Excimer laser micromachining for fabrication of diamond diffractive optical elements

Results of the development of multilevel diamond diffractive optical elements (DOEs) for high power CO 2 lasers are reported. For this purpose, the technique of selected-area laser ablation was applied to create a given phase microrelief on mechanically polished CVD polycrystalline diamond plates. High precision micromachining of the diamond plates was performed using a KrF excimer-laser-based system. The spherical (focal distances f=50 mm, f=100 mm) and cylindrical (f=25 mm) Fresnel lenses with an aperture up to 6x6 mm 2 were produced and tested with a cw CO 2 laser (λ=10.6 μm). The diffraction efficiency of the developed DOE measured in the case of the cylindrical lens was found to be only 1-2% lower than the theoretical value. Also a diffractive shaper (with the aperture 6x6 mm 2 and the focal distance 100 mm) transforming a Gaussian beam of a CO 2 laser into a uniformly filled-in rectangle was designed and fabricated.