WO2003022763A2

WO2003022763A2 - Bismuth oxide-containing glass comprising lanthanum oxide

Info

Publication number: WO2003022763A2
Application number: PCT/US2002/028572
Authority: WO
Inventors: Joseph S. Hayden; Paula Vullo
Original assignee: Schott Glas
Priority date: 2001-09-10
Filing date: 2002-09-09
Publication date: 2003-03-20
Also published as: WO2003022763A3; AU2002343344A8; AU2002343344A1

Abstract

This invention relates to a bismuth oxide glass containing lanthanum oxide, a process for the production of such a glass, and the use of such a glass.

Description

Bismuth oxide-containing glass comprising lanthanum oxide

This application claims the benefit of priority of U.S. Provisional Patent Application Serial No. 60/317,973, filed September 10, 2001.

Description

This invention relates to a bismuth oxide glass containing lanthanum oxide, a process for the production of such a glass, and the use of such a glass .

Optical amplifier units represent one of the key components of modern optical communications engineering, in particular of WDM technology ("wavelength division multiplexing") . Previously the prior art used mainly quartz glasses doped with optically active ions as the core glass for such optical amplifiers. Amplifiers doped with Er and based on Si0₂ make it possible simultaneously to amplify several closely neighboring channels differentiated by wavelength in the range of 1.5 μ . But because of the only narrow-band emission of the Er in Si0₂ glasses, the latter are not suited for the increasing need for transmission capacity.

Accordingly the need is growing for glasses from which rare earth ions emit in clearly broader bands than from Si0₂ glasses.

Here glasses are favored with heavy elements, in particular heavy metal oxide glasses (HMO glasses) . Because of their weak interatomic bonds, these heavy metal oxide glasses have large interatomic electrical fields and thus lead, because of a larger Stark splitting between the base state and the excited state, to a broader emission of the rare earth ions. Glasses containing bismuth oxide are also proposed as such heavy metal oxides.

For certain applications it can be advantageous that such amplifier glasses also contain lanthanum oxide. For example, lanthanum influences a glass compound with respect to physical properties in almost the same way as rare earth ions, but with the difference that lanthanum is not optically active. By replacing rare earth ions with La ions there can be produced, in addition to a component with an optically active glass, a passive component or glasses with varying rare earth concentrations which, in each case, have the same physical, optical, and thermal properties .

But the tendency to crystallize is a problem with high bismuth oxide-containing glasses. Thus JP Hll-236245 describes bismuth oxide glasses containing lanthanum oxide. But in finishing these compounds it turned out that they always crystalized and no glass was obtained. Such compounds can thus not be used for the production of fiber amplifiers in particular.

Further, the examples according to the invention of this patent all contain Cer. This is a drawback in glasses for optical amplifiers, since the Cer content produces a yellowing of the glass .

Thus, an object of this invention is to provide glasses containing bismuth oxide for optical amplifiers that could overcome the problems of the prior art .

Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.

These objects are achieved by the embodiments described herein and in the claims.

In particular, this invention relates to a glass containing bismuth-oxide that has the following composition:

Bi₂0₃ 20-70 mole % rare earth compound 0-8 mole % (based on oxide)

La₂0₃ 0.001-20 mole % other oxides 0-80 mole %

The glass compound according to the invention contains lanthanum oxide in a portion of 0.001 to 20 mole %. Preferably the content of lanthanum oxide is at most 10 mole %, more preferably at most 8 mole %. Preferably the glass according to the invention contains at least 0.005 mole % of lanthanum oxide.

It has turned out that the presence of lanthanum positively influences the devitrification stability of glasses containing bismuth oxide. It was determined by experiments that, in the devitrification of compounds containing bismuth oxide, mainly mixed crystals containing Bi/Si precipitated. It is thus assumed that the additional content of lanthanum oxide as a glass forming component can surprisingly stabilize these compounds.

In particular at higher contents of rare earth compounds, such as for example at least 0.5 mole %, lanthanum oxide has a positive effect on the glass compound.

Bismuth oxide is present in the glass according to the invention in a portion of 20 to 70 mole %. Preferably the portion of bismuth oxide in the glass is at least 30 mole %. As the top limit for bismuth oxide, 70 mole % based on oxide is contained in the glass, since above this value, despite the presence of lanthanum, the glass can easily crystallize. Preferably the portion of bismuth oxide is at most 60 mole %.

According to one embodiment, the glass containing bismuth oxide comprises at least one rare earth compound as the doping agent. This embodiment relates in particular to the use of the glasses according to the invention as optically active glasses for optical amplifiers and lasers. Preferably the rare earth compound involves at least one oxide, which is selected from oxides of Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu. Especially preferred are oxides of the elements Er, Pr, Tm, Nd and/or Dy. The glass according to the invention can also contain eerie oxide, but this embodiment is not preferred since the Ce can discolor the glass a yellowish-orange. Preferably the glass according to the invention is thus free of Ce.

Optionally Sc and/or Y compounds can be contained in the glass according to the invention, besides one or more rare earth compounds .

