Hybridization of plasmonic and photonic modes for subwavelength optical confinement with longer propagation and variable nonlinearity

Mode hybridization of photonic and plasmonic modes in hybrid plasmonic (HP) waveguide is proposed to achieve low-loss sub-wavelength (nano-scale) optical-confinement with variable optical nonlinearity. Origin and analysis of the mode hybridization is presented to come up with an efficient design of HP-waveguide. The coupled-mode-theory is used to calculate the coupling between the SPP and photonic-mode for the estimation of mode character. The mode-coupling can be modified by controlling the associated evanescent field which is responsible for the longer propagation of HP mode in the dielectric. The coupling strength (for HP mode) in Si/SiO2/Ag system is found to be 52%. The nonlinear coefficient for a 10-nm thick dielectric remains at 3.8×107 km−1 w−1 with propagation length of 154-μm and modal area of 0.0009/μm2. The nonlinearity of the guided mode is shown to be variable with change in waveguide width. The guiding characteristics are shown to be effectively controlled by the high-index region under the dielectric layer to provide flexible nonlinearity. The propagation loss for Si-based HP-waveguide is 0.028-dB/μm. Coupling and propagation characteristics of the HP waveguides are calculated analytically as well with Finite-Element-Method.