controllable steering and tuning of surface plasmons on the metallic nano-film with nanoslits array

A scheme of steering and tuning surface plasmon wakes (sws) on the metallic nano-film (mnf) excited by a free-electron-beam is demonstrated. with a well-designed array of nanoslits etched in the mnf, the sws can be steered to propagate along the mnf in definite directions via a unique smith-purcell effect. both the frequency and direction of sws can be well controlled by adjusting the beam velocity and mnf parameters: the sw frequency can be tuned from the infrared to the ultraviolet, and the sws can propagate both forwardly and backwardly. these results indicate promising applications for surface plasmon devices on chip. and also the proposed scheme offer an effective way for nondestructive detections of the particle velocity and dielectric index.