Ultrahigh nonlinear nanoshell plasmonic waveguide with total energy confinement

Dielectric nonlinear waveguides have reached their maximum potential in achieving high nonlinearity due to the limitation of mode confinement beyond the diffraction limit. We theoretically demonstrate that a plasmonic waveguide consisted of a nonlinear subwavelength core coated by a metallic nanoshell can achieve ultrahigh nonlinearity and complete mode confinement. Our results show that the subwavelength nanoshell plasmonic waveguide can possess an ultrahigh Kerr nonlinearity up to 4.1 × 104W-1m-1 with nearly 100% of the mode energy residing inside the waveguide at λ = 1.55 μm. The optical properties are explored with detailed numerical simulations and are explained in terms of their dispersive properties.