▎ 摘　　要

Strong confinement and long-range propagation of electromagnetic energy are longed for when designing efficient miniaturized photonic devices. Here, a graphene-coated nanowire with a drop-shaped cross section is proposed for guiding graphene surface plasmon polaritons to demonstrate an extremely long propagation length (1 mm) with ultra-strong mode confinement (10 nm), which results from the distinctive mode field distribution caused by both the top and bottom arcs of the waveguide. The combination of nanoconcentration and long-range propagation makes the waveguide very useful in nanophotonics, bio-photonics, and highly integrated photonic circuits. (C) 2017 Optical Society of America