Effect of Mirror Characteristics on Critical Coupling in Plasmonic Nanostructures

Plasmonic nanostructures have been used in various non-destructive sensing and modulation applications. The efficiency of plasmonic structures can be tuned by controlling their net optical absorption and near-field enhancement. In the current study, we numerically investigate the effect of mirror characteristics on absorption and near-field enhancement in critically coupled plasmonic structures. We explore structures with metallic mirrors and dielectric Bragg reflectors (DBR) and show that the optical response can be enhanced by a judicious choice of spacer thickness and operating wavelength. The results presented in this study provide a roadmap for designing plasmonic substrates with enhanced efficiencies.