Browse Prior Art Database

Two-level Chip Optical Waveguide

IP.com Disclosure Number: IPCOM000102377D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 5 page(s) / 182K

Publishing Venue

IBM

Related People

Leas, JM: AUTHOR

Abstract

Disclosed is an optical waveguide which confines light propagating in a straight line on the surface of a chip or reflects it around corners in the plane of the chip or vertically out of that plane and into a second waveguide level along which it can propagate and then be directed back to the first waveguide level. The beam can also be directed off the chip and into a fiber or from a fiber into the chip waveguide. Also disclosed are reflectors and fiber interconnects.

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This is the abbreviated version, containing approximately 40% of the total text.

Two-level Chip Optical Waveguide

       Disclosed is an optical waveguide which confines light
propagating in a straight line on the surface of a chip or reflects
it around corners in the plane of the chip or vertically out of that
plane and into a second waveguide level along which it can propagate
and then be directed back to the first waveguide level.  The beam can
also be directed off the chip and into a fiber or from a fiber into
the chip waveguide.  Also disclosed are reflectors and fiber
interconnects.

      Light from a laser or light-emitting diode (LED) formed on a
chip, or light from an optical fiber attached to the chip, is coupled
into a film of transparent high index material, such as TiO2, Ta2O5,
ZnS, SiC, or diamond, which is fully embedded in low index cladding
materials, such as SiO2 or Si3N5 .  This structure confines a
rectilinear propagating beam and permits 90o bends along either of
the two orthogonal axes by total internal reflection.  Several levels
of waveguide can be formed, allowing a high density of active optical
devices to be integrated on the chip and eliminating light leaks that
would occur if waveguides simply intersected each other in a single
level structure.

      The first level waveguide cladding is deposited in three
layers, the middle layer of which forms the sidewalls of the high
index core and includes 45o angle surfaces which bend the beam by
total internal reflection.  As will be evident from the drawings and
process description, the slanted surfaces can be oriented in several
directions and the beam redirected either in the plane or out of the
plane of the chip.  Top and bottom layers have planar surfaces
parallel to the surface of the chip and serve only to confine the
beam, which generally follows a path parallel to their surfaces.  The
middle layer of the cladding must have a significantly lower index
than the core high index material, but there are fewer restrictions
on the indexes of the top and bottom layers.

      The second level waveguide cladding is deposited in two layers
and the shaping is done on the high index core.  In this case, the
top layer of the cladding must have an index significantly lower than
the core.

      For low loss reflection and transmission, interfaces between
the high and low index materials must be optically smooth, and this
is achieved using mechanically polished or reactive ion beam assisted
etched surfaces as will be evident from the process presented below.

      The waveguide can be formed to connect two optical devices or
it can have branches so that a signal from a laser fans out to
multiple detectors or so a detector receives signals from several
lasers.

      It is known in the art to provide a chip optical waveguide that
uses the interface between silica and air to provide total internal
reflection.  The requirement of an air-silica interface poses
problems, however, including the necessity for a rough surface...