JP2003283015A - Lamp excited laser oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser oscillator in which the life of an excitation lamp is elongated and stabilized. <P>SOLUTION: Excited light from the excitation lamp 2 is collected and reflected by the inner surface of an excitation cavity 3 to excite a laser medium 1. The stimulated emission light is amplified with reiterated reflection between resonator mirrors 8, 9, and outputted from the output mirror 8. The length of the lamp 2 is larger than that of an excitation area of the laser medium 1, and in correspondence with which both of electrodes 4, 5 and a peripheral part 6 are disposed outside the cavity 3, being shielded by a housing 7. The length of the shield range, for instance, is approximately 30 mm. The peripheral part 6 is deteriorated by the sputtering attachment or discoloring of a silica tube as time passes with the lamp 2 being lit. However, since the peripheral part 6 is disposed outside the cavity 3 and shielded by the housing 7, no light permeates through the peripheral part 6 for contribution to laser oscillation. As a result, stable laser output is maintained for a long period of time. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lamp-pumped laser oscillator used in, for example, laser processing, medical treatment, illumination, communication, etc. More specifically, the pumped-laser oscillator has a long lamp life. , For high reliability technology.

[0002]

2. Description of the Related Art In recent years, a lamp-excited laser oscillator using a crystal such as Nd: YAG as a laser medium has been used in a laser processing apparatus for cutting or welding a metal or a non-metal material. In a general lamp excitation laser oscillator, the laser medium is excited by irradiating the discharge light of an excitation lamp such as a krypton arc lamp from the side of the laser medium. Since both ends of this laser medium are mechanically held, the excitation length of the laser medium (the length of the portion excited by the excitation light) is the length of the portion located inside the excitation cavity or housing. Is shorter than the total length of the laser medium. The discharge length of the excitation lamp (the length of the portion where discharge occurs between the electrodes) is generally designed to be substantially equal to the excitation length of the laser medium.

On the other hand, the oscillation output of the lamp excitation type laser oscillator depends on the emission intensity of the excitation lamp, and when the emission intensity decreases with the operating time, the oscillation output also gradually decreases. For this reason, it is customary to replace the oscillation output with a new excitation lamp when the oscillation output has decreased to a certain limit, for example, about 20% of the emission intensity at the start of lamp operation.

Such a replacement cycle of the excitation lamp is generally called a lamp life, and if the lamp life is short, naturally,
The frequency of replacement increases, causing problems such as maintenance time and running costs. Also, when there are multiple lamps in the same cavity, the radiated light from each other accelerates the deterioration of the lamps, causing damage.
There were also problems such as shortened life.

By the way, in the lamp excitation type laser oscillator, the emission intensity of the lamp is lowered as described above,
The factors that necessitate exchanging the excitation lamp are (1) discoloration due to ultraviolet absorption of the quartz tube used as the tube of the excitation lamp, (2) violent collision of ionized atoms and electrons with the electrodes. Examples include deterioration of the electrode material itself, and (3) deterioration of the electrode material scattered from the electrode due to adhesion (sputtering) of the electrode material to the inner wall of the quartz tube, in particular, discoloration in the vicinity of the electrode.

Among these factors, the one that has the greatest effect on the reduction of the emission intensity is the above-mentioned (3) that the material adhered to the inner wall of the quartz tube due to the sputtering of the electrode material and the discoloration of the quartz tube. FIG. 5 is a diagram for explaining this. In the figure, reference numeral 1 is a laser medium (for example, a solid crystal such as YAG or glass or a liquid dye), and an excitation cavity 3 covered with a condensing reflection surface between resonator mirrors (output mirror and rear mirror; not shown). It is arranged inside and is excited (optically pumped) by excitation light emitted from an excitation lamp (for example, a rare gas discharge tube such as krypton or xenon).

