Fig. 4
Waveguiding properties including a mode area Am (left y-axis) and normalized mode area Am/λ2 (right y-axis), b propagation length Lm, and c figure of merit (FOM) of the PEPP and SPP with a MNW diameter of 50 nm. Compared to the monotonic behaviors of the SPP, the PEPP is able to exert its full strength for energy confinement in the exciton-like region (blue-filling area in c), while is capable of achieving excellent FOM in the SPP-like region (non-filling area in c). Blue star: maximum confinement. Green diamond and square: local maximum FOMs. The diameter for the Ag MNW here is 50 nm