Dichroic thin films of silver nanoparticle chain arrays on facetted alumina templates

We show that controlled growth on ordered facetted alumina substrates can be used as nanoscale templates to produce regular arrays of silver nanoparticle chains. The interactions between the aligned nanoparticles induce strong dichroism in the absorption spectra. The resonance plasmon wavelengths are shifted to 455 and 550 nm for transverse and longitudinal polarization, respectively. Simulations show that the slightly prolate shape of the nanoparticles also contributes to the resonance splitting. Such nanostructured thin films can be used as dichroic devices.