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Distributed Feedback Structure Produced Without Growth Interruption

IP.com Disclosure Number: IPCOM000099621D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Tischler, MA: AUTHOR

Abstract

Disclosed is a distributed feedback (DFB) structure which is formed in one growth step, in contrast to conventional techniques which require at least two growth steps. The DFB requires a periodic change in dielectric constant, with the period equal to one half of the optical wavelength in the material. This structure is conventionally produced by depositing a material with dielectric constant e1, etching grooves having the proper spacing, and then depositing a different material with a different dielectric constant e2 (see Fig. 1). This process is quite complicated, involving two deposition steps separated by patterning and etching.

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Distributed Feedback Structure Produced Without Growth Interruption

       Disclosed is a distributed feedback (DFB) structure which
is formed in one growth step, in contrast to conventional techniques
which require at least two growth steps.  The DFB requires a periodic
change in dielectric constant, with the period equal to one half of
the optical wavelength in the material.  This structure is
conventionally produced by depositing a material with dielectric
constant e1, etching grooves having the proper spacing, and then
depositing a different material with a different dielectric constant
e2 (see Fig. 1).  This process is quite complicated, involving two
deposition steps separated by patterning and etching.

      The one growth-step process uses a fractional superlattice to
provide the periodic change in dielectric constant.  In this process,
the substrate is first prepared by being misoriented a specific
amount, producing steps spaced with a period equal to that required
for the DFB structure.  The period for these structures depends on
the material and wavelength but is generally around 100-300 nm. The
angle at which the substrate must be misoriented is given by r =
tan-1 (a0/P), where a0 is the thickness of a monolayer of the
material and P is the period required for the feedback structure.
This is shown in Fig. 2A.  For periods of 100-300 nm, r = .16 -.05o
.  The substrate is now ready for deposition of the feedback
structure in one step. This is done...