The discovery of graphene will turn out to be as important as the
discovery of the transistor fifty years ago. This item reports on
the remarkable utility of graphene in electro-optical manipulation.
This with the advent of graphene sheets opens up manufacturing
possibilities for large chip embedded devices.
The advent of graphene is steadily liberating us from the limitations
of silicon and setting us up for astounding discoveries ans
development.
What has astonished myself over the years is how easy it has been to
recognize a need in our manipulation of matter and photonic energy
and then to see it gratified in ways that could not be anticipated
yet still be gratified. All dead ends have nimbly been bypassed.
Moore's Law still rules supreme although I am sure that an army of
grad students can show me that it will hit the wall just as they did
forty years ago. Of course, no one is brave enough anymore.
Perhaps some day we will have a Holodec that that draws heat from the
environment:-)
Unique properties
of graphene lead to a new paradigm for low-power telecommunications
Published: Sunday,
July 15, 2012 - 14:02 in Physics & Chemistry
New research by
Columbia Engineering demonstrates remarkable optical nonlinear
behavior of graphene that may lead to broad applications in optical
interconnects and low-power photonic integrated circuits. With the
placement of a sheet of graphene just one-carbon-atom-thick, the
researchers transformed the originally passive device into an active
one that generated microwave photonic signals and performed
parametric wavelength conversion at telecommunication wavelengths.
"We have been able to demonstrate and explain the strong
nonlinear response from graphene, which is the key component in this
new hybrid device," says Tingyi Gu, the study's lead author and
a Ph.D. candidate in electrical engineering. "Showing the
power-efficiency of this graphene-silicon hybrid photonic chip is an
important step forward in building all-optical processing elements
that are essential to faster, more efficient, modern
telecommunications. And it was really exciting to explore the 'magic'
of graphene's amazingly conductive properties and see how graphene
can boost optical nonlinearity, a property required for the digital
on/off two-state switching and memory."
The study, led by Chee
Wei Wong, professor of mechanical engineering, director of the Center
for Integrated Science and Engineering, and Solid-State Science and
Engineering, will be published online in the Advance Online
Publication on Nature Photonics's website on July 15 and in
print in the August issue. The team of researchers from Columbia
Engineering and the Institute of Microelectronics in Singapore are
working together to investigate optical physics, material science,
and device physics to develop next-generation optoelectronic
elements.
They have engineered a
graphene-silicon device whose optical nonlinearity enables the system
parameters (such as transmittance and wavelength conversion) to
change with the input power level. The researchers also were able to
observe that, by optically driving the electronic and thermal
response in the silicon chip, they could generate a radio frequency
carrier on top of the transmitted laser beam and control its
modulation with the laser intensity and color. Using different
optical frequencies to tune the radio frequency, they found that the
graphene-silicon hybrid chip achieved radio frequency generation with
a resonant quality factor more than 50 times lower than what other
scientists have achieved in silicon.
"We are excited
to have observed four-wave mixing in these graphene-silicon photonic
crystal nanocavities," says Wong. "We generated new optical
frequencies through nonlinear mixing of two electromagnetic fields at
low operating energies, allowing reduced energy per information bit.
This allows the hybrid silicon structure to serve as a platform
for all-optical data processing with a compact footprint in dense
photonic circuits."
Wong credits his
outstanding students for the exceptional work they've done on the
study, and adds, "We are fortunate to have the expertise right
here at Columbia Engineering to combine the optical nonlinearity in
graphene with chip-scale photonic circuits to generate microwave
photonic signals in new and different ways."
Until recently,
researchers could only isolate graphene as single crystals with
micron-scale dimensions, essentially limiting the material to studies
confined within laboratories. "The ability to synthesize
large-area films of graphene has the obvious implication of enabling
commercial production of these proven graphene-based technologies,"
explains James Hone, associate professor of mechanical
engineering, whose team provided the high quality graphene for this
study. "But large-area films of graphene can also enable the
development of novel devices and fundamental scientific studies
requiring graphene samples with large dimensions. This work is an
exciting example of both -- large-area films of graphene enable the
fabrication of novel opto-electronic devices, which in turn allow for
the study of scientific phenomena."
Commenting on the
study, Xiang Zhang, director of the National Science Foundation
Nanoscale Science and Engineering Center at the University of
California at Berkeley, says, "this new study in integrating
graphene with silicon photonic crystals is very exciting. Using the
large nonlinear response of graphene in silicon photonics
demonstrated in this work will be a promising approach for ultra-low
power on-chip optical communications."
"Graphene has
been considered a wonderful electronic material where electron
moves like an effectively massless particle in the atomically thin
layer," notes Philip Kim, professor of physics and applied
physics at Columbia, one of the early pioneers in graphene research
and who discovered its low-temperature high electronic conductivity.
"And now, the recent excellent work done by this group of
Columbia researchers demonstrates that graphene is also unique
electro-optical material for ultrafast nonlinear optical modulation
when it is combined with silicon photonic crystal structures.
This opens an important doorway for many novel optoelectronic device
applications, such as ultrafast chip-scale high-speed optical
communications."
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