Figure 7
Sequence of the materials used in the planar multilayer model employed to analyze the properties of the modes within the plasmonic taper section.
The various colors refer to the different materials involved (dark blue: silica (tsilica = 10 μm), magenta: ultrathin niobium film (tNb = 12.5 nm), dark green: Al2O3 (tAl2O3 = 80 nm), light green: liquid analyte). The blue curve is a schematic representation of the magnetic field components (Hy) of the TM-polarized hybrid plasmonic mode (even TM01-mode, mode amplitude and shape of the curve not to scale). The propagation direction is along the x-axis and the waveguide is translational invariant along the y-axis. The dashed red line indicates the symmetry plane at which the boundary condition ∂Hy/∂z = 0 is applied.
