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My principal field of interest is a). light for computation
and communication on a chip and b). light for energy
generation. The approach is based on Si CMOS
platform that shortens time-lag between basic research
and commercialization. We refer this field to as Sibased
photonics. The goal is for students to experience
a typical cycle of research; discover-understand -
prototype-innovate, and eventually to demonstrate the
impact of research.
a) Light for computation and communication on a chip
Light is an enabler to enhance the performance of Si-
LSIs. My works have shown that light can be
manipulated on a chip. The first challenge was making
photonic devices small. We have implemented “highindex
contrast optics” on a chip. The second challenge
was reducing materials diversity in photonics. We have
prototyped Si waveguides, and Ge photodetectors. The
next targets are Si-based modulators and light emitters.
We have been exploring the SiGe Franz-Keldysh effect
for modulation and Si:Er for light emission. The final
challenge in Si-based photonics is to reduce device
diversity. Essential device functions in photonics are
light emitting, waveguiding, detecting, filtering,
isolating, amplifying, modulating, coupling/splitting,
polarization-rotating, etc. Conceptual works are going
on.
b) Light for energy generation
Solar energy is clean, and an infinite power source as far
as lifetime of the human beings on the earth is
concerned. Another feature of solarcells “distributed
power sources” will be even more important in terms of
home-land security. My current activity is focused on
cost-effective Si solarcell with an efficiency beyond the
current maxium (24.5%). We have been implementing
photonic nano-structures to utilize the superprism effect.
Interested in how far we can go for the theoretical limit
93%. We are also working to generate electricity from
heat so far wasted, based on monolithically integrated
Ge thermo-photovoltaic cells on Si. |
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| Y. Ishikawa, K. Wada, D.D. Cannon, H.-C. Luan, and
L.C. Kimerling: “Strain-induced Bandgap Shrinkage Ge
grown on Si substrates”, Appl. Phys. Lett., 82 (2003)
2044
Y. Yi, P. Bermel, K. Wada, X. Duan, J.D. Joannopoulos,
and L.C. Kimerling: “A Tunable, Multichannel Optical
Filter Based on Si-MEMS Actuation”, Appl. Phys. Lett.,
81 (2002) 4112
M. Popovic, K. Wada, S. Akiyama, H.A. Haus, and J.
Michel: “Air Trenches for Sharp Silica Waveguide
Bends”, J. Lightwave Technology, 20 (2002) 1762 |
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