Optical waveguides – Having particular optical characteristic modifying chemical... – Of waveguide core
Reexamination Certificate
2000-11-03
2003-01-28
Lee, John D. (Department: 2874)
Optical waveguides
Having particular optical characteristic modifying chemical...
Of waveguide core
C385S123000, C385S129000, C501S064000, C501S065000, C501S095100, C501S123000, C501S126000
Reexamination Certificate
active
06512879
ABSTRACT:
The invention relates to a glass composition that is particularly suitable in optical devices, and more specifically, the invention relates to a phosphate-free. erbium/ytterbium co-doped borosilicate glass suitable in lasers and optical signal amplifiers. for example, bulk, planar waveguiding and fiber types. The invention relates also to said optical devices based on said glass composition.
The present invention relates to a glass composition which is particularly useful in the production and the functioning of optical devices which are capable of amplifying an optical signal. These types of device include, but are not limited to bulk glass lasers. planar lasers, planar waveguide optical amplifiers, and fiber lasers and amplifiers. The description of the invention which follows, relative to optical devices composed of the glass composition of the invention, is limited to planar optical amplifiers for convenience; however, those skilled in the art will appreciate the applicability of the glass composition of the invention to other types of optical devices mentioned above.
Moreover, waveguide fabrication techniques such as ion-exchange, sputtering, flame hydrolysis and chemical vapour deposition are well reported in the literature and need not be discussed herein for an understanding of the invention by one skilled in the art. U.S. Pat. No. 5,128,801 (Jansen et al.), e.g., incorporated herein by reference, describes a planar amplifier with a waveguide path integrated into a glass body. The glass body is doped with an optically active material such as a rare earth metal oxide. The signal to be amplified is transmitted through the waveguide; the pump power is coupled into the waveguide at one end, and an amplified signal is extracted from the waveguide at the other end of the waveguide. Erbium is a preferred optically active dopant for optical signal amplifying devices since, amongst other reasons, it has a fluorescence spectrum that conveniently encompasses the low loss 1550 nm third telecommunications window, and exhibits a long excited state lifetime in a glass host.
An ideal optical amplifying device will have short length, a high amplifier efficiency (dB/mW
PUMP
), and a large gain coefficient (dB/cm). One limiting factor to the performance of erbium doped amplifiers is the glass host, the composition of which affects the excited state lifetime of the Er
3+
ions, the absorption and emission cross sections of the Er
3+
ions, and their bandwidth. In addition, the concentration of erbium in the host glass will significantly affect amplifier performance. For example, even at concentrations as low as 100 ppm in an erbium doped silica fiber, a phenomenon referred to as energy transfer up conversion can effectively quench the population inversion due to the clustering of Er
3+
ions and the resulting energy transfer between these clustered regions. While the effects of energy transfer up conversion can be greatly reduced by lowering the erbium concentration and increasing the length of the amplifier, this is in contrast to the desired amplifier characteristics mentioned above. For instance, it has been reported by Nykolak et al., “System evaluation of an Er
3+
-doped planar waveguide amplifier”,
IEEE Photon. Technol. Lett.,
5, pp. 1185-1187, (1993), that Er
3+
concentrations as high as 10,000 ppm in a 4.5 cm planar waveguide amplifier produced only 15 dB gain for 280 mW of 980 nm pump power. Moreover, in a 4 cm T1
+
ion-exchanged waveguide amplifier comprising Corning B1664 borosilicate host glass doped with 0.5% by weight of Er
2
O
3
and pumped with 110 mW of 973 nm pump power, we observed an optimum performance of 3 dB net gain.
Accordingly, there is a recognized need for a glass composition suitable for use in making an optical amplifying device of the types described herein, that avoids the known disadvantages of phosphate glasses along with the other concerns such as those mentioned above and appreciated by those skilled in the glass and optical device arts, and that provides the spectroscopic and manufacturing advantages associated with phosphate containing glasses without the known disadvantages of phosphosilicate glass compositions.
