Tunable plasmonic dichroism of Au nanoparticles self-aligned on rippled Al ₂ O ₃ thin films

The self-alignment and optical dichroism of Au nanoparticle chains grown by glancing incidence deposition on rippled Al 2 O 3 thin films is investigated. Although the nucleation of the nanoparticles is almost isotropic, their growth is strongly anisotropic resulting in a sharp dependence of their optical transmittance on the orientation of the polarization of the incident light. We show that both the frequency and the spectral width of the transverse and longitudinal surface plasmon resonances can be easily tuned by varying the amount of deposited metal. Such nanostructured materials open perspectives for the development of plasmonic devices endowed with tunable optical dichroism both in the visible and the near infrared regimes.