Substrate-Embedded Dipole Nanoantenna Arrays: Collective Optical Response

We have studied the optical properties of a regular array of plasmonic nanoantennas in the form of subwavelength metal spherical particles partly embedded in a metal substrate with a hollow gap between the particles and the substrate. Using gold, a representative plasmonic material, for the particles and the substrate, we have demonstrated that the nanoantenna array possesses two distinct resonances, which may be tuned by varying the parameters of the individual nanoantennas and the grating period. Particular attention is given to the scenario when the two resonances overlap producing an asymmetric Fano-like resonant feature in the array’s reflection spectrum. The possibility of using the nanoantenna array under study for refractometric measurements is considered. Apart from refractometry, the results obtained in this work can find application in the development of novel nanophotonic functional elements for concentration, enhancement and redistribution of the electromagnetic field.