Tech Briefs Magazine - November 2023 - PIT-16

that we understand how to interpret
the results. Now we can start studying
all these materials in a way that we
couldn't before. "
To conduct the experiment, the researchers
had to get creative. Essentially,
they decided to make things easier by
making them more complicated. With
the typical technique, for instance, blue
light is hard to use because its wavelength
is so short, meaning that it is
more challenging to focus over the right
spot near the metal tip. If not aligned
just right, the measurement won't work.
With the red light, this focusing condition
is more relaxed, making it easier to
align the optics in order to extract the
scattered light efficiently.
With those challenges in mind, the researchers
used the blue light to not only
illuminate the sample so that the light
scatters, but also to produce a burst of
terahertz radiation from the sample.
The radiation carries important information
about the sample's electrical
properties. While the solution adds an
extra step and increases the amount of
data the scientists have to analyze, it
eliminates the need to be as precise in
how they align the tip over the sample.
The key here is that because the terahertz
radiation has a much longer wavelength,
it is much more easily aligned.
" It still has to be really close, but it
doesn't have to be as close, " Mittleman
said. " When you hit it with the light,
you'll still be able to get information in
the terahertz. "
The researchers are excited to see what
comes next in terms of new information
and discoveries the method leads to, such
as better insights into the semiconductors
used to produce blue LED technology.
For more information, contact Juan
Siliezar at juan_siliezar@brown.edu.
Researchers Create World's Smallest LED And Holographic Microscope
With this development, existing mobile phone cameras can be converted into high-resolution microscopes.
Singapore-MIT Alliance for Research and Technology (SMART)
R
esearchers from the Disruptive
& Sustainable Technologies for
Agricultural Precision (DiSTAP) and
the Critical Analytics for Manufacturing
Personalized-Medicine (CAMP) Interdisciplinary
Research Groups (IRG) of
the Singapore-MIT Alliance for Research
and Technology (SMART), MIT's research
enterprise in Singapore, have developed
the world's smallest LED. It enables
the conversion of existing mobile
phone cameras into high-resolution microscopes.
Smaller than the wavelength
of light, the new LED was used to build
the world's smallest holographic microscope,
paving the way for existing cameras
in everyday devices such as mobile
phones to be converted into microscopes
with modifications to the silicon chip and
software. This technology also represents
a significant step forward in the miniaturization
of diagnostics for indoor farmers
and sustainable agriculture.
This breakthrough was supplemented
by the researchers' development of a revolutionary
neural networking algorithm
that is able to reconstruct objects measured
by the holographic microscope,
thus enabling enhanced examination of
microscopic objects such as cells and bacteria
without the need for bulky conventional
microscopes or additional optics.
The research also paves the way for a major
advancement in photonics - the
building of a powerful on-chip emitter
that is smaller than a micrometer, which
has long been a challenge in the field.
The light in most photonic chips
originates from off-chip sources, which
16
300 mm
3mm
2mm
1 µm
beads sample
CMOS imager
(a) Photograph of a fully fabricated 300 mm wafer. (b) Close-up of a chip die. (c) Infrared micrograph with
the LED turned on. (d) Holographic microscope setup. (e) Close-up of a reconstructed holographic image
compared with the (f) ground truth. (Image: Singapore-MIT Alliance for Research and Technology)
leads to low overall energy efficiency
and fundamentally limits the scalability
of these chips. To address this issue,
researchers have developed on-chip
emitters using various materials such
as rare-earth-doped glass, Ge-on-Si,
and heterogeneously integrated III-V
materials. While emitters based on
these materials have shown promising
device performance, integrating their
fabrication processes into standard
complementary metal-oxide-semiconductor
(CMOS) platforms remains
Lorem ipsum
challenging. While silicon (Si) has
shown potential as a candidate material
for nanoscale and individually controllable
emitters, Si emitters suffer
from low quantum efficiency because
of the indirect bandgap, and this fundamental
disadvantage combined with
the limitations set by the available materials
and fabrication tools has hindered
the realization of a small native
Si emitter in CMOS.
In a recently published Nature Communications
paper, " A sub-wavelength
Photonics & Imaging Technology, November 2023

Tech Briefs Magazine - November 2023

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