Gravitational wave scientists from The University of Western Australia have
led the development of a new laser mode sensor with unprecedented precision
that will be used to probe the interiors of neutron stars and test
fundamental limits of general relativity.
Research Associate from UWA's Centre of Excellence for Gravitational Wave
Discovery (OzGrav-UWA) Dr. Aaron Jones said UWA coordinated a global
collaboration of gravitational wave, metasurface and photonics experts to
pioneer a new method to measure structures of light called "eigenmodes."
"Gravitational wave detectors like LIGO, Virgo and KAGRA store enormous
amount of optical power and several pairs of mirrors are used to increase
the amount of laser light stored along the massive arms of the detector,"
Dr. Jones said.
"However, each of these pairs has small distortions that scatters light away
from the perfect shape of the laser beam, which can cause excess noise in
the detector, limiting sensitivity and taking the detector offline.
"We wanted to test an idea that would let us zoom in on the laser beam and
look for the small 'wiggles' in power that can limit the detectors'
sensitivity."
Dr. Jones said a similar problem is encountered in the telecoms industry
where scientists are investigating ways to use multiple eigenmodes to
transport more data down optical fibers.
"Telecoms scientists have developed a way to measure the eigenmodes using a
simple apparatus, but it's not sensitive enough for our purposes," he said.
"We had the idea to use a metasurface—an ultra-thin surface with a special
pattern encoded in sub-wavelength size—and reached out to collaborators who
could help us make one."
The proof-of-concept setup the team developed was over one thousand times
more sensitive than the original apparatus developed by telecoms scientists
and the researchers will now look to translate this work into gravitational
wave detectors.
OzGrav-UWA Chief Investigator Associate Professor Chunnong Zhao said the
development is another step forward in detecting and analyzing the
information carried by gravitational waves, allowing us to observe the
universe in new ways.
"Solving the mode sensing problem in future gravitational wave detectors is
essential if we are to understand the insides of neutron stars and further
our observation of the universe in a way never before possible," Associate
Professor Zhao said.
The study has been accepted for publication in Physical Review A.
Reference:
Metasurface Enhanced Spatial Mode Decomposition, arXiv:2109.04663v2
[physics.optics]
arxiv.org/abs/2109.04663
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Physics