Heavily doped Ag+ and single pulse nJ laser writable glasses with ionic [YOx] modified covalent Al (PO3)3 networks towards long-term 3D optical data storage†

Abstract

Direct laser writing (DLW)-induced photoluminescent Ag clusters in glasses have attracted considerable attention in the development of high-density optical data storage technology. However, achieving silver cluster-doped glasses, with combined advantages of large optical data storage capacities, low writing energy consumption, and ultra-long lifetimes, still remains a big challenge. In this work, with direct near-infrared femtosecond laser writing, silver clusters are formed and enable luminescence read out in aluminum metaphosphate glasses. In order to increase the solubility of Ag in the glass and achieve the above mentioned merits, Y₂O₃ is introduced into the glass system to produce [YO_x] polyhedra and form ionic [YO_x] modified covalent Al(PO₃)₃ glass networks. The combination of a rigid phosphate framework and flexible ionic components gives rise to the transformation of [AlO₆] → [AlO₄]⁻, as well as a growing number of nonbridging oxygens (NBOs); then, it results in a more stable glass network. According to the charge compensation strategy, the newly formed negatively charged [AlO₄]⁻ tetrahedron can well stabilize silver as Ag⁺, while silver can also be effectively stabilized by NBO coordination through acting as network modifiers. These eventually improve Ag in the glass to obtain a uniform distribution. Upon the above points, the Y₂O₃ modified aluminum phosphate glass exhibits remarkable fs laser photosensitivity and enables efficient data writing and readout operations only with very low power fs-laser pulses (19 nJ, 0.6 J cm⁻²). This low-energy requirement significantly reduces power consumption during DLW processes, and the ionic-covalent mixed stable network also endows the glass with long-term endurability. Thus, the glass achieves a storage capacity of 23.3 GB cm⁻³ (equivalent to 790.0 GB for a 120 × 3 mm³ Blu-ray DVD) and the laser-written data possess an ultra-long lifetime of up to 5.3 × 10⁵ years at room temperature. Therefore, the glass shows great potential for high density ODS applications.