Laser-direct-writing of molecule-like Ag _m ^{x +} nanoclusters in transparent tellurite glass for 3D volumetric optical storage

In situ constructing program-designed nanostructures via laser-direct-writing (LDW) has proved to be a reliable strategy for optical storage (OS). Herein, a kind of low-melting Ag⁺-doped TeO₂-ZnO-Na₂O (TZN) tellurite glass has been demonstrated as an ideal LDW OS medium. Microstructural and spectroscopic studies reveal the generation of molecule-like Ag_m^x+ nanoclusters featured with a broad emission band in the orange-red region upon laser irradiation. Probing the laser-glass interaction yields evidences of the spatial distribution of Ag species responsive to laser-induced thermoelastic pressure wave oscillation, as well as the heat-driven migration/aggregation of Ag species along the radial direction of the laser spot. Raman analyses disclose the loose network of TZN-glass convenient for Ag⁺ mobility and the increased network connectivity when Ag_m^x+ nanoclusters are precipitated out. Combined with the XPS result of Ag⁺ → Ag⁰ reduction, the possible formation mechanism of Ag nanoclusters stabilized in glass has been proposed. In a proof-of-concept experiment, 3D volumetric OS in the TZN glass has been demonstrated, showing optical data encoding/decoding in the form of characters and image patterns.