Optical lenses

Details Optical lenses Optical lenses

2002-11-12

2004-10-19

Sanghavi, Hemang (Department: 2874)

Optical waveguides

With optical coupler

Input/output coupler

C385S093000

Reexamination Certificate

active

06807336

ABSTRACT:

FIELD OF THE INVENTION
The present invention lies in the field of micro-optical lenses as used in fiber optic data communication systems, whether singles or arrays, and particularly relates to inexpensive lenses that launch laser light into high-bandwidth optical fibers while reducing or eliminating feedback to the lasers.
BACKGROUND OF THE INVENTION
A typical known arrangement is shown in
FIG. 1
, wherein an optical lens
10
is interposed between a laser (i.e. coherent) light source
15
and the front-end of an optical fiber
20
. The laser source
15
is mounted on for instance from a transistor outline (TO) header or a circuit board or
12
that covers the open end of a cavity
14
. The lens
10
has an object (or input) surface
25
and an image (or output) surface
30
. The lens
10
is held in optical alignment with the laser source
15
by a transistor outline (TO) can or a molding
16
.
FIG. 1
shows, by ray tracing, the typical path of light from the laser source
15
into the front-end
22
of the fiber
20
. The optical fiber
20
also has a back-end
24
that connects with a receiver device
35
.
There are a number of antagonistic design considerations relating to such lenses. This includes the situation that the volume of space within a package containing the laser, lens and fiber end is very small. Typically there is only 300 &mgr;m between the laser light source and the input surface of the lens in parallel optical channel applications. This places restrictions upon the lens design. Furthermore, such lens coupling units are often manufactured in an array (typically 12×1). The most significant objective in the design of such lenses is the avoidance of back reflections. Referring again to
FIG. 1
, conventional fiber surface
22
partially reflects the input laser light, which will then interfere with the source light
15
(and thus the data represented by the modulated light source) resulting in data errors at the far-end of the optical fiber. It is also possible for partial reflection to occur at the output surface
24
, to be propagated back towards the laser light source
15
again leading to data corruption. A further requirement is that lens launches the laser light in the fiber while avoiding the refractive index anomalies in the fiber center as well as those at the core-cladding interface thus improving the bandwidth of the data communication.
One example in the prior art of an approach to the problem of partial reflections is described in British Patent Publication No. GB 2 354 839 A (Agilent Technologies Inc). This prior art document describes the toroidal lens surfaces as replacement for earlier hyperbolic transfer lenses.
It is further known to use sub-micron diffraction patterns (eg small ridges as a lens surface in an effort to reduce back reflections. These lens surfaces are produced by use of expensive sub-micron wafer technologies and these lenses attenuate the laser beam.
It is generally desirable to be able to injection mold micro lenses since that fabrication process is well suited for manufacturing at high volumes and low cost. The lenses are required to retain their shape at temperatures of 200° C. or above since laser transmitter/transceiver modules are exposed to high temperatures during their placement on PCB boards by a solder re-flow process or a solder bath. For this reason, only polymers with high glass transition temperatures can be used. However, the use of these types of polymer prevents the application of diffractive surfaces. Besides polymers, certain glass types can also be utilized, however this will significantly raise the price of the lens or lens array.
SUMMARY OF THE INVENTION
An optical lens that has at least one end surface of a surface shape that is the combination of a conic component, a spiral component and a cone component.
The lens can be arranged as an array. The lens or lens array can be integrated with a housing that has one end coupling for coupling to a laser source or laser sources and a further end for coupling to a free end of an optical fiber or fibers.
A method of fabricating the said optical lens involves forming a mold having the negative shape of the lens, including a mold portion corresponding to an end surface of the lens. The mold portion is the negative of the combination of a conic component, a spiral component and a cone component. The lens is produced by a flowable material applied to the mold.


REFERENCES:
patent: 4961622 (1990-10-01), Gorman et al.
patent: 6530697 (2003-03-01), Johnson et al.
patent: 2002/0075911 (2002-06-01), Cham et al.
patent: 2354839 (2001-04-01), None
patent: 2370653 (2002-07-01), None
patent: WO 01/67566 (2001-09-01), None
patent: WO 200205004 (2002-01-01), None

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