Preferably the rare earth compounds used as doping agents involve so-called "optically active compounds," and "optically active compounds" are understood to be those that lead to making the glass according to the invention capable of stimulated emission when the glass is excited by a suitable pump source.

According to one embodiment, the glass according to the invention is doped with at least two rare earth compounds in a total amount of 0.01 to 15 mole %. Glasses with optically active rare earth ions can be codoped with optically inactive rare earth elements, for example to increase the duration of the emission. Thus, for example, Er can be codoped with La and/or Y. To increase the pump efficiency of the amplifier, Er can, for example, also be codoped with other optically active rare earth compounds such as, for example, Yb. Gd can be codoped to stabilize the crystallization.

Especially preferably the glass according to the invention contains at least Er₂0₃ as the doping agent . By doping with other rare earth ions such as, for example, Tm, other wavelength ranges can be accessed, as in the case of Tm the so-called S-band between 1420 and 1520 n . According to other embodiments of this invention, for this reason other rare earth ions such as Tm, Yb, Pr³⁺, Nd³⁺, and/or Dy³⁺ can be preferred as the doping agent .

Further, to produce a more effective exploitation of the excitation light, sensitizers such as Yb, Ho and Nd can be added in suitable amounts, for example 0.005-8 mole %.

The content of each individual rare earth compound (s) in the glass is preferably between about 0.005 to 8 mole % based on oxide. According to one embodiment, the content of rare earth compound is between about 2 and 5 mole % based on oxide. According to another embodiment, the content of rare earth compound is about 0.01 to 2 mole % based on oxide.

The glass according to the invention can contain, besides the above-named components, other oxides with a content of 0 to 80 mole % based on oxide.

Such additional oxides can be contained to adjust physicochemical or optical properties or to lower the tendency to crystallize .

To improve fiber ductility, especially when using the glass according to the invention for an optical fiber amplifier, the addition of at least one conventional network-forming component such as Si0₂, B₂0₃, A1₂0_3/ Ge0₂, etc., is preferred.

Al₂0₃ in particular can be added to facilitate the formation of glass. Oxides of and/or Ga can be used to increase the Δλ value, i.e., to broaden the emissions cross section.

The glass according to the invention contains no gallium- and/or aluminum oxide according to one embodiment .

Further, oxides of elements can be contained that are selected from groups consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Zn, W, Ti, Zr, Cd and In.

The addition of alkaline oxides is especially advantageous if the glass is to be used for planar applications using ion exchange technology. The addition of Li₂0 can also be preferred since, in doing so, the glass formation areas are enlarged for glasses containing bismuth oxide. Li₂0 is further advantageous if an amplifier with especially good efficiency in the L-band is to be produced.

Optionally the glasses according to the invention can also contain portions of halogenide ions such as F or Cl in a weight portion of at most about 10 mole %, especially preferably at most about 5 mole % .

The glass according to the invention preferably has the following composition (in mole %) :

Bi₂0₃ 30-70 La₂0₃ 0.001-20

Si0₂ 0-60

Ge0₂ 0-30

B₂0₃ 0-60

Al₂0₃ 0-50

Ga₂0₃ 0-50 ln₂0₃ 0-30 wo₃ 0-30

Mo0₃ 0-30

Nb₂0₅ 0-30

Ta₂0₅ 0-15

Ti0₂ 0-30

Zr0₂ 0-30

Sn0₂ 0-40

M¹ ₂0 0-40

Mⁿ0 0-30

F and/ or Cl 0-10

Si0₂ and Ge0₂ 0.5-60

B₂0₃+A1₂0₃ ;+Ga₂0₃ 0.5-60 rare earth compound 0-8 (based on oxide)

where M¹ is at least one of Li, Na, K, Rb, Cs, and M¹¹ is at least one of Be, Mg, Ca, Sr, Ba and/or Zn.

If the glass according to the invention is used as a so- called passive component, preferably it contains no rare earth compound. But it can be preferred, according to certain embodiments, that even passive components such as the sheathing of a glass fiber contain slight amounts of optically active rare earth compounds .

This invention further relates to a process for the production of the glass according to the invention. The glass according to the invention is preferably produced under oxidizing conditions.

Such oxidizing conditions can be achieved preferably by blowing oxygen into the glass melt, so-called oxygen bubbling.

Further, according to this embodiment of this invention, it is preferred that dry oxygen be blown in. This promotes to a considerable extent, as a further positive effect, the dehydration of the melt. To dry the glass compound or the melt it is further preferred that the batch of starting materials be thermally pretreated, for example by drying the batch, preferably in a vacuum. The addition of halogenated oxygen also promotes dehydration so that the blowing in of halogenated oxygen is also preferred according to certain embodiments of this invention. These measures for drying the batch or the melt can be used individually or in combination with one another.

