Tuning the optical properties of metamaterials based on gold nanowire arrays embedded in alumina

We fabricated a series of gold nanowires/alumina composite films with different wire lengths. Optical transmission measurements confirmed that the composite films exhibit transverse and longitudinal surface plasmon resonances. We show that the wavelength of the longitudinal resonance is sensitive to nanowire length, while that of the transverse resonance is not. The experimental results are in agreement with the modeled results based on the Maxwell Garnett effective medium theory. Moreover, the window for negative refraction of the samples can be tuned in synchronism with the longitudinal resonance by the nanowire length.

► Freestanding metamaterials based on gold nanowires embedded in alumina with different nanowire length have been fabricated.
► Optical transmission measurements indicate that there are two minima in the transmission spectra due to the excitation of the transverse and longitudinal SPRs.
► The position of the longitudinal resonance can be tuned by nanowire length.
► The wavelength region where the sample behaves like a negative index medium locates around the longitudinal SPR.
► This widnow for negative refraction will be tuned in synchronism with the longitudinal SPR when the nanowire length changes.