JP2003020288A - Laser crystal and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laser crystal obtained by jointing at least one crystal being a polycrystalline body with other crystals. SOLUTION: A single crystal Nd: YAG for a laser rod and a polycrystalline Nd: YAG are jointed by bringing formed body of the polycrystalline Nd: YAG obtained by slip casting into contact with an end face or a side face of the single crystal Nd: YAG, then dewaxing and sintering. When the formed body is jointed with the single crystal, a free face of the formed body which has not touched a slip discharging face or a mold is brought into contact with the single crystal and sintered. Accordingly, there is no need to polish the surface to be jointed in such a manner that optical contact is obtained, and the jointing is easily performed. Further, the face to be jointed is not limited to a flat surface and it is also possible to joint the formed body obtained by slip casting to a side face, or the like, of the single crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser crystal in which a plurality of crystals are joined and a method for manufacturing the same.

[0002]

2. Description of the Related Art The heat generated by the excitation of a solid-state laser causes mechanical distortion of the laser crystal and destroys the crystal, and before that, the beam quality is deteriorated and the output is lowered due to the thermal birefringence effect and the thermal lens effect. Therefore, the laser output is limited. In order to solve this, by joining a crystal without an activator to the laser crystal, such as Nd: YAG single crystal and YAG single crystal, Cr: alumina single crystal (ruby) and alumina single crystal (sapphire). The heat dissipation is promoted and the laser crystal is made uniform.

For joining crystals, there are proposals such as a method of using an optical adhesive and a method of using glass as an adhesive. However, the adhesive and glass originally have poor thermal conductivity, and a sufficient effect can be expected. No, US Pat. No. 5,441,80
The diffusion bonding in 3 is often used.

Further, the laser crystal is required to have a very high quality, and it is difficult to produce a large single crystal for laser. As a countermeasure against this, it is also possible to bond a plurality of small crystals into a large crystal, and in this case as well, diffusion bonding is effective (Japanese Patent Laid-Open No. 4-259269).

On the other hand, with recent advances in powder technology and ceramics technology, optically applicable polycrystalline ceramics (hereinafter referred to as polycrystalline bodies) have become relatively easy to produce. Furthermore, as a laser crystal that is said to be required to have the ultimate quality, the use of polycrystals has become possible, as reported in, for example, OPTRONICS, p168-173 (2001) No.4 of Optronics. There is.

The polycrystalline body may be obtained by forming a raw material powder into a desired shape and sintering it. Therefore, in order to obtain a polycrystalline body in which a plurality of crystals are joined, it is considered that a plurality of desired crystal raw materials are sequentially filled, a multilayer ceramics compact is produced, and then sintered. However, in this method, the raw materials are likely to be mixed in at the joint interface of the crystals, and the dimensional accuracy of each crystal is greatly concerned due to the sintering shrinkage of the ceramics. Therefore, under the present circumstances, the above-mentioned diffusion bonding can only be used to manufacture a laser crystal formed by bonding a plurality of crystals.

[0007]

In diffusion bonding, optically polished crystals are brought into optical contact with each other, and then heated to a temperature at which rearrangement of crystal lattice occurs and bonded. In optical contact, it is necessary to accurately contact two crystals so that bright points and scattering points in the laser wavelength range do not occur on the contact surface, and polishing that enables optical contact becomes very expensive, which is a major factor in the industry. Makes application difficult. Moreover, since the optical contact is required, the shape of the joint surface is limited to a flat surface. Therefore, there is a demand for an inexpensive joining method and a joined body which are not bound by the shape.

