JP3132245B2 - Fluoride glass composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass composition for a fluoride glass fiber used for optical communication and the like.

[0002]

2. Description of the Related Art Fluoride glass, which transmits light in the visible region to the mid-infrared region, has attracted attention as a host for optical amplification, up-conversion, and fiber lasers. Above all, research on praseodymium (Pr ³⁺ ) -doped fluoride glass fiber amplifiers for the purpose of amplifying signals in the 1.3 μm band, which is the communication wavelength, has been conducted very energetically.

A very important factor in these applications is that
This is the quantum efficiency of the added active species. Since the quantum efficiency is the ratio of the energy that can be effectively extracted out of the excited energy, the value greatly affects the performance in each application. For example, in a fiber laser, the higher the quantum efficiency, the higher the oscillation intensity. Further, in the case of a fiber used for an optical amplifier, the amplification efficiency increases in proportion to the quantum efficiency. Therefore, it is required to increase the quantum efficiency in order to improve the performance.

At present, for the above-mentioned applications, (a) ZrF ₄ -based fluoride glass (glass abbreviated as ZBLAN, ZBLYAN is typical) mainly due to high stability against crystallization, etc. (b) AlF ₃ -based Fluoride glass is widely used. (For example, Y. Ohishi, et.al.,
Electron. Lett., 27 (1991), p1995-6).

However, these glasses have a very low quantum efficiency. For example, a praseodymium-doped fiber amplifier has a serious disadvantage that the quantum efficiency is only 1 to 3%. The quantum efficiency of these glasses is low because the frequency between atoms is high, that is, the phonon energy is high, so that the non-radiative relaxation probability is high.

As a method for avoiding this drawback, (1) chalcogenide glass (S compound, Se compound or Te compound)
(2) Cd-based halide glass (CdF ₂ -based or CdCl
( ₂ ) (3) Glasses with low phonon energy, such as ThF ₄ -based fluoride glass, are being studied. (For example, DWHewak, et.al., ibid, 29 (1993),
p237-9).

[0007] However, the glass (1) requires a dedicated facility for chalcogenide glass and has a problem that the loss is large because impurities cannot be sufficiently removed. The glass of (2) uses very toxic Cd, and the glass of (3) uses Th which is a radioisotope.

[0008] Recently, a glass mainly containing InF ₃ has been reported. (M. Poulain, et.al., XVI Interna
nation Congress of Glass, Madrid 1992, Proceedings
of Congress 2, p61-66, hereafter referred to as a report example).

[0009] However, the glass obtained in the reported composition range is very easily crystallized, and it has been almost impossible to spin into glass fiber.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a core glass composition for a fluoride glass fiber which has high quantum efficiency and is stable against crystallization.

[0011]

An object of the present invention is to provide a semiconductor device comprising:
In a fluoride glass composition containing F ₃ , BaF ₂ , ZnF ₂ , PbF ₂ , and SrF ₂ as main components, AlF ₃ , GdF ₃ , and YbF ₃ are added to the above composition, and the glass composition is as follows: Is achieved by the fluoride glass composition in the range shown in the following.

35 ≦ InF ₃ ≦ 40 mol%, 10 ≦ BaF ₂ ≦ 25 mol%, 15 ≦ ZnF ₂ ≦ 20 mol%, 5 ≦ PbF ₂ ≦ 25 mol%, 5 ≦ SrF ₂ ≦ 15 mol%, 0. 5 ≦ AlF ₃ ≦ 3.8 mol%, 0.5 ≦ GdF ₃ ≦ 4.0 mol%, 0.5 ≦ YbF ₃ ≦ 4.0 mol% Further, the ratio R of the contents of InF ₃ and ZnF ₂ (R ( R = [I
_{nF 3] / [ZnF 2]} ) is, 1.8 ≦ R ≦ 2.5, and AlF _3, GdF _3, each of the sum of the content Z (Z = [AlF ₃ of YbF _3] + [GdF ₃ ] + [Yb
F ₃ ]) is achieved by a glass composition in which 2.0 ≦ Z ≦ 8.0 mol%.

