The optical Fano resonance in asymmetric dimer metamaterial

We study the sharp Fano-type resonance in a dimer metamaterial based on nanorods with different lengths. Breaking the length symmetry results in the excitation of a dark mode that weakly couples to the free space. Interference between the dark mode and the higher frequency bright mode gives rise to the peculiar asymmetric and sharp profile of the resonance. The steep dispersion and high sensitivity to slight variations of the dielectric environment of this resonance envisage the possible application of the asymmetric dimer metamaterial as an optical sensor for chemical or biological analysis.