Abstract
High-capacity storage technologies are needed to meet our ever-growing data demands1,2. However, data centres based on major storage technologies such as semiconductor flash devices and hard disk drives have high energy burdens, high operation costs and short lifespans2,3. Optical data storage (ODS) presents a promising solution for cost-effective long-term archival data storage. Nonetheless, ODS has been limited by its low capacity and the challenge of increasing its areal density4,5. Here, to address these issues, we increase the capacity of ODS to the petabit level by extending the planar recording architecture to three dimensions with hundreds of layers, meanwhile breaking the optical diffraction limit barrier of the recorded spots. We develop an optical recording medium based on a photoresist film doped with aggregation-induced emission dye, which can be optically stimulated by femtosecond laser beams. This film is highly transparent and uniform, and the aggregation-induced emission phenomenon provides the storage mechanism. It can also be inhibited by another deactivating beam, resulting in a recording spot with a super-resolution scale. This technology makes it possible to achieve exabit-level storage by stacking nanoscale disks into arrays, which is essential in big data centres with limited space.
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Data availability
The data that support the findings of this study are available at https://doi.org/10.57760/sciencedb.13342 (ref. 50). Source data are provided with this paper.
Code availability
The MATLAB code used in this study is available at https://doi.org/10.57760/sciencedb.13342 (ref. 50).
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Acknowledgements
J.W. acknowledges the financial support from the National Natural Science Foundation of China (NSFC, project no. 62175153). M.G. acknowledges the support from the Science and Technology Commission of Shanghai Municipality (project no. 21DZ1100500) and the Shanghai Municipal Science and Technology Major Project. M.G., J.W. and H.R. acknowledge the financial support from the Shanghai Municipal Science and Technology Commission Innovation Action Plan (project no. 18DZ1100400). M.G. and H.R. acknowledge the financial support from the National Key R&D Program of China (project no. 2021YFB2802000). Y.-W.Z. acknowledges the support from the National Natural Science Foundation of China (NSFC, project no. 21925112). X.W. acknowledges the support from the National Natural Science Foundation of China (NSFC, project no. 62027824). We thank Z. Gan from Huazhong University of Science and Technology for the adjustment of the optical writing set-up. We thank F. Liu from the Integrated Laser Microscopy System and Computation System at the National Facility for Protein Science in Shanghai (NFPS), Zhangjiang Lab for providing usage and technical support for the STED microscope. We thank H. H. Li and E. K. Zhang from Leica Microsystems (Shanghai) Trading Company Ltd for time-resolved photoluminescence detection and emission spectrum measurement. We thank D. Y. Lei and S. Y. Jin from the City University of Hong Kong for the discussion of the measurement of fluorescence lifetime in microscale. We thank H. X. Xu from Wuhan University, and D. Pan and C. J. Zhang from East China Normal University for helping with the Raman measurement in microscale. We thank T. C. Tang from the University of Shanghai for Science and Technology for data baseline cutting in the Raman measurement. We thank W. X. Cao from the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences for joining the shelf lifetime measurement of the sample.
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Contributions
M.G., H.R. and J.W. conceived the original concept and initiated the work. J.W., M.Z. and Q.H. performed the theoretical analysis and conducted the simulation. M.Z. and J.W. synthesized the material. M.Z., J.W. and H.R. developed the set-up and performed the measurements. J.W., M.Z., H.R., Y.-W.Z. and M.G. analysed the data and explained the mechanism. M.G., J.W., H.R., M.Z. and Y.-W.Z. discussed the results. J.W., M.G., M.Z., X.W. and H.R. wrote the paper and all authors reviewed the paper.
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Extended data figures and tables
Extended Data Fig. 1 Optical setup of dual-beam volumetric nanoscale writing.
L1, L2, L3, and L4, collimation lenses; L5, collection lens; L6, tube lens; PH1 and PH2, pinholes; HWP, half-wave plate; QWP, quarter-wave plate; VPP, vortex-phase plate; DC1 and DC2, dichroic filters; S, electronic shutter; M, mirror; BS, beam-splitter; MMF, multi-mode fibre; and CCD, charged coupled device. Source images of the optical components provided courtesy of Thorlabs, Inc.
