CAREER: Microscopic Study of Light Localization Hui Cao, Northwestern University, DMR-0093949

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CAREER Microscopic Study of Light Localization
Hui Cao, Northwestern University, DMR-0093949
Surface plasmons represent collective excitations
of electrons in metals. Since they act as X-ray
waves with optical frequencies, they play an
important role in nano-optics. Using the
near-field scanning optical microscopy, we have
observed for the first time the coexistence of
localized and delocalized surface plasmon modes
in percolating metal films. The localization
lengths of surface plasmon modes vary from the
size of single metal grain to that of the entire
system. The physical origin for this
inhomogeneous localization lies in the
short-range correlations among elements of the
governing Kirchhoff Hamiltonian.
1?m ? 1?m scanning electron micrograph of
percolating silver film on a glass substrate.
High-order moments of near-field intensity
enhancement as a function of silver concentration
p.
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CAREER Microscopic Study of Light Localization
Hui Cao, Northwestern University, DMR-0093949
Education One undergraduate Olivia Tang, two
graduate students H. Noh and X. Wu, one postodoc
fellow Katyayani Seal (female) have contributed
to this work. Because of her excellent work,
Olivia is selected as the member of Phi Beta
Kappa, and one of the 2006 Nanoscience Scholars
by the NSF-funded National Center for Learning
and Teaching in Nanoscale Science and
Engineering. She has also successfully obtained
the Northwestern University Undergraduate
Research Grant.
Societal Impact The ability to localize and
delocalize optical excitations in
metal-dielectric nano-composites is very
important to the development of nano-scale
photonic devices. Strong localization of
electromagnetic energy in the nano-scale can
enhance various linear and nonlinear optical
processes, while the delocalization allows the
buildup of spatial correlations over large
distance.