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SINAM Nano-Seminar Announced NANOPARTICLE PLASMONS FOR FIELD-ENHANCED MICROSCOPY AND SPECTROSCOPY Dr. Javier Aizpurua - Donostia International Physics Center, San Sebastian, Spain Monday, March 12, 2007 ABSTRACT Collective oscillations of valence electrons in metallic materials, also known as plasmons, determine the optical response of these materials. The energy and strength of these surface oscillations are a function of the shape, size and coupling of the nanoparticles. With the use of the boundary element method (BEM), we solve Maxwell's equations to calculate light scattering and surface modes in nanostructures that are commonly used as hosts and/or samples in different field-enhanced scanning probe microscopies and spectroscopies. The light scattering and near field distribution of particles such as nanorings [1], nanorods [2], nanodisks [3], or nanowires [4] are calculated and interpreted in terms of the plasmon modes supported by the nanosystems. The results are related for each case with different spectroscopic experiments and connected with the capabilities of these structures to host biomolecules and perform the corresponding spectroscopy. Special emphasis is placed on the near-touching limit for pairs of spherical particles to understand recent experiments in the literature [5]. We also study the electromagnetic response of gold particles when they are coupled to a metallic tip in scattering-type near field optical microscopy (s-SNOM) [6]. We obtain different optical and infrared contrast for different particle size and substrate material, and associate these differences in contrast to the properties of the tip-particle-substrate coupling. Last, but not least, we would like to show some evidence of the decay of a nanohole plasmon in a thin film into a surface plasmon polariton [7]. The understanding of the coupling of the modes in such a variety of systems, and the consequences for the local field enhancement are crucial to engineer and design plasmonic devices for detection and effective optical response. [1] J. Aizpurua et al. Phys. Rev. Lett. 90, 057401 (2003). ABOUT Dr. Aizpurua Dr. Javier Aizpurua holds a Ph.D in Physics from Euskal Herriko Unibertsitatea / University of the Basque Country. He has been a Research Fellow at the Foundation Donostia International Physics Center, DIPC, since 2004, and previously held a position as a Guest researcher in the Atomic Physics Division at the National Institute of Standards and Technology NIST , Gaithersburg, MD (USA). His research interests include: * Nanooptics Link to Donostia International Physics Center Link to Dr. Aizpurua's Homepage View the flyer for this event (PDF, 21KB) Seminar presented by the Center for Scalable and Integrated Nanomanufacturing
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