Extended Data Fig. 2 Summary of an aggregation-induced emission dye-doped photoresist (AIE-DDPR) film.
a–c, Fluorescence images of the ODS medium doped with tetraphenylethene (a), no AIEgens (b) and hexaphenylsilole (c) obtained by the Leica microscope. d–f, Intensity profiles (d), (e) and (f) are extracted from (a–c). g, Transmission electron microscopy image of a cured AIE-DDPR film. h, Expansion of the blue-boxed area in (g). i, Transmittance of a cured AIE-DDPR film with a thickness of 130 µm (blue line) and a pure silica substrate with a thickness of 980 µm (red line).
Extended Data Fig. 3 Aggregation-induced emission dye-doped photoresist (AIE-DDPR) recording medium in colloidal and solid states and fluorescence images of the volumetric writing with different layer spacings.
a, AIE-DDPR in the colloidal state under white-light illumination (left) and ultraviolet (UV)-light illumination (right). b, Cured spin-coated AIE-DDPR film under white-light illumination (left) and UV-light illumination (right). c, Base disc comprising the substrate. d, Disc spin-coated with a film of AIE-DDPR that has been cured (a blank disc yet to be written with information). e–g, There was strong cross-talk of the signal when the layer spacing was 0.5 μm (e) or 0.7 μm (f), and no cross-talk of the signal when the layer spacing was 1 μm (g).
Extended Data Fig. 4 Binary bits of the encoded image (a) and the recalled image (b) in Fig. 2e.
In a, ‘1’ and ‘0’ represent the writing beam being ‘on’ and ‘off’ which are controlled by the electronic shutter in Extended Data Fig. 1. In b, ‘1’ and ‘0’ represent the fluorescent signal from the recording medium being ‘on’ and ‘off’.
Extended Data Fig. 5 Schematic illustration of the writing principle of volumetric nanoscale ODS and simulations.
a, Jablonski diagram of 2-isopropylthioxanthone photoinitiators for the explanation of polymerization by two-photon absorption and depolymerization by triplet–triplet absorption. The green arrows indicate the absorption of the two photons, the brown arrow indicates the radiative relaxation of the fluorescence, the blue arrow indicates the radiative relaxation of the phosphorescence, the grey dashed arrow indicates intramolecular vibrational redistribution (IVR), the red arrow indicates triplet–triplet absorption, the yellow arrows indicate intersystem crossing (ISC)/IVR (dashed arrow) or reverse ISC/IVR (solid arrow), and the black arrow indicates radical formation. The energy levels are not to scale. The solid horizontal lines indicate nonvibrational electronic states whereas the dashed horizontal lines indicate vibrationally excited electronic states. b, Principle of dual-beam nanoscale optical writing. A 515-nm femtosecond Gaussian laser beam initiates polymerization in a medium via two-photon absorption, and a 639-nm CW doughnut-shaped laser beam then deactivates locally the polymerization at the periphery of the focus, which reduces the polymerization volume to the subdiffractive level. c, Simulated profiles of photo-polymerization conversion rate versus deactivating intensity in a dual-beam writing process. The threshold was set to 42%, with the area above 42% representing the third state in Fig. 3, and the area below 42% representing the second state in Fig. 3. d and e, Simulated superresolution STED images of a 4 × 4 pattern formed by the 515-nm femtosecond writing laser beam without (d) and with (e) subsequent application of the 639-nm deactivating beam. f, Simulated confocal image of the pattern formed by the dual-beam writing configuration. g, Intensity profiles extracted from (d–f).
