Shape dependent holographic metasurfaces
One of the exciting application areas for optical metasurfaces is holography. Through a clever arrangement of meta-atoms we use metasurfaces to display almost any computer-generated hologram, allowing the display of high-resolution images, lensing or shaping the emission of an antenna.
Of particular interest here are conformable metasurfaces that can be applied to shaped objects and decouple the optical response from the object’s shape. For example, normally a reflective cylinder would result in a divergent beam, however, in previous work we have shown that through a conformable metasurface, this can be turned into a focused beam.
We have now taken this concept a step further, by creating a single metasurface that displays to completely different holographic images, depending on the shape of the underlying object. The figure below indicates our key result – when in a convex shape the metasurface displays two focal spots along a diagonal from the top left to the bottom right corner of the image, while in the concave configuration, the image displays three focal spots, along the opposite diagonal, i.e. from the bottom left to the top right.
This work was carried out in collaboration with the Synthetic optics and mm-Wave groups here in St Andrews and is published in the journal Advanced Materials Technology.