Formation of nano-voids in transparent dielectrics by femtosecond lasers

Formation of three-dimensional (3D) patterns of 0.2–0.5 μm diameter voids inside a transparent solid has been demonstrated. The nano-voids could be created with a spacing ∼2 μm thus suggesting the possibility of permanent 3D optical memory with density ∼100 Gbit/cm3. Extremely high pressures of ∼10 TPa and temperatures up to 105 K can be produced by a single sub-picosecond laser pulse tightly focused inside transparent dielectrics. Analysis of the size of the void and the shock affected zone as a function of the deposited energy shows that the experimental results can be explicitly understood on the basis of conservation laws and be modeled by plasma hydrodynamics. Therefore, the size of the void can be controlled and predicted by proper focusing conditions and laser parameters.