[MOS] November 10, 2009

[Zina Queen]

Seminar on

Modern Optics and Spectroscopy

Manipulating nanoparticles and enhancing spectroscopy with surface plasmons

Ken Crozier, Harvard University

Tuesday, November 10, 2009


12:00 - 1:00 p.m.




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).


Grier Room, MIT Bldg 34-401
Refreshments served after the lecture
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