Nonlinear optical interactions in focused beams and nanosized structures

Thin-film materials from μm thickness down to single-atomic-layered 2D play a central role in many novel electronic and optical applications. Coherent, nonlinear (NLO) μ-spectroscopy offers insight into the local thickness, stacking order, symmetry, or vibrational properties. Thin films are usually supported on multi-layered substrates leading (multi-)reflections, interference, phase jumps at interfaces during μ-spectroscopy, which all can make interpretation of experiments particularly challenging. The disentanglement influence parameters be achieved via rigorous theoretical analysis. In this work, we compare two self-developed modeling approaches, semi-analytical fully vectorial model, carried out thin-film geometry for archetypal NLO processes, second-harmonic third-harmonic generation. particular, demonstrate that interference matching do heavily signal strength. Furthermore, work key differences between three four photon such as Gouy-phase shift focal position. Last, show relatively simple despite its limitations, is able accurately describe significantly lower computational cost compared full modeling. This study lays groundwork performing quantitative thin materials, it identifies quantifies impact corresponding sample setup signal, order distinguish them genuine material