A new angle on controlling light
[Philip Lelyveld comment: this could become the new privacy screen technology.]
But now, for the first time, MIT researchers have produced a system that allows light of any color to pass through only if it is coming from one specific angle; the technique reflects all light coming from other directions. This new approach could ultimately lead to advances in solar photovoltaics, detectors for telescopes and microscopes, and privacy filters for display screens.
The new structure consists of a stack of ultrathin layers of two alternating materials where the thickness of each layer is precisely controlled. “When you have two materials, then generally at the interface between them you will have some reflections,” Soljačić explains. But at these interfaces, “there is this magical angle called the Brewster angle, and when you come in at exactly that angle and the appropriate polarization, there is no reflection at all.”
While these experiments were done using layers of glass and tantalum oxide, Shen says that in principle any two materials with different refractive indices could be used.
See the full story here: http://web.mit.edu/newsoffice/2014/a-new-angle-on-controlling-light.html