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Proceedings Paper

Optical trapping of nanoshells
Author(s): Brooke C. Hester; Alice Crawford; Rani B. Kishore; Kristian Helmerson; Naomi J. Halas; Carly Levin
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Paper Abstract

We investigate near-resonant trapping of Rayleigh particles in optical tweezers. Although optical forces due to a near-resonant laser beam have been extensively studied for atoms, the situation for larger particles is that the laser wavelength is far from any absorption resonance. Theory predicts, however, that the trapping force exerted on a Rayleigh particle is enhanced, and may be three to fifty times larger for frequencies near resonance than for frequencies far off resonance. The ability to selectively trap only particles with a given absorption peak may have many practical applications. In order to investigate near-resonant trapping we are using nanoshells, particles with a dielectric core and metallic coating that can exhibit plasmon resonances. The resonances of the nanoshells can be tuned by adjusting the ratio of the radius of the dielectric core, r1, to the overall radius, r2, which includes the thickness of the metallic coating. Our nanoshells, fabricated at Rice University, consist of a silica core with a gold coating. Using back focal plane detection, we measure the trap stiffness of a single focus optical trap (optical tweezers), from a diode laser at 853 nm for nanoshells with several different r1/r2 ratios.

Paper Details

Date Published: 5 September 2007
PDF: 9 pages
Proc. SPIE 6644, Optical Trapping and Optical Micromanipulation IV, 66441B (5 September 2007); doi: 10.1117/12.735276
Show Author Affiliations
Brooke C. Hester, National Institute of Standards and Technology (United States)
Alice Crawford, National Institute of Standards and Technology (United States)
Rani B. Kishore, National Institute of Standards and Technology (United States)
Kristian Helmerson, National Institute of Standards and Technology (United States)
Naomi J. Halas, Rice Univ. (United States)
Carly Levin, Rice Univ. (United States)

Published in SPIE Proceedings Vol. 6644:
Optical Trapping and Optical Micromanipulation IV
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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