Tech Briefs Magazine - May 2024 - PIT-23

sparser pixels for the peripheral regions, "
Ni said. " This allows for the more important
aspects of a photo to come through
clearly while others remain less in focus,
thereby saving data bandwidth. "
The metasurface is placed in front of a
camera so that light first passes through
it and transforms the image from the
Cartesian system into log-polar coordinates
before it is digitalized by a camera
and transferred to a computer. Since it
works using nanostructures that bend
light, the metasurface does not need any
power and works at the speed of light.
" As an image of an object can vary in size
or orientation, it is desirable to preprocess
images to make them resistant to scale and
rotation changes, " Ni said. " This preprocessing
helps AI applications more easily
recognize them as the same object. "
By placing a different metasurface in
front of a camera, researchers also can
transform the log-polar image back into the
original image with Cartesian coordinates.
The invention has many potential applications,
the researchers said, including
for use in target tracking and surveillance
to map how a car, for example,
moves across a city.
" A metasurface can be used in tandem
with AI systems as a preprocessor, making
it easier to recognize the same car
from multiple street view cameras, " Ni
said. " Or if it is applied to a satellite, it
could potentially track planes from takeoff
to landing. "
For more information, contact College
of Engineering Media Relations at
communications@engr.psu.edu.
A New Optical Metamaterial Makes True One-Way Glass Possible
Researchers have discovered how to make a new optical metamaterial that would underpin a variety
of new technologies.
Aalto University, Finland
A
new approach has allowed researchers
at Aalto University to design
a kind of metamaterial that has so
far been beyond the reach of existing
technologies. Unlike natural materials,
metamaterials and metasurfaces can be
tailored to have specific electromagnetic
properties, which means scientists
can create materials with features desirable
for industrial applications.
The new metamaterial takes advantage
of the nonreciprocal magnetoelectric
(NME) effect. The NME effect
implies a link between specific properties
of the material (its magnetization
and polarization) and the different
field components of light or other electromagnetic
waves. The NME effect is
negligible in natural materials, but scientists
have been trying to enhance it
using metamaterials and metasurfaces
because of the technological potential
this would unlock.
" So far, the NME effect has not
led to realistic industrial applications.
Most of the proposed approaches
would only work for microwaves and
not visible light, and they also couldn't
be fabricated with available technology, "
said Shadi Safaei Jazi, a doctoral
researcher at Aalto. The team designed
an optical NME metamaterial that can
be created with existing technology, using
conventional materials and nanofabrication
techniques.
The new material opens up applications
that would otherwise need a
strong external magnetic field to work
- for example, creating truly onePhotonics
& Imaging Technology, May 2024
The magnetic properties of a material can affect how it interacts with light. (Image: Ihar Faniayeu/
University of Gothenburg)
way glass. Glass that's currently sold as
'one-way' is just semi-transparent, letting
light through in both directions.
When the brightness is different between
the two sides (for example, inside
and outside a window), it acts like
one-way glass. But an NME-based oneway
glass wouldn't need a difference in
brightness because light could only go
through it in one direction.
" Just imagine having a window with
that glass in your house, office, or car.
Regardless of the brightness outside,
people wouldn't be able to see anything
inside, while you would enjoy a perfect
view from your window, " said Safaei. If
the technology succeeds, this one-way
glass could also make solar cells more
efficient by blocking the thermal emissions
that existing cells radiate back toward
the sun, which reduces the amount
of energy they capture.
The research was published in Nature
Communications on February 12, 2024.
For more information, contact Shadi
Safaei Jazi at shadi.safaeijazi@aalto.fi.
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Tech Briefs Magazine - May 2024

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