From a flat mirror, designer light—An optical phenomenon that defies laws of reflection and refract…

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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.

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“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.”

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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.

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