Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2001-06-08
2003-12-09
Sample, David (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
Reexamination Certificate
active
06660672
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled, “Alkaloid Halogen-Doped Sulfide Glasses for Opitical Amplifier and Fabricating Method thereof,” filed in the Korean Industrial Property Office on Jul. 6, 2000 and there duly assigned Serial No. 2000-38691.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to sulfide glasses and a fabricating method thereof. More particularly, the present invention relates to sulfide glasses used as an optical amplifier and the fabricating method thereof.
2. Description of the Related Art
The following list of literature reference is indicative of the extensive research conducted in recent years in the field of sulfide-containing glasses.
<References>
1. “High-Gain Rare Earth Doped Fiber Amplifier Operating at 1.54 &mgr;m”, in Tech. Digest of Conference on Optical Fiber Communication, Reno Nevada (Optical Society of America. Washington, D.C.), W12, 167 (1987) by R. J. Mears, L. Leekie, I. M. Jauncey, and D. N. Payne.
2. “Amplification and Lasing at 1350 nm in Neodymium Doped Fluorozirconate Fiber”, Electron. Lett. 24, 438 (1988) by M. C. Brierley and C. A. Millar.
3. “Pr
3+
—doped Fluoride Fibre Amplifier Operating at 1.31 &mgr;m”, Opt. Lett. 16, 1747 (1991) by Y. Ohoshi, T. Kanamori, T. Kitagawa, S. Takahashi, E. Snitzer, and G. H. Sigel, Jr.
4. “Amplification at 1.3 &mgr;m in a Pr
3+
—Doped Single Mode Fluorozirconate Fibre”, Electronics Letters vol. 27, no. 8, 628 (1991) by S. F. Carter, D. Szebesta, S. T. Davey, R. Wyatt, M. C. Brierley, and P. W. France.
5. “Pr
3+
: La—Ga—S Glass: A Promising Material for 1.3 &mgr;m Fiber Amplification”, in Tech. Digest of Topical Meeting Optical Amplifiers and their Applications. PDP5 (1992) by P. C. Becker, M. M. Broer, V. C. Lambrecht, A. J. Bruce, and C. Nykolak.
6. “Pr
3+
—Doped Ge—Ga—S Glasses for 1.3 &mgr;m Optical Fiber Amplifiers”, J. Non-Cryst. Solids, 182, 257 (1995) by K. Wei, D. P. Macherwirth, J. Wenzel, E. Snitzer, and G. H. Sigel, Jr.
7. Spectroscopy and Quantum Efficiency of Halide-Modified Gallium-Lanthanium Sulfide Glasses Doped with Praseodymium”, J. Non-Cryst. Solids, 239, 176 (1998) by J. R. Hector, J. Wang, D. Brady, M. Kluth, D. W. Hewak, W. S. Brocklesby, and D. N. Payne.
In general, an optical communication system operates at the zero dispersion wavelength band, 1.31 &mgr;m, and a minimum loss wavelength band, 1.5 &mgr;m of silica glass, as an optical wave-guide material [See reference 1]. Particularly in the 1.31 &mgr;m wavelength band, the rare-earth ions of Nd
3+
, Dy
3+
, and Pr
3+
exhibit fluorescence transition. Efforts have been made toward utilization of these rare-earth ions.
With reference to Nd
3+
, the central wavelength of fluorescence resulting from transition from the energy level of
4
F
3/2
to
4
F
13/2
is 1.35 &mgr;m, which is different from the zero dispersion wavelength band of silica glass. Moreover, the probability of fluorescence emission at 1.31 &mgr;m is only one fifth of the fluorescence emission probability at 0.89 &mgr;m and 1.064 &mgr;m that are simultaneously generated at
4
F
3/2
. The gain at 1.31 &mgr;m drops due to a strong, excited state absorption [See reference 2].
Dy
3+
produces fluorescence at 1.31 &mgr;m across an induced emission area that is four times larger than Pr
3+
, and has a high branching ratio relative to other rare-earth elements. Despite these advantages, Dy
3+
has a very narrow energy difference, about 1800 cm
−1
between the fluorescence levels of 1.31 &mgr;m,
4
F
11/2
or
6
H
9/2
, and the nearest lower energy level
6
H
11/2
s. Here, the resulting multiphonon relaxation leads to energy loss. Consequently, Dy
3+
has only 10% of the fluorescence lifetime of Pr
3+,
which are low fluorescence efficiency and a low gain coefficient needed for light amplification.
