Rapid generation of birefringent nanostructures by spatially and energy manipulated femtosecond lasers for ultra-high speed 5D optical recording exceeding MB/s.

In the current era of data explosion, developing a data storage method that combines longevity, large capacity, and fast read/writing capabilities has become imperative. A promising approach is the nanogratings-based 5D optical data storage, which is realized by femtosecond lasers processing of silica glass, with its extremely long storage lifetime and high-density storage capabilities. However, a significant limitation of nanogratings is that their formation relies on in-situ irradiation with tens to hundreds of femtosecond laser pulses. This limitation severely hinders the writing speed of storage techniques that rely on nanogratings. Addressing this challenge, our method, rooted in a deep understanding of the nanogratings evolution process, effectively reduces the pulse requirement for inducing a complete birefringent nanostructure to just three. By modulating the energies and focus depths of seeding and writing pulses, this method achieves control over the material environment and near-field enhancement in the focus region. Crucially, it circumvents the ascent process of nanovoids, a process traditionally necessitating more than 80% pulse number during nanogratings formation. This approach significantly boosts the recording speed of 5D optical data storage based on birefringent nanostructure, likely achieving speed exceeding megabytes per second (MB/s). Such a breakthrough facilitates the development of innovative practical applications utilizing nanogratings structures, including multi-dimensional optical data storage, microfluidics, waveguide, and geometric phase components.