JPS6037632B2 - Solid state laser oscillator - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in solid-state laser devices.

[Technical background of the invention and its problems]

In a solid-state laser device, the laser rod is optically excited while being cooled with cooling water, but when the optical excitation is in a steady state, the center of the laser rod is hotter than the outer circumference, which is cooled, and the laser rod is heated by the lens. produce an effect.

However, a phenomenon often occurs in which this lens action is not axially symmetrical with respect to the laser rod axis. This is caused by the fact that the laser rod is not used under conditions where it receives uniform optical excitation from the surroundings, or by the non-uniformity of the laser rod itself. To explain the above point with reference to FIG. 1, if the axial direction of the laser rod 3 housed together with the excitation lamp 2 in the elliptical reflector 1 is taken as the Z axis, the action of the laser rod 3 in the x and y directions is is different. That is, as shown in FIG. 2, where the vertical axis is the rear focal length and the horizontal axis is the excitation input pi, in the x direction and the y direction, there is a convergence effect of 戊, fy, which becomes shorter as the excitation input pj increases, Does not exhibit axially symmetric optical properties. Since it is not axially symmetrical, when condensing the beam, the machining characteristics change depending on the scanning direction due to the biased condensed spot. In order to make the focused spot uniform and axially symmetrical, it is possible to install multiple excitation lamps equally around one laser rod and excite the light from the surrounding area with uniform intensity, or to place the laser rod in an IJ cal shape. There is a technology for optically excitation by inserting it into an excitation lamp, but both have low oscillation efficiency and it is difficult to replace the excitation lamp, which poses a practical problem. Furthermore, in a configuration in which a laser rod and an excitation lamp are arranged one-to-one, the surface of the laser rod facing the excitation lamp becomes hotter than the other surface, and the laser rod physically bends and the optical path inevitably bends. Therefore, it is necessary to readjust the optical axis of the laser resonator mirror every time the excitation intensity changes. [Object of the Invention] An object of the present invention is to provide a stable laser device in which the laser rod is less likely to cause lens action and the asymmetric characteristics of the output laser beam are improved.

[Summary of the invention] The surface of the laser rod opposite to the side facing the excitation lamp is made rough to promote heat dissipation, thereby minimizing the temperature difference at the outer periphery of the laser rod and preventing bending of the laser rod. It was designed to do so.

Furthermore, the light scattering ability of the optical excitation light on the surface of the scissor rod is varied to make the heat generation inside the rod symmetrical and uniform with respect to the rod axis. [Embodiments of the Invention] The present invention will be described based on drawings showing embodiments.

FIG. 3 shows an example of a solid-state laser oscillation device with single-sided excitation, which is the first embodiment of the present invention. That is, an excitation lamp 11 and a laser rod 12 are provided coaxially and parallel to the focal point of the elliptical reflector 1 on the elliptical reflector 1 which is made of a segmented body and has a highly reflective inner surface. Shi-Therod 1
The side facing the excitation lamp 11 of No. 2, that is, the direction connecting the center of the cross section of the laser rod 12 with 0 and the center of the cross section of the excitation lamp 11 with 02 is x, and the direction perpendicular to the x direction is Y. Then, the 1× side is left as a smooth surface 13, and the opposite 10× side is formed into a rough surface 14 of about 0.1 side. With the above configuration, the surface that is most strongly hit by the excitation light from the excitation lamp 11 is the smooth surface 14, so the excitation light travels straight inward and is scattered by the rough surface 13 on the opposite side. Helps prevent heat buildup and temperature rise near the area. Therefore, the temperature distribution of the part far from the excitation lamp 11 and the part that is strongly excited near the excitation lamp 11 is balanced, and the conventional bending phenomenon of the laser rod due to imbalance in heat distribution is eliminated. FIG. 4 shows a second embodiment of the present invention, in which 15 is a double elliptical reflector, a laser rod 16 is provided on the common focus of this reflector, and is excited by two excitation lamps 11, 11. It is configured.

In this embodiment, the excitation lamps 11,1 of the laser rod 16 are
A part of the surfaces facing each side 1 is a smooth surface 18. Further, the surface in the y direction is finished to have a rougher surface 19. In the second embodiment, as in the first embodiment, the rough surfaces 19, 19 have a larger temperature increasing effect than other surfaces, so even if the light from the excitation lamp 11 has a long reach, the result is The temperature rise is about the same as that of the smooth surface 18 that is strongly hit by the excitation light, and the temperature distribution is balanced.

Note that instead of forming a rough surface, a deposited film may be formed that transmits spectral components effective for optical excitation of the laser rod and absorbs other wavelengths.

In addition, the surface of the laser rod may be coated with a vitreous material whose thermal conductivity is lower than that of the laser rod to allow the excitation light to pass therethrough. By the way, instead of keeping the heat generating part near the surface due to rough surface formation etc. away from the excitation lamp, for example, in the second embodiment above, the assembly surface is placed in the x direction to emphasize the difference between 戊 and fy. Good too. In this case, since an elliptical spot is obtained, it is suitable for processing in which the laser beam is scanned in the elliptical direction for welding. [Effects of the Invention] Optical uniformity was improved under the thermal action of the laser rod under conditions of low to high excitation intensity, and an oscillation pattern with a circular cross section could be obtained even at high output.

In addition, in the case of a laser rod with poor axial symmetry, in order to improve the defect, it is possible to actively form a part with a difference in surface finish in the corresponding part to compensate for optical non-uniformity. . Furthermore, it is also possible to obtain an oscillation pattern suitable for processing by changing the position of the heat dissipation portion using a rough surface or the like.
Brief explanation of the drawings Figure 1 is a cross-sectional view showing a conventional example, Figure 2 is a cross-sectional view showing a conventional example;
The figure is a diagram showing the relationship between input power and focal length for each direction in a follow-up example, FIG. 3 is a cross-sectional view showing the first embodiment of the invention, and FIG. 4 is a diagram showing the second embodiment of the invention. FIG. 3 is a cross-sectional view showing an example.

1...Elliptical reflector, 11...Excitation lamp,
12, 16... Laser rod, 14, 18... Rough surface.

Younger brother 1 Figure 2 [many] figure Multi 4 figures

Claims (1)

[Scope of Claims] 1. A solid-state laser oscillator having a laser head section including an excitation lamp and a laser rod excited by the excitation lamp inside an elliptical reflector, wherein the laser rod has a surface on a part of its outer peripheral surface. A solid-state laser oscillation device characterized by providing a temperature rise control portion that has a rougher surface. 2. The solid-state laser oscillation device according to claim 1, wherein the temperature rise control portion is formed along the length direction. 3. The solid-state laser oscillation device according to claim 1, wherein the temperature rise control portion does not face the excitation lamp. 4. The solid-state laser oscillation device according to claim 1, wherein the temperature rise control portion is formed over substantially the entire length of the laser rod along the axial direction. 5. The solid-state laser oscillation device according to claim 1, wherein the temperature rise control portion is formed of a material other than the material of the laser rod that transmits optical excitation light. 6. The solid-state laser oscillation device according to claim 1, wherein the temperature rise control portion is installed in a direction that compensates for non-uniformity of the rod during optical excitation.