Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2001-06-29
2003-07-08
Sample, David (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S043000, C501S037000, C359S341500, C359S343000
Reexamination Certificate
active
06589895
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to the field of glass compositions and devices for optical amplification.
2. Description of the Related Art
In optical telecommunications networks, high bandwidth is desired for applications such as the Internet, video on demand, and videophone. In many optical communications systems, optical signals having wavelengths in the range 1530-1560 nanometers (nm) are utilized. This wavelength range corresponds to the “C-band” in telecommunications. This wavelength range also corresponds to a minimum attenuation region for silica and silica-based fibers.
Optical amplifiers are utilized to amplify the optical signals in those wavelength regions. Conventional optical amplifiers for telecommunications include erbium (Er)-doped silicate glass. The Er-doped silicate glass optical amplifier operates in the C-band and can also amplify optical signals in the 1570 nm-1620 nm range (also referred to as the L-band).
The ever-increasing demand for bandwidth has filled the erbium C-band, and is beginning to fill the L-band. In order to increase optical bandwidth, more wavelengths will need to be transmitted. One wavelength range of interest is the 1460 nm-1530 nm wavelength band, often referred to as the “S-band.” However, this wavelength band is outside of the Er-based material amplification range.
Within the 1460 nm-1530 nm wavelength band, trivalent thulium (Tm
3+
) has an emission band centered at about 1470 nm. As shown in the Tm
3+
energy diagram of
FIG. 1
, the
3
H
4
—
3
F
4
transition in Tm
3+
corresponds to an emission at about 1470 nm. In order to generate a population in the
3
H
4
energy level, for example, 790 nm radiation is absorbed by the Tm
3+
material, whereby ions are transferred to the
3
H
4
excited state from the
3
H
6
ground state.
Most Tm-doped silicate glasses have an excited state lifetime (for the
3
H
4
level) of less than 100 microseconds, due to the quenching of the upper level in silicate hosts. This short lifetime is less preferable for laser and amplification applications. Similarly, other Tm
3+
hosts, such as phosphate glass and borate glass, are also less preferable because Tm
3+
is quenched by the high phonon energy of these glasses as well.
An increased
3
H
4
excited state lifetime can be obtained with a Tm-doped host fluoride glass material, such as fluorozirconate or ZBLAN (57ZrF
4
-20BaF
2
-4LaF
3
-3AlF
3
-20NaF). The measured lifetime for the
3
H
4
excited state lifetime in ZBLAN is about 1.5 milliseconds. While laser action and optical amplification have been previously demonstrated in Tm-doped ZBLAN, this material is not advantageous for mass-produced optical amplifier applications because of the difficulties of processing fluoride glasses, the low glass transition temperature, and the less than desirable chemical durability of fluoride glasses, which suffer from deleterious effects when exposed to moisture. In addition, the emission linewidth in ZBLAN is narrow, limiting the bandwith of the amplifier.
Thus, there remains a need for optical amplifiers that operate in the 1460 nm-1530 mu wavelength band.
SUMMARY OF THE INVENTION
In view of the foregoing, according to one embodiment of the present invention, a composition comprises GeO
2
having a concentration of at least 20 mole percent, Tm
2
O
3
having a concentration of about 0.001 mole percent to about 2 mole percent, and Ga
2
O
3
, having a concentration of about 2 mole percent to about 40 mole percent. The composition can further include an alkaline earth metal compound selected from the group consisting of MgO, CaO, SrO, BaO, BaF
2
, MgF
2
, CaF
2
, SrF
2
, BaCl
2
, MgCl
2
, CaCl
2
, SrCl
2
, BaBr
2
, MgBr
2
, CaBr
2
, SrBr
2
, and combinations thereof, and having a non-zero concentration of less than about 40 mole percent. The composition can fturther include an alkali metal compound selected from the group consisting of Li
2
O, Na
2
O, K
2
O, Rb
2
O, Cs
2
O, Li
2
F
2
, Na
2
F
2
, K
2
F
2
, Rb
2
F
2
, Cs
2
F
2
, Li
2
Cl
2
, Na
2
Cl
2
, K
2
Cl
2
, Rb
2
Cl
2
, Cs
2
Cl
2
, Li
2
Br
2
, Na
2
Br
2
, K
2
Br
2
, Rb
2
Br
2
, Cs
2
Br
2
and combinations thereof, and having a non-zero concentration of less than about 20 mole percent. The emission bandwidth and lineshape of the composition in the 1450 nm to 1530 nm range can be varied on the basis of one or more composition ratios and/or other parameters.
