Tuesday, April 29, 2014 - 3:30pm
Regents 109
The experimental discovery of two-dimensional (2D) gated
graphene in 2004 by Novoselov and Geim is a seminal event in electronic
materials science, ushering in a tremendous outburst of scientific activity in
the study of electronic properties of this unique two-dimensional material with
a gapless Dirac electronic spectrum. The lack of a traditional bandgap makes
graphene an exceptionally versatile photonic material, and the ability to dope
graphene through metallic contacts and tune the carrier density through the
application of a gate opens possibilities for a variety of transformative
photonic devices. In particular highly doped graphene has recently been
recognized as a powerful plasmonic material that combines many important
properties at terahertz (THz) frequencies with the ability of being
electrically tunable. Terahertz radiation has uses from security to medicine.
Currently, however, THz technology is notoriously underdeveloped. Graphene
plasmonics has promise of filling in this conspicuous gap in the
electromagnetic spectrum with a robust and radically new technology. Recently,
sensitive room temperature THz detectors have been demonstrated that operate on
a photo-thermo-electric principle with response times of 10s of femtoseconds.
THz absorption in a graphene element raises the temperature of the graphene
carriers, which then diffuse to the contacts made of dissimilar metals and
produces a photo voltage proportional to the Seebeck coefficient of the
graphene. A source of THz radiation based on this photo-thermo-electric effect
also looks promising. A graphene element is used as an optical mixer of near IR
to generate THz plasmons which are then coupled to free space radiation by an
antenna. A review of graphene and these THz developments will be described.
Host:
Paola Barbara
Discussion Leader:
Paola Barbara
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