Enabling large-scale fabrication of Broadband Angular-Range Selective Film (BASM)

The ability to control the propagation direction of light is a longstanding scientific and engineering goal. Until now, the production of large-scale low-cost polymeric structures that operate across the visible wavelength range while exhibiting angular-range selective transparency and reflectivity has been elusive. 

At Lux Labs, we detail a novel polymer-enabled large-scale fabrication method for producing these films based on stacking multiple one-dimensional photonic crystals, with specifically engineered periodicities, to produce a band gap across a wide spectral range. 

In the recently published paper in ACS Nano (Impact Factor 2020: 15.881), we demonstrate that this method can produce films with broadband transparency at a range of incident angles near normal while at the same time showing reflectivity at larger viewing angles. Experimental results show that these films have high transmissivity (~80%) at a range of angles centered at normal incidence, and high reflection (~75%) at incident angles at and above 60° across the visible spectrum.

The fabrication method is very economical and can produce large scale films that have practical commercial application in high-efficiency solar energy conversion devices (light trapping), privacy screens, and optical detectors with enhanced signal-to-noise ratios.