Unidirectional Optical Coupling For Plasmonic Waveguide Based On Metallic-Dielectric High Contrast Gratings

Based on the metallic-dielectric high contrast gratings, we proposed two new different schemes to achieve the unidirectional coupling of incident free-space light into the plasmonic waveguides. Using the cascaded metal-air sub-gratings (structure 1) or metallic-dielectric subwavelength periodic gratings (structure 2), the ultra-broadband and wide-angular SPPs excitation could be both achieved. The operation principle and performance of the structures are analyzed and discussed, respectively.