Browsing by Subject "Plasmon"
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Item Loss compensation in a plasmonic nanoparticle array(2013-05) Miller, Shannon Marie; Alú, AndreaThe problem of heavy material and radiative losses in plasmonic devices has held back their implementation for compact and high-speed data storage and interconnects. One of the most interesting solutions to this problem currently under exploration is the addition of a gain material in close proximity to the metallic nanostructures for loss compensation. Here the physics of light transport in a nanoparticle array, and the operation of gain media in contact with the structure, are described and analytically modeled. A two-dimensional array of closely spaced gold nanoparticles has been fabricated by focused ion beam milling, and its electromagnetic response in the presence or absence of a dye coating has been simulated in preparation for pump-probe optical testing. The compensation of losses via a fluorophore coating has been proven for the first time in this geometry, for a physically realized sample.Item Novel tools for ultrafast spectroscopy(2011-12) Jarvis, Thomas William; Li, Elaine; Fink, Manfred; Keto, John; Lim, Sang-Hyun; Shih, Chih-Kang; Sitz, GregExciton dynamics in semiconductor nanostructures are dominated by the effects of many-body physics. The application of coherent spectroscopic tools, such as two-dimensional Fourier transform spectroscopy (2dFTS), to the study of these systems can reveal signatures of these effects, and in combination with sophisticated theoretical modeling, can lead to more complete understanding of the behaviour of these systems. 2dFTS has previously been applied to the study of GaAs quantum well samples. In this thesis, we outline a precis of the technique before describing our own experiments using 2dFTS in a partially collinear geometry. This geometry has previously been used to study chemical systems, but we believe these experiments to be the first such performed on semiconductor samples. We extend this technique to a reflection mode 2dFTS experiment, which we believe to be the first such measurement. In order to extend the techniques of coherent spectroscopy to structured systems, we construct an experimental apparatus that permits us to control the beam geometry used to perform four-wave mixing reflection measurements. To isolate extremely weak signals from intense background fields, we extend a conventional lock-in detection scheme to one that treats the optical fields exciting the sample on an unequal footing. To the best of our knowledge, these measurements represent a novel spectroscopic tool that has not previously been described.Item Simulation of a plasmonic nanowire waveguide(2009-05) Malcolm, Nathan Patrick; Howell, John R.; Shi, LiIn this work a Finite Difference Time Domain (FDTD) simulation is employed to explore local field enhancement, plasmonic coupling, and charge distribution patterns. This 3D simulation calculates the magnetic and electric field components in a large matrix of Yee cells using Maxwell’s equations. An absorbing boundary condition is included to eliminate reflection back into the simulation chamber, and a sample system of cells is checked for convergence. In the specific simulations considered here, a laser pulse of single wavelength is incident on a silicon substrate, travels through an embedded ZnO nanowire (NW) waveguide only (due to an Ag filter), then incites plasmonic coupling at the gap between an Au nanoparticle tip and an Au substrate, an Au nanoparticle (NP), or a trio of Au nanoparticles incident on an angled Si substrate. The angle between the axis of the NW and the normal of the substrate is varied from 0-60°. The NP perpendicular deflection with respect to the NW axis is also varied from -115 - 75 nm. The enhancement patterns reveal superior signal to noise ratio compared to Near Field Scanning Optical Microscopy (NSOM), three times smaller than the NP diameter 100 nm, as well as resolution and spot size of less than 50 nm. This method of Apertureless NSOM (ANSOM) using a NW waveguide grown on a transparent microcantilever therefore shows promise for imaging of single molecules incident on a substrate and NP-labeled cell membrane.