Graphene and its uses in optical
interconnects.
Technical seminar
EC-0425
Submitted by:
Submitted to:
Aaruti Sood
Mr. Abhishek Chauhan
1040930002
Assistant Prof
ECE-‘A’, 4th Yr
Deptt of ECE
SRM University, NCR Campus, Modinagar, U.P.-201204
What is Graphene?
Graphene is a flat monolayer of carbon atoms tightly packed into a two dimensional (2D)
honeycomb lattice, and is a basic building block for graphitic materials of all other
dimensionalities. It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes or stacked
into 3D graphite.
What is a fullerene?
A fullerene is any molecule composed entirely of carbon, in the form of a
hollow sphere, ellipsoid or tube.
Graphene is an isolated atomic plane of graphite. Producing graphene by the exfoliation
techniques is one of the most expensive methods, however, to use graphene in the optical
interconnects, the isolation of each graphene layer is necessary. The bonds between the layers of
graphene are very weak and hence can be broken easily rather than the bond between the
various constituent carbon molecules having a sp2 configuration.
Fields where graphene is being explored due to its properties:

Components with higher strength to weight ratios.

Transistors that operate at higher frequency.

Lower cost of display screens in mobile devices.

Storing hydrogen for fuel cell powered cars.

Sensors to diagnose diseases.

Ultra capacitors with better performance than batteries.
OPTICAL INTERCONNECTS:
What are optical interconnects?
Optical interconnect is a way of communication by optical cables. Compared to traditional
cables, optical wires are capable of a much higher bandwidth, from 10 Gbit/s up to 100 Gbit/s.
Optical fiber can be used as a medium for telecommunication and computer networking because
it is flexible and can be bundled as cables. It is especially advantageous for long-distance
communications, because light propagates through the fiber with little attenuation compared to
electrical cables. This allows long distances to be spanned with few repeaters.
An optical fiber is a cylindrical dielectric waveguide (non conducting waveguide) that transmits
light along its axis, by the process of total internal reflection. The fiber consists of
a core surrounded by a cladding layer, both of which are made of dielectric materials. To confine
the optical signal in the core, the refractive index of the core must be greater than that of the
cladding. The boundary between the core and cladding may either be abrupt, instep-index fiber, or
gradual, in graded-index fiber.
Optical interconnects even though are good for long distance communication, there are several
problems that occur in utilizing them for everyday purpose.
The fact that people have disposed of telecommunication cables long ago due to the high energy
loses during long distance transmission. If they are used in the computer systems, then we see
that the buses are mainly responsible for the interfacing and data transmission which leads to
the mismatching of data transmission signals.
32-way free-space, broadcast optical interconnect
However extensive research into the field has lead to success that if can be implemented will
lead to speeds of data transmission so high that it will be almost impossible to match.
OPTICAL INTERCONNECTS & GRAPHENE:
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.
Tingyi Gu, the study's lead author and a Ph.D. candidate in electrical engineering said that the
strong and non linear behavior of grapheme is the key component in the hybrid device and 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.
Chee Wei Wong, professor of mechanical engineering and his team have engineered a graphenesilicon 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.
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 of
Chee Wei Wong. "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."
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. "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."
Ultralow-power optical
information processing is based on
graphene on silicon photonic
crystal nanomembranes. (Credit:
Nicolette Barolini)