Strukturierung von Zinkoxid Dünnschichten mittels Zweistrahlanordnung unter Ausnutzung einer Excited State Absorption The present work demonstrates the ns laser pulse assisted excited state absoption (ESA) based processing of Zinc(II) oxide thin films with a layer thickness of 50 – 300 nm on crystallographically differently oriented quartz as well as crystalline sapphire and amophous fused silica substrates using a dual laser beam setup. The goal was to achieve an ablation efficiency improvement compared to single beam ablation by decreasing the required pulse fluences. For the ESA based ablation the optical excitation with radiation of a laser with photon energies Ep above the optical band gap energy EBL was used to excite electrons into the conduction band (LB) which then partially relax into defect levels. This allows the transient single photon absorption of radiation of a second spatially and temporally aligned laser pulse with Ep < EBL exciting electrons to the LB from these defect levels. By utilizing different ESA wavelengths in the visible spectrum with λESA = 410 – 600 nm λESA = 450 nm was determined as the most effective wavelength for the ESA based ablation due to the increased Ep allowing the absorption from an increased number of suitable defect levels. To quantify the efficiency improvements a model was developed to allow for a comparison with single beam ablation by determining the pulse fluence dependent size of the ablated structures. For a more detailed analysis of the ESA based dual beam process and to determine optimal processing parameters a second model was developed to describe the temporal process and the impact of the temperature increase by the pump pulse. In addition to ablation of variable ablation depths the ablation quality was improved by decreasing resolidified molten structures and an ablation was achieved even with a temporal pulse delay in the μs range.