# Corner Reflector Plasmonic Nanoantennas for Enhanced Single-Photon Emission
## 3 Results and Discussion
In addition to the impact of the better figures for the \(f_{R}\) and \(f_{L}\) values in the case of silver NAs, the lower values of \(G\) obtained in the case of gold CR NAs were also due to the fact that \(L/\lambda_{M}\) was smaller in the case of gold. The incorporation of the CR in the proposed hybrid NAs is targeted to shape the radiation produced by the dipole-NP feeder system. It is important to evaluate the possible interaction effects between the CR and the feeder. First, we calculated the properties of a \(W=80\) nm thick CR when the emitter-NP was replaced by a single dipole emitter feeder. Figure 12a,b compare the the directivities as a function of \(S/\lambda_{M}\) obtained with the CR NA with and without the spherical NP coupled to the dipole emitter. In the latter case, the position of the dipole emitter was centered at the origin. The results demonstrate that the spatial shaping of the emission obtained by using the CR is largely independent of the dipole feeding system employed, since the differences between the directivities obtained with and without the NP were negligible. Figure 12c,d display the Purcell and loss factors for silver and gold nanoantennas, respectively, in the same cases as the previous figures. The losses due to the CRs were much smaller that those obtained for a dipole coupled to a metal nanosphere and showed little dependence with respect to the position of the dipole emitter along the corner axis. For the case of silver CRs, the losses were negligible at \(\lambda=450\) nm. As regards the Purcell factor, we observed the same type of pattern as that shown in Figures 9 and 10 regarding the variation in \(f_{R}\) with \(S/\lambda_{M}\) due to the interaction of the dipole emitter with the CR plasmonic antenna, but the deviations from the unity were milder that those of the NP-emitter system and much smaller than those of the NP-emitter incorporated as a feeder system in the CR NA. In summary, whereas the CR alone was responsible for managing the directive properties of the hybrid NA, the strong plasmonic  
Figure 2:1 Radiation efficiency of silver (**a**) and gold (**b**) CR NA as a function of the normalized feeder position \(S/\lambda_{M}\) for four different reflector film thicknesses \(W\). interactions observed in the system, with large variations in \(f_{R}\), were found to be mediated by the spherical NP at the feeder arrangement. Figure 13 displays the plasmonic resonance wavelengths when the NPs were incorporated into the CR setup. These results illustrate the impact of NP-CR plasmonic interactions on the Purcell factor. Note that the distances between the feeder NP and the corner apex are unnormalized in these plots. The results obtained for spherical NPs, shown in Figure 2, exhibit minimal variation in the resonance wavelengths with respect to particle size and the distance between the NP and the emitter. In contrast, Figure 13 demonstrates that, for sufficiently large mirror thicknesses \(W\), there were significant shifts in the resonance wavelengths as the position of the feeder emitter-NP was moved along the corner axis. As \(S\) increased, there was an initial rise in \(\lambda_{res}\), followed by a sudden drop to approximately the resonance wavelength of the isolated NPs. This drop occurred for values of \(S\) near the minimum \(f_{R}\) in Figures 9 and 10, highlighting the relationship between these results and the interaction properties of the CR with the NP in close proximity. The modification of the emitter's fluorescence rate by the NA system is directly related to the local field enhancement (LFE) at the emitter's position due to the surrounding plasmonic environment [21]. To evaluate the LFE factor, the NA setup must be in receiving mode. Reciprocity [15,16] ensures that the antenna properties remain the same whether it is receiving or transmitting electromagnetic radiation. For these calculations, a linearly polarized plane wave, with the \(E\) field aligned along the \(Z\) axis, impinges on the NA along the \(Y\) axis in the reverse direction.