High‐Efficiency Generation of Vectorial Terahertz Beams via Surface‐Wave‐Excited Dielectric Metasurfaces

ABSTRACT Generating pre‐designed vectorial beams via on‐chip devices can yield many fascinating applications, but traditional diffraction‐based devices are bulky and inefficient. While plasmonic metasurfaces exhibit ultra‐compact sizes and deep‐subwavelength resolutions, their working efficiencies are limited by metallic losses. Here, we propose a generic design for highly efficient, ultra‐compact dielectric metasurfaces that generate tailored vectorial beams under surface‐wave (SW) excitations, experimentally validated in the terahertz (THz) regime. We first experimentally characterize the basic dielectric meta‐atom, and then demonstrate a benchmark meta‐device that, under the SW excitation, can generate a circularly polarized focused beam. We next realize two dielectric meta‐devices, each consisting of two subsets of meta‐atoms responsible for generating two pre‐designed circularly polarized beams with opposite helicity, with their interference forming the target vectorial beams. Our experiments show that these two meta‐devices can generate an azimuthally polarized Bessel beam and a vectorial multifocal holographic image, respectively. We experimentally show that the present dielectric meta‐system exhibits significant improvement in the relevant frequency band compared to its metallic counterpart, and numerically demonstrate that it exhibits an absolute working efficiency as high as 92%. Our study paves the way to realize many on‐chip applications with high efficiencies, such as biological sensing, displays, image multiplexing, and beyond.