Optical figuring and shape correction using femtosecond lasers

We demonstrate nano-structuring and the reduction of mid-spatial-frequency (MSF) errors using femtosecond laser figuring and finishing. We established a method to create periodic nanostructures using femtosecond-laser-based ablation. In addition, a laser-created sinusoidal pattern with five cycles/mm was generated to mimic the mid-spatial frequency error that often occurs s during conventional optics fabrication. A deterministic material removal having nanometer-scale precision was performed to remove the mid-spatial-frequency error from 17 nm to one nanometer in magnitude. The resulting surface remains single-digit-nanometer surface roughness after the MSF error correction.