Development of nanostructure based antireflection coatings for EO/IR sensors

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 and beyond to 1.8 microns. One of the critical technologies that will enhance the EO/IR sensor performance is the development of high quality nanostructure based antireflection coating. 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 250 nm to 2500 nm and 0° to 40° angle of incidence. These nanostructure AR coatings have shown to enhance the optical transmission in the band of interest and minimize the reflection loss to less than 3 percent substantial improvement from the thin film AR coatings technology.