Observation of Fano-like resonance in dual-blade shaped gold nanostructures

The authors report their observation of Fano-like resonance in a metallic nanostructured array consisting of constituent overlapping gold nano-rectangles, which leads to the possibility of generating a dual-band extinction spectrum. The calculated extinction cross-sections of the nanostructure under linearly polarized light excitations, by the boundary element method, are in excellent agreement with the observed results. Electromagnetic model analysis of plasmon modes at the Fano dip in the extinction spectrum reveals that this mode is an anti-bonding mode sustained by the constituent overlapping nano-rectangles, whereas the other plasmon modes are resonant with bonding modes. The excited Fano dip is highly sensitive in both wavelength and amplitude to the background dielectric medium. The tunability of induced Fano resonance associated with an enhanced electric field in the visible region suggests promising applications, particularly in refractive index sensing.