Field-enhanced nanofocusing of radially polarized light by a tapered hybrid plasmonic waveguide with periodic grooves.

This study reports the field-enhanced nanofocusing of radially polarized light by tapered hybrid plasmonic waveguide (THPW) with periodic grooves. The THPW consists of a conical high-index dielectric cone, a sandwiched low-index dielectric thin layer, and a metal cladding. The axially symmetric 3D finite element method is used to investigate the nanofocusing effect. Under radially polarized illumination at 632.8 nm, strongly enhanced nanofocusing occurs. The hybrid plasmonic structure effectively reduces the energy loss and improves the field enhancement nearly 554 times. Furthermore, periodic grooves are constructed on the metallic surface of the THPW, satisfying the phase-matching condition, and they couple the light energy from the inside to the outside. Finally, an optimized nanofocusing performance with field enhancement of approximately 1810 times is obtained. The results offer an important reference for designing related photonic devices, and the proposed scheme could be potentially exploited in the application of light-matter interactions.