High-sensitivity nanostructured aluminium ultrathin film sensors with spectral response from ultraviolet to near-infrared

An aluminum ultrathin film with nanohole arrays arranged in a hexagonal lattice is theoretically explored for the sensor application. Two transmission dips, which exhibit high sensitivity to the refractive index (RI) of the cladding layer or substrate, are presented owing to the excitation of surface plasmons at the top and bottom surfaces of the ultrathin metal film. Numerical results show that a sensitivity of 348 nm/RIU, with a figure of merit of 34.8, are obtained, which are tolerated in the existence of aluminum oxidization. By increasing the RI of the substrate, the related transmission dip is obviously red-shifted, which makes the sensors based on the proposed nanostructure work effectively in a broad spectral range from ultraviolet to near-infrared.