Search

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.

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.

Atomic layer deposition ALD can be used to deposit ultra-thin and conformal films on flat substrates, high aspect ratios structures and particles. In this paper, we demonstrate that insulating, multilayered and functionalized ALD coatings can also be deposited conformally on carbon nanotubes. Multilayered coatings consisting of alternating layers of dielectric and conductive materials, such as Al2O3 and W, respectively, are deposited on conductive multi-walled carbon nanotubes. This coated carbon nanotube can function as a nanoscale coaxial cable. Thin layers of Al2O3 ALD are also used as a seed layer to functionalize nanotubes. A carbon nanotube was made highly hydrophobic using an Al2O3 ALD seed layer followed by the attachment of perfluorinated molecules., Published in Applied Physics Letters, v87 p123110-1-123110-3, 2005.

Using Beta/Beta prime dimethypyrrole polymers to reduce the structural disorder it has been possible to interpret the results of electron diffraction data and to propose and idealized structure for neutral polypyrrole. XPS data have been used to define some of the deviations from this ideal structure that are seen in actual films and the origin of some of these defects is related to the mechanism of polymerization. The planarity of the chain structure is shown to be important for high conductivity in pyrrole polymers which appears to involve spinless carriers perhaps associated with bipolarons. (Author)