Manipulating Nanoparticles and Enhancing Spectroscopy with Surface Plasmons

Thursday, February 18, 2010
6:00 PM
Free and open to the public

Field enhancement from surface plasmon structures presents new opportunities for optical manipulation and surface enhanced Raman spectroscopy (SERS). We demonstrate the propulsion of gold nanoparticles using surface plasmon polaritons (NanoLetters 9, 2623 (2009)). SPPs are excited on a thin gold film. The resultant evanescent field draws nanoparticles toward the film, where they are propelled along by the optical scattering force. We describe related work on Fresnel zone plate optical tweezers. We show that these offer comparable performance to conventional optical tweezers (APL 92, 071112 (2008)), but with considerably smaller footprints. We describe our work on metal nanoparticle substrates for SERS. Arrays of metal nanoparticles are often used for SERS, but the interactions between nanoparticles are frequently overlooked. We demonstrate that periodic metal nanoparticle arrays can exhibit spectrally-narrow surface plasmon resonances, with numerical simulations predicting considerably enhanced optical near-fields (APL 93, 181108 (2008)). To conclude, we describe a novel SERS substrate consisting of a metal nanoparticle array separated from a gold film by a thin SiO2 spacer (Opt Lett 34, 244 (2009)). We show that the double plasmon resonances of these structures enable field enhancement at both pump and Stokes frequencies (FiO 2009, paper FWT5)

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Ken Crozier

John Loeb Associate Professor of the Natural Sciences
Harvard University