Eternal 5D storage in quartz glass

Femtosecond laser writing in transparent materials has attracted considerable interest due to new science and a wide range of applications from laser surgery, 30 integrated optics and optofluidics to optical data storage. A decade ago it has been discovered that under certain irradiation conditions self-organized subwavelength structures with record small features of 20 nm, can be created in the volume of fused quartz, which is renowned for its high chemical stability. On the macroscopic scale the self-assembled nanostructure behaves as a uniaxial optical crystal with negative birefringence. The optical anisotropy, which results from the alignment of nano-platelets, referred to as form birefringence, is of the same order of magnitude as positive birefringence in crystalline quartz. The two independent parameters describing birefringence, the slow axis orientation (4th dimension) and the strength of retardance (5th dimension), are explored for the optical encoding of information in addition to three spatial coordinates. The slow axis orientation and the retardance are independently manipulated by the polarization and intensity of the femtosecond laser beam. The storage allows unprecedented parameters including hundreds of terabytes per disc data capacity and thermal stability up to 1000°. Even at elevated temperatures of 160 °C, the extrapolated decay time of nanogratings is comparable with the age of the Universe - 13.8 billion years. The demonstrated recording of the first digital document, which will survive the human race, is a vital step towards an eternal archive