[0008]

As a result of various studies to solve the above problems, the present inventors have found that after combining a single crystal or polycrystal with a free surface of a polycrystal cast molding, or The present invention has been completed by finding that it is possible to produce an optically problem-free joined body by combining the free surfaces of the cast molded article of 1 and then sintering.
That is, the present invention provides: (1) a laser crystal formed by joining a plurality of crystals, wherein at least one crystal is a polycrystal, and this is joined to another crystal, and (2) ) The free surface at the time of molding of the cast compact is used as a joint surface, and the joint surface is brought into contact with the surface of another crystal to sinter, thereby sintering the compact to obtain a polycrystalline body and at the same time a polycrystalline body. Is a method for manufacturing a laser crystal, in which the bonding surface of is bonded to another crystal. Preferably, a cylindrical polycrystalline body is bonded to the side surface of the laser rod, and more preferably, a plate-shaped polycrystalline body is bonded to both end surfaces of the laser rod. Preferably, the cast molding is a sludge cast molding, and the free surface is a surface that does not come into contact with the mold during the cast molding. Particularly preferably, the inner peripheral surface of the cylindrical cast molded body is a free surface, the laser rod is inserted into the inner peripheral surface of the cast molded body, the cast molded body is sintered together with the laser rod, and The peripheral surface is joined to the side surface of the laser rod. In this specification, the free surface at the time of cast molding refers to a surface that does not come into contact with a mold or the like when cast molding is performed, and for example, a mud discharge surface is a free surface.

The laser crystal is, for example, a laser rod of a solid-state laser, and preferably the content of the activator is smaller on the end face or side face (circumferential surface) of the single crystal rod containing the activator (oscillation impurities). Alternatively, a polycrystalline body containing substantially no activator is bonded. The activator is, for example, neodymium in the case of YAG or Y2O3 or chromium in the case of alumina. In the conventional example, it is impossible to bond the polycrystalline body to the side surface of the single crystal rod without generating a scattering point or the like on the bonding surface, but since the bonding surface is not limited to a flat surface in the present invention, the single crystal rod It is also possible to bond a polycrystalline body to the side surface of the. Further, since the joining surface does not need to be polished enough to obtain an optical contact, the joining becomes easy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A laser crystal obtained by joining a plurality of crystals of the embodiment is produced by using a free surface of a cast body as a joining surface. There are two combinations of crystals to be joined: (1) a single crystal body or a free surface of a polycrystalline body and a polycrystalline cast body, or (2) free surfaces of a polycrystalline cast body.

First, a method for producing a bonded crystal by combining the single crystal or polycrystal of (1) and a free surface of a cast body will be described. In the joining of the free surfaces of the cast-molded body of (2), the lap surface of the single crystal or the polycrystalline body may be replaced with the free surface of the cast-molded body.

The joint surface of the single crystal or the polycrystal is Rma.
Lapping is preferably performed until x is 5 μm or less, more preferably 2 μm or less, and most preferably 0.5 μm or less. If it is larger than this, the pores formed between the crystal and the ceramic cannot be removed even if the sintering power of the ceramic is used, and it is left behind as a pore in the joint surface, causing the light scattering. Becomes

The ceramic material to be bonded to the crystal is basically preferably the same material as the crystal. Bonding is completed by sintering, but stress acts on the bonding interface due to the difference in coefficient of thermal expansion during cooling, resulting in strain in the entire crystal after bonding,
Disturbance will occur in the transmitted wavefront. However, there is no problem when the coefficient of thermal expansion is very similar to Yttria and YAG. This type of limitation is equivalent to that of diffusion bonding. And, preferably, the laser rod is a single crystal rod having a high impurity content, and a polycrystalline and low or zero impurity content ceramics is bonded to the end face or the side face thereof.

The molded body used for joining is produced by cast molding. There are solid casting method and sludge sludge casting method for cast molding, but since a free surface is required, the sludge casting method is adopted. The slurry used for the cast molding may be water-based or non-water-based, but in the case of the water-based slurry, it is preferable not to use a gypsum mold as a solvent-absorbing mold used in ordinary cast molding. Gypsum dissolves in the water used as the medium,
Gypsum is mixed in the molded body, and it becomes impossible to obtain a polycrystalline body having excellent optical characteristics. When gypsum is used as a mold, alcohol-based slurry is recommended, and when water-based slurry is used, a solvent-absorbent mold is recommended such as a resin mold or porous ceramics found in the unglazed state of ceramics.

