Figure 4. Sub-10 nm EM confinement in SOAs.

a, experimental extinction efficiency spectra of SOAs with 20 nm, 9 nm and 5 nm thickness SiO₂ spacer, collected for 50° incidence illumination. b, plot reporting the normalized electric field at the left extremity of the cavity (see inset) for 50° light incidence angle, as a function of the spacer thickness, in β and α resonance condition. c-e, normalized electric field (left plots) and Poynting vector distributions (right plots) of the β configuration inside the MIM cavity, at 50° light incidence condition, for three different spacer thicknesses: respectively 30 nm, 20 nm and 5 nm.