Femtosecond laser nanostructuring in glass with sub-50nm feature sizes
  We report on controllable production of nanostructures embedded in a porous glass substrate by femtosecond laser direct writing. We show that a hollow nano-void with a lateral size of ~40 nm and an axial size of ~1500 nm can be achieved by manipulating the peak intensity and polarization of the writing laser beam. Our finding enables direct construction of 3D nanofluidics inside glass. 
Yang Liao, Yinglong Shen, Lingling Qiao, Danping Chen, Ya Cheng, Koji   Sugioka, and Katsumi Midorikawa
physics.optics