Megan McRainey
Institute Communications and Public Affairs
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Associate
Professor Adibi’s research team has produced
a prototype of their technology. |
Being the delicate optical instruments that they are,
spectrometers are pretty picky about light.
But Georgia Tech researchers have developed a technology
to help spectrometers — instruments that can be
used as the main parts of sensors to detect substances
present in ultra-small concentrations — analyze
with fewer parts in a wide variety of environments,
regardless of lighting. The technology can improve portability,
while reducing the size, complexity and cost of many
sensing and diagnostics systems that use spectrometers.
Conventional spectrometers have multiple parts: a narrow
slit, a lens to guide light, a grating to separate wavelengths,
a second lens and a detector to detect the power at
different wavelengths. The Georgia Tech team’s
goal was to combine all these pieces into two parts
— a volume hologram (formed in an inexpensive
piece of polymer) and a detector — to create a
compact, efficient and inexpensive spectrometer that
could be used for multiple spectroscopy and sensing
applications.
“This technology is very useful for low-end spectrometers,
but at the same time, there are many applications that
require high-end spectrometers,” said Ali Adibi,
head of the project and an associate professor in the
School of Electrical
and Computer Engineering. “This technology
could convert a portion of a complex, high-end system
into a much more versatile and light system.”
Because of its light weight, the new design helps create
more versatile and portable spectrometers for several
applications where portability had been difficult. For
instance, the technology would make handheld devices
possible for carbon monoxide detection or on-the-spot
blood analysis and other biomedical applications.
Another of the key advantages to the new spectrometer
is its relative insensitivity to alignment. Spectrometers
are very sensitive to both the direction and wavelength
of light — in fact, several of its parts are devoted
to keeping the light correctly directed.
But the research team was able to incorporate those
necessary alignments together with the focusing functions
into a volume hologram. This hologram is recorded by
the interference pattern of two beams in a piece of
photopolymer.
“There were lots of challenges because the light
we need to analyze is diffuse in nature,” Adibi
said.
Spectrometers work the best under collimated light
(i.e. light moving in only one direction). In conventional
spectrometers, this problem is solved by blocking light
in all but one direction using a slit and a lens, but
results in considerable power loss and lower efficiency.
“By choosing the appropriate hologram, we have
no collimating hardware in our system,” Adibi
said. “We have further demonstrated the capability
of improving the throughput by using more complex holograms
[that are recorded similar to less complex holograms]
in our spectrometer without adding to the actual complexity
of the system.”
The team has a prototype for a lower-end spectrometer
comparable to those currently on the market but for
a considerably lower cost. According to Adibi, the research
team will now focus on developing systems to improve
the efficiency — and thereby the sensitivity —
of its spectrometers.
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