A negative electrode 4 and a positive electrode 5 are provided at both ends of the lamp 2.
There is a discharge between the two electrodes, and the lamp 2 emits light,
Excitation light is generated and condensed on the laser medium 1 by the condensing and reflecting action of the inner surface of the excitation cavity 3. The stimulated emission light of the laser medium 1 excited by this is repeatedly reflected between the resonator mirrors facing each other, amplified, and output from the output mirror as laser output light. The problem here is that in the conventional structure as shown in FIG. 5, the light condensed on the laser medium 1 contains a considerable amount of light passing through the wall of the discharge tube in the vicinity of the electrodes 4 and 5. , Electrodes 4, 5
It means that there is also light that directly goes to the laser medium 1 from the wall of the discharge tube in the vicinity of.

As described above, the atoms and electrons ionized by the discharge violently collide with the electrodes 4 and 5, and the electrode material scattered from the electrodes 4 and 5 adheres to the inner wall of the quartz tube in a layered manner, resulting in fog. Cause discoloration. The region where such a phenomenon related to the deposition of sputtering spreads with the lighting time of the lamp, and the closer to the negative electrode 4 and the positive electrode 5, the larger the deposition amount and the more severe the discoloration. Therefore, the closer to the electrodes 4 and 5, the light amount of the light passing through the wall of the discharge tube sharply decreases, which appears as a laser output decrease.

Further, the portion 6 discolored by the adhered matter is
Since the excitation light of the other lamps 2 arranged in the same excitation cavity 3 and the excitation light of its own are absorbed to generate heat, the strength of the quartz tube is lowered, and cracks may be caused.

Conventionally, as a method for alleviating the problem of the decrease in the emission intensity of the excitation lamp and extending the life of the excitation lamp,
It was adopted by changing the electrode shape, changing the electrode material, and improving the design of the excitation lamp itself. However, such measures require a great deal of time and money. further,
Phenomena such as spatter and discoloration near the electrodes of the excitation lamp are
Since the traveling speed of the laser device varies greatly depending on the usage conditions of the laser device, such as the current value applied to the excitation lamp and the frequency of ON-OFF, even if the laser oscillator has the same configuration, the degree of discoloration and color change of the excitation lamp It was difficult to predict in advance the lighting time of the lamp was not constant. Therefore, it is not easy to design a lamp that suits the individual usage conditions.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and in a lamp-excited laser oscillator, the lamp life can be reliably extended under any structure and use conditions, and the replacement thereof can be performed. An object is to provide a device that can be reduced in frequency.

[0012]

According to the present invention, in a lamp pumping type laser oscillator, the discharge length of the pumping lamp is set sufficiently longer than the pumping length of the laser medium, and the region near the electrode of the pumping lamp is pumped by the laser medium. By adopting the idea of making a structure that does not contribute to the above, the reduction of the laser output due to the deterioration of the periphery of the electrode of the excitation lamp is reduced, the laser output is stabilized for a long time, and the frequency of lamp replacement is reduced.

Specifically, according to the present invention, the laser medium and the excitation lamp are an excitation cavity for reflecting and collecting the excitation light, or a housing for mechanically supporting the laser medium and the excitation lamp. In a lamp excitation laser oscillator having an enclosed structure, a length of a portion of the laser medium contained inside the excitation cavity or the housing in the longitudinal direction is shorter than a distance between positive and negative electrodes of the excitation lamp. In addition, the excitation lamp and the excitation cavity or the housing are arranged so that the excitation light around the electrodes of the excitation lamp is not shielded by the component or the housing constituting the excitation cavity and is not irradiated on the laser medium. It

Here, within the distance between the electrodes of the excitation lamp, the range for shielding light is set so as to cover the range where spatter adhesion and discoloration around both electrodes have a strong influence on the excitation light intensity. Practically, it should be set so as to shield at least 20 mm from the tips of both electrodes toward the center, and preferably the range not less than 30 mm is shielded.

