Figure 3.

(a) Measured asymmetry parameter, a, as a function of the normalized frequency parameter, V, for every combination of d and λ tested (color-coded for wavelength as indicated in the legend). V was calculated for each data point as a weighted average over the corresponding fluorophore’s emission spectrum, resulting in the horizontal error bars shown. Vertical error bars represent the deviation of a within the measurements. (b) Graphic representation of how the asymmetry parameter is defined (see main text for details; axes are the same as those in Figure 2d). One expects a = 1 for a perfectly symmetric peak, a = 0 for an infinitely long, nonlightguiding nanowire, and a ≈ 0.2 for a nonlightguiding wire about 3.5 μm long, observed under confocal illumination. Examples of how the parameter a is determined are given in the Supporting Information Section 7.