Metamaterials to bridge propagating waves with surface waves and control electromagnetic waves

In this work, we demonstrate theoretically and experimentally that a specific gradient-index meta-surface can convert a PW to a SW with nearly 100% efficiency. Distinct from conventional devices such as prism or grating couplers, the momentum mismatch between PW and SW is compensated by the reflection-phase gradient of the meta-surface, and a nearly perfect PW-SW conversion can happen for any incidence angle larger than a critical value. Experiments in the microwave region, including both far-field and near-field characterizations, are in excellent agreement with full-wave simulations. Based on gradient metasurface´s idea, we also realized a gradient meta-surface supporting high-efficiency anomalous reflection for near-infrared light and a flat focusing lens for microwave.