Browse Prior Art Database

Corrected Etched Side Walls for Integrated Optics

IP.com Disclosure Number: IPCOM000114410D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Goodman, DS: AUTHOR [+5]

Abstract

Silica-on-silicon optical waveguides are attractive for integrated optics because of the low waveguide and fiber coupling losses but etching of the material is difficult. The reactive ion etching requires long (and therefore expensive) etch times, but an additional problem is the significant undercut and nonverticality of the etched wall. This is not a problem for standard waveguide devices, but it is a major limitation for newer devices which rely on etched reflectors. Typically, the waveguide cores are 8 &mu m deep and the mask must be 1 &mu m wider on each side to allow for undercut. This problem can easily be corrected by compensation in the mask. By comparison, a reflective surface defined by an etched wall requires a much deeper etch.

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Corrected Etched Side Walls for Integrated Optics

      Silica-on-silicon optical waveguides are attractive for
integrated optics because of the low waveguide and fiber coupling
losses but etching of the material is difficult.  The reactive ion
etching requires long (and therefore expensive) etch times, but an
additional problem is the significant undercut and nonverticality of
the etched wall.  This is not a problem for standard waveguide
devices, but it is a major limitation for newer devices which rely on
etched reflectors.  Typically, the waveguide cores are 8 &mu m deep
and the mask must be 1 &mu m wider on each side to allow for
undercut.  This problem can easily be corrected by compensation in
the mask.  By comparison, a reflective surface defined by an etched
wall requires a much deeper etch.  For an 8 &mu m high waveguide, the
reflective wall should be at on the order of 30 &mu m high because it
needs to cover the entire upper cladding, the core, and as much of
the lower cladding as a significant part of the guided mode extends
into.  The wall is typically metallized.  Any tilt or curvature of
the etched wall affects where the reflected light is directed and can
cause unacceptable loss.  Furthermore, if the the etched reflectors
is a grating there is a large loss of feature resolution [1].  This
invention describes a way to make hybrid devices that use silica
where low loss is required, but photosensitive polymer where etching
is critical.

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