Demonstration of unusual nanoantenna array modes through direct reconstruction of the near-field signal.

Abstract

We perform complex investigation of the distribution of electromagnetic fields in the vicinity of an array of silver nanoantennas, which can operate as an efficient light trapping structure in the visible spectral range. In theory, this array should support unusual collective modes that possess an advantageous distribution of local electric fields, ensuring both strong field localization beneath nanoantennas and a low level of optical losses inside the metal. Using an aperture-type near-field scanning optical microscope (NSOM), we obtain near-field patterns that show excellent agreement with the NSOM signal, directly reconstructed from rigorous numerical simulations using an approach based on the electromagnetic reciprocity theorem. The agreement between theory and experiment allows us to claim the first-time experimental verification of the existence of collective modes with such properties in an array of silver nanoantennas. The confirmation of this physical phenomenon opens the door to a new class of light-trapping structures for photovoltaics.