Correction of figure errors on optical surfaces by laser-induced contraction of Mo/Si multilayers

We demonstrate that laser annealing of Mo/Si multilayers can be used to make controlled modifications of the surface figure of an optical substrate on a nanometer scale. In this experiment a superpolished optical flat was exposed to single pulses from an excimer laser to produce surface depressions of widths that varied from 10 µm to 0.5 mm and of depths in the range 2–50 nm. Simulations of thermally induced contraction of the Mo/Si multilayers are in good agreement with the observed deformations and indicate that the technique can be extended to larger deformations and higher resolution.