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Application of Inverted Cone Shaped Structures for Accurate Alignment of Laser Diodes, Fibers and Micro Lenses

IP.com Disclosure Number: IPCOM000109236D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 4 page(s) / 171K

Publishing Venue

IBM

Related People

Benedict, M: AUTHOR [+4]

Abstract

This article describes the fabrication and application of concave cone-shaped structures which are self-aligned to the light-path of a laser diode or an optical fiber. They are used as receptacles for small lenses (spheres) or cores of single mode fibers to produce accurately aligned structures. The result is improved optical coupling at reduced cost in mass produced parts. BASIC PRINCIPLE

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Application of Inverted Cone Shaped Structures for Accurate Alignment of Laser Diodes, Fibers and Micro Lenses

       This article describes the fabrication and application of
concave cone-shaped structures which are self-aligned to the
light-path of a laser diode or an optical fiber.  They are used as
receptacles for small lenses (spheres) or cores of single mode fibers
to produce accurately aligned structures.  The result is improved
optical coupling at reduced cost in mass produced parts.
BASIC PRINCIPLE

      A thin layer 1 of photo-resist is applied to the light-emitting
surface of a laser diode 2 or an optical fiber 3 as shown in Figs.
1A and 1B.  This layer 1 is then exposed by energizing the laser
diode 2 or sending light through the optical fiber 3.  The exposed
volume of the photo-resist has the shape of an oval cone 4 according
to the intensity profile of the light beam.  The next step is to
develop the exposed material to end up with a funnel-like cavity.  A
flexible core of a single mode fiber (tapered or fire polished) or a
glass sphere inserted into this cavity will be accurately aligned
with the emitted light.  The requirement is that the photo-resist is
sensitive to the wavelength of the particular application at least in
the case of the laser 2.  The technique can also be applied on a
layer 5 of photo-resist supported by a mechanical structure 6 placed
in close proximity to a laser diode or a fiber 7, as illustrated in
Fig. 2, the mechanical structure 6 being fixed at the fiber support
8.
FABRICATION OF CONES ON CLEAVED LASER FACETS AND ON FIBERS (Figs. 1A,
1B)

      Application of the photo-resist or other suitable resin can be
done by a squirting mechanism such as used in ink-jet printers or by
a miniature syringe.  The size and shape of the small volume of
resist after placement onto the laser 2 or the fiber 3 can be
influenced by viscosity and surface tension of the fluid and the
orientation of the structure during drying.  The sequence of the
application on laser diodes 2 or fibers 3 starts by determining the
location of the light exit area in a packaged structure within a few
micrometers in relation to a reference point.  Similarly is the
position where droplets hit determined.  This allows to position the
laser 2 or the fiber 3 to the right spot to produce the cones 4
as described.
FABRICATION OF CONES ON MECHANICAL STRUCTURES (Fig. 2)

      A rough alignment of the mechanical structure 6 against the
laser or the fiber 7 has to be provided before or after resist
application.  This depends on the intensity of light and the time
required for the alignment.  The fabrication of the cone 9 can be
done as described above.
FABRICATION OF CONES ON LASER DIODES OF THE ETCHED-FACET TYPE (Figs.
3A, 3B)

      The application of the photo-resist could be done the same way
as for the conventional lasers described above.  Since the process
allows to completely manufacture and test the laser d...