Further, considering that spatter adhesion or discoloration particularly strongly occurs around the negative electrode, the light may be shielded only in the negative electrode peripheral portion. That is, in another aspect of the present invention, a structure in which a laser medium and an excitation lamp are surrounded by an excitation cavity that reflects and collects excitation light, or a housing that mechanically supports the laser medium and the excitation lamp. In the lamp-pumped laser oscillator, the length of the laser medium in the longitudinal direction of a portion contained inside the pumping cavity or the housing is configured to be shorter than the distance between the positive and negative electrodes of the pumping lamp, The excitation lamp and the excitation cavity or the housing are arranged so that only the excitation light around the negative electrode of the excitation lamp is shielded by the component or the housing forming the excitation cavity and is not irradiated on the laser medium.

In this case, within the distance between the electrodes of the excitation lamp, the range for shielding light is set so as to cover the range where spatter adhesion or discoloration strongly affects the excitation light intensity in the vicinity of the negative electrode. Practically, it should be set so that at least a range of 20 mm from the tip of the negative electrode (tip on the center side) toward the center is shielded from light, preferably 3
The area that does not fall below 0 mm is shaded.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 4 and 6. Elements common to those of the conventional example shown in FIG. 5 are designated and provided with common reference numerals, and illustrated and described.

First, FIG. 1 shows the structure of the essential parts of a first embodiment of a lamp excitation type laser oscillator according to the present invention.
In the figure, 1 is a laser medium (for example, a solid crystal or liquid dye such as YAG or glass), 2 is an excitation lamp (for example, a rare gas discharge tube such as krypton or xenon), and 3 is a condensing reflecting surface. Excited cavity covered. Reference numeral 7 is a housing for holding the lamp 2 or the excitation cavity 3, 8 and 9 are paired resonator mirrors, 8 is an output mirror, and 9 is a rear mirror.

When a discharge current flows through the excitation lamp 2, the excitation lamp emits light, and the excitation light is condensed on the laser medium 1 by the condensing and reflecting action of the inner surface of the excitation cavity 3. As a result, the laser medium 1 is excited, the stimulated emission light is repeatedly reflected between the opposing resonator mirrors 8 and 9, is amplified, and is output from the output mirror 8 as laser output light. This operating principle is the same as the conventional one.

The most important difference between the structure shown in FIG. 1 and the conventional structure (FIG. 5) is that the length of the pump lamp 2 is the pump length of the laser medium 1, that is, the length of the laser siliceous material. Direction, which is sufficiently longer than the length of the inner part (excitation area) of the excitation cavity 3, and accordingly the electrodes 4, 5 and their periphery 6 are arranged outside the excitation cavity 3,
Besides, it is covered with the housing 7 and shielded from light. In this embodiment, the length of the range in which the light is shielded is about 30 mm. Generally, at least two electrodes are formed from the tips (tips on the center side) of both electrodes 4, 5 toward the center.
0 mm is necessary and preferably not less than 30 mm.

As mentioned above, this portion 6 of the excitation lamp 2 deteriorates due to spatter adhesion and discoloration of the quartz tube as the lamp 2 is turned on. However, in the structure shown in FIG. 1, since it is disposed outside the excitation cavity 3 and is shielded from light by the housing 7, it passes through this electrode vicinity portion (portion where spatter adhesion or discoloration is noticeable) 6 and causes laser oscillation. There is virtually no contributing light. Therefore, what actually affects the laser output is only the light emitted from the region that gives an effective light emission length, that is, the region that is not shielded between the portions 6 on both ends. Since this effective light emitting portion is separated from both electrodes 4 and 5, the deterioration progresses relatively slowly. As a result, a stable laser output is maintained for a long period of time.

Further, as can be understood from the comparison with the conventional structure shown in FIG. 1, the electrode peripheral portion 6 of the excitation lamp 2 is not irradiated with the excitation light of other lamps in the same cavity 3. The deterioration itself of the part 6 is also reduced.

