Einladung zum Promotionsvortrag von Herrn Felix Köttig:
„Strong-Field Nonlinear Fiber Optics“
Gas-filled hollow-core photonic crystal fibers are an ideal platform for the efficient interaction of ultrashort laser pulses with matter over long distance. In this talk I will present recent results on gas-based nonlinear fiber optics in the strong-field regime where partial photoionization of the gas occurs. In a first fiber stage, pulses from an ytterbium fiber laser were compressed from 300 to sub-25 fs pulse duration with high efficiency. In a second fiber stage, wavelength-tunable ultrashort pulses were generated in the deep UV between 200 and 300 nm with unprecedented performance via the resonant emission of dispersive waves from self-compressed solitons, reaching 8% conversion efficiency from the 1 μm pump laser, 1 μJ pulse energy and 1 W of average power at 1.92 MHz repetition rate. On one hand, long-lived effects that follow recombination of the partially ionized gas inside the fiber core were found to degrade the UV emission at high repetition rate. On the other hand, the strong nonlinearity that comes with photoionization leads to unique soliton-plasma interactions on the femtosecond timescale, for example dispersive wave emission in the mid-IR between 3 and 4 μm. At the highest intensities, asymmetric self-phase modulation due to ionization suppresses the conventional soliton self-compression. This leads to a coherent plasma-induced soliton fission that creates robust pulse pairs with PHz bandwidth that co-propagate phase-locked over long distance. (Vortrag auf Englisch)
Dem Vortrag schließt sich eine Diskussion von 15 Minuten an. Vortrag und Diskussion sind öffentlich. Diesen Verfahrensteilen folgt ein nicht öffentliches Rigorosum von 45 Minuten.