http://news.harvard.edu/gazette/story/2011/09/from-a-flat-mirror-designer-light/From a flat mirror, designer light
An optical phenomenon that defies laws of reflection and refraction
Exploiting a novel technique called phase discontinuity, researchers at the Harvard School of Engineering and Applied Sciences (SEAS) have induced light rays to behave in a way that defies the centuries-old laws of reflection and refraction.
The discovery, published Sept. 2 in the journal Science, has led to a reformulation of the mathematical laws that predict the path of a ray of light bouncing off a surface or traveling from one medium into another — for example, from air into glass.
…
“By incorporating a gradient of phase discontinuities across the interface, the laws of reflection and refraction become designer laws, and a panoply of new phenomena appear,” said Zeno Gaburro, a visiting scholar in Capasso’s group who was co-principal investigator for this work. “The reflected beam can bounce backward instead of forward. You can create negative refraction. There is a new angle of total internal reflection.”
…
The researchers have already succeeded at producing a vortex beam (a helical, corkscrew-shaped stream of light) from a flat surface. They also envision flat lenses that could focus an image without aberrations.
…