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Calculation and Optical Measurement of Laser Trapping Forces on Non-Spherical Particles

Nieminen, T. A., Rubinsztein-Dunlop, H. and Heckenberg, N. R. (2001-01-01) Calculation and Optical Measurement of Laser Trapping Forces on Non-Spherical Particles. Journal of Quantitative Spectroscopy and Radiative Transfer, 70 : 627-637.

Document type: Journal Article
Collection: School of Physical Sciences Publications  
 
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Author(s) Nieminen, T. A.
Rubinsztein-Dunlop, H.
Heckenberg, N. R.
Title Calculation and Optical Measurement of Laser Trapping Forces on Non-Spherical Particles
Journal name Journal of Quantitative Spectroscopy and Radiative Transfer
Publication date 2001-01-01
Volume number 70
ISSN 0022-4073
Start page 627
End page 637
Total pages 11
Editor(s) P. Varanasi
Place of publication United Kingdom
Publisher Pergamon
Collection year 2001
Language eng
Subject 240400 Optical Physics
C1
780102 Physical sciences
Abstract Optical trapping, where microscopic particles are trapped and manipulated by light is a powerful and widespread technique, with the single-beam gradient trap (also known as optical tweezers) in use for a large number of biological and other applications. The forces and torques acting on a trapped particle result from the transfer of momentum and angular momentum from the trapping beam to the particle. Despite the apparent simplicity of a laser trap, with a single particle in a single beam, exact calculation of the optical forces and torques acting on particles is difficult. Calculations can be performed using approximate methods, but are only applicable within their ranges of validity, such as for particles much larger than, or much smaller than, the trapping wavelength, and for spherical isotropic particles. This leaves unfortunate gaps, since wavelength-scale particles are of great practical interest because they are readily and strongly trapped and are used to probe interesting microscopic and macroscopic phenomena, and non-spherical or anisotropic particles, biological, crystalline, or other, due to their frequent occurance in nature, and the possibility of rotating such objects or controlling or sensing their orientation. The systematic application of electromagnetic scattering theory can provide a general theory of laser trapping, and render results missing from existing theory. We present here calculations of force and torque on a trapped particle obtained from this theory and discuss the possible applications, including the optical measurement of the force and torque.
Keyword(s) light scattering
optical forces
optical tweezers
laser micromanipulation
 
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http://www.arxiv.org/abs/physics/0308110  
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http://www.elsevier.com/locate/jqsrt  
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Created: Thu, 11 Mar 2004, 10:00:00 EST by Timo Nieminen on behalf of School of Mathematics & Physics. Detailed History