JPH11228182A - Tellurite glass fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide tellurite glass fiber being low loss, high NA and having a high light emission efficiency. SOLUTION: The core glass consists of one composition among a Te-Zn-Ba- Ge base, a Te-Zn-Ba-R base and a Te-Zn-Pb base. The clad glass consists of a component composition of one among the Te-Zn-Ba-Ge base, Te-Zn-Ba-R base and Te-Zn-Pb base, which is added either one of Ge or B and alkali metal R. The Te-Zn-Ba-Ge base consists of (by mol.%) 50<TeO2 <70, 2<GeO2 <15, 7<BaO<15 and 7<ZnO<25. The Te-Zn-Ba-R base consists of, by mol.%, 60<TeO2 <80, 5<BaO<20, 5<ZnO<20, and 5<R2 O<15. The Te-Zn-Pb base consists of, by mol.%, 50<TeO2 <80, 5<ZnO<20, and 15<PbO<40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tellurite glass fiber which can be used for a light guide for sensing, an optical amplifier, a fiber laser, a nonlinear element, and the like.

[0002]

2. Description of the Related Art Tellurite glass has the best transmission characteristics in a long wavelength region among oxide glasses, and has good light emission characteristics when rare earth elements such as Nd and Er are added. In addition, it shows a large nonlinear constant. Because of these features, applications to light guides, lasers, optical amplifiers, nonlinear elements, and the like having a wide transmission wavelength range are expected.

[0003]

In order to realize these optical devices, it is necessary to convert tellurite glass into a fiber. However, since it is actually difficult to manufacture a fiber, any of the optical devices has good characteristics. Has not been realized. One of the difficulties in fabricating fibers is that there is no known thermally stable glass composition that can withstand the fiber fabrication process.

For example, US Pat. No. 5,251,062 discloses that 58-84% of TeO ₂ , O.D. 05 to 24% of Na ₂ O, and 3-component glass comprising 10 to 30% ZnO is described as suitable for fiber production.
However, the glass having this composition range has a difference between the crystallization temperature and the glass transition temperature of about 90 to 130 ° C., and with such a degree of stability, considerable quenching is required for glass production in order to prevent precipitation of crystals.

[0005] In the case of tellurite glass, if it is formed by quenching, unevenness in the refractive index due to stress is very likely to occur, so that a fiber with low loss cannot be obtained. In other words, in order to obtain a low-loss fiber, extremely stable glass is required so that rapid cooling is not required, but such a glass has not been obtained conventionally. As a result, the losses of the tellurite glass fibers reported so far are as large as 1 dB / m.

If the glass does not require quenching, the fiber can be drawn directly from the glass by a double crucible method without going through complicated steps, and it becomes very easy to produce a low-loss fiber. However, there has never been such a stable glass in the tellurite glass system.
Nobody has yet reported an example of the production of tellurite glass fiber by the double crucible method.

[0007] In addition, US Pat.
With component glasses, it is difficult to produce high NA single mode fibers required for applications such as optical amplifiers and nonlinear elements. In the above U.S. Patent, a method of changing the concentration of alkali ions to give a refractive index difference between the core and the clad is described. As a result, the viscosity characteristics of the glass also change, so that the alkali ion concentration can be changed only slightly. Therefore, this method cannot ensure a substantially large refractive index difference. Since two glasses with a large difference in alkali ion concentration cannot be simultaneously drawn, a glass with a large difference in refractive index with a alkali concentration cannot be used as a combination of a core and a clad.

When a fiber is used as a laser or an optical amplifier, it is necessary to obtain not only a low-loss fiber but also a high luminous efficiency when a rare earth element such as Er and Pr is added. is there. However, conventionally, the relationship between the composition of the tellurite glass and the luminous efficiency has not been known.

An object of the present invention is to solve such a problem and to provide a tellurite glass fiber which is easy to manufacture.

Another object of the present invention is to provide a low loss, high NA tellurite glass fiber.

Another object of the present invention is to provide a tellurite glass fiber having good luminous performance when a rare earth element is added.

The present invention further relates to a low-loss wide-wavelength light guide, and a tellurite glass that can be used as a light-emitting medium or an optical amplification medium for an optical amplifier, fiber laser, nonlinear optical element, or the like that can cope with the wavelength range. The purpose is to present the fiber.

