Optical amplifying glass

Details Optical amplifying glass Optical amplifying glass

2001-08-08

2003-07-29

Sample, David (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C501S073000, C501S037000, C501S055000

Reexamination Certificate

active

06599852

ABSTRACT:

The present invention relates to an optical amplifying glass. Particularly, it relates to an optical amplifying glass capable of amplification in a broad band range for lights with wavelengths of from 1.4 to 1.5 &mgr;m.
For the purpose of application to an optical amplifier in an optical communication system, there have been research and development of an optical amplifying glass comprising a core glass and a clad glass and having a rare earth element incorporated to the core glass.
On the other hand, to cope with diversification of communication services expected in future, a wavelength division multiplexing communication system (WDM) has been proposed to increase the transmission capacity. In WDM, the transmission capacity will increase, as the number of wavelength division multiplexing channels increases.
Heretofore, an Er (erbium)-doped optical amplifying glass has been proposed as a glass suitable for optical amplification of C band (wavelength: 1,530 to 1,560 nm) or L band (wavelength: 1,570 to 1,600 nm), and a Tm (thulium)-doped optical amplifying glass has been proposed as a glass suitable for optical amplification of S
+
band (wavelength: 1,450 to 1,490 nm) and S band (wavelength: 1,490 to 1,530 nm).
To the Tm-doped optical amplifying glass, an excitation light is introduced together with a light to be amplified i.e. a signal light, and the signal light will be amplified by means of a stimulated emission transition of Tm. The wavelength of the excitation light is typically from 1.0 to 1.6 &mgr;m, when excitation is carried out by an upconversion method. Further, the Tm-doped optical amplifying glass is usually used in the form of a fiber.
In the Tm-doped optical amplifying glass, optical amplification of S
+
band is carried out by means of the stimulated emission transfer between
3
H
4
-
3
F
4
. However, below the
3
H
4
level, there is a near level
3
H
5
at a distance of about 4,300 cm
−1
. When the phonon energy of the glass containing Tm
3+
is large, due to this level
3
H
5
, the multiphonon relaxation in the above-mentioned stimulated emission transfer, increases, and the radiation relaxation decreases, whereby the emission efficiency, accordingly, the optical amplification factor, may decrease.
As a Tm-doped optical amplifying glass, an optical amplifying glass having Tm doped to a fluoride glass (a fluoride type Tm-doped optical amplifying glass) has been proposed. The fluoride glass has a merit such that the multiphonon relaxation is less than an oxide glass. However, the glass transition point T
g
of the fluoride type Tm-doped optical amplifying glass is low (typically not higher than 320° C.), and it was likely to be thermally damaged, when the intensity of the excitation light was high.
Further, the Vickers hardness H
v
of the fluoride type Tm-doped optical amplifying glass is low (typically, 2.4 GPa), whereby it was susceptible to scratching, and when it is made into a fiber, such a scratch is likely to cause breakage.
As an optical amplifying glass having Tm doped to a fluoride glass, a Tm-doped fluoride glass ZBLAN is, for example, known which has 1.19% by mass percentage of Tm doped to a matrix glass of a composition, as represented by mol %, comprising 52.53% of ZrF
4
, 20.20% of BaF
2
, 3.03% of LaF
3
, 4.04% of AlF
3
and 20.20% of NaF and which has a T
g
of 200° C., a peak wavelength of the emission spectrum of 1,452 nm and a half value thereof being 76 nm (Applied Optics, 39(27), 4,979-4,984 (2000)).
Further, as an optical amplifying glass having Tm doped to a tellurite glass, a Tm-doped terlite glass is, for example, known which has 1.23% by mass percentage of Tm doped to a matrix glass with a composition, as represented by mol %, comprising 75% of TeO
2
, 10% of ZnO and 15% of Na
2
O and which has a peak wavelength of the emission spectrum of 1,458 nm and a half value width thereof being 114 nm. However, its T
g
is as low as 295° C. (Applied Optics, 39(27), 4,979-4,984 (2000)).
Further, a glass having 0.01%, 0.05% or 1.5% by outer mass percentage of Tm doped to a matrix glass comprising 56 mol % of PbO, 27 mol % of Bi
2
O
3
and 17 mol % of Ga
2
O
3
(Tm-doped PbO—Bi
2
O
3
—Ga
2
O
3
glass) is disclosed (Applied Optics, 34(21), 4,284-4,289 (1995)).
The annealing point and the Knoop hardness of the above matrix glass are 319° C. and 2.2 GPa, respectively (Phys. Chem. Glasses, 27, 119-123 (1986)). The annealing, point may be deemed to be equal to T
g
, and it is considered that there will be no substantial change in T
g
even if Tm is doped up to 1.5%. Namely, T
g
of the above Tm-doped PbO—Bi
2
O
3
—Ga
2
O
3
glass is also about 320° C., whereby the above-mentioned thermal damage is likely to result.
Further, in the case of an optical glass, the Knoop hardness gives a value lower by from 0.4 to 1.3 GPa than H
v
(Dictionary of Glass, p. 352, published by Asakura Shoten, 1985). Accordingly, H
v
of the above Tm-doped PbO—Bi
2
O
3
—Ga
2
O
3
is considered to be within a range of from 2.6 to 3.5 GPa and can not be said to be high.
It is an object of the present invention to provide an optical amplifying glass which has high T
g
and H
v
and which is capable of amplifying lights in S
+
band and S band.
The present invention provides an optical amplifying glass comprising a matrix glass and from 0.001 to 10% by mass percentage of Tm doped to the matrix glass, wherein the matrix glass contains from 15 to 80 mol % of Bi
2
O
3
and further contains at least one component selected from the group consisting of SiO
2
, B
2
O
3
and GeO
2
.


REFERENCES:
patent: 4790619 (1988-12-01), Lines et al.
patent: 5093287 (1992-03-01), Borrelli et al.
patent: 5093288 (1992-03-01), Aitken et al.
Kasamatsu et al., 1.50-&mgr;m-band gain-shifted thulium-doped fiber amplifier with 1.05- and 1.56-&mgr;m duaql-wavelength pumping, Dec. 1, 1999, Optics Letters, vol. 24, No. 23, 1684-1686.*
Jon Heo, Yong Beom Shin, and Joo Nyung Jang Applied Optics, vol. 34, No. 21, Jul. 20, 1995 pp. 4284-4289 Spectroscopic analysis of Tm3+in PbO-Bi2O3-Ga2O3Glass.

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