A special beam splitting scheme based on distributed beam splitting with diffractive elements is presented. Multiple beams are created, whose phase relations can be controlled with almost arbitrary precision by only changing the distance between the applied diffractive elements. Integration of this scheme into a reflective imaging system ensures temporal and spatial overlap of all selected beams in the target plane, and enables the use of femtosecond radiation. Manifold photonic structures can be fabricated in this way by phase-controlled multiple-beam interference. We demonstrate the capability of the method for femtosecond laser treatment of solids. Using subpicosecond laser pulses at 248 nm, submicron sized periodic structures with different shapes and feature sizes in the range of 100 nm are ablated on the surface of polycarbonate samples.
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