Anti-reflection coating of large-format lenses for sub-mm applications

We have recently developed a repeatable and reliable technique for anti-reflection coating large lenses, suitable for use at sub-mm wavelengths. Small lenses have been coated using this technique, and are currently flying on-board Herschel-SPIRE and Planck-HFI. We have recently coated much larger, highly-curved lenses (up to 380 mm diameter) for the EBEX and Polarbear cosmic microwave background (CMB) experiments. In this paper, we present details of the coating technique, experimental results of coated samples, and comparison of the results to theoretical predictions. We also present an indication of their technology readiness level (TRL) for future space applications such as B-Pol.