Regensburg 2022 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 20: Poster
DS 20.15: Poster
Mittwoch, 7. September 2022, 16:00–18:00, P3
Surface second harmonic generation in dielectric nanofilms — •Fatemeh alsadat Abtahi1, Pallabi Paul1,2, Sebastian Beer1, Adriana Szeghalimi1,2, Stefan Nolte1,2, and Falk Eilenberger1,2,3 — 1Institute of Applied Physics, Friedrich-Schiller-University, Jena, Germany — 2Fraunhofer-Institute for Applied Optics and Precision Engineering IOF, Jena, Germany — 3Max Planck School of Photonics, Jena, Germany
Second-harmonic generation (SHG) is a second-order nonlinear optical process that is not allowed in media with inversion symmetry. However, due to the broken symmetry at the surface, surface SHG can still occur in such materials. We experimentally investigate the surface SHG in the periodic stacks of ultrathin dielectric layers. Uniform, dense and optically homogeneous multilayer stacks of SiO2/TiO2 were grown by Plasma Enhanced Atomic Layer Deposition (PEALD) on fused silica substrates. With this technique individual layers of a thickness of less than 2 nm can be fabricated, increasing the number of SHG-active surfaces substantially. Because of the material discontinuity, in each surface of this structure, the symmetry is broken and surface SHG will occur. By changing the Angle of Incidence (AOI) and having constructive interference between all fundamental/SHG signals from different surfaces, we are able to enhance the surface SHG. We experimentally show that under large angles of incidence > 20 degrees there is substantial SHG, well beyond the level, which can be expected for simple surfaces.