Tech Briefs Magazine - February 2024 - 32

Imaging
produced by a radar installation on Cape
Cod, which is a building so large it is visible
from space. While the Cape Code
radar is able to cover a much larger area,
the new reflectarray is the first to bring military-grade
resolution to a device for commercial
intelligent machines.
" Antenna arrays are very interesting because,
just by changing the time delays
that are fed to each antenna, you can
change the direction the energy is focused,
and it is completely electronic, " said Dr. Nathan
Monroe. " So, it stands as an alternative
to those big radar dishes you see at the
airport that move around with motors. We
can do the same thing, but we don't need
any moving parts because we are just
changing some bits in a computer. "
For more information, contact Abby
This image shows the semiconductor terahertz beam former, with almost 10,000 built-in elements.
(Image: The researchers)
Abazorius at abbya@mit.edu; 617-2532709.
Metasurfaces
Control Polarized Light at Will
The research could lead to applications in diverse fields including imaging, microscopes,
displays, and astronomy.
Harvard John A. Paulson School of Engineering, Cambridge, MA
F
or years, researchers at SEAS have engineered
metasurfaces to manipulate
light based on its polarization state. That
research has contributed to advances in
polarization technology but metasurface
technology has proven more powerful
than even the researchers themselves real(a)
Ades
∝ L R
Bright when jin
Dark when jin
R
L
ky
kx
Screen in
far-field
y
J (x,y)
jin
x
F
Collimated incident light of
variable polarization
Illustrative example of a polarization-analyzing hologram. When illuminated with a laser light, the
metasurface hologram implements a far-field in which light is directed on the basis of its incident
polarization state. In this particular example, the hologram is designed to produce a pattern of illustrations
of different polarization states. (Image: Capasso Lab/Ha SEAS)
32
www.techbriefs.com
Ades
Dark when
Bright when
∝ x x
jin
jin
= x
= y
ized. Now, they have uncovered hidden
potential in these metasurfaces and
demonstrated optical devices that manipulate
light's polarization state with an unprecedented
degree of control.
The new metasurface can encode an
unlimited number of holographic images
or manipulate light in a virtually infinite
number of directions based on a
very large number of polarization states.
The research demonstrates a new way
to control polarized light with metasurfaces.
This new approach, in which a holographic
image can be engineered with
a polarization-tunable response across
the image itself, could lead to applications
in diverse fields including imaging,
microscopes, displays, and astronomy.
According to the researchers, this advancement
is general and could be applied
to almost any kind of optical system
that uses polarized light. Their
work suggests that metasurfaces could
be used in new types of laser systems
whose light output could be engineered
based on the light's polarization state,
or perhaps in telescope systems where
similar types of optics are already being
used, to aid in the detection of Earthlike
exoplanets.
Holography has always been a popular
technique to record and display information
- this research has taken a fundamental
principle of holography and
generalized it in a way that greatly expands
the information capacity of this
rather old technique.
For more information, contact Leah
Burrows at lburrows@seas.harvard.edu.
Tech Briefs, February 2024
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Tech Briefs Magazine - February 2024

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