Fig. 1. 5D optical storage of nanogratings^[25]. (a) Data recording setup; (b) Arrhenius plot of nanograting decay rate; (c) data readout

Fig. 2. Type X structures with high transmittance^[42]. (a) Transmission spectra and photographs of birefringent structures of Type II (dotted line/left) and Type X (solid line/right); (b) scanning electron microscope (SEM) images of nanostructures under different pulse numbers; retardance and transmission images of birefringence structure under different (c) pulse densities and (d) pulse durations

Fig. 3. 100-layer error-free 5D optical data storage^[43]. (a) Illustration of data encoding and decoding; (b) birefringent images of data voxels on different layers; (c) birefringent images after removing background of Fig.3(b); (d) polar diagrams of measured retardance and azimuth for all voxels in Fig.3(c)

Fig. 4. High-density 5D optical storage based on SNS structure^[44]. (a) Birefringent distribution; (b) slow axis orientation distribution; (c) SEM image; (d) schematic of decoding process

Fig. 5. High-density 5D optical storage based on Type S structure^[45]. (a) Simulated temperature versus time at focus center; (b)-(d) SEM images; (e) pulse energy modulation comparison

Fig. 6. Multi-dimensional optical storage based on tilted nanostructures^[46]. (a) Schematic of formation mechanism of tilted nanostructure; (b) slow-axis orientation images of recorded data

Fig. 7. Optical storage and information encryption based on crystalline nanogratings^[51]

Fig. 8. Ultra-long lifetime 4D optical storage based on single pulse^[55]. (a) Arrhenius plot of decay rate; (b) photoluminescence stability of written dots under different excitation power densities; (c) 16 levels of photoluminescence intensity coding; (d) optical information writing and readout

Fig. 9. Reversible 3D optical storage^[64]. (a) 3D optical information erasing and rewriting; (b) optical information readout

Fig. 10. Ultrafast 3D optical storage based on single pulse^[69]

Fig. 11. Reversible 3D optical storage with entire photostimulation^[70]. (a) Schematic of writing, reading, and erasing of optical information; (b) repeated erasure experiment

Fig. 12. Optical storage and information encryption based on CsPbBr₃ quantum dots^[73]. (a) Optical images (upper) and readout signal intensity mapping images (lower) of CsPbBr₃ QD array during erasing-recovery process under ultraviolet (UV) light; (b) encryption key constructed by laser irradiation

Fig. 13. 3D direct lithography of composition-tunable PNCs in glass^[75]. (a) Schematic of ultrafast laser-induced liquid nanophase separation and PNC formation; (b) PL images and PL spectra of PNCs; (c) PL images of multicolor patterns and multi-layer optical storage application

Fig. 14. 5D optical storage based on LiGa₅O₈∶Mn²⁺ nanocrystals^[59]. (a) Site variation of Mn²⁺ after glass crystallization induces multicolour emission; (b) demonstration experiment for optical storage with 3D space/wavelength/intensity multiplexing

Fig. 15. Parallelization and aberration correction of optical storage. (a) Demonstration of 3D multi-focus parallel recording^[20]; (b) comparative experimental results of aberration correction ^[84,92]

Fig. 16. Data readout from optical storage under deep learning. (a)(b) Super-resolution imaging based on deep learning^[98]; (c) information decoding based on deep learning^[97]