That is, I reported in the above report example
nF ₃ , InF ₃ , BaF ₂ , ZnF ₂ , PbF ₂ , S
AlF as an additive to glass composed of rF ₂
F ₃ , GdF ₃ and YbF ₃ are added. At that time, if the values of R and Z are within the above-mentioned limited range, a homogeneous glass free from crystallization can be obtained. R
If the values of Z and Z are out of the above-mentioned limited range, the rate of precipitation of crystals in the melt during the cooling process increases, and it becomes difficult to obtain a homogeneous glass.

Hereinafter, each component will be described in detail.
InF ₃ and ZnF ₂ are indispensable components for glass formation.
The content and the ratio R thereof are preferably in the above-mentioned limited range. Outside this range, the melt may become homogeneous, but the melt may become emulsified during cooling. Further preferably, 1.9 ≦ R ≦ 2.2.

BaF ₂ and SrF ₂ are essential components of this glass, and the content thereof is preferably within the above-mentioned limited range. Outside this range, the rate of crystallization during cooling will be significantly faster.
More preferably, 15 ≦ BaF ₂ ≦ 20 mol% and 5 ≦ SrF ₂ ≦ 10 mol%.

PbF ₂ is an essential component for increasing the refractive index of glass. Even when the content of PbF ₂ is lower than the lower limit of the above-mentioned limited range, a glass that is sufficiently stable against crystallization can be obtained, but the refractive index is as low as about 1.50, and the numerical aperture when a fiber is made, They are often short and unsuitable for the above-mentioned applications. If the content of PbF ₂ is higher than the upper limit of the above-mentioned limited range, a homogeneous melt may be formed, but fine crystals may precipitate or the crystallization rate during cooling may be significantly increased.

AlF ₃ , GdF ₃ and YbF ₃ are essential components for stabilizing the InF ₃ -based glass of the above reported example against crystallization. The respective contents and the sum Z of the contents are preferably in the above-mentioned limited ranges. Further preferably, 1.0 ≦ AlF ₃ ≦ 3.0 mol%, 1.5 ≦ GdF ₃ ≦ 2.5 mol%, 1.0 ≦ YbF ₃ ≦ 2.5 mol%, 4.0 ≦ Z ≦ 7. When added to satisfy 0.0 mol%, the glass is remarkably stabilized against crystallization. However, when it is lower than the lower limit of the above-mentioned limited range, the crystallization rate during cooling is high, and it is not suitable for spinning. If it is higher than the upper limit, a uniform melt cannot be obtained, or microcrystals precipitate during cooling.

Furthermore, YbF ₃ acts as a sensitizer for Pr ^{3+ as} an active species in, for example, application to a praseodymium (Pr ³⁺ ) -doped fluoride glass fiber amplifier, so that the excitation efficiency is improved. This can increase the amplification efficiency.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail based on embodiments.

(Example 1) As shown in Table 1, the composition of the obtained glass is represented by mol, and InF ₃ : 35%, Ba
F ₂ : 15%, ZnF ₂ : 19%, PbF ₂ : 20%, S
rF ₂ : 5%, AlF ₃ : 2%, GdF ₃ : 2%, Yb
F ₃ : 2%, 15 g of the total amount was weighed and melted at 800 ° C. for 1 hour in an inert gas atmosphere using a gold crucible.

[0021]

[Table 1]

Thereafter, the obtained melt is poured into a mold having a diameter of 15 mm and a depth of 40 mm preheated to 300 ° C.
It was placed in an electric furnace at 00 ° C. and gradually cooled to room temperature over 6 hours. The obtained compound of the above composition is a colorless transparent body,
In the differential thermal analysis, a glass transition point of 258 ° C. and a crystallization start point of 333 ° C. were observed. Further, since only a halo pattern peculiar to the amorphous phase was found in the X-ray diffraction, it was determined that the obtained compound was glass.

