Durable broadband ultralow index fluoropolymer antireflection coatings for plastic optics

Durable broadband antireflection (AR) coatings remain an ongoing challenge for plastic optics used in a wide range of applications. Here, we show that glancing angle deposition of a commercial fluoropolymer can be used to fabricate extremely durable ultralow index AR coatings that reduce the solar spectrum-averaged (400 < λ < 1600 nm) reflectance of acrylic and polycarbonate plastic to <1% over a wide range of incidence angles up to ~40°. The coatings feature strong adhesion and exhibit outstanding resistance to heat, humidity, dirt, ultraviolet light, outdoor exposure, solvents, acids, bases, abrasion, and repeated bend/compression cycling. They are successfully applied to f/1 curved lens surfaces as well as acrylic Fresnel lenses, where coating both sides increases the solar spectrum-averaged transmittance from 92% to 98%. These results represent a significant development for plastic optics commonly used in solar concentrators as well as more generally for broadband AR applications that demand extreme environmental, chemical, and mechanical durability.