A modified poton sieve serves as a memory for different holograms

 |  SFBCeOPP  |  Nachrichten AG Zentgraf

When light hits a pinhole with a hole diameter below the wavelength as a plane wave, spherical waves can form behind the pinhole. If now a whole ensemble of holes with well-considered positioning is chosen, the different spherical waves can interfere with each other in any way. The superposition of the transmitted individual waves then results in a new wave front which can, for example, carry image information. Such a construct is called a photon sieve. A simple structure like a hole pattern cannot distinguish between different colors of incident light in a narrow spectral range. To generate color-selective behavior of photon sieves, we show in our article 'A wavelength selective photon sieve for holographic applications' how specially designed silicon metaatoms can be exploited as color filters. By choosing two different geometries of the metaatoms, up to three holograms can be stored in a photon sieve in our example. A cleverly chosen correlation of the two different geometries also increases the information density. By this kind of multiplexing, different information can be read out by changing the wavelength or the polarization of the incident light. Because the holograms are in the visible spectral range and the readout of the different image information is very fast and easy, this principle is attractive for applications in holographic displays, such as those used in airplanes and cars. The major advantage of metamaterials compared to conventional light modulators is the small pixel size, which dramatically increases the information density, and the small thickness of the information carrier of only 300 nanometers.

This work is funded by the German Research Foundation (DFG) as part of the Collaborative Research Center TRR142 "Tailored Nonlinear Photonics".

Read the paper: doi.org/10.1515/nanoph-2021-0440

PhD student Daniel Frese during his work in the optics lab. (Photo: UPB, Thomas Zentgraf)