FIG. 6 is a graph showing the time change of the output of the laser oscillator according to the present embodiment in comparison with the conventional example. In FIG. 6, the output change characteristic indicated by reference numeral 10 is
It is the result of actual measurement of the output change characteristic of the conventional lamp excitation type laser oscillator, and reference numeral 11 is the time change of the laser output actually measured by the lamp excitation type laser oscillator having the structure of this embodiment.

From a comparison of these two change characteristics 10 and 11, it is understood that the structure of the present embodiment realizes a gentle output reduction as compared with the change characteristics 10 obtained by the conventional structure. This means that the frequency of exchanging the excitation lamp 2 can be reduced as compared with the conventional one, and this is nothing but the fact that the excitation lamp 2 has a substantially long life.

Next, FIG. 2 is a diagram for explaining a second embodiment of the present invention. As shown in the figure, in the present embodiment, only the vicinity of the negative electrode 4 of the excitation lamp 2 is arranged outside the excitation cavity 3, and the housing 7 or the like shields the light. Otherwise, it has a structure similar to that shown in FIG.

That is, 1 is a laser medium (for example, a solid crystal or liquid dye such as YAG or glass), 2 is an excitation lamp (for example, a rare gas discharge tube such as krypton or xenon), and 3 is a condensing reflecting surface. Excitation cavity covered with. The housing 7 holds the lamp 2 or the excitation cavity 3. The illustration of the resonator mirror is omitted.

Also in the present embodiment, when a discharge current flows through the excitation lamp 2, the excitation lamp emits light, and the excitation light is condensed and reflected by the inner surface of the excitation cavity 3,
It is focused on the laser medium 1. As a result, the laser medium 1 is excited, the stimulated emission light is repeatedly reflected between the opposing resonator mirrors (not shown), is amplified, and is output as laser output light from the output mirror.

In the present embodiment, the reason why the light from the lamp 2 is shielded especially in the peripheral region on the negative electrode side is generally the lamp 2
Deterioration due to spatter adhesion or discoloration of the quartz tube is due to the fact that the negative electrode side progresses faster than the positive electrode side and the degree thereof is large. That is, even in the structure in which only the negative electrode side is shielded from the light, the decrease in the laser output due to the lamp deterioration is slower than that in the conventional structure, and the effect of extending the lamp life can be expected sufficiently.

Here, within the distance between the electrodes of the excitation lamp, the range for shielding light is set so as to cover the range where spatter adhesion or discoloration around the negative electrode 4 has a strong effect on the excitation light intensity. . Practically, it should be set so as to be shielded from the tip (center side) of the negative electrode 4 toward the center by at least 20 mm, preferably 30 mm.
The range not less than mm is shaded. In Figure 3, 30m
An example is shown in which the range of m is shielded from light.

FIG. 4 shows an example of a structure in which a part of the structure of the second embodiment shown in FIG. 2 is modified so that the plurality of excitation lamps 2 are arranged so as to face each other. As described above, this structure takes into consideration that the progress speed of deterioration (spatter adhesion, discoloration, etc.) of the lamp 2 is considerably different between the negative electrode 4 and the positive electrode 5. That is, if the directions of the plurality of lamps 2 are aligned, the lamp deterioration may be biased to one side of the oscillator (the side of the negative electrode 4) and the uniform laser oscillation may be impaired. However, in the structure shown in FIG. According to this, such an imbalance of deterioration progress can be avoided.

Except for the direction of the lamp 2, the structure,
Since the essential points of the operation are not particularly different from those of the second embodiment,
The repeated description is omitted. In addition, within the distance between the electrodes 4 and 5 of the excitation lamp 2, the range in which light is shielded should cover the range in which spatter adhesion or discoloration around the negative electrode 4 strongly affects the excitation light intensity for each lamp 2. Is set. In practice, at least 20 mm from the tip (center side) of the negative electrode 4 toward the center should be set so as to be shielded from light, and preferably the range not less than 30 mm is shielded from light.

