New Nanotech Discovery at Rensselaer Polytechnic Institute Could Lead to Breakthrough in Infrared Satellite Imaging Technology
Researchers Develop Lens-Less, Gold-Covered
“Microlens” That Enhances Imaging Signal Without Increasing
Rensselaer Polytechnic Institute
Professor Shawn-Yu Lin has developed a new
nanotechnology-based “microlens” that uses gold to boost
the strength of infrared imaging and could lead to a new
generation of ultra-powerful satellite cameras and
night-vision devices. The device, pictured, leverages the
unique properties of nanoscale gold to “squeeze” light
into the tiny holes in its surface.
Researchers from Rensselaer Polytechnic Institute have
developed a new nanotechnology-based “microlens” that uses gold
to boost the strength of infrared imaging and could lead to a
new generation of ultra-powerful satellite cameras and
By leveraging the unique properties of nanoscale gold to
“squeeze” light into tiny holes in the surface of the device,
the researchers have doubled the detectivity of a quantum
dot-based infrared detector. With some refinements, the
researchers expect this new technology should be able to
enhance detectivity by up to 20 times.
This study is the first in more than a decade to demonstrate
success in enhancing the signal of an infrared detector without
also increasing the noise, said project leader Shawn-Yu
Lin, professor of physics at Rensselaer and a member of the
university’s Future Chips
Constellation and Smart Lighting
Engineering Research Center.
“Infrared detection is a big priority right now, as more
effective infrared satellite imaging technology holds the
potential to benefit everything from homeland security to
monitoring climate change and deforestation,” said Lin, who in
2008 created the world’s
darkest material as well as a coating
for solar panels that absorbs 99.9 percent of light from
nearly all angles.
“We have shown that you can use nanoscopic gold to focus the
light entering an infrared detector, which in turn enhances the
absorption of photons and also enhances the capacity of the
embedded quantum dots to convert those photons into electrons.
This kind of behavior has never been seen before,” he said.
Results of the study, titled “A Surface Plasmon Enhanced
Infrared Photodetector Based on InAs Quantum Dots,” were published
online recently by the journal Nano Letters. The
paper also will appear in a forthcoming issue of the journal’s
print edition. The U.S. Air Force Office of Scientific Research
funded this study. The paper is available online at: http://pubs.acs.org/doi/abs/10.1021/nl100081j
The detectivity of an infrared photodetector is determined
by how much signal it receives, divided by the noise it
receives. The current state-of-the art in photodetectors is
based on mercury-cadmium-telluride (MCT) technology, which has
a strong signal but faces several challenges including long
exposure times for low-signal imaging. Lin said his new study
creates a roadmap for developing quantum dot infrared
photodetectors (QDIP) that can outperform MCTs, and bridge the
innovation gap that has stunted the progress of infrared
technology over the past decade.
The surface plasmon QDIPs are long, flat structures with
countless tiny holes on the surface. The solid surface of the
structure that Lin built is covered with about 50 nanometers –
or 50 billionths of a meter – of gold. Each hole is about 1.6
microns – or 1.6 millionths of a meter – in diameter, and 1
micron deep. The holes are filled with quantum dots, which are
nanoscale crystals with unique optical and semiconductor
The interesting properties of the QDIP’s gold surface help
to focus incoming light directly into the microscale holes and
effectively concentrate that light in the pool of quantum dots.
This concentration strengthens the interaction between the
trapped light and the quantum dots, and in turn strengthens the
dots’ ability to convert those photons into electrons. The end
result is that Lin’s device creates an electric field up to 400
percent stronger than the raw energy that enters the QDIP.
The effect is similar to what would result from covering
each tiny hole on the QDIP with a lens, but without the extra
weight, and minus the hassle and cost of installing and
calibrating millions of microscopic lenses, Lin said.
Lin’s team also demonstrated in the journal paper that the
nanoscale layer of gold on the QDIP does not add any noise or
negatively impact the device’s response time. Lin plans to
continue honing this new technology and use gold to boost the
QDIP’s detectivity, by both widening the diameter of the
surface holes and more effective placement of the quantum
“I think that, within a few years, we will be able to create
a gold-based QDIP device with a 20-fold enhancement in signal
from what we have today,” Lin said. “It’s a very reasonable
goal, and could open up a whole new range of applications from
better night-vision goggles for soldiers to more accurate
medical imaging devices.”
Co-authors of the paper are Rensselaer Senior Research
Scientist James Bur, graduate student Chun-Chieh Chang, and
Research Associate Yong-Sung Kim; Yagya D. Sharma, Rajeev V.
Shenoi, and Sanjay Krishna of the Center for High Technology
Materials at the University of New Mexico, Albuquerque; and
Danhong Huang of the Space Vehicles Directorate at the Air
Force Research Laboratory, Kirtland Air Force Base.
For more information on Lin’s research, visit:
For information on Lin’s “darkest material” and solar panel
Contact: Michael Mullaney
Phone: (518) 276-6161