Synthesis of diamond diffractive optical elements for IR laser beam focusing

The fabrication of diamond-based optical elements for high-power CO2 lasers is of particular interest because of the low optical absorption coefficient of this material in combination with it's very high thermal conductivity and the weak temperature dependence of refractive index1. Recent advances in gas-phase synthesis have made it possible to fabricate polycrystalline CVD diamond films (DF) whose optical and thermal properties are close to those of single crystal diamond material, whereas they are far cheaper. As a result, these sophisticated materials are applied more and more to tasks dominated till now by other materials. Such examples for this are windows for high-power CO2 lasers in the 5 - 20 kW domain1 and beam-splitters2. Recently new techniques have been proposed for antireflective structuring of DF surface3,4 as well as for generation of phase microrelief to manufacture diamond diffractive optical elements (DOEs) for the far IR range5-8. The realisation of DOE by UV-laser ablation has been considered5-8. Using of ion-chemical etching and plasmochemical-etching9 is considered later10. The present paper is devoted to further development of considered approaches5,9. The realization of diamond diffractive optical elements (DOEs) is considered, able to focus an incoming CO2 laser beam into certain pregiven focal domains. Results of experimental investigation of designed DOEs are presented and discussed.