Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – Process of manufacturing optical fibers – waveguides – or...
Reexamination Certificate
2000-07-31
2003-05-27
Hoffman, John (Department: 1731)
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
Process of manufacturing optical fibers, waveguides, or...
C065S391000, C065S033100, C385S130000, C385S002000, C385S141000, C501S010000, C501S041000, C501S135000, C501S137000, C501S037000
Reexamination Certificate
active
06568219
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electro-optic devices and to methods for their manufacture.
BACKGROUND OF THE INVENTION
Electro-optic devices, e.g. modulators, are essential components of most lightwave systems. Typically, these devices use lithium niobate as the active electro-optic material. In state of the art commercial systems, electro-optic devices are digital and operate with data transmission rates up to 10 Gbits. Systems under development reach data rates of 40 Gbits and higher.
Lithium niobate is widely used in electro-optic applications largely because techniques have been developed for making large crystals of this material. Other ceramic ferroelectric materials, such as barium titanate and strontium barium niobate, have potentially superior ferroelectric properties but these materials are difficult to produce in large, optical quality, crystals. Moreover, in single crystal form, these alternative materials exhibit undesirable photorefractive properties.
Thus commercial electro-optics devices continue to be made using bulk crystals of lithium niobate. However, bulk devices are expensive to manufacture, especially with very small dimensions, are difficult to integrate, and typically operate with relatively high drive voltages. High drive voltages currently limit practical implementation of ultra high bit rate modulators. New device designs, with lower manufacturing cost and reduced drive voltages, are critical to the continued development and large-scale commercial application of these modulators. Especially attractive from these standpoints, are devices made in thin film form. However, to date, the availability of efficient ferroelectric materials that can be fabricated using thin film techniques is limited.
New ferroelectric materials that meet these needs would constitute a significant advance in the technology.
Attempts have been made recently to develop new material systems called ceram-glass. In these materials a glass is used as a host for a ferroelectric ceramic. If the ferroelectric component of the material system is be made with small enough crystal grain size, a transparent body can result. However, engineering such a system is complicated by the fact that most ceramics form multiple phases, and creating a uniform, stable and reproducible phase with the right ferroelectric properties is elusive. Moreover, the optical properties of the host material, especially the refractive index, must match those of the ferroelectric phase. From a practical standpoint this eliminates the silica glasses from consideration.
Due to the foregoing difficulties, the development of new ceram-glass materials has met with limited success.
STATEMENT OF THE INVENTION
We have developed new ferroelectric ceram-glass materials that can be produced using thin film technology, and also show promise for bulk glass applications, especially optical fibers. The new materials comprise strontium barium niobate (SBN) in a host glass comprising tellurium dioxide. When properly processed, these material can be made highly transparent. Importantly, the ferroelectric phase in this system is thermodynamically favored, since the strontium-barium-niobium constituents prefer to form as oxides rather than tellurides. It has been demonstrated that, with proper processing, the ferroelectric constituents precipitate out as oxides with a very fine grain structure. These materials can be sputtered conveniently to form thin film devices, and can also be made in bulk form for other applications, notably, optical fibers.
The ceram-glass compositions useful for the invention can be expressed as:
{SrO
(y)
(BaO
(1−y)
(Nb
2
O
5
)
2
}
(1−x)
(TeO
2
)
(x)
where y=0.5-0.8, and x=0.4-0.9.
REFERENCES:
patent: 3877953 (1975-04-01), Broemer et al.
patent: 4732875 (1988-03-01), Sagara
patent: 5116786 (1992-05-01), Matsuura
patent: 5749932 (1998-05-01), Lamar et al.
patent: 5786659 (1998-07-01), Takagi et al.
patent: 5831387 (1998-11-01), Kaneko et al.
patent: 2002/0092356 (2002-07-01), Yamamoto et al.
Sabadel et al, Structural and Nonlinear Optical Characterizations of TelluriumOxide based glasses, Journal of SOlid State Chemistry, 132(2): 411-419—1997.
Glass Alastair Malcolm
Greene Benjamin Irvin
Kopylov Nonna
Kortan Ahmet Refik
Hoffman John
Lucent Technologies - Inc.
Wilde Peter V. D.
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