Spatial Coupled-mode Theory Based On Surface Plasmon Polariton

As the filed of surface plasmon grows widely, extensive attentions have been attracted by the spatial coherent control of surface plasmon polaritons (SPPs). In order to describe the spatial properties of SPP, we develop the spatial coupled-mode theory for the SPP excitation. The theory engages the coupling among input, output waves and mode of SPP-excitation structure. We show that the coupling coefficients are constrained by energy conservation and time-reversal transformation. To validate the theory, we apply the theory to a Otto-configurated metal surface and a symmetric metal grating to get the reflection and phase of such structure, and compare the results to numerical methods, such as the transfer matrix and the finite-element method. Finally, as the application of the spatial coupled-mode theory, we design an angular selectivity metal surface based on the spatial mode coupling and interference.