Rapid prototyping of diffractive optical elements for high-power lasers using laser ablation lithography fabrication and coherence probe microscopy analysis

Abstract

An alternative technique for rapid prototyping of diffractive optical elements (DOEs) for use with mid-infrared high-power lasers is proposed. The solution is based on the photoablation of an intermediate resist layer on various substrates using an excimer laser in a micromachining station, followed by classical etching of the substrate to form the DOE. Being able to achieve rapid prototyping also depends on having available a rapid, precise, nondestructive profilometry technique in order to optimize each stage of the manufacturing process. After comparing several techniques for structural characterization, we found that coherence probe microscopy was the best one suited for the rapid and precise measurement of the squareness, depth, and surface roughness of the transparent resist mask and the substrate features. Several results of the characterization of transparent resist layers and etched substrates are given. The technique of rapid prototyping by the means proposed is illustrated with the fabrication of a DOE for direct marking of an industrial logo using a high-power CO 2 laser.