Plasmonic Bloch oscillations in metal heterowaveguide superlattices and metal waveguide arrays with graded width of guiding regions

We study the propagation of surface plasmon polaritons (SPPs) in nanoscale metal heterowaveguide superlattices and metal waveguide arrays (MWGAs), both realized by gradually increasing the width of guiding regions. Theoretical analysis of the transmission properties of SPPs passing through the metal heterowaveguide superlattices by the transfer matrix method reveals that the SPPs minibands and minigaps in the frequency domain exhibit a spatial tilting, implying the appearance of plasmonic Wannier-Stark ladders and the existence of time-resolved plasmonic Bloch oscillations (BOs) in the superlattices. The analytic results of the coupled wave theory show that SPPs periodically oscillate transversely in the MWGAs under conditions of multiple waveguide excitation as the behavior of spatial BOs. Numerical simulations of the dynamic evolution of SPPs in the superlattices and MWGAs by the finite-difference time-domain method demonstrate the analytical predications well. (C) 2009 Optical Society of America