Broad-angle and efficient unidirectional excitations of surface plasmons with dielectric-coated subwavelength metallic periodic nanoslits

We experimentally demonstrate a mechanism of broad-angle and efficient unidirectional excitations of surface plasmon polaritons (SPPs). By combining the plasmonic critical angle phenomenon and grating effects, unidirectional excitation of SPPs with broad incident angular width up to 25° and high extinction ratio better than 10 dB was experimentally demonstrated. A peak extinction ratio of 17 dB was achieved. The proposed structure was also numerically simulated showing good agreement with experimental measurement. The operation principle was numerically and experimentally clarified through compare and analysis.