Angle-sensitive device could improve photography and solar energy harvesting
Weishun Xu and Yuhao Zhang
Like a traffic cop directing cars, a layered stack of transparent materials permits light arriving from only a single direction to pass through. Such angle-sensitive filters could improve cameras and telescopes or allow solar cells to convert sunlight into energy more efficiently.
People have created effective light filters for thousands of years. Stained glass, for instance, filters light by color, allowing only a single shade to shine through while reflecting light at other wavelengths. But scientists have had trouble filtering light based on the angle from which it arrives.
In creating a directional light filter, MIT physicist Yichen Shen and his team knew that for the interface between any pair of materials, light arriving from one specific angle, known as the Brewster angle, can simply pass through unimpeded — it won’t get reflected or bent.