As an example of an actual joining operation, a method of joining a polycrystalline body to a side surface or an end face of a single crystal columnar crystal which is a shape often used as a laser rod will be described.

When joining a polycrystalline body to the side surface, a pipe is produced as a ceramic molded body. First, a hole having a required size is made by penetrating a solvent-absorbent mold, and the lower part is closed. The ceramic slurry to be produced is poured into this hole, and left to stand for a while to be inlaid. When the desired thickness is reached, the lower part is opened and the remaining sludge is drained. As a result, the inner surface of the pipe becomes a mud discharge surface.

By leaving it in the dryer for a while,
The molding shrinks from the mold due to drying shrinkage, and the molding can be taken out. The crystals thus obtained are directly inserted into the molded body for degreasing and further sintering, or because the molded body is easily scratched, degreasing is performed only with the molded body and the crystals are inserted after the strength is given. And sinter. A laser-quality bonded crystal is obtained by combining the crystal and the ceramic molded body and then performing ordinary sintering for obtaining a translucent ceramic.

The relationship between the outer diameter and the inner diameter of the crystal and the ceramic pipe molded body (cast molded body) is determined by the shrinkage amount of the ceramic molded body due to sintering. After sintering, the inner diameter of the ceramic pipe may be smaller than the outer diameter of the crystal. If it becomes too small, the ceramic may be destroyed, but surprisingly, when the ceramic is bonded to a crystal of about 10 mmΦ which is usually used as a laser rod, the outer diameter of the crystal and the ceramic pipe before sintering are molded. Even if the inner diameter of the body is almost the same, no fracture occurs during sintering. Due to this phenomenon, the dimensional accuracy of the outer diameter of the crystal and the dimensional accuracy of the inner diameter of the ceramic molded body have a very high degree of freedom.

Next, a method for joining a polycrystalline body to the end face of the columnar crystal will be described. The ceramic molded body may be prepared as a plate material having a required thickness or more after sintering. The method is not limited as long as it is made by cast molding, but put a ring cut PVC pipe or glass tube etc. as a sludge storage part on the solvent absorbent mold material, pour the sludge into it and mold it. It would be easiest to get a face. In this molding method, it is not necessary to drain the mud when only the required amount of sludge is used. The free surface is the surface that does not come into contact with the mold during casting, and the mud discharge surface is the free surface, and there is no difference between the mud discharge surface and the free surface considering the method.

As described above, the ceramic molded body may be directly degreased and sintered in combination with the crystal body, but it is degreased before joining with the crystal body to give initial strength, and in particular, it rubs against the crystal. It is preferable to heat-treat so as not to scratch the joint.

The free surface of the ceramic molded body and the crystal are combined and sintered to complete the joining. At this time, it is to arrange the crystal and the compact to be joined in the firing furnace in a vertically stacked manner.
It is suitable for preventing displacement of the joint surface during firing.

It is effective to apply a compression load to the joint surface during firing. As the flatness of the bonded surface of the crystal, a surface of about 3 μm can be easily obtained if ordinary lapping is performed. With the flatness of this degree, the space between the crystal and the ceramic is absorbed in a manner that the ceramic follows the crystal due to the deformation of the ceramic during firing, and complete optical bonding is possible. It is almost impossible to handle ordinary laser crystals, but even if there is a large difference in flatness, a maximum of about 50 μm is allowed by applying a load. The allowable load range is from no load to the breaking load of the ceramic compact.

As described above, according to the present invention, a bonded crystal can be manufactured very easily as compared with the diffusion bonding which is widely used as a crystal bonding method at present. The reason for this is not clear, but on the free surface of the cast body, it is considered that there is only a disturbance of a few raw material particles as the surface roughness, and this disturbance is absorbed by the deformation of the ceramics during sintering. .

