High efficient unidirectional surface plasmon excitation utilizing coupling between metal-insulator-metal waveguide and metal-insulator interface

A new structure is proposed, which can realize parallel coupling between metal-insulator-metal (MIM) waveguide and plasmon on metal-insulator (MI) interface. An example for wavelength of 680 nm shows the coupling efficiency can be high as 82%, with short coupling length of 1.2 µm. By using MIM waveguide with proper length, a unidirectional plasmon generator is realized. The generator shows excitation efficiency as high as 78%, with high extinction ratio as 1:170. It also shows a good tolerance for the wavelength. The results are of vital importance for optical integration and unidirectional plasmon excitation.