Friday, September 02, 2011
Playing with interfaces for optical fun and profit
A team at Harvard has published in Science a fun and interesting result. When light passes from one medium to another, there are boundary conditions that have to be obeyed by the electromagnetic field (that is, light still has to obey Maxwell's equations, even when there's a discontinuity in the dielectric function somewhere). Because of those boundary conditions, we end up with the familiar rules of reflection and refraction. Going up a level in sophistication and worrying about multiple interfaces, we are used to having to keep track of the phase of the electromagnetic waves and how those phases are affected by the interfaces. In fact, we have gotten good at manipulating those phases, to produce gadgets like antireflection coatings and dielectric mirrors (and on a more sophisticated level, photonic band gap materials). What the Harvard team does is use plasmonic metal structures to pattern phase effects at a single interface. The result is that they can engineer some bizarre reflection and refraction properties when they properly stack the deck in terms of phases. Very cute. I must confess, though, that since Federico Capasso was once my boss's boss at Bell Labs, I'm more than a little disturbed by the photo accompanying the physorg article.
Posted by Douglas Natelson at 2:31 PM