Nondiffracting beam emission from hyperbolic metasurfaces

We demonstrate highly directive and transversely confined emissions from hyperbolic metasurfaces (HMSs) to free-space. The generation of such beams is attributed to the narrow hyperbolic isofrequency contour, such that only propagating waves with their wavevectors near normal incidence can transmit through the medium. The directions of transmitted waves' Poynting vectors are altered by the medium and become parallel to the propagation direction, resulting in the generation of nondiffracting beams. We also suggest a realization of the proposed HMS using a layered silver-dielectric structure for optical wavelengths.