QNC - Quantum Nano Centre, Room 1501
Please join the Waterloo Institute for Nanotechnology and the Department of Applied Mathematics on Thursday, July 29, 2019 for a guest lecture by George W. Hanson, PhD, Professor in the Electrical Engineering Department at the University of Wisconsin-Milwaukee. He will be speaking on "Gyrotropic Graphene and Substrate Models, and Faraday Rotation with Nonreciprocal Quasi-Two-Dimensional Structures".[Poster]
Abstract:
Nonreciprocal two-dimensional (2D) and quasi-2D materials are of great current interest, as their development will pave the way toward small, lightweight nonreciprocal devices necessary for a range of applications (e.g., optical circulators and isolators). One important signature of optical nonreciprocity is the polarization rotation experienced by transmitted (Faraday rotation (FR)) or reflected (Kerr rotation) of light. In this work, we are interested in the far infrared/low THz regime, using graphene as a tunable nonreciprocal material. We consider two biasing methods to achieve nonreciprocity. The first is a traditional external magnetic field, used to induce a gryotropic response in graphene. The second is a magnetless approach, consisting of a 2D layer of ferrimagnetic Tm3Fe5O12 (TIG) on a Gd3Ga5O12 (GGG) substrate. The TIG layer provides an out-of-plane magnetic bias for the graphene, and should sufficiently bias the graphene for nonreciprocal effects.
We have performed experiments on Faraday rotation, based on time-domain terahertz spectroscopy, and model development and simulation, for a graphene/GGG heterostructure. The GGG substrate itself is found to have a gyrotropic response at low temperatures, which affects the FR of the hetrostructure.
Results show a giant magneto-optic effect from monolayer graphene with a Verdet coefficient greater than 100 rad/Tm, in excellent agreement with theoretical modeling based on experimentally obtained THz response parameters.
Bio:
George
Hanson has
been
a
leading
figure
in
the
field
of
nanoelectromagnetics
and
metamaterials.
His
models
have
shown
that
some
experimental
claims
of
nanoparticle
heating
for
cancer
applications
were
wrong,
further
advancing
understanding
of
this
emerging
field.
Professor
Hanson
studied
Electrical
Engineering,
obtaining
his
Bachelor’s
degree
at
Lehigh
University,
then
going
on
to
Master’
studies
at
Southern
Methodist
University,
and
completing
his
PhD
degree
at
Michigan
State
University.
At
the
University
of
Wisconsin-Milwaukee,
his
research
focuses
on
electromagnetics
and
nanoelectromagnetics
of
carbon
nanotubes
and
graphene,
quantum
optics
and
quantum
plasmonics,
metamaterials,
nonlocal
phenomena,
and
electromagnetic
wave
phenomena
in
layered
media.