Layered Nanostructures for Broadband Antireflectivity

US Army sensor systems are complex optical instrumentation incorporating complex optical designs with multiple optical surfaces. To enhance the performance of such systems, it is critical to minimize reflections from the optical surfaces and enhance light transmission. Multi-layer anti-reflection coatings (ML-ARCs) are widely used in such optical systems to address this issue. Although well-designed ML-ARCs perform well, obtaining broadband anti-reflectivity for 3 µm–12 µm for large angles of incidence and polarization-insensitivity in a cost-effective manner is challenging. However, ARCs based on nanostructured arrays (NSAs) offer broadband, omnidirectional, and polarization-insensitive anti-reflectivity and also provide additional benefits such as anti-fogging. During Phase I, we propose to identify strategies for fabricating NSAs, and then demonstrate the feasibility of fabricating NSAs exhibiting broadband anti-reflectivity for large angles of incidence. Nanoparticles of the specified IR lensing materials will be fabricated. The size of the nanoparticles will be varied to obtain optimum performance. A bottoms-up fabrication technique will then be used to produce layered NSAs. The optical performance of these NSAs will be thoroughly evaluated for incidence angles up to 60°, and the reflectivity will be quantified. We will also investigate the nanoimprinting of gradient-index nanostructures for the proposed application.