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Proceedings Paper

Self-assembled nanomaterials for nonlinear fiber optics and tunable plasmonics
Author(s): Islam Ashry; Chalongrat Daengngam; Ishac Kandas; James Heflin; Hans Robinson; Yong Xu
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Paper Abstract

As an amorphous material with full inversion symmetry, silica-based microstructures cannot possess significant secondorder nonlinearity. We recently developed a method that can potentially overcome this deficiency by coating a silica fiber taper with layers of radially aligned nonlinear molecules. The coating process can be accomplished through layerby- layer self-assembly, where the alignment of the nonlinear molecules is maintained through electrostatic interaction. As a result, the nonlinear fiber structures are thermodynamically stable and can generate significant second-order nonlinear responses despite their full rotational symmetry. This prediction has been experimentally confirmed through SHG measurements. To further enhance the overall second-order nonlinearity, we have developed an UV-ablation-based approach that can generate second-order nonlinearity that is spatially periodic along the fiber taper. Our preliminary experiments suggest that SHG intensity can be enhanced by such quasi-phase-matching configurations.

We can also use the self-assembly approach to construct tunable plasmonic systems. As a proof-of-concept study, we assembled swellable polymer films over a planar Au substrate through layer-by-layer assembly and covered the swellable polymer with a monolayer of quantum dots. After immersing the swellable plasmonic structure in solution and adjusting its pH value, we used a fluorescence lifetime based approach to demonstrate that the thickness of the swellable polymers can be modified by almost 400%. The fluorescence lifetime measurements also confirmed that the plasmonic resonance can be significantly modified by the swellable polymers.

Paper Details

Date Published: 28 September 2013
PDF: 9 pages
Proc. SPIE 8845, Ultrafast Imaging and Spectroscopy, 88450D (28 September 2013);
Show Author Affiliations
Islam Ashry, Virginia Tech (United States)
Chalongrat Daengngam, Virginia Tech (United States)
Ishac Kandas, Virginia Tech (United States)
James Heflin, Virginia Tech (United States)
Hans Robinson, Virginia Tech (United States)
Yong Xu, Virginia Tech (United States)

Published in SPIE Proceedings Vol. 8845:
Ultrafast Imaging and Spectroscopy
Zhiwen Liu, Editor(s)

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