendicular to the axial direction of the laser medium 101.

In general, a laser medium 10 that absorbs excitation light
In No. 1, part of the absorbed energy becomes heat. Therefore, when the pumping light is strengthened to obtain a larger output, the thermal stress caused by the temperature distribution at this time not only causes fluctuations in the laser characteristics, but also may destroy the laser medium. .

Therefore, in order to make the temperature distribution in the flow passage uniform and to cool the laser medium uniformly, Japanese Patent Laid-Open No. 5-32707.
Japanese Patent Publication No. 3 discloses a solid-state laser device in which the cross-sectional area of the flow path around the laser medium is uniform.

[0007]

As described above, since the cooling medium is introduced into the cooling medium introducing passage substantially perpendicularly to the axial direction of the laser medium, the cooling medium is introduced at the end portion of the passage on the side of the cooling medium introducing passage. The flow direction of the cooling medium is rapidly changed, and the flow of the cooling medium in the flow path becomes uneven. The cooling of the laser medium is performed by contacting the laser medium with the cooling medium and transferring the heat of the laser medium to the cooling medium. Generally, this heat transfer amount depends on the flow velocity and the temperature of the cooling medium. If the flow of the cooling medium becomes non-uniform, the temperature distribution around the axis of the laser medium becomes non-uniform. The temperature distribution around the axis of the laser medium is axisymmetric when it is ideally cooled, but it is not axisymmetric when the flow of the cooling medium is uneven. Therefore, the non-uniformity of the flow of the cooling medium at the cooling medium introduction path side end of the flow path cannot be avoided only by making the cross-sectional area of the flow path around the laser medium uniform.

Such non-uniformity of the flow of the cooling medium becomes more remarkable when the excitation light is increased and the laser output is increased. As a result, problems such as a decrease in laser output, a mode change of the output laser light, or a change in the output direction of the laser light are caused.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a solid-state laser device in which the flow of the cooling medium around the laser medium is made uniform and stable laser output characteristics can be obtained.

[0010]

In order to achieve the above object, the solid-state laser device of the present invention is such that a rod-type laser medium is held inside a tubular body, and a cooling medium is used to cool the laser medium. In a solid-state laser device in which a path that flows along the axial direction of the laser medium is formed around the laser medium after being introduced into the tube from the side surface of the tube, the laser in the path through which the cooling medium flows. An axial flow type impeller is arranged coaxially with the laser medium upstream of the medium.

In the solid-state laser device configured as described above, the cooling medium is introduced from the side surface of the tubular body and then flows around the laser medium along the axial direction of the laser medium to cool the laser medium. When the cooling medium introduced from the side surface of the tubular body flows in the axial direction of the laser medium, the flow of the cooling medium is disturbed due to the change in the direction of the flow of the cooling medium. Here, since the axial flow type impeller is arranged upstream of the laser medium, the cooling medium passing through the impeller advances while rotating around the axis of the laser medium. As a result, the flow of the cooling medium around the laser medium is stabilized and the laser medium is cooled uniformly.

The impeller can be fixed to the tube body or can be rotatably provided. In particular, since the impeller is rotated by the pressure of the cooling medium by rotatably providing it, the flow of the cooling medium is further stabilized.

Further, by forming a circular space having a diameter larger than the outer diameter of the impeller coaxially with the impeller, the space serves as a cooling medium reservoir. Therefore, the cooling medium has a reduced flow velocity in the space and is supplied to the impeller, so that the function of the impeller is more effectively exhibited.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the solid-state laser device of the present invention. In FIG. 4, the rod-shaped laser medium 1 is fixed inside the oscillator assembly 2 which is a tubular body by holding both ends of the rod-shaped laser medium 1 by the laser medium holder 3.
The laser medium 1 is made of Nd: YAG (nedium-doped yttrium-aluminum-garnet) crystal. Further, a reflecting mirror 5 for focusing the excitation light from a flash lamp (not shown) arranged in parallel with the laser medium 1 on the laser medium 1 is arranged inside the oscillator structure 2, and the flash lamp By absorbing the excitation light from the laser medium 1, the laser medium 1 performs laser oscillation.

A glass tube 4 is arranged on the outer periphery of the laser medium 1, and a flow path 11 through which a cooling medium passes is formed between the glass tube 4 and the laser medium 1. The channel 11 is formed along the axial direction of the laser medium 1, and the cooling medium is the laser medium 1.
Along the flow path. At one end of the oscillator structure 2, an introduction path 12 that connects the inlet 12a opening to the side surface of the oscillator structure 2 and the flow path 11 is formed. Similarly, at the other end of the oscillator assembly 2, a lead-out path 1 that connects the outlet 13a opening on the side surface of the oscillator assembly 2 and the flow path 11 to each other.
3 are formed. The introduction path 12, the flow path 11 and the discharge path 13 constitute a path through which the cooling medium flows. Water is used as the cooling medium. The inlet 12a and the outlet 13a are provided on the side surface of the oscillator assembly 2 because the laser light needs to be emitted from the end surface of the laser medium 1 and the structure of the oscillator assembly 2 is reduced, as described above.