When the refractive index (n _d ) of the obtained glass at the Na-d line was measured, as shown in Table 1, n _d =
1.557. Therefore, the obtained glass was used as a core, and a glass containing no PbF ₂ (eg, in terms of composition, ZrF ₄ : 47%, BaF ₂ : 20%, La
F ₃ : 3%, YF ₃ : 3%, AlF ₃ : 6%, NaF: 2
The use of 1%, a glass) is a cladding, n _d of the glass since 1.494, fiber NA = 0.44 is obtained.

To evaluate the quantum efficiency, PrF ₃ was added to this glass so as to be 500 ppm by weight,
When the fluorescence lifetime of ¹ G ₄ level of r ³⁺ was measured, 220 μ
s. For comparison, a conventional ZrF ₄ glass (composition: ZrF ₄ : 43%, BaF ₂ : 19%, LaF ₃ :
3%, YF ₃ : 6%, AlF ₃ : 6%, NaF: 13%,
When the fluorescence lifetime in PbF ₂ (10%) was measured, 12
4 μs.

From these, the quantum efficiency for the 1.3 μm radiative transition of Pr ³⁺ from ¹ G ₄ to ³ H ₅ is calculated (Yasutake Oishi et al., IEICE Technical Report, OQE91-18, p1
-5), which is 3.8% for the ZrF ₄ -based glass, and 6.8% for the glass of this example, which is extremely high.

(Examples 2 to 6) A total of 15 g of the raw materials were weighed so that the compositions shown in Table 1 were obtained, and a gold crucible was used in the same manner as in Example 1 at 800 ° C. in an inert gas atmosphere. 1
After melting for an hour, the diameter 15 preheated to 300 ° C.
It was poured into a mold having a thickness of 40 mm and a depth of 40 mm, placed in an electric furnace at 300 ° C., and gradually cooled to room temperature over 6 hours. The obtained compound having the above composition was a colorless and transparent substance, and the glass transition point and the crystallization start point having the values shown in Table 1 were observed in the differential thermal analysis. Further, since only a halo pattern peculiar to the amorphous phase was found in the X-ray diffraction, it was determined that the obtained compound was glass.

[0027] When a n _d of the resulting glass was measured,
The values are as shown in Table 1. For example, the composition is expressed in mol, ZrF ₄ : 47%, BaF ₂ : 20%, LaF ₃ : 3
_{%, YF 3: 3%,} AlF 3: 6%, NaF: the use of the glass is 21% in the cladding, n _d of the glass 1.
Since it is 494, a fiber with NA = 0.23 to 0.44 is obtained.

(Comparative Example 1) As shown in Table 2, the composition of the obtained glass is represented by mol, and InF ₃ : 35%, Ba
F ₂ : 18%, ZnF ₂ : 19%, PbF ₂ : 10%, S
rF ₂ : 9%, AlF ₃ : 2%, GdF ₃ : 5%, Yb
F ₃ : 2%, 15 g in total was weighed and melted at 800 ° C. for 1 hour in an inert gas atmosphere using a gold crucible.

Thereafter, when the obtained melt was poured into a mold having a diameter of 15 mm and a depth of 40 mm, which was preheated to 300 ° C., complete crystallization of the obtained compound having the above composition was observed.

[0030]

[Table 2]

(Comparative Example 2) As shown in Table 2, the composition of the obtained glass is represented by mol, and InF ₃ : 40%, Ba
F ₂ : 20%, ZnF ₂ : 20%, PbF ₂ : 10%, S
A total of 15 g was weighed so that rF ₂ : 10%,
Using a gold crucible, 800 ° C, 1
Time melting was performed.

Thereafter, the obtained melt was poured into a mold having a diameter of 15 mm and a depth of 40 mm preheated to 300 ° C.
It was placed in an electric furnace at 00 ° C. and gradually cooled to room temperature over 6 hours. It was observed that microcrystals precipitated in the obtained compound having the above composition.

