Additive Nanostructured Arrays for BBAR

U.S. Army sensor systems are complex and include many optical elements of different infrared lensing materials (Ge, ZnS, GaAs, and CaF2) to fully compensate for the optical aberrations over the broad 3-12 micron band.  Typical anti-reflective (AR) interference coatings are employed on the infrared optics to reduce Fresnel reflections.  However, broadband AR (BBAR) interference coatings for 3-12 micron band are expensive, time consuming, and the reflectivity is sensitive to angle of incidence and polarization.  The proposed work will design, model and demonstrate proof-of-concept methods of creating additive nanostructured arrays for BBAR on infrared optics.  The nanostructured optical elements on the lens surface will reduce the reflection below 1% in the 3-12 micron band at incident angles of up to 60°.  Our novel anti-reflective surface will consist of growing a random arrangement structure of features in sub-wavelength scale size and depth.  This new additive method will be applicable in a short process time and at low cost to uncoated infrared optics 12-155mm in diameter and with a curvature of twice the radius.  The innovative additive manufacturing approach will be investigated in details and plans to develop and fabricate prototypes during the Phase II effort will be reported.