Alex Widhalm

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The existence of localized vibrational modes both at the positive and at the negative LiNbO<sub>3</sub> (0001) surface is demonstrated by means of first-principles calculations and Raman spectroscopy measurements. First, the phonon modes of the crystal bulk and of the (0001) surface are calculated within the density functional theory. In a second step, the(More)
In this work we study the impact of ion implantation on the nonlinear optical properties in MgO:LiNbO3 via confocal second-harmonic microscopy. In detail, we spatially characterize the nonlinear susceptibility in carbon-ion implanted lithium niobate planar waveguides for different implantation energies and fluences, as well as the effect of annealing. In a(More)
Silicon oxynitride (SiON) layers for telecommunication device application are grown by Plasma Enhanced Chemical Vapor Deposition (PECVD) for various gas compositions of SiH<inf>4</inf>, N<inf>2</inf>O and NH<inf>3</inf>. Processing and annealing effects on the oxynitride films were studied by Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force(More)
The structural and vibrational properties of lithium niobate (LN) - lithium tantalate (LT) mixed crystals (LNT, LiNb<sub>1-x</sub>Ta<sub>x</sub>O<sub>3</sub>) are investigated over the whole composition range by first-principles simulations. The crystal volume grows roughly linearly from LT to LN, whereby the lattice parameters a and c show minor deviations(More)
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