Diffraction drastically limits the bit density in optical data storage. To increase the storage density, alternative strategies involving supplementary recording dimensions and robust read-out schemes must be explored. Here, we propose to encode multiple bits of information in the geometry of subwavelength dielectric nanostructures. A crucial problem in high-density information storage concepts is the robustness of the information readout with respect to fabrication errors and experimental noise. Using a machine-learning based approach in which the scattering spectra are analyzed by an artificial neural network, we achieve quasi error free read-out of sequences of up to 9 bit, encoded in top-down fabricated silicon nanostructures. We demonstrate that probing few wavelengths instead of the entire spectrum is sufficient for robust information retrieval and that the readout can be further simplified, exploiting the RGB values from microscopy images. Our work paves the way towards high-density optical information storage using planar silicon nanostructures, compatible with mass-production ready CMOS technology.Optical information storage promises perennial longevity, high information densities and low energy consumption compared to magnetic storage media. 1,2The compact disc (CD) and its successors, the DVD and the blue-ray disc, broadly established optical storage in our society. 3,4 Those media are based on storing a single binary digit per diffraction limited area ("zero" or "one"). Several concepts have been proposed to increase the information density in optical storage. Examples are schemes exploiting polarization-sensitive digits, 5 near-field optical recording, 6 the use of fluorescent dyes 7 or three-dimensional approaches like two-photon point-excitation 8 . Yet, all these alternatives suffer from major drawbacks. Either they are hardly superior to commercial planar solutions (polarization-sensitive patterns) or they require very complex storage media (fluorescence) or sophisticated read-out schemes (nearfield recording, two-photon point-excitation). The most promising alternative seemed to be holographic memory, which was proposed in the early 1960ies and makes use of the volume of the storage medium. To date, however, there is still no commercial product available, despite several announcements in the past 20 years. 9,10 In the last decades, photonic nanostructures emerged as powerful instruments to control light at the nanometer scale. 11,12 Localized surface plasmons (LSP) in metal nanoparticles 13 or Mie-type resonances in high-index dielectric structures 14 cover the entire visible spectrum and can be tuned by designing appropriate geometric features. 15,16 Furthermore, the high scattering efficiencies of photonic nanostructures render single-particle spectroscopy relatively easy. In consequence, the idea has been raised to encode information in the rich scattering spectra of plasmonic nanostructures, denser than a single data bit. 17-21 The information density might be even further increased by addre...

Monolayers (MLs) of transition metal dichalcogenides (TMDs) such as WSe2 and MoSe2 can be placed by dry stamping directly on broadband dielectric resonators, which have the ability to enhance the spontaneous emission rate and brightness of solid-state emitters at room temperature. We show strongly enhanced emission and directivity modifications in room-temperature photoluminescence mapping experiments. By varying TMD material (WSe2 vs MoSe2) transferred on silicon nanoresonators with various designs (planarized vs nonplanarized), we experimentally separate the different physical mechanisms that govern the global light emission enhancement. For WSe2 and MoSe2, we address the effects of Mie resonances and strain in the monolayer. For WSe2, an important additional contribution comes from out-of-plane exciton dipoles. This paves the way for more targeted designs of TMD-Si nanoresonator structures for room-temperature applications.

We present the experimental realization of ordered arrays of hyper-doped silicon nanodisks, which exhibit a localized surface plasmon resonance. The plasmon is widely tunable in a spectral window between 2 and 5 μm by adjusting the free carrier concentration between 1020 and 1021 cm–3. We show that strong infrared light absorption can be achieved with all-silicon plasmonic metasurfaces employing nanostructures with dimensions as low as 100 nm in diameter and 23 nm in height. Our numerical simulations show an excellent agreement with the experimental data and provide physical insights on the impact of the nanostructure shape as well as of near-field effects on the optical properties of the metasurface. Our results open highly promising perspectives for integrated all-silicon-based plasmonic devices for instance for chemical or biological sensing or for thermal imaging.