Appeal No. 1998-2938
Application 08/510,752
(col. 5, lines 60-66). As noted by the Examiner (FR2),
Ishikawa does not teach a non-uniform lattice constant or
strain profile. Appellants argue that the AlGaAs system is
well known for the property that aluminum can be substituted
for gallium with a negligible change of lattice constant, and
hence a negligible effect on strain, and so Ishikawa is
limited to structures having non-uniform composition but
uniform lattice constant (Br5-6); this statement has not been
challenged by the Examiner and is accepted as fact.
Zucker discloses a polarization independent
electrooptical waveguide. The waveguiding region comprises
one or more strained quantum well layers (col. 4,
lines 44-46). Strain is introduced by changing the lattice
constant and, therefore, the degree of lattice mismatch for a
composition such as In Ga As by varying the mole fraction x
x 1-x
(col. 5, lines 28-32). Lattice mismatching can be defined
with respect to the substrate or with respect to any layer
(col. 5, lines 44-47). Zucker discloses that the material
combination GaAs/AlGaAs (the combination used in Ishikawa),
among others, may be used instead of the GaAs/InGaAs
composition discussed (col. 8, lines 17-28).
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