While Pr
3+
induces fluorescence at 1.31 &mgr;m utilizing transition
1
G
4
to
3
H
5
and has a much higher 1.31 &mgr;m fluorescence transition probability than other fluorescence transition probabilities, it also has a narrow energy difference, 3000 cm
−1
between
1
G
4
and
3
F
4
. Thus, when an oxide glass having a phonon energy of 800 cm
−1
or above is used as a base material, it is highly probable that the energy of Pr
3+
ions excited to
1
G
4
experiences radiation-less transition due to the multiphonon relaxation, which results in the decrease of optical amplification efficiency. To solve the problem, a fluoride glass or a sulfide glass that has low phonon energy was suggested as a base material. However, the use of the fluoride glass as a base material can not produce high optical amplification efficiency because its quantum efficiency is very low, 4%. The sulfide glass as a base material is not effective in achieving high optical amplification efficiency due to its short fluorescence lifetime, 300 &mgr;s at
1
G
4
[See references 3 to 7].
FIG. 1
illustrates the multiphonon relaxation of Pr
3+
between energy levels, and the energy transfer between Pr
3+
ion. The 1.31 &mgr;m fluorescence lifetime and the optical amplification efficiency of Pr
3+
at
1
G
4
are much influenced by radiation-less transition in which energy excited to
1
G
4
is consumed in a form other than light. The radiation-less transition refers to the multiphonon relaxation of phonon energy, as indicated reference character a, and the energy transfer between adjacent Pr
3+
ions, as indicated by reference character b in FIG.
1
. The multiphonon relaxation is a dominant factor that decreases the optical amplification efficiency.
SUMMARY OF THE INVENTION
The present invention provides alkali halide-doped sulfide glasses to be used as an optical amplifier and its fabricating method to extend fluorescence lifetime by eliminating the multiphonon relaxation, thus increasing the optical amplification efficiency of the optical amplifier.
The present invention can be achieved by providing alkali halide-doped sulfide glasses for an optical amplifier and a fabricating method thereof. An alkaloid halogen-doped sulfide glass is formed of silica doped with a Ge—Ga—S three-component system, Pr
3+
, and an alkali halide. To fabricate alkali halide-doped sulfide glass for an optical amplifier, silica doped with Ge, Ga, S, Pr
3+
, and an alkali halide as a starting material is filled into a container. The container is sealed in a vacuum and the starting material in the container is fused by heating the container. The container is cooled and the starting material is sintered by heating the container at a glass transition temperature.
According to one aspect of the present invention, the Pr
3+
and alkali halide-doped sulfide comprises a mixture of GeGaS and CsBr, expressed in terms of mole percent on the sulfide basis, and is selected from the group consisting of 90-92% (Ge
0.25
Ga
0.10
S
0.65
) and 8-10% (CsBr); 94.5-96.0% (Ge
0.29
Ga
0.05
S
0.66
) and 4-5.5% (CsBr); and, 84.2-85.25% (Ge
0.18
Ga
0.18
S
0.64
) and 14.75-15.75% (CsBr).
According to another aspect of the invention, the Pr
3+
and alkali halide-doped sulfide glass comprises a mixture of GeGaS and KBr, expressed in terms of mole percent on the sulfide basis, and comprises 90.91% (Ge
0.25
Ga
0.10
S
0.65
) and 9.09% (KBr).
According to a further aspect of the invention, the Pr
3+
and alkali halide-doped sulfide glass comprises a mixture of GeAsGaS and CsBr, expressed in terms of mole percent on the sulfide basis, and comprises 98% (Ge
0.30
As
0.06
Ga
0.028
S
0.62
) and 2%(CsBr).
Preferably, the alkali halide-doped is CsBr or Kbr.
REFERENCES:
patent: 5379149 (1995-01-01), Snitzer et al.
patent: 5389854 (1995-02-01), True
patent: 5392376 (1995-02-01), Aitken et al.
patent: 6148125 (2000-11-01), Heo et al.
patent: 6347177 (2002-02-01), Heo et al.
patent: 1022823 (2000-07-01), None
patent: 2342771 (2000-04-01), None
patent: 2000
Heo Jong
Jung Sun-Tae
Lee Dong-Chin
Lee Hye-Sun
Cha & Reiter
Sample David
Samsung Electronics Co LTD
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