Super-resolution for optical data storage in nanoscale

Rapid growing data in the coming big-data era compels ever increasing demands on the development of data storage technique enabling ultra-high capacity. For its advantages in energy-saving and long-time information preservation [1–3], optical data storage exhibits exceptional applicability in the near-line storage and data archiving, compared with other storage techniques such as hard discs and solid state discs. However, existing optical data storage techniques with the DVD and the blu-ray DVD are suffering from theoretical capacity limit due to the physical barrier, well known as the diffraction limit of light. While the smallest recording bit size on the order of the wavelength, the storage capacity is limited down to tens of Gigabytes per disc. Here we report on our recent progress on the development of optical solutions to enable super-resolution recording and reading by directly breaking the diffraction limit with an optical nanoscopy-based approaches [4, 5]. This approach can produce a focal spot in the nanoscale for both of recording and writing. For the recording, we have demonstrated the bit feature size as small as 33 nm, which leads to an equivalent storage capacity approaching 1PB per disc. For the reading process, optically active quantum dots with engineered energy levels facilitate the luminescence signal retrieved in a super-resolved manner by reversible saturable optical fluorescence transitions (RESOLFT)process, which allows for resolving the bit size far less than the wavelength of the laser beam.