Additional features and advantages of the invention will be set forth in the description which follows, and/or in part will be apparent from the description, and/or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus and compositions thereof as particularly pointed out in the written description and claims hereof as well as the appended drawings.
The present invention has therefore for first subject a phosphate-free, Er/Yb co-doped borosilicate glass composition, the glass composition comprising:
for 100 parts by weight made up of:
60 to 70 parts by weight of SiO
2
or SiO
2
+GeO
2
with SiO
2
always representing more than 40 parts by weight, (preferably 65 to 68 parts by weight of SiO
2
or SiO
2
+GeO
2
),
8 to 12 parts by weight of B
2
O
3
(preferably 11 to 12 parts by weight of B
2
O
3
),
10 to 25 parts by weight of M
2
O wherein M
2
O is at least one alkali metal oxide selected from the group consisting of the oxides: Na
2
O intervening at 0 to 20 parts by weight, K
2
O intervening at 0 to 20 parts by weight and Li
2
O intervening at 0 to 10 parts by weight,
0 to 3 parts by weight of BaO (preferably 0 to 1 part by weight of BaO),
0.01 to 5 parts by weight of Er
2
O
3
(preferably 0.5 to 3 parts by weight of Er
2
O
3
),
from 0.1 to 12 parts by weight of Yb
2
O
3
(preferably from 1 to 10 parts by weight of Yb
2
O
3
) and from 0 to less than 5 parts by weight of F; and containing the boron atoms, of tetrahedral spatial coordination (for a concentration of B
2
O
3
of less than 12%), which is known for increasing the lifetime of the Er
3+4
I
13/2
metastable state.
The glass compositions of the invention, such as those characterized above, are original, always in keeping close to prior art borosilicate glasses, such as those referenced Corning B1664 or Schott BK-7, known to be easy to process and melt, relatively inexpensive to make, reliable, resistant to chemicals and insensitive to humidity.
The glass compositions of the invention are based on silica. Nevertheless, germanium (another element of column IV of the periodic table of the elements) can in part be substituted for silicon, for an equivalent result, which does not surprise the person skilled in the art. The intervention of germanium oxide can notably allow a slight increase in the refractive index. Said glass compositions of the invention contain:
either from 60 to 70 parts by weight of silica (SiO
2
),
or from 60 to 70 parts by weight of SiO
2
+GeO
2
, silica always representing more than 40 parts by weight of the SiO
2
+GeO
2
mixture.
The composition of the invention ensures that the boron atoms are of tetrahedral spatial coordination in order to avoid quenching of the population inversion, while the alkaline oxides, in the amounts indicated, aid glass melting and help maintaining a refractive index of about 1.5, which is essentially the same as that of silica.
Fluorine, F intervenes advantageously to improve melting and fining the glass, to modify the refractive index of said glass, and to improve the exchange properties of the ions of the composition. The intervention of said fluorine in amounts greater than those recommended (≧5 parts by weight, for 100 parts by weight of [SiO
2
+GeO
2
+B
2
O
3
+M
2
O+BaO+Er
2
O
3
]) tends to render the glass opalescent. The intervention of said fluorine generally reveals to be advantageous from 0.1 parts by weight.
The presence of ytterbium (Yb
2
O
3
) in the amounts indicated increases the the level of inversion of the Er
3+
ions for a given pump power, and Yb, besides having a strong absorption at 980 nm, ensures an efficient energy transfer to the Er
3+
ions when the concentrations of co-dopants are sufficiently high. Moreover, higher e
Beguin Alain
Camy Patrice
LaBorde Pascale
Lerminiaux Christian
Ades Patricia L.
Corning Incorporated
Lee John D.
Short Svetlana Z.
LandOfFree
Glass composition and optical device made therefrom does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Glass composition and optical device made therefrom, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Glass composition and optical device made therefrom will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3066924