High-capacity optical data storage by ultraviolet femtosecond laser writing in silica glass

Multiplexed optical data storage with the merits of a long lifetime and high data capacity is considered to be a promising technology for storing huge amounts of data generated by human activities. However, practical applications have been limited by the current data capacity, which remains at just a few terabytes (TB) per disc. Here, we demonstrate high-density multidimensional optical data storage in silica glass by writing birefringent voxels using ultraviolet (UV) ultrafast laser pulses. The azimuth of slow axis of birefringent voxels is perpendicular to the polarization direction of the writing laser beam and their retardance can be modulated by pulse numbers or energies. The birefringence modification is attributed to the nanostructures induced by UV laser direct writing in silica glass. Furthermore, a digital document is recorded by this method with a capacity of 7.5 TB/disc and a readout accuracy of 100%.