[0013]

In the present invention, the core glass is made of a Te-Zn-Ba-Ge system, Te-Zn-Ba-R.
And any one of a Te-Zn-Pb-based composition and the clad glass is a Te-Zn-Ba-Ge-based,
The composition is such that one of Ge and B and an alkali metal R are added to one of the e-Zn-Ba-R system and the Te-Zn-Pb system.

[0014] This makes it possible to obtain a large difference in the refractive index while being thermally stable, making the core and the clad have the same viscosity. As a result, rapid cooling becomes unnecessary, and a large numerical aperture can be realized.

When the core glass is made of any one of a Te—Zn—Ba—Ge system and a Te—Zn—Ba—R system, high luminous efficiency can be obtained when a rare earth element such as Er is added. Can be achieved. As a result, a high-efficiency optical amplifier, fiber laser, and non-linear element that can handle a wide wavelength range can be realized.

By forming the core glass with a Te-Zn-Pb-based component composition and the clad glass with a Te-Zn-Pb-based component composition with addition of Ge and alkali metal R, a transparent fiber in a wide wavelength range can be obtained. That is, a fiber that can be used as a light guide for sensing can be realized.

The composition of the Te—Zn—Ba—Ge system is 50% by mole from the viewpoint of thermal stability, transmission characteristics and emission characteristics.
<TeO ₂ <70, ₂ <GeO ₂ <15, 7 <BaO <1
5 and 7 <ZnO <25 are preferred.

The composition of the Te—Zn—Ba—R system has a molar percentage of 60 <60 from the viewpoints of thermal stability, transmission characteristics and emission characteristics.
TeO ₂ <80, 5 <BaO <20, 5 <ZnO <20
And 5 <R ₂ O <15. The alkali metal R is, for example, Na or K.

The composition of the Te—Zn—Pb system has thermal stability,
From the viewpoint of transmission characteristics and emission characteristics, 50 <TeO in mol%
₂ <80, 5 <ZnO <20 and 15 <PbO <40 are preferred.

Since the clad glass is made up of the same component composition as that contained in the core glass and one of Ge and B and an alkali metal R added, the basic composition excluding the additives of the clad glass becomes the core glass. And the clad glass are the same, and the viscosity and the thermal characteristics are the same so that the production becomes easy.

[0021]

Embodiments of the present invention will be described below in detail.

The inventor of the present application prepared ternary glasses of various compositions and investigated the thermal stability of tellurite glass. FIG. 1 shows the metal ion component ratio, the glass transition point Tg (ΔC), the crystallization temperature Tx (ΔC), and the difference Tx−Tg between the crystallization temperature Tx and the glass transition point Tg of the ternary glass. The larger the temperature difference Tx-Tg, the more stable the glass. As shown in FIG. 1, the stable ternary glass in which crystallization is not observed is only a Te—Zn—Pb-based glass, and any other ternary glass has a crystallization temperature Tx.
It has been found that its thermal stability is insufficient to make low loss fibers.

Therefore, an attempt was made to improve the stability of the Te-Zn-Ba-based glass, which is next to the Te-Zn-Pb-based glass, by converting the glass into four components. FIG. 2 shows an example of a glass composition in which no crystallization was observed by DSC measurement. G
It has been found that the addition of e, B or alkali metal R (R is Na or K) is extremely effective in stabilizing the Te—Zn—Ba glass. In the case of an alkali metal, Na was the most effective, but K had almost the same effect. Therefore, in the present specification, both are collectively denoted by R.

Next, transmission wavelength characteristics and emission characteristics of the ternary glass of Te—Zn—Pb and the stabilized quaternary glass were examined. FIG. 3 shows transmittance wavelength characteristics of a glass sample having a thickness of 5 mm measured by the FTIR method. The material having the widest transmission wavelength range is a Te—Zn—Pb-based glass, which transmits light up to 6.3 μm. Then, Te-Z
The glass in which Ge or R was added to the n-Ba system transmitted light up to 6 μm. In the glass obtained by adding B to the Te-Zn-Ba system, even when the addition amount of B was 10%, the transmission range was significantly reduced, and the glass was transmitted only up to 3.5 μm. From this result, the Te-Zn-Pb-based glass is most suitable as a wide-wavelength light guide, and the glass obtained by adding B to the Te-Zn-Ba-based glass, generally, the glass to which B is added is widely used. It turned out that it was not suitable for use as a wavelength band light guide.