[0024]

Example 1 An yttrium nitrate aqueous solution and an aluminum nitrate aqueous solution were prepared.
Mix it so that it has a YAG composition, add water, and convert it to YAG conversion of 0.
It was set to 1000 L of 003 mol / L acidic aqueous solution. To this, 14.5 times the molar ratio of metal ion concentration of urea and 1.6
Add twice the amount of concentrated sulfuric acid, and use colloidal silica as a sintering aid in an amount of 400 wt.
After adding so that it might become ppm, it heated at 100 degreeC and was made to react under stirring for 3 hours, and precipitate was produced. After the reaction, the mixture was cooled to 35 ° C., filtered and washed with water 6 times, and dried at 150 ° C. for 12 hours. By calcining this precipitate at 1200 ° C. for 3 hours, YAG powder having an average primary particle diameter of 0.2 μm and a secondary particle diameter of 0.3 μm was obtained by observation with TEM and SEM.

To 1 kg of this powder, 250 pure water was used as a liquid medium.
g, 0.5% by weight of A-6114 (Toagosei Kagaku Kabushiki Kaisha, polycarboxylic acid type, A-6114 is a trade name of Toa Gosei Kagaku) as a dispersant, and WF- as a binder.
804 (manufactured by Chukyo Yushi Co., Ltd., polyvinyl alcohol, WF
-804 was added by 0.5 wt% of Chukyo Yushi-Seiyaku Co., Ltd., and was ball-milled and mixed all day and night to obtain a casting slurry. The sludge was poured onto a porous alumina plate in a unglazed state on which a vinyl chloride ring was placed as a sludge storage part, left for 1 day, then dried in a dryer at 60 ° C for 1 day, and then 1 hour.
It was dried for 1 day in a dryer at 20 ° C. to obtain 7 molded bodies of 105Φ × 5 mmt. In this specification, Φ represents a diameter in mm.

Example 2 From the molded body obtained in Example 1, 10 × 10 × 5 mmt
70 molded articles of 1 were cut out, heated at a rate of 25 ° C./hour, and then heat-treated at 1100 ° C. for 5 hours to degrease. After heat treatment, 25 pieces are 1800 under a vacuum of 10-1 Pa or less.
Sintering was performed at 0 ° C. for 10 hours to obtain a translucent YAG ceramic. After mirror polishing the upper and lower surfaces with a parallelism of 10 seconds, the transmitted wave front was observed with a Fizeau interferometer, but no distortion was observed.

Example 3 On one side of the sintered body produced in Example 2, using free SiC abrasive grains, 5 pieces each having a surface roughness of Rmax 10.1, 4.8, 2.2 and 0.45 μm were prepared. I wrapped each one. Flatness of all samples is about 1
was μm. The lap surface and the free surface of the heat-treated compact produced in Example 2 were combined face-to-face and set in a vacuum furnace for sintering. For the sintered body, the two surfaces facing the joint surface are mirror-polished with parallelism of 8 to 10 seconds,
When the joining state was visually confirmed, all the joining surfaces were joined together. The He-Ne laser was transmitted and the scattering points (voids, pores) existing on the joint surface were observed, and the disturbance of the transmitted wave front was also confirmed. The results are shown in Table 1.

[0028]

[Table 1] Observation result of bonding surface Surface roughness Presence of bright spots on bonding surface Number of samples with turbulence on transmitted wavefront 10.1 μm 5 5 4.8 μm 1 2 2.2 μm None 1 piece 0.45 μm None None

Here, the free surface of the degreased plate-shaped cast body was joined to the sintered cast body, but in actual application, both end faces of a laser rod, for example, a single crystal laser rod, are not fired. It is preferable to bring the free surface of the cast molded body that has been degreased by binding into contact and sinter.

Comparative Example 1 Lap surface of sintered body (Rmax 0.45 μm, flatness 1 μm)
Joining was performed in the same manner as in Example 3 except that the surface of the heat-treated molded body to be combined with was a surface (5 pieces) facing the alumina mold during molding or a machined surface (5 pieces) that was cut and then finished by lathe. Crystals were made. Two surfaces facing the bonding surface of the bonded crystal were mirror-polished, and the bonding state was confirmed with the naked eye. As a result, the entire bonding surface was bonded. Next, when 5 mW of He-Ne laser was transmitted and the laser light scattering points at the bonding surface were observed, a large number of scattering bright points were present in all.

