Appeal No. 1997-4033
Application No. 08/589,584
Claim 22, the only independent claim, reads as follows:
22. A Mach-Zehnder optical modulator having first and
second passive regions and an active region between said first
and second passive regions, said Mach-Zehnder optical
modulator comprising:
a semiconductor substrate extending over said first and
second passive regions and said active region;
a bottom electrode extending on an entire part of a
bottom surface of said semiconductor substrate;
a first cladding layer extending on an entire part of a
top surface of said semiconductor substrate;
a ridge-shaped optical wave-guide having: a Y-shaped
branching passive wave-guide section on said first passive
regions [sic, region]; a Y-coupling passive wave-guide section
on said second passive regions [sic, region]; and two parallel
straight phase modulator sections on said active region;
wherein said ridge-shaped optical wave-guide comprises:
a buffer layer provided on said first cladding layer;
a multiple quantum well optical wave-guide layer provided
on said buffer layer, said multiple quantum well optical wave-
guide
layer being grown by a metal organic vapor phase epitaxy using
dielectric stripe masks having a large width in said active
region and a small width in said first and second passive
regions so that said multiple quantum well optical wave-guide
layer provided on said first and second passive regions has a
thickness larger than that provided on said active region and
so that said multiple quantum well optical wave-guide layer
provided on said first and second passive regions has a band
gap wavelength smaller than that provided on said active
region;
a second cladding layer provided on said multiple quantum
well optical wave-guide layer;
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