Phase transitions of nonlinear waves in quadratic waveguide arrays

We study two-color parametric nonlinear modes in waveguide arrays with a quadratic nonlinear response. We predict theoretically and observe experimentally a new type of phase transition manifested in an abrupt power-controlled change of the mode structure from unstaggered to staggered, due to the interplay of localization and synchronization in parametrically driven discrete systems.     

Second-harmonic generation spectroscopy on?organic?nanofibers

Optical second-harmonic generation upon nanosecond laser irradiation of nanofibers grown from nonsymmetrically functionalized para-quarter-phenylene molecules on mica surfaces is investigated in the spectral region around electronic resonances. Strong multiphoton excited luminescence appears together with the second-harmonic signal in the spectra. It is demonstrated how the two components can be separated by analyzing emission spectra recorded over a broad range of wavelengths around the second-harmonic energy. Spectra of the absolute values of the second-harmonic signals are obtained for three differently functionalized molecules. Together with supplementary measurements of the structure of the nanofiber films this forms the basis for estimation of the second-harmonic susceptibility of the fiber materials. Values of the nonlinear susceptibilities are obtained, which are comparable to those of well-known inorganic nonlinear optical crystals.     

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Erratum: ‘All-optical switching in the directional coupler caused by nonlinear refraction due to cascaded second-order nonlinearity’

Erratum: All-optical switching in the directional coupler caused by nonlinear refraction due to cascaded second-order nonlinearity     

Nonlinear optical properties of CNHP4 nanofibers: Molecular dipole orientations and two photon absorption cross-sections

Polarized second harmonic measurements are used to determine the in- and out-of plane orientations of molecular dipoles in optical active, elongated, surface bound nanoaggregates. As a specific example, nonlinear optical active nanofibers grown from CNHP4 molecular dipoles on muscovite mica are investigated. The orientation of the dipoles relative to the substrate is found to be 7 ± 5°, whereas that of the dipoles relative to the long nanofiber axes is ± 13 ± 5°. Following 780 nm femtosecond laser excitation, the two photon action potential ησ₂ for CNHP4 is determined to be 4.7 × 10⁻⁵⁴ cm⁴ s/photon. For comparison, ησ₂ for para-hexaphenylene nanofibers is measured to be 12 × 10⁻⁵⁴ cm⁴ s/photon.     

Water adsorption on the hydroxylated H-(1x1) O-ZnO(0001) surface

The adsorption of water multilayers on a well defined single crystal, hydroxyl-terminated ZnO-surface, H(1x1)-O-ZnO(0001) surface has been investigated using infrared (IR) spectroscopy, helium atom scattering (HAS) and X-ray photoelectron spectroscopy (XPS). The results reveal the formation of well ordered mono-, bi- and multilayers of D2O and H2O on this substrate. On the bare hydroxyl-covered H(1x1) surface the OH-stretch vibration could be clearly identified in the IR-spectra. The water adsorption and desorption kinetics on this hydroxylated surface were studied by monitoring the reflectivity of the surface for helium atoms. The analysis of the data yielded activation energies for desorption of H2O from the H(1x1) O-ZnO surface of 55.2 kJ mol-1. The results reveal the formation of ordered mono- and bilayers. Further exposure to water at 113 K results in the formation of amorphous 3-D islands.     

One-dimensional spatial soliton families in optimally engineered quasi-phase-matched lithium niobate waveguides

The advantage for quadratic soliton generation of engineering the quasi-phase-matching period near the input of lithium niobate slab waveguides is demonstrated. This approach allows members of one-dimensional quadratic soliton families with different values of the wave-vector mismatch to be cleanly excited and to be characterized by quantitative intensity-profile measurements of both the fundamental and the second-harmonic soliton components.     

Spatial ultrafast switching and frequency conversion in lithium niobate waveguide arrays

We demonstrate phase-insensitive, ultrafast, all-optical spatial switching and frequency conversion in quadratically nonlinear waveguide arrays in periodically poled lithium niobate. Routing of milliwatt signals with wavelengths in the communication band (1550 nm) is achieved without pulse distortions by parametric interaction with a control beam with 10-W power and wavelengths near 775 nm.     

Ähnlichkeitsanalyse Von Gruppenrelationen

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