Two regimes of nanofocusing of the surface plasmon-polariton wave at the vertex of the metal micropoint

Nanofocusing of electromagnetic energy of the optical range near a microscale sharp cone tip on a metallic surface of the convergent surface plasmon-polariton wave is considered. Two regimes of focusing, which differ by a type of in the peculiarity of the electric field, are found. A transition from one regime to the other upon changing the apex angle of the tip is considered.