# Corner Reflector Plasmonic Nanoantennas for Enhanced Single-Photon Emission
## 4 Conclusions  
The analysis of dipole-NP interactions, combined with CR integration, reveals important insights into the enhancement of radiative properties for silver and gold NPs. Knowing the fundamental behavior of NP interactions is crucial for understanding the modifications introduced by the incorporation of the CR in the system. Initially, isolated dipole-NP calculations without the CR showed trends consistent with previous theoretical and experimental studies, particularly regarding the variation in resonance wavelength, the radiative emission rate enhancement factor, and loss factor with silver and gold particle size and dipole emitter separation. This preliminary study established a set of parameters for the subsequent analysis of the CR. The results also suggest that silver NPs are more effective than gold NPs in enhancing radiative emission while maintaining lower loss factors.  
Integrating CRs into silver and gold NA systems leads to substantial improvements in directivity. The variation in directivity with respect to the normalized distance \(S/\lambda_{M}\) reveals that thicker metal films generally lead to more regular oscillatory patterns in directivity. At the first directivity maxima, significant gains in the radiative enhancement factor, \(f_{R}\), were also achieved with minimal increases in the loss factor, \(f_{L}\), leading to high gain figures of merit, \(G\). At the second directivity maximum, the CR mainly enhanced directivity, with the highest values of \(D\) corresponding to the global maxima of \(G\).  
Extending the corner length to \(L=3\) um demonstrated a saturation effect in the enhancement of directivity for both materials, with similar peak values achieved for the gold and silver CRs despite differences in their \(L/\lambda_{M}\) values. Meanwhile, the patterns for the variations in \(f_{R}\) and \(f_{L}\) closely resembled those found at \(L=1.5\) um. These findings highlight the localized nature of CR-induced enhancements near the apex. However, silver CRs exhibited larger shifts in their positions of the directivity maxima and minima with changes in \(W\). This resulted in the maximum gain for silver CR NAs at a metal thickness  
Figure 18: Nanoantenna gain as a function of the feeder position \(S\) normalized to the corresponding target wavelength for three different reflector film thicknesses when the length of the CR planes was increased to \(L=3\) μm. (**a**) Results for silver CR. (**b**) Results for gold CR.  
of \(W=40\) nm, rather than \(W=80\) nm, due to the alignment of the directivity maximum with a higher value of \(f_{R}\).  
Overall, the results indicate that silver CR NAs outperform gold CR NAs in terms of radiative enhancement and gain, offering more efficient light emission and directivity control for nanoscale optical applications, although different spectral windows are targeted by the choice of NA metal.  
The reflector angle selected for the analysis aligns with a typical value used in RF applications, corresponding to optimization for operation at the more favorable second gain maximum. The analysis reveals a strong metal-feeder interaction near the corner apex, suggesting the potential benefits of further exploring corner geometries to optimize the first gain maximum, which will be addressed in future works.  
This work was funded by the Spanish Ministerio de Ciencia e Innovacion (MCIN) under grant PID2020-119418 GB-I00, by the European Union NextGeneration EU under grant PRTRC17.I1, and by the Consejeria de Educacion, Junta deCastilla y Leon, through the QCAYLE project and grant VA184P24.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
The author declares no conflicts of interest.