Tech Briefs Magazine - September 2021 - PIT-24

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As impressive as that is, Khajavikhan
and her team decided to go even further.
And this is where that combination
of physics and photonics really comes
into play. Topological materials can
exhibit amazing new transport properties,
but they cannot easily be switched
between an " on " and " off " state. Think
about these light structures like a stateof-the-art
race car. They can move faster,
turn harder, and do more than their
competitors. But if you can't ever turn
the car off once you've started the
engine, it's not a very practical piece of
machinery.
That's exactly what the USC team was
t1
This novel structure produces uniquely shaped light and is only one quarter of a millimeter squared in
size. (Photo Credit: Nathan Liu)
So, what is so special about this new
structure and how did they build it? The
team first uses topological physics to
come up with a design they want to
explore. They then run simulations to
understand how the elements in the
structure should interact with each
other. Next, they design the individual
cells - the little building blocks that
make up the whole structure. Once the
cell design is complete, they must
decide how they should be arranged
together to form the structure. Finally,
the design is taken to a nano-fabrication
clean room where the physical product
- less than 0.25 square millimeter in
size - is built. What we are left with is a
totally unique structure that forms light
into a novel shape when it flows
through. This new shape, in turn, has
new qualities, such as better lasing purity
and higher efficiency.
able to do - control this new light. They
introduced a technique from photonic
systems called " optical pumping " to give
the topological properties of the structure
the ability to turn on and off. The
ability to control not just the shape of
light, but when and how it flows through
a system is of utmost importance.
For the researchers, the work on this
new structure is only just the beginning.
" Our findings open up completely new
avenues to study topological systems and
we plan on engineering more designs
that could change the face of a whole
host of industries such as holographic
screens and high-power lasers, " said
Khajavikhan.
For more information, contact Amy
Blumenthal at amyblume@usc.edu.
A Sharper Look at the Interior of Semiconductors
Friedrich-Schiller-Universitaet Jena (Jena, Thuringia, Germany)
mages provide information - what we
can observe with our own eyes enables
us to understand. Constantly expanding
the field of perception into dimensions
that have been initially hidden from the
naked eye, drives science forward. Today,
increasingly powerful microscopes let us
see into the cells and tissues of living
organisms, into the world of microorganisms,
as well as into inanimate nature. But
even the best microscopes have their limits.
" To be able to observe structures and
processes down to the nanoscale level
and below, we need new methods and
technologies, " said Dr. Silvio Fuchs from
the Institute of Optics and Quantum
Electronics at the University of Jena. This
applies
I
in particular
24
Cov
ToC
to technological
areas such as materials research or data
processing. Together with colleagues, he
has now developed a method that makes
it possible to display and study tiny, complex
structures and even " see inside "
them without destroying them.
The imaging procedure is based on
optical coherence tomography (OCT),
which has been established in ophthalmology
for a number of years, explains
doctoral candidate Felix Wiesner, the
lead author of the study. " These devices
have been developed to examine the
retina of the eye non-invasively, layer by
layer, to create 3-dimensional images. "
The
ophthalmologist's
OCT
uses
infrared light to illuminate the retina.
The radiation is selected in such a way
that the tissue to be examined does not
absorb it too strongly and it can be
reflected by the inner structures.
However, the physicists in Jena use
extremely short-wave UV light instead
of long-wave infrared light for their
OCT. In order to look into semiconductor
materials with structure sizes of only
a few nanometers, light with a wavelength
of only a few nanometers is
needed.
Generating such extremely shortwave
UV light (XUV) used to be a challenge
and was almost only possible in largescale
research facilities. Jena physicists,
however, generate broadband XUV in an
ordinary laboratory and use what are
called high harmonics for this purpose.
This radiation is produced by the interaction
of laser light with a medium and has
a frequency many times that of the original
light. The higher the harmonic
order, the shorter the resulting wavelength.
They generated light with a wavePhotonics
& Imaging Technology, September 2021

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Tech Briefs Magazine - September 2021

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