Sub-Wavelength Arrays of Metallic Nanoparticles for Polarization-Selective Broad-Band Absorbers

摘要

Sub-wavelength arrays of silver nanoparticles embedded in a dielectric matrix are elaborated by a low-cost bottom-up technique, which combines substrate pre-patterning by defocused ion-erosion (resulting in the generation of one-dimensional nanoripples) with subsequent Volmer-Weber growth by physical vapor deposition at glancing incidence. The arrays are constituted by regular chains (～20 nm period) of small particles (size less than 10 nm) with elongated shape in the direction of the ripples. This shape anisotropy and the resulting interparticle coupling inside the chains (gap between the particles less than 10 nm) are responsible for the plasmonic dichroism of the array leading to polarization-selective broad-band absorption in visible and near infrared. This dichroism can be tuned by adjusting the amount of deposited metal, the elaboration temperature, the nature of the dielectric host and the deposition geometry. The technique is at last employed to elaborate 3D nanostructures.