Researchers from CIC nanoGUNE (San Sebastian, Spain), in collaboration with the Donostia International Physics Center (DIPC, San Sebastian, Spain) and Kansas State University (USA), report in Science the development of a so called 'hyperbolic metasurface' on which light propagates with completely reshaped wavefronts. This scientific achievement towards a more precise control and monitoring of light is highly interesting for the long run technological challenge of miniaturizing optical devices for sensing and signal processing.
Optical waves propagating away from a point source typically exhibit circular (convex) wavefronts. "Like waves on a water surface when a stone is dropped," explains Peining Li, EU Marie Sklodowska-Curie fellow at nanoGUNE and first author of the paper. The reason of this circular propagation is that the medium through which light travels is typically homogenous and isotropic i.e. uniform in all directions.
Scientists had already theoretically predicted that specifically structured surfaces can turn the wavefronts of light upside down when it propagates along them. "On such surfaces, called hyberbolic metasurfaces, the waves emitted from a point source propagate only in certain directions and with open (concave) wavefronts," explains Javier Alfaro, PhD student at nanoGUNE and co-author of the paper. These unusual waves are called hyperbolic surface polaritons. Because they propagate only in certain directions, and with wavelengths that are much smaller than that of light in free space or standard waveguides, they could help to miniaturize optical devices for sensing and signal processing.
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