# Angle-Resolved Fluorescence of a Dye Coupled to a Plasmonic Nanohole Array
## 3 Results  
The measured ATTO700 dye fluorescence spectra of the PEF platform are presented in Figure 3. The configuration with the pump on the front side, panels (a) and (b) of Figure 3, shows a systematically higher intensity compared to pumping from the back side. Considering the front/back configuration, looking at pumping angle \(\alpha\), panel (a), Figure 3, no significant spectral changes in the curves are noted. On the other hand, the peak intensity decreases with \(\alpha\), undergoing an interruption between 15\({}^{\circ}\) and 20\({}^{\circ}\). Considering the variation in collection angle \(\beta\), instead, in panel (b), Figure 3, the peak intensity is decreasing. When the pumping is performed from the back, panel (c), Figure 3, the fluorescence peak intensity increases with the pumping angle \(\alpha\), 0\({}^{\circ}\) to 20\({}^{\circ}\), and then decreases. Considering the variation with respect to the collection angle \(\beta\), panel (d), Figure 3, the peak intensity also shows a decrease for this configuration. Overall, the peak spectral position is mainly unaffected, displaying the emission maximum near 730 nm, regardless of the pumping angle for both the pumping/collection configurations. On the other hand, considering the dependence on the collection angle \(\beta\), the peak spectral position remains unchanged for the front/back configuration and exhibits a blue shift in the back/front one. Consistent behavior of the fluorescence emission spectra is also observed when pumping and collection both persist on the same side (front/front or back/back). Figure 4 reports the results obtained for these configurations. In this case, the front/front measurements exhibit the largest fluorescence intensities, whereas the back/back ones are roughly one-third lower in intensity. Also, in this case, the spectral shape remains substantially unchanged when the pumping angle is varied, displaying a maximum of around 730 nm. Starting from the lowest collection angle of 10\({}^{\circ}\), the fluorescence maximum intensity decreases down to 45\({}^{\circ}\) for the front configuration (panel (a), Figure 4), while maintaining its value up to 30\({}^{\circ}\) to lower again for the back/back configuration (panel (c), Figure 4). A shift and a reshape of the spectral curves can also be observed in this case by varying the collection angle. In fact, for both the front/front and back/back configurations, panels (b) and (d) of Figure 4, respectively, the fluorescence spectra show a redistribution of the spectral weight toward lower wavelengths, exhibiting a blue shift of the fluorescence maximum. So, by comparing the results corresponding to the different measurement configurations, it results that the side on which the pumping occurs determines the intensity of the response. Instead, the spectral shape is mainly affected by the collection angle, independently of the chosen configuration. The dispersion of SPPs can be identified by comparing the experimental R behavior and the theoretical SPPs model (see Appendix A.1), depicted by the dotted curves in Figure 5. Here, the black lines in panel (d) can be ascribed to the SPPs related to the Au/SiO\({}_{2}\) interface and can be clearly observed when measuring from the back. Figure 3: Variable-angle fluorescence spectra of ATTO700 dye measured on the PEF platform by impinging and collecting on opposite sides. Panels **(a,b)** report the spectra collected when illuminating from the front side and collecting from the back one. Panels **(c,d)** refer to the pumping on the back side and collection from the front one. Spectra are shown as a function of the pumping angle \(\alpha\) in panels **(a,c)**, in contrast to the collection angle \(\beta\) in panels **(b,d)**. To better highlight the complex plasmonic response of the GNA, which can be associated with maxima and minima in the optical spectra, Figure 5 reports the second derivative of the reflectance (R) spectra (see Appendix A.2, Figure A1) as a function of the incidence angle [32].