FIG. 4 shows the emission characteristics in the 1.5 μm band when 5,000 ppm of Er is added. The excitation wavelength is 1.48 μm. Te containing 10 mol% or less of Ge
-The Zn-Ba-Ge glass had the highest emission intensity. 70Te-17Zn-10Ba-3Ge glass is
No. 7 described in US Pat. No. 5,251,062.
It has an emission intensity 1.6 times that of 0Te-20Zn-10Na glass. Next, the light emission of the Te-Zn-Ba-R-based glass is strong. These quaternary glasses are made of fiber lasers.
It is suitable for applications such as lasers and optical amplifiers.

The Te—Zn—Ba—B-based glass is obtained from the above 2
Since light emission is weaker than that of two glass systems, it is not suitable for use in light emitting devices such as fiber lasers and optical amplifiers.

From these characteristics, as the fiber core glass, a three-component system composed of Te—Zn—Pb, a Te—Zn—Ba—Ge system and a Te—Zn—Ba—
It has been found that an R quaternary glass is suitable. Therefore, the stable composition regions of these three glass systems were examined in detail. FIGS. 5, 6 and 7 show Te—Zn—Ba—Ge, respectively.
2 shows composition regions in which crystallization is not observed in the system, Te—Zn—Ba—Na system, and Te—Zn—Pb system. 5 and 6
7 and FIG. 7, ○ indicates a sample exhibiting thermally stable characteristics, and X indicates a sample exhibiting thermally unstable characteristics. Will be.

Based on the thermal stability, transmission characteristics, and light emission characteristics described above, the core glass suitable for an optical amplifier, a fiber laser, and the like is 50 <TeO ₂ <70, ₂ <GeO ₂ <1
T in the range of 5, 7 <BaO <15 and 7 <ZnO <25
e-Zn-Ba-Ge glass or 60 <TeO ₂
<80, 5 <BaO <20, 5 <ZnO <20, and 5
<R ₂ O (R = Na or K) Te—Zn in the range of 15
-Ba-R glass. The core glass suitable for the light guide for sensing is 50 <TeO ₂ <80, 5 <
Te in the composition range of ZnO <20 and 15 <PbO <40
—Zn—Pb glass.

The preferred composition as the clad glass for these core glasses is as follows. That is, the clad glass is prepared by further adding Ge or B and R as a pair to the composition of the core glass. Ge, B and R all have the function of lowering the refractive index, Ge and B increase the viscosity of the glass, and R has the function of lowering the viscosity.
When Ge and R or B and R are added as a pair, the refractive index can be reduced while maintaining the same viscosity as the core glass. For example, in terms of the glass transition point, the addition of 1 mol% of Ge or B increases the glass transition point slightly more than 2 ° C, and the addition of the same amount of R lowers the glass transition point slightly more than 2 ° C. Therefore, Ge
Alternatively, the refractive index can be reduced without changing the glass transition point by adding R in substantially the same amount as B.

In addition, Ge or B and R are added in pairs.
The component glass is extremely stable, as shown in the measurement example by DSC in FIG. 8, and has a wider stable composition region than the core glass. Therefore, both the core and the clad can be formed without quenching. That is, a combination of thermally stable core glass and clad glass can be realized.

Glass to which BR is added is not suitable for a fiber intended for a light guide for sensing because of a narrow transmission wavelength range, but can be used as a cladding glass in a wavelength range up to about 2 μm. On the other hand, the glass to which Ge-R is added has a wide transmission wavelength range, and thus is suitable not only as a light emitting device but also as a cladding glass for a light guiding fiber.

Actually, the core glass composition is 65 Te-20
Zn-10Ba-5Ge with a cladding glass composition of 50
A single mode fiber of Te-14Zn-10Ba-15Ge-11Na was prepared by a double crucible method.
The core diameter of the produced fiber is 2.3 μm, and the NA is 0.3.
32. FIG. 9 shows a loss-wavelength characteristic of the prepared fiber. The minimum loss value is 110d at a wavelength of 1.47 μm.
B / km, 120 dB / km at 1.55 μm,
A loss value as low as about 1/10 of the conventional tellurite fiber can be achieved. The sharp increase in loss on the longer wavelength side than 1.5 μm is due to absorption by water, and further reduction in loss can be expected by incorporating a dehydration step into the fiber manufacturing process.

