Figure 3 . Sensitivity, fabrication complications, losses, and
footprint comparison of plasmonic WGs with dielectric or hybrid
plasmonic WGs.
The main benefit of the plasmonic WGs is that the operational wavelength
of light does not influence its size. This makes it possible to create
plasmonic WGs with lengths on the order of several tens of nanometers,
something that is not feasible with dielectric WGs. Additionally,
exceptionally strong light confinement and effective interaction with
nanomaterials that have various special properties become conceivable. A
three-dimensional plasmonic mode converter is necessary since such WGs
cannot readily be included in optical integrated circuits. The plasmonic
WG is made up of a MIM WG, a Si-wire WG, and a plasmonic mode converter
section. On an SOI substrate, the silicon ridge WG, and the silicon
section of the plasmonic mode converter are constructed, followed by the
formation of the metal components using electron beam lithography and
evaporation. This set of procedures makes use of standard methods for
fabricating nanostructures and is hence compatible with those applied to
other silicon photonic devices. For device integration, this makes it
possible to integrate with other optical components on the same
substrate. For a MIM WG with a core size of 50 nm × 20 nm, a plasmonic
mode converter with an air gap width of 40 nm has been developed as
shown in Figure 4 (a). The E-field distribution in the whole plasmonic
device and at different segments of the WG is presented in Figure 4 (b).