Additive Nanostructured Arrays for Broadband Anti-Reflectivity

Triton proposes to develop a high throughput additive nanofabrication process to produce nanostructured arrays on larger area infrared optical elements, both flat and curved. Nanostructured surfaces on visible and near infrared optics have demonstrated superior performance and have been implemented in a variety of military and commercial applications. Affordable production of large-area nanostructured surfaces on infrared optics, especially on curved surfaces, however, has not been successful, primarily due to materials limitations in mid and long wavelength-infrared wavelengths. The selected nanofabrication process will have ~50 nm resolution in the x-, y- and z-dimensions and patterning speed of more than 10-100 cm2/hour, similar the speed of deep-UV patterning processes yet suitable for application to curved surfaces.   In Phase I, we will model the required dimensions of nanostructured arrays, such as pitch, diameter and height (aspect ratio) of the micro- or nano-protrusions, to meet the program goal of <1% reflectance across the entire infrared band at wide angles of incident. Using the resulting dimensional requirements, we will validate our additive nanofabrication approach by performing a selected set of experiments to demonstrate the feasibility of producing nanostructured arrays with controlled geometry on flat substrates. In the Phase I Option, we will further optimize the designed nanostructured arrays via modeling simulation by considering manufacturing tolerances of the nanofabrication process, targeting ±50 nm. We will also establish nanofabrication process to produce nanostructured arrays on curved surfaces.  In Phase II, we will fully optimize the nanofabrication process to generate nanostructured broadband antireflection coatings on flat and curved substrates, followed by antireflection coatings on IR optical elements.  We will also design and apply a method of durability enhancement to protect nanostructured surfaces from fouling and damaging during handling. Further, we will measure infrared reflectance at various angles of incident, up to 60°.  A set of infrared optic elements with nanostructured surfaces will be produced and made available to the Army for testing.