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We experimentally demonstrate practical approaches to enhance second-harmonic (SH) generation in individual lithium niobate nanowires (NWs) with a sub-micrometer cross-section and length up to tens of micrometers. We establish that parametric interactions of guided modes propagating along the NW determine the SH output power, which can be therefore controlled by the NW length. We show that the SH power is increased by about 84 times at wavelengths corresponding to modal phase-matching. Importantly, at non-phase-matched wavelengths the SH power can be improved by a factor of up to 9.3 by adjusting the NW length with a focused ion beam. We also characterize SH emission directionality, which can be further tailored for applications in integrated optical circuits and nonlinear microscopy.

Ion beam mixing of Fe/Si bilayers, induced by 100 keV (40)Arions at room temperature was investigated. Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for structural characterization. The main focus of this study was on the influence of the substrate structure on interface mixing. The influence of the substrate structure is due to the two classes of irradiated bilayers, Fe thin films deposited on crystalline or pre-amorphized Si substrates. An about 76% higher efficiency of atomic transport across the pre-amorphized Fe/a-Si interface as compared to that of Fe/c-Si bilayers was observed.

Charge-state equilibration of ions moving in matter occurs within femtoseconds and when penetrating nanometer depths. Ion-beam mixing in bilayers, tens of nm thick, should therefore not depend on the charge state of the projectiles. As the experimental situation for metal/silicon bilayers irradiated with noble-gas ions of different charge-states is ambiguous, we studied interface mixing of Fe/Si(1 0 0) bilayers, induced by 100 keV Ar-40, 180 keV Kr-86 and 250 keV Xe-132 ions, either singly and multiply charged (Ar8+, Kr11+, Xe17+). No significant influence of the ionic charge-state was established for Kr and Xe ions; a slightly higher mixing rate was found for Ar8+ than for Ar1+ irradiation. (c) 2007 Elsevier B.V. All rights reserved.

Ion-beam mixing of Fe/Si bilayers, induced at room temperature by 100 keV Ar-40(+), 180 keV Kr-86(+), and 250 keV Xe-132(+) ions, was investigated. The study focuses on the influence of the preamorphization of the Si(100) substrates by 1.0 keV Ar-ion irradiation. Rutherford backscattering spectroscopy as well as scanning and transmission electron microscopies were applied for structural characterization. The mixing rate across the preamorphized Fe/Si interface was, on average, by 76% higher than that of crystalline Si. (c) 2007 American Institute of Physics.