Free-form optics at any scale offer great advantages over conventional optics in term imaging quality, system complexity and weight as a single monolithically component can replace a sub-assembly made of traditional spherical and aspherical components. Regardless of their characteristic dimension, free-form are delicate to manufacture and often requires longer machining steps and more iteration thereof compared to conventional rotational-symmetric components.
A novel approach consists of producing preforms by femtosecond laser-assisted wet etching and subsequently induce a reflow by heating locally with a CO2 laser. The intensity and the net direction of the force depends on the viscosity gradient, which itself depends on the local temperature gradient. Here we will present our analysis and preliminary experimental data related to the surface tension force field induced by local laser heating and its application to toward to goal of making free-form optics from discretised preform structure machined with femtosecond laser.