JPH0316284A - Semiconductor laser excitated solid state laser device - Google Patents

Abstract

PURPOSE:To improve combination efficiency, to improve excitation efficiency and to realize high output by setting an optical path of a YAG laser beam and that of a semiconductor laser beam to coincide each other in a laser medium of a solid state laser device of polygonal pole type. CONSTITUTION:An optical path of a YAG laser beam and that of a semiconductor laser beam are made to coincide each other inside a YAG rod 1 by setting an incident angle (a reflection angle) thetaYAG of the YAG laser beam at the side of the YAG rod 1 to a critical angle thetaC=33.3 deg. or less to make an optical path of the semiconductor laser beam coincide with that of YAG laser beam. An incident angle of YAG laser beam can be made 33.3 deg. or less only by making sides of the YAG rod 1 cross at 60 deg. each other. Excitaton efficiency can be improved by matching semiconductor laser beams respectively against an incident light and a reflection light at each point of reflection of the YAG laser beam. Thereby, a YAG laser of high efficiency and high output can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-output solid-state laser device excited by a semiconductor laser, which can be used for processing metals, semiconductors, ceramics, etc., and for medical purposes as a coagulator.

Conventional technology Arc lamps, flash lamps, etc. have traditionally been used to excite solid-state laser devices, but since they contain a large amount of spectrum other than those that contribute to excitation, the excitation efficiency is poor, and from the standpoint of heat dissipation from the lamp and laser medium. The equipment had to be large. However, in recent years, as semiconductor lasers have become more powerful, attempts have been made to use them as excitation light sources for solid-state lasers. When a semiconductor laser is used, the wavelength can be matched to the absorption band of a solid-state laser, so the excitation efficiency is good, and heat dissipation is facilitated because there is no heat generation due to absorption of excess spectrum.

Therefore, one of the methods that has been tried many times in recent years is a method called shaft end face excitation as shown in FIG. This method uses Nd
: The light from the semiconductor laser 5 is focused on the end face of the YAG rod 4 by a condenser lens 6 and excited. The resonator reflects externally! ! 13 and the excitation side end surface of the YAG rod 4. In this method, since the coupling efficiency of the YAG laser light and the semiconductor laser light is high, efficient excitation can be achieved, and moreover, it can be stably operated in the T E Moo mode. However, since there are only 11 points that can be excited, Y
In order to improve the output of AG laser light, it is essential to increase the output of the semiconductor laser, and there is a problem that the output is limited by the output of the semiconductor laser.

A method proposed to solve this problem is a method in which the YAG laser beam is reflected on each side of a hexagonal prism-shaped YAG rod, as shown in Figure 8, so that the YAG laser beam draws a spiral optical path. It is. By using this method, the reflection points on each surface can be used as excitation points, which overcomes the drawback of the conventionally known axial excitation method (Figure 7) that there is only one excitation point, and it is also stable. It can be operated in TEMoo mode.

Problems to be Solved by the Invention However, in the hexagonal prism YAG laser shown in FIG.
The optical path of the YAG laser beam within the G rod and the optical path of the semiconductor laser beam, which is excitation light, do not match. Therefore, the coupling efficiency is not sufficient, which hinders the improvement of excitation efficiency. Poor excitation efficiency poses a problem in terms of heat dissipation when increasing output.

Means for Solving the Problems In the present invention, in order to increase the coupling efficiency, the optical paths of the YAG laser light and the semiconductor laser light within the YAG rod must be matched. For this purpose, as shown in Figure 4, Y
Incident angle (reflection angle) of YAG laser beam on the side of the AG rod
QYAO is the critical angle θc( s i rr' (nA+r
/nvAa)=33.3(d e g+) or less, otherwise the semiconductor laser light cannot be aligned with the optical path of the YAG laser light. In order to make the angle of incidence and reflection of the YAG laser beam 33.3 degrees or less, the side surfaces of the YAG rods should intersect with each other at 60 degrees.

Furthermore, as shown in FIG. 4, excitation efficiency can be increased by matching the semiconductor laser light to the incident light and reflected light at each reflection point of the YAG laser light.

Effect As described above, by matching the optical paths of the YAG laser beam and the semiconductor laser beam in the polygonal YAG rod, the coupling efficiency can be improved and efficient excitation can be achieved. With this structure, it is highly efficient and can be used for processing metals, etc. A high-output semiconductor laser pumped YAG laser can be realized.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a structural diagram of a semiconductor laser pumped solid-state laser device of the present invention. Nd j Y processed into a hexagonal column shape
In the AG rod 1, as shown in FIG. 2, the YAG laser beam (thin line) is reflected by 3g4 planes that intersect at 60 degrees, so that it travels while drawing a spiral optical path. As shown in the sketch of FIG. 3, this hexagonal prism-shaped YAG rod has a hexagonal bottom surface with a length of 6 m and alternating sides of 22 mm, and a height of 50 mm.

