Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-07-31
2002-09-24
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S147000
Reexamination Certificate
active
06456761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to electronic assemblies, and, in particular, to a micro-fixtured lensed assembly for optoelectronic devices and optical fibers.
2. Description of Related Art
Optoelectronics and fiber optic communications are commonly used in communications and electronic devices. The use of optical fibers for telephonic and other information transfer is desirable because of the high bandwidth and high data rates possible with fiber optic lines. The electronics that transmit and receive the light signals that travel on fiber optic lines have become integrated with the fiber optic lines for better signal transmission and reception.
Alignment between the individual strands of a fiber optic cable and the detectors and transmitters is crucial to a fiber optic data transmission system. There are typically two approaches to alignment of the fiber to the electronics; active approaches, where light is passed through the fiber and strikes the detector, and the detector is monitored during positioning of the fiber in relation to the detector, and passive approaches, where no light is passed through the fiber, and mechanical devices are used for alignment of the individual parts of the transmitter or receiver assembly.
Previous passive alignment approaches directly couple light between a fiber and an optoelectronic device without passing that light through a separate optical lens. As a result, divergence of the optical beam and differences in the optical-mode sizes can reduce the optical coupling efficiency.
FIG. 1
illustrates an optoelectronic transmitter assembly of the related art. As shown, assembly
100
comprises a silicon platform
102
, also called a silicon waferboard, and a laser chip
104
. Grooves
106
are etched into the silicon platform
102
for mechanically holding optical fibers against the silicon platform
102
and for aligning the optical fibers to the laser chip
104
. The grooves
106
are typically v-shaped. The silicon platform
102
also contains pedestals
108
, typically nine microns high, formed by reactive ion etching (RIE) into the top surface of the silicon. The pedestals
108
serve to position the laser chip
104
on the plane of the silicon platform
102
.
A notch
110
is etched into laser chip
104
, and the notch is placed against one pedestal
108
, while the cleaved front facet
112
is placed against two other pedestals
114
. Standoffs
116
are constructed from polyimide of a controlled thickness, typically five microns, and patterned by RIE. The standoffs
116
determine the vertical position of the laser chip
104
which is mounted with the laser devices down, facing the silicon platform
102
.
FIGS. 2A-2B
illustrate another device of the related art. The device
200
of
FIGS. 2A-2B
illustrate a silicon platform
202
with a photodetector array
204
where the photodetector array
204
is mounted with the photodetectors facing away from the silicon platform
202
. Grooves
206
and ribbon support
208
are etched into the silicon platform
202
to mechanically support the fiber optic cables and the individual optical fibers. As described with respect to
FIG. 1
, the photodetector array
204
is positioned and aligned by pressing the photodetector array
204
against pedestals
210
that have been etched into the surface of silicon platform
202
. However, the photodetector size must be larger than necessary to accommodate the alignment tolerances, inaccuracies in dicing and/or cleaving of the photodetector array
204
, and divergence of the light beam before it reaches the photodetector array
204
, thus limiting the bandwidth of the output.
FIG. 2B
illustrates the light path
212
of the device illustrated in FIG.
2
A. Grooves
206
are typically v-shaped, and terminate in reflective mirror surfaces
214
that redirect the light from an optical fiber out of the plane of the silicon platform
202
and onto the backside of the photodetector array
204
. Wire bonds
216
carry the signals generated by photodetector array
204
to other circuitry.
FIG. 3
illustrates a laser array of the related art. Device
300
again has a silicon platform
302
and laser array chip
304
mounted to silicon platform
302
. Laser array chip
304
is an edge emitting laser array, and the optical fibers
306
are guided through a structure
308
in silicon platform
302
to in-plane optical elements
310
formed directly on the silicon platform
302
. The tapered waveguides
312
transform the small diameter of the optical mode in the edge-emitting laser
304
to the larger diameter of the optical mode in the optical fiber
306
. The tapered waveguides
312
are formed from the thin films of silica deposited on the silicon platform
302
surface. The optical fibers
306
are held in v-grooves etched in the silicon platform
302
. Since both the tapered waveguides
312
and the v-grooves are fabricated directly on the silicon platform
302
, their relative positions can be controlled precisely. The laser chip is mounted onto the silicon platform
302
by means of solder bumps
314
and standoffs
316
, which also align the chip on the silicon platform
302
. However, this approach suffers from having the optical elements formed as an integral part of the silicon platform
302
, thereby reducing the types of optical elements that can be used in the assembly
300
.
There is therefore a need in the art for an apparatus and method for aligning optical fibers to optoelectronic devices. There is also a need in the art for a method of aligning optical fibers to optoelectronic devices that reduces manufacturing time and costs. There is also a need in the art for a method of aligning optical fibers to optoelectronic devices that maximizes the throughput of the optical fiber.
SUMMARY OF THE INVETION
The present invention discloses a method and apparatus for aligning an optical fiber to an optoelectronic element. The apparatus comprises a base and a lens. The base is fabricated from a first crystallographic orientation, and includes an alignment feature for an optical fiber. The lens is fabricated from a second crystallographic orientation, and is aligned with the base using a second alignment feature associated with the first and second crystallographic orientations.
A method in accordance with the present invention comprises the steps of coupling an optoelectronic element to a base comprising a material having a first crystallographic orientation, coupling a lens to the base, the lens comprising a material having a second crystallographic orientation, wherein the lens is aligned to the base using the first crystallographic orientation and the second crystallographic orientation, and attaching an optical fiber to the base, wherein the optical fiber is placed proximate to the lens, such that a light path of the optical fiber is aligned with the optoelectronic element through the lens.
An optoelectronic assembly in accordance with the present invention comprises an optoelectronic element, a lens assembly, and a base. The optoelectronic element converts between an optical signal and an electrical signal. The lens assembly comprises a first material having a first crystallographic orientation and includes a first alignment feature. The base comprises a second material having a second crystallographic orientation and includes a second alignment feature. The lens assembly and base are aligned using the first alignment feature and the second alignment feature, the first alignment feature aligns the lens assembly to the optoelectronic element, and the second alignment feature aligns an optical fiber to the lens assembly.
The present invention provides an apparatus and method for aligning optical fibers to optoelectronic devices. The present invention also provides a method of aligning optical fibers to optoelectronic devices that reduces manufacturing time and costs. Further, the present invention provides a method of aligning optical fibers to optoelectronic devices that maximizes the throughput of the
Au Anson
Yap Daniel
Duraiswamy V. D.
Hughes Electronics Corporation
Sales M. W.
Ullah Akm E.
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