TM mode in a cylindrical hybrid plasmonic waveguide with large propagation length.

This study reports on a cylindrical hybrid plasmonic waveguide (CHPW) consisting of a high-index dielectric core, a sandwiched low-index dielectric layer, and a metal cladding. The CHPW supports the TM mode with a radially polarized transverse component of the electric field. Optical fields can be significantly enhanced in the sandwiched low-index dielectric region with nanoscale thickness down to 5 nm, and tight mode confinement with the same order of the normalized mode area compared with that of the plasmonic waveguide is achieved. Moreover, the mode propagation loss is well compensated by adjusting dimensions of the waveguide to obtain a longer propagation distance. The calculated figure of merit reaches a value several times greater than that in the similarly reported structure. The results indicate that this novel type of hybrid structure can support the limited propagation of a radially polarized mode with good confinement and low loss, consummate the whole system of manipulating the cylindrical vector beams, and show great potential of applications for various integrated nano-photonic devices.