[0032]

According to the present invention, even if the sputter / color-change region spreads in the vicinity of the electrode of the excitation lamp, the region is shielded by the excitation cavity or the lamp housing and does not substantially participate in laser oscillation. However, the decrease in the laser oscillation output becomes gentle even after long-term operation. As a result, a long service life of the excitation lamp is achieved. In addition, it is possible to prevent the sputter / color change area near the electrodes of the excitation lamp from being irradiated by the radiated light of other lamps arranged in the same excitation cabinet, so deterioration due to mutual irradiation between the lamps is prevented. It also has an effect
This also contributes to extending the life of the excitation lamp. Further, as long as the present invention is applied, a stable lamp life that is not so much influenced by any structure and use condition is secured.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a second embodiment of the present invention.

FIG. 3 is a diagram for explaining a light blocking range in the structure shown in FIG.

FIG. 4 is a diagram for explaining a modified example of the second embodiment of the present invention.

FIG. 5 is a diagram for explaining a problem in a conventional laser oscillator.

FIG. 6 is a graph showing the time change of the laser oscillation output measured in the embodiment of the present invention in comparison with the conventional gas equation.

[Explanation of symbols]

1 Laser Oscillation Medium 2 Excitation Lamp 3 Excitation Cavity 4 Excitation Lamp Negative Electrode (Cathode) 5 Excitation Lamp Positive Electrode (Anode) 6 Sputter Adhesion Area around Lamp Electrode 7 Housing 8 Resonator Mirror (Output Mirror) 9 Resonator Mirror (Rear Mirror) ) 10 Time-varying characteristic of laser output measured by conventional laser oscillator configuration 11 Time-varying characteristic of laser output actually measured by the embodiment of the present invention

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Yoshida             Yamanashi Prefecture Minamitsuru-gun Oshino-mura Shinobaku-ji Kobaba 3580             Local FANUC Co., Ltd. (72) Inventor Haruhiko Yamamoto             Yamanashi Prefecture Minamitsuru-gun Oshino-mura Shinobaku-ji Kobaba 3580             Local FANUC Co., Ltd. F term (reference) 5F072 AB02 AK01 JJ03 PP01 RR01

Claims (4)

[Claims] 1. A lamp pump laser oscillator having a structure in which a laser medium and a pump lamp are surrounded by a pump cavity for reflecting and focusing pump light, or a housing for mechanically supporting the laser medium and the pump lamp. In the laser medium, the length of the portion of the laser medium included inside the excitation cavity or the housing in the longitudinal direction is configured to be shorter than the distance between the positive and negative electrodes of the excitation lamp, and both electrodes of the excitation lamp. The pumping lamp and the pumping cavity or the housing are arranged so that the pumping light of the peripheral portion is shielded by the component or the housing constituting the pumping cavity and is not irradiated to the laser medium. Type laser oscillator. 2. Within the distance between the electrodes of the excitation lamp, a range of 30 mm or less from the tips of both electrodes toward the center,
The lamp-pumped laser oscillator according to claim 1, wherein light is shielded by a component or a housing constituting the pump cavity. 3. A laser pumping laser oscillator having a structure in which a laser medium and a pumping lamp are surrounded by a pumping cavity for reflecting and focusing pumping light, or a housing for mechanically supporting the laser medium and the pumping lamp. In the laser medium, the length in the longitudinal direction of the portion of the laser medium included inside the excitation cavity or the housing is configured to be shorter than the distance between the positive and negative electrodes of the excitation lamp, and the negative electrode of the excitation lamp. The excitation lamp and the excitation cavity or the housing are arranged so that only the excitation light in the peripheral portion is shielded by the component or the housing constituting the excitation cavity and is not irradiated on the laser medium. Excitation laser oscillator. 4. The part of the distance between the electrodes of the excitation lamp, which is 30 mm or less from the tip of the negative electrode toward the center, is shielded by a component or a housing constituting the excitation cavity. Lamp-pumped laser generator.