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Broadband Waveguide Distributed Bragg Reflectors Based on High Index Photonic Lattice

IP.com Disclosure Number: IPCOM000117804D
Original Publication Date: 1996-Jun-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Harder, C: AUTHOR [+2]

Abstract

Waveguide Distributed Bragg Reflectors (DBRs) can only be made for the full 30nm wide Wavelength Division Multiplexing (WDM) band with photonic lattices. The traditional low index photonic lattice waveguide (drilled holes or etched in waveguide) have tremendous radiation loss into the substrate, unless they are suspended as bridges. It is rather cumbersome to fabricate such suspended bridges. Disclosed are high index photonic lattice waveguides which can be fabricated in a simple planar process and which have excellent characteristics.

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Broadband Waveguide Distributed Bragg Reflectors Based on High Index
Photonic Lattice

      Waveguide Distributed Bragg Reflectors (DBRs) can only be made
for the full 30nm wide Wavelength Division Multiplexing (WDM) band
with photonic lattices.  The traditional low index photonic lattice
waveguide (drilled holes or etched in waveguide) have tremendous
radiation loss into the substrate, unless they are suspended as
bridges.  It is rather cumbersome to fabricate such suspended
bridges.  Disclosed are high index photonic lattice waveguides which
can be fabricated in a simple planar process and which have excellent
characteristics.

      On a 'SiO' sub 2 substrate, a thin layer (a few &mu.m thin)
of oxynitride (with a higher index) is deposited to form the
waveguide in the vertical direction.  The photonic lattice is
lithograpically formed on the planar wafer, lambda '/4' lines are
opened on a pitch of lambda '/2', i.e., 100nm wide openings on a
300nm pitch for a center wavelength of 1.55&mu.m and with indexes of
the oxynitride and silicon of 2.0 and 3.6, respectively.  These lines
are then transferred  to the wafer by Reactive Ion Etching (RIE),
through the oxynitride into  the silicon dioxide substrate, a few
microns deep.  The trenches are now filled in with amorphous silicon
in a Chemical Vapor Deposition (CVD)  step.  The thin layer on the
top is removed either by mechanical or chemical means.  The lateral
waveguide is formed last in an additional  li...