Photoacoustic detection of circular dichroism in a square array of nano-helices

A novel nano-structured material has been assembled by means of a focused ion beam technique. This artificial material is composed of a square array of nano-helices built upon a multilayered substrate. Optical measurements of circular dichroism of a sample are confirmed by photo-acoustic investigations, which allow to directly study the helix-field interaction apart from the dielectric substrate. The study is consistent with 3D numerical simulations, and demonstrates to be an efficient tool of investigation for the entire class of these novel structured materials.