Localization of surface plasmon by using a metal-coated axicon prism

We present the localization of surface plasmon using a metal-coated axicon prism and its application to fluorescence scanning microscopy. The cone angle of the axicon prism is designed such that a plane wave incident on the prism can excite surface plasmon on the side surface of the prism. Since the surface plasmon propagates toward the apex of the prism, an extremely high enhancement of the electric field is expected. The proposed technique can overcome the trade-offbetween the field-enhancement factor of surface plasmon and the resolution limit due to the propagation of surface plasmon. The experimental result obtained with the localized surface plasmon is also demonstrated.