MAY 2016|| 11An Australian research team has designed a nanophotonic chip that
can achieve unparalleled levels of control over the angular
momentum of light. The work, published in Science (http://
tinyurl.com/hqzoqb3), opens new opportunities to use angular
momentum for the generation, transmission, processing and
recording of information, and could also be used to help scientists
better understand the evolution and nature of black holes.
While travelling approximately in a straight line, a beam of light
also spins and twists around its optical axis. The angular momentum
of light measures the amount of this dynamic rotation, and could be
harnessed to improve the capacity of optical fibres by creating
parallel light channels – an approach known as “multiplexing”.
However, the creation of angular momentum multiplexing on a
chip has remained a major challenge as there is no material in
nature capable of sensing twisted light.
“By designing a series of elaborate nano-apertures and
nanogrooves on the photonic chip, our team has enabled the on-chip
manipulation of twisted light for the first time,” said Prof Min Gu of
RMIT University. “The design removes the need for any other bulky
interference-based optics to detect the angular momentum signals.
“Our discovery could open up truly compact on-chip angular
momentum applications such as ultra-high definition displays, ultra-
high capacity optical communications and ultra-secure optical
encryption. It could also be extended to characterise the angular
momentum properties of gravitational waves to help us gain more
information on how black holes interact with each other in the
universe.”
The team devised nanogrooves to couple angular momentum-
carrying beams into different plasmonic angular momentum fields,
with the nano-apertures subsequently sorting and transmitting the
different plasmonic angular momentum signals. “Our specially
designed nanophotonic chip can precisely guide angular momentum
data signals so they are transmitted from different mode-sorting
nano-ring slits without losing any information,” said Haoran Ren, a
PhD candidate at Swinburne University of Technology.
Gu added that the research offers a precise method of studying
black holes as it enabled full control over twisted light, including
both spin angular momentum and orbital angular (Oangular)
momentum. “Due to the fact that rotating black holes can impart
Oangular momentum associated with gravitational waves, an
unambiguous measuring of the Oangular momentum through the sky
could lead to a more profound understanding of the evolution and
nature of black holes in the universe,” he said.Burial Ground Discovery
Deepens Laos Jar Mystery
Archaeologists from The Australian National University have
unearthed a 2500-year-old burial ground at one of Asia’s most
mysterious sites – the Plain of Jars in Laos.
The project in central Laos is the irst major
archaeological dig since the 1930s at any of the
90 sites that make up the Plain of Jars. The sites
feature ancient carved stone jars up to 3 metres
tall, but their purpose remains a mystery.
“This will be the irst major effort since the
1930s to attempt to understand the purpose of
the jars and who created them,” said project
leader Dr Dougald O’Reilly. “One theory is that
they were used to decompose the bodies. Later,
after the lesh was removed, the remains may
have been buried around the jars.
“What is now clear is that these are mortu-
aries and were used for the disposal of the dead.
The jars can number between one and 400 at
each site, ranging in size from 1 metre to 2 metres
tall.”
O’Reilly said the dig had revealed three
distinct types of burial. “There are pits full of
bones with a large limestone block placed over
them, and other burials where bones have been
placed in ceramic vessels,” he said. “Our exca-
vations have also revealed, for the irst time at one
of these sites, a primary burial where a body was
placed in a grave.”
O’Reilly explained that it was diicult to determine the status
of the buried individuals due to a lack of material objects buried
with them. Genetic analysis might shed some light on whom these
people were related to.
The Laos government is pushing for the Plain of Jars to be listed
as a UNESCO World Heritage site.Nanochip Captures the Power of Twisted Light
Excavations at the Plain of Jars (inset) unearthed
for the first time at one of these sites a primary
burial, where a body was placed in a grave.