[0033]

As can be easily understood from the above description, according to the present invention, a low-loss fiber which does not require quenching in the fiber manufacturing process and has little variation in refractive index and irregularities in the core-cladding interface can be produced. it can. Further, by adding Ge-R or BR as a pair, the refractive index can be reduced without changing the viscosity of the glass, and the refractive index difference can be increased, so that a large numerical aperture (NA) Fiber can be created.

The newly discovered composition has a high luminous efficiency when a rare earth element is added, so that it can be used as a luminous medium or an optical amplifying medium such as a fiber laser and an optical amplifier. realizable.

Further, a light guide having a wider transmission wavelength range and a wider wavelength range than before can be realized.

That is, according to the present invention, a fiber having a low loss, a high NA, and a high luminous efficiency can be produced, so that a light guide, a fiber laser, an optical amplifier, a nonlinear optical element, etc., having a long wavelength or a wide wavelength range can be realized. it can.

[Brief description of the drawings]

FIG. 1 is a table showing a metal ion component ratio, a glass transition point Tg, a crystallization temperature Tx, and a difference Tx-Tg between the crystallization temperature Tx and the glass transition point Tg of a ternary glass.

FIG. 2 is a table showing glass compositions in which crystallization was not observed.

FIG. 3 shows transmission wavelength characteristics of a ternary glass of Te—Zn—Pb and a stabilized quaternary glass.

FIG. 4 is a table showing the emission intensity in the 1.5 μm band when Er is added.

FIG. 5 is a view showing a composition region where crystallization of a Te—Zn—Ba—Ge system is not observed.

FIG. 6 is a diagram showing a composition region where crystallization of a Te—Zn—Ba—Na system is not observed.

FIG. 7 is a diagram showing a composition region in which crystallization of a Te—Zn—Pb system is not observed.

FIG. 8 shows the measurement results of the thermal stability characteristics of a five-component glass to which Ge-R or Ge-B is added as a pair.

FIG. 9 shows a loss of a fiber prepared according to the present embodiment.
It is a wavelength characteristic.

Continuing on the front page (72) Inventor Tetsuya Nakai 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo International Telegraph and Telephone Corporation (72) Inventor Toshio Tani 2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo International Inside Telegraph and Telephone Co., Ltd. (72) Inventor Tomomi Sudo 2-7-12 Omorikita, Ota-ku, Tokyo Inside Furuuchi Chemical Co., Ltd. (72) Inventor Shunichi 2-7-12 Omorikita, Ota-ku, Tokyo Furuuchi Chemical Co., Ltd.

Claims (9)

[Claims] 1. Te-Zn-Ba-Ge system, Te-Zn
A core glass composed of any one of a Ba—R system and a Te—Zn—Pb system; and a Te—Zn—Ba—Ge system, a Te—Zn—Ba—R system, and a Te—Zn—Pb system. A tellurite glass fiber characterized by comprising one of Ge and B and a clad glass having a component composition to which an alkali metal R is added. 2. The method according to claim 1, wherein the core glass is Te-Zn-B.
2. The tellurite glass fiber according to claim 1, wherein the tellurite glass fiber is made of any one of a-Ge-based and Te-Zn-Ba-R-based components and further added with a rare earth element. 3. The tellurite glass fiber according to claim 2, wherein said rare earth element is Er. 4. The method according to claim 1, wherein the core glass is Te—Zn—Pb.
And the cladding glass is composed of the T
The tellurite glass fiber according to claim 1, comprising a component composition obtained by adding Ge and an alkali metal R to an e-Zn-Pb system. 5. The composition of the Te—Zn—Ba—Ge system in which the molar percentage is 50 <TeO ₂ <70, ₂ <GeO ₂ <1.
3. The tellurite glass fiber according to claim 1, wherein 5, 7 <BaO <15 and 7 <ZnO <25. 6. The composition of the Te—Zn—Ba—R system,
60 <TeO ₂ <80, 5 <BaO <20, 5
_{2. The method according} to claim 1, wherein said ZnO <20 and 5 <R2O <15.
Or the tellurite glass fiber according to 2. 7. The tellurite glass fiber according to claim 1, wherein said R is any one of Na and K. 8. The composition of the Te—Zn—Pb-based compound in which, in mol%, 50 <TeO ₂ <80, 5 <ZnO <20 and 15
5. The tellurite glass fiber according to claim 1, comprising <PbO <40. 6. 9. The tellurite glass fiber according to claim 1, wherein the clad glass comprises a component obtained by adding one of Ge and B and an alkali metal R to the same component composition as that contained in the core glass.