Experimental demonstration of sharp Fano resonance within binary gold nanodisk array through lattice coupling effects.

Abstract

Fano resonance originating from the interaction of anti-phased and in-phased lattice collective resonances supported by a binary gold nanodisk array is investigated both numerically and experimentally. As the magnitude of particle radii in the two arrays approaches gradually, the Q factor of such resonance increases while the spectral contrast reduces. In the experiment, a high spectral contrast of 0.7 and a large Q factor of 14 could be achieved at the same time due to the excitation of the pure dipole resonance of each particle resulting from the weak near-field coupling. Optimal calculation gives rise to a higher Q factor of up to 85 and a corresponding spectral contrast of 0.86, which is very promising in refractive sensors. The sensitivity and the figure of merit are 337 nm/RIU and 116, respectively.