Another preferred option for producing oxidizing conditions during the glass production process is represented by the addition of oxides of polyvalent pentavalent cations, e.g., Sb as NaSb(OH)₆, Nb₂0₅, Sn0₂, Cr₂0₃, V₂0₅, As₂0₃, and/or mixtures of them to the glass compound. Since, for example, antimony has a higher electron negativity than bismuth, antimony will always oxidize possibly reduced bismuth. On the other hand, antimony is not reduced to the elementary metal, so that the glass cannot become discolored with black by precipitation of elementary metal. According to this embodiment, preferably about 0.01 to 10% by weight, more preferably up to 5% by weight (based on oxide) of a pentavalent compound is added to the glass compound.

This invention further relates to the use of a glass according to the invention for optical amplifiers, and fiber amplifiers or planar amplifiers can be involved. The glass according to the invention can be used in these amplifiers as matrix or core glass and/or sheathing glass. In such glass fibers a compound preferably similar to that of the doping is used as the sheathing glass .

Further, the glass according to the invention can be used as matrix glass and/or as passive component for a laser.

This invention further relates to a glass fiber that contains the glass according to the invention, as well as optical amplifiers that contain a glass fiber according to the invention or the glass according to the invention.

In processing the glass according to the invention as core glass for a fiberlike amplifier, the sheathing glass used preferably has a very similar composition to the core glass, and the sheathing glass is not doped with an optically active rare earth metal .

In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight .

The entire disclosure of all applications, patents and publications, cited above and below, and of corresponding U.S. Provisional Application No. 60/317,973, filed September 10, 2001 is hereby incorporated by reference.

Examples

The glass compounds entered in Table 1 were melted. None of the compounds produced showed devitrification when they cooled. Table 1

Example 1 Example 2 Example 3 Example 4

Si0₂ 27 . 0 27 32 25 . 24

B₂0₃ 20 . 0 20 20 15 . 78

Bi₂0₃ 42 . 0 42 42 42

La₂0₃ 2 . 67 2 . 65 2 . 81 2 . 8 Nb₂0₅ 5.00

Er₂0₃ 0.68 0, .69 0.66 0.65

Yb₂0₃ 2.65 2. .66 2.54 2.54

Na₂0 11.0

Sb₂0₃ 5. .00

Devitrification none none none none

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims

1. A glass composition containing bismuth oxide comprising the following (in mole %) :

Bi₂0₃ 20-70 rare earth compound 0-8 (based on oxide)

La₂0₃ 0.001-20 other oxides 0-80.

2. Glass according to claim 1, wherein the glass contains at least 0.005 to 10 mole % of La₂0₃.

3. Glass according to claim 1 or 2 , wherein the glass contains at least one rare earth compound in a portion of 0.005 to 8 mole % based on oxide that is selected from oxides of Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and/or Lu.

4. Glass according to one of the preceding claims, wherein the glass contains, in addition to La₂0₃, at least two rare earth compounds .

5. Glass according to one of the preceding claims, wherein, in addition to La₂0₃, at least Er₂0₃ is contained as a rare earth compound .

6. Glass according to one of the preceding claims, wherein the glass contains Sc and/or Y-compounds.

7. Glass according to one of the preceding claims that comprises the following composition (in mole %)

Bi₂0₃ 30-60

La₂0₃ 0.001-8

Si0₂ 0-60

Ge0₂ 0-30

B₂0₃ 0-60

Al₂0₃ 0-50

Ga₂0₃ 0-50 ln₂0₃ 0-30

W0₃ 0-30

Mo0₃ 0-30

Nb₂0₅ 0-30

Sb₂0₃ 0-30

Ta₂0₅ 0-15

Ti0₂ 0-30

Zr0₂ 0-30

Sn0₂ 0-40

M^x ₂0 - 0-40

M^lxO 0-30

F and/or Cl 0-10

Si0₂ and Ge0₂ 0.5-60

B₂0₃+A1₂0₃ +Ga 0₃ 0.5-60 rare earth compound 0.005-8 (based on oxide) where M¹ is at least one of Li, Na, K, Rb, Cs, and M¹¹ is at least one of Be, Mg, Ca, Sr, Ba and/or Zn.

8. Glass according to one of claims 1 to 6, wherein the glass contains no Al₂0₃ and/or Ga₂0₃.

9. Process for the production of a glass according to any one of claims 1 to 8, wherein the glass is melted under oxidizing conditions .

10. Process according to claim 9, wherein the oxidizing conditions are created by blowing oxygen into the glass melt .

11. Process according to claim 9 or 10, wherein a polyvalent compound selected from among Nb₂0₅,Sb₂0₅, Sn0₂, Cr₂0₃, As₂0₃, V₂0₅,and mixtures of these oxides is added to the mixture to be melted.

12. Use of a glass according to one of claims 1 to 8 as a matrix glass for optical amplifiers.

13. Use of a glass according to claim 10, wherein the optical amplifier is a fiberlike amplifier.

14. Use according to claim 11, wherein the optical amplifier is a planar amplifier.

15. Use of a glass according to one of claims 1 to 8 as matrix glass for a laser.