Laser shaping of diamond for IR diffractive optical elements

Recently a new technique for laser-induced generation of phase relief to manufacture diamond diffractive lenses for the mid IR range has been proposed. In the present paper the realization of more complicated diamond diffractive optical elements (DOEs) is considered, able to transform a CO2 laser beam into arbitrary pre-given focal domains. Two DOEs for completely different tasks of laser beam focusing have been manufactured and finally investigated by means of various optical techniques. Measured intensity distributions in the DOEs focal planes as well as diffraction efficiencies have been compared with related results of computer simulation, and have been found to be in a good mutual concordance. The obtained results indicate that laser ablation technique can be effectively used to manufacture high quality diamond DOEs for laser beam focusing. Special attention is paid to the diamond surface graphitization in the process of laser ablation. Main parameters of excimer laser ablation are investigated and density of laser-induced graphite-like layer is defined. It was demonstrated experimentally that graphitized layer formed at different regimes of irradiation remains almost constant in thickness, but has different crystal structure.