JP3928742B2 - Silica glass for laser - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an optical silica glass, and more particularly to an optical silica glass having characteristics such as optical characteristics and nonlinear optical characteristics.
[0002]
[Prior art]
Conventionally, many glasses and ceramics doped with functional elements and imparted with characteristics such as optical characteristics, nonlinear optical characteristics, electric or magnetic characteristics have been developed and put into practical use. In particular, since laser glasses obtained by doping rare earth elements into glass can provide large oscillators, various types of laser glasses have been proposed that are suitable for high-power lasers compared to single crystals. As the laser glass, a laser glass in which a phosphate glass substrate is doped with a rare earth element is generally used. Since a phosphate glass has a small thermal shock constant of 0.43 W / cm, for example, a fusion driver. When the laser is manufactured to a high average output laser such as the above, there is a defect that the glass of the base material is broken by the energy accumulated at the time of laser oscillation. Therefore, laser glass based on silica glass having a thermal shock constant of 14.5 W / cm, which is two orders of magnitude higher than that of phosphate glass, has attracted attention and research. For example, Galant. There have been proposed laser glass by et al melting method, Nd-doped silica glass by Edward et al sol-gel method, and the like. However, when the laser silica glass was doped with a rare earth element, rare earth elements were associated with each other from a very small amount, and the laser efficiency was poor. In order to solve such problems, a laser glass which co-doped Al ₂ O ₃ and P ₂ O ₃ together with rare earth elements to coordinate Al and P to Nd ³⁺ and prevent association of Nd atoms is disclosed in Japanese Patent Application Laid-Open No. 60-11245. Proposed in the Gazette.
[0003]
[Problems to be solved by the invention]
However, the silica glass described in the above publication is preferably doped with Al ₂ O ₃ or P ₂ O ₃ in an amount equal to or more than 10 times that of Nd, but simply because Nd and Al or P are doped into the silica glass. The coordination state is unstable, and there is Nd that associates with all doped Nd without coordination of Al or P. This associated Nd not only contributes to the laser oscillation, but also has a function of absorbing the laser beam and lowers the laser oscillation efficiency. In particular, when the Nd concentration was 0.5 mol% or more, the laser oscillation efficiency decreased rapidly due to the cluster in which Nd was associated.
[0004]
In view of the current situation, the present inventors have conducted extensive research, and as a result, the rare earth elements were fixed in a stable coordination field in advance and doped into the silica glass in that state, so that the rare earth elements could be supported even at high concentrations. The present invention has been completed by finding that an optical silica glass capable of sufficiently exhibiting the function of a doping element is obtained. That is, [0005]
An object of the present invention is to provide an optical silica glass doped without rare earth elements being associated.
[0007]
Furthermore, an object of the present invention is to provide a large-sized and high-power laser silica glass.
[0008]
[Means for Solving the Problems]
The present invention that achieves the above object is a silica glass obtained by sintering a rare earth element-fixed zeolite and a silica raw material, wherein the rare earth element is doped in an amount of 0.1 to 4 wt% without association. Related to porous silica glass.
[0009]
The rare earth element refers to an element having various functional characteristics, which is a lanthanum series element and actinium series element of Group IIIB of the periodic table. In particular, lanthanum series elements, especially Nd, are preferred. As shown in FIG. 1, the functional silica glass of the present invention has an aluminosiloxane hexagonal column structure (D6R) as shown in FIG. 1, that is, a structure in which 6 out of 12 vertices are Al and the remaining 6 are Si. Is a silica glass obtained by firing zeolite fixed to the SI site at the center of the soot and silica raw material. The SI site in the center of the cage constitutes a stable coordination field, and there are 16 SI sites per unit cell in the case of a fauger site. Originally Na ⁺ occupies the SI site, but 3 to 13, preferably 9 of them are ion-exchanged with rare earth elements, and NH ₄ , Y _b or La is coordinated to the remaining sites, thereby rare earth elements. Can be fixed stably. Examples of the zeolite include faujasite type zeolite and cyclodextrin having similar properties to the faujasite. In particular, faujasite is preferable, and faujasite A {(Na ₂ , K ₂ , Ca, Mg) _29.5 [(AlO ₂ ) ₅₉ (SiO ₂ ) ₁₃₂ ] · 235H ₂ O}, faujasite X {Na ₈₆ [(AlO ₂ ) ₈₆ (SiO ₂ ) ₁₀₆ ] · 246H ₂ O} or faujasite Y {Na ₅₆ [(AlO ₂ ) ₅₆ (SiO ₂ ) ₁₃₆ ] · 250H ₂ O} is used. The functional silica glass of the present invention is doped in the silica glass with the soot structure covering one unit, that is, the periphery of the functional element with another element. Is doped in the range of 0.1 to 4 wt%. When the doping concentration is less than 0.1 wt%, the characteristics of rare earth elements are not exhibited, and when the doping concentration exceeds 4 wt%, the vitreous region is exceeded and silica glass is not formed. Further, when the rare earth element coordinates more than 13 SI sites, the rare earth element is detached and association occurs. The zeolite in which the rare earth element is fixed in a stable coordination field is manufactured by mixing zeolite and a water-soluble compound of the rare earth element in water, heating and exchanging ions, and then treating with an ammonium chloride solution. Examples of the water-soluble compound of the rare earth element include chloride, nitric acid, hydroxide salt, and the like of the rare earth element, and these are used alone or in combination. An element that does not exhibit functionality, such as Yb or La, even if it is a rare earth element is important as an element that controls the number of substitution of the rare earth element because it does not show an association due to separation even when coordinated to the SI site. Moreover, by coordinating this element, the alkali element concentration in the zeolite can be reduced, which is suitable for use in the field where the presence of the alkali element is disliked. As a control of the number of substitution of the rare earth element, it is preferable to treat with an ammonium chloride solution after ion exchange of the rare earth element. The number of substitutions can be arbitrarily changed by appropriately selecting the concentration and treatment time of the ammonium chloride solution. The number of substitutions can also be controlled by using insensitive rare earth elements in combination. The optimum number of substitutions in which the rare earth element performs its function is nine, and in this case, it is preferable to treat with a saturated ammonium chloride solution.
