Hybridly Polarized Nanofocusing of Metallic Helical Nanocone

We present a metallic helical nanocone, which is a combination of a helical structure and a conic structure. Surface plasmon poloritons are excited at the boundary of the bottom of the helical nanocone, then guided and rotated by the groove provide by the helical structure on the nanocone, and finally, squeezed to the apex of the tip to form a highly localized strong electromagnetic field. The intensity distributions and polarization of the electric fields generated by the metallic helical nanocone are simulated with 3-D finite-difference time-domain method, which indicate that highly confined and hybridly polarized optical fields can be produced at the apex of the metallic helical nanocone.