Periodically structured plasmonic waveguides

摘要

We study surface plasmon polariton (SPP) guiding structures, which are a modification of the Metal-Insulator-Metal (MIM) waveguide. The designs are constructed by introducing a periodic modulation in a MIM waveguide, with a glass core and silver claddings. This periodic modulation is created either by causing periodic indentations in the silver slabs encompassing the glass core, or by increasing the glass spacer material in certain periodic locations. Our objective is to achieve long range sub-wavelength waveguiding with vast dispersion engineering capabilities. We employ the Finite Difference Time Domain Method (FDTD) with the Auxiliary Differential equation method (ADE) for the calculation of the dispersion relation of the guided modes, as well as the real time propagation of electromagnetic energy through the waveguide. The analysis of the mode profile and real time propagation suggests that the guiding mechanism in the examined structures is based on the electromagnetic (EM) coupling between the slit plasmon modes. These, - depending on the design-, exist in the groves between the silver plates or in the larger areas of the glass core spacer. Put it different, the guiding mechanism in the examined SPP waveguide designs is analogous to the EM energy transfer along metallic nanoparticle chains.