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EO/IR Nanosensors are being developed for a variety of Defense and Commercial Systems
Applications. These include UV, Visible, NIR, MWIR and LWIR Nanotechnology based
Sensors. The conventional SWIR Sensors use InGaAs based IR Focal Plane Array (FPA) that
operate in 1.0-1.8 micron region. Similarly, MWIR Sensors use InSb or HgCdTe based FPA that
is sensitive in 3-5 micron region. More recently, there is effort underway to evaluate low cost
SiGe visible and near infrared band that covers from 0.4 to 1.6 micron.
One of the critical technologies that will enhance the EO/IR sensor performance is the
development of high quality nanostructure based antireflection coating. Prof. Fred Schubert and
his group have used the TiO2 and SiO2 graded-index nanowires / nanorods deposited by obliqueangle
deposition, and, for the first time, demonstrated their potential for antireflection coatings by
virtually eliminating Fresnel reflection from an AlN-air interface over the UV band. This was
achieved by controlling the refractive index of the TiO2 and SiO2 nanorod layers, down to a
minimum value of n = 1.05, the lowest value so far reported
In this paper, we will discuss our modeling approach and experimental results for using oblique
angle nanowires growth technique for extending the application for UV, Visible and NIR sensors
and their utility for longer wavelength application. The AR coating is designed by using a genetic
algorithm and fabricated by using oblique angle deposition. The AR coating is designed for the
wavelength range of 400 nm to 2500 nm and 0° to 40° angle of incidence. The measured average
optical transmittance of an uncoated glass substrate between 1000 nm and 2000 nm is improved
from 92.6% to 99.3% at normal incidence by using a two-layer nanostructured AR coating
deposited on both surfaces of the glass substrate.
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