Control of ultrafast plasmonic structures by a metal-insulator transition

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ABSTRACT ECCS- 0801985R. Haglund, Vanderbilt UniversityObjective: The objective of this project is to show how plasmon dynamics in composite metal-vanadium dioxide (VO2) nanostructures can be modulated by the reversible semiconductor-to-metal transition (SMT) in VO2. Intellectual Merit: The SMT will be initiated by localized adiabatic heating using a scanning-probe tip, and by ultrafast laser excitation using standard prism coupling schemes. Plasmon dynamics will be tracked using femtosecond pump-probe spectroscopy, plasmon microscopy and a novel, dual apertureless scanning-probe tip scheme for detecting plasmon propagation. During the first year, we will measure the ultrafast localized surface-plasmon resonance (LSPR) response and surface plasmon-polariton (SPP) propagation on nanohole arrays comprising bi-layer films (Ag or Au on VO2) and on VO2-covered nanoparticle arrays (Ag or Au). In the sec-ond year, we will fabricate various VO2:metal composite nanostructures such as non-spheroidal nanoparticles, nanospirals and nanoholes surrounded by grooved diffractive structures. We will investigate the effects of local curvature, size and morphology, and of excitation by linearly and circularly polarized light, on LSPR and SPP dynamics. In the third year, we will fabricate SPP waveguides such as nanoparticle chains (Au-VO2-Au ? ellipsoidal chains and Au-Au ? chains capped with VO2) and nanowire or nanochannel geometries. These SPP-guiding structures are expected to exhibit interesting effects due to induced magnetization, polarization and dispersion that will be tracked via their signatures in the visible optical spectrum. These experiments will point the way to modulating SPP propagation in nanostructures that could serve as prototypes for a variety of plasmonic devices. Broader Impact: The technology will be a demonstration of an ultrafast broadband switch in the near-infrared communications spectral bands. The fundamental understanding of plasmon-photon coupling and plasmon dynamics is expected to result in industrial "spin-off" benefits. Ad-ditionally, the project will result in the dissemination of new knowledge through the training of junior scientists in an international, cross-institutional collaborative environment and a web-based graduate seminar course in nanoplasmonics that will be available to the scientific com-munity.