Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1998-10-29
2001-04-03
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298150, C204S192120, C204S192110, C204S192340, C118S728000, C118S500000, C216S066000, C216S067000
Reexamination Certificate
active
06210546
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical components, and, in particular, to the manufacture of optical components used in laser-based optical communication systems.
2. Description of the Related Art
In a laser-based optical communication system, light is transmitted from a laser source (which converts electrical signals into optical signals) to an optical receiver (which converts the optical signals back into electrical signals) over optical fibers and through various types of optical components that modulate, filter, route, amplify, or otherwise process the optical signals. Two or more optical components may be aligned and mounted onto a substrate for an encapsulated laser package to be used in an optical communication system. One such component is an optical semi-isolator, which may be used in conjunction with an optical analyzer to form an optical isolator. Optical semi-isolators are described in more detail in U.S. Pat. No. 5,737,349.
FIG. 1
shows a cross-sectional view of a typical optical semi-isolator
100
. Semi-isolator
100
is formed from two parts: a polarizer
102
and a rotator
104
, each of which has an optical element mounted
20
within a frame. In particular, polarizer
102
comprises glass element
106
having an anti-reflection coating and mounted within frame
108
, while rotator
104
comprises garnet element
110
having an anti-reflection coating and mounted within frame
112
. Frames
108
and
112
are typically gold-coated metal structures. For example, in one implementation, frames
108
and
112
are iron-nickel (Fe—Ni) structures coated with nickel/gold (Ni/Au) plating
114
.
Fabrication of semi-isolator
100
involves the following steps:
(1) Apply anti-reflection coatings to glass element
106
and garnet element
110
;
(2) Insert glass element
106
into frame
108
and insert garnet element
110
into frame
112
;
(3) Solder elements
106
and
110
within frames
108
and
112
, respectively, using solder glass
116
at about 500° C. in air to form polarizer
102
and rotator
104
; and
(4) Laser weld (
118
) frame
108
of polarizer
102
to frame
112
of rotator
104
to form semi-isolator
100
.
Semi-isolator
100
may then be mounted onto a substrate to form one component of a laser package for use in an optical communication system. In particular, components like semi-isolator
100
are often auto-bonded to a ceramic substrate using a tin-lead (Sn-Pb) solder without using any flux. The ability to mount optical components like semi-isolators onto substrates without using any flux is important in applications where flux would adversely affect the operational characteristics of the optical elements (e.g., contaminate or otherwise interact with the surfaces of the optical elements).
Unfortunately, however, it has been found that optical components, such as semi-isolator
100
of
FIG. 1
, that are fabricated using a process similar to the one outlined above, cannot be mounted onto ceramic substrates with sufficient reliability using flux-less auto-bonding techniques. The strength of such bonding is often too low to withstand normal operational conditions (e.g., vibrations and temperature variations). As a result, an unacceptably high percentage of such optical components come loose from their substrates, thereby destroying the desired functionality of those laser packages.
SUMMARY OF THE INVENTION
The present invention is directed to a technique for manufacturing optical components, such as optical semi-isolator
100
of
FIG. 1
, such that the resulting optical components can be reliably mounted onto substrates using flux-less auto-bonding. According to the technique of the present invention, one or more optical components arc placed within a special fixture that allows certain portions of the optical components (e.g., surface
120
of semi-isolator
100
of
FIG. 1
) to be exposed to a plasma or ion beam directed at the components, while shielding other, sensitive portions of the optical components (e.g., the optical elements
106
and
110
of
FIG. 1
) from such exposure.
In one embodiment, the present invention is a fixture used in fabricating an optical component having at least one optical element and a mounting surface. The fixture comprises one or more troughs defined on a first side of the fixture, each trough adapted to receive one or more optical components. Each trough has opposing shelves adapted to support the one or more optical components. The shelves define an aperture in the trough such that, when the optical component is placed within a trough, at least a portion of the mounting surface of the optical component will be exposed when a plasma or ion beam is directed at the optical component from a second side of the fixture, while the shelves shield the optical element in the optical component from direct exposure to the plasma or ion beam.
In another embodiment, the present invention is a method for fabricating an optical component having at least one optical element and a mounting surface, comprising the steps of (a) placing the optical component within a fixture comprising one or more troughs defined on a first side of the fixture, each trough adapted to receive one or more optical components, each trough having opposing shelves adapted to support the one or more optical components, the shelves defining an aperture in the trough; and (b) directing a plasma or ion beam at a second side of the fixture, wherein the aperture in the trough exposes at least a portion of the mounting surface of the optical component to the plasma or ion beam and the shelves shield the optical element in the optical component from direct exposure to the plasma or ion beam.
REFERENCES:
patent: 2391595 (1945-12-01), Richards et al.
patent: 2398382 (1946-04-01), Lyon
patent: 3653900 (1972-04-01), Black
patent: 3708418 (1973-01-01), Quinn
patent: 3998718 (1976-12-01), Melliar-Smith
patent: 4126530 (1978-11-01), Thornton
patent: 4245768 (1981-01-01), Sater
patent: 4278493 (1981-07-01), Petvai
patent: 5090609 (1992-02-01), Nakao et al.
patent: 5376180 (1994-12-01), Maher
patent: 5380551 (1995-01-01), Blonder et al.
patent: 5737349 (1998-04-01), Gaebe
patent: 6017581 (2000-01-01), Hooker et al.
Coult David G.
Derkits, Jr. Gustav E.
Shakespeare Walter J.
Wendling Duane D.
Yeagle Frederick A.
Cantelmo Gregg
Lucent Technologies - Inc.
Mendelsohn Steve
Nguyen Nam
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