Holography and Security Holograms

The LaNN laboratory is one of the most important nanofabrication centers in Italy and it’s active in several research fields.

New types of security holograms capable of decoding visual information only by means of light with definite spatial distribution of intensity, phase and polarization state have been engineered.

The security holograms developed belong to two typologies:

  1. in the first one, constituted by a multilevel pixelated structure, the light that illuminates the hologram is modeled by particular phase masks (Spiral Phase Plates) in order to generate a unique decoding key allowing the correct reconstruction of the image. Traditional illumination will not succeed in decoding the image.
  2. The second type of security-hologram relies on the properties of Metasurfaces. Many works are devoted to the control of light with 2D metamaterials. They take advantage of resonant scattering by nanostructures instead of phase-accumulation through propagation. By tailoring shape and size of the nanostructures, hence modifying the properties of the material, we are no more limited to the normal response of naturally existing materials to electromagnetic waves: metasurfaces offer new abilities to control optical beams.


Filippo Romanato: filippo.romanato@unipd.it