title: Distinguishing between ultrafast optical harmonic generation and multi-photon-induced luminescence from ZnO thin films by frequency-resolved interferometric autocorrelation microscopy.
abstract: The nonlinear optical properties of thin ZnO film are studied using interferometric autocorrelation (IFRAC) microscopy. Ultrafast, below-bandgap excitation with 6-fs laser pulses at 800 nm focused to a spot size of 1 µm results in two emission bands in the blue and blue-green spectral region with distinctly different coherence properties. We show that an analysis of the wavelength-dependence of the interference fringes in the IFRAC signal allows for an unambiguous assignment of these bands as coherent second harmonic emission and incoherent, multiphoton-induced photoluminescence, respectively. More generally our analysis shows that IFRAC allows for a complete characterization of the coherence properties of the nonlinear optical emission from nanostructures in a single-beam experiment. Since this technique combines a very high temporal and spatial resolution we anticipate broad applications in nonlinear nano-optics.
authors.affiliation: Institut für Physik Carl von Ossietzky Universität, 26129 Oldenburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Mascheck
authors.forename: M
authors.initials: M
authors.lastname: Silies
authors.forename: T
authors.initials: T
authors.lastname: Yatsui
authors.forename: K
authors.initials: K
authors.lastname: Kitamura
authors.forename: M
authors.initials: M
authors.lastname: Ohtsu
authors.forename: C
authors.initials: C
authors.lastname: Lienau