Comparative Example 2 The lapped surfaces of the sinters having the Rmax of 0.45 μm and the flatness of 0.8 μm were combined and heat-treated at 1800 ° C. under vacuum in the same manner as in Example 3. About 20% of the joint surface area
Was not joined.

Example 4 Ten samples each having a length of about 10 mm were cut out from a 8% × 205 mm 0.6% Nd: YAG single crystal laser rod, and the end face was rounded.
It was wrapped to a maximum of 0.45 μm and a flatness of 0.9 μm. Five sets of the lap surface and the free surface of the heat-treated molded body produced in Example 2 were combined facing each other, and 5 sets were prepared and set in a vacuum furnace and sintered. When the crystal body was mirror-polished on two surfaces facing the joint surface with a parallelism of 8 to 10 seconds and the joint state was confirmed with the naked eye, all the joint surfaces were joined on the single crystal side. He of 5mW output on this side
The scattering points (voids, pores) existing on the bonding surface were observed after passing through the -Ne laser, but none were observed.

Comparative Example 3 A single crystal bonded crystal was prepared in the same manner as Comparative Example 2 except that the 8Φ × 10 mm single crystal sample prepared in Example 4 was used instead of the sintered body. About 50% of the joint surface area
Was not joined.

Example 5 1000 g of YAG raw material powder produced in the same manner as in Example 1
And 667 g of ethanol as a liquid medium and E as a dispersant.
-503 (Chukyo Yushi Co., Ltd., polycarboxylic acid type, E-50
3 was added by 0.5% by weight of Chukyo Yushi Co., Ltd. and 1% by weight of PVB-BL1 (manufactured by Sekisui Chemical Co., Ltd., polyvinyl alcohol, PVB is a trademark of Sekisui Chemical Co., Ltd.) as a binder, and crushed by a ball mill for 1 day.・ Mixed to obtain slurry. After pouring a through hole of 11.5Φ × 75mm in advance, pour this slurry into the plaster mold with the bottom closed again,
It was left to stand until the inking thickness became 1 mm. After reaching the target thickness, the remaining sludge was drained by opening the bottom of the plaster mold. By drying the thus obtained molded body, a YAG ceramics molded body having an inner diameter of 9Φ, an outer diameter of 11Φ and a length of 70 mm was obtained.

A Nd: YAG single crystal having a length of 8Φ × 50 mm was inserted into the inside of the molded body while paying sufficient attention not to damage it. After this, 1100 at a rate of 25 ° C./h in air
The temperature was raised to 0 ° C., and this temperature was maintained for 5 hours for sufficient degreasing. After degreasing, under vacuum of 10-1 Pa or less, 18
Translucent YAG Ceramics-N by sintering at 00 ℃ for 10 hours
A rod-shaped bonded crystal of d: YAG single crystal was obtained. After mirror-polishing both end faces, a He-Ne laser with a power of 5 mW was transmitted through this face to observe scattering points (voids, pores) existing on the joint surface, but none were observed.

Comparative Example 4 Granules used for CIP (Cold Isostatic Pressing) molding were obtained from the slurry produced in the same manner as in Example 5 using a spray dryer. A bonded crystal was produced in the same manner as in Example 5 except that a pipe-shaped molded body was produced by CIP molding using the granules. When both end surfaces were mirror-polished and the state of the joint surface was confirmed with the naked eye, white rings were clearly seen along the outer periphery of the single crystal, which could be judged to have pores.

