Fundamentals of a New Sub-Diffraction Direct Laser Writing Method by a Combination of Stimulated Emission Depletion and Excited State Absorption

摘要

We present a unique method of hybrid laser processing by structuring 200 nm thin ZnO films sputtered on fused silica substrates. By a combination of two pulsed ns-laser beams with different photon energies – one below and one above the ZnO band gap energy – the controlled independent ablation of the film devoid of any substrate damage is demonstrated. Compared to single beam ablation, we reduce the amount of debris and thermal defects at the surface at comparable laser energy conditions. To quantify the impact of this dual beam set-up on ablation quality and efficiency, several parameters like pulse delay, laser wavelength, and pulse fluence were varied. These results establish the basis for the proposed novel direct sub diffraction writing method of semiconductors by a combination of the presented principle and stimulated emission.