Fig. 1. (a) PL spectra of initial Eu: CSA glass. (b) PL spectra of Eu: CSA and CSA glasses after irradiation. (c) PL spectra of Eu: BAN glass after ultrafast laser irradiation. The inset is the enlarged PL spectrum excited by 405 nm laser. (d) Absorption spectra of Eu: CSA and Eu: BAN glasses. Inset is an enlargement of absorbance from 350 to 430 nm.

Fig. 2. (a) Optical image of recorded information in the glass. (b) Reading out of information by PL mapping. Scale bar: 10 µm. (c) Relationship between emissive dot size and pulse energy. (d) PL intensity of dots written with diverse pulse durations and pulse energies. (e) PL intensity of dots written with various repetition rates and pulse numbers. (f) 16 levels of grayscale assignment based on the relation between PL intensity and pulse number.

Fig. 3. Optical information writing and readout. (a) Schematic diagram of 3D information writing in the glass. (b) Recorded information in glass in different layers. Dots in layer 1 and layer 2 are written by single pulse with 200 nJ. Dots in layer 3 and layer 4 are written by single pulse with 250 nJ and 300 nJ, respectively. Scale bar: 10 µm. (c) Encode information by binary format. (d) Complicated logo pattern recorded in the glass. Scale bar: 20 µm.

Fig. 4. Stability of recorded information.(a) Thermal stability of PL in Eu: CSA glass. (b) Arrhenius plot of the decay rate. Grey area: error estimates. (c) Comparison of lifetime in ODS based on different media^{6, 8}. (d) Comparison of thermostability of PL in Eu: DSA glasses. (e) PL stability of written dots under various excitation power densities. (f) PL stability of different ODS media.

Fig. 5. (a) PL spectra of dots written in the aluminosilicate glasses by fs laser. (b) PL spectra of initial glasses. Excitation wavelength: 375 nm. (c) Optical emission of Eu²⁺ in CIE coordinates. (d) Schematic diagram of the real 5d energy position in an inorganic solid. (e) Spectroscopic redshift in Eu: DSA glass.