Example 6 Yttrium nitrate, urea, ammonium sulfate and aluminum nitrate were respectively added in concentrations of [Y (NO3) 3] =
0.25 mol / L, [Urea] = 1.5 mol / L, [(NH4) 2
SO4] = 0.25 mol / L, and [Al (NO3) 3] = 6.7
It was dissolved in pure water so that the concentration became × 10 −5 mol / L. Next, 10 L of the mixed solution was put into an autoclave and the temperature was adjusted to 125
The temperature was adjusted to 5 × 10 ⁵ Pa and the temperature was kept for 2 hours to obtain a yttrium carbonate precipitate. Filtration and washing of the obtained precipitate are repeated 5 times, and 24 hours at 110 ° C.
Dried for hours. Next, this dry powder was calcined in an alumina crucible at 1200 ° C. for 3 hours in an air atmosphere to obtain an easily sinterable yttria powder. The obtained yttria raw material powder 20
Chugyo Yushi E-503 and F-2 as deflocculants for 0 g
12 g and 4 g of 19 (amine type) were further added, and 1 g of PVB-BL1 manufactured by Sekisui Chemical Co., Ltd. was further added as a binder and mixed with 50 g of ethanol for 12 hours using a nylon pot and a nylon ball to prepare an alcohol slurry.

This alcohol slurry was poured into a gypsum mold to obtain a 60 mm × 60 mm × 5 mm compact. From this molded body, 20 molded bodies each having a size of 10 × 10 × 5 mm were cut out. Five of them were heated at 25 ° C./hour to sufficiently degrease them at 1100 ° C. for 5 hours, and then 5 at a temperature of 1650 ° C. in a vacuum furnace.
Sintered for hours. At this time, the temperature rising rate was 100 ° C./hr and the degree of vacuum was 10 −1 Pa or less. One end surface of the thus obtained sintered body was wrapped with Rmax 0.45 μm and flatness 0.8 μm. 5 sets of the combination of the lap surface and the free surface of the molded body and 5 sets of the combination of the free surfaces of the molded body were heated again at 25 ° C./hr for 1100
After sufficiently degreasing at 5 ° C. for 5 hours, it was sintered at 1650 ° C. for 5 hours in a vacuum furnace. In this case, the combination of the free surfaces of the molded body was 5 × 1 times that of the yttria sintered body during degreasing.
It was placed so that the load was 0 ³ Pa.

The obtained crystal body faces the joint surface 2
The surfaces were polished to a mirror surface with a parallelism of 8 to 10 seconds, and the bonding state was confirmed with the naked eye. As a result, all the bonding surfaces were bonded. The He-Ne laser was transmitted and the scattering points (voids, pores) existing on the joint surface were observed, and the disturbance of the transmitted wave front was also confirmed, but it was an optical crystal with no problem.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hitoshi Kubo             4-7 Koraibashi, Chuo-ku, Osaka Kamijima             Chemical Industry Co., Ltd. (72) Inventor Tomoki Kubo             4-7 Koraibashi, Chuo-ku, Osaka Kamijima             Chemical Industry Co., Ltd. F-term (reference) 4G026 BA02 BB02 BC01 BD11 BE01                       BE02 BG02 BG05 BH06                 4G031 AA08 AA29 BA01 CA01 CA07                       GA06 GA16                 5F072 AB02 AK01

Claims (6)

[Claims] 1. A laser crystal formed by bonding a plurality of crystals, wherein at least one crystal is a polycrystal, and this is bonded to another crystal. 2. The laser crystal according to claim 1, wherein a cylindrical polycrystalline body is bonded to the side surface of the laser rod. 3. The laser crystal according to claim 1, wherein a plate-shaped polycrystalline body is bonded to both end faces of the laser rod. 4. A molded body is sintered into a polycrystalline body by making a free surface at the time of molding of a cast molded body a joint surface and bringing the joint surface into contact with the surface of another crystal to sinter. At the same time, a method for producing a laser crystal, in which the bonding surface of the polycrystalline body is bonded to another crystal. 5. The method for producing a laser crystal according to claim 4, wherein the cast molding is a sludge sludge cast molding, and the free surface is a surface which does not come into contact with the mold during the cast molding. 6. A cylindrical cast-molded body having an inner peripheral surface as a free surface, a laser rod inserted into the inner peripheral surface of the cast-molded body, and the cast-molded body sintered together with the laser rod. The method for producing a laser crystal according to claim 5, wherein the inner peripheral surface is joined to the side surface of the laser rod.