JPH07115237A - Solid state laser apparatus - Google Patents

Abstract

PURPOSE:To realize higher output power and improve durability with use of the reduced number of laser rods. CONSTITUTION:There are provided a reflection cylinder including a reflection surface 3 inside it, a laser rod 4 as a lower medium provided in the reflection cylinder, and an excitation lamp 5 as an excitation source in the reflection cylinder for irradiating the laser rod with the excitation light. A reflection surface of the reflection cylinder is formed with a diffusive reflector into a cylindrical configuration with a circular cross section, and at least, three of the excitation lamps 5 are disposed.

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 device using a laser rod as a laser medium and an excitation lamp as an excitation source.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a large output in this type of solid-state laser device, two methods, a method of using a plurality of laser rods arranged side by side and a method of using a plurality of excitation lamps, have been widely adopted. ing.

[0003]

However, the above-mentioned conventional method has the following problems. In the case of a high-power laser system using a plurality of laser rods arranged side by side, optical adjustment is troublesome, and there are drawbacks such as poor maintainability. Therefore, it is desirable that the number of laser rods is smaller, more preferably one.

On the other hand, in the case of a high-power laser system using one laser rod and a plurality of excitation lamps,
If two pump lamps are used to obtain a large output, the input power to the pump lamp exceeds its limit, and the problem of shortening the life of the pump lamp occurs.

Further, in general, since a specular reflection type multi-elliptical reflection cylinder is used as a reflection cylinder of a solid-state laser device, if an attempt is made to obtain a large output by using three or more pump lamps, the pumping efficiency will be lowered and it will be practical. It wasn't.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a solid-state laser device which can obtain a large output with a small number of laser rods and is excellent in durability. With the goal.

[0007]

The present invention has the following features to attain the object mentioned above. That is, the solid-state laser device of the present invention, a reflecting cylinder having a reflecting surface inside,
A laser rod as a laser medium provided inside the reflecting cylinder and an excitation lamp as an excitation source for supplying excitation light to the laser rod provided inside the reflecting cylinder are provided, and the reflecting surface of the reflecting cylinder is diffusely reflected. At least three excitation lamps were arranged in a tubular shape with a circular cross section.

Hereinafter, each structure of the present invention will be described in more detail. For the diffuse reflector constituting the reflecting surface of the reflecting cylinder of the present invention, for example, mica ceramics or fluororesin containing barium sulfate in an amount of 10 to 20% by weight can be used. As the mica ceramics, free-cutting ceramics (for example, trade name “Maselite” manufactured by Mitsui Mining Co., Ltd.) can be used, and in this case, the manufacturing process becomes easy.

The diffuse reflectance of the diffuse reflector is substantially 9
It is preferably 5% or more, and more preferably close to 100%. The fact that the diffuse reflectance is substantially 95% or more does not mean that the incident light is reflected by 95% or more, but the energy generated by the excitation lamp is repeatedly scattered in the reflecting cylinder, and the detected energy is the laser rod. To 95
% Or more means being substantially absorbed.

Further, in the present invention, it is desired that the diffuse reflectance is substantially 95% from the infrared region to the near infrared region in order to increase the excitation efficiency of the laser rod. The diffuse reflectance can be improved by coating the reflective surface with at least one of gold and silver.

As the material of the laser rod of the present invention, materials such as alexandrite, glass and ruby can be adopted in addition to the YAG material. Further, in the present invention, there is no limitation on the length or diameter of the laser rod as long as it has a rod shape (for example, a columnar shape), but particularly the rod length is 100 to 250 mm.
Therefore, a rod having a diameter of 6 to 15 mm is preferable.

The laser rod may be used by fixing and holding both ends of the laser rod with two rod holders as in the conventional solid-state laser device, but it is preferable to use the laser rod in the optical axis direction (length direction). ) So that it can be expanded and contracted. For example, one end of the laser rod is fixed and held by one rod holder, and the other end of the laser rod is held by the other rod holder so that the laser rod can be extended and contracted only in the length direction. It is preferable to use a solid-state laser device in which one rod holder (both holders may be improved) is improved.

The number of excitation lamps of the present invention is not limited to three, and may be four or five or more as long as it is three or more. A krypton type or a xenon type can be used as the excitation lamp.

The ratio of the outer diameter of the laser rod, the inner diameter of the excitation lamp, and the inner diameter of the reflecting surface of the reflecting cylinder is 1: (0.
5 to 1.5): (3.0 to 6.0) is preferable. When each diameter is within this range, a particularly high excitation efficiency is obtained, which is preferable.

[0015]

[Function] Since the light emitted from each excitation lamp is diffused and reflected by the reflecting surface of the reflecting cylinder, the amount of light that is absorbed and reflected by other excitation lamps and does not reach the laser rod is smaller than that in the case of specular reflection. Therefore, high excitation efficiency can be obtained. As a result, although the input power to the excitation lamp is lower than the input power limit, a large output of excitation light can be input to the laser rod, the life of the excitation lamp can be extended, and a large output from the solid-state laser device can be obtained. Will be able to get.

