Subwavelength focusing with a corrugated metallic plate

In this paper, we presented a device that can focus electromagnetic field with subwavelength resolution. The device consists of a single slit in a corrugated metallic plate. The input face of the plate features a periodic corrugation which enhances transmission through the slit, while the output face of the plate features a non-periodic corrugation which forms the subwavelength focus. Simulation and free-space measurements are reported at 10 GHz, confirming the corrugated plate's ability to form a subwavelength focus. In the experiments, the input face of the plate was illuminated with a Gaussian beam, and a subwavelength focus was formed at a distance lambda/15 from the output face of the plate.