According to another embodiment of the present invention, an optical amplification device comprises a germanate glass material doped with Tm
3+
. The germanate glass material has a first surface configured to receive an optical signal having a wavelength of from about 1460 nm to about 1540 nm and a second surface configured to output an amplified optical signal. The germanate glass material can have the composition described above. The emission bandwidth of the germanate glass material can be varied based on the composition of the material. The germanate glass material can be configured as a core for an optical fiber. The optical amplification device can further include a pump source for producing an excited
3
H
4
state in Tm
3+
.
REFERENCES:
patent: 4999321 (1991-03-01), Kohli
patent: 5420080 (1995-05-01), Wang et al.
patent: 5668659 (1997-09-01), Sakamoto et al.
patent: 5786287 (1998-07-01), Bayya et al.
patent: 6271160 (2001-08-01), Yamamoto et al.
patent: 6413891 (2002-07-01), Cho et al.
J. Y. Allain et al.,Tunable CW Lasing Around 0•82, 1•48, 1•88, and 2•35 &mgr;m In Thulium-Doped Fluoriozirconate Fibre, Electronics Letters, Nov. 23, 1989, pp. 1660-1662, vol. 25-No. 24.
S. Bayya et al., BaO-Ga2O3-GeO2glasses with enhanced properties, Journal of Non-Crystalline Solids, 1997, pp. 198-207, vol. 212, Elsevier Science B.V.
D. A. Chapman,Erbium-doped fibre amplifiers: the latest revolution in optical communications, Electronics & Communication Engineering Journal, Apr. 1994, pp. 59-67, vol. 6-No. 2, IEE.
J. Heo et al.,Spectroscopic analysis of Tm3+in PbO-Bi2O3-Ga2O3glass, Applied Optics, Jul. 20, 1995, pp. 4284-4289, vol. 34-No. 21.
P. L. Higby et al.,Properties of barium gallium germanate glasses,Journal of Non-Crystalline Solids, 1993, pp. 303-308, vol. 163, North Holland.
J. M. Jewell et al.,Properties of BaO-R2O3-Ga2O3GeO2(R=Y, Al, La, and Gd)Glasses, Journal of the American Ceramic Society, Mar. 1994, pp. 697-700, vol. 77-No. 3.
M. Krishnan Murthy et al.,Some Physical Properties of Alkali Germanate Glasses, Nature, Jan. 18, 1964, pp. 285-286, vol. 201-No. 4916.
M. K. Murthy et al.,Properties and structure of glasses in the system M2O-Ga2O3-GeO2 (M=Li, Na, K), Physics and Chemistry of Glasses, Feb. 1, 1967, pp. 26-29, vol. 8-No. 1.
T. Sakamoto et al.,1.4-&mgr;m-Band Gain Characteristics of a Tm-Ho-Doped ZBLYAN Fiber Amplifier Pumped in the 0.8-&mgr;m Band, IEEE Photonics Technology Letters, Sep. 9, 1995, pp. 983-985, vol. 7-No. 9.
de Sandro Jean-Philippe
Dejneka Matthew J.
Mayolet Alexandre M.
Samson Bryce N.
Wang Ji
Corning Incorporated
Foley & Lardner
Sample David
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