Extended Data Fig. 6 Properties of the standard sample of Ru(bpy)3Cl2 thin film and the aggregation-induced emission dye-doped photoresist (AIE-DDPR) film for characterization of QYs and fluorescence on–off contrast of the recorded spots.
a–c, (a) Chemical formula. The QY of Ru(bpy)3Cl2 thin film is 7.3% which is calculated from the absorbance (b) and the fluorescence emission intensity (c) at an excitation wavelength λ = 480 nm. d, Fluorescence intensity of the AIE-DDPR film at an excitation wavelength λ = 480 nm before exposure to the femtosecond laser (0 mW, i.e., the second state in Fig. 3) and after exposure to the 515-nm femtosecond laser with various writing powers, i.e., 0.3–1.5 mW (i.e., the third state in Fig. 3), and the standard sample of Ru(bpy)3Cl2 thin film. e, Photobleaching: fluorescence on–off contrast of a recorded spot probed by irradiation with a 480-nm pulsed laser. f–h, Fluorescence image obtained at 7 min (f), 27 min (g), and 134 min (h) after the beginning of excitation.
Extended Data Fig. 7 Comparison of fluorescence images and aggregation sizes of the recorded spots with the 515-nm femtosecond Gaussian laser beam only and dual-beam writing.
a, Fluorescence and optical images of the recorded spots at different writing powers of the 515-nm femtosecond laser beam, as measured in the optical path. b, Scanning electron microscopy (SEM) images and fluorescent images of diffraction-limited spots recorded by the 515-nm femtosecond Gaussian laser beam only and subdiffractive spots recorded by the dual-beam writing configuration. Scale bar: 1 µm. c and d, Superresolution imaging of densely arranged spots of a panda yin–yang pattern. Superresolution STED-image readouts of the recording patterns formed by the 515-nm femtosecond writing laser beam without (c) and with (d) subsequent application of the 639-nm CW deactivating beam. Insets: Magnified images of 1 × 2 recording spots and the original panda yin–yang pattern. e, Intensity profiles extracted from the areas marked with the dashed lines in the magnified images in (c) and (d). The panda yin–yang pattern is discretized to a 21 × 21 dot matrix with a spacing of 112 nm.
Extended Data Fig. 8 ODS on optical base disc and fluorescence lifetime imaging of the recording areas.
a, A base disc comprising only substrate. b, A disc with a transparent-yellow circle of the aggregation-induced emission dye-doped photoresist (AIE-DDPR) that has been subsequently cured. c, Superresolution imaging of recording spots formed by the 515-nm femtosecond writing beam without and with the application of the 639-nm CW deactivating beam. d, Intensity profiles extracted from the areas marked with the white dashed lines in the red and blue boxes in (c). The recording-spot sizes were 107 nm and 188 nm for dual-beam writing and single-beam writing, respectively. We had to scan a portion of the optical disc as the scanning stage could not accommodate a whole disc. e and f, Scanning fast fluorescence lifetime imaging microscopy (FLIM) image (e) and the corresponding FLIM histogram (f) for the recorded areas at different writing powers of the 515-nm femtosecond laser beam (the third state) and the background area with only ultraviolet curing (the second state). The recording areas were written at a scan speed of 2.5 µm/s and comprised parallel lines with a line spacing of 300 nm.
Extended Data Fig. 9 Lifetime and durability test of ODS.
a and b, Scanning fluorescence and white-light microscopic images of the recorded spots for the temperature stress condition of 130 °C and 120 °C. The time is incubation time. c and d, The intensities for different incubation times (c) and (d) were extracted from the fluorescence images (a) and (b).
Supplementary information
Supplementary Video 1
A video of 100-layer recording on the AIE-DDPR film in mp4 format. The institute and university badges (‘SIOM’ and ‘USST’) and binary bits of encoded images of a tree and a flower were alternately written in the recording medium. The layer-to-layer distance is 1 μm.
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Zhao, M., Wen, J., Hu, Q. et al. A 3D nanoscale optical disk memory with petabit capacity. Nature 626, 772–778 (2024). https://doi.org/10.1038/s41586-023-06980-y
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DOI: https://doi.org/10.1038/s41586-023-06980-y
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