The resonator is formed by a reflecting surface 1-1 formed on the bottom surface of a YAG rod and an external reflecting mirror 3. The reflective surface 1-1 and the output surface 1-2 formed on the bottom surface of the YAG rod are at an angle θ#4.4 degrees with respect to the normal direction of the bottom surface of the YAG rod so that the optical path of the YAG ray becomes a spiral shape. The YAG laser beam is incident on the reflection surface 1-1 and the emission surface 1-2 perpendicularly. The reflecting surface 1-1 is a flat surface and has a reflectance of 99% or more for a wavelength of 1.06 μm, and the output surface 1-2 is a flat surface and has a reflectance of 99% for a wavelength of 1.06 μm.
Has a transmittance of 0% or more. Another external reflection lol! ．． 3 has a radius of curvature of 1.5 m and is 80% for a wavelength of 1.06 μm.
It has a reflectance of side (
The excitation surface 1-3) has a transmittance of 90% or more for an excitation wavelength of 809 μm and a reflectance of 99% or more for a wavelength of 1.06 μm. The excitation point by the semiconductor laser beam is the second
As shown in the figure and Fig. 3, the YAG laser beam
This corresponds to the point reflected on the side of the AG rod. this·
FIG. 4 shows the state of YAG laser light and semiconductor laser light at the points indicated by marks. In order to improve excitation efficiency, it is desirable that the optical paths of the YAG laser beam and the semiconductor laser beam coincide. Therefore, in this embodiment, the YAG laser beam is directed at an angle θYA (1=
3 0.3 (d e gt), and the semiconductor laser light is incident and reflected at an angle θ+. o=66.6 (de
g+), the optical paths are made to coincide. In addition, in order to increase excitation efficiency, semiconductor laser light is incident on one reflection point (marked with a *) from two directions so that both the incident light and reflected light of the YAG laser light are excited. . By the way, the incident and reflection angle θY of the YAG laser beam
The incident angle θLD between AG and the semiconductor laser is the hexagonal prism angle YAG.
It is determined by the inclination θ of the resonator with respect to the height direction of the rod. The relationship between this angle θ, θYAG, and θLD is shown in the fifth
It is a diagram. The maximum angle of incidence angle θYAO of YAG laser beam is determined by the critical angle of total reflection, θYAG = 33.3 (deg
+). Therefore, the reflective sides are 60 (de) from each other.
The relationship must intersect at g+).

FIG. 6 shows the input/output characteristics of this embodiment under the above configuration. In this device, the semiconductor laser light for excitation is guided through an optical fiber, and the semiconductor laser is cooled by a Peltier element. Also, since there are 27ii excitation points,
Excitation was performed using a total of 54 semiconductor lasers. As shown in FIG. 6, an output of 8.5 W was obtained for an input of 20 W. Note that when the input exceeds 14 W, the output becomes saturated, but this is thought to be due to heat. This can be improved by improving the heat dissipation of the YAG rod.

Effects of the Invention The present invention provides Y in the laser medium of a polygonal solid state laser device.
The coupling efficiency is improved by setting the optical paths of the AG laser light and the semiconductor laser light to match. Improving coupling efficiency increases excitation efficiency and increases output power.

The present invention has great effects as a solid-state laser for processing and medical applications that require high output.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of a semiconductor laser pumped solid-state laser device of the present invention, Fig. 2 is a diagram illustrating the optical path of a laser beam in a solid-state laser medium that is a part of the device of the present invention, and Fig. 3 is a diagram of the present invention. Schematic diagram of the solid-state laser medium that is part of the device, No. 4
The figure shows the incident angles of YAG laser light and semiconductor laser light on the reflective side of the solid-state laser medium that is part of the device of the present invention.
FIG. 5 is a diagram illustrating the relationship between reflection angles, and FIG. θ and the incident angle θY of the YAG laser beam shown in Figure 4.
A diagram showing the relationship between the incident angle θLD of AG and semiconductor laser light, FIG. 6 is an input/output characteristic diagram of the device of the present invention, FIG. 7 is a structural diagram of a conventional axially pumped solid-state laser device, and FIG. 8 is a diagram of the conventional axially pumped solid-state laser device. FIG. 2 is a structural diagram of a polygonal column type solid-state laser device. 1...Hexagonal column type Nd: YAG rod, 1-
1...Reflection surface, 1-2...Emission surface, 1
-3...Excitation surface (reflection side), 2...
Optical fiber with condensing lens, 3... External reflecting mirror, 4... Nd: YAG rod, 5...
... Semiconductor laser, 6... Condensing lens.

Claims (1)

[Claims] A resonator is formed so that solid-state laser light travels along a spiral optical path in a polygonal solid-state laser medium having three sides that intersect with each other at 60 degrees,
The resonator is provided on the bottom surface, side surface, or outside of the polygonal solid-state laser medium, and the resonator surface is at an angle of 0 degrees or more and 15.3 degrees with respect to the normal direction of the bottom surface of the polygonal solid-state laser medium. The angle of incidence is 65.5 degrees or more so that the semiconductor laser beam is aligned with the optical path of the solid-state laser beam at the point where the solid-state laser beam is reflected by each side surface of the polygonal solid-state laser medium. A semiconductor laser-excited solid-state laser device characterized by condensing and exciting light at 90.0 degrees or less.