Optical waveguides – Integrated optical circuit
Reexamination Certificate
1998-12-29
2002-05-07
Font, Frank G. (Department: 2877)
Optical waveguides
Integrated optical circuit
Reexamination Certificate
active
06385359
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to packaging integrated circuits, and more particularly to a submountless integrated optics chip package and method of packaging for use in a fiber optic gyroscope. The government of the United States of America may have rights to this invention.
BACKGROUND OF THE INVENTION
A gyroscope is an instrument commonly used in navigation systems of transportation vehicles, satellites, and communications systems to sense motion with respect to a known starting point by measuring rotation about an axis. Mechanical gyroscope designs implementing spinning flywheels suspended in gimbals are being replaced in modern designs by optical gyroscopes, which have light waves circulating around a closed path. One type of optical gyroscope, the fiber optic gyroscope, typically utilizes an Integrated Optic Chip (IOC) made of lithium niobate (LiNbO
3
) to split and modulate the laser light. The IOC may comprise other materials such as silicon, for example, and are typically housed in a package before being assembled into a gyroscope or other device.
Several design aspects must be considered in order to preserve the physical integrity of the Integrated Optic Chip (IOC), as well as its performance characteristics, when packaging the IOC. First, the IOC itself must experience minimal strain during temperature cycling and vibration. Second, the interface for the optic fiber attached (pigtailed) to the chip must also experience minimal strain. Third, the electrical connections that are wire bonded must be held rigid, either permanently or temporarily, to accommodate the wire bonding process. It is also desirable that an IOC package and method of packaging have a low cost and ease of assembly.
SUMMARY OF THE INVENTION
The present invention achieves technical advantages as a submountless IOC package and further including a method of packaging an IOC, by attaching an IOC to the package base with a dielectric gel. The components of a submount and strain relief blocks, and several processing steps of prior art packages are eliminated with the present invention, resulting in time and cost savings.
In one embodiment, disclosed is an Integrated Optics Chip (IOC) package for an IOC, including a base having an upper support surface with a first raised surface. A dielectric gel is disposed on the first raised surface of the base. The dielectric gel is adapted to couple to the IOC, and the dielectric gel is sufficiently compliant to minimize stresses from structural changes in the base, accommodate a thermal mismatch between the IOC and the base, and reduce vibration. A first adhesive may be applied to a platform integral to the base that is sufficiently rigid to prevent the IOC from separating from the dielectric gel during vibration.
In another embodiment, disclosed is an Integrated Optics Chip (IOC) package, including a base having a mounting surface with a first raised surface. A dielectric gel is disposed on the first raised surface of the base. An IOC is coupled to the base via the dielectric gel, where the dielectric gel is sufficiently compliant to minimize stresses from structural changes in base, accommodate a thermal mismatch between IOC and base, and reduce vibration. A first adhesive may be applied to a platform integral to the base that is sufficiently rigid to prevent the IOC from separating from the dielectric gel during vibration.
Also disclosed is a method of packaging an Integrated Optics Chip (IOC), the method including the step of providing a base, where the base has an upper support surface with a first raised surface. The method also includes the step of attaching the IOC to the first raised surface of the base with a dielectric gel, where the dielectric gel is sufficiently compliant to minimize stresses from structural changes in the base, accommodate a thermal mismatch between the IOC and the base, and reduce vibration. The attaching step may further include attaching the IOC to a platform of the base via a first adhesive, where the first adhesive is sufficiently rigid to prevent the IOC from separating from the dielectric gel during vibration.
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patent: 4424174 (1984-01-01), Howarth
patent: 5214726 (1993-05-01), Hockaday
patent: 5479548 (1995-12-01), Cote et al.
patent: 5673345 (1997-09-01), Saito et al.
patent: 5875545 (1999-03-01), DiStefano et al.
Craig T. Herdman,Fiber-Optic Gyroscopes; Scientific Honeyweller; 1996 pp. 1-10.
UTP Catalog “Fiber Optic Gyro Circuits” pp. 21-22, 26.
Fetting Karl A.
Hung Henry H.
Shannon John H.
Vaught Jesse A.
Font Frank G.
Honeywell International , Inc.
Mooney Michael P.
Shudy John G.
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