nanotehnoloogia, nanoteknologia, nanotechnologija, nanotehnologijas, nanoteknologija,
nanotechnologii, nanotecnologia, nanotehnologijo, nanoteknik
compact communication, signal processing and sensing
optics technologies, multiple wavelengths of light
are combined as a space-saving measure as they carry
information. The wavelengths must then be separated
again when they reach their destinations. Wavelengths
used for these sophisticated applications have very
high spectral resolution, meaning the distance between
wavelengths is very small. The device that sorts
out these crowded wavelengths is called a wavelength-demultipler
Compact optical WDs are key in spectral analysis for biosensers small enough
to fit on a chip and for integrated circuits for optical information processing.
Georgia Tech researchers have designed a WD able to function at very high resolution
in much tighter confines (as small as 64 microns by 100 microns — smaller
than a millimeter) by developing a new design for photonic crystals, which
are highly periodic structures typically etched in very thin silicon that are
designed to control light and have the potential to revolutionize everything
from computing to communications. The research had been published in Laser
Focus World and Optics Express and was recently presented at the Conference
on Lasers and Electro-Optics (CLEO 2006).
“We believe we have developed the most compact WD that has been reported to date,” said
Ali Adibi, a professor in Georgia Tech's School of Electrical and Computer Engineering
and the lead researcher on the project. “If you want to have many optical functions
on a single micro- or nano-sized chip, you have to be able to practically integrate
all those functions in the smallest amount of space possible. Our WD solves many
problems associated with combining delicate optical functions in such a small
The Georgia Tech team was able to shrink its WD by combining into one crystal
three unique properties of photonics crystals — the superprism effect (separating
wavelengths much more finely than a regular prism), negative diffraction or
focusing (reversing the expansion of the light beam and focusing it back to
its original size after interacting with the material being analyzed) and negative
refraction (filtering wanted and unwanted wavelengths).
By combining these effects, Georgia Tech's WD takes an expanded beam of
light and instead of expanding it further as wavelengths are separated, focuses
the wavelength into different locations. The structure simultaneously separates
wavelengths, focuses wavelengths instead of refracting them and then separates
the wavelengths in one structure, solving the problems associated with wavelength
interference without adding extra devices to the system.
“This project really demonstrates the importance of dispersion engineering in
photonic crystals — and it's all done by changing the geometry of some holes
you etch in the silicon. It's very simple and it allows you to combine properties
into one material that you never could before,” Adibi said.
Despite the more advanced capabilities of the photonic crystals used in Georgia
Tech's WD, they are no more complex or difficult to manufacture than conventional
photonic crystals, Adibi added.
The team members created these newly optimized crystals by using a modeling
tool they developed two years ago to test the properties of a material much
faster than time-consuming conventional numerical methods.
The result is a WD that is less than a millimeter in all dimensions rather
than the several centimeters of other currently available WDs. Furthermore,
Georgia Tech's WD can be integrated for several other functionalities on a
single chip for signal processing, communications, or sensing and lab on-a-chip
The work was supported by the Air Force Office of Scientific Research (AFOSR,
G. Pomrenke) and in part by the National Science Foundation (NSF) and David
and Lucile Packard Foundation.
The Georgia Institute of Technology is one of the nation's premiere research
universities. Ranked ninth among U.S. News & World Report 's top public
universities, Georgia Tech educates more than 17,000 students every year
through its Colleges of Architecture, Computing, Engineering, Liberal Arts,
Management and Sciences. Tech maintains a diverse campus and is among the
nation's top producers of women and African-American engineers. The Institute
offers research opportunities to both undergraduate and graduate students
and is home to more than 100 interdisciplinary units plus the Georgia Tech
Research Institute. During the 2004-2005 academic year, Georgia Tech reached
$357 million in new research award funding. The Institute also maintains
an international presence with campuses in France and Singapore and partnerships
throughout the world.