SEAS researcher Noah Rubin told Photonics Media that one of the most compelling aspects of metasurface optics is that you can embed very interesting polarization functionality into the optics.



“The reason that we can do that is because on each point of the metasurface we can design something that has tunable birefringence,” Rubin said. “We can tune the birefringence at each point in an array, and if this birefringence is tuned suitably from one point in an array to another, you can design a very new type of optical element.”



Birefringence is the separation of a light beam as it penetrates a doubly refracting object into two diverging beams, commonly known as ordinary and extraordinary beams.



Under the direction of Federico Capasso, lead researcher, and Robert L. Wallace, professor of applied physics at Harvard, members of the Capasso Group have successfully encoded multiple holographic images in a metasurface that can be unlocked separately with different polarized light.



“The novelty of this type of metasurface is that for the first time we have been able to embed vastly different images that don't look at all like each other — like a cat and a dog — and access and project them independently using arbitrary states of polarization,” Capasso said.



