[labmembers] University PhD Dissertation Defense of Aaswath Raman

Aaswath Raman aaswath at stanford.edu
Wed Feb 6 17:45:24 PST 2013


Department of Applied Physics
University PhD Dissertation Defense

Broadband Nanophotonics: Plasmonic Band Theory & Light Trapping in Solar
Cells

Aaswath Pattabhi Raman
Research Advisor: Professor Shanhui Fan

Friday February 15, 2013 @ 2:00 PM
Location: Allen Building (CIS-X), Room 101

ABSTRACT

Subwavelength photonic structures enable a remarkable degree of control
over light propagation and absorption at nanoscale dimensions. From sensing
and modulation, to on-chip communication and light trapping in solar cells,
new device applications and opportunities now motivate the need for a
richer understanding of the optical properties of plasmonic structures and
metamaterials over a broad range of frequencies.

In this talk, I will first introduce a photonic band theory that rigorously
models the broadband behavior of plasmonic nanostructures and
metamaterials. The theory formulates plasmonic band structures as
Hermitian eigenvalue equations, and offers an intuitive physical picture of
modal material loss. An upper bound on the modal material loss rate is then
derived, placing fundamental limits on device operation. Furthermore, I
will present a perturbation theory that elucidates the effect of dielectric
refractive index modulation and metallic plasma frequency variation in
plasmonic nanostructures.

Next, I will present a nanophotonic light trapping theory for solar cells
and show that, using a nanophotonic design, one can exceed conventional
limits on light trapping for all absorption regimes of the active material.
The theory's insights are then applied to organic solar cells to design a
dielectric light trapping structure that provides 10-15% photocurrent
enhancement relative to an optimized planar organic solar cell. Finally, I
will use the plasmonic band theory to probe the role of parasitic loss in
the metal on achievable absorption enhancement factors in plasmonic light
trapping schemes.
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