Investigation of laser ablation on hybrid sol–gel material applied to kinoform etching

Ultraviolet laser machining of a hybrid organic/inorganic material prepared via a sol–gel process has been studied for the fabrication of kinoforms or surface relief diffractive optical elements. The hybrid mixes silicon and titanium oxides and an organic network in order to improve the mechanical properties. Different material compositions have been investigated. Laser ablation of the hybrid material is observed at low laser fluence (measured threshold fluence of 125 mJ/cm2 at 248 nm/6 ns) and shows that the process is well adapted to micro-patterning by laser machining means. The best observed depth resolution is 60± 20 nm and appears to be limited by the ablation setup. Finally, the fabrication of an effective diffractive optical element and its operation at 1.06 μm are described.