Detailed Characterization of Fano Resonance in Asymmetric-double-bar Metamaterials in the Optical Region

Abstract

We investigated characteristics of Fano resonance in asymmetric-double-bar (ADB) metamaterials in the optical region. An ADB structure consisted of a gold nanowire pair with slightly different bar lengths. ADB metamaterials with different sizes were fabricated by a lift-off method, and optical spectra were measured. For three kinds of fabricated ADB metamaterials with different dimensions, experimental spectra clearly showed Fano resonance at around wavelengths of 1500, 1100, and 750 nm, respectively. Characteristics of Fano resonance were estimated from optical spectra, and dependence of the degree of asymmetry was studied. The quality of Fano resonance increased with decreased in asymmetry due to a small radiative loss. In the visible region, quality of resonance was relatively small compared with that in the near-infrared region. Peak values and contrast depended on structural size of the metamaterials. The results will be useful for designing optical metamaterials with high-quality resonance.