ab-initio description of optical nonlinearities in femtosecond filaments

• Antragsteller: Dr. Carsten Brée
• Fachliche Zuordnung: Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen
• Förderung: Förderung von 2012 bis 2016
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 229103282

Femtosecond filaments are self-organized strings of light and free electric charges. The electric field strength in these filaments comes close to the atomic field strength.Therefore, laser filamentation, together with high-harmonic generation, is one of the most extreme scenarios in nonlinear optics, with a large number of effects acting simultaneously in the spatial as well as in the temporal domain. While numerical modeling is quite advanced, recently, the commonly accepted picture of filamentation has been challenged by experimental reports that indicate a previously underestimated effect resulting from higher-order electronic nonlinearities which may overrule plasma effects. While this report has given rise to vivid discussions, a rigorous theoretical understanding going all the way back to the quantum mechanical roots, i.e., the Schrödinger Equation is still outstanding. Here we propose a suite of theoretical tests for the role of high-order harmonics in nonlinear optics. These tests start with the simplest case of atomic hydrogen or helium, using non-perturbative techniques. For more complex and experimentally more relevant scenarios, we plan to use time-dependent density functional theory to calculate the induced dipole moment. Such rigorous theoretical investigations appear to be the only way to decide whether we really have a new paradigm in Nonlinear Optics or whether old pictures of plasma effects balancing Kerr effects actually prevail.

• DFG-Verfahren: Sachbeihilfen
• Beteiligte Person: Professor Dr. Günter Steinmeyer