Analysis of propagation characteristics in the surface plasmon polariton gap waveguides by method of lines

A numerical study of the complex propagation constants of a surface plasmon polariton gap waveguide (SPGW) that was nanometric in size is performed by the method of lines (MoL). The validity of the code based on the MoL is examined by comparing the present results with those calculated using a volume integral equation, which is a completely different numerical technique from the MoL. The dependences of the complex propagation constants on the sizes of the SPGWs are investigated in detail and the fundamental propagation characteristics of SPGWs are revealed. Three kinds of SPGW structures (slab-slab, slab-plate and staggered slab-slab) are examined with a view to reducing the attenuation constants and the spot size to nanometric size. It is found that the nanometric field confinement can be controlled by using the staggered slab-slab structure of SPGW without a large change in the propagation constants. (C) 2009 Optical Society of America