(Comparative Example 3) As shown in Table 2, the composition of the obtained glass is represented by mol, and InF ₃ : 37%, Ba
F ₂ : 22%, ZnF ₂ : 19%, PbF ₂ : 3%, Sr
_{F 2: 12%, AlF 3} : 2%, GdF 3: 3%, Yb
F ₃ : 2%, 15 g in total was weighed and melted at 800 ° C. for 1 hour in an inert gas atmosphere using a gold crucible.

Thereafter, the obtained melt was poured into a mold having a diameter of 15 mm and a depth of 40 mm preheated to 300 ° C.
It was placed in an electric furnace at 00 ° C. and gradually cooled to room temperature over 6 hours. The obtained compound of the above composition is a colorless transparent body,
In the differential thermal analysis, a glass transition point of 283 ° C. and a crystallization start point of 348 ° C. were observed. Further, since only a halo pattern peculiar to the amorphous phase was found in the X-ray diffraction, it was determined that the obtained compound was glass.

When the refractive index (n _d ) of the obtained glass at the Na-d line was measured, as shown in Table 2, n _d =
1.502. Therefore, the obtained glass was used as a core, and a glass containing no PbF ₂ (eg, in terms of composition, ZrF ₄ : 47%, BaF ₂ : 20%, La
F ₃ : 3%, YF ₃ : 3%, AlF ₃ : 6%, NaF: 2
Even if (1% glass) is used for the cladding, the glass has a small numerical aperture of NA = 0.15 since the glass has n _d of 1.494.

(Comparative Examples 4 to 15) A total of 15 g of the raw materials were weighed so that the compositions shown in Table 2 were obtained, and a gold crucible was used in the same manner as in Example 1 at 800 ° C. under an inert gas atmosphere.
After melting for a time, the diameter is 15 mm and the depth is 40 mm
, And slowly cooled in an electric furnace at 300 ° C. However, in any of the materials, since the content of the glass component or the value of R or Z was outside the above range of the present invention, slight precipitation of fine crystals or complete devitrification was observed.

[0037]

As can be seen from the above examples, the fluoride glass of the present invention is stable against crystallization, and the fluorescence lifetime of rare earth ions added to the glass of the present invention is conventionally known. It is much longer than that of a certain composition.

That is, since the quantum efficiency is greatly improved, by using the glass of the present invention as a core glass of an optical communication fiber, particularly a core glass of a rare earth ion-doped fiber for a fiber amplifier or a fiber laser, the performance thereof is dramatically improved. Significant improvement is expected.

Claims (2)

(57) [Claims] 1. InF ₃ , BaF ₂ , ZnF ₂ , PbF ₂ ,
In a fluoride glass composition containing SrF ₂ and SrF ₂ as main components, the above composition is mixed with AlF ₃ , GdF ₃ and YbF
_3. A fluoride glass composition to which ₃ is added and the glass composition is in the range shown below. 35 ≦ InF ₃ ≦ 40 mol%, 10 ≦ BaF ₂ ≦ 25 mol%, 15 ≦ ZnF ₂ ≦ 20 mol%, 5 ≦ PbF ₂ ≦ 25 mol%, 5 ≦ SrF ₂ ≦ 15 mol%, 0.5 ≦ AlF ₃ ≦ 3.8 mol%, 0.5 ≦ GdF ₃ ≦ 4.0 mol%, 0.5 ≦ YbF ₃ ≦ 4.0 mol% 2. The ratio R (R) of the contents of InF ₃ and ZnF _2.
= [InF ₃ ] / [ZnF ₂ ]) is 1.8 ≦ R ≦ 2.5, and the sum Z (Z = [AlF ₃ ] +) of the respective contents of AlF ₃ , GdF ₃ and YbF ₃ [GdF ₃ ] + [Yb
The fluoride glass composition according to claim 1, wherein F ₃ ]) satisfies 2.0 ≦ Z ≦ 8.0 mol%.