American Ceramic Society Bulletin

esearch briefs
New class of optical fiber developed at Penn State; ZnSe waveguide
cores open infrared spectrum
Scientists at Pennsylvania State University
report that they developed the
first optical fiber made with a core of
zinc selenide. The team is led by John
Badding, professor of chemistry at PSU,
with help from fellow researchers at the
school’s Materials Research Institute
and Department of Materials Science
and Engineering, as well as from scientists
at the Optoelectronics Research
Centre at the University of Southampton
(U.K.).
Badding says in a PSU news release,
“It has become almost a cliche to say
that optical fibers are the cornerstone
of the modern information age. These
long, thin fibers, which are three times
as thick as a human hair, can transmit
over a terabyte – the equivalent of 250
DVDs of information per second. Still,
there always are ways to improve on
existing technology. Glass has a haphazard
arrangement of atoms. In contrast,
a crystalline substance like zinc
selenide is highly ordered. That order
allows light to be transported over longer
wavelengths, specifically those in
the mid-infrared.”
The group’s methods include a specially
developed high-pressure chemical
vapor deposition technique. “The highpressure
deposition is unique in allowing
formation of such long, thin, zinc
selenide fiber cores in a very confined
space,” Badding says in the release.
According to the PSU release, “this
new class of optical fiber allows for a
more effective and liberal manipulation
of light and promises to open the door
to more versatile laser-radar technology.”
Other applications include the
development of improved surgical and
medical lasers, better countermeasure
lasers used by the military, and superior
environment-sensing lasers for measuring
pollutants and to detect the dissemination
of bioterrorist chemical agents.
New lighting uses also may be possible.
ACerS member Venkatraman Gopa-
lan, professor
at Penn State’s
Department of
Materials Science
and Engineering
and the
associate director
for the Center
for Optical
Technologies, is
a member of the
research team.
An email from
Gopalan to the
Bulletin provides
some important
context of their
optical fiber
discovery. He
notes, “Infrared
wavelength range
is extremely
important, and
yet even the
basic infrared
technologies,
such as optics,
coatings, waveguides,
lasers, and
detectors, are in
their infancy, as
compared with
technologies in
the visible or
telecon wavelengths.
This development breathes
new life into glass fibers that are usually
infrared opaque beyond approximately
2.5 microns wavelength.”
Gopalan also predicts that these
fibers could revolutionize many important
areas of optics research, such as
fiber-based guiding, imaging, spectroscopy
and tunable lasers. “The deposition
technique is versatile enough to
imagine a whole family of important
compound semiconductors making their
way into fiber cores in the near future.
Optical fibers may soon come with
(a) Schematic of the HPCVD process, where a high-pressure precursor
mixture is configured to flow into a capillary (left). When
the capillary is heated, well-developed annular films are deposited.
Unreacted precursors, carrier gas, and reaction byproducts
are carried out of the fiber (right). (b) Diascopically illuminated
optical micrograph from the side showing the transparent, uniform
ZnSe fiber core. The deposited structures can have a uniform
cross section for as long as 4 centimeter when made in a 10 centimeter
long furnace. Note that cylindrical lensing effects magnify
the interior tube diameter considerably in this view, making its
400-nanometer diameter appear much larger than it is. (c) Crosssectional
SEM image showing an overview of the silica cladding
and ZnSe core. (d) A higher magnification SEM image of the
nearly completely filled core. Scale bars: (b) 50 micrometer, c) 50
micrometer, d) 5 micrometer.
many flavors and functions well beyond
what glass can do,” writes Gopalan.
Researcher team member Anna Peacock
remarks on her website that, “ultrafast
all-fibrer optical switches will reduce
costs and improve efficiency of communications
systems, whilst laser sources,
which operate in the mid-infrared, can
be used for environmental sensing and
medical applications. The incorporation
of the active semiconductor component
into the fiber geometry provides an
important step toward seamlessly linking
semiconductor photonics with existing
20 American Ceramic Society Bulletin, Vol. 90, No. 4
(Credit: J. Badding, PSU; Advanced Materials.)