Figure 2

(a) The maximum total electric field enhancement (defined as |M| = |Eloc/Ein|) as a function of wavelength and cone angle of the tip. (b) The total electric field distribution of the plane between the tip and substrate, where ϕ = 20° and the incident wavelength is 632.8 nm. (c) The maximum vertical electric field enhancement (|Mz|) and (d) the maximum horizontal electric field enhancement (|Mxy|) as a function of wavelength and cone angle of the tip.