A novel laser based sub-diffraction writing technique by a combination of STED and ESAWednesday (24.06.2020) 14:30 - 14:50 Room 2
We introduce a novel laser based direct sub-diffraction writing (SDW) technique and discuss its advantages compared to common lithographic methods. As shown in Figure 1(a), 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. Here, several different fluorescent material systems such as fluorescence-molecules, -polymers, laser dyes, direct semiconductors, and quantum dots basically fulfill the requirements for a STED-process. Besides the already proven STED-compatibility for some of these material systems [2-4], the second essential requirement, an ESA-based processing, was demonstrated experimentally for the first time within this present study. For this purpose, a thin optically active layer, e.g., a direct semiconductor, was deposited on an optical transparent substrate. The experimental setup consists of two (ultra-) short pulsed lasers, one for excitation and one for the ESA-based processing, as well as a variable time delay. Both laser pulses were spatially superimposed to each other and the processing of the optically active layer solely induced by an ESA based on the single ablation thresholds of each laser pulse was studied in dependence of the pulse delay, laser wavelengths, and pulse fluences. Besides the surface modification, this technique is potentially adaptable for the volume structuring inside the material using a multiphoton approach as shown in Figure 1(b), leading to numerous future applications in the processing of metamaterials, optoelectronics, and photonic crystals .
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