An axial flow type impeller 10 is arranged upstream of the laser medium 1 in the path through which the cooling medium flows. As shown in FIG. 2, the impeller 10 includes an outer ring 10a and an inner ring 10b that are coaxially arranged, an outer ring 10a, and an inner ring 1.
0b and a plurality of blades 1 radially arranged and fixed between
0c and. Then, the outer ring 10a is fixed to the oscillator structure 2, and the laser medium holder 3 on the introduction path 12 side is fitted to the inner ring 10b, whereby the impeller 1
0 is fixed coaxially with the laser medium 1.

Based on the above configuration, the cooling medium introduced from the inlet 12a is supplied to the flow passage 11 through the introduction passage 12. At this time, the direction of the flow of the cooling medium is changed from the direction perpendicular to the axial direction of the laser medium 1 to the axial direction of the laser medium 1, and the flow of the cooling medium is disturbed. Here, since the impeller 10 is arranged upstream of the laser medium 1,
The flow direction of the cooling medium is regulated by the impeller 10, and in the flow path 11, the cooling medium advances while rotating around the laser medium 1 as shown by the arrow in FIG. The cooling medium that has passed through the flow path 11 is discharged through the discharge path 13
Through the outlet 13a.

As described above, the impeller 10 applies a rotational force about the axis of the laser medium 1 to the cooling medium, so that the flow of the cooling medium in the channel 11 is made uniform. As a result, the laser medium 1 is also cooled uniformly, and stable laser output characteristics are obtained.

As the cooling medium advances in the flow passage 11, the rotation of the cooling medium gradually disappears due to energy dissipation due to friction between the cooling medium and the flow passage 11. However, this is not a problem because the flow of the cooling medium is originally uniform except on the upstream side of the flow path 11.

FIG. 4 is a sectional view of another embodiment of the solid-state laser device of the present invention. In this embodiment, the cooling medium reservoir 32 is formed upstream of the impeller 30 in the path through which the cooling medium flows. The cooling medium reservoir 32 is a circular space having a diameter larger than the outer diameter of the impeller 30.
It is formed coaxially with 0. An inlet 32a for introducing the cooling medium is opened on the side surface of the cooling medium reservoir 32. The other structure is similar to that shown in FIG. 1, and therefore its explanation is omitted.

By thus forming the cooling medium reservoir 32a on the upstream side of the impeller 30, the cooling medium introduced from the inlet 32a is supplied to the impeller 30 at a reduced speed in the cooling medium reservoir 32. . Therefore, as compared with the embodiment shown in FIG. 1, the cooling medium passes through the impeller 30 in a more stable state and the function of the impeller 30 is exerted more effectively. Can be made more uniform, and the laser medium 21 can be cooled more uniformly.

In each of the above-described embodiments, the example in which the impeller is fixedly provided is shown, but the impeller may be rotatably provided and rotated by utilizing the pressure of the cooling medium. By doing so, the flow of the cooling medium around the laser medium can be more effectively made uniform.

[0024]

As described above, in the solid-state laser device of the present invention, the axial flow type impeller is arranged coaxially with the laser medium in the path through which the cooling medium flows, upstream of the laser medium. The flow of the cooling medium around the laser medium can be made uniform. As a result, the laser medium is cooled uniformly, and stable laser output characteristics can be obtained. Particularly, by rotatably providing the impeller, the flow of the cooling medium can be more effectively made uniform.

Further, the function of the impeller can be exhibited more effectively by forming a space serving as a cooling medium reservoir upstream of the impeller.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a solid-state laser device of the present invention.

FIG. 2 is a perspective view of an impeller of the solid-state laser device shown in FIG.

FIG. 3 is a diagram for explaining a flow of a cooling medium in a flow path of the solid-state laser device shown in FIG.

FIG. 4 is a sectional view of another embodiment of the solid-state laser device of the present invention.

FIG. 5 is a sectional view of a conventional solid-state laser device.

[Explanation of symbols]

 1,21 Laser medium 2 Oscillator structure 3 Laser medium holding jig 4 Glass tube 5 Reflector 10,30 Impeller 11 Flow path 12 Introduction path 13 Derivation path 32 Cooling medium reservoir

Claims (4)

[Claims] 1. A rod-shaped laser medium is held inside a tubular body, and a cooling medium is introduced into the tubular body from a side surface of the tubular body to cool the laser medium. In a solid-state laser device in which a path that flows along the axial direction of the laser medium is formed around, in the upstream of the laser medium of the path that the cooling medium flows,
A solid-state laser device, wherein an axial-flow type impeller is arranged coaxially with the laser medium. 2. The solid-state laser device according to claim 1, wherein the impeller is fixed to the tube body. 3. The solid-state laser device according to claim 2, wherein the impeller is rotatably provided on the tube body. 4. A circular space having a diameter larger than an outer diameter of the impeller is formed coaxially with the impeller upstream of the impeller in a path through which the cooling medium flows. 2. The solid-state laser device according to 2 or 3.