Features of a dielectric-metal-dielectric plasmonic waveguide with a double grating

We report the results concerning the theoretical optimization of a surface plasmon-polariton based waveguide at the optical communication wavelength of 1.55 μm. In particular, the effect of metal thickness and grating depth on the excitation of long-and short-range surface plasm on polaritons in a dielectric/metal/dielectric structure are considered. It is shown that the coupling between these modes increases as the metal thickness decreases with the tendency of modes to overlap when the grating depth and metal thickness are reduced to values of respectively 50 nm and 25 nm. Also, the attenuation and confinement in these waveguide structures are inspected theoretically as the thickness of the three most used metals (Ag, Au and Al) is varied. The results confirm the established requirement of a trade-off between high confinement and low loss.