Generation of harmonic radiation in self guided filaments in gaseous media Strong field regime self guiding filamentation third order harmonic generation (THG) high order harmonic generation (HHG) transient grating frequency resolved optical gating (TG FROG) coherent diffraction imaging (CDI). Starkfeld Regime Selbstführung Erzeugung dritter Harmonischer Erzeugung hoher Harmonischer Diffraktionsmikroskopie