Three-dimensional optical data storage in vitreous silica

To achieve high bit densities (>10 GB/cm(3)) in optical memory, we accompli shed a three-dimensional optical data storage system using vitreous silica as the recording material. We succeeded in high-density optical recording b y focusing pulsed laser beams of 532 nm (full width at half maximum [FWHM] 30 ps) and 400 nm (150 fs). A recording density of 72.9 GB/cm(3) was achiev ed, which corresponded to that of 100 compact disks, on a glass plate of (2 x 2) cm(2) and 2.2 mm thickness. We found that the optical damage of silic a occurs within 400 ps after irradiation by a single pulse for 30 ps at 532 nm. Three photoluminescence bands were found in the photomodified silica a t 283 nm, 468 nm and 558 nm. All the three bands showed similar photolumine scence excitation spectra, i.e. a peak related to oxygen vacancy absorption at 250 nm.