Precision shaping of a diamond surface by using interferometrically controlled laser-ablation method

A novel method for figuring and polishing diamond surfaces is described. It is a three step process, consisting of 1) a diffusion smoothing step using carbon reaction with certain materials at elevated temperatures (such as hot iron, molten rare earth metals, etc.), 2) a laser polishing and figuring step where UV laser ablation actively coupled within situ interferometry provides the desired diamond figure and 3) an ion beam assisted superpolishing step, where ion beam technology is used to provide the final surface finish. The first step of the process uses carbon diffusion into a hot iron surface to achieve an initial, relatively smooth surface of the as grown chemical vapor deposited (CVD) diamond surface. The technique dan be used on any size CVD diamond and may be applied to curved surfaces. The second step, excimer laser ablation, is the backbone of the proposed method. By using an in-situ, interferometric surface measuring and monitoring capability, diamond material may be removed from the surface in an accurately controlled manner, both in depth and width. The method is conceptually similar to single point diamond turning for figuring the optical surfaces of metal mirrors. The last step uses the properties of ion beam technology to change the top layer of the diamond surface into a soft and easily polishable amorphous carbon. The final surface finish of the accurately figured surface is obtained by conventional, high quality polishing techniques.