A new development could mean vastly
increase data transfer over optical fibre cables. Credit: Shutterstock
Fibre optics allow for the communication of data at the speed
of light.
But
the amount of data that can be sent along any optic fibre is limited by how
much information
you can encode into the light wave traveling through it.
Currently,
optic fibre technology uses several different properties of light to encode
information, including brightness, colour, polarization and direction of
propagation.
But
if we want to cram even more information through optic fibre, we need to use
other features of light to encode more information, without disrupting
currently used properties.
Such
a feature could help boost the bandwidth of optic fibre technology, including
our internet speeds.
Detecting
the twist
If
the light
wave traveling through the optic fibre is twisted helically – like
a spring – then it has angular momentum, which is a measure of its momentum
when it rotates around a point.
But
there was a major problem with using angular momentum to decode the information
from the optic fibre. We needed a material with tiny nanoscale helical
structures that could detect the twisted
light.
Our
research, published today in Science, shows how we can control the angular momentum of
light at a nanoscale using an integrated photonic chip.
So
for the first time, we have a chip with a series of elaborate nano-apertures and
nano-grooves that allow for the on-chip manipulation of twisted light.
The
helical design of these tiny apertures and grooves removes the need for any
other bulky interference-based optics to detect the angular momentum signals.
So
if you send an optical data signal to a photonic
chip, which is a microchip that uses light instead of electrons,
then it is important to know where the data is going, otherwise information
will be lost.
Using
our nanophotonic chip, we can precisely guide angular momentum data signals
without losing the information they carry.
What's
more, the angular momentum information of many different signals can be
processed at the same time through the chip.
The nanophotonic chip magnified
2,000 times. Each indentation on the image is a single unit of the chip, like a
single pixel in a display panel, made up of semi-circle nano-grooves and
nano-apertures engraved in a metallic film. Credit: RMIT University, Author
provided
This
means we can potentially achieve an ultra-wide bandwidth, with six-orders
magnitude of increased data access compared to current technology.
Technology
for today
Owing
to the rapid development of nano-fabrication technology, we believe there is no
technical challenge to the mass production of this chip today.
This
breakthrough opens an entirely new perspective in employing light
for chip-scale information generation, transmission and retrieval of images,
videos, sounds and so on.
It
could be used in applications such as data transmission, ultra-high definition
displays, ultra-high capacity optical communications and ultra-secure optical
encryption.
Professor
Min Gu with the nanophotonic chip that can harness the angular momentum of
light. Credit: RMIT University, Author provided
For
example, the communication speed on the National Broadband Network can be
boosted through the parallel processing of the angular momentum.
Since
the chip consists of an array of individually-controlled single units, and each
single unit is capable of independently processing the angular momentum
information, this chip device allows for parallel processing of optical
information.
A
large number of optical fibres in one fibre bundle can be processed through the
chip in parallel, which means the processing speed can be significantly
increased by considering how large the array is.
For
example, if we take 100 by 100 of such units in the array for the chip,
then the speed could be boosted by four orders of magnitude.
This
quirk of physics could one day lead to significantly faster internet speeds
along with a host of other useful applications.
http://techxplore.com/news/2016-04-boost-internet.html
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