[0010]
After the functional rare earth element is fixed and the zeolite and the silica raw material are uniformly mixed, the functional silica glass of the present invention can be produced by firing at 1700 to 1800 ° C. The silica raw material was produced by a CVD method or a VAD method using silica using an alkali silicate as a silica source, silica using an alkoxysilane as a silica source, or a silane compound such as Si (CH ₃ ) Cl ₃ or SiCl ₄ as a silica source. Examples thereof include silica and natural crystalline quartz. In particular, in the case of a silica raw material using alkoxysilane as a silica source, a homogeneous silica raw material can be obtained by mixing and gelling a silica sol obtained by hydrolyzing alkoxysilane with a zeolite in which a functional rare earth element is fixed. By firing or mixing with other silica raw materials and firing, silica glass doped with rare earth elements uniformly can be obtained.
[0011]
As described above, the optical silica glass of the present invention contains a functional rare earth element at a high concentration and does not associate, so that the function expression efficiency of the rare earth element is high. For example, a laser glass doped with a rare earth element is used. The lifetime is much longer than laser silica glass obtained by other manufacturing methods, and the oscillation efficiency is also high. For example, the Nd-doped silica glass of the present invention has a fluorescence spectrum intensity for 1063 nm excitation light that is 3 to 4 times higher than that of an Nd-doped silica glass produced according to the production method described in JP-A-60-11245, The lifetime is 400 μs or longer, which is much longer than the lifetime of 300 μs of the known phosphoric acid laser glass. As described above, the optical silica glass of the present invention exhibits various functions depending on the kind of the functional rare earth element to be doped. For example, if the doping amount of an element that increases the refractive index such as Cs or Tl is changed in the circumferential direction, light is refracted in the circumferential direction, and a plate-like lens can be manufactured. Doping of rare earth elements other than Nd, including the rare earth elements, into the silica glass may be performed in the same manner as the Nd treatment.
[0012]
[Embodiment]
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to this.
[0013]
【Example】
Example 1
156 g of faujasite X and 477 g of NdCl ₃ were kept for 2 weeks while refluxing at 100 ° C. with good stirring in water. Subsequently, the obtained Nd-substituted faujasite X was taken out, treated with saturated ammonium chloride solution for 4 hours, and Nd ⁺³ was coordinated to 9 SI sites. After drying the faujasite X, the faujasite X is uniformly mixed at a ratio of 4.59 g, 9.61 g, 21.27 g, and 35.71 g with respect to 100 g of silica powder, and sintered at 1750 ° C. A transparent silica glass was prepared. The doped amounts of Nd in the silica glass were 0.5 wt%, 1 wt%, 2.0 wt% and 3.0 wt%, respectively. When the fluorescence spectrum intensity of silica glass having a Nd doping amount of 1 wt% was measured, the relative fluorescence spectrum intensity with respect to the excitation light of 1063 nm was 9.38 [a. u. ]Met. Further, when the lifetime of the Nd-doped silica glass was measured, it was 400 μs or more as shown in FIG.
[0014]
On the other hand, when the relative fluorescence spectrum intensity for the excitation light of 1063 nm was measured in the same manner as described above for silica glass doped with 1.2 wt% Nd by the melting method, 0.668 [a. u. ]Met. Further, when the lifetime and relative fluorescence spectrum intensity of a phosphate glass generally used as a laser glass were measured, 300 μs and 5.81 [a. u. ]Met.
[0015]
As described above, the Nd-doped silica glass of this example has a high relative fluorescence spectrum intensity and a long lifetime, despite the fact that it contains a high concentration of Nd. Presumed. The distance between Nd and Nd in the silica glass is estimated to be 9.3 mm or more, which is estimated from the Zeolato structure and the like, and rare earth elements do not associate.
Example 2
A silica glass doped with 3.0 wt% of Ce was prepared in the same manner as in Example 1 except that Ce was used instead of Nd in Example 1. The fluorescence spectrum intensity of the silica glass was as shown in FIG.
[0016]
【The invention's effect】
The optical silica glass of the present invention is a silica glass that can exhibit its characteristics sufficiently without association of rare earth elements. In particular, a laser silica glass doped with Nd or the like has a high output and a long lifetime laser oscillation, and is useful as a large and high output glass laser.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing that zeolite X has a hexagonal prism structure (D6R).
FIG. 2 is a graph showing the fluorescence spectrum intensity of the Nd-doped silica glass of the present invention.
FIG. 3 is a graph showing the lifetime of the Nd-doped silica glass of the present invention.
FIG. 4 is a graph showing the fluorescence spectrum intensity of the Ce-doped silica glass of the present invention.

Claims (5)

An optical silica glass obtained by sintering a zeolite in which a rare earth element is fixed at an SI site and a silica raw material, wherein the rare earth element is doped in an amount of 0.1 to 4 wt% without association. Silica glass for laser . 2. The silica glass for laser according to claim 1, wherein the rare earth element is zeolite fixed to 3 to 13 SI sites. Laser silica glass according to claim 1 or 2, wherein the silica glass for optical is a laser glass. The silica glass for laser according to claim 3, wherein the fluorescence lifetime of the laser glass is 400 µsec or more. 2. The silica glass for laser according to claim 1, wherein the rare earth element is Nd.

Images