The reflecting surface of the reflecting cylinder is closer to the laser rod and the excitation lamp so that the reflecting efficiency is better. Therefore, when arranging three or more excitation lamps, a circular cross section is preferable. Further, since the cross section is circular, there is also an advantage that processing is easy. Especially, if free-cutting mica ceramics are used, it is possible to perform cutting with a precise shape.

Generally, heat is generated by optical pumping by the laser medium (laser rod), and the laser medium expands under the influence of the heat. According to the present invention, the laser rod is a laser. Since at least one end is held in the resonator in a free state so that it can be expanded and contracted in the optical axis direction of the beam, this thermal expansion amount is absorbed by the expansion of the laser rod in the optical axis direction.

More specifically, when both ends of the laser rod are held by the rod holders, one rod holder is fixed inside the resonator body, and the other rod holder is positioned relative to the resonator body. If the laser rod is free to move in the length direction and, as a result, the laser rod is allowed to extend in the length direction, this thermal expansion amount causes extension in the length direction of the laser medium that extends with the other rod holder. Be absorbed.

Further, as long as the rod holder itself holds the laser rod in a free state so that it can be expanded and contracted (moved) in the length direction, even if the rod holder is fixed to the resonator body, The rod can extend in the length direction and absorb the expansion.

In the present invention, the outer diameter of the laser rod and
As described above, the ratio of the inner diameter of the excitation lamp to the inner diameter of the reflecting surface of the reflecting cylinder is 1: (0.5 to 1.5) :( 3.0
.About.6.0) is preferable.

If the inner diameter of the pump lamp is smaller than the above range, the pump power will be reduced. On the other hand, if it is larger than the above range, the excitation lamp becomes a shadow for the light reflected from the reflecting surface, and the amount of light reaching the laser rod decreases. On the other hand, the farther the reflecting surface is from the laser rod, the smaller the amount of light reaching the laser rod. Therefore, the smaller the inner diameter of the reflecting surface is, the better, but the minimum space for housing the laser rod, the excitation lamp and the like is required. Therefore,
As described above, the ratio of the outer diameter of the laser rod, the inner diameter of the excitation lamp, and the inner diameter of the reflecting surface of the reflecting cylinder is 1: (0.
5 to 1.5): (3.0 to 6.0) is most preferable.

[0022]

Embodiments of the present invention will be described below with reference to the drawings of FIGS. FIG. 1 is a cross-sectional view of a solid-state laser device, which has a reflecting cylinder 1. Reflector 1
Is formed by Mitsui Mining Co., Ltd. under the trade name "Maselite" (diffusive reflector). This macerite is obtained by precipitating fluorophlogopite crystals in a glassy matrix by a sol-gel method using a metal alkoxide as a starting material.

This reflecting cylinder 1 is composed of blocks 1a, 1b, 1
c, 1d are stacked to form a prismatic shape,
A circular cross section (inner diameter 58 m)
The chamber 2 of m) is formed. The inner surface of the reflecting cylinder 1, that is, the surface of the chamber 2 serves as the reflecting surface 3.

Inside the reflecting cylinder 1, one YAG laser rod 4 and four excitation lamps 5 are arranged. still,
FIG. 2 is a perspective view in which one of the blocks 1b and 1d of the reflection cylinder 1 is removed and the two excitation lamps 5 housed on the side of the blocks 1b and 1d are omitted.

The laser rod 4 has an outer diameter of 12.7 m.
It has a cylindrical shape of m and a length of 195 mm, and is arranged with its central axis aligned with the central axis of the reflecting cylinder 1. Both ends of the laser rod 4 are extensible and held by rod holders 8 described later.

The four excitation lamps 5 arranged around the laser rod 4 have an inner diameter of 10 mm and a length of 200 m.
It has a cylindrical shape of m. The excitation lamps 5 are arranged around the laser rod 4 at equal intervals in the circumferential direction (that is, at intervals of 90 °) and are in a posture parallel to the laser rod 4. The central axis of each excitation lamp 5 is arranged on the same pitch circle with a diameter of 39 mm centered on the central axis of the reflecting cylinder 1.

As described above, in this embodiment, the ratio of the outer diameter of the laser rod 4, the inner diameter of the excitation lamp 5 and the inner diameter of the reflecting surface 3 of the reflecting cylinder 1 is approximately 1: 0.8: 4.6.
It has become.

In the reflecting cylinder 1, the laser rod 4 is
It is housed in a transparent tube 6 made of glass, and the transparent tube 6 is in the chamber 2 and communicates with the inside of the reflecting cylinder 1. Then, the transparent tube 6 and the reflecting cylinder 1 are filled with a cooling liquid 7 such as water to cool the laser rod 4.

As shown in FIG. 3, one end of the laser rod 4 is held so as to be wrapped by the above-mentioned rod holder 8. An O-ring 10 is fixed to this holding portion, and the laser rod 4 and the transparent tube 6 are held. The liquid-tightness is enhanced so that the cooling water between and does not enter the rod holder 8.

An O-ring 11 is also fitted between the outer peripheral portion of the rod holder 8 on the outer end side and the reflecting cylinder 1 to maintain liquid tightness inside the reflecting cylinder body. The rod holder 8 is
As shown in FIGS. 1 and 3, one side (upper side in the figures) is 1
One ball plunger 16 and the other (downward in the figure) are held by a pair of screws 17 and 17 with free balls, and one set of the ball plunger 16 and the screws 17 and 17 with free balls is 2 as shown in FIG. It is provided in pairs.

As shown in FIG. 4, the ball plunger 16 has a hexagonal wrench hole H in the base thereof, and a metal ball 22 is rotatably accommodated in the tip of a screw main body 21 having a thread strip around it. The metal ball 22 is biased in the protruding direction by a spring 23 housed inside the screw body 21.

As shown in FIG. 5, the screw 17 with a free ball also has a hexagonal wrench hole H at the base, and a metal ball 25 is provided at the tip of the screw main body 24 having a thread strip around it.
Is rotatably housed.

The ball plunger 16 and the screw 17 with a free ball allow the rod holder 8 to move freely in the length direction of the laser rod 4, that is, in the length direction of the laser rod 4. Is held in.

In the solid-state laser device having the above structure, when the four excitation lamps 5 are turned on continuously or in a pulsed manner, a part of the excitation light emitted from each excitation lamp 5 is directly applied to the laser rod 4, After the rest is diffused and reflected by the reflecting surface 3 of the reflecting cylinder 1, the reflected light is reflected by the laser rod 4.
Is irradiated. As a result, the laser rod 4 oscillates a laser and a laser beam is emitted from both ends. here,
Since the indirect light diffusely reflected by the reflecting surface 3 is less absorbed and reflected by other excitation lamps, the oscillation efficiency is improved. As a result, although the power input to the excitation lamp 5 is lower than the power input limit, a large output of excitation light can be input to the laser rod 4, the life of the excitation lamp 5 can be extended, and the solid-state laser device can increase the lifetime. You will be able to get the output.

In this example, the following laser output could be obtained with respect to the input power.

[0036]

[Table 1]

[0037]

As described above, according to the solid-state laser device of the present invention, the reflecting surface of the reflecting cylinder is formed of a diffuse reflector to form a cylindrical shape having a circular cross section, and three or more inside the reflecting cylinder. Since the excitation lamp is provided, the light emitted from the excitation lamp is diffused without being focused on a specific portion, and the ratio of being absorbed / reflected by another excitation lamp is reduced, so that the efficiency is improved. Therefore, the number of laser rods to be used can be reduced, for example, a large output can be obtained even with one laser rod, and a small-sized and large-output solid-state laser device can be manufactured.

Furthermore, even if the power supplied to the excitation lamp is lower than the power supply limit, the laser rod can be irradiated with high-power excitation light, so that the life of the excitation lamp can be extended.
The durability of the solid-state laser device is improved.

[Brief description of drawings]

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

FIG. 2 is an external perspective view showing a state in which one block of the reflection cylinder and two excitation lamps are removed in the solid-state laser device of the present invention.

FIG. 3 is a cross-sectional view of the solid-state laser device of the present invention.

FIG. 4 is a sectional view of a ball plunger used in the solid-state laser device of the present invention.

FIG. 5 is a sectional view of a screw with a free ball used in the solid-state laser device of the present invention.

[Explanation of symbols]

 1 Reflective Cylinder 2 Chamber 3 Reflecting Surface 4 Laser Rod 5 Excitation Lamp 6 Transparent Tube 7 Coolant 8 Rod Holder 10, 11 O-ring 16 Ball Plunger 17 Screw with Free Ball 21 Screw Body 22 Metal Ball 23 Spring 24 Screw Body 25 Metal Ball H hexagon wrench hole

Claims (4)

[Claims] 1. A reflecting cylinder having a reflecting surface on the inside, a laser rod as a laser medium provided inside the reflecting cylinder, and an excitation source for providing excitation light to the laser rod provided inside the reflecting cylinder. In the solid-state laser device including an excitation lamp, the reflecting cylinder has a reflecting surface formed of a diffuse reflector and has a cylindrical shape with a circular cross section, and at least three or more exciting lamps are arranged. Solid-state laser device. 2. The solid-state laser device according to claim 1, wherein the laser rod is held in a free state so that at least one end of the laser rod can expand and contract in the axial direction. 3. The ratio of the outer diameter of the laser rod, the inner diameter of the excitation lamp, and the inner diameter of the reflection surface is 1: (0.
5 to 1.5): (3.0 to 6.0). The solid-state laser device according to claim 1 or 2, wherein 4. The solid-state laser device according to claim 1, wherein the diffuse reflector is made of mica ceramics.