Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2002-03-11
2003-09-02
Ngo, Hung V. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C174S050510, C257S433000, C257S788000
Reexamination Certificate
active
06613980
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an environrimental protection apparatus for an optical assembly of a type that uses bulk optics in an optical path. The present invention also relates to a method of manufacturing an environmental protection apparatus for an optical assembly.
DISCUSSION OF THE BACKGROUND ART
It is well known that both the operational efficiency and the working lifetime of an optical assembly are dependent upon the environmental conditions within which the optical assembly operates. Contaminants such as non-inert gases or moisture that come into contact with parts of the optical assembly can cause degradation and/or irreparable damage of the parts of the optical assembly.
FIG. 1
is a schematic diagram of a known package used in the art to provide environmental protection for an optical assembly. The optical assembly is substantially hermetically sealed within a housing
10
by a lid
8
to create a substantially hermetically sealed package containing a controlled gas environment
11
therein. The optical assembly comprises a bulk optical component
12
formed from a polymer such as polycarbonate and through which electromagnetic radiation
13
, typically light, can propagate. The bulk optical component
12
comprises a reflecting surface
14
(by virtue of total internal reflection) which is substantially planar in shape and a lens portion
16
. The optical assembly also comprises an optoelectronic device
18
disposed adjacent and beneath the lens portion
16
of the bulk optical component
12
.
In operation, electromagnetic radiation
13
is divergent on leaving an optical fibre (not shown) and when entering the bulk optical component
12
. The electromagnetic radiation
13
is incident upon the reflecting surface
14
and, via total internal reflection of the electromagnetic radiation
13
, the electromagnetic radiation
13
is reflected to the lens portion
16
. The lens portion
16
focuses the electromagnetic radiation
13
onto the optoelectronic device
18
.
Although a near contaminant free, controlled, gas environment
11
can be achieved by the near-hermetic seal between the lid
8
and the housing
10
, some ingress of contaminants and moisture into the sealed package will occur as the seal is not perfect. Similarly, if the near-hermetic seal between the lid
8
and the housing
10
fails, ingress of non-inert gases and moisture into the housing will occur, thereby contaminating the controlled gas environment
11
of the package. Consequently, over time, the performance of the optical assembly degrades and the bulk optical component
12
and the optoelectronic device
18
become damaged due to the ingress of contaminants. Furthermore, production of the near-hermetically sealed package having the controlled gas environment
11
is costly and time consuming. Also, the location of the optoelectronic device
18
beneath the lens portion
16
of the bulk optical component
12
makes visual alignment of the optoelectronic device
18
with the bulk optical component
12
, so that the electromagnetic radiation
13
is incident upon the optoelectronic device
18
, very difficult due to the bulk optical component
12
obscuring the view of the optoelectronic device
18
. The difficulty in visual alignment of the bulk optical component
12
with the optoelectronic device
18
increases the time and costs associated with the production of the packaged optical assembly.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a package for an optical assembly comprising an optoelectronic device, characterised in that the bulk optical component and the optoelectronic device are enveloped by an encapsulant material having a substantially same refractive index as the bulk optical component, the bulk optical component having a reflective surface to, when in use, reflectively direct electromagnetic radiation incident thereupon to the optoelectronic device.
Preferably, the encapsulant material is silicone.
Preferably, the reflective surface is curved so as to focus the electromagnetic radiation. More preferably, the reflective surface is metallised.
According to the present invention, there is also provided a method of forming a package for an optical assembly, the method comprising the steps of: disposing an optoelectronic device on a substrate; aligning the bulk optical component with respect to the optoelectronic device, the optoelectronic device not being obscured by the bulk optical component during the alignment of the bulk optical component with the optoelectronic device; enveloping the bulk optical component and the optoelectronic device with an encapsulant material; and depositing a protective layer over the encapsulant material.
It is thus possible to provide a packaged optical assembly with effective environmental protection of the parts of the optical assembly by the envelopment of the optical assembly with silicone. Furthermore, visual alignment of the optoelectronic device with the bulk optical component, so that the electromagnetic radiation is incident upon the optoelectronic device, is simplified due to the position of the optoelectronic device relative to the bulk optical component being such that the view of the optoelectronic device is not obscured during alignment. The visual alignment of the optoelectronic device with the bulk optical component can be performed in a gaseous environment prior to envelopment of the optical assembly with silicone because electromagnetic radiation exiting the bulk optical component does so substantially normal to the surface of the bulk optical component.
REFERENCES:
patent: 6246123 (2001-06-01), Landers, Jr. et al.
patent: 2001/0035573 (2001-11-01), Weigert
Keeble Daniel John
Lemoff Brian
McGhee Andrew
Pozzi Fabio
Agilent Technologie,s Inc.
Ngo Hung V.
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