Figure 3: Nanoantenna fluorescence images.

The top panels show SEM images of the nanoantenna arrays for reference, (a) for Si and (e) for Au. The four images below are fluorescence images corresponding to Si (left) and Au (right). Scale bar, 2 μm. Reference panels (b) and (f): fluorescence images without the heating laser turned on. (b) Silicon nanoantennas produce enhanced fluorescence while gold antennas (f) slightly enhance the fluorescence emission (see Supplementary Fig. 4 and Supplementary Note 4 for explanation). (c) and (g): Fluorescence images with the heating laser on at 6 mW μm⁻². The color scale bar is the same for all the fluorescence images. Bottom panels: Intensity profiles taken from the rows indicated as lines in the fluorescence images. The intensity clearly drops for the gold antennas (h) but remains nearly constant for the silicon ones (d). The Nile Red molecules around the gold antennas are affected by drastic changes in temperature, leading to the observed intensity drop. In all the fluorescence images the background average value has been subtracted for better displaying.