We introduce a novel sub-diffraction direct laser writing process and discuss its advantages compared to common lithographic methods. The fundamental idea is based on the combination of a Stimulated Emission Depletion (STED) with the effect of an Excited State Absorption (ESA). Analogous to the STED-microscopy, an excited spatial volume below the diffraction limit is created. The modified optical properties of this volume compared to the non-excited surrounding regions are used for the subsequent spatially restricted processing based on an ESA. In combination with a required STED- and ESA-compatibility, a variety of potentially suitable processes for excitation, stimulated emission, and ESA are presented for various materials. Here, direct semiconductors such as ZnO are of particular interest for a STED-process. The second essential requirement, an ESA-based processing, was demonstrated experimentally for the first time at a 200 nm thinn ZnO-layer sputtered on a fused silica substrate. For this purpose, an experimental setup consisting of two ns-lasers, one for excitation and one for the ESA-based processing, as well as a variable time delay, was used.
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