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color="#000000"><b>Seminar on</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Modern Optics and Spectroscopy</b></font></div>
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<div align="center"><font face="Arial" size="+1"
color="#000000"><b>Manipulating nanoparticles and enhancing
spectroscopy with surface plasmons</b></font></div>
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<div align="center"><font face="Times New Roman"
color="#000000"><b>Ken Crozier</b>, Harvard University</font></div>
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<div align="center"><font face="Times New Roman"
color="#000000">Tuesday, November 10, 2009</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">12:00
- 1:00 p.m.</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">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 (SPPs, 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 also review 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.
Lastly, 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 mostly overlooked.
Here, 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 SiO_2 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).</font></div>
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<div align="center"><font face="Times New Roman" color="#000000">Grier
Room, MIT Bldg 34-401</font></div>
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